US20130336721A1 - Fluid storage in compressed-gas energy storage and recovery systems - Google Patents

Abstract

In various embodiments, lined underground reservoirs and/or insulated pipeline vessels are utilized for storage of compressed fluid in conjunction with energy storage and recovery systems.

Description

RELATED APPLICATIONS
• This application claims the benefit of and priority to U.S. Provisional Patent Application No. 61/659,164, filed Jun. 13, 2012, and U.S. Provisional Patent Application No. 61/695,393, filed Aug. 31, 2012. The entire disclosure of each of these applications is hereby incorporated herein by reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
• This invention was made with government support under DE-0E0000231 awarded by the DOE. The government has certain rights in the invention.
FIELD OF THE INVENTION
• In various embodiments, the present invention relates to gas storage, gas distribution, pneumatics, power generation, and energy storage, and more particularly, to fluid systems for energy storage and recovery.
BACKGROUND
• It is often desirable to store energy in the form of a fluid, such as compressed air or a fluid fuel (e.g., methane), that may be at non-ambient temperature and under high pressure (e.g., 3,000 psi). The energy may be stored at times of low demand or over supply, and the stored energy may be utilized at times of high demand or low supply in various ways: for example, methane may be used to generate industrial process heat, compressed air may be used to power mechanical devices directly, and methane or compressed air may be used by power generators that produce electricity. Retrievable or reversible modes of energy storage include chemical potential energy (i.e., fuel), elastic potential energy (i.e., the energy inherent in a compressed gas or liquid or in a compressed or stretched elastic solid), gravitational potential energy (i.e., the energy inherent in any mass by virtue of its altitude), latent energy (i.e., the energy inherent in a body by virtue of its phase state), electric energy (e.g., the energy inherent in separated electrical charges, as in a charged battery or capacitor), and exergy (i.e., the extractable work latent in a body that is at a temperature higher or lower than the temperature of a heat reservoir such as the body's environment). In systems that employ an energy-storing fluid, the cost of insulated and/or pressure-resistant vessels to contain the fluid is often a large part of the net cost, over the lifetime of the system, of storing and retrieving an average unit of energy.
• Storing energy in the form of compressed gas has a long history and components tend to be well tested and reliable, and have long lifetimes. The general principle of compressed-gas or compressed-air energy storage (CAES) is that generated energy (e.g., electric energy) is used to compress gas (e.g., air), thus converting the original energy to pressure potential energy; this potential energy is later recovered in a useful form (e.g., converted back to electricity) via gas expansion coupled to an appropriate mechanism. Advantages of compressed-gas energy storage include low specific-energy costs, long lifetime, low maintenance, reasonable energy density, and good reliability.
• If a body of gas is at the same temperature as its environment, and expansion occurs slowly relative to the rate of heat exchange between the gas and its environment, then the gas will remain at approximately constant temperature as it expands. This process is termed “isothermal” expansion. Isothermal expansion of a quantity of high-pressure gas stored at a given temperature recovers approximately three times more work than would “adiabatic expansion,” that is, expansion where no heat is exchanged between the gas and its environment—e.g., because the expansion happens rapidly or in an insulated chamber. Gas may also be compressed isothermally or adiabatically.
• An ideally isothermal energy-storage cycle of compression, storage, and expansion would have 100% thermodynamic efficiency. An ideally adiabatic energy-storage cycle would also have 100% thermodynamic efficiency, but there are many practical disadvantages to the adiabatic approach. These include the production of higher temperature and pressure extremes within the system, heat loss during the storage period, and inability to exploit environmental (e.g., cogenerative) heat sources and sinks during expansion and compression, respectively. In an isothermal system, the cost of adding a heat-exchange system is traded against resolving the difficulties of the adiabatic approach. In either case, mechanical energy from expanding gas is typically converted to electrical energy before use.
• An efficient and novel design for storing energy in the form of compressed gas utilizing near isothermal gas compression and expansion has been shown and described in U.S. Pat. No. 7,832,207, filed Apr. 9, 2009 (the '207 patent) and U.S. Pat. No. 7,874,155, filed Feb. 25, 2010 (the '155 patent), the disclosures of which are hereby incorporated herein by reference in their entireties. The '207 and '155 patents disclose systems and techniques for expanding gas isothermally in staged cylinders and intensifiers over a large pressure range in order to generate electrical energy when required. Mechanical energy from the expanding gas may be used to drive a hydraulic pump/motor subsystem that produces electricity. Systems and techniques for hydraulic-pneumatic pressure intensification that may be employed in systems and methods such as those disclosed in the '207 and '155 patents are shown and described in U.S. Pat. No. 8,037,678, filed Sep. 10, 2010 (the '678 patent), the disclosure of which is hereby incorporated herein by reference in its entirety.
• In the systems disclosed in the '207 and '155 patents, reciprocal mechanical motion is produced during recovery of energy from storage by expansion of gas in the cylinders. This reciprocal motion may be converted to electricity by a variety of techniques, for example as disclosed in the '678 patent as well as in U.S. Pat. No. 8,117,842, filed Feb. 14, 2011 (the '842 patent), the disclosure of which is hereby incorporated herein by reference in its entirety. The ability of such systems to either store energy (i.e., use energy to compress gas into a storage reservoir) or produce energy (i.e., expand gas from a storage reservoir to release energy) will be apparent to any person reasonably familiar with the principles of electrical and pneumatic machines.
• The net monetary cost at which energy-storage systems deliver from storage a unit of energy (e.g., a kilowatt hour [kWh] of electrical energy, a BTU of natural gas) depends in part on the cost at which the system stores each unit of compressed gas. The net cost of energy storage by a system employing compressed gas is also influenced by the cost of conditioning the stored, compressed gas by heating, cooling, and/or the addition and removal of other gases or fluids. There is therefore a need for facilities that can store and in some cases thermally condition large quantities of compressed gas at relatively low cost, including the costs of construction and maintenance.
SUMMARY
• In various embodiments, the invention includes the employment of one or more pressure vessels and/or one or more insulated pipeline vessels (IPVs) and/or one or more lined underground reservoirs (LURs) as pressurized-fluid storage containers for a system that stores energy in the form of a compressed fluid (e.g., high pressure gas). The terms “IPV” and “LUR” will be clarified shortly, below. In general, the quantity of energy to be stored may be characterized as “low,” “medium,” or “large.” The cost-effectiveness of a storage container type is, in general, affected by the quantity of energy (i.e., fluid) to be stored. For storage of low energy quantities, pressure vessels (e.g., commercially-produced cylindrical tanks) and/or IPVs will in general be most cost-effective for fluid storage; for storage of medium energy quantities, IPVs and/or LURs will in general be most cost-effective for fluid storage; and for storage of large energy quantities, LURs and/or large scale geological storage (e.g., salt cavern, aquifer) will be in general be most cost-effective for fluid storage.
• Herein, the terms “thermal energy” and “exergy” are employed interchangeably, usually to signify extractable work latent in a body that is at a temperature higher than that of the body's environment. Hybrid systems that store energy in one or more fluids that contain energy in one or more retrievable or reversible forms can also be envisaged and are contemplated herein even when not explicitly mentioned or described.
• The term “insulated pipeline vessel” or “IPV” refers herein to a segment of pressure-resistant pipeline (e.g., pipeline designed to transport natural gas), of whatever length, that has been sealed at its ends (other than to the extent that perforations are provided for the delivery of fluids into and removal of fluids from the IPV) and covered by one or more layers of insulation and possibly by other protective materials as well. Herein, “IPV” may also refer to a series of pipe segments joined together and sealed, or an array of such segments or series of joined segments. An array of pipe segments employed as an IPV is herein referred to as an “IPV array.” An IPV also may be equipped with perforations, valves, and other devices to control the admission and release of gas and/or liquid; may be equipped with sensors for detecting and reporting flow, volume, temperature, pressure, strain, or other qualities of the vessel's contents or of the vessel's own fabric; may contain devices for the exchange of heat between the vessel's fluid contents and external sources or sinks of thermal energy; and may be encased in or buried under a layer or layers of earth, gravel, or other materials. The term “insulated pipeline vessel” or “IPV” may also refer herein to two or more IPVs, as just described, interconnected so as to form a single system for the storage of fluid. IPVs may have lengths well in excess (e.g., >100×) of their diameters, and may not fall within ASME regulations for pressure vessels. IPVs may include or consist essentially of (i) a thermally insulating material (e.g., one or more plastics or polymers) or (ii) a base material that is more conductive (e.g., one or more metals or metal alloys such as steel) that is (a) at least partially buried within an insulating material (e.g., earth, soil, gravel, etc.), (b) has a thermally insulating material impregnated therewithin, and/or (c) has a thermally insulating material disposed on its inner and/or outer surface. In various embodiments, the thermal heat conduction through the walls of the IPV is no greater than 5 Watts per degree Celsius per cubic meter of storage volume (e.g., no more than 250 Watts lost due to heat conduction for fluid contained in an IPV, where the fluid is 50° C. warmer than the surroundings, for every 1.3 meter length of a 1 meter inner diameter pipe), and in preferred embodiments the thermal conductance is no greater than 2 Watts per degree Celsius per cubic meter of storage volume, or even no greater than 1 Watt per degree Celsius per cubic meter of storage volume. For reference, an uninsulated pipe may lose more than 1000 watts (W) per degree Celsius per cubic meter of storage volume (e.g., more than 50,000 W lost due to heat conduction for fluid contained in the pipe, where the fluid is 50° C. warmer than the surroundings, for every 1.3 meter length of a 1 meter inner diameter pipe).
• An LUR is a cavity in rock (primarily crystalline bedrock) that is lined with steel, concrete, and/or other materials that enable the cavity to serve as a vessel containing fluids (e.g., natural gas, air, an air-water mixture) at high pressure (e.g., 150 atmospheres, 250 atmospheres, or higher) without significant fluid leakage either into or out of the cavity. Various embodiments of the invention employ techniques for the excavation of open, vertical shafts in the construction of LURs and for the thermal conditioning of fluids stored in LURs that have been constructed by open-shaft and other techniques.
• Typically, construction of an LUR entails excavation of a large, vertically cylindrical cavity (e.g., 20-50 meters in diameter and 50-115 meters tall) with a domed roof and rounded invert (floor). Excavation may be via sloping access tunnels or the sinking of a vertical shaft. The domed roof may be constructed after excavation of the cavity. A vertically oriented shape enhances the stability of the excavation by minimizing roof area, while rounding of the roof and the invert increases roof strength and enables fluid-pressure stresses on the inner liner (e.g., steel skin) to be distributed more evenly.
• An LUR cavity may be located at various depths below the ground (e.g., 100 meters to 200 meters), depending on rock type and other constraints, and may be lined with a multi-layer lining that may be constructed, wholly or partly, either during excavation or after excavation. The lining typically includes a layer of reinforced concrete (e.g., approximately 1 meter thick) and a thin (e.g., 12-15 mm) inner liner of carbon steel. The lining may also include other layers, such as a layer of thermal insulation (e.g., perlite concrete) and/or a network of pipes to drain groundwater away from the cavity liner. One purpose of the inner liner is to act as an impermeable barrier, both to retain the fluid contents of the cavity and to keep fluids (e.g., groundwater) from entering the cavity. A purpose of the concrete layer is to act as a distributor of forces exerted by the contents of the LUR on the surrounding lining layers and rock mass, and by the surrounding rock mass on the LUR lining layers: that is, the concrete layer assures the most even possible transfer of forces from fluid within the LUR to the surrounding rock mass and distributes any local strains in the rock mass (e.g., from the opening of natural rock fractures) at the concrete/rock interface) as evenly as possible across the concrete and thus across the inner liner. Smooth distribution of forces across the inner liner is desirable because the inner liner is typically thin (to conserve materials and so reduce cost): its composition and thickness, and hence its cost, will depend on the maximum local circumferential strain that any part of it must be able to resist during operation. Therefore, preventing the occurrence of excessive local strain on any part of the inner liner is advantageous.
• To further minimize local circumferential strains on the inner liner, a viscous layer (e.g., approximately 5 mm thick and made of a bituminous (tarry) material) may be placed between the steel and the concrete layers of the liner. This viscous layer will allow some slippage between the inner liner and the concrete, contributing to the reduction of local strains.
• These and other features and advantages of LUR linings in various embodiments of the invention will be further disclosed and clarified in the drawings and accompanying explanations. The foregoing description of liner construction techniques and materials is exemplary: other techniques for construction, and other materials for the inner liner and various other portions of the cavity liner, may be employed.
• Conventional storage facilities for compressed gas rely primarily on (a) compressed-gas bottles, or (b) depleted oil fields, salt caverns, or aquifer formations, into which compressed gas may be injected. The use of oil fields, salt caverns, and aquifers tightly constrains site selection, which is disadvantageous. The various surface-vessel options tend to occupy relatively large areas of land, which can be site-constraining, and are materials-intensive, which raises cost. For a commercially realistic energy-storage capacity, the areal footprint of a compressed gas energy storage and generation facility located at or near the surface of the earth will typically consist mostly of storage.
• A number of advantages are realized by using LURs with energy storage systems relying on compressed gas. An LUR facility, both during and after construction, tends to disturb its surface environs relatively little compared to surface-sited storage facilities of comparable capacity, which, as noted above, can occupy significant area. The ability to site an LUR wherever suitable earth material (e.g., bedrock) allows for the construction of energy storage and generation facilities nearer to demand in some cases, reducing transmission costs. Herein, any earth material suitable for the construction of an LUR is referred to as “bedrock.” Being embedded deeply in bedrock, LURs are relatively secure from accidental or malicious damage, making compressed-gas LURs a particularly safe way to store large amounts of energy; indeed, compressed-air LUR storage is probably one of the safest ways to store large amounts of energy yet devised, since LUR air storage is not accompanied by the possibility of detonation, deflagration, explosive decompression, dam bursting, release of toxins, release of suffocating gases, and other hazards associated with various other energy-storage technologies. The environmental impact of a compressed-air LUR is low both because its surface footprint is low and its water usage is low compared to pumped-reservoir storage, the latter being especially of advantage in arid or semiarid regions.
• Another advantage of compressed-gas LUR storage is that an LUR may enable the storage of compressed gas fluids at lower per-unit cost than most other methods of storage. Lower cost is achieved because in an LUR, outward-acting pressure forces are borne by surrounding bedrock rather than by the constructed fabric of the vessel itself. This greatly reduces the quantities of relatively expensive materials (e.g., steel, carbon fiber, reinforced concrete) needed to contain each unit of pressurized fluid as compared to free-standing high-pressure vessels that must bear all loads internally. Further, because an LUR may be relatively large (e.g., approximately 30,000 m³), its surface-to-volume ratio is low compared to that of a multiplicity of smaller vessels, further reducing material and construction costs per unit of fluid stored.
• Another potential advantage is that an LUR may, when the temperature of its contents is lower than that of the surrounding rock, harvest energy from the earth's innate heat. Heat that flows from surrounding rock to fluids in an LUR may be partially converted to electricity by the energy-conversion portion of an energy storage and generation system.
• Provisions may be made for the exchange of heat between a heat-transfer fluid (e.g., water with additives) and the air (or other gas) within an LUR: for example, water may be sprayed or foamed into the LUR to either warm or cool the air within, and may then be pumped out to partake in further heat exchanges and/or to be recycled within the system. Such provisions may be advantageous for the operation of an energy storage and generation system. For example, lowering the temperature of fluids within an LUR may be employed to reduce energy loss to, or increase energy gain from, surrounding rock, or may be employed to reduce pressure changes and associated mechanical stresses on the LUR's lining layers and surrounding rock. Such provisions may enable the conveyance of heat obtained from external surface sources (e.g., waste heat from a thermal power plant) to the fluid contents of the LUR, in which case the LUR will store energy both as the elastic potential energy of compressed air and as the thermal energy of warm fluids.
• The construction of LURs as storage reservoirs for energy-storage systems employing compressed air and near-isothermal compression and expansion is therefore advantageous as regards surface footprint, siting flexibility, safety, cost per unit of energy stored, and other aspects of cost and operation.
• Embodiments of the present invention may be utilized in energy storage and generation systems utilizing compressed gas. In a compressed-gas energy storage system, gas is stored at high pressure (e.g., approximately 3,000 psi). This gas may be expanded into a cylinder having a first compartment (or “chamber”) and a second compartment separated by a piston slidably disposed within the cylinder (or by another boundary mechanism). A shaft may be coupled to the piston and extend through the first compartment and/or the second compartment of the cylinder and beyond an end cap of the cylinder, and a transmission mechanism may be coupled to the shaft for converting a reciprocal motion of the shaft into a rotary motion, as described in the '678 and '842 patents. Moreover, a motor/generator may be coupled to the transmission mechanism. Alternatively or additionally, the shaft of the cylinders may be coupled to one or more linear generators, as described in the '842 patent.
• As also described in the '842 patent, the range of forces produced by expanding a given quantity of gas in a given time may be reduced through the addition of multiple, series-connected cylinder stages. That is, as gas from a high-pressure reservoir is expanded in one chamber of a first, high-pressure cylinder, gas from the other chamber of the first cylinder is directed to the expansion chamber of a second, lower-pressure cylinder. Gas from the lower-pressure chamber of this second cylinder may either be vented to the environment or directed to the expansion chamber of a third cylinder operating at still lower pressure; the third cylinder may be similarly connected to a fourth cylinder; and so on.
• The principle may be extended to more than two cylinders to suit particular applications. For example, a narrower output force range for a given range of reservoir pressures is achieved by having a first, high-pressure cylinder operating between, for example, approximately 3,000 psig and approximately 300 psig and a second, larger-volume, lower-pressure cylinder operating between, for example, approximately 300 psig and approximately 30 psig. When two expansion cylinders are used, the range of pressure within either cylinder (and thus the range of force produced by either cylinder) is reduced as the square root relative to the range of pressure (or force) experienced with a single expansion cylinder, e.g., from approximately 100:1 to approximately 10:1 (as set forth in the '853 application). Furthermore, as set forth in the '678 patent, N appropriately sized cylinders can reduce an original operating pressure range R to R^1/N. Any group of N cylinders staged in this manner, where N≧2, is herein termed a cylinder group.
• Every compression or expansion of a quantity of gas, where such a compression or expansion is herein termed “a gas process,” is generally one of three types: (1) adiabatic, during which the gas exchanges no heat with its environment and, consequently, rises or falls in temperature, (2) isothermal, during which the gas exchanges heat with its environment in such a way as to remain at constant temperature, and (3) polytropic, during which the gas exchanges heat with its environment but its temperature does not remain constant. Perfectly adiabatic gas processes are not practical because some heat is always exchanged between any body of gas and its environment (ideal insulators and reflectors do not exist); perfectly isothermal gas processes are not practical because for heat to flow between a quantity of gas and a portion of its environment (e.g., a body of liquid), a nonzero temperature difference must exist between the gas and its environment—e.g., the gas must be allowed to heat during compression in order that heat may be conducted to the liquid. Hence real-world gas processes are typically polytropic, though they may approximate adiabatic or isothermal processes. The Ideal Gas Law states that for a given quantity of gas having mass m, pressure p, volume V, and temperature T, pV=mRT, where R is the gas constant (R=287 J/K•kg for air). For an isothermal process, T is a constant throughout the process, so pV=C, where C is some constant.
• For a polytropic process, as will be clear to persons familiar with the science of thermodynamics, pVⁿ=C throughout the process, where n, termed the polytropic index, is some constant generally between 1.0 and 1.6. For n=1, pVⁿ=pV¹=pV=C, i.e., the process is isothermal. In general, a process for which n is close to 1 (e.g., 1.05) may be deemed approximately isothermal.
• For an adiabatic process, pV^γ=C, where γ, termed the adiabatic coefficient, is equal to the ratio of the gas's heat capacity at constant pressure Cp to its heat capacity at constant volume, C_V, i.e., γ=C_P/C_V. In practice, γ is dependent on pressure. For air, the adiabatic coefficient γ is typically between 1.4 and 1.6.
• Herein, we define a “substantially isothermal” gas process as one having n≦1.1. The gas processes conducted within cylinders described herein are preferably substantially isothermal with n≦1.05. Herein, wherever a gas process taking place within a cylinder assembly or storage reservoir is described as “isothermal,” this word is synonymous with the term “substantially isothermal.”
• The amount of work done in compression or expansion of a given quantity of gas varies substantially with polytropic index n. For compressions, the lowest amount of work done is for an isothermal process and the highest for an adiabatic process, and vice versa for expansions. Hence, for gas processes such as typically occur in the compressed-gas energy storage systems described herein, the end temperatures attained by adiabatic, isothermal, and substantially isothermal gas processes are sufficiently different to have practical impact on the operability and efficiency of such systems. Similarly, the thermal efficiencies of adiabatic, isothermal, and substantially isothermal gas processes are sufficiently different to have practical impact on the overall efficiency of such energy storage systems. For example, for compression of a quantity of gas from initial temperature of 20° C. and initial pressure of 0 psig (atmospheric) to a final pressure of 180 psig, the final temperature T of the gas will be exactly 20° C. for an isothermal process, approximately 295° C. for an adiabatic process, approximately 95° C. for a polytropic compression having polytropic index n=1.1 (10% increase in n over isothermal case of n=1), and approximately 60° C. for a polytropic compression having polytropic index n=1.05 (5% increase in n over isothermal case of n=1). In another example, for compression of 1.6 kg of air from an initial temperature of 20° C. and initial pressure of 0 psig (atmospheric) to a final pressure of approximately 180 psig, including compressing the gas into a storage reservoir at 180 psig, isothermal compression requires approximately 355 kilojoules of work, adiabatic compression requires approximately 520 kilojoules of work, and a polytropic compression having polytropic index n=1.045 requires approximately 375 kilojoules of work; that is, the polytropic compression requires approximately 5% more work than the isothermal process, and the adiabatic process requires approximately 46% more work than the isothermal process.
• It is possible to estimate the polytropic index n of gas processes occurring in cylinder assemblies such as are described herein by empirically fitting n to the equation pVⁿ=C, where pressure p and volume V of gas during a compression or expansion, e.g., within a cylinder, may both be measured as functions of time from piston position, known device dimensions, and pressure-transducer measurements. Moreover, by the Ideal Gas Law, temperature within the cylinder may be estimated from p and V, as an alternative to direct measurement by a transducer (e.g., thermocouple, resistance thermal detector, thermistor) located within the cylinder and in contact with its fluid contents. In many cases, an indirect measurement of temperature via volume and pressure may be more rapid and more representative of the entire volume than a slower point measurement from a temperature transducer. Thus, temperature measurements and monitoring described herein may be performed directly via one or more transducers, or indirectly as described above, and a “temperature sensor” may be one of such one or more transducers and/or one or more sensors for the indirect measurement of temperature, e.g., volume, pressure, and/or piston-position sensors.
• The systems described herein, and/or other embodiments employing foam-based heat exchange, liquid-spray heat exchange, and/or external gas heat exchange, may draw or deliver thermal energy via their heat-exchange mechanisms to external systems (not shown) for purposes of cogeneration, as described in U.S. Pat. No. 7,958,731, filed Jan. 20, 2010 (the '731 patent), the entire disclosure of which is incorporated by reference herein.
• The compressed-air energy storage and recovery systems described herein are preferably “open-air” systems, i.e., systems that take in air from the ambient atmosphere for compression and vent air back to the ambient atmosphere after expansion, rather than systems that compress and expand a captured volume of gas in a sealed container (i.e., “closed-air” systems). The systems described herein generally feature one or more cylinder assemblies for the storage and recovery of energy via compression and expansion of gas. The systems also include (i) a reservoir for storage of compressed gas after compression and supply of compressed gas for expansion thereof, and (ii) a vent for exhausting expanded gas to atmosphere after expansion and supply of gas for compression. The storage reservoir may include or consist essentially of, e.g., one or more IPVs, LURs, pressure vessels, (i.e., containers for compressed gas that may have rigid exteriors or may be inflatable, that may be formed of various suitable materials such as metal or plastic, and that may or may not fall within ASME regulations for pressure vessels), or caverns (i.e., naturally occurring or artificially created cavities that are typically located underground). Open-air systems typically provide superior energy density relative to closed-air systems.
• Furthermore, the systems described herein may be advantageously utilized to harness and recover sources of renewable energy, e.g., wind and solar energy. For example, energy stored during compression of the gas may originate from an intermittent renewable energy source of, e.g., wind or solar energy, and energy may be recovered via expansion of the gas when the intermittent renewable energy source is nonfunctional (i.e., either not producing harnessable energy or producing energy at lower-than-nominal levels). As such, the systems described herein may be connected to, e.g., solar panels or wind turbines, in order to store the renewable energy generated by such systems.
• In an aspect, embodiments of the invention feature a method of fabricating a lined underground reservoir. Rock is excavated at a site location to form an open shaft extending below ground level. A fluid-impermeable (i.e., impermeable to liquid such as water and/or gas such as air or natural gas) liner substantially enclosing an interior volume for containing at least one of compressed gas or heat-transfer liquid is assembled within or above the shaft. The interior volume is smaller than the total volume of the open shaft. The liner includes or consists essentially of an invert section enclosing a bottom of the interior volume, a dome section enclosing a top of the interior volume opposite the bottom, and a sidewall section substantially gaplessly spanning the invert and dome sections. After assembly, the liner is disposed within the shaft below ground level. A surround material is disposed to at least partially fill a gap between an outer surface of the liner and an inner surface of the shaft around at least a portion of the outer surface of the liner. After assembly of the liner and disposal of the surround material so as to form a surrounded liner, an overfill material is disposed over the surrounded liner to fill at least a portion of a space between the ground level and the surrounded liner. The interior volume enclosed by the liner is fluidly connected to a fluid source or fluid sink external to the surrounded liner, thereby forming the lined underground reservoir.
• Embodiments of the invention may feature one or more of the following in any of a variety of different combinations. The surround material may include or consist essentially of concrete or metal-reinforced concrete (e.g., concrete internally reinforced with a network of metal such as rebar). The liner may include or consist essentially of steel and/or plastic. The overfill material may include or consist essentially of rock, concrete, and/or metal-reinforced concrete. The overfill material may include or consist essentially of a volume of heat-transfer liquid (e.g., water). The overfill material may be the fluid source and/or fluid sink. Prior to disposing the overfill material, a plug, shaped to laterally distribute upward-acting forces resulting when the liner contains pressurized fluid, may be formed within the shaft. A width of the shaft around the plug may be larger than a width of the shaft around the surrounded liner. A cross-section of the plug, e.g., a cross-section in a plane approximately perpendicular to ground level, may be substantially trapezoidal or hexagonal. Prior to disposing the surround material, spacer may be disposed on the liner that defines at least a portion of the gap between the outer surface of the liner and the inner surface of the shaft around at least a portion of the outer surface of the liner. The shaft may be substantially fully formed prior to any portion of the liner being disposed therein. At least a portion of the surround material may be disposed within the shaft prior to the liner being disposed within the shaft. A mechanism for generating a foam or droplet spray may be disposed within the interior volume. The mechanism may be fluidly connected to a source of heat-transfer fluid external to the surrounded liner. An area within the interior volume of the liner proximate the invert section may be fluidly connected to a sink of heat-transfer fluid external to the surrounded liner.
• Assembling the liner may include or consist essentially of supporting a first portion of the liner above a bottom surface of the shaft such that a top surface of the first portion of the liner is proximate ground level, disposing a second portion of the liner on the top surface of the first portion of the liner to form an at least partially assembled liner, and lowering the at least partially assembled liner such that a top surface of the second portion of the liner is proximate ground level. Supporting the first portion of the liner may include or consist essentially of floating the first portion of the liner on a liquid within the shaft. Lowering the at least partially assembled liner may include or consist essentially of removing liquid from the shaft. Assembling the liner may include or consist essentially of filling at least a portion of the shaft with a liquid, floating a first portion of the liner on the liquid, proximate ground level, disposing a second portion of the liner on the first portion of the liner, and removing liquid from the shaft until a top surface of the second portion of the liner is proximate ground level. At least a portion of the surround material may be disposed on the inner surface of the shaft prior to filling the at least a portion of the shaft with the liquid. A spacer may be disposed on the first portion of the liner. The spacer may define at least a portion of the gap between the outer surface of the liner and the inner surface of the shaft around at least a portion of the outer surface of the liner. After the surround material is disposed within the gap, the surround material may have a substantially uniform thickness, defined by the spacer, around the liner. A portion of the surround material may be attached to each of the first and second sections of the liner proximate ground level. Each portion of the surround material may include or consist essentially of a network of metal.
