CN114096789A - High Efficiency Low Cost Static Planar Solar Concentrators - Google Patents

Abstract

The invention relates to a solar concentrator comprising at least one reflective or semi-reflective first primary collector (1) that pre-focuses light towards a heliostat secondary collector (2) that concentrates the light onto any target or energy conversion unit (3), characterized in that the primary collector (1) is planar and static.

Description

High efficiency low cost static planar solar concentrator

Technical Field

The present invention relates to the field of solar energy collection and concentration according to an innovative approach to high efficiency and low cost sensors. The device according to the invention makes it possible to dispense with the existing heliostats, which are particularly bulky, inefficient, bulky and expensive.

Solar energy is undoubtedly the source of NRE (new renewable energy) that best meets global energy needs and should meet climate challenges. The present invention relates to the field of solar energy capture and concentration and enables the recovery of more than 90% of the incident solar energy, almost 900w/m2, i.e. 10 times more than conventional PV (photovoltaic) technology.

Current NRE solutions, such as PV or CSP (concentrated solar power) cannot adequately meet current and future energy demands for the following reasons: they have almost only a very low "real" efficiency of 6% to 20%, their high price, their implementation using complex and expensive devices requiring specialists, their generation of pollution during their manufacture, the need to use a large amount of limited land resources, their non-recyclability of parts, their product being unitary (electricity only) and the need to consume water for expensive maintenance (especially in desert environments).

Furthermore, these methods require storage devices based mainly on expensive and contaminated batteries, the capacity of which is particularly limited. In addition, the existing methods cannot achieve the high collection rate required for high efficiency, except for the Dish-Stirling type (Dish-Stirling type) heavy parabolic method, which is circular and therefore cannot optimize collector area and increase footprint.

Furthermore, existing devices require, for their operation or to increase their productivity, very heavy, bulky and very expensive heliostat assemblies which are particularly sensitive to weather conditions and require a large surface area, while generating harmful shadow zones which result in up to 70% area loss due to shadow effects.

The present invention overcomes these problems by providing an extremely intelligent, efficient, durable and environmentally friendly solution for capturing and concentrating solar energy due to an extremely simple, efficient and especially innovative solar energy concentrating method of very low cost and very high efficiency, as it is mainly made of recycled and recyclable materials. In addition, devices with a carbon footprint close to zero can be easily produced.

The present invention may be used in a variety of applications, such as (but not limited to):

in general, high efficiency solar concentration;

-generating electrical energy via PV (photovoltaic), thermodynamics, Peltier (Peltier) or other methods;

-steam or hot fluid production;

heating or cooling, air conditioning;

-lighting;

-drinking water production;

energy intensive industrial processes for heating or melting materials such as steel products, glass products, steel production, etc.;

solar energy reformation in thermal and nuclear power plants and the like;

hydrogen production or various chemical processes;

-the provision of satellites, radio or spacecraft, non-terrestrial bases;

-an astronomical application or a probe,

and the like.

Different types of solar power plants with fresnel mirrors are known, which comprise a support for a set of mirrors consisting of mirror strips, called primary mirrors, each mirror strip being pivoted relative to the support about a respective axis of rotation, called primary axis, and intended to collect the solar rays in order to concentrate them in the direction of one or more concentrator elements having the same or different properties.

The difficulty lies in the orientation of the concentrator, which, given its weight, requires a very robust mechanism that is also subject to severe weather and often fluctuating climatic conditions. To reduce costs, the principle of fresnel concentrators is also used in the prior art using planar (flat) mirrors, called "compact linear reflectors", which are cheaper than parabolic mirrors. Each of these mirrors may rotate following the path of the sun to constantly divert and concentrate the rays of the sun to the absorber tubes.

In addition, the prior devices use a moveable mirror, the reflective portion of which is located at the rear of a glass block, the thickness of which significantly reduces the optical performance, and involve larger glass blocks to ensure the strength and durability of the assembly.

Other approaches use parabolic mirrors, as in the dish stirling approach, which allows optimum performance to be achieved, but do not contribute to the complexity of the assembly, cost, footprint and extreme sensitivity to weather conditions.