• During disposal of the surround material, the interior volume of the liner may be at least partially filled with a liquid such that a top surface of the liquid is approximately coplanar with a top surface of the surround material. The sidewall section of the liner may include or consist essentially of a plurality of substantially cylindrical segments, and each cylindrical segment may include or consist essentially of a plurality of discrete curved portions connected at interfaces therebetween. The plurality of discrete curved portions may be welded together at the interfaces to form each of the substantially cylindrical segments. The fluid source or fluid sink external to the surrounded liner may be a compressed-gas energy storage and recovery system configured to store gas in the interior volume after compression thereof and extract gas from the interior volume before expansion thereof. The energy storage and recovery system may store, e.g., compressed air or natural gas, within the interior volume and/or extract it therefrom. A network of drainage pipes for channeling liquid away from the liner may be disposed between the outer surface of the liner and the inner surface of the shaft. Concrete may be sprayed on the network of drainage pipes. At least a portion of the surround material may be disposed within the shaft before the liner is assembled. The surround material may include or consist essentially of (i) a network of drainage pipes and (ii) concrete reinforced with metal. The shaft may be deepened after a first portion of the surround material is disposed within the shaft, and, thereafter, a second portion of the surround material may be disposed on the first portion of the surround material. The assembled liner may not be self-supporting in the absence of the surround material. The shaft may be deepened after a first portion of the liner is assembled within the shaft, and, thereafter, a second portion of the liner may be attached to the first portion of the liner.
• A portion of the surround material may be disposed over the dome section of the liner. The surround material may include or consist essentially of a concrete layer and, disposed between the concrete layer and the liner, a viscous layer for mitigating force on the liner. The concrete layer may include therewithin a network of metal (e.g., the concrete may be metal-reinforced concrete). The shaft may be substantially vertical. A region of the shaft disposed above the assembled liner may have a width or diameter approximately equal to or greater than a width or diameter of the assembled liner. The entire shaft may have a width or diameter approximately equal to or greater than a width or diameter of the assembled liner. During assembly of the liner and disposal of the surround material, the site location may be free of sub-surface access tunnels having a sufficiently large size and/or sufficiently shallow slope to accommodate vehicular traffic. Excavating rock may include or consist essentially of (a) excavating one or more holes at the site location where the shaft is to be formed, (b) placing an explosive in the one or more holes, (c) detonating the explosive to pulverize the rock, (d) removing the pulverized rock, and (e) optionally, repeating steps (a)-(d). Excavating rock may include or consist essentially of (a) pulverizing rock with a cutting mechanism mounted on a translatable telescoping boom to form at least a portion of the shaft, (b) removing the pulverized rock, and (c) optionally, lowering the cutting mechanism and boom into the at least a portion of the shaft and repeating steps (a) and (b). The surrounded liner may be configured to contain a fluid pressure of at least 200 bar, and the rock at the site location may have a rock mass rating of at least 50. The rock at the site location may have a rock mass rating RMR, and the surrounded liner may be configured to contain a maximum fluid pressure P in MPa defined by P≦(RMR×0.83)−25. A thickness of the liner may be insufficient to withstand a maximum internal fluid pressure of the lined underground reservoir, and the lined underground reservoir may be configured to withstand the maximum internal fluid pressure, notwithstanding the insufficient thickness of the liner, via at least one of the overfill or rock surrounding the surrounded liner withstanding a portion of the internal fluid pressure.
• In another aspect, embodiments of the invention feature a method of energy storage utilizing a compressed-gas energy storage system selectively fluidly connected to a lined underground reservoir at least partially surrounded by rock. Gas is substantially isothermally compressed with the energy storage system at a compression temperature. The compressed gas is transferred to the lined underground reservoir for storage. Thereafter, heat is exchanged between the stored compressed gas and the rock at least partially surrounding the lined underground reservoir to change a temperature of the stored gas to a storage temperature different from the compression temperature. The compressed gas may be thermally conditioned during transfer to the lined underground reservoir by (i) spraying droplets of a heat-transfer liquid into the gas and/or (ii) forming a foam comprising the gas and a heat-transfer liquid. The storage temperature may be lower than the compression temperature. The storage temperature may be higher than the compression temperature.
• In yet another aspect, embodiments of the invention feature a compressed-gas energy storage and recovery system that includes or consists essentially of a cylinder assembly for compressing gas to store energy and/or expanding gas to recover energy, a heat-exchange subsystem for thermally conditioning the gas during the compression and/or expansion via heat exchange between the gas and a heat-transfer liquid, a lined underground reservoir for storing compressed gas and/or heat-transfer fluid in an interior volume thereof, the lined underground reservoir being substantially impermeable to fluid and comprising an inner steel layer surrounded by an outer concrete layer, a source of heat-transfer fluid fluidly connected to the interior volume of the lined underground reservoir, and a sink for heat-transfer fluid fluidly connected to the interior volume of the lined underground reservoir.
• Embodiments of the invention may feature one or more of the following in any of a variety of different combinations. A nozzle for introducing heat-transfer fluid into the interior volume as a spray of droplets or as a foam may be disposed within the interior volume of the lined underground reservoir. A first pipe may fluidly connect the cylinder assembly to the interior volume of the lined underground reservoir. A second pipe may fluidly connect the source of heat-transfer fluid to the nozzle. A third pipe may fluidly connect an area proximate a bottom portion of the interior volume of the lined underground reservoir and the sink for heat-transfer fluid. A pump may be configured to transfer heat-transfer fluid through the third pipe to the sink for heat-transfer fluid. The source of heat-transfer fluid and the sink for heat-transfer fluid may be the same body of liquid. The source of heat-transfer fluid and the sink for heat-transfer fluid may be two discrete and separate bodies of liquid.
• In a further aspect, embodiments of the invention feature a compressed-gas energy storage and recovery system that includes or consists essentially of a cylinder assembly for at least one of compressing gas to store energy or expanding gas to recover energy, a heat-exchange subsystem for thermally conditioning the gas via heat exchange between the gas and a heat-transfer liquid, and selectively fluidly connected to the cylinder assembly, one or more insulated pipeline vessels (IPVs) for at least one of (i) storage of gas after compression, (ii) supply of compressed gas for expansion, (iii) storage of heat-transfer liquid, or (iv) supply of heat-transfer liquid.
• Embodiments of the invention may feature one or more of the following in any of a variety of different combinations. Each IPV may include or consist essentially of a base material at least partially surrounded by insulation for retarding heat exchange between contents of the IPV and surroundings of the IPV. Each IPV may include, disposed on at least a portion of its interior surface, a corrosion-resistant coating. At least one IPV may contain gas at a pressure higher than an ambient pressure and/or at a temperature higher than an ambient temperature. The one or more IPVs may be at least partially buried underground. At least one IPV may include an unburied access point for the inflow and outflow of gas and/or heat-transfer liquid. Each IPV may be at least partially disposed within a separate fill capsule (i) containing insulating fill and (ii) including an outer envelope substantially impermeable to liquid and/or air. Each fill capsule may be at least partially buried underground. The one or more IPVs may include or consist essentially of a plurality of IPVs, and two or more IPVs may be at least partially disposed within a fill capsule (i) containing insulating fill and (ii) including an outer envelope substantially impermeable to at least one of liquid or air. The fill capsule may be at least partially buried underground. All of the plurality of IPVs may be at least partially disposed within the fill capsule. The one or more IPVs may be each substantially linear and disposed lengthwise at a first non-zero angle to the horizontal such that a downhill end of each IPV is lower than an uphill end. At least one IPV may include, proximate the downhill end thereof, a first access point for the inflow and outflow of heat-transfer liquid. The at least one IPV may include, proximate the first access point, a second access point for the inflow and outflow of gas. The second access point may be disposed at a distance from the downhill end sufficient to prevent blockage of the second access point by heat-transfer liquid accumulating proximate the downhill end. A manifold pipe may be fluidly connectable to the first access points of one or more IPVs. The manifold pipe may be inclined lengthwise at a second non-zero angle to the horizontal. The manifold pipe may be disposed approximately perpendicular to lengths of the one or more IPVs. The second non-zero angle may be different from the first non-zero angle. At least two of the one or more IPVs may be fluidly connected by a connector. The connector may include or consist essentially of a manifold and/or a U-bend connector. At least one IPV may include therewithin a mechanism for the introduction of heat-transfer liquid. The mechanism for the introduction of heat-transfer liquid may include or consist essentially of a nozzle, a spray head, and/or a spray rod. A pump may supply heat-transfer liquid to the mechanism. Each IPV may have a length exceeding its diameter by a factor of at least 100. Each IPV may not fall within ASME regulations for pressure vessels. The heat-exchange subsystem may include a mechanism for (i) the introduction of heat-transfer liquid into gas in the form of droplets and/or (ii) the mingling of heat-transfer liquid with gas to form foam.
• In yet a further aspect, embodiments of the invention feature a compressed-gas energy storage and recovery system that includes or consists essentially of a cylinder assembly for compressing gas to store energy and/or expanding gas to recover energy, and a storage system for the storage of compressed gas and/or heat-transfer liquid. The storage system includes or consists essentially of a first approximately planar array of insulated pipeline vessels (IPVs). The first array is inclined at a first non-zero angle to the horizontal in a first direction and disposed at a second angle to the horizontal in a second direction perpendicular to the first direction.
• Embodiments of the invention may feature one or more of the following in any of a variety of different combinations. The second angle may be approximately zero or may be non-zero. The second angle may be different from the first angle. At least two of the IPVs of the first array may be fluidly connected to each other via at least one connector. The at least one connector may include or consist essentially of a manifold and/or at least one U-bend connector. The storage system may include, disposed over the first array, a second approximately planar array of IPVs. The second array may be approximately parallel to the first array. The second array may be inclined at a third non-zero angle to the horizontal in the first direction and disposed at a fourth angle to the horizontal in the second direction. The fourth angle may be approximately zero or may be non-zero. The second angle may be approximately equal to the fourth angle. The first angle may be approximately equal to the third angle. The first angle may be different from the third angle. Relative to the horizontal, an absolute value of the first angle may be approximately equal to an absolute value of the third angle. At least one of the IPVs of the first array may be fluidly connected to at least one of the IPVs of the second array by at least one connector. The at least one connector may include or consist essentially of a manifold or at least one U-bend connector. Each IPV may include or consist essentially of a base material at least partially surrounded by insulation for retarding heat exchange between contents of the IPV and surroundings of the IPV.
• In another aspect, embodiments of the invention feature a compressed-gas energy storage and recovery system that includes or consists essentially of a cylinder assembly for at least one of compressing gas to store energy or expanding gas to recover energy, a heat-exchange subsystem for thermally conditioning the gas via heat exchange between the gas and a heat-transfer liquid, and selectively fluidly connected to the cylinder assembly, a lined underground reservoir for at least one of (i) storage of gas after compression, (ii) supply of compressed gas for expansion, (iii) storage of heat-transfer liquid, or (iv) supply of heat-transfer liquid.
• Embodiments of the invention may feature one or more of the following in any of a variety of different combinations. The lined underground reservoir may include a liner at least partially surrounded by at least one of earth, dirt, or gravel. The liner may include or consist essentially of steel and/or concrete. A coating for sealing the liner to prevent fluid flow therethrough, preventing corrosion or degradation of the liner, and/or for thermally insulating the liner may be disposed on an inner surface of the liner and/or an outer surface of the liner. At least a portion of the lined underground reservoir may be disposed below ground level. The lined underground reservoir may include therein a liquid containment region disposed above a bottom surface of the lined underground reservoir. A spray head and/or nozzle for introducing heat-transfer liquid and/or foam may be disposed within the lined underground reservoir. The lined underground reservoir may include a container buried beneath and surrounded by at least one of earth, dirt, or gravel. The container may include or consist essentially of steel. Concrete, an insulating material, fiberglass, and/or carbon fiber may be disposed between the container and the earth, dirt, and/or gravel. The concrete, insulating material, fiberglass, and/or carbon fiber may be disposed directly on the container with substantially no gap or air therebetween. A circulation apparatus for pumping liquid disposed proximate a bottom surface of the lined underground reservoir to a point outside of the lined underground reservoir may be disposed within the lined underground reservoir. The lined underground reservoir may include therein a liquid containment region disposed above a bottom surface of the lined underground reservoir. A second circulation apparatus for pumping liquid disposed in the liquid containment region to a point outside of the lined underground reservoir may be disposed within the lined underground reservoir. A pipe for transferring gas between the cylinder assembly and the lined underground reservoir may extend from the cylinder assembly to a point within an interior volume of the lined underground reservoir. The lined underground reservoir may include or consist essentially of a plurality of discrete containers disposed within a shaft extending below ground level.
• These and other objects, along with advantages and features of the invention, will become more apparent through reference to the following description, the accompanying drawings, and the claims. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations. Note that as used herein, the terms “pipe,” “piping” and the like shall refer to one or more conduits that are rated to carry gas or liquid between two points. Thus, the singular term should be taken to include a plurality of parallel conduits where appropriate. Herein, the terms “liquid” and “water” interchangeably connote any mostly or substantially incompressible liquid, the terms “gas” and “air” are used interchangeably, and the term “fluid” may refer to a liquid, a gas, or a mixture of liquid and gas (e.g., a foam) unless otherwise indicated. As used herein unless otherwise indicated, the terms “approximately” and “substantially” mean ±10%, and, in some embodiments, ±5%. Herein, any fluid at a pressure higher than ambient atmospheric pressure is said to be “pressurized.” A “valve” is any mechanism or component for controlling fluid communication between fluid paths or reservoirs, or for selectively permitting control or venting. The term “cylinder” refers to a chamber, of uniform but not necessarily circular cross-section, which may contain a slidably disposed piston or other mechanism that separates the fluid on one side of the chamber from that on the other, preventing fluid movement from one side of the chamber to the other while allowing the transfer of force/pressure from one side of the chamber to the next or to a mechanism outside the chamber. At least one of the two ends of a chamber may be closed by end caps, also herein termed “heads.” As utilized herein, an “end cap” is not necessarily a component distinct or separable from the remaining portion of the cylinder, but may refer to an end portion of the cylinder itself. Rods, valves, and other devices may pass through the end caps. A “cylinder assembly” may be a simple cylinder or include multiple cylinders, and may or may not have additional associated components (such as mechanical linkages among the cylinders). The shaft of a cylinder may be coupled hydraulically or mechanically to a mechanical load (e.g., a hydraulic motor/pump or a crankshaft) that is in turn coupled to an electrical load (e.g., rotary or linear electric motor/generator attached to power electronics and/or directly to the grid or other loads), as described in the '678 and '842 patents. As used herein, “thermal conditioning” of a heat-exchange fluid does not include any modification of the temperature of the heat-exchange fluid resulting from interaction with gas with which the heat-exchange fluid is exchanging thermal energy; rather, such thermal conditioning generally refers to the modification of the temperature of the heat-exchange fluid by other means (e.g., an external heat exchanger). The terms “heat-exchange” and “heat-transfer” are generally utilized interchangeably herein. Unless otherwise indicated, motor/pumps described herein are not required to be configured to function both as a motor and a pump if they are utilized during system operation only as a motor or a pump but not both. Gas expansions described herein may be performed in the absence of combustion (as opposed to the operation of an internal-combustion cylinder, for example). The term “thermal well” refers herein to any mass (e.g., a quantity of fluid in an insulated container, or a solid thermal mass in an insulated container, or a portion of the earth) with which heat may be exchanged, whose temperature may be raised or lowered compared to some other mass (e.g., the environment), and which tends to retain rather than to dissipate any thermal energy stored within itself. Alternatively or additionally, a thermal well may employ material phase changes (e.g., melting and solidifying of a material) to store and release energy. As used herein, a “recessed” or “underground” storage reservoir is at least partially surrounded by and/or buried in material such as earth, dirt, gravel, and/or water or other liquid. Recessed storage reservoirs may be formed in (and may occupy substantially all of the space of) artificial and/or natural caverns.
BRIEF DESCRIPTION OF THE DRAWINGS
• In the drawings, like reference characters generally refer to the same parts throughout the different views. Cylinders, rods, and other components are depicted in cross section in a manner that will be intelligible to all persons familiar with the art of pneumatic and hydraulic cylinders. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present invention are described with reference to the following drawings, in which:
• FIG. 1A is a schematic drawing of an energy storage and generation facility employing lined underground reservoirs, accordance with various embodiments of the invention;
• FIG. 1B is a schematic drawing of an energy storage and generation facility employing insulated pipeline vessels, accordance with various embodiments of the invention;
• FIG. 1C is a schematic drawing of an energy storage and generation facility employing lined underground reservoirs, accordance with various embodiments of the invention;
• FIG. 1D is a schematic drawing of an energy storage and generation facility employing lined underground reservoirs, accordance with various embodiments of the invention;
• FIG. 2 is a schematic drawing of various components of a compressed-gas energy storage system in accordance with various embodiments of the invention;
• FIG. 3 is a schematic drawing of the major components of a compressed air energy storage and recovery system in accordance with various embodiments of the invention;
• FIG. 4 is a schematic drawing of various components of a compressed-gas energy storage system in accordance with various embodiments of the invention;
• FIG. 5 is a schematic drawing of various components of a multi-cylinder compressed-gas energy storage system in accordance with various embodiments of the invention;
• FIG. 6A is a schematic drawing of an insulated pipeline vessel in accordance with various embodiments of the invention;
• FIG. 6B is a schematic drawing of an insulated pipeline vessel and piping for accessing the contents thereof in accordance with various embodiments of the invention;
• FIG. 6C is a schematic drawing of an insulated pipeline vessel and a device for thermally regulating the contents thereof in accordance with various embodiments of the invention;
• FIG. 7A is a schematic drawing of an array of insulated pipeline vessels in accordance with various embodiments of the invention;
• FIG. 7B is a schematic drawing of an illustrative liquid-collection scheme for an IPV array in accordance with various embodiments of the invention;
• FIG. 7C is a schematic drawing of an illustrative, generalized, single-layer IPV array in accordance with various embodiments of the invention;
• FIG. 7D is a schematic drawing of an illustrative, generalized, two-layer IPV array with parallel layers in accordance with various embodiments of the invention;
• FIG. 7E is a schematic drawing of an illustrative, generalized, two-layer IPV array with layers at different angles in accordance with various embodiments of the invention;
• FIG. 7F is a schematic drawing of an illustrative, generalized, serpentine IPV array in accordance with various embodiments of the invention;
• FIG. 8 is a schematic drawing of a lined underground reservoir system for the storage and thermal conditioning of pressurized fluid in accordance with various embodiments of the invention;
• FIG. 9A is a schematic drawing of a lined underground reservoir system for the storage and thermal conditioning of pressurized fluid in accordance with various embodiments of the invention;
• FIG. 9B is a schematic drawing of a lined underground reservoir system for the storage and thermal conditioning of pressurized fluid, showing access tunnels built with level topography in accordance with various embodiments of the invention;
• FIG. 9C is a schematic drawing of a lined underground reservoir system for the storage and thermal conditioning of pressurized fluid, showing access tunnels built with high-relief topography in accordance with various embodiments of the invention;
• FIG. 10 is a schematic drawing of a lined underground reservoir system for the storage and thermal conditioning of pressurized fluid, showing a spiraling access tunnel in accordance with various embodiments of the invention;
• FIG. 11 is a schematic drawing of stages in the excavation of an open shaft for the creation of a recessed lined underground reservoir in accordance with various embodiments of the invention;
• FIG. 12A is a schematic drawing of a device for excavating an open shaft in accordance with various embodiments of the invention;
• FIG. 12B is a schematic drawing of a device for excavating an open shaft in accordance with various embodiments of the invention;
• FIG. 13 is a schematic drawing of a pipe network draining water from the vicinity of a lined underground reservoir in accordance with various embodiments of the invention;
• FIG. 14A is a schematic drawing of a multilayered lining for a lined underground reservoir in accordance with various embodiments of the invention;
• FIG. 14B is a schematic drawing of a multilayered lining for a lined underground reservoir in accordance with various embodiments of the invention;
• FIGS. 15A and 15B are schematic drawings of the effects of pressure-driven expansion upon a lined underground reservoir and surrounding rock in accordance with various embodiments of the invention;
• FIG. 16 is a plot of the deformation of a steel reservoir lining for three temperature and pressure cycles in accordance with various embodiments of the invention;
• FIG. 17 is a schematic drawing of stages in the construction of an inner liner for a lined underground reservoir in accordance with various embodiments of the invention;
• FIG. 18 is a schematic drawing of stages in the construction of a lined underground reservoir in accordance with various embodiments of the invention;
• FIG. 19 is a schematic drawing of stages in the construction of a lined underground reservoir in accordance with various embodiments of the invention;
• FIG. 20 is a schematic drawing of stages in the construction of a lined underground reservoir in accordance with various embodiments of the invention;
• FIG. 21A is a schematic drawing of stages in the construction of a lined underground reservoir in accordance with various embodiments of the invention;
• FIG. 21B is a schematic drawing of stages in the construction of a lined underground reservoir in accordance with various embodiments of the invention;
• FIG. 21C is a schematic drawing of stages in the construction of a lined underground reservoir in accordance with various embodiments of the invention;
• FIG. 21D is a schematic drawing showing details of the liner of a lined underground reservoir in accordance with various embodiments of the invention;
• FIG. 22 is a schematic drawing of a stage in the assembly of the liner of a lined underground reservoir in accordance with various embodiments of the invention;
• FIG. 23 is a schematic drawing of stages in the construction and lining of a lined underground reservoir in accordance with various embodiments of the invention;
• FIG. 24A is a schematic drawing of a lined underground reservoir showing a first design for a pressure barrier in accordance with various embodiments of the invention;
• FIG. 24B is a schematic drawing of a lined underground reservoir showing a second design for a pressure barrier in accordance with various embodiments of the invention;
• FIG. 24C is a schematic drawing of a lined underground reservoir showing the action of forces in the absence of a pressure barrier in accordance with various embodiments of the invention;
• FIG. 24D is a schematic drawing of a lined underground reservoir showing the action of forces in the presence of a pressure barrier in accordance with various embodiments of the invention;
• FIG. 25 is a schematic drawing of a lined underground reservoir employing construction cavities for the housing of machinery and storage of liquid in accordance with various embodiments of the invention;
• FIG. 26 is a schematic drawing of a lined underground reservoir employing a portion of a shaft for the storage of liquid in accordance with various embodiments of the invention;
• FIG. 27 is a schematic drawing of a lined underground reservoir system in which the lined cavity protrudes above the surface in accordance with various embodiments of the invention;
• FIG. 28 is a schematic drawing of a lined underground reservoir system in which the lined cavity protrudes above the surface and provisions are made for the circulation of a heat-transfer fluid within the reservoir in accordance with various embodiments of the invention;
• FIG. 29 is a schematic drawing of a cylinder assembly with apparatus for the generation of foam external to the cylinder in accordance with various embodiments of the invention;
• FIG. 30 is a schematic drawing of a cylinder assembly with apparatus for the generation of foam external to the cylinder and provision for bypassing the foam-generating apparatus in accordance with various embodiments of the invention;
• FIG. 31 is a schematic drawing of a cylinder assembly with apparatus for the generation of foam in a vessel external to the cylinder in accordance with various embodiments of the invention;
• FIG. 32 is a schematic drawing of a cylinder assembly with apparatus for the generation of foam in a vessel external to the cylinder in accordance with various embodiments of the invention;
• FIG. 33A is a plot of metal stress range as a function of cycle number for a lined underground reservoir pressurized gas storage system in accordance with various embodiments of the invention;
• FIG. 33B, incorporating, as shown, partial viewsFIG. 33B-1,FIG. 33B-2, andFIG. 33B-3, is a tabular presentation of the rock mass rating system utilized in accordance with various embodiments of the invention;
• FIG. 34 is a table and plot of criteria for rock quality pertaining to the construction of lined underground reservoirs in accordance with various embodiments of the invention;
• FIG. 35 is a plot of the total construction cost of a lined underground reservoir as a function of reservoir volume and overlying topography in accordance with various embodiments of the invention;
• FIG. 36 is a plot of the construction cost per cubic meter of a lined underground reservoir as a function of reservoir volume and overlying topography in accordance with various embodiments of the invention;
• FIG. 37 is a plot of the total construction cost of a lined underground reservoir as a function of reservoir volume, broken out by cost sector, in accordance with various embodiments of the invention; and
• FIG. 38 is a plot of the construction time of a lined underground reservoir as a function of reservoir volume and overlying topography in accordance with various embodiments of the invention.
DETAILED DESCRIPTION
• FIG. 1A schematically depicts anillustrative facility100A for the storage and generation of energy that employs two lined underground reservoirs (LURs)102,104 to store pressurized fluids. TheLURs102,104 may exchange fluids with an above-ground facility106 viapiping108. TheLURs102,104 depicted inFIG. 1A are of a capsule-like form typical for such reservoirs, namely, cylindrical with rounded inverts (floors)110,112 and domed ceilings (114,116). Linings and other details of theLURs102,104 and other components of thesystem100A are omitted fromFIG. 1A for clarity. The above-ground facility106 may be a gas processing facility that injects high-pressure gas for storage in theLURs102,104 and extracts the gas for distribution, or thefacility106 may be a generating facility that burns a fuel, e.g., natural gas, stored in theLURs102,104. Alternatively, thefacility106 may be a storage and generating facility that burns natural gas and renders such combustion more efficient by using compressed air fromLURs102,104, where the compressed air in theLURs102,104 may be provided by pumping air during hours of low electrical demand. Thefacility106 may even be a compressed-air-only energy storage and generation facility that pumps air into bothLURs102,104 during hours of low electrical demand or high generation by an associated renewable-energy facility (e.g., wind farm and/or solar cells; not shown) and generates energy by running generators using the energy released by expanding air from theLURs102,104. In particular, the above-ground facility106 may be a compressed-air energy storage and generation facility that uses approximately isothermal compression and storage as detailed herein.
• FIG. 1B schematically depicts anillustrative system100B that employsLUR102 to store an energy-storing fluid (e.g., methane, hydrogen, compressed gas).LUR102 exchanges the fluid through piping108 at asurface access point118, which features attachment points for piping and valves for directing and measuring fluid flow. Thesurface access point118 receives the fluid from a source/sink120 (e.g., well, hydrogen generator, shipping terminal) and may, in some modes of operation, direct the fluid to the source/sink120. Thesurface access point118 may also be connected to an aboveground fluid-handling facility122. The fluid-handling facility122 may process the fluid (e.g., cool and compress methane or reform methane with steam to produce hydrogen), or may utilize the energy contained within the fluid to produce electricity. The product of the fluid-handling facility122 (i.e., a fluid, electricity, etc.) may be delivered to an external user124 (e.g., power grid) or may, in some modes of operation, be directed to theLUR102 or to the external source/sink120. In various other embodiments, some or all components ofsystem100B, in addition to theLUR102, are located underground.
• FIG. 1C schematically depicts an illustrative system100C for the storage of energy and the generation of electricity that employs anLUR102 to store compressed air. System100C interconverts electrical energy with both thermal energy and the elastic potential energy of compressed air. To compress air for storage, system100C draws electrical power from a source/sink126 (e.g., power grid). The electrical power from the source/sink126 may be passed through atransformer128. After transformation, the power drives a motor/generator130. The motor/generator130 drives a compressor/expander132 (e.g., turbine, reciprocating piston, systems depicted inFIGS. 2-5, etc.) that raises ambient air to a higher-than-ambient pressure. The pressurized air is stored in theLUR102. Heat from the pressurized air is extracted and stored in a thermal energy sink134 (e.g., atmosphere, body of water, thermal well).
• To generate electricity from compressed air released from storage, compressed air from theLUR102 is expanded to a near-ambient pressure in the compressor/expander132 in a manner that performs mechanical work. Heat from a thermal energy source (e.g., combusted methane, waste heat from a fuel-burning generator) may be added to the air being expanded in the compressor/expander132 and is partially converted to mechanical work. The mechanical work derived from the compressed air and the thermal energy added thereto is directed to the motor/generator130. Electricity produced by the motor/generator130 is directed through thetransformer128 and thence to the source/sink126.
• In various other embodiments, system100C does not include a discretethermal energy sink134 orthermal energy source136. Motor/generator130 may be a single electric machine, or may consist of a separate motor and separate generator. Compressor/expander132 may be a single system or may be separate compressor unit and separate expander unit.
• FIG. 1D schematically depicts anillustrative system100D that employs an array of insulated pipeline vessels (IPVs)138 to store an energy-storing fluid (e.g., methane, hydrogen, compressed gas). TheIPV array138, which may be located either aboveground or partially or substantially wholly belowground, exchanges the fluid through piping108 ataccess point118, which includes attachment points for piping and valves for directing and measuring fluid flow. Thesurface access point118 receives the fluid from source/sink120 (e.g., well, hydrogen generator, shipping terminal) and may, in some modes of operation, direct the fluid to the source/sink120. Thesurface access point118 is also connected to aboveground fluid-handling facility122. The fluid-handling facility122 may process the fluid (e.g., cool and compress methane or reform methane with steam to produce hydrogen), or may utilize the energy contained within the fluid to produce electricity. The product of the fluid-handling facility122 (i.e., a fluid, electricity, or other) may be delivered to an external user124 (e.g., power grid) or may, in some modes of operation, be directed to theIPV array138 or to the external source/sink120. In various other embodiments, some or all components ofsystem100D are located underground, including theIPV array138; also in various other embodiments, more than one IPV array may be employed bysystem100D, in addition to one or more LURs (not shown).
• FIG. 2 depicts anillustrative system200 that may be part of a larger system, not otherwise depicted, for the storage and release of energy. Subsequent figures will clarify the application of embodiments of the invention to such a system. Thesystem200 depicted inFIG. 2 features anassembly201 for compressing and expanding gas. Expansion/compression assembly201 may include or consist essentially of either one or more individual devices for expanding or compressing gas (e.g., turbines or cylinder assemblies that each may house a movable boundary mechanism) or a staged series of such devices, as well as ancillary devices (e.g., valves) not depicted explicitly inFIG. 2.
• An electric motor/generator202 (e.g., a rotary or linear electric machine) is in physical communication (e.g., via hydraulic pump, piston shaft, or mechanical crankshaft) with the expansion/compression assembly201. The motor/generator202 may be electrically connected to a source and/or sink of electric energy not explicitly depicted inFIG. 2 (e.g., an electrical distribution grid or a source of renewable energy such as one or more wind turbines or solar cells).
• The expansion/compression assembly201 may be in fluid communication with a heat-transfer subsystem204 that alters the temperature and/or pressure of a fluid (i.e., gas, liquid, or gas-liquid mixture such as a foam) extracted from expansion/compression assembly201 and, after alteration of the fluid's temperature and/or pressure, returns at least a portion of it to expansion/compression assembly201. Heat-transfer subsystem204 may include pumps, valves, and other devices (not depicted explicitly inFIG. 2) ancillary to its heat-transfer function and to the transfer of fluid to and from expansion/compression assembly201. Operated appropriately, the heat-transfer subsystem204 enables substantially isothermal compression and/or expansion of gas inside expansion/compression assembly201.
• Connected to the expansion/compression assembly201 is apipe206 with acontrol valve208 that controls a flow of fluid (e.g., gas) betweenassembly201 and a storage reservoir212 (e.g., one or more pressure vessels, IPVs, and/or LURs). Thestorage reservoir212 may be in fluid communication with a heat-transfer subsystem214 that alters the temperature and/or pressure of fluid removed fromstorage reservoir212 and, after alteration of the fluid's temperature and/or pressure, returns it tostorage reservoir212. Asecond pipe216 with acontrol valve218 may be in fluid communication with the expansion/compression assembly201 and with avent220 that communicates with a body of gas at relatively low pressure (e.g., the ambient atmosphere).
• Acontrol system222 receives information inputs from any of expansion/compression assembly201,storage reservoir212, and other components ofsystem200 and sources external tosystem200. These information inputs may include or consist essentially of pressure, temperature, and/or other telemetered measurements of properties of components ofsystem201. Such information inputs, here generically denoted by the letter “T,” are transmitted to controlsystem222 either wirelessly or through wires. Such transmission is denoted inFIG. 2 bydotted lines224,226.
• Thecontrol system222 may selectively controlvalves208 and218 to enable substantially isothermal compression and/or expansion of a gas inassembly201. Control signals, here generically denoted by the letter “C,” are transmitted tovalves208 and218 either wirelessly or through wires. Such transmission is denoted inFIG. 2 by dashedlines228,230. Thecontrol system222 may also control the operation of the heat-transfer assemblies204,214 and of other components not explicitly depicted inFIG. 2. The transmission of control and telemetry signals for these purposes is not explicitly depicted inFIG. 2.
• Thecontrol system222 may be any acceptable control device with a human-machine interface. For example, thecontrol system222 may include a computer (for example a PC-type) that executes a stored control application in the form of a computer-readable software medium. More generally,control system222 may be realized as software, hardware, or some combination thereof. For example,control system222 may be implemented on one or more computers, such as a PC having a CPU board containing one or more processors such as the Pentium, Core, Atom, or Celeron family of processors manufactured by Intel Corporation of Santa Clara, Calif., the 680x0 and POWER PC family of processors manufactured by Motorola Corporation of Schaumburg, Ill., and/or the ATHLON line of processors manufactured by Advanced Micro Devices, Inc., of Sunnyvale, Calif. The processor may also include a main memory unit for storing programs and/or data relating to the methods described above. The memory may include random access memory (RAM), read only memory (ROM), and/or FLASH memory residing on commonly available hardware such as one or more application specific integrated circuits (ASIC), field programmable gate arrays (FPGA), electrically erasable programmable read-only memories (EEPROM), programmable read-only memories (PROM), programmable logic devices (PLD), or read-only memory devices (ROM). In some embodiments, the programs may be provided using external RAM and/or ROM such as optical disks, magnetic disks, or other storage devices.
• For embodiments in which the functions ofcontroller222 are provided by software, the program may be written in any one of a number of high-level languages such as FORTRAN, PASCAL, JAVA, C, C++, C#, LISP, PERL, BASIC or any suitable programming language. Additionally, the software can be implemented in an assembly language and/or machine language directed to the microprocessor resident on a target device.
• As described above, thecontrol system222 may receive telemetry from sensors monitoring various aspects of the operation ofsystem200, and may provide signals to control valve actuators, valves, motors, and other electromechanical/electronic devices.Control system222 may communicate with such sensors and/or other components of system200 (and other embodiments described herein) via wired or wireless communication. An appropriate interface may be used to convert data from sensors into a form readable by the control system222 (such as RS-232 or network-based interconnects). Likewise, the interface converts the computer's control signals into a form usable by valves and other actuators to perform an operation. The provision of such interfaces, as well as suitable control programming, is clear to those of ordinary skill in the art and may be provided without undue experimentation.
• System200 may be operated so as to compress gas admitted through thevent220 and store the gas thus compressed inreservoir212. For example, in an initial state of operation,valve208 is closed andvalve218 is open, admitting a quantity of gas into expansion/compression assembly201. When a desired quantity of gas has been admitted intoassembly201,valve218 may be closed. The motor/generator202, employing energy supplied by a source not explicitly depicted inFIG. 2 (e.g., the electrical grid), then provides mechanical power to expansion/compression assembly201, enabling the gas withinassembly201 to be compressed.
• During compression of the gas withinassembly201, fluid (i.e., gas, liquid, or a gas-liquid mixture) may be circulated betweenassembly201 and heat-exchange assembly204. Heat-exchange assembly204 may be operated in such a manner as to enable substantially isothermal compression of the gas withinassembly201. During or after compression of the gas withinassembly201,valve208 may be opened to enable high-pressure fluid (e.g., compressed gas or a mixture of liquid and compressed gas) to flow toreservoir212. Heat-exchange assembly214 may be operated at any time in such a manner as alter the temperature and/or pressure of the fluid withinreservoir212.
• Thatsystem200 may also be operated so as to expand compressed gas fromreservoir212 in expansion/compression assembly201 in such a manner as to deliver energy to the motor/generator202 will be apparent to all persons familiar with the operation of pneumatic, hydraulic, and electric machines.
• FIG. 3 depicts anillustrative system300 that features a cylinder assembly301 (i.e., an embodiment ofassembly201 inFIG. 2) in communication with a reservoir322 (212 inFIG. 1) and a vent to atmosphere323 (220 inFIG. 2). In theillustrative system300 shown inFIG. 3, thecylinder assembly301 contains apiston302 slidably disposed therein. In some embodiments thepiston302 is replaced by a different boundary mechanism dividingcylinder assembly301 into multiple chambers, orpiston302 is absent entirely, andcylinder assembly301 is a “liquid piston.” Thecylinder assembly301 may be divided into, e.g., two pneumatic chambers or one pneumatic chamber and one hydraulic chamber. Thepiston302 is connected to arod304, which may contain a center-drilled fluid passageway withfluid outlet312 extending from thepiston302. Therod304 is also attached to, e.g., a mechanical load (e.g., a crankshaft or a hydraulic system) that is not depicted. Thecylinder assembly301 is in liquid communication with a heat-transfer subsystem324 that includes or consists essentially of acirculation pump314 and aspray mechanism310 to enable substantially isothermal compression/expansion of gas. Heat-transfer fluid circulated bypump314 may be passed through a heat exchanger303 (e.g., tube-in-shell- or parallel-plate-type heat exchanger).Spray mechanism310 may include or consist essentially of one or more spray heads (e.g., disposed at one end of cylinder assembly301) and/or spray rods (e.g., extending along at least a portion of the central axis of cylinder assembly301). In other embodiments, a foam, rather than a spray of droplets, is created to facilitate heat exchange between liquid and gas during compression and expansion of gas within thecylinder assembly301, as described in U.S. patent application Ser. No. 13/473,128, filed May 16, 2012 (the '128 application), the entire disclosure of which is incorporated by reference herein. Foam may be generated by foaming gas with heat-exchange liquid in a mechanism (not shown, described in more detail below) external to thecylinder assembly301 and then injecting the resulting foam into thecylinder assembly301. Alternatively or additionally, foam may be generated inside thecylinder assembly301 by the injection of heat-exchange liquid intocylinder assembly301 through a foam-generating mechanism (e.g., spray head, rotating blade, one or more nozzles), partly or entirely filling the pneumatic chamber ofcylinder assembly301. In some embodiments, droplets and foams may be introduced intocylinder assembly301 simultaneously and/or sequentially. Various embodiments may feature mechanisms (not shown inFIG. 3) for controlling the characteristics of foam (e.g., bubble size) and for breaking down, separating, and/or regenerating foam.
• System300 further includes a first control valve320 (208 inFIG. 2) in communication with astorage reservoir322 andcylinder assembly301, and a second control valve321 (218 inFIG. 2) in communication with avent323 andcylinder assembly301. A control system326 (222 inFIG. 2) may control operation of, e.g.,valves322 and321 based on various system inputs (e.g., pressure, temperature, piston position, and/or fluid state) fromcylinder assembly301 and/orstorage reservoir322. Heat-transfer fluid (liquid or circulated bypump314 enters throughpipe313.Pipe313 may be (a) connected to a low-pressure fluid source (e.g., fluid reservoir (not shown) at the pressure to whichvent323 is connected or thermal well342); (b) connected to a high-pressure source (e.g., fluid reservoir (not shown) at the pressure of reservoir322); (c) selectively connected (using valve arrangement not shown) to low pressure during a compression process and to high pressure during an expansion process; (d) connected to changing-pressure fluid308 in thecylinder301 viaconnection312; or (e) some combination of these options.
• In an initial state, thecylinder assembly301 may contain a gas306 (e.g., air introduced to thecylinder assembly301 viavalve321 and vent323) and a heat-transfer fluid308 (which may include or consist essentially of, e.g., water or another suitable liquid). When thegas306 enters thecylinder assembly301,piston302 is operated to compress thegas306 to an elevated pressure (e.g., approximately 3,000 psi). Heat-transfer fluid (not necessarily the identical body of heat-transfer fluid308) flows frompipe313 to thepump314. Thepump314 may raise the pressure of the heat-exchange fluid to a pressure (e.g., up to approximately 3,015 psig) somewhat higher than the pressure within thecylinder assembly301, as described in U.S. Pat. No. 8,359,856, filed Jan. 19, 2011 (the '856 patent), the entire disclosure of which is incorporated by reference herein. Alternatively or in conjunction, embodiments of the invention add heat (i.e., thermal energy) to, or remove heat from, the high-pressure gas in thecylinder assembly301 by passing only relatively low-pressure fluids through a heat exchanger or fluid reservoir, as detailed in U.S. patent application Ser. No. 13/211,440, filed Aug. 17, 2011 (the '440 application), the entire disclosure of which is incorporated by reference herein.
• Heat-transfer fluid is then sent through apipe316, where it may be passed through a heat exchanger303 (where its temperature is altered) and then through apipe318 to thespray mechanism310. The heat-transfer fluid thus circulated may include or consist essentially of liquid or foam.Spray mechanism310 may be disposed within thecylinder assembly301, as shown; located in thestorage reservoir322 or vent323; or located in piping or manifolding around the cylinder assembly, such aspipe318 or the pipes connecting the cylinder assembly tostorage reservoir322 or vent323. Thespray mechanism310 may be operated in thevent323 or connecting pipes during compression, and a separate spray mechanism may be operated in thestorage reservoir322 or connecting pipes during expansion. Heat-transfer spray311 from spray mechanism310 (and/or any additional spray mechanisms), and/or foam from mechanisms internal or external to thecylinder assembly101, enable substantially isothermal compression ofgas306 withincylinder assembly301.
• In some embodiments, the heat exchanger303 is configured to condition heat-transfer fluid at low pressure (e.g., a pressure lower than the maximum pressure of a compression or expansion stroke in cylinder assembly301), and heat-transfer fluid is thermally conditioned between strokes or only during portions of strokes, as detailed in the '440 application. Embodiments of the invention are configured for circulation of heat-transfer fluid without the use of hoses that flex during operation through the use of, e.g., tubes or straws configured for non-flexure and/or pumps (e.g., submersible bore pumps, axial flow pumps, or other in-line style pumps) internal to the cylinder assembly (e.g., at least partially disposed within the piston rod thereof), as described in U.S. patent application Ser. No. 13/234,239, filed Sep. 16, 3011 (the '239 application), the entire disclosure of which is incorporated by reference herein.
• At or near the end of the compression stroke,control system326 opensvalve320 to admit thecompressed gas306 to thestorage reservoir322. Operation ofvalves320 and321 may be controlled by various inputs to controlsystem326, such as piston position incylinder assembly301, pressure instorage reservoir322, pressure incylinder assembly301, and/or temperature incylinder assembly301.
• As mentioned above, thecontrol system326 may enforce substantially isothermal operation, i.e., expansion and/or compression of gas incylinder assembly301, via control over, e.g., the introduction of gas into and the exhausting of gas out ofcylinder assembly301, the rates of compression and/or expansion, and/or the operation of the heat-exchange subsystem in response to sensed conditions. For example,control system326 may be responsive to one or more sensors disposed in or oncylinder assembly301 for measuring the temperature of the gas and/or the heat-exchange fluid withincylinder assembly301, responding to deviations in temperature by issuing control signals that operate one or more of the system components noted above to compensate, in real time, for the sensed temperature deviations. For example, in response to a temperature increase withincylinder assembly301,control system326 may issue commands to increase the flow rate ofspray311 of heat-exchange fluid308.
• Furthermore, embodiments of the invention may be applied to systems in which cylinder assembly301 (or a chamber thereof) is in fluid communication with a pneumatic chamber of a second cylinder (e.g., as shown inFIG. 5). That second cylinder, in turn, may communicate similarly with a third cylinder, and so forth. Any number of cylinders may be linked in this way. These cylinders may be connected in parallel or in a series configuration, where the compression and expansion is done in multiple stages.
• The fluid circuit of heat exchanger303 may be filled with water, a coolant mixture, an aqueous foam, or any other acceptable heat-exchange medium. In alternative embodiments, a gas, such as air or refrigerant, is used as the heat-exchange medium. In general, the fluid is routed by conduits to a large reservoir of such fluid in a closed or open loop. One example of an open loop is a well or body of water from which ambient water is drawn and the exhaust water is delivered to a different location, for example, downstream in a river. In a closed-loop embodiment, a cooling tower may cycle the water through the air for return to the heat exchanger. Likewise, water may pass through a submerged or buried coil of continuous piping where a counter heat-exchange occurs to return the fluid flow to ambient temperature before it returns to the heat exchanger for another cycle.
• In various embodiments, the heat-exchange fluid is conditioned (i.e., pre-heated and/or pre-chilled) or used for heating or cooling needs by connecting thefluid inlet338 andfluid outlet340 of the external heat-exchange side of the heat exchanger303 to an installation such as a heat-engine power plant, an industrial process with waste heat, a heat pump, and/or a building needing space heating or cooling, as described in the '731 patent. Alternatively, the external heat-exchange side of the heat exchanger303 may be connected to a thermal well342 as depicted inFIG. 3. The thermal well342 may include or consist essentially of a large water reservoir that acts as a constant-temperature thermal fluid source for use with the system. Alternatively, the water reservoir may be thermally linked to waste heat from an industrial process or the like, as described above, via another heat exchanger contained within the installation. This allows the heat-exchange fluid to acquire or expel heat from/to the linked process, depending on configuration, for later use as a heating/cooling medium in the energy storage/conversion system. Alternatively, the thermal well342 may include two or more bodies of energy-storage medium, e.g., a hot-water thermal well and a cold-water thermal well, that are typically maintained in contrasting energy states in order to increase the exergy ofsystem300 compared with a system in whichthermal well342 includes a single body of energy-storage medium. Storage media other than water may be utilized in thethermal well342; temperature changes, phase changes, or both may be employed by storage media of thermal well342 to store and release energy. Thermal or fluid links (not shown) to the atmosphere, ground, and/or other components of the environment may also be included insystem300, allowing mass, thermal energy, or both to be added to or removed from thethermal well342. Moreover, as depicted inFIG. 3, the heat-transfer subsystem324 does not interchange fluid directly with thethermal well342, but in other embodiments, fluid is passed directly between the heat-transfer subsystem324 and the thermal well342 with no heat exchanger maintaining separation between fluids.
• FIG. 4 is a schematic of the major components of anillustrative system400 that employs apneumatic cylinder402 to efficiently convert (i.e., store) mechanical energy into the potential energy of compressed gas and, in another mode of operation, efficiently convert (i.e., recover) the potential energy of compressed gas into mechanical work. Thepneumatic cylinder402 may contain a slidablydisposed piston404 that divides the interior of thecylinder402 into adistal chamber406 and aproximal chamber408. A port or ports (not shown) with associatedpipes412 and abidirectional valve416 enables gas from a high-pressure storage reservoir420 (e.g., one or more pressure vessels, IPVs, and/or LURs) to be admitted tochamber406 as desired. A port or ports (not shown) with associatedpipes422 and abidirectional valve424 enables gas from thechamber406 to be exhausted through avent426 to the ambient atmosphere as desired. In alternate embodiments, vent426 is replaced by additional lower-pressure pneumatic cylinders (or pneumatic chambers of cylinders). A port or ports (not shown) enables the interior of thechamber408 to communicate freely at all times with the ambient atmosphere. In alternate embodiments,cylinder402 is double-acting andchamber408 is, likechamber406, equipped to admit and exhaust fluids in various states of operation. The distal end of arod430 is coupled to thepiston404. Therod430 may be connected to a crankshaft, hydraulic cylinder, or other mechanisms for converting linear mechanical motion to useful work as described in the '678 and '842 patents.
• In the energy recovery or expansion mode of operation,storage reservoir420 is filled with high-pressure air (or other gas)432 and a quantity of heat-transfer fluid434. The heat-transfer fluid434 may be an aqueous foam or a liquid that tends to foam when sprayed or otherwise acted upon. The liquid component of the aqueous foam, or the liquid that tends to foam, may include or consist essentially of water with 2% to 5% of certain additives; these additives may also provide functions of anti-corrosion, anti-wear (lubricity), anti-biogrowth (biocide), freezing-point modification (anti-freeze), and/or surface-tension modification. Additives may include a micro-emulsion of a lubricating fluid such as mineral oil, a solution of agents such as glycols (e.g. propylene glycol), or soluble synthetics (e.g. ethanolamines). Such additives tend to reduce liquid surface tension and lead to substantial foaming when sprayed. Commercially available fluids may be used at an approximately 5% solution in water, such as Mecagreen 127 (available from the Condat Corporation of Michigan), which consists in part of a micro-emulsion of mineral oil, and Quintolubric 807-WP (available from the Quaker Chemical Corporation of Pennsylvania), which consists in part of a soluble ethanolamine. Other additives may be used at higher concentrations (such as at a 50% solution in water), including Cryo-tek 100/Al (available from the Hercules Chemical Company of New Jersey), which consists in part of a propylene glycol. These fluids may be further modified to enhance foaming while being sprayed and to speed defoaming when in a reservoir.
• The heat-transfer fluid434 may be circulated within thestorage reservoir420 via high-inlet-pressure, low-power-consumption pump436 (such as described in the '731 patent). In various embodiments, the fluid434 may be removed from the bottom of thestorage reservoir420 via piping438, circulated viapump436 through aheat exchanger440, and introduced (e.g., sprayed) back into the top ofstorage reservoir420 via piping442 and spray head444 (or other suitable mechanism). Any changes in pressure withinreservoir420 due to removal or addition of gas (e.g., via pipe412) generally tend to result in changes in temperature of thegas432 withinreservoir420. By spraying and/or foaming the fluid434 throughout thestorage reservoir gas432, heat may be added to or removed from thegas432 via heat exchange with the heat-transfer fluid434. By circulating the heat-transfer fluid434 throughheat exchanger440, the temperature of the fluid434 andgas432 may be kept substantially constant (i.e., isothermal). Counterflow heat-exchange fluid446 at near-ambient pressure may be circulated from a near-ambient-temperature thermal well (not shown) or source (e.g., waste heat source) or sink (e.g., cold water source) of thermal energy, as described in more detail below.
• In various embodiments of the invention,reservoir420 contains an aqueous foam, either unseparated or partially separated into its gaseous and liquid components. In such embodiments, pump436 may circulate either the foam itself, or the separated liquid component of the foam, or both, and recirculation of fluid intoreservoir420 may include regeneration of foam by apparatus not shown inFIG. 4.
• In the energy recovery or expansion mode of operation, a quantity of gas may be introduced viavalve416 andpipe412 into theupper chamber406 ofcylinder402 whenpiston404 is near or at the top of its stroke (i.e., “top dead center” of cylinder402). Thepiston404 and itsrod430 will then be moving downward (thecylinder402 may be oriented arbitrarily but is shown vertically oriented in this illustrative embodiment). Heat-exchange fluid434 may be introduced intochamber406 concurrently via optional pump450 (alternatively, a pressure drop may be introduced inline412 such that pump450 is not needed) through pipe452 anddirectional valve454. This heat-exchange fluid434 may be sprayed intochamber406 via one ormore spray nozzles456 in such a manner as to generatefoam460. (In some embodiments,foam460 is introduced directly intochamber406 in foam form.) Thefoam460 may entirely fill theentire chamber406, but is shown inFIG. 4, for illustrative purposes only, as only partially fillingchamber406. Herein, the term “foam” denotes either (a) foam only or (b) any of a variety of mixtures of foam and heat-exchange liquid in other, non-foaming states (e.g., droplets). Moreover, some non-foamed liquid (not shown) may accumulate at the bottom ofchamber406; any such liquid is generally included in references herein to thefoam460 withinchamber406.
• System400 is instrumented with pressure, piston position, and/or temperature sensors (not shown) and controlled viacontrol system462. At a predetermined position ofpiston404, an amount ofgas432 and heat-transfer fluid434 have been admitted intochamber406 andvalve416 andvalve454 are closed. (Valves416 and454 may close at the same time or at different times, as each has a control value based on quantity of fluid desired.) The gas inchamber406 then undergoes free expansion, continuing to drivepiston404 downward. During this expansion, in the absence offoam460, the gas would tend to decrease substantially in temperature. Withfoam460 largely or entirely filling the chamber, the temperature of the gas inchamber406 and the temperature of the heat-transfer fluid460 tend to approximate to each other via heat exchange. The heat capacity of the liquid component of the foam460 (e.g., water with one or more additives) may be much higher than that of the gas (e.g., air) such that the temperature of the gas and liquid do not change substantially (i.e., are substantially isothermal) even over a many-times gas expansion (e.g., from 250 psig to near atmospheric pressure, or in other embodiments from 3,000 psig to 250 psig).
• When thepiston404 reaches the end of its stroke (bottom dead center), the gas withinchamber406 will have expanded to a predetermined lower pressure (e.g., near atmospheric).Valve424 will then be opened, allowing gas fromchamber406 to be vented, whether to atmosphere throughpipe422 and vent426 (as illustrated here) or, in other embodiments, to a next stage in the expansion process (e.g., chamber in a separate cylinder), viapipe422.Valve424 remains open as the piston undergoes an upward (i.e., return) stroke, emptyingchamber406. Part or substantially all offoam460 is also forced out ofchamber406 viapipe422. A separator (not shown) or other means such as gravity separation is used to recover heat-transfer fluid, preferably de-foamed (i.e., as a simple liquid with or without additives), and to direct it into astorage reservoir464 viapipe466.
• Whenpiston404 reaches top of stroke again, the process repeats withgas432 and heat-transfer fluid434 admitted fromvessel420 viavalves416 and454. If additional heat-transfer fluid is needed inreservoir420, it may be pumped back intoreservoir420 fromreservoir464 via piping467 and optional pump/motor468. In one mode of operation, pump468 may be used to continuously refillreservoir420 such that the pressure inreservoir420 is held substantially constant. That is, as gas is removed fromreservoir420, heat-transfer fluid434 is added to maintain constant pressure inreservoir420. In other embodiments, pump468 is not used or is used intermittently, the pressure inreservoir420 continues to decrease during an energy-recovery process (i.e., involving removal of gas from reservoir420), and thecontrol system462 changes the timing ofvalves416 and454 accordingly so as to reach approximately the same ending pressure when thepiston404 reaches the end of its stroke. An energy-recovery process may continue until thestorage reservoir420 is nearly empty ofpressurized gas432, at which time an energy-storage process may be used to recharge thestorage reservoir420 withpressurized gas432. In other embodiments, the energy-recovery and energy-storage processes are alternated based on operator requirements.
• In either the energy-storage or energy-compression mode of operation,storage reservoir420 is typically at least partially depleted of high-pressure gas432, asstorage reservoir420 also typically contains a quantity of heat-transfer fluid434.Reservoir464 is at low pressure (e.g., atmospheric or some other low pressure that serves as the intake pressure for the compression phase of cylinder402) and contains a quantity of heat-transfer fluid470.
• The heat-transfer fluid470 may be circulated within thereservoir464 via low-power-consumption pump472. In various embodiments, the fluid470 may be removed from the bottom of thereservoir464 via piping467, circulated viapump472 through aheat exchanger474, and introduced (e.g., sprayed) back into the top ofreservoir464 via piping476 and spray head478 (or other suitable mechanism). By spraying the fluid470 throughout thereservoir gas480, heat may be added or removed from the gas via the heat-transfer fluid470. By circulating the heat-transfer fluid470 throughheat exchanger474, the temperature of the fluid470 andgas480 may be kept near constant (i.e., isothermal). Counterflow heat-exchange fluid482 at near-ambient pressure may be circulated from a near-ambient-temperature thermal well (not shown) or source (e.g., waste heat source) or sink (e.g., cold water source) of thermal energy. In one embodiment, counterflow heat-exchange fluid482 is at high temperature to increase energy recovery during expansion and/or counterflow heat-exchange fluid482 is at low temperature to decrease energy usage during compression.
• In the energy-storage or compression mode of operation, a quantity of low-pressure gas is introduced viavalve424 andpipe422 into theupper chamber406 ofcylinder402 starting whenpiston404 is near top dead center ofcylinder402. The low-pressure gas may be from the ambient atmosphere (e.g., may be admitted throughvent426 as illustrated herein) or may be from a source of pressurized gas such as a previous compression stage. During the intake stroke, thepiston404 and itsrod430 will move downward, drawing in gas. Heat-exchange fluid470 may be introduced intochamber406 concurrently via optional pump484 (alternatively, a pressure drop may be introduced inline486 such that pump484 is not needed) throughpipe486 anddirectional valve488. Thisheat exchange fluid470 may be introduced (e.g., sprayed) intochamber406 via one ormore spray nozzles490 in such a manner as to generatefoam460. Thisfoam460 may fill thechamber406 partially or entirely by the end of the intake stroke; for illustrative purposes only,foam460 is shown inFIG. 4 as only partially fillingchamber406. At the end of the intake stroke,piston404 reaches the end-of-stroke position (bottom dead center) andchamber406 is filled withfoam460 generated from air at a low pressure (e.g., atmospheric) and heat-exchange liquid.
• At the end of the stroke, withpiston404 at the end-of-stroke position,valve424 is closed.Valve488 is also closed, not necessarily at the same time asvalve424, but after a predetermined amount of heat-transfer fluid470 has been admitted, creatingfoam460. The amount of heat-transfer fluid470 may be based upon the volume of air to be compressed, the ratio of compression, and/or the heat capacity of the heat-transfer fluid. Next,piston404 androd430 are driven upwards via mechanical means (e.g., hydraulic fluid, hydraulic cylinder, mechanical crankshaft) to compress the gas withinchamber406.
• During this compression, in the absence offoam460, the gas inchamber406 would tend to increase substantially in temperature. Withfoam460 at least partially filling the chamber, the temperature of the gas inchamber406 and the temperature of the liquid component offoam460 will tend to equilibrate via heat exchange. The heat capacity of the fluid component of foam460 (e.g., water with one or more additives) may be much higher than that of the gas (e.g., air) such that the temperature of the gas and fluid do not change substantially and are near-isothermal even over a many-times gas compression (e.g., from near atmospheric pressure to 250 psig, or in other embodiments from 250 psig to 3,000 psig).
• The gas in chamber406 (which includes, or consists essentially of, the gaseous component of foam460) is compressed to a suitable pressure, e.g., a pressure approximately equal to the pressure withinstorage reservoir420, at whichtime valve416 is opened. Thefoam460, including both its gaseous and liquid components, is then transferred intostorage reservoir420 throughvalve416 andpipe412 by continued upward movement ofpiston404 androd430.