Background

Patent application US20110088694a1 is known in the prior art and describes an improved fluid flow metering device comprising a light-reinforced acrylic block flow tube to optimize visualization of pressure readings. An LED or other light source is mounted on top of the flow tube and illuminates the float or spool from above to provide a more accurate reading, especially in low light conditions such as modern operating rooms. In addition, the light enhanced flow tube can provide a mechanical backup in case of failure of the updated electronic system, and visually matches the graphical flow display, while providing a double check of the electronic system.

Disadvantages of the background Art

A drawback of the solutions of the prior art is that the optical mirrors used, which constitute extremely bulky elements, require heliostat tracking on mirrors representing the whole capture surface, are very fragile and particularly expensive, and lose a non-negligible amount of energy, about 10% to 15%, since the light rays have to pass through large glass panes, causing harmful optical aberrations. The application US20110088694a1 highlights the importance of tilting the facets distributed on the annular envelope and the person skilled in the art never ignores these features in order to maintain a planar main collector solution.

Therefore, the known solutions require a strong and expensive infrastructure, requiring a large and expensive infrastructure and installation logistics, and their heliostats also require very expensive and powerful automation systems, in particular using a plurality of computers and control/rotation devices that require continuous maintenance.

Exposure to severe weather limits the lifetime of these concentrators, which are very expensive to replace or maintain and require periodic cleaning with large amounts of water, which is unacceptable especially in desert environments.

Furthermore, focusing devices made of materials of the prior art exhibit an undesirable achromatic effect due to the fact that the angle of refraction of the light rays by the lens or optical system depends on their wavelength, which leads to a magnification of the image that can only be corrected by adding correction optics. The result is that such a focusing device is relatively complex and allows a lower transmission efficiency of solar radiation compared to a focusing device using the flat mirrors and static mirrors proposed by the present invention. In addition, a non-negligible partial loss of radiation was found to occur as the radiation passed through the material of the optical device.

The solution provided by the invention

To remedy these drawbacks, the invention relates in its most general sense to a solar concentrator comprising at least one reflective first primary collector, called "sensor", which is planar and static, ideally mounted perpendicular to the zenith or to the high position of the sun, pre-focused via suitable optical means (for example of the fresnel type) towards a very small-sized secondary collector, called "concentrator", which concentrates the light and returns it to a capture or energy conversion unit.

The concentrator is characterized in that the reflecting surface is deformable to ensure the necessary optical correction or adjustment. The concentrator is arranged on a frame that can be moved in one or more dimensions, which allows heliostat tracking and return of the concentrated solar flux to any target integrated into the structure, for example located at the center of the sensor, or otherwise remote.

The optical assembly thus formed allows capture and concentration of solar energy in excess of 900W/m2 on the earth's surface, and more outside the earth's atmosphere. For example, due to simple unwinding of the self-adhesive film roll or assembly of the self-supporting structure, installation is rapid and production is very inexpensive.

The present invention relates to a two-stage solar concentrator. The first stage includes a first primary collector that pre-focuses light toward a secondary collector.

The second secondary collector constitutes a second stage for concentrating light in the direction of the energy conversion unit.

The essential features relate to the fact that: the primary collector is planar and static, and is in particular constituted by one of a flexible or rigid engraved or embossed film.

Detailed description of non-limiting examples of the invention

The invention will be better understood from a reading of the following detailed description of non-limiting examples of the invention with reference to the attached drawings, in which:

figure 1 shows an overall view of the device according to the invention.

In the following description it is explicitly pointed out that one or more of the following features may be employed alone or in any technically possible combination.

Schematic description of architecture

Fig. 1 very schematically shows the overall architecture of a solar concentrator according to a non-limiting example of the present invention.

The architecture comprises a planar primary sensor 1 arranged on a support 7. The planar sensor concentrates the light beam and returns it to the secondary concentrator 2, which secondary concentrator 2 in turn returns the solar energy to a target orheat collecting element 3 comprising, for example, a heat sink. The secondary concentrator 2 is supported by a frame 4, which frame 4 ensures its orientation based on the time of the year and day.

Description of the Sensors

The sensor constitutes 100% of the capture surface, which is primarily characterized as planar and static, and has a reflectivity that can be greater than 98%. The sensor collects the solar flux and pre-focuses it. One of the main advantages of the present invention is that the capture surface can be perfectly optimized because the shape of the surface is not circular, but square or rectangular.