• Whenpiston404 reaches top of stroke again, the process repeats, with low-pressure gas and heat-transfer fluid470 admitted fromvent426 andreservoir464 viavalves424 and488. If additional heat-transfer fluid is needed inreservoir464, it may be returned toreservoir464 fromreservoir420 via piping467 and optional pump/motor468. Power recovered frommotor468 may be used to help drive the mechanical mechanism for drivingpiston404 androd430 or may be converted to electrical power via an electric motor/generator (not shown). In one mode of operation,motor468 may be run continuously, whilereservoir420 is being filled with gas, in such a manner that the pressure inreservoir420 is held substantially constant. That is, as gas is added toreservoir420, heat-transfer fluid434 is removed fromreservoir420 to maintain substantially constant pressure withinreservoir420. In other embodiments,motor468 is not used or is used intermittently; the pressure inreservoir420 continues to increase during an energy-storage process and thecontrol system462 changes the timing ofvalves416 and488 accordingly so that the desired ending pressure (e.g., atmospheric) is attained withinchamber406 when thepiston404 reaches bottom of stroke. An energy-storage process may continue until thestorage reservoir420 is full ofpressurized gas432 at the maximum storage pressure (e.g., 3,000 psig), after which time the system is ready to perform an energy-recovery process. In various embodiments, the system may commence an energy-recovery process when thestorage reservoir420 is only partly full ofpressurized gas432, whether at the maximum storage pressure or at some storage pressure intermediate between atmospheric pressure and the maximum storage pressure. In other embodiments, the energy-recovery and energy-storage processes are alternated based on operator requirements.
• FIG. 5 depicts anillustrative system500 that features at least two cylinder assemblies502,506 (i.e., an embodiment ofassembly201 inFIG. 2; e.g.,cylinder assembly301 inFIG. 3) and a heat-transfer subsystem504,508 (e.g.,subsystem324 inFIG. 3 associated with eachcylinder assembly502,506. Additionally, the system includes a thermal well510 (e.g., thermal well342 inFIG. 3) which may be associated with either or both of the heat-transfer subsystems504,508 as indicated by the dashed lines.
• Assembly502 is in selective fluid communication with a storage reservoir512 (e.g.,212 inFIG. 2,322 inFIG. 3) capable of holding fluid at relatively high pressure (e.g., approximately 3,000 psig).Assembly506 is in selective fluid communication with assembly502 and/or with optional additional cylinder assemblies betweenassemblies502 and506 as indicated by ellipsis marks522.Assembly506 is in selective fluid communication with an atmospheric vent520 (e.g.,220 inFIG. 2,323 inFIG. 3).
• System500 may compress air at atmospheric pressure (admitted tosystem500 through the vent520) stagewise throughassemblies506 and502 to high pressure for storage inreservoir512.System500 may also expand air from high pressure inreservoir512 stagewise throughassemblies502 and506 to a low pressure (e.g., approximately 5 psig) for venting to the atmosphere through vent520.
• As described in U.S. Pat. No. 8,191,362, filed Apr. 6, 2011 (the '362 patent), the entire disclosure of which is incorporated by reference herein, in a group of N cylinder assemblies used for expansion or compression of gas between a high pressure (e.g., approximately 3,000 psig) and a low pressure (e.g., approximately 5 psig), the system will contain gas at N−1 pressures intermediate between the high-pressure extreme and the low pressure. Herein each such intermediate pressure is termed a “mid-pressure.” Inillustrative system500, N=2 and N−1=1, so there is one mid-pressure (e.g., approximately 250 psig during expansion) in thesystem500. In various states of operation of the system, mid-pressures may occur in any of the chambers of a series-connected cylinder group (e.g., the cylinders of assemblies502 and506) and within any valves, piping, and other devices in fluid communication with those chambers. Inillustrative system500, the mid-pressure, herein denoted “mid-pressure P1,” occurs primarily in valves, piping, and other devices intermediate betweenassemblies502 and506.
• Assembly502 is a high-pressure assembly: i.e., assembly502 may admit gas at high pressure fromreservoir512 to expand the gas to mid-pressure P1 for transfer to assembly502, and/or may admit gas at mid-pressure P1 fromassembly506 to compress the gas to high pressure for transfer toreservoir512.Assembly506 is a low-pressure assembly: i.e.,assembly506 may admit gas at mid-pressure P1 from assembly502 to expand the gas to low pressure for transfer to the vent520, and/or may admit gas at low pressure from vent520 to compress the gas to mid-pressure P1 for transfer to assembly502.
• Insystem500, extended cylinder assembly502 communicates withextended cylinder assembly506 via a mid-pressure assembly514. Herein, a “mid-pressure assembly” includes or consists essentially of a reservoir of gas that is placed in fluid communication with the valves, piping, chambers, and other components through or into which gas passes. The gas in the reservoir is at approximately at the mid-pressure which the particular mid-pressure assembly is intended to provide. The reservoir is large enough so that a volume of mid-pressure gas approximately equal to that within the valves, piping, chambers, and other components with which the reservoir is in fluid communication may enter or leave the reservoir without substantially changing its pressure. Additionally, the mid-pressure assembly may provide pulsation damping, additional heat-transfer capability, fluid separation, and/or house one or more heat-transfer sub-systems such as part or all ofsub-systems504 and/or508. As described in the '362 patent, a mid-pressure assembly may substantially reduce the amount of dead space in various components of a system employing pneumatic cylinder assemblies, e.g.,system500 inFIG. 5. Reduction of dead space tends to increase overall system efficiency.
• Alternatively or in conjunction, pipes and valves (not shown inFIG. 5) bypassing mid-pressure assembly514 may enable fluid to pass directly between assembly502 andassembly506.Valves516,518,524, and526 control the passage of fluids between theassemblies502,506,512, and514.
• A control system528 (e.g.,222 inFIG. 2,326 inFIG. 3,462 inFIG. 4) may control operation of, e.g., all valves ofsystem500 based on various system inputs (e.g., pressure, temperature, piston position, and/or fluid state) fromassemblies502 and506, mid-pressure assembly514,storage reservoir512, thermal well510,heat transfer sub-systems504,508, and/or the environment surrounding system520.
• It will be clear to persons reasonably familiar with the art of pneumatic machines that a system similar tosystem500 but differing by the incorporation of one, two or more mid-pressure extended cylinder assemblies may be devised without additional undue experimentation. It will also be clear that all remarks herein pertaining tosystem500 may be applied to such an N-cylinder system without substantial revision, as indicated byelliptical marks522. Such N-cylinder systems, though not discussed further herein, are contemplated and within the scope of the invention. As shown and described in the '678 patent, N appropriately sized cylinders, where N≧2, may reduce an original (single-cylinder) operating fluid pressure range R to R^1/Nand correspondingly reduce the range of force acting on each cylinder in the N-cylinder system as compared to the range of force acting in a single-cylinder system. This and other advantages, as set forth in the '678 patent, may be realized in N-cylinder systems. Additionally, multiple identical cylinders may be added in parallel and attached to a common or separate drive mechanism (not shown) with thecylinder assemblies502,506 as indicated byellipsis marks532,536, enabling higher power and air-flow rates.
• Pressurized fluids may also be stored in accordance with various embodiments of the present invention, alternatively or additionally to the use of LURs, in insulated pipeline vessels (IPVs).FIG. 6A is a cross-sectional schematic drawing of an illustrative insulated pipeline vessel (IPV)system600 for the storage of fluid at pressures up to some relatively high value (e.g., 3,000 psig) and at temperatures up to some relatively elevated temperature (e.g., 100° C.). The drawing inFIG. 6A shows a side view. TheIPV system600, which may be part of the storage subsystem of an energy storage-and-recovery system (not shown), features a single length ofpipeline602, e.g., natural-gas pipeline, which in this illustrative case has length L (e.g., an interval of 40 or 80 foot sections) and an interior diameter of D (e.g., 32 inches). The cross-sectional shape of thepipeline602 is circular in thisillustrative system600, but various other embodiments have other cross-sectional shapes. Additional components ofillustrative system600, some optional, are depicted in subsequent figures. All illustrative IPV systems depicted herein, including arrays of IPV pipeline sections, may be utilized in energy-storage-and-recovery systems whose other components are not depicted.
• The single length ofpipeline602 may include or consist essentially of two or more shorter lengths of pipe (e.g., in thisillustrative pipeline602, the sub-lengths604,606), welded together or otherwise joined in fluid-proof manner at one ormore joints608. End caps610,612 seal the ends of thepipeline602 to form an enclosed volume: in this illustrative case, end-caps610,612 are bolted to flanges on the ends ofpipeline602.Pipeline602 is generally tilted at some angle θ₁from the horizontal. A layer ofinsulation614 covers the outer surface of thepipeline602. Additional insulation or protective coatings (not shown) may be applied as layers to the interior of thepipeline602.Pipeline602 may be substantially or wholly buried within a berm or fillcapsule616 including or consisting essentially offill618 and a substantiallyimpermeable envelope620. Thefill618 may include or consist essentially of various forms of earth (e.g., sand, crushed rock), an artificial thermal insulation material, or a mixture of earth and insulating material. Thefill618 is preferably dry (i.e., contains no substantial fraction of liquid water), in order that the thermal insulating power of thefill capsule616 may be maximal. Theimpermeable envelope620 prevents circulation of liquid and possibly air into and through thefill capsule616, increasing the thermal insulating power of thefill capsule616. The thickness of thefill capsule616 as measured from various points on the outer surface of thepipeline612 to theimpermeable envelope620 may vary from point to point, but will preferably be chosen to meet structural requirements and produce an insulating effect on thepipeline602 that justifies the cost of constructing the fill capsule616 (e.g., justifies the cost of constructing thefill capsule616 in terms of levelized cost of energy of the storage subsystem comprising IPV system600).
• Thelower end622 of thepipeline602 in theillustrative IPV system600 is allowed to protrude from thefill capsule616. Thesystem600 may be partly or entirely buried in earth (e.g., the earth naturally present at a given installation site; not shown), in which case a trench, pit, or vault (not shown) may be constructed to allow maintenance access to thelower end622 of thepipeline602.
• Thefirst insulation layer614 and the insulatingfill capsule616 serve jointly to slow to an acceptable rate the exchange of thermal energy between the fluid contents ofpipeline616 and the ambient environment ofsystem600.
• FIG. 6B shows additional components of theillustrative IPV system600 ofFIG. 6A. An accumulation ofliquid624 may exist at thelower end622 of thepipeline602. Thepipeline602 may also contain gas and aqueous foam or droplets (not shown). Apipe626 enables the withdrawal of liquid from (or the introduction of gas or liquid into)pipeline602 through anaccess point628. Apipe630 enables the withdrawal of gas from (or the introduction of gas or liquid into)pipeline602 through anaccess point632. Alternatively or additionally, bothpipes626 and630 may enable the exchange of two-phase fluids with thepipeline602.System600 may include valves (e.g., valves controlling flow throughpipes626 and630), pumps, and other components not depicted inFIG. 6B. Preferably, theliquid accumulation624 is not allowed to achieve a depth that blocks the point wherepipe630 is connected to the interior ofpipeline602. The points at whichpipes626 and630 connect to the interior ofpipeline602 in system600 (i.e., the insertion points634,636 ofpipes626 and630) are not necessarily drawn to scale; e.g., theinsertion point636 ofpipe630 may be farther fromend622 than shown inFIG. 6B, allowing theliquid accumulation624 to achieve a greater depth without blocking theinsertion point636 ofpipe630. In other embodiments, angle θ₁is negative, and theinsertion point634 ofpipe626 is at the far end of thepipe602 fromend622.
• FIG. 6C shows optional components of theillustrative IPV system600 ofFIG. 6A. In particular, aspray rod638 is positioned insidepipeline602. In other embodiments, thespray rod638 is external to thepipeline602 with spaced nozzle holes penetrating thepipeline602 at appropriate intervals (e.g., one nozzle penetration per meter). Liquid or a two-phase mixture (e.g., foam)640 may be injected, indicated inFIG. 6C by a row of short arrows, into the interior ofpipeline602, where it may proceed to exchange heat with the fluid contents of pipeline602 (e.g., stored, expanding, or compressing gas). In other embodiments, devices other than spray rods (e.g., spray heads) are employed (alone or in conjunction with spray rods) to inject thefluid640. The fluid640 may be fluid withdrawn frompipeline602 viapipe626 and circulated through a pump (not shown), heat exchanger (not shown), and/or other devices (not shown) before being injected throughspray rod638; or, the fluid640 may be supplied tospray rod638 from a reservoir (not shown) or other source or subsystem. By the injection offluid640 at an appropriate temperature and rate, the temperature of the fluid contents ofpipeline602 may be kept approximately constant as gas and liquid are added or removed frompipeline602; or, the temperature of the fluid contents ofpipeline602 may be increased or decreased at any time, or may be kept approximately constant during the addition of fluid to pipeline602 (which will tend to increase pressure and temperature of the fluid contents of pipeline602) or during the withdrawal of fluid from pipeline602 (which will tend to decrease pressure and temperature of the fluid contents of pipeline602). Holding the temperature of the fluid contents ofpipeline602 approximately equal throughout the volume ofpipeline602 and/or approximately constant during the addition or removal of fluid (i.e., realizing a substantially isothermal process) will tend to increase the overall efficiency of the energy storage system of whichsystem600 is a part, and is therefore advantageous.
• The preferable value of the angle θ₁, and of other angles of IPV tilt in other illustrative systems described herein, depends on the amounts of liquid found in each IPV in various states of system operation, the rates at which liquid is introduced into and removed from each IPV, and the inner dimensions of each IPV (e.g., diameter, length, locations of points of piping insertion). In accordance with various embodiments of the invention, the angle of IPV tilt may even be altered during operation via mechanical means, e.g., a tiltable stage.
• FIG. 7A is a schematic diagram of components of anillustrative IPV array700 including or consisting essentially of an array of N IPV pipeline sections (only oneIPV pipeline section702 is explicitly labeled inFIG. 7A). Herein, the terms “IPV pipeline section” and “IPV” are synonymous.FIG. 7A shows theIPV array700 from an overhead point of view. TheN IPVs702 are joined in pairs by N/2 U-shaped connector pipes (only oneU-shaped connector pipe704 is explicitly labeled inFIG. 7A). In various other embodiments, theU-shaped connectors704 are omitted or their function is performed by other forms of piping. Vertical ellipses706 indicate the presence of an indefinite number of additional pipeline sections in thearray700. Each IPV section inFIG. 7A (e.g., section702) is similar toIPV system600 inFIGS. 6A,6B,6C and may include any or all of the arrangements described or depicted forsystem600, as well as additional arrangements. For example,array700 may be enclosed by a fill capsule with an impermeable envelope to slow the exchange of thermal energy between the fluid contents ofarray700 and the ambient environment, or a separate fill capsule may enclose each IPV section in thearray700. Although the number N of IPV pipeline sections inFIG. 7A is depicted as equal to or greater than 6, any N equal to or greater than 1 is contemplated and within the scope of the invention.
• Thepipeline sections702 of theillustrative array700 are parallel to each other and lie in a common plane; in various embodiments, thepipeline sections702 may not be co-planar. The plane in which thepipeline sections702 lie is tilted at some angle θ₁from the horizontal, with the lower end of the plane at the left-hand side ofFIG. 7A. By gravity, liquid and two-phase mixtures will tend to flow downhill to the downhill ends of the IPVs, i.e., the ends at the left-hand side ofFIG. 7A. The angle θ₁is preferably larger than but close to the minimum angle that will cause acceptably rapid flow of fluid to the downhill end of each IPV in thearray700 without causing fluid blockage of the insertion points of the pipes (e.g.,708) that permit exchange of gas with each IPV section.
• At the downhill end of each IPV section inFIG. 7A (e.g., pipe section702), piping708 permits fluid (e.g., liquid) to be added to or withdrawn from the pipe section through amanifold pipe710 and asurface access point712. Also at the lower end of each IPV section inFIG. 7A (e.g., pipe section702), piping714 permits fluid (e.g., gas or foam) to be added to or withdrawn from the pipe section through amanifold pipe716 and asurface access point718.
• Uniformly spaced, straight, parallel (at least in one plane) IPV pipeline sections of uniform diameter and identical length and diameter are depicted inFIG. 7A and in various depictions of illustrative IPV arrays herein, but in various other embodiments, arrayed IPV sections need not be straight, parallel, uniformly spaced, uniform in diameter, or identical in length and/or diameter. Alternative embodiments of all illustrative IPV arrays depicted herein may be readily devised in which the arrayed IPV pipeline sections are not straight, parallel, uniformly spaced, uniform in diameter, or identical in length and/or diameter in accordance with embodiments of the invention. In various embodiments, IPV arrays are interconnected with other forms of fluid storage, e.g., lined or unlined underground reservoirs and non-IPV storage vessels, to provide energy and fluid storage for one or more energy storage-and-recovery systems.
• FIG. 7B is a schematic cross-section of portions of theIPV array700 ofFIG. 7A. The cross-section shows the downhill ends of thearray700, with aliquid accumulation720 in each IPV. (Only oneliquid accumulation720, i.e., that in the Nth IPV, is explicitly labeled inFIG. 7B. Although similar liquid accumulations are shown in other IPVs inFIG. 7B, each IPV may contain a different amount of liquid accumulation.) At the downhill end of each IPV depicted in cross-section inFIG. 7B, piping708 permits liquid to be added to or withdrawn from the IPV through amanifold pipe710 andaccess point712. Also at the downhill ends of the IPVs depicted in cross-section inFIG. 7B, piping714 permits fluid (e.g., gas or foam) to be added to or withdrawn from the pipe section throughmanifold pipe716 andsurface access point718. The plane in which the N IPVs ofarray700 lie is tilted only along the lengthwise dimension of the IPVs themselves: i.e., any perpendicular cross-sectional view ofarray700, such asFIG. 7B, will show a level row of pipeline cross-sections, although the altitude of that level row will be higher for cross-sections closer to the elevated edge of the array (the right-hand edge of the array inFIG. 7A).
• Inillustrative IPV array700, themanifold pipe710 is tilted at some angle θ with sufficient to guarantee downhill flow of liquid from all N IPV pipeline sections to thelow point722 ofmanifold710. A sump or reservoir (not shown) located approximately atpoint722 may allow an accumulation of liquid. A pump (not shown) may be employed to raise liquid frompoint722 or from a sump located approximately atpoint722 to theliquid access point712. Gas pressure in the N IPV pipeline sections may contribute to or entirely cause the movement of liquid from the IPV s to theaccess point712. In various other embodiments, angle θ is zero and pumping and/or gas pressure are entirely responsible for the movement of liquid from the N IPV pipeline sections to theaccess point712.
• FIG. 7C is a schematic diagram of components of an illustrativerectangular IPV array723 including or consisting essentially of N similar, parallel IPV pipeline sections (only oneIPV724 is explicitly labeled inFIG. 7C). Each IPV section inFIG. 7C is similar toIPV system600 inFIGS. 6A,6B,6C and may include any or all of the arrangements described or depicted forsystem600, as well as additional arrangements. TheIPV array723 may also include any or all of the arrangements described or depicted forarray700 inFIGS. 7A and 7B, as well as additional arrangements.FIG. 7C indicates the level plane ABCD (726) and the orientation of three standard orthogonal axes x, y, and z (728). The N IPV pipeline sections ofarray723 are parallel to one another and lie in a common plane that is tilted at angle θ₁with respect to they axis and at angle θ₂with respect to the x axis. Herein, the edge of theIPV array723 that lies along a straight line at angle θ₂with respect to the x axis is termed the CD edge (because of its proximity to the line segment CD). By extension of this convention, the other three edges of thearray723 are herein termed the AB, AC, and BD edges. One or more manifolds or U-connector pipes (not shown) enable fluid communication between the interiors of the N IPV pipeline sections ofarray723 and the delivery of gas to, or removal of gas from, the pipeline sections. Optional manifolds or U-connector pipes (not shown) may allow passive downhill liquid flow along the CD and/or AB edges ofarray723. Manifolds or piping (not shown) may also allow fluid to pass between the N IPV pipeline sections at points located anywhere along the pipeline sections. The angles θ₁and θ₂may be selected, in combination with optional manifolds and piping, to provide acceptable gravity-assisted flow, pooling, and collection through manifolds of liquid or other flowing fluid (e.g., foam) withinarray723 without interfering with access to the gaseous contents of array723 (e.g., by liquid blockage of openings intended for the passage of gas or two-phase mixtures). Preferably, manifolds and piping of thearray723 are arranged so that gas and liquid (and/or two-phase mixtures of gas and liquid) may be delivered to or removed from thearray723 from a closely clustered set of surface access points (e.g., near the A corner ofarray723 or at some point along the AB edge of array723).
• FIG. 7D is a schematic diagram of components of an illustrativerectangular IPV array729 including or consisting essentially of2N similar, parallel pipeline sections (only oneIPV pipeline section724 is explicitly labeled inFIG. 7D). Each IPV section inFIG. 7D is similar toIPV system600 inFIGS. 6A,6B,6C and may include any or all of the arrangements described or depicted forsystem600, as well as additional arrangements. TheIPV array729 may also include any or all of the arrangements described or depicted forarrays700,723 inFIGS. 7A,7B, and7C, as well as additional arrangements.FIG. 7D indicates the level plane ABCD (726) and the orientation of three standard orthogonal axes x, y, and z (728). The 2N IPV pipeline sections ofarray729 are parallel to one another and lie in two parallel planes, each tilted at angle θ₁with respect to the y axis and at angle θ₂with respect to the x axis.Array729 thus includes or consists essentially of two parallel, tilted layers or ranks of N IPV pipeline sections each. Piping or U-connectors may connect IPVs in the upper rank to pipes in the lower layer (e.g., each IPV in the upper rank may be connected to the IPV directly below it, or to some other IPV in the lower rank). Such piping may be arranged to allow for the delivery to or extraction from thearray729 of gas, liquid, or two-phase mixtures of gas and liquid. Such piping may be arranged in a wide variety of configurations to allow the passive drainage of liquid from IPVs in the upper rank to IPVs in the lower rank, or, in general, from any portion of any IPV where liquid may accumulate to any portion of any other IPV if that portion of the latter IPV is at lower elevation than the liquid accumulation in the former IPV. The angles θ₁and θ₂may be selected, in combination with optional manifolds and piping, to provide acceptable gravity-assisted flow, pooling, and collection through manifolds of liquid or other flowing fluid (e.g., foam) withinarray729 without interfering with access to the gaseous contents of array729 (e.g., by liquid blockage of openings intended for the passage of gas or two-phase mixtures). Preferably, manifolds and piping of thearray729 are arranged so that gas and liquid (and/or two-phase mixtures of gas and liquid) may be delivered to or removed from thearray729 from a closely clustered set of surface access points (e.g., near the A corner ofarray729 or at some point along the AB edge of array729).FIG. 7D depicts what is in effect a stack of two IPV arrays, each containing N IPV pipeline sections, but similar stacks of M IPV layers, where M is any integer number greater than or equal to1 and where the M layers may contain varying numbers of IPV pipeline sections, are contemplated and within the scope of the invention.
• FIG. 7E is a schematic diagram of components of an illustrativerectangular IPV array730 including or consisting essentially of 2N similar, parallel pipeline sections (only oneIPV pipeline section724 is explicitly labeled inFIG. 7E). Each IPV section inFIG. 7E is similar toIPV system600 inFIGS. 6A,6B,6C and may include any or all of the arrangements described or depicted forsystem600, as well as additional arrangements. TheIPV array730 may also include any or all of the arrangements described or depicted for700,723,729 inFIGS. 7A-7D, as well as additional arrangements.FIG. 7E indicates the level plane ABCD (726) and the orientation of three standard orthogonal axes x, y, and z (728). The N IPV pipeline sections of the lower layer ofarray730 are parallel to one another and lie in a common plane that is tilted at angle θ₁with respect to they axis and at angle θ₂with respect to the x axis. The N IPV pipeline sections of the upper layer ofarray730 are parallel to one another and lie in a common plane that is tilted at angle θ₃with respect to they axis and at angle θ₂with respect to the x axis.Array730 thus includes or consists essentially of two layers or ranks of NIPV pipeline sections each. Piping or U-connectors may connect IPVs in the upper rank to pipes in the lower layer (e.g., each IPV in the upper rank may be connected to the IPV directly below it, or to some other IPV in the lower rank). Such piping may be arranged to allow for the separate delivery to, or extraction from, thearray730 of gas, liquid, or two-phase mixtures of gas and liquid. Such piping may be arranged in a wide variety of configurations to allow the passive drainage of liquid from IPVs in the upper rank to IPVs in the lower rank, or, in general, from any portion of any IPV where liquid may accumulate to any portion of any other IPV if that portion of the latter IPV is at lower elevation than the liquid accumulation in the former IPV. For example, connecting each IPV in the upper layer ofarray730 to IPV in the lower rank at the CD edge (where the two layers of IPVs approximate), e.g., by a vertically oriented U-connector, would be advantageous because no further connections to the upper layer of IPVs would be necessary in order for gas to be exchanged freely between each IPV of the upper layer and the corresponding IPV of the lower layer, while liquid would flow by gravity from each IPV of the upper layer into the corresponding IPV of the lower layer, to be further directed and collected for removal from thearray730. The angles θ₁, θ₂, and θ₃may be selected, in combination with optional manifolds and piping, to provide acceptable gravity-assisted flow, pooling, and manifold collection of liquid or other flowing fluid (e.g., foam) withinarray730 without interfering with access to the gaseous contents of array730 (e.g., by liquid blockage of openings intended for the passage of gas or two-phase mixtures). Preferably, manifolds and piping of thearray730 are arranged so that gas and liquid (and/or two-phase mixtures of gas and liquid) may be delivered to or removed from thearray730 from a closely clustered set of surface access points (e.g., near the A corner of array730). Similar stacks of M IPV layers tipped at various angles, where M is any integer number greater than or equal to 2 and the M layers may contain varying numbers of IPVs, are contemplated and within the scope of the invention.
• FIG. 7F is a schematic representation of portions of an illustrative embodiment of the invention. Asystem732 includes or consists essentially of a field or series of pipeline segments724 (only one of which is explicitly labeled inFIG. 7F) connected into a serpentine whole by a series of U-connectors734 (only one of which is explicitly labeled inFIG. 7F). Thepipeline segments724 and U-connectors734 are of preferably but not necessarily circular cross-section. Whatever cross-sectional shape is employed in a given embodiment, thepipeline segments724 and U-connectors734 are preferably of approximately the same cross-section, both in shape and size. That is, the interior of thesystem732 has a continuous cross-section, that is, is approximately continuous in shape and dimensions. The continuous cross-section ofsystem732 is advantageous in that allows the passage of a “pig” (a device, for e.g., pipe inspection, inserted into a pipeline and traveling freely through it) that is large relative to the cross-section throughout the whole pipe field ofsystem732, e.g., from anentry point736 to anexit point738.
• FIG. 7F depicts anillustrative system732 featuring fivepipeline segments724 and fourU-connectors734, but various embodiments may contain any number of pipeline segments greater than two and any number of U-connectors greater than one. Thepipeline segments724 depicted inFIG. 7F are arranged in an accordion-like manner to minimize IPV total field width while still allowing for the required bend radius of theU connectors734. In various other embodiments, two or more, or even all, of the pipeline segments may be substantially parallel to each other.
• FIG. 8 is a schematic representation of portions of another illustrative embodiment of the invention. A recessed LUR compressed-gas storage system800 is formed in a vertical, artificial cavern orshaft802, typically but not necessarily circular in cross-section, and may be part of a larger system (not shown) for the storage and recovery of energy. Compressed air, natural gas, or other fuel or non-fuel liquids or gasses may be stored, either exclusively or in different states of operation, withinsystem800, as well as within various other LUR systems and IPVs described herein and within various embodiments not explicitly described but within the scope of the invention. As inFIGS. 1A,1B,1C, and1D, one or more LUR systems (e.g., system800) and/or IPV systems falling within the scope of the invention may be employed at a single site, or in a network of sites connected by piping, in order to store compressed air, natural gas, and/or other fluids simultaneously. Compressed air stored in individual, multiple, or networked storage systems may be utilized as an energy-storage medium by a system, e.g., an adiabatic compressed-air energy storage system or an isothermal compressed-air energy storage system, that employs no additional fuel; alternatively or additionally, compressed air so stored may be utilized in combination with natural gas or other fuels for the production of energy. For illustrative purposes, most of the energy storage and generation systems described and depicted herein are isothermal compressed-air energy systems, and the storage systems described and depicted herein are primarily lined underground reservoirs storing compressed air and heat-exchange liquid; however, this emphasis should not be taken as in any way restricting the contemplated scope of the invention.
• In various embodiments,system800 includes a storage reservoir recessed into ashaft802 in the earth and containing fluid that may be pressurized and/or thermally conditioned (e.g., heated, cooled, or maintained at an approximately constant temperature). Pressurization of the fluid stored bysystem800 enables the storage of elastic potential energy; heating or cooling of the fluid enables the storage of exergy (work available from a system in disequilibrium). Typically, although not necessarily, the fluid is thermally conditioned by heating or by maintenance at an approximately constant temperature rather than by cooling. A fluid may be both pressurized and thermally conditioned. Such pressurization and thermal conditioning may be controlled functions of time.Shaft802 may be lined with a material that prevents leakage of fluids into or out of theshaft802; the material may also act as a thermal insulator to assist in thermal conditioning or in mitigating the exchange of heat between the fluid and the surrounding earth. Alternatively or additionally,shaft802 may be lined with a material that acts primarily as a thermal insulator.
• In the illustrative embodiment depicted inFIG. 8,shaft802 is vertical and circular in cross-section.Shaft802 is sunk preferably in stable earth material, e.g., solid rock, and may be sunk by a technique and machine for sinking vertical shafts, e.g., as described in U.S. Patent Application Publication No. 2011/0139511, filed Jan. 19, 2011, and/or in U.S. Patent Application Publication No. 2012/0163919, filed Mar. 19, 2012, the entire disclosure of each of which is incorporated herein by reference. In one approach to the excavation of a shaft such asshaft802 according to embodiments of the present invention, an excavating machine breaks up rock during boring into particles that are removed from the bore hydraulically. In other embodiments of the invention, the rock is removed mechanically (e.g., by scoops). Herein, the term “rock” signifies all earth material suitable for excavation for and fabrication of a pressurized underground fluid-storage reservoir.
• As theshaft802 is sunk, a shaft liner804 (which includes or consists essentially of reinforced concrete and/or some other material) forming an interior wall of theshaft802 may be installed in a series of rings, each ring being added below previous rings as the excavating machine increases the depth of the bore by a suitable amount. The inner and/or outer surface of theshaft liner804 may be coated with one or more coatings or additional layers of material (not shown inFIG. 8): these additional layers may serve to prevent leakage of fluid into or out of theshaft802, to preserve theshaft liner804 from corrosion or degradation, to thermally insulate theshaft802 from the surrounding earth806, or more perform two or more of these functions.
• In general, a lined underground reservoir constructed within ashaft802 of larger depth and/or radius will be capable of storing more fluid and more thermal and elastic potential energy than ashaft802 of relatively small depth and/or radius.
• In various embodiments including the illustrative embodiment depicted inFIG. 8, acavity liner808 is constructed within theshaft802 lined by theshaft liner804. In this illustrative embodiment, thecavity liner808 may include or consist essentially of multiple layers, not all of which are depicted inFIG. 8: one layer is a concrete or reinforced-concrete layer810, and another layer is aninner lining812, of an impermeable (e.g., to liquid and/or gas) material such as steel or a plastic. Thecavity liner808 includes a dome portion814 that is surmounted and strengthened by a concrete or reinforced-concrete cap816. Thiscap816 may extend into the surroundingrock820 and may serve as or separately consist of a plug to distribute upward pressure forces from the dome814, in part or entirely, to the surroundingrock820 as opposed to theinfill818. Above theconcrete cap816, theshaft802 is filled to approximately surface level primarily with aninfill818 of one or more materials (e.g., rock particles removed during excavation of theshaft802, concrete, earth, water). Thecavity liner808 may be coated with one or more coatings or additional layers of material not shown inFIG. 8, interiorly and/or exteriorly, that may serve to seal, protect, or insulate thecavity liner808. Thecavity liner808 is in sufficient contact with theshaft liner804 and with theconcrete cap816 in a manner that enables forces originating with pressurized fluids within thecavity liner808 to be communicated to the surroundingrock820 and to theinfill818. The strength and weight of the surroundingrock820 and of theinfill818 bear most of the pressure load of the fluid within thecavity liner808. Preferably, the mass and/or mechanical strength of the dome814,cap816, andinfill818 are collectively capable of bearing all pressure loads exerted by the fluid contents of thesystem800, with a sufficient margin of safety beyond whatever plausible pressure to which the contents ofsystem800 may be intentionally or accidentally raised. Also, preferably, the mechanical strength of the dome814, cap86, andinfill818 are collectively capable of bearing the load of their own weight, and of any vehicles, floodwaters, or other surface loads that might be plausibly superadded above theshaft802, when the fluid contents of thesystem800 are at relatively low pressure (e.g., ambient atmospheric pressure). In short, theliner808 is generally supported in such a manner that it neither swells unacceptably or bursts when filled with high-pressure fluid, nor sags unacceptably or collapses when filled with atmospheric-pressure fluid. An “acceptable” degree of swelling or sagging ofliner808, with accompanying displacement of surroundingrock820,infill818, and other materials or components ofsystem800, is any degree of swelling or sagging that does not cause breakage or degradation of the materials or components of system800 (e.g.,liner808,inner liner812, piping826,830,834).
• The cavity liner808 (including its dome814), the load-bearing cap816, theinfill818, theshaft liner804, and the surroundingrock820 constitute a sealed recessed storage reservoir. The reservoir may include other components and materials in various other embodiments (e.g., an insulating layer within or around the cavity liner808).
• In various other embodiments, the invert (floor) and sides of thecavity liner808 may be in direct contact with the surroundingrock820; the dome814 may not be a distinct structure from theconcrete cap816; and/or a system of piping may surround thecavity liner808 in a manner that tends to drain water away from thecavity liner808. Water so diverted from thecavity liner808 may be conducted away through piping not depicted inFIG. 8. In embodiments where thesystem800 is constructed by excavation through relatively small, primarily non-vertical access tunnels, rather than through vertical shaft excavation, the dome814 may be in direct contact with the surroundingrock820,infill818 may be absent, and plugs (or “pressure barriers”) of concrete or other material may prevent loss of fluid from the recessed reservoir through the tunnels built to enable excavation of the reservoir.
• In the illustrative embodiment depicted inFIG. 8, the recessedreservoir800 contains an accumulation of a non-gaseous fluid (e.g., foam or liquid)822 and ofgas824. Thegas824 occupies the portion ofreservoir800 not occupied by thenon-gaseous fluid822. The fluid contents ofreservoir800 may be at high pressure (e.g., 3,000 psig) and relatively high temperature (e.g., 60° C.).
• Piping826 passes from the surface, through the infill818 (as shown inFIG. 8) or through the native rock820 (in various other embodiments), through the dome portion814 of liner808 (or, in various other embodiments, some portion of theshaft liner804 and/or through the side or invert of liner808) and reaches to near the bottom of theshaft802. Apump828 is capable of drawingfluid822 into piping826 and expelling the fluid822 from theshaft802. The piping826 may be enclosed by a conduit of sufficient width to enable the insertion and removal of thepump828 from within theliner808. Power, control, and data cables (not shown inFIG. 8) may also entershaft802 through piping826 or through some other conduit, enabling the control and operation ofpump828 and communication with sensors (not shown) insideshaft802 and/or vessel lining808 that provide information to operators ofreservoir800 and/or to an automatic control system on various physical variables, e.g., pressure and temperature of the fluid contents ofcavity liner808, forces acting on theliner808 orrock820, depth offluid822, and the like.
• Fluid expelled fromshaft802 bypump828 may be directed via piping826 to reservoirs, cylinders, or other components of an energy storage and recovery system (not shown). Fluid may be directed via piping830 to a spray head or nozzle (not explicitly shown), or array of spray heads and/or nozzles, for the generation of a foam ordroplet spray832 within the gas-filled portion ofliner808. The foam ordroplet spray832 may exchange heat with the fluids insideliner808. In various embodiments, fluid exiting the interior of theliner808 through piping826 is passed through pumps, valves, heat exchangers, and other devices (not shown) before being returned to the interior ofliner808 throughpiping830.Additional piping834 allows the addition to or removal from the interior ofliner808 of fluid (e.g., gas).
• In another embodiment, not shown, multiplefluid liners808 may be situated in asingle shaft802. Thefluid liners808 may be stacked one atop another, or arranged in a vertically-oriented bundle of tube-like liners, or otherwise arranged in order to enable convenient construction, spatially even distribution of forces, and/or other advantages. In some cases, multiple narrower-diameter fluid liners (e.g., capped pipes, such as one or more IPVs) may be less expensive than asingle liner808 of comparable capacity endowed with a single large, weldedinner liner812.
• FIG. 9A is a schematic diagram of portions of another illustrative embodiment of the invention. A recessed LUR compressed-gas storage system900 includes acavity902 surrounded by suitable (e.g., solid-rock) earth material. The materials that may be stored in thesystem900, and the uses to which those materials may be put, include those described forsystem800 inFIG. 8. Thecavity902 is typically but not necessarily circular in cross-section, and may be part of a larger system (not shown) for the storage and recovery of energy.
• Although the storage capacity and functions ofsystem900 may be similar to those ofsystem800 inFIG. 8, the method of construction ofsystem900 differs. Rather than excavating a vertical shaft, as forsystem800, slopingaccess tunnels904,906,908 (only partly shown inFIG. 9A) are excavated to the location ofcavity902 from points on the surface that may be many meters away from a point on the surface directly abovecavity902. Exemplary arrangements of theaccess tunnels904,906,908 are shown more fully inFIGS. 9B and 9C,FIG. 10, andFIG. 25. Thetunnels904,906,908 may be constructed by ordinary techniques for solid-rock excavation, i.e., drill, blast, and clear, and are of sufficient size to allow passage for excavating machines, workers, and rock debris. Excavation of thetunnels904,906,908 begins at one or more surface points (not shown inFIG. 9A); when thetunnels904,906,908 have reached the intended location ofcavity902, thecavity902 is excavated. Avertical shaft910 is also produced, leading from a surface point directly abovecavity902 to thecavity902. Theshaft910 may be narrow relative to (i.e., have a cross-sectional area smaller than that of) thecavity902 and produced by means of a conventional drill.
• Oncecavity902 has been excavated, it is lined with acavity liner912. In this illustrative embodiment, thecavity liner912 may include or consist essentially of multiple layers, not all of which are depicted inFIG. 9A: one layer is a concrete or reinforced-concrete layer916 and another layer is aninner liner914 of an impermeable material such as steel or a plastic. Moreover, after the construction of thecavity liner912, theaccess tunnels906,908 which open upon thecavity902, and thedrilling910, are sealed byplugs918,920,922. The plugs may include or consist essentially of concrete or reinforced concrete and may be perforated in a manner that allows pipes, wires, and conduits (not shown) to pass into the interior of thecavity902. In particular, thesystem900 may be equipped with piping and other contrivances (not shown inFIG. 9A) similar to thepiping826,830,834, pump828, and spray mechanisms shown and/or described forsystem800.
• System800 and similar embodiments may have advantages oversystem900 and similar embodiments. In particular, theaccess tunnels904,906,908 andcavity902 are, in general, excavated by workers working in situ, underground, and the lining912 of thecavity902 is typically excavated by workers working with in thecavity902. Such work may be slow, expensive, and relatively dangerous. In contrast, the widevertical shaft802 ofsystem800 may be excavated, in some instances, mostly or entirely by a machine operated from the surface, and thecavity liner808, with itsinside liner812, may be partly or entirely constructed at the surface and lowered into theshaft802. Greater speed, lower cost, and higher safety for comparable capacity may thus, in some instances, be achieved in the construction ofsystem800. Additionally,system800 does not need additional access areas and underground tunnel for access as may be required forsystem900.
• FIG. 9B is a schematic diagram of theillustrative system900 ofFIG. 9A shown in a larger geographical context. Four construction tunnels are shown inFIG. 9B, i.e.,shaft tunnel904,upper tunnel906,lower tunnel908, andaccess tunnel924. The need to move construction machinery through the tunnels places a practical limit on the steepness of all tunnels (e.g.,8 degrees of slope). This steepness limit, in combination with an assumption of linear tunneling and with the topography of the landscape above and near thecavity902, typically constrains how closely thesurface entrance926 to theaccess tunnel924 may be to the site of thecavity902. In the relatively flat illustrative geographical conditions sketched inFIG. 9B, the top of thecavity902 is approximately 114 meters vertically below the surface, the cavity is approximately 51 meters high and has a diameter of approximately 35 meters, and thetunnel entrance926 is approximately 600 meters away from thecavity902.
• In various embodiments it may be advantageous to locate theaccess tunnel entrance926 at a point closer a point on the surface directly above thecavity902.FIG. 9C is a schematic diagram of theillustrative system900 ofFIG. 9A shown in a larger geographical context that is alternative to the geographical context shown inFIG. 9B. In the context ofFIG. 9C, the surface declines relatively steeply from a point on the surface directly above thecavity902. Under these circumstances, alower tunnel908,upper tunnel906, andshaft tunnel904 may be cut from atunnel entrance926 that is closer to thecavity902 than thetunnel entrance926 inFIG. 9B. Construction of thesystem900 may be less expensive in a geological context resembling that ofFIG. 9C than in a geological context resembling that ofFIG. 9B because fewer meters of tunnel are cut in order to construct acavity902 of comparable storage capacity. However, acquisition of legal rights to access the site oftunnel entrance926, or to construction tunnels under the land between thetunnel entrance926 and a point on the surface directly above thecavity902, may still be expensive. It may therefore be advantageous to locate thetunnel entrance926 at a point directly above, or near to directly above, thecavity902.
• FIG. 10 is a schematic diagram of anillustrative LUR system1000 similar tosystem900 ofFIG. 9A,9B,9C. Acavern1002 is excavated in substantially solid rock by removal of pulverized rock through access tunnels. Amain access tunnel1004 begins at anaccess point1006 that is directly above, or substantially directly above, thecavity1002, and descends in a spiraling fashion through the rock. The steepness of themain access tunnel1004 typically never exceeds the working steepness limit for such a tunnel (e.g., 8 degrees) mandated by the need to safely pass machinery and vehicles (e.g., cement trucks). Ashaft1008 is drilled from the point on thesurface1006 to thecavity1002 to enable access to thecavity1002 by piping, electrical cables, data cables, and the like, as described above forsystem900. Access to the lower portion of theshaft1008 from the main access tunnel is obtained by excavating a first approximately horizontal tunnel1010; access to the upper portion of thecavity1002 is obtained by excavating a second approximatelyhorizontal access tunnel1012; and access to the lower portion of thecavity1002 is obtained by directing the lower portion of the spiralingmain access tunnel1004 to a point ofcontact1014 with thecavity1002. The construction of a spiraling main access tunnel may reduce difficulties associated with accessing land rights to linear access tunnels potentially located a distance away from the overhead access and surface facilities.
• Thecavity902 inFIG. 9A,FIG. 9B, andFIG. 9C andcavity1002 inFIG. 10 may be lined by a variety of methods, including as described above forsystem800 and further illustratively described hereinbelow. Also, invarious embodiments systems800,900, and/or1000 may include one or more underground chambers or cavities—e.g., a chamber located directly above the main fluid storage cavity (e.g.,cavity902 or1002) and accessed by theshaft tunnel904 or first horizontal access tunnel1010—in addition to the main fluid storage cavity. The one or more additional chambers may contain various components of a system for the storage and retrieval of energy not depicted inFIGS. 9A,9B,9C, or10, such as machinery, liquid, and/or pressurized gas. Examples of machinery that may be located within in the one or more additional chambers include systems for control (e.g., computers, control systems as detailed above), pumps, insulated pipeline vessels, and systems for the interconversion of electrical, thermal, and elastic-potential energy in compressed gas and other fluids, and/or for the combustion of fuels (e.g., natural gas). Liquid (e.g., water) located in the one or more additional chambers may constitute a storage reservoir of heat-exchange fluid to be circulated into and out of the main fluid-storage chamber for the purpose of thermally regulating the fluid stored within the main fluid-storage chamber. Alternatively or additionally, liquid located in the one or more additional chambers may constitute one or more lower or upper reservoirs enabling gravitational potential energy to be stored or released by virtue of an altitude difference between the one or more reservoirs and some other location (e.g., the earth's surface or another chamber at greater depth).
• FIG. 11 is a schematic representation of three stages in one method of construction of avertical shaft1100, similar toshaft802 inFIG. 8, sunk into stable earth material1102 (preferably, solid rock). Withinshaft1100, a recessed storage reservoir such as that depicted inFIG. 8,FIG. 9A,FIG. 9B,FIG. 9C, orFIG. 10, may be constructed. Stage A (upper drawing inFIG. 11) is a stage at which anincipient shaft1100 of depth D1 is already in progress. Drillings (narrow shafts)1104 are sunk into the invert of theincipient shaft1100 to a depth of approximately D2. The number ofdrillings1104 shown inFIG. 11 is illustrative only. Explosives (e.g., dynamite) are inserted into thedrillings1104 and detonated, creating a pulverized mass ofrock1106. A single mass of pulverizedrock1106 is shown in Stage B inFIG. 11, but in practice only portions of the invert ofshaft1100 may be pulverized in any given blasting operation. The pulverizedrock1106 is removed (e.g., by buckets or as a slurry), creating anew vacancy1108 that extends theshaft1100 deeper into therock1102, as shown in Stage C inFIG. 11. As of Stage C, theshaft1100 has attained a depth of D3=D2+D1. A shaft of any width may be sunk to any depth by these means, subject to the stability of theshaft1100 thus created. The walls of theshaft1100 may be segmentally covered (e.g., by rings or panels) and strengthened by a liner (not shown) as theshaft1100 is incrementally deepened.
• The method of shaft-sinking depicted inFIG. 11 may be time-consuming and expensive, since workers typically descend to the bottom of theshaft1100 to operate machinery to produce thedrillings1104, insert explosives, and operate machinery that removes thedebris1106. Another method of shaft-sinking is depicted inFIG. 12A andFIG. 12B. This method of shaft-sinking may entail less time-consuming and possibly hazardous descent by workers into the developing shaft.
• FIGS. 12A and 12B are schematic diagrams of a shaft-sinkingsystem1200 utilized in various embodiments of the present invention. Herein, such a system is termed a “roadheader shaft sinking system” or simply “roadheader system.” Thesystem1200 includes asupport rig1202 erected over the opening of a shaft1204 (which may have a depth of zero when the process of excavation begins). A platform orstage1206 descends by weight-bearing cables1208 from thesupport rig1202. Thesupport rig1202 is capable of raising or lowering thestage1206 and all components attached thereto, e.g., by means of motor-driven cable drums (not depicted). To the bottom of thestage1206 is attached amechanical housing1210, which typically contains motors, reservoirs of fluid, cameras, and/or other components. Adjustable-length cables and conduits for the conveyance of electrical power, control signals, fluids, and other services to and from thestage1206 components attached thereto are not shown inFIG. 12A but may extend, like the weight-bearing cables1208, from thesupport rig1202 into theshaft1204. To the bottom of thehousing1210 is attached a controllable joint1212 which supports and moves atelescoping boom1214. The joint1212 is capable of directing theboom1214 through the entire hemisphere of action not occluded by the housing1210 (i.e., a solid angle of approximately 2π steradians). At the end of thetelescoping boom1214 is arotating cutting head1216. As used herein, the term “roadheader” includes any drilling system featuring a directable boom surmounted by a cutting head. Thestage1206 and all components attached thereto are herein termed the “roadheader rig.” The roadheader rig is raised and lowered by thesupport rig1202.
• The joint1212 is capable of raising, lowering, and rotating theboom1214; theboom1214 may extend and retract. By appropriately combining (e.g., under the direction of a human operator, automatic control system, or both) the motions of thestage1206, joint1212, andboom1214, the working surface of the cuttinghead1216 may be brought into contact with any point on the walls or invert of theshaft1204.
• Rock fragments broken from the walls and/or invert of theshaft1204 by the cuttinghead1216 typically accumulate asdebris1218 upon the invert of theshaft1204. Such debris may be removed by a variety of techniques. Theillustrative system1200 introduces water through piping (not shown) that mixes with thedebris1218 to form a slurry. Alternatively, theshaft1204 may be wholly or partly filled with water during operation of thesystem1200. Theslurrified debris1218, whether its water portion is introduced through piping or through filling of theshaft1204 with water, is pumped through apipe1220 to the surface. (Two portions ofpipe1220 are depicted inFIGS. 12A and 12B.)
• InFIG. 12B, thesystem1200 is shown in a state of operation different from that depicted inFIG. 12A. InFIG. 12B, thedebris1218 is not depicted and thecutting head1216 has been maneuvered into a position that displays the working face of the cuttinghead1216 and is suitable for removing rock from the face of the invert.
• It is clear that by lowering the roadheader rig, breaking up rock with the cutting head, and removing debris from theshaft1204, theshaft1204 may be sunk to any depth to which thesupport rig1202 is capable of lowering the roadheader rig and at which the walls of theshaft1204 remain stable. The walls of theshaft1200 may be segmentally covered and strengthened by a liner (not shown) as theshaft1200 is incrementally deepened. Withinshaft1200, a recessed storage reservoir such as that depicted inFIG. 8,FIG. 9A,FIG. 9B,FIG. 9C, orFIG. 10, may be constructed, constituting a lined underground reservoir.
• FIG. 13 is a schematic representation of an illustrative lined underground reservoir fluid-storage system1300 that includes a lined cavity1302 (dashed lines) similar tocavity902 inFIG. 9. In general, it is desirable that water be controlled during excavation and construction of the linedcavity1302. In other instances, it may be useful to reduce water collecting or impinging on the exterior of the lining (not shown) of thecavity1302. In some instances, water may accelerate the corrosion or cracking of the various component layers of a lining; moreover, if a cold liquid (e.g., liquefied natural gas) is stored in thesystem1300, or the gaseous pressure of the contents of thecavity1302 is lowered rapidly to a sufficient degree without thermal conditioning of the contents, freezing temperatures may occur within and in the vicinity of thecavity1302, and ice expansion may cause cracking of the lining and other damage. Therefore,system1300 includes a network ofpipes1304 that surrounds thecavity1302. The crisscrossing lines superimposed over thecavity1302 inFIG. 13 are a two-dimensional representation of a three-dimensional network or basket of interconnectingpipes1304 surrounding thecavity1302. The pipes are tilted, perforated, and/or interconnected in a manner that permits water to enter the pipes and be drained downward to acollection point1306. Acollection pipe1308 conducts water from thecollection point1306 to adisposal point1310 on the surface. A pump or pumps (not shown) impel the water through thecollection pipe1308. Air from the surface is permitted to enter thedrainage network1304 through ashaft1312 in order to equalize pressure within thedrainage network1304 as water is pumped out through thecollection pipe1308. In various other embodiments, the arrangement of pipes in thedrainage network1304 differs from that schematically represented inFIG. 13; water collected by thedrainage network1304 is directed to more than onecollection point1306; thecollection pipe1308 may be a part of, or located within, thedrainage network1304; and/or thecollection pipe1308 may reach the surface through thesame shaft1312 that admits air to thedrainage network1304 rather than through a separate shaft as depicted inFIG. 13. Also in various other embodiments, fluids for storage in and retrieval from thecavity1302, fluids for thermal conditioning of the contents ofcavity1302, control cables (not shown), air entering thedrainage network1304, water leaving thedrainage network1304, and other fluids and components ofsystem1300 may pass through a multiplicity of conduits located within asingle shaft1312 and/or may pass through a multiplicity of shafts (not shown inFIG. 13). This drainage system may be applied to vertically-excavated LURs such as those described with reference toFIG. 8. Thisdrainage network1304, after initial usage during excavation and construction, may subsequently be repurposed and used to monitor and detect any incidents of gas leakage from the LUR. Especially in storage of potentially hazardous or explosive fluids, the repurposeddrainage network1304 may serve as a useful safety system for detection, collection, and evacuation of gas leakage. For example, the air and/or liquid (e.g., water) within thedrainage network1304 may be monitored (e.g., via a conventional gas monitor) for the presence of and/or elevated levels of the gas contained within the LUR (e.g., natural gas), which may signify leakage from the LUR. In the event of such leakage, thedrainage network1304 may be used as a conduit to remove (e.g., with a pump connected thereto) and potentially recover all or a fraction of the leaking gas from underground, thereby mitigating contamination and/or unsafe conditions.
• FIG. 14A is a cross-sectional schematic representation of portions of anillustrative lining1400 of a linedunderground reservoir1402. The lower portion ofFIG. 14A shows a portion of the lining1400 of the linedunderground reservoir1402 in cross-section; the upper portion ofFIG. 14A is a magnified and rotated view of a small portion of thelining1400, as indicated by dashedlines1404.Raw rock mass1406 presents a relatively rough surface exposed by excavation. In one method of construction of thelining1400, a network of water-drainage pipes1408 similar to that depicted inFIG. 13 is placed against the surface of therock mass1406. Thedrainage pipes1408 are covered with a layer ofshotcrete1410, i.e., spray-on concrete. Theshotcrete1410 may be porous to allow water to flow through it and into the drainage pipes. Theshotcrete1410 serves both to stabilize thedrainage pipes1408 and to protect them from displacement or damage during pouring and/or injection of the next most inward layer, namely, aconcrete layer1412. Theconcrete layer1412 may be self-compacting and may be agitated during or after pouring in order to remove void spaces and promote uniform density. Within theconcrete layer1412 is embedded a metal (e.g., steel reinforcement)mesh1414, one purpose of which shall be explained below with reference toFIGS. 15A and 15B. The inward surface of theconcrete layer1412 is comparatively smooth, and is shaped to form acavity1416. Thecavity1416 is lined with an impermeable liner1418 (e.g., a liner including or consisting essentially of steel). Between theimpermeable liner1418 and the inward face of the concrete1412 is a viscous or sliding layer1420 (e.g., a layer of asphalt, a layer of plastic), herein termed “the viscous layer.” Theviscous layer1420 enables slippage between theimpermeable liner1418 and theconcrete layer1412, mitigating the buildup of forces (e.g., tensile forces) that could cause strain (e.g., stretching) in the material ofimpermeable liner1418 and which could thus damage theimpermeable liner1418. Theviscous layer1420 may also serve to mitigate corrosion of theimpermeable liner1418.
• FIG. 14B is a schematic cutaway drawing of a portion of thelining1400 inFIG. 14A. Therock face1406,drainage pipes1408,concrete layer1412,mesh1414,viscous layer1420, andimpermeable liner1418 are depicted. Theshotcrete layer1410 is not depicted inFIG. 14B for clarity. Primary (rock-mass) cracks1422, secondary (concrete) cracks1424, and tertiary (concrete) cracks1426 are depicted inFIG. 14B. Rock-mass cracks1422 tend to propagate outward (i.e., away fromcavity1416,FIG. 14A) from the face of therock mass1406.Secondary cracks1424 tend to propagate inward into the concrete1414 from the face of therock mass1406. Upon reaching themesh1414, thesecondary cracks1424 tend to propagate still further inward as smaller, more numeroustertiary cracks1426. The effect of themesh1414 is thus to increase the number of, while decreasing the size of, the cracks that impinge upon theviscous layer1420 andimpermeable layer1418. This pattern of cracking tends, for a given degree of expansion of thecavity1416, to decrease the magnitude of forces (e.g., tensile forces) exerted upon various local portions of theimpermeable lining1418. Decreasing the forces (e.g., tensile forces) exerted locally within the impermeable lining1418 (e.g., during repeated pressurizations of the cavity1416) tends to preserve the lining1418 from damage and to increase its longevity.
• The network of drainage pipes within thelining1400 may be used to pump water out of the shaft during construction. Various illustrative methods of construction of thelining1400 are considered further inFIGS. 17-23.
• FIGS. 15A and 15B are schematic representations of aspects of the behavior of cracks and other components of a linedunderground reservoir1500 having a lining similar to that portrayed inFIG. 14A andFIG. 14B when the contents of the linedunderground reservoir1500 are raised to a relatively high pressure (e.g., 3,000 psi). In general, arock mass1502 surrounding acavity1504 is not perfectly rigid. Rather, under the influence of pressure forces exerted by the fluid contents of thecavity1504, therock mass1502 in the vicinity of thecavity1504 will tend to be displaced outward slightly from its original, pre-pressurization position. As a result of this outward displacement, therock mass1502 tends to develop radiating cracks1506 (primarily by opening existing cracks that are frequent in blocky crystalline bedrock), i.e., cracks that tend to (a) impinge edgewise upon the cavity1504 (b) be widest at their point of impingement upon thecavity1504, and (c) narrow as they proceed away from thecavity1504.
• FIG. 15A portrays a first state in which thecavity1504 has hitherto contained fluid only at relatively low pressure (e.g., atmospheric) and has diameter D1.Lines1510 in the upper portion ofFIG. 15 show existing closed cracks in therock mass1502 when the contents ofcavity1504 are sufficiently pressurized. Aconcrete liner1512 surrounds thecavity1504 and is, in the unstressed initial condition portrayed inFIG. 15A, uncracked.
• FIG. 15B portrays a second state in which the contents ofcavity1504 have been raised to relatively high pressure (e.g., 3,000 psi) andcavity1504 has expanded to diameter D2.Cracks1506 have opened up in therock mass1502. The rock-mass cracks1506 give rise tosecondary cracks1514 that tend to propagate into theconcrete layer1512 from the face of therock body1502. In various embodiments where a mesh is embedded in theconcrete layer1512, as in the illustrative embodiment depicted inFIGS. 14A andFIG. 14B, the secondaryconcrete cracks1514, upon propagating inward to the mesh, will give rise to tertiary concrete cracks as depicted inFIG. 14B, distributing forces (e.g., tensile forces) less unevenly across the surface of theimpermeable liner1508.
• The storage of relatively hot (e.g., 60° C. or higher) pressurized fluid within a lined underground reservoir (e.g.,cavern1402 inFIGS. 14A and 14B, orcavern1500 inFIGS. 15A and 15B) as is contemplated in various embodiments of the present invention, tends to decrease forces (e.g., tensile forces) exerted locally within the impermeable lining (e.g., lining1508 inFIGS. 15A and 15B) if theimpermeable lining1508 is constructed of a material (e.g., steel) that expands at higher temperatures. That is, as regards forces (e.g., tensile forces) exerted within theimpermeable lining1508, the effects of increasing the pressure of the fluid contents of linedunderground reservoir1500 tend to be counteracted by the effects of increasing the temperature of the fluid contents of linedunderground reservoir1500.
• FIG. 16 is a plot of illustrative data showing the relationship between cyclic pressure within a lined underground reservoir (horizontal axis) and the strain or deformation in an illustrative steel liner of the lined underground reservoir (vertical axis), for three hypothetical cycles of temperature of the contents of the lined underground reservoir. In a first hypothetical temperature-pressure cycle1602, the contents of the reservoir, and thus the lining, which is in contact with the contents, remain at a constant temperature as the pressure within the reservoir is raised from alow pressure1604 to ahigh pressure1606 and then lowered to thelow pressure1604 again. (The relationship between temperature and pressure of the contents is not depicted explicitly inFIG. 16.) The strain undergone by the steel liner over thefirst cycle1602 varies over a range R1.
• In a second hypothetical temperature-pressure cycle1608, the contents of the reservoir, and thus the lining in contact with the contents, vary moderately in temperature as the pressure of the contents changes from alow pressure1604 to ahigh pressure1606 and then back to thelow pressure1604 again: i.e., the temperature increases with increasing pressure and decreases with decreasing pressure. The strain undergone by the steel liner over thesecond cycle1608 varies over a range R2 that is significantly smaller than the stress range R1 of thefirst cycle1602, and the peak strain undergone by the steel liner forcycle1608 is less than that undergone forcycle1602.
• In a third hypothetical temperature-pressure cycle1610, the contents of the reservoir, and thus the lining, vary more widely than incycle1608 as the pressure within the reservoir is raised from alow pressure1604 to ahigh pressure1606 and then lowered to thelow pressure1604 again: i.e., the temperature increases with increasing pressure and decreases with decreasing pressure. The strain undergone by the steel liner over thesecond cycle1608 varies over a range R3 which is smaller than the range R1 and larger than the range R2; moreover, the sense or sign of the relationship between strain and pressure/temperature has been reversed from that ofcycle1602 andcycle1608, that is, the liner experiences less strain atpeak pressure1606 and temperature than atlowest pressure1604 and temperature. Different relationships between temperature, pressure, and strain than those shown inFIG. 16 may pertain for various steels, or for materials other than steel, or for multilayered liners. In general, a temperature-pressure-strain relationship that entails the lowest maximum strain on the liner—e.g.,cycle1608 in FIG.16—is preferable.
• Illustrative methods of constructing portions of a lined underground reservoir in various embodiments of the present invention are now considered.FIG. 17 is a schematic cross-sectional representation of three stages (Stage A, Stage B, and Stage C) in the construction of an illustrative linedunderground reservoir1700 similar toreservoir900 inFIG. 9.Cavern1700 is constructed by excavating acavity1702 primarily by removing rock fragments throughaccess tunnels1704,1706, and1708. In Stage A, a network of drainage pipes (not shown) similar tonetwork1408 inFIG. 14A has been placed against the interior rock mass and covered with a layer of shotcrete (not shown) similar tolayer1410 inFIG. 14A. In Stage A, asteel invert liner1710 conforming in shape to the invert of thecavity1702 has been constructed and is held above the rock face of the invert by spacers (not shown). Trucks (e.g., truck1712) bring concrete to the worksite through thelower access tunnel1708 and pour and/or inject concrete1714 into the space between theinvert liner1700 and the rock face below. In order to prevent the concrete1714 from deforming or floating theinvert liner1710,water1716 may be added to the interior ofinvert liner1710 through piping (not shown) as the concrete1714 is poured. At Stage A, theinvert liner1710 is approximately filled with water and the concrete1714 between theinvert liner1710 and the rock face is almost completely poured.
• After the concrete1714 hardens, firmly undergirding theinvert liner1700, thewater1716 is removed from theinvert liner1710. Asteel liner dome1718 is then constructed atop the invert liner1710 (Stage B). Thedome1718 may be jacked up or otherwise raised incrementally as sections of wall-lining material1720 are assembled (e.g., by welding) intorings1722 beneath thedome1718. In this manner, thesteel liner dome1718 is raised until it is close to the domed ceiling of thecavity1702, at which point an approximately cylindrical set ofrings1722 has been fabricated thereunder.
• At Stage C, a completeinner steel liner1724 has been constructed within thecavity1702. Trucks (e.g., truck1726) bring concrete to the worksite through themiddle access tunnel1706 and pour and/or inject additional concrete1728 into the space between theliner1724 and the surrounding rock face. Some of the concrete1728 forms aplug1730 in the lower access tunnel. Water within theliner1724 prevents theliner1724 from being deformed by the weight of the concrete1728.
• After Stage C, in phases of construction not depicted inFIG. 17, concrete may be added through atop shaft1732 to fill the space between the water-filledliner1724 and the rock face at and above the level of themiddle access tunnel1706.Middle access tunnel1706 is plugged with concrete during the addition of the concrete, and finally thetop shaft1732 is plugged with concrete. Other phases of construction, including the addition of pumps, piping, sensors, power cables, and other components, are not portrayed inFIG. 17 or discussed herein but are contemplated.
• When the linedunderground reservoir1700 has been completed, the water within theliner1724 may be used to pressure-test theliner1724. After completed testing, the water is removed by injection of the stored product, e.g., compressed air. This procedure ensures the stability of the storage, as there is always an internal overpressure from the water and/or the stored product.
• FIG. 18 is a schematic cross-sectional representation of three stages (Stage A, Stage B, and Stage C) in the construction of an illustrative linedunderground reservoir1800 similar toreservoir800 inFIG. 8.Cavern1800 is constructed partly by excavating anopen shaft1802 in suitable rock; a lined reservoir is produced in theshaft1802 primarily by assembling portions of an impermeable (e.g., including or consisting essentially of steel) liner at or near the surface of the earth and lowering them down the shaft by means of asupport rig1804 and then surrounding the resultingliner1806 with concrete1808 (Stage C) and other materials. In Stage A, aninvert liner1810 has already been placed at the bottom of theshaft1802. Theinvert liner1810 may be undergirded by concrete1812 by means similar to those depicted for undergirding of theinvert liner1710 inFIG. 17; alternatively, the undergirding concrete1812 may be formed in situ, prior to the emplacement of theinvert liner1710, which may be lowered into the undergirding concrete1812. In either case, after emplacement of theinvert liner1710, the cylindrical or wall-lining portion of theliner1806 is constructed by constructing or staging rings, panels, or othersegmental portions1814 of theliner1806 at or near the surface and then lowering them down theshaft1802 by means ofsupport rig1804. Thesegments1814 may be joined together (e.g., welded together) in situ upon being lowered into theshaft1802. A network of drainage pipes (not shown inFIG. 18) and other lining layers similar to those depicted inFIG. 14A andFIG. 14B may be emplaced simultaneously with thesegmental portions1814 of theliner1806.
• In Stage B, the wall-lining portions of theliner1806 have all been emplaced, and adome liner1816 is being lowered into theshaft1802. Following emplacement of thedome liner1816, a concrete liner orsurround1808 may be poured and/or injected into the space between theliner1806 and the surrounding rock, as depicted inFIG. 17. Thissurround1808 may additionally include a plug (not shown) that may extend into the surrounding rock and may serve as or separately consist of a plug to distribute upward pressure forces from thedome1816, in part or entirely, to the surrounding rock as opposed to theoverfill1818.
• In Stage C, theconcrete liner1808 has been emplaced, overfill1818 (e.g., crushed rock; concrete; reinforced concrete) has been emplaced, and at least three conduits orpipes1820,1822, and1824 have been emplaced to enable fluid communication (and, in various embodiments, electrical, informatic, and mechanical communication) between the interior of the linedunderground reservoir1800 and facilities (not shown) on the surface. Gas may be injected into or removed from thereservoir1800 throughpipe1820, heat-exchange fluid (e.g., liquid, foam; not shown inFIG. 18) may be injected into thereservoir1800 through pipe1822 in order to thermal condition the contents of thereservoir1800, and heat-exchange fluid may be removed from thereservoir1800 throughpipe1824.
• The method of construction depicted inFIG. 18 typically requires that most assembly (e.g., joining ofsegmental portions1814 to the liner)1806 is done by workers in situ, deep within theshaft1802. It is in general desirable that as little work as possible be performed at depth, in order to increase worker safety and to decrease costs.
• FIG. 19 is a schematic cross-sectional representation of five stages (Stage A, Stage B, Stage C, Stage D, and Stage E) in the construction of an illustrative linedunderground reservoir1900 similar toreservoir800 inFIG. 8.Cavern1900 is constructed partly by excavating anopen shaft1902 in suitable rock; a lined cavity may be produced in theshaft1902 primarily by assembling portions of an impermeable (e.g., steel)liner1904 at or near the surface of the earth and floating theliner1904 upon a body of water1904 (or other liquid) that may be raised or lowered by the addition or removal of water. The method of construction depicted inFIG. 19 typically requires the performance of less construction work within theopen shaft1902 than does the method of construction depicted inFIG. 18. In Stage A, a partial concrete lining withdrainage system1908 has been constructed within theshaft1902 and a body ofwater1906 mostly fills theshaft1902. Aninvert liner1910 and asegmental portion1912 of theliner1904 have been assembled proximate the surface and are floating upon the body ofwater1906. As utilized herein, “proximate the surface” is defined as at or near the surface (i.e., within reach of a worker or work crew at the surface or on work surfaces (e.g., scaffolding) near the surface).
• In Stage B, furthersegmental portions1914 have been joined to theliner1904. The depth of the body ofwater1906 has been lowered in order to keep the level at which furthersegmental portions1914 are added to theliner1904 at or near the surface.
• In Stage C, theliner1904 has been completed and rests in the prefabricated undergirdingconcrete liner1908.
• In Stage D, additional concrete1916 has been added to cover, protect, and strengthen adome liner1918, and at least three conduits orpipes1920,1922, and1924 have been emplaced to enable fluid communication (and, in various embodiments, electrical, informatic, and mechanical communication) between the linedunderground reservoir1900 and facilities (not shown) on the surface. Gas may be injected into or removed from thereservoir1900 throughpipe1920, heat-exchange fluid (e.g., liquid, foam; not shown inFIG. 19) may be injected into thereservoir1900 throughpipe1922 in order to thermal condition the contents of thereservoir1900, and heat-exchange fluid may be removed from thereservoir1900 throughpipe1924. The additional concrete1916 may additionally include a plug (not shown) that may extend into the surrounding rock and may serve as or separately consist of a plug to distribute upward pressure forces from thedome1918, in part or entirely, to the surrounding rock as opposed to theoverfill1926.
• In Stage E, overfill1926 (e.g., crushed rock; concrete; reinforced concrete) has been added above the concrete1916. The weight and/or mechanical strength of theoverfill1916 serve to restrain expansion of the linedunderground reservoir1900 when thereservoir1900 is filled with fluid at high pressure.
• The method of construction partly depicted inFIG. 19 dispenses with thesupport rig1804 inFIG. 18 and allows a greater amount of construction work to be performed at or near the surface of the earth. In various other embodiments, a method of construction similar to that depicted inFIG. 19 is employed, but no prefabricated concrete undergirding1908 is constructed. Rather, theliner1904 is lowered into place as it is constructed, coming to rest upon spacers (e.g., beams, ribs, struts) that hold the liner a desired distance away from the surrounding rock face at all points. Concrete is then poured and/or injected into the space between theliner1904 and the surrounding rock face, approximately as described for the emplacement of theconcrete liner1728 inFIG. 17, producing a result similar to Stage C inFIG. 18. Construction may then proceed as described for the method of construction partly depicted inFIG. 18.
• FIG. 20 is a cross-sectional schematic representation of two stages (Stage A and Stage B) of the first stages of construction of an illustrative linedunderground reservoir2000 similar toreservoir800 inFIG. 8, in accordance with various embodiments of the present invention.Cavern2000 is constructed partly by excavating anopen shaft2002 in suitable rock. Similar toFIG. 19, a lined cavity is produced in theshaft2002 primarily by assembling portions of an impermeable (e.g., including or consisting essentially of steel) liner2004 (see Stage B,FIG. 20) at or near the surface of the earth and floating theliner2004 upon a body of water2006 (see Stage B,FIG. 20) that may be raised or lowered by the addition or removal of water. In Stage A, adrainage layer2008 has been constructed within theshaft2002. Thedrainage layer2008 includes a network ofpipes2010 similar to the network ofpipes1408 depicted inFIG. 14A andFIG. 14B. Thepipe network2010 is covered with a layer of shotcrete to stabilize and protect thepipe network2010. One ormore openings2012 allow water to flow from the interior of theshaft2002 into thepipe network2010, or from thepipe network2010 into the interior of theshaft2002. One or more pipes and pumps (not shown) allow water to be pumped from and to thedrainage network2010.Openings2012 may be closed (e.g., filled with concrete) or left open after or during Stage B.
• In Stage B, a body of water2006 mostly fills theshaft2002. An invert liner (e.g., dome shaped liner)2020 and asegmental portion2018 of theliner2004 have been assembled at or near the surface and are floating upon the body of water2006. One or more spacers2014 (e.g., beams, ribs, struts) that can hold the liner2004 a desired distance away from the surrounding rock face at all points are attached to the outside of theliner2004. Also, a network or basket of rebar2016 has been constructed around and attached to the portion of theliner2004 constructed as of Stage B. As further segmental portions ofsteel liner2018 and rebar network2016 of theliner2004 are added to theliner2004, water may be removed from theshaft2002 through thepipe network2010, lowering the level of the body of water2006 and thus permitting the joining of furthersegmental portions2018 and portions of network2016 to theliner2004 to proceed at or near the surface of the earth. When theliner2004 is completed, it may be lowered to the bottom of theshaft2002 by the removal of all water from theshaft2002. Concrete is then poured and/or injected into the space between theliner2004 and the surrounding rock face, approximately as described for the emplacement of theconcrete liner1728 inFIG. 17, producing a result similar to Stage C inFIG. 18. This concrete may also fill anyopenings2012. Construction may then proceed as described for the method of construction partly depicted inFIG. 18. In other embodiments, water (or other liquid) is not utilized, and the weight of the liner is supported in part or entirely by other means, such as via hydraulic jack or crane. In yet other embodiments, at least a portion of theliner2004 is assembled directly on thedrainage layer2008 after lower portion(s) of the liner2004 (if any) have been assembled and/or lowered down to the bottom of theshaft2002.
• FIG. 21A is a cross-sectional schematic representation in two stages (Stage A and Stage B) of yet another exemplary method of construction of an illustrative linedunderground reservoir2000 similar toreservoir800 inFIG. 8.Cavern2100 is constructed partly by excavating anopen shaft2102 in suitable rock; a lined cavity is produced in theshaft2102 primarily by assembling segments of an impermeable (e.g., including or consisting essentially of steel) liner2104 (see Stage B,FIG. 20) proximate (at or near) the surface of the earth and floating theliner2104 upon a body of water2106 (see Stage B,FIG. 21A) that may be raised or lowered by the addition or removal of water as theliner2004 grows. In Stage A, theshaft2102 is partially sunk. In Stage B, theliner2104 has been partially constructed in a segmented manner and is being lowered into theshaft2102 by removal of water from theshaft2102.
• FIG. 21B is a cross-sectional schematic representation of two further stages (Stage C and Stage D) of the method of construction of the illustrative linedunderground reservoir2100 represented inFIG. 21A. In Stage C, thesteel liner2104 has been completely constructed and lowered to near the bottom of theshaft2012. Spacers (not shown) preserve a desired amount of space between theliner2104 and the surrounding rock face. In Stage C, concrete2108 from asurface source2110 is being poured and/or injected into the space between theliner2104 and the surrounding rock face whilewater2112 is added to the interior of theliner2104 to balance the pressure of the rising concrete2108, thus preventing excessive deformation of theliner2104. In Stage D, theliner2104 has been completely surrounded by aconcrete layer2108, is filled withwater2112, and is being surmounted by aconcrete plug2114 that is shaped to contain upward-acting forces generated by the pressurized fluid contents ofreservoir2100 in various states of operation. Theplug2114 is shaped in such a manner as to resist relative movement with respect to the surrounding rock when exposed to low- or high-pressure forces. Theplug2114 is typically disc shaped (e.g., a shallow cylinder) to fill theshaft2102 with one or more extensions (e.g., a rim) extending into a cutout in the surrounding rock. Theplug2114 will typically extend into a cutout region of surrounding rock face, where the cutout region of rock serves in part as a lip against which the pressure and other (e.g., gravity) forces may be transmitted to the bulk surrounding rock. The cutout may be a triangular, curved, or otherwise shaped to allow a similarly shapedplug2114 to be constructed within or inserted. Theplug2114 may include a manhole (not shown) or other small access apparatus to allow access to the lower cavity andliner2104. In other embodiments, theplug2114 is solid and permanent when installed, except holes for access pipes and thus no easy access to the lower cavity orliner2104 remains after construction of theplug2114. The plug may include or consist essentially of reinforced concrete or other materials such as steel. One ormore conduits2118 permits communication (e.g., fluid, mechanical, informatic, electrical) between the interior of thelining2104 and installations (not shown) on the surface.
• FIG. 21C is a cross-sectional schematic representation of two further stages (Stage E and Stage F) of the method of construction of the illustrative linedunderground reservoir2100 represented inFIG. 21A. In Stage E, infill material2120 (e.g., crushed rock, concrete, reinforced concrete) has placed above theplug2114. In various embodiments, at least a portion of the space occupied byinfill material2120 inFIG. 21C may be utilized for storage of water (or other heat-transfer liquid) or equipment utilized in the construction, maintenance, and/or operation ofLUR2100. In Stage F, piping2122 has been inserted through theconduit2118 into the interior of thesteel liner2104 and awellhead2124 has been installed for connection to surface facilities (not shown). Piping2122 reaches approximately to the bottom ofvessel2104, enabling the extraction of approximately all settled fluid (e.g., liquid) from the interior of theliner2104. In other stages of construction of the linedunderground reservoir2100, other components, not shown, may be added, including piping for the introduction and extraction of fluids, pumps, wiring for power and telemetry, spray heads, and other components.
• FIG. 21D is a cross-sectional schematic representation of Stage F (also represented inFIG. 21C) of the method of construction of the illustrative linedunderground reservoir2100 represented inFIG. 21A. InFIG. 21D, illustrative dimensions are indicated for some of the components of linedunderground reservoir2100. Theshaft2102, from the top of thewellhead2124 to the bottom, is 11 meters in diameter and 153 meters deep. The inner liner2104 (steel-lined portion of the reservoir2100) is 100 meters high and 10 meters in diameter, with a volume of approximately 7,592 m³.FIG. 21D also provides a magnified view of a portion of the layers of the linedunderground reservoir2100, with illustrative approximate dimensions for these layers: i.e., from the inmost layer to the outermost, (1) steel liner2104 (8 mm thick), viscous or sliding layer2126 (6 mm thick), concrete layer2108 (455 mm thick), shotcrete layer2128 (30 mm thick), and rock face2130 (500 mm distant from inner surface of steel liner2104: thickness of rock, indefinite). Embedded within theconcrete layer2108 is ametal mesh layer2132. Embedded within theshotcrete layer2128 is adrainage pipe network2134. The layers depicted inFIG. 21D, and their functions, are similar to those depicted inFIGS. 14A and 14B. Other sets of layers, which may include layers not depicted herein (e.g., an insulation layer), and/or the omission of layers depicted herein, are contemplated in various other embodiments of the invention.
• The construction of cavity liners for lined underground reservoirs—e.g., the multi-layered liner depicted inFIG. 14A,FIG. 14B, and FIG.21D—may proceed by a variety of means. Aspects of one illustrative technique of liner construction are depicted inFIG. 22 andFIG. 23.
• FIG. 22 is a cross-sectional schematic representation of the assembly of a ring-shaped segmental portion2202 (e.g.,segmental portion1814 inFIG. 18) of a cavity liner.Preformed panels2204, possibly manufactured at a distant location, include or consist essentially of concrete; embedded in the concrete is a metal-mesh orrebar frame2206. Therebar frame2206 typically protrudes beyond the edge-surfaces of eachpanel2204. By arranging thepanels2204 in a circle2208 and welding the rebar frames2206 together,panels2204 may be joined into a ring-shapedsegmental portion2202. The gaps betweenpanels2210 may be filled with concrete or otherwise grouted. The panels may be installed within an open shaft iteratively during shaft construction or installed after shaft construction. Alternatively, a fully completely ring-shapedsegmental portion2202 may be lowered into an open shaft such asshaft1100 inFIG. 11. Adjacent ring-shapedsegmental portions2202 may be joined by rebar welding and gap grouting, just as thepanels2204 are joined to make each ring-shapedsegment2202.
• In other embodiments, not shown, a cavity liner (e.g., a reinforced concrete base lining) may be constructed by using slip-form casting, in which concrete is poured into a continuously moving form. This may be very efficient for a long vertical shaft and produces a very smooth surface on which may be installed the impermeable lining.
• FIG. 23 is a cross-sectional schematic representation of stages of an illustrative method of emplacing segmental portions of a cavity liner in an open shaft. In Stage A, excavation of ashaft2300 has been commenced in a setting where it is desirable to stabilize the walls of theshaft2300 as it is deepened. When theshaft2300 is deep enough to accommodate a ring-shaped segmental portion (“segment”)2302 of lining,panels2304 similar topanel2204 inFIG. 22 are lowered into theshaft2300 and assembled into asegment2302. In Stage B, theshaft2300 has been deepened sufficiently to allow the emplacement of asecond segment2306. In Stage C, theshaft2300 has been deepened sufficiently to allow the emplacement of athird segment2308. In Stage D,shaft2300 has reached its desired final depth and aninvert liner2310 has been constructed (e.g., by conventional concrete forming or by segmented assembly). In Stage E, an impermeable liner2312 (e.g. one including or consisting essentially of metal and/or plastic) has been emplaced in theshaft2300. Theimpermeable liner2312 may be emplaced by the method of segmental assembly depicted inFIG. 18 or by other methods such as direct attachment to thecavity liner2304,2306,2308,2310. Because theimpermeable liner2312 may be attached to the cavity liner, it does not need to support its own weight as inFIG. 14 andFIG. 18, thus the liner may consist of a thin steel sheet (e.g. stainless steel sheet metal) or of a plastic (e.g., one or more polymeric materials) liner connected (e.g., welded and/or bonded) together to be impermeable to gas. In fact, theliner2312 may not be “self-supporting,” i.e., the liner, being supported by other materials (e.g., the cavity liner) during assembly, may be of insufficient thickness and/or strength to support itself in the absence of such support material(s). Thus, in the absence of such materials, the assembled liner would, at least to some extent, lose structural stability due to the force of its own weight.
• Plastic liners may include or consist essentially of pre-manufactured sheets or plates of polymer material (e.g., approximately 10 mm thick) that are welded or melted together in situ to form a liner, or of liners constructed in situ by spraying or painting, or by other means (e.g., in situ inflation and emplacement of a liner manufactured elsewhere). Pre-manufactured sheet-type polymer liners may include or consist essentially of thermoplastics such as polypropylene and high-density polyethylene. Spray-on liners may include or consist essentially of thermosetting plastics such as epoxy and polyurethane. Liners may also consist of sandwich or composite materials, e.g., a combination of polyurethane for flexibility and glass-fiber reinforced epoxy for high strength and chemical resistance.
• In Stage F, additional material2314 such as a reinforced concrete plug (not shown), additional concrete, and overfill has been emplaced over theliner2312. The additional material2314 may additionally include a plug (not shown) that may extend into the surrounding rock and may serve as or separately consist of a plug to distribute upward pressure forces from the dome of theliner2312, in part or entirely. In other stages of the illustrative construction process depicted inFIG. 23, other components, not shown, may be added, including piping for the introduction and extraction of fluids, pumps, wiring for power and telemetry, spray heads, and other components.
• FIG. 24A is a cross-sectional schematic representation of portions of a linedunderground reservoir system2400.System2400 includes a linedcavity2402, alining2404 including or consisting essentially of concrete and possibly other materials (e.g., metal mesh and/or rebar, shotcrete, piping), a plug orpressure barrier2406 that resists expansive forces exerted by pressurized fluids withincavity2402, afirst piping2408 for injecting gas into and removing gas fromcavity2402, asecond piping2410 for injecting a heat-exchange fluid2412 (e.g., liquid, foam) intocavity2402 in order to thermally condition fluids withincavity2402, athird piping2414 through which settledfluid2416 may be extracted from thecavity2402, and aninfill barrier zone2418. It is desirable that the large forces produced by high-pressure fluids within thecavity2402 be distributed widely through therock mass2422 as well as potentially through theinfill barrier2418. For example, for acylindrical cavity2402 with a diameter of 10 meters, filled with gas at 3,000 psi, a total outward-acting force of 6.9×10⁸pounds is exerted on the upper domed portion of thecavity2402 alone. The uplift and distortion ofrock2422 caused by such forces preferably remains within acceptable limits. In some designs, theinfill barrier zone2418 may be used for other purposes, such as storage of water or equipment. In others, theinfill barrier zone2418 may be filled with various materials to aid in resistance of the force from the pressurizedcylindrical cavity2402. The weight and/or mechanical strength of theinfill barrier2418 contributes to the resistance of expansive forces exerted by pressurized fluid withincavity2402. Also, the mechanical strength of theinfill barrier2418 and the mechanical strength of theplug2406 support the weight of thebarrier2418 and plug2406 during operating conditions when thecavity2402 contains fluid at relatively low pressure (e.g., atmospheric pressure), and thus prevent thecavity2402 from collapsing. In various embodiments, theplug2406 includes or consists essentially of concrete or reinforced concrete. In the illustrative embodiment depicted inFIG. 24A, theplug2406 is approximately circular in transverse cross section (not depicted) and trapezoidal in the longitudinal cross section depicted inFIG. 24A. When thecavity2402 is filled, the wider, upper side of the trapezoidal cross-section tends to transmit forces into the body of the surroundingrock mass2422. Transmission of forces from thecavity2402 into therock mass2422, and the influence of anillustrative plug2406 on such transmission, will be depicted inFIG. 24C andFIG. 24D.
• FIG. 24B is a cross-sectional schematic representation of portions of the illustrative linedunderground reservoir system2400 inFIG. 24A, with the distinction that theplug2424 has a hexagonal longitudinal cross-section rather than a trapezoidal cross section like that of theplug2406 inFIG. 24A. Depending on the mechanical properties of therock mass2422 and on the dimensions of theplugs2406,2424, the plug design ofFIG. 24B may distribute forces through a larger volume of therock mass2422 than the plug design ofFIG. 24A.
• A range of materials may be used for the infill barrier2418: e.g., theinfill barrier2418 may include or consist essentially of rock tailings produced during the excavation of theshaft holding system2400, or of such rock tailings mixed or grouted with a binding agent (e.g., cement), or of concrete, or of reinforced concrete. Althoughinfill barrier2418 is represented inFIG. 24A andFIG. 24B as a uniform mass of material, in various embodiments (not depicted)infill barrier2418 may be a heterogeneous mass of materials (e.g., crushed rock; metal; concrete; reinforced concrete; other) structured in a manner that supports the weight of theinfill2418 itself, resists deformation by expansive forces from thecavity2402, and/or partially transmits forces of weight and/or fluid pressure to the surroundingrock mass2422. For example, the infill barrier may include or consist essentially of a series of layers or cylindrical plugs of grouted rock fragments alternating with trapezoidal or hexagonal plugs peripherally embedded in therock mass2422 in a manner similar to that of theplugs2406 and2424. Force-transmitting extensions of metal, concrete, and other materials may be extended from the mass of any plug or portion of theinfill barrier2418 to the surrounding rock mass. In general, a more-even distribution of forces over the widest feasible bulk of material overlying thecavity2402 will allow for acceptable mitigation of pressure-induced deformations at the lowest possible total shaft depth; this in turn will reduce system costs. Theinfill barrier2418 may extend to the ground surface or some distance below it. The space above the infill barrier may be filled with liquid or used to house equipment, including compressor/expanders or other gas processing facilities.
• The depth at whichcavity2402 is located beneath the earth's surface, the temperatures of the fluids stored within thecavity2402 at various times, and the nature of the layering materials with which thecavity2402 is surrounded (e.g., insulating, non-insulating), are among the factors that may influence the exchange of thermal energy between the contents ofcavity2402 and the surroundingrock2422. Since the mass of the Earth is effectively infinite compared to the mass of the contents ofcavity2402, the temperature-depth gradient ofrock mass2422 will tend to retain its undisturbed, natural value away from the immediate vicinity of the linedunderground reservoir2400. Therefore, if thecavity2402 is not lined with an effective insulator, exchange of heat between the contents ofcavity2402 and therock2422 may constitute either (a) a path of net energy loss forsystem2400, i.e., if the contents of thecavity2402 are warmer on average than surroundingrock2422, or (b) a path of net energy gain forsystem2400, if the contents of thecavity2402 are cooler on average than therock2422. For example, an adiabatic compressed-air energy storage system with stored air cycled (stored and released) daily with a maximum storage pressure of 5 MPa (725 psi) and a constant air injection temperature of 21.5° C. may experience approximately 3.3% thermal energy loss. For a relativelydeep cavity2402, and/or relatively cool fluid contents ofcavity2402, and/or a locally steep temperature/depth gradient, this relationship may be reversed: i.e., thesystem2400 may function not only as a system for storing energy, but also as a harvester of geothermal energy. The ability of any particular embodiment to function partly as a harvester of geothermal energy may depend on depth, construction materials, fluid operating temperatures, operational cycling, and/or local geothermal conditions, among other factors. The concrete used in the lined underground reservoir walls may be of an insulating type having a the thermal conductivity less than a standard concrete mixture, decreasing the rate of exchange between the surroundingrock2422 and the fluid within thecavity2402. The insulating concrete may be located throughout or only at certain layers such as closest to the surroundingrock2422. Examples of insulating concrete include cellular concretes (e.g., where air voids are incorporated into concrete) and aggregate concretes (e.g., concrete made with insulating aggregates such as expanded perlite, vermiculate, and/or polystyrene pellets). Physical properties of insulating concrete vary according to mix designs, with lower density typically corresponding to higher insulating value. Insulating concretes may have thermal conductivities on the order of 2 to 10 times lower than a non-insulating concrete (where heavyweight non-insulating concrete may have a thermal conductivity exceeding 1 W/m-K). Thus, the thermal conductivity of insulating concrete utilized in various embodiments of the invention may be between approximately 0.1 W/m-K and approximately 0.5 W/m-K. Insulating layers (not shown) of other materials (e.g., polyurethane foam) may also be applied interior or exterior to thecavity2402, decreasing the rate of exchange between the surroundingrock2422 and the fluid with thecavity2402.
• FIG. 24C is a cross-sectional schematic representation of portions of an illustrative linedunderground reservoir system2400 like that ofFIG. 24A, with the distinction that theplug2406 depicted inFIG. 24A is absent. InFIG. 24C, illustrative forces acting on select points in the material above thecavity2402 are indicated by arrows. In the state of operation depicted inFIG. 24C, thecavity2402 is filled with a pressurized gas and a potential failure mode of thesystem2400 is uplift of the material overlying thecavity2402. Also, therock2422 surrounding thecavity2402 is presumed, for this illustrative system, to be so rigid and so horizontally extensive that any purely lateral shifting of therock2422 by the pressurized contents ofcavity2402 is insignificant. Any displacement ofrock2422 andinfill2418 is, therefore, presumed to occur within a volume centered above thecavity2402 and taking, roughly, the form of an inverted truncated cone with curvingsides2430 indicated by dashed lines. This volume is herein also termed “the cone.” The upper base of the cone is anarea2428 on the surface and centered above thecavity2402. The lower base (not indicated inFIG. 24C) of the inverted cone is a horizontal surface area directly above thecavity2402. Shearing (slippage between two portions of a body of material) will typically tend to occur in therock2422 along thesurface2430 if sufficient upward force is exerted by the pressurized contents ofcavity2402.
• Given the finite flexibility of real (i.e., not idealized) earth material, some degree of uplift or doming of thearea2428—though preferably no shearing alongsurface2430—may occur in any real-world setting. Such doming is deemed acceptable if it does not damage components of thesystem2400, either immediately or over repeated fill-and-empty cycles; such doming is deemed unacceptable if it destroys components of thesystem2400 or shortens their working lifespan significantly. Thesystem2400 is preferably designed, therefore, to contain the upward-actingforces2432 generated by the pressurized contents ofcavity2402 not only to the extent that catastrophic failure of the cavity2402 (i.e., breakthrough of gas to the surface, or explosion of part or all of the overlying area2428) is practically impossible, but, further, to the extent that the longevity ofsystem2400 is not compromised.
• In the absence of an advantageously shaped top-plug, as depicted inFIG. 24C,forces2432 exerted by the contents ofcavity2402 act vertically and laterally throughout the volume of the cone having curvedlateral surface2430. Directly above thecavity2402, a substantiallyvertical force2434 is exerted upon theinfill2418. Elsewhere within the cone, angled forces2436 (i.e., forces having both horizontal and vertical components) are exerted within theinfill2418 androck2422. At a given depth above thecavity2402, the magnitude of both thevertical force2434 and theangled forces2436 depends primarily on the magnitude of theforce2432 exerted by the contents ofcavity2402 and on the width, at the given depth, of the cone.
• FIG. 24D is a cross-sectional schematic representation of portions of the illustrative linedunderground reservoir system2400 inFIG. 24A, including theplug2406 having a trapezoidal cross section. The primary effect of theplug2406, with respect to the transmission of forces throughout therock2422 andinfill2418, is to broaden both the lower and upper bases of the inverted, truncated cone described above with regard toFIG. 24C. Likewise, theplug2406 may transmit nearly all the uplift force to therock2422 with little force transmitted to theinfill2418. As a result, at any given depth thevertical force2434 is much smaller in magnitude and the angled forces are widely distributed throughout therock2422. In general, theupward forces2432 originated at the top of thecavity2402 are spread over a larger area, at any given depth, than for the plugless system depicted inFIG. 24C. This relative transmission and dissipation of force at a given depth is indicated by the greater number of the force arrows (2434,2436) inFIG. 24D, compared to those inFIG. 24C. Doming ofarea2428 is lessened, shearing alongsurface2430 is rendered less likely, and, in general, damage to or failure of components ofsystem2400 as a result of material displacement within or above the cone is rendered less likely. The force-spreading effect of theplug2406, or, in various other embodiments, a plug of some other form (e.g., plug2424 ofFIG. 24B), may thus be used to (a) increase the safety factor of thesystem2400, (b) enable acavity2402 at a certain depth to store fluid at a higher peak pressure than would be feasible without theplug2424, (c) enable acavity2402 storing fluid at a given peak pressure to be constructed at a lesser depth (and therefore more economically) than would be feasible without theplug2424, or (d) some combination of two or more of (a), (b), and (c).
• Plugs (pressure barriers) of orientations or cross-sectional forms different from those illustratively depicted inFIG. 24A,FIG. 24B, andFIG. 24D are also contemplated and in some cases may be more effective than those depicted. For example, thepressure barrier2406 ofFIG. 24A might be constructed, in various embodiments, with a smoothly curved surface (e.g., a surface protruding into the surrounding rock at one or more points).
• FIG. 25 is a cross-sectional schematic representation of portions of an illustrative energy storage andgeneration system2500 that includes a linedunderground reservoir2502. The linedunderground reservoir2502 is similar to that depicted inFIG. 9C, albeit with certain differences. Thesystem2500 includes apower system2504, which may resemble systems shown and described in the '207 patent and the '155 patent, for the interconversion of electrical, thermal, and elastic potential energy. Primarily, the power system2504 (a) interconverts electricity with the elastic potential energy of gas expanded and/or compressed at approximately constant temperature (i.e., isothermally) and (b) interconverts the thermal energy of gas and/or a heat-exchange liquid with the elastic potential energy of gas to be expanded and/or compressed. Herein, thesystem2504 is termed an “isothermal power system.” Bodies of heat-exchange liquid (or liquids) may be employed both for the exchange of heat with gas stored in thereservoir2502 and as thermal reservoirs (i.e., thermal wells); in various other embodiments, they may be employed additionally or alternatively as reservoirs of gravitational potential energy. It may be desirable, in various circumstances (e.g., installation in an urban area) to minimize the surface area occupied by facilities associated withsystem2500; in such circumstances, theisothermal power system2504 may be located, as insystem2500, in achamber2506 beneath the surface of the ground.Chamber2506 may be excavated during the excavation ofreservoir2502 through upper, middle, andlower access tunnels2508,2510, and2512, and access to theisothermal power system2504 may be maintained throughupper access tunnel2508. Since the lower ends ofsloping access tunnels2510 and1512 are sealed byplugs2514 to prevent fluids from escapingreservoir2502, heat-exchange liquid2516 may be stored in the portions of thelower access tunnel2512 andmiddle access tunnel2510. Theisothermal power system2504 may add liquid to or extract liquid from thetunnels2510,2512 throughpiping2518. In thesystem2500, all major components—power system, liquid storage, and gas storage—are located underground, out of sight. Moreover, an energy storage and retrieval system thus located would be to a large extent safeguarded from natural forces, accidents, and deliberate attack. Thepower system2504 may also be a gas processing facility or other energy storage power unit.
• Storage of a volume of heat-exchange liquid may also be achieved in various other embodiments without use of surface vessels for liquid storage.FIG. 26 is a cross-sectional schematic representation of portions of a linedunderground reservoir system2600 that is similar in most respects to linedunderground reservoir system2400 of FIG.
• 24A, with the distinction that instead of a solid infill barrier2418 (FIG. 24A), the shaft ofsystem2600 is infilled with areservoir2620 of heat-exchange liquid on top of theplug2606. Also,system2600 is equipped with piping2622 for the addition of liquid to and subtraction of liquid from thereservoir2620.
• If the lining surrounding the inner cavity of a lined underground reservoir storage system is of sufficient strength, infilling may be dispensed with, and the lined portion of the storage system may protrude above the surface of the ground.FIG. 27 is a schematic representation of portions of an illustrative embodiment of the invention in which the lined portion of the storage system protrudes above the surface of the ground.LUR system2700 is disposed at least partially within a vertical, artificial cavern orshaft2702, typically but not necessarily circular in cross-section, which may be part of a larger system (not shown) for the storage and recovery of energy.
• In various embodiments,system2700 is a recessed LUR containing fluid that may be pressurized and/or heated. Pressurization of the fluid enables the storage of elastic potential energy; heating of the fluid enables the storage of thermal energy; and a stored fluid may be both pressurized and heated.Shaft2702 may be lined with an impermeable material that prevents leakage of fluids into or out of theshaft2702; the material may also act as a thermal insulator. Alternatively or additionally,shaft2702 may be lined with a distinct layer that acts primarily as a thermal insulator.
• In the illustrative embodiment depicted inFIG. 27,shaft2702 is vertical and circular in cross-section. As theshaft2702 is sunk, a liner2704 (which includes or consists essentially of reinforced concrete such as in a pre-stressed concrete storage vessel and/or some other material) for the interior wall of theshaft2702 may be installed in a series of rings, each ring being added below previous rings as the excavating machine increases the depth of the bore by a suitable amount. The inner and/or outer surface of theliner2704 may be coated with one or more coatings or additional layers of material (not shown inFIG. 27), which may serve to prevent leakage of fluid into or out of theshaft2702, to preserve theliner2704 from corrosion or degradation, to thermally insulate theshaft2702 from the surroundingearth2706, or more perform two or more of these functions. In general, ashaft2702 of greater depth and/or radius will be capable of storing more thermal and elastic potential energy than ashaft2702 of smaller depth and/or radius.
• Additionally, a cap ordome2708 is connected to the top of theshaft2702 andliner2704 in order to produce a sealed recessed storage reservoir.Cap2708 may include or consist essentially of reinforced concrete and/or one or more other durable materials and, like theliner2704 ofshaft2702, may be coated with one or more coatings or additional layers of material (not shown inFIG. 27), interiorly and/or exteriorly, that may serve to seal, protect, or insulate thecap2708.
• In the illustrative embodiment depicted inFIG. 27,reservoir2700 contains an accumulation of fluid (e.g., foam or liquid)2710 andgas2712. Thegas2712 occupies the portion ofshaft2702 not occupied bynon-gaseous fluid2710. The contents ofreservoir2700 may be at high pressure (e.g., 3,000 psig) and relatively high temperature (e.g., 60° C.).
• Piping2714 passes through cap2708 (or, in various other embodiments, some portion of theliner2704 of reservoir2700) and extends to near the bottom of theshaft2702. Apump2716 is capable of drawing fluid2710 intopiping2714 and expelling the fluid from theshaft2702. Power, control, and data cables (not shown) may also enterreservoir2700, enabling the control and operation ofpump2716 and communication with sensors (not shown) insideshaft2702 that provide information to operators ofreservoir2700 on various physical variables, e.g., pressure and temperature of the fluid contents ofreservoir2700 and depth offluid2710.
• Fluid expelled fromreservoir2700 bypump2716 may be directed via piping2718 to reservoirs, cylinders, or other components of an energy storage and recovery system (not shown), or may be directed via piping2720 to a spray head or nozzle (not explicitly shown) for the generation of a foam ordroplet spray2722 within the gas-filled portion ofreservoir2700. The foam ordroplet spray2722 may exchange heat with the fluids insidereservoir2700. In various embodiments, fluid passing throughpiping2720 is additionally passed through pumps, valves, heat exchangers, and other devices (not shown) before being returned to the interior ofreservoir2700.Additional piping2724 allows the addition to or removal fromreservoir2700 ofgas2712.
• FIG. 28 is a schematic representation of portions of another illustrative embodiment of the invention. Recessedreservoir2800 is at least partially disposed within a vertical, artificial cavern orshaft2802, typically but not necessarily circular in cross-section, and may be part of a larger system (not shown) for the storage and recovery of energy.Shaft2802 may be constructed by means similar toshaft2702 inFIG. 27, and may be lined in a manner similar toshaft2702 inFIG. 27.
• A liner2804 (which may include or consist essentially of, e.g., reinforced concrete and steel and/or other durable materials) within the interior wall of theshaft2802 may be installed to construct a recessed reservoir capable of holding fluids at high pressure and/or at elevated temperature, as described with respect toFIG. 27. Liquid may be separated from the gaseous component prior to storage by a separator (e.g., a gravity separator), not shown, prior to delivery at elevated pressure intoshaft2802. Liquid at high pressure and/or elevated temperature may be delivered via apipe2820 to asecondary containment unit2814 as illustrated inFIG. 28. Thissecondary containment unit2814 may be at higher elevation than the bottom of thevertical shaft2802. The secondary containment unit may be an open container within theliner2804 as illustrated inFIG. 28, or may be a separate pressure vessel or vertical shaft at a higher elevation or above ground level. By keeping the liquid portion of the storage at higher elevation (closer to the elevation of the ground level), lower power (and energy) may be required to pump the liquid into and out ofreservoir2800. (That is, the vertical distance (head) is less between the ground level andsecondary reservoir2814 than between the ground level and the bottom of the vertical shaft2802).
• The separated high pressure and/or elevated temperature gas may be delivered toshaft2802 via apipe2824.Liquid2810 and2830 may be removed fromshaft2802 viapumps2816 and2836. Pump2836 will generally consume less power to pump the liquid2830 (at least as a function of volume of liquid pumped) than will pump2816 to pump liquid2810, as the vertical distance from liquid2830 to the ground surface is much less. Thus, in preferred embodiments of the invention, most or substantially all of the liquid inshaft2802 is directed tosecondary containment2814, with only a fraction of the liquid being at the bottom ofshaft2802.
• Fluid expelled fromshaft2802 bypump2816 and fromsecondary containment2814 by pump2836 may be directed via piping2818 to reservoirs, cylinders, or other components of an energy storage and recovery system (not shown), or may be directed via to a spray head or nozzle for the generation of a foam ordroplet spray2822 within the gas-filled portion ofshaft2802 and/or secondary containment2814 (spray or foam incontainment2814 is not shown). The foam ordroplet spray2822 may exchange heat with the fluids insideshaft2802 and/orsecondary containment2814. In various embodiments, fluid passing throughpiping2818 is additionally passed through pumps, valves, heat exchangers, and other devices (not shown) before being returned to the interior ofshaft2802.Additional piping2824 allows the addition to or removal fromshaft2802 ofgas2812.
• Generally, the systems described herein featuring IPVs, LURs and/or recessed reservoirs may be operated in both an expansion mode and in compression mode as part of a full-cycle energy storage system with high efficiency. For example, the systems described herein may be operated so as to efficiently (e.g., substantially isothermally) store pressure and thermal potential energy delivered from an energy storage system and possibly from other sources as well, or so as to efficiently deliver to the energy storage system pressure and thermal potential energy stored within the systems described herein. Heat-exchange liquid may be caused to exchange heat with pressurized gas in a lined underground reservoir or IPV by several methods, e.g., bringing the heat-exchanged fluid and pressurized gas into direct contact with each other or by employing a non-mixing heat exchanger that permits the liquid and gas to exchange heat through impermeable, heat-conductive barriers. If heat-exchange liquid is brought into contact with pressurized gas for the purpose of exchanging heat, it is in general preferable that the heat-exchange liquid be divided into droplets or mixed with the gas in the form of a foam in order to increase surface area over which the gas and liquid may exchange heat; or, if the volume of liquid is large relative to the volume of gas, the gas may be bubbled through the liquid to increase the surface area of contact. Lower cost for a given rate of heat exchange between bodies of liquid and gas is generally achieved by bringing the liquid and gas into direct contact with each other.
• Gas stored in lined underground reservoirs or IPVs may be thermally conditioned either in situ, that is, within the reservoir or IPV, or in external devices (e.g., sprayers, bubblers, or heat exchangers located in a facility on the surface of the earth). It is generally preferable, for in situ thermal conditioning, that the heat-exchange liquid and stored gas be brought into direct contact with each other by spraying or foaming the heat-exchange liquid into the stored gas. Alternatively or additionally, heat-exchange fluid may be mixed with stored gas in order to maintain the gas at an approximately constant temperature as it is expanded in, e.g., cylinder. That is, approximately isothermal expansion of the gas may be achieved by mixing of heat-exchange liquid at an appropriate rate and temperature, as droplets or the liquid component of a foam, with the gas. Thermal conditioning of a gas may occur during compression of the gas, storage of the gas, or expansion of the gas.
• FIGS. 29-32 schematically depict several illustrative methods for thermally conditioning gas released from a lined underground reservoir, IPV, or other reservoir as or before the gas is expanded in a cylinder.
• FIG. 29 is a schematic diagram showing components of asystem2900 for achieving approximately isothermal compression and expansion of a gas for energy storage and recovery using a pneumatic cylinder2902 (shown in partial cross-section) according to embodiments of the invention. Thecylinder2902 typically contains a slidably disposedpiston2904 that divides thecylinder2902 into twochambers2906,2908. Areservoir2910, which may consist essentially of one or more pressure vessels and/or one or more IPVs, and/or one or more LURs, contains gas at high pressure (e.g., 3,000 psi); thereservoir2910 may also contain a quantity of heat-exchange liquid2912. The heat-exchange liquid2912 may contain an additive that increases the liquid's tendency to foam (e.g., by lowering the surface tension of the liquid2912). Additives may include surfactants (e.g., sulfonates), a micro-emulsion of a lubricating fluid such as mineral oil, a solution of agents such as glycols (e.g., propylene glycol), or soluble synthetics (e.g., ethanolamines). Foaming agents such as sulfonates (e.g., linear alkyl benzene sulfonate such as Bio-Soft D-40 available from Stepan Company of Illinois) may be added, or commercially available foaming concentrates such as firefighting foam concentrates (e.g., fluorosurfactant products such as those available from ChemGuard of Texas) may be used. Such additives tend to reduce liquid surface tension of water and lead to substantial foaming when sprayed. Commercially available fluids may be used at an approximately 5% solution in water, such as Mecagreen 127 (available from the Condat Corporation of Michigan), which consists in part of a micro-emulsion of mineral oil, and Quintolubric 807-WP (available from the Quaker Chemical Corporation of Pennsylvania), which consists in part of a soluble ethanolamine. Other additives may be used at higher concentrations (such as at a 50% solution in water), including Cryo-tek 100/Al (available from the Hercules Chemical Company of New Jersey), which consists in part of a propylene glycol. These fluids may be further modified to enhance foaming while being sprayed and to speed defoaming when in a reservoir.
• Apump2914 and piping2916 may convey the heat-exchange liquid to a device herein termed a “mixing chamber”2918. Gas from thereservoir2910 may also be conveyed (via piping2920) to themixing chamber2918. Within themixing chamber2918, a foam-generating mechanism2922 combines the gas from thereservoir2910 and the liquid conveyed by piping2916 to createfoam2924 of a certain grade (i.e., bubble size variance, average bubble size, void fraction), herein termed Foam A, inside themixing chamber2918.
• Themixing chamber2918 may contain ascreen2926 or other mechanism (e.g., source of ultrasound) to vary or homogenize foam structure.Screen2926 may be located, e.g., at or near the exit of mixingchamber2918. Foam that has passed through thescreen2926 may have a different bubble size and other characteristics from Foam A and is herein termed Foam B (2928). In other embodiments, thescreen2926 is omitted, so that Foam A is transferred without deliberate alteration tochamber2906.
• The exit of themixing chamber2918 is connected by piping2930 to a port in thecylinder2902 that is gated by a valve2932 (e.g., a poppet-style valve) that permits fluid from piping2930 to enter the upper chamber (air chamber)2906 of thecylinder2902. Valves (not shown) may control the flow of gas from thereservoir2910 through piping2920 to themixing chamber2918, and from themixing chamber2918 through piping2928 to theupper chamber2906 of thecylinder2902. Another valve2934 (e.g., a poppet-style valve) permits theupper chamber2906 to communicate with other components of thesystem2900, e.g., an additional separator device (not shown), the upper chamber of another cylinder (not shown), or a vent to the ambient atmosphere (not shown).
• The volume ofreservoir2910 may be large (e.g., at least approximately four times larger) relative to the volume of themixing chamber2918 andcylinder2902.
• Foam A and Foam B are preferably statically stable foams over a portion or all of the time-scale of typical cyclic operation of system2900: e.g., for a 120 RPM system (i.e., 0.5 seconds per revolution), the foam may remain substantially unchanged (e.g., less than 10% drainage) after 5.5 seconds or a time approximately five times greater than the revolution time.
• In an initial state of operation of a procedure whereby gas stored in thereservoir2910 is expanded to release energy, thevalve2932 is open, thevalve2934 is closed, and thepiston2904 is near top dead center of cylinder2902 (i.e., toward the top of the cylinder2902). Gas from thereservoir2910 is allowed to flow through piping2920 to themixing chamber2918 while liquid from thereservoir2910 is pumped bypump2914 to themixing chamber2918. The gas and liquid thus conveyed to themixing chamber2918 are combined by the foam-generating mechanism2922 to form Foam A (2924), which partly or substantially fills the main chamber of themixing chamber2918. Exiting themixing chamber2918, Foam A passes through thescreen2926, being altered thereby to Foam B. Foam B, which is at approximately the same pressure as the gas stored inreservoir2910, passes throughvalve2932 intochamber2906. Inchamber2906, Foam B exerts a force on thepiston2904 that may be communicated to a mechanism (e.g., an electric generator, not shown) external to thecylinder2902 by arod2936 that is connected topiston2904 and that passes slideably through the lower end cap of thecylinder2902.
• The gas component of the foam inchamber2906 expands as thepiston2904 androd2936 move downward. At some point in the downward motion ofpiston2904, the flow of gas fromreservoir2910 into themixing chamber2918 and thence (as the gas component of Foam B) intochamber2906 may be ended by appropriate operation of valves (not shown). As the gas component of the foam inchamber2906 expands, it will tend, unless heat is transferred to it, to decrease in temperature according to the Ideal Gas Law; however, if the liquid component of the foam inchamber2906 is at a higher temperature than the gas component of the foam inchamber2906, heat will tend to be transferred from the liquid component to the gas component. Therefore, the temperature of the gas component of the foam withinchamber2906 will tend to remain constant (approximately isothermal) as the gas component expands.
• When thepiston2904 approaches bottom dead center of cylinder2902 (i.e., has moved down to approximately its limit of motion),valve2932 may be closed andvalve2934 may be opened, allowing the expanded gas inchamber2906 to pass fromcylinder2902 to some other component of thesystem2900, e.g., a vent or a chamber of another cylinder for further expansion.
• In some embodiments,pump2914 is a variable-speed pump, i.e., may be operated so as to transfer liquid2912 at a slower or faster rate from thereservoir2910 to the foam-generating mechanism2922 and may be responsive to signals from the control system (not shown). If the rate at which liquid2912 is transferred by thepump2914 to the foam-mechanism2922 is increased relative to the rate at which gas is conveyed fromreservoir2910 through piping2920 to themechanism2922, the void fraction of the foam produced by themechanism2922 may be decreased. If the foam generated by the mechanism2922 (Foam A) has a relatively low void fraction, the foam conveyed to chamber2906 (Foam B) will generally also tend to have a relatively low void fraction. When the void fraction of a foam is lower, more of the foam consists of liquid, so more thermal energy may be exchanged between the gas component of the foam and the liquid component of the foam before the gas and liquid components come into thermal equilibrium with each other (i.e., cease to change in relative temperature). When gas at relatively high density (e.g., ambient temperature, high pressure) is being transferred from thereservoir2910 tochamber2906, it may be advantageous to generate foam having a lower void fraction, enabling the liquid fraction of the foam to exchange a correspondingly larger quantity of thermal energy with the gas fraction of the foam.
• All pumps shown in subsequent figures herein may also be variable-speed pumps and may be controlled based on signals from the control system. Signals from the control system may be based on system-performance (e.g., gas temperature and/or pressure, cycle time, etc.) measurements from one or more previous cycles of compression and/or expansion.
• Embodiments of the invention increase the efficiency of asystem2900 for the storage and retrieval of energy using compressed gas by enabling the surface area of a given quantity of heat-exchange liquid2912 to be greatly increased (with correspondingly accelerated heat transfer between liquid2912 and gas undergoing expansion or compression within cylinder2902) with less investment of energy than would be required by alternative methods of increasing the surface of area of the liquid, e.g., the conversion of the liquid2912 to a spray.
• In other embodiments, thereservoir2910 is a separator rather than a high-pressure storage reservoir as depicted inFIG. 29. In such embodiments, piping, valves, and other components not shown inFIG. 29 are supplied that allow the separator to be placed in fluid communication with a high-pressure gas storage reservoir as well as with themixing chamber2918, as shown and described in the '128 application.
• FIG. 30 is a schematic diagram showing components of asystem3000 for achieving approximately isothermal compression and expansion of a gas for energy storage and recovery using a pneumatic cylinder3004 (shown in partial cross-section) according to embodiments of the invention.System3000 is similar tosystem2900 inFIG. 29, except thatsystem3000 includes abypass pipe3038. Moreover, twovalves3040,3042 are explicitly depicted inFIG. 30.Bypass pipe3038 may be employed as follows: (1) when gas is being released from thestorage reservoir3010, mixed with heat-exchange liquid3012 in themixing chamber3018, and conveyed to chamber3006 ofcylinder3004 to be expanded therein,valve3040 will be closed andvalve3042 open; (2) when gas has been compressed in chamber3006 ofcylinder3004 and is to be conveyed to thereservoir3010 for storage,valve3040 will be open andvalve3042 closed. Less friction will tend to be encountered by fluids passing throughvalve3040 andbypass pipe3038 than by fluids passing throughvalve3042 andscreen3026 and around the foam-generating mechanism3022. In other embodiments,valve3042 is omitted, allowing fluid to be routed through thebypass pipe3038 by the higher resistance presented by themixing chamber3018, andvalve3040 is a check valve preventing fluid flow when gas is being released in expansion mode. The direction of fluid flow from chamber3006 to thereservoir3010 via a lower-resistance pathway (i.e., the bypass pipe3038) will tend to result in lower frictional losses during such flow and therefore higher efficiency forsystem3000.
• In various other embodiments, thereservoir3010 is a separator rather than a high-pressure storage reservoir as depicted inFIG. 30. In such embodiments, piping, valves, and other components not shown inFIG. 30 are supplied that allow the separator to be placed in fluid communication with a high-pressure gas storage reservoir as well as with themixing chamber3018 andbypass pipe3038.
• FIG. 31 is a schematic diagram showing components of asystem3100 for achieving approximately isothermal compression and expansion of a gas for energy storage and recovery using a pneumatic cylinder3102 (shown in partial cross-section) according to embodiments of the invention.System3100 is similar tosystem2900 inFIG. 29 except thatsystem3100 omits themixing chamber2918 and instead generates foam inside thestorage reservoir3110. Insystem3100, apump3114 circulates heat-exchange liquid3112 to a foam-generating mechanism3122 (e.g., one or more spray nozzles) inside thereservoir3110. Thereservoir3110 may, by means of thepump3114 andmechanism3122, be filled partly or entirely by foam of an initial or original character, Foam A (3124). Thereservoir3110 may be placed in fluid communication viapipe3120 with a valve-gatedport3144 incylinder3102. Valves (not shown) may govern the flow of fluid throughpipe3120. An optional screen3126 (or other suitable mechanism such as an ultrasound source), shown inFIG. 31 insidepipe3120 but locatable anywhere in the path of fluid flow betweenreservoir3110 andchamber3106 of thecylinder3102, serves to alter Foam A (3124) to Foam B (3128), regulating characteristics such as bubble-size variance and average bubble size.
• In other embodiments, thereservoir3110 is a separator rather than a high-pressure storage reservoir as depicted inFIG. 31. In such embodiments, piping, valves, and other components not shown inFIG. 31 will be supplied that allow the separator to be placed in fluid communication with a high-pressure gas storage reservoir as well as with thecylinder3102. In other embodiments, a bypass pipe similar to that depicted inFIG. 30 is added tosystem3100 in order to allow fluid to pass fromcylinder3102 toreservoir3110 without passing through thescreen3126.
• FIG. 32 is a schematic diagram showing components of asystem3200 for achieving approximately isothermal compression and expansion of a gas for energy storage and recovery using a pneumatic cylinder3202 (shown in partial cross-section) according to embodiments of the invention.System3200 is similar tosystem2900 inFIG. 29, except thatsystem3200 omits themixing chamber2918 and instead generates foam inside theair chamber3206 of the cylinder3202. Insystem3200, apump3214 circulates heat-exchange liquid3212 to a foam-generating mechanism3222 (e.g., one or more spray nozzles injecting into cylinder and/or onto a screen through which admitted air passes) either located within, or communicating with (e.g., through a port),chamber3206. Thechamber3206 may, by means of thepump3214 and mechanism3222 (and by means of gas supplied fromreservoir3210 viapipe3220 through a port3244), be filled partly or substantially entirely by foam. Thereservoir3210 may be placed in fluid communication viapipe3220 with valve-gatedport3244 in cylinder3202. Valves (not shown) may govern the flow of fluid throughpipe3220.
• FIG. 33A is a plot of relationships between stress range (in this case, referring to fluid storage pressure) and lifespan cycle number for an illustrative LUR system utilized as a facility for storage of compressed air, herein referred to as the “Demo Plant.” The Demo Plant resemblessystem900 inFIGS. 9A and 9B and has a volume of 40,000 m³. Herein, a “cycle” is complete filling of an empty storage vessel to a specified storage pressure (e.g., 3,000 psi) followed by emptying of the vessel to a lower pressure (e.g., 500 psi). The Demo Plant employs a cavity lining resembling those shown inFIG. 14A,FIG. 14B, andFIG. 21D, and adesign cycle demand3302 for the Demo Plant is to withstand100 full operating pressure cycles. InFIG. 33A, a [Steel]Fatigue Design Curve3304 is based on theEurocode 3 standard (i.e., “EN 1993—Eurocode 3: Design of Steel Structures,” European Committee for Standardization, 2004, the entire disclosure of which is incorporated by reference herein). The Design Stress Range3306 (i.e., value of the maximum stress range sustainable by the steel lining) is approximately 218 MPa. AsFIG. 33A shows, the design values of 218 MPa and 100 cycles were well below theFatigue Design Curve3304. In fact, with a design stress range of 218 MPa, and given the lifespan limitation imposed by theFatigue Design Curve3304, the Demo Plant operating life is estimated at nearly 40,000 cycles. In fact, the actual stress range (based on measured rock-mass deformations) is estimated to be only approximately 73 MPa. With a stress range of 73 MPa, anAllowable Life3310 would be about one million cycles (2,700 years of operation, at the rate of one full cycle per day). Thus, the longevity of lined underground reservoirs employed as storage vessels for rapid-cycling, large-scale storage of pressurized gasses (e.g., compressed air) is likely, in practice, very long.
• The geophysical properties of a given site may affect the feasibility of constructing a lined underground reservoir at the site. To rate the geological suitability of proposed lined underground reservoir sites, a rock mass rating may be assigned to the rock mass in which construction of a lined underground reservoir is being considered. The rock mass rating system is a geological classification system developed by Z. T. Bieniawski in 1973 and revised in 1989, and is tabulated inFIG. 33B.
• FIG. 34 shows illustrative geological criteria for use in early stages in site selection of a viable lined underground reservoir for storage of pressurized fluids (e.g., air, natural gas). A table3402 shows a classification table for the Rock Mass Rating (RMR) system shown inFIG. 33B, matching numerical RMR values to rock quality. Aplot3404 shows the relationship between RMR rating for a rock mass (horizontal axis) and maximum storage pressure (vertical axis) of a lined underground reservoir storage pressure constructed within the rock mass. Thepoint3406 shows the rock-mass quality and storage pressure of the Demo Plant described with reference toFIG. 33A. In theplot3404, afirst region3408 of generally low rock quality and pressure above approximately 7 MPa generally does not permit the construction of a viable lined underground reservoir; asecond region3410 of low-to-moderate rock quality and low-to-high pressure may permit the construction of a viable lined underground reservoir, but this is not certain; and athird region3412 of low-to-high rock quality and low-to-high pressure does permit the construction of a viable lined underground reservoir.
• InFIG. 34, a dashedline3414 indicates a substantially linear boundary that approximately divides the region of possibly or definitely nonfeasible RMR-pressure space from the region of definitely feasible RMR-pressure space. The region of possibly or definitely nonfeasible RMR-pressure space is to the left of the dashedline3412. The feasible region, to the right of dashedline3412, is defined by the equation P≦(RMR×0.83)−25, where P is storage pressure in MPa (vertical axis) and RMR is the horizontal axis.
• FIG. 35 shows an illustrative plot of estimated construction cost per lined underground reservoir (in units of MEUR, millions of Euros, 2012 value) as a function of reservoir volume (in units of m³) under two different conditions of local (overlying) topography.Curve3502 shows construction cost as a function of reservoir volume for flat overlying topography (e.g., similar to that depicted inFIG. 9B). Curve3504 shows construction cost as a function of reservoir volume for some high-relief overlying topographies (e.g., similar to that depicted inFIG. 9C) that permit minimal access-tunnel length. Flat topography requires, in general, longer access tunnels (which cannot be made excessively steep while still enabling access by standard construction vehicles, e.g., cement trucks and drilling rigs) and therefore longer construction time; high-relief topography may allow shorter access tunnels and therefore shorter construction time (and thus may enable lower construction cost). The data represented inFIG. 35 are based on utilization of the access-tunnel approach of, e.g.,FIG. 9B, rather than the open-shaft approach of, e.g.,FIGS. 21A-21D. The cost level reflects the approximately present European market at time of filing; the accuracy of the estimates is believed to be within ±20%.
• FIG. 36 shows an illustrative plot of estimated construction cost (in units of Euros, 2012 value) per cubic meter for lined underground reservoirs of the same types referred to byFIG. 35.Curve3602 shows construction cost as a function of reservoir volume for flat overlying topography (e.g., similar to that depicted inFIG. 9B).Curve3604 shows construction cost as a function of reservoir volume for some high-relief overlying topographies (e.g., similar to that depicted inFIG. 9C) that permit minimal access-tunnel length.
• FIG. 37 shows an illustrative plot of estimated construction cost (in units of MEUR, millions of Euros, 2012 value) for a lined underground reservoir of the same type referred to byFIG. 35 andFIG. 36 as a function of reservoir volume (in units of m³), broken out by cost for (a) installations, (b) concrete lining, (c) steel lining, (d) underground reservoir construction, including support and drainage, and (e) access tunnels.
• FIG. 38 shows an illustrative plot of estimated construction time (units of years) for a lined underground reservoir of the same type referred to byFIG. 35 andFIG. 36 as a function of reservoir volume (units of m³) under two different conditions of local (overlying) topography.Curve3802 shows construction time as a function of reservoir volume for flat overlying topography (e.g., similar to that depicted inFIG. 9B).Curve3804 shows construction time as a function of reservoir volume for some high-relief overlying topographies (e.g., similar to that depicted inFIG. 9C) that permit minimal access-tunnel length.
• Construction time for open-shaft-style construction of a lined underground reservoir (e.g., as depicted inFIGS. 21A-21D) may be as low as one-fifth that for access-tunnel-style construction of a reservoir of comparable volume for small-scale (e.g. 10,000 m³) high-pressure storage (e.g., 3000 psi). This drastic difference in estimated construction time arises from the rapidity with which a roadheader type shaft-excavating device or other mechanized rock drilling machine such as that depictedFIG. 12A-12B can excavate a volume of rock as compared to excavation of access tunnels and a cavity by the standard drill-blast-and-clear method, which is comparatively slow, expensive, and hazardous to workers. For large volume (e.g., 100,000 m³) LURs, drill-and-blast techniques may proceed more rapidly than mechanized excavating machines due to both better area/volume ratio and quicker excavation.
• In various embodiments of the invention, the heat-exchange fluid utilized to thermally condition gas within one or more cylinders and/or storage vessels (e.g., IPVs and/or recessed storage reservoirs) incorporates one or more additives and/or solutes, as described in U.S. Pat. No. 8,171,128, filed Apr. 8, 2011 (the '128 patent), the entire disclosure of which is incorporated herein by reference. As described in the '128 patent, the additives and/or solutes may reduce the surface tension of the heat-exchange fluid, reduce the solubility of gas into the heat-exchange fluid, and/or slow dissolution of gas into the heat-exchange fluid. They may also (i) retard or prevent corrosion, (ii) enhance lubricity, (iii) prevent formation of or kill microorganisms (such as bacteria), and/or (iv) include an agent to modify surface tension, as desired for a particular system design or application.
• Embodiments of the invention may, during operation, convert energy stored in the form of compressed gas and/or recovered from the expansion of compressed gas into gravitational potential energy, e.g., of a raised mass, as described in U.S. patent application Ser. No. 13/221,563, filed Aug. 30, 2011, the entire disclosure of which is incorporated herein by reference.
• Generally, the systems described herein may be operated in both an expansion mode and in the reverse compression mode as part of a full-cycle energy storage system with high efficiency. For example, the systems may be operated as both compressor and expander, storing electricity in the form of the potential energy of compressed gas and producing electricity from the potential energy of compressed gas. Alternatively, the systems may be operated independently as compressors or expanders.
• The terms and expressions employed herein are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

Claims (23)

What is claimed is:

1-112. (canceled)

113. A method of energy storage utilizing a compressed-gas energy storage system selectively fluidly connected to a lined underground reservoir at least partially surrounded by rock, the method comprising:

substantially isothermally compressing gas with the energy storage system at a compression temperature;

transferring the compressed gas to the lined underground reservoir for storage; and

thereafter, exchanging heat between the stored compressed gas and the rock at least partially surrounding the lined underground reservoir to change a temperature of the stored gas to a storage temperature different from the compression temperature.

114. The method ofclaim 113, further comprising thermally conditioning the compressed gas during transfer to the lined underground reservoir by at least one of (i) spraying droplets of a heat-transfer liquid into the gas or (ii) forming a foam comprising the gas and a heat-transfer liquid.

115. The method ofclaim 113, wherein the storage temperature is lower than the compression temperature.

116. The method ofclaim 113, wherein the storage temperature is higher than the compression temperature.

117. A compressed-gas energy storage and recovery system comprising:

a cylinder assembly for at least one of compressing gas to store energy or expanding gas to recover energy;

a heat-exchange subsystem for thermally conditioning the gas during the at least one of compression or expansion via heat exchange between the gas and a heat-transfer liquid;

a lined underground reservoir for storing at least one of compressed gas or heat-transfer fluid in an interior volume thereof, the lined underground reservoir being substantially impermeable to fluid and comprising an inner steel layer surrounded by an outer concrete layer;

a source of heat-transfer fluid fluidly connected to the interior volume of the lined underground reservoir; and

a sink for heat-transfer fluid fluidly connected to the interior volume of the lined underground reservoir.

118. The system ofclaim 117, further comprising:

disposed within the interior volume of the lined underground reservoir, a nozzle for introducing heat-transfer fluid into the interior volume as a spray of droplets or as a foam;

a first pipe fluidly connecting the cylinder assembly to the interior volume of the lined underground reservoir;

a second pipe fluidly connecting the source of heat-transfer fluid to the nozzle;

a third pipe fluidly connecting an area proximate a bottom portion of the interior volume of the lined underground reservoir and the sink for heat-transfer fluid; and

a pump configured to transfer heat-transfer fluid through the third pipe to the sink for heat-transfer fluid.

119. The system ofclaim 117, wherein the source of heat-transfer fluid and the sink for heat-transfer fluid are the same body of liquid.

120. A compressed-gas energy storage and recovery system comprising:

a cylinder assembly for at least one of compressing gas to store energy or expanding gas to recover energy;

a heat-exchange subsystem for thermally conditioning the gas via heat exchange between the gas and a heat-transfer liquid; and

selectively fluidly connected to the cylinder assembly, a lined underground reservoir for at least one of (i) storage of gas after compression, (ii) supply of compressed gas for expansion, (iii) storage of heat-transfer liquid, or (iv) supply of heat-transfer liquid.

121. The system ofclaim 120, wherein the lined underground reservoir comprises a liner at least partially surrounded by at least one of earth, dirt, or gravel.

122. The system ofclaim 121, wherein the liner comprises at least one of steel or concrete.

123. The system ofclaim 121, further comprising, disposed on at least one of an inner surface of the liner or an outer surface of the liner, a coating for at least one of sealing the liner to prevent fluid flow therethrough, preventing corrosion or degradation of the liner, or for thermally insulating the liner.

124. The system ofclaim 120, wherein at least a portion of the lined underground reservoir is disposed below ground level.

125. The system ofclaim 120, wherein the lined underground reservoir comprises therein a liquid containment region disposed above a bottom surface of the lined underground reservoir.

126. The system ofclaim 120, further comprising, disposed within the lined underground reservoir, at least one of a spray head or nozzle for introducing at least one of heat-transfer liquid or foam.

127. The system ofclaim 120, wherein the lined underground reservoir comprises a container buried beneath and surrounded by at least one of earth, dirt, or gravel.

128. The system ofclaim 127, wherein the container comprises steel.

129. The system ofclaim 127, further comprising, disposed between the container and the at least one of earth, dirt, or gravel, at least one of concrete, an insulating material, fiberglass, or carbon fiber.

130. The system ofclaim 129, wherein the at least one of concrete, an insulating material, fiberglass, or carbon fiber is disposed directly on the container with substantially no gap or air therebetween.

131. The system ofclaim 120, further comprising, disposed within the lined underground reservoir, a circulation apparatus for pumping liquid disposed proximate a bottom surface of the lined underground reservoir to a point outside of the lined underground reservoir.

132. The system ofclaim 131, wherein the lined underground reservoir comprises therein a liquid containment region disposed above a bottom surface of the lined underground reservoir, and further comprising, disposed within the lined underground reservoir, a second circulation apparatus for pumping liquid disposed in the liquid containment region to a point outside of the lined underground reservoir.

133. The system ofclaim 120, further comprising, extending from the cylinder assembly to a point within an interior volume of the lined underground reservoir, a pipe for transferring gas between the cylinder assembly and the lined underground reservoir.

134. The system ofclaim 120, wherein the lined underground reservoir comprises a plurality of discrete containers disposed within a shaft extending below ground level.

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