This may desirably be formed from, for example, a flexible film 1, such as poly (ethylene-co-tetrafluoroethylene), more commonly abbreviated ETFE. This is a thermoplastic fluoropolymer which is an ethylene/tetrafluoroethylene alternating copolymer or any other suitable substrate, whatever it may be.

ETFE is lighter than glass (d ═ 2.5) and its cost is as low as 70% of that of glass. ETFE is capable of supporting 400 times its weight and exhibits high abrasion resistance, and can be used over a wide temperature range (from-80 ℃ to 155 ℃). ETFE is not a composite material, but is also recyclable and injectable. Furthermore, this material has a long life of more than 40 years.

The flexible or rigid film 1, for example made of ETFE, has a prismatic surface structure to form, for example, a fresnel type structure. The thickness of the membrane 1 is generally between 200 and 400 microns, but may have any type of thickness as required, and the membrane 1 may be covered at its lower part with a self-adhesive layer to facilitate its fixation on the support.

The sensor can easily consist of only a rigid structure which in particular can be self-supporting and thus form the roof, the assembly ideally being able to be made of recyclable and recyclable materials.

Ideally, the profile of the microstructure may preferably have broken prismatic ridges to form an optical device with several slopes of different angles, which makes it possible to increase the acceptance angle, which is originally about 60 ° and can be doubled by this method. The acceptance angle is a useful angle to capture the solar flux during its journey.

These microstructures are produced by mass production methods such as nanoimprinting, hot or cold molding or embossing, as well as, for example, many other techniques, the master itself can be produced using methods used in the industry such as semiconductor production (ICP etching and electron lithography) or any other suitable method, such as offset methods used in embossing, in particular a cylinder engraved with negative structures (embossed on the film in relief).

The microstructure of the sensor 1 is configured using software such as LightTools (trade name), for example.

The film 1 may be embossed or moulded in a mould to form a pattern of prisms in the base of the microstructure where incident solar flux is concentrated, or produced by any other suitable method such as etching or ablation.

In some cases, the focal point may advantageously be shifted by a certain angle to compensate for certain optical effects, to correct for high orientation angles with respect to the sun (very oblique or poorly oriented top/support), to increase the acceptance angle (so that the maximum useful angle of concentration can be fully exploited), to limit certain deformations or even to compensate for geometrical defects related to the travel of the sun and therefore to the focal point (the higher the angle of incidence, the greater the geometrical deformation of the focal point, so it can be expected to compensate for this effect by moving the focal point on either side of the zenith point).

Another solution that makes it possible to increase the acceptance angle and, in a related manner, the productivity comprises a prismatic structure or other method comprising a plurality of levels comprising one or more levels that capture and concentrate solar energy incident at an angle, for example, between 180 ° and 90 °, and one or more other levels having an angle value between 90 ° and 0 °.

Another advantageous alternative may include, for example, holograms/microbeads or other types of self-correcting or self-aggregating methods.

The surface of the fresnel type film is also desirably coated with:

an adhesive layer that allows the underlying layer to have excellent adhesion and good chemical insulation against corrosion or oxidation,

one or more reflective layers or dielectric coatings, for example formed by metallization, so that the IR/visible spectrum can be ideally covered;

a layer of optically transparent material making it possible to fill the interstices of the three-dimensional fresnel-type reflective optical microstructures, preventing them from being filled with optical and other contaminants, such as dust. The layer may also compensate for certain undesirable effects such as achromatization by virtue of its properties.

The different layers applied generate optical aberrations, refraction, partial reflection and other phenomena that impair the overall performance, which can be compensated in various ways or by adding one or more interfaces (layers, structures, reliefs, geometries, etc.) suitable to compensate these adverse effects.

The protective layer can be, for example, a simple varnish or any suitable coating, but it is preferably hard and chemically insulating, for example, produced from SiO2 or a ceramic deposit, the outer structure of the protective layer exposed to the open air being of the all-or ultra-all-phobic type (hydrophobic, oleophobic, etc.), this property being obtained, for example, via a microrelief or structure of suitable geometry, in order to avoid adhesion of elements that are detrimental to the optical properties, such as water, snow, frost, dust, drops, non-newtonian products and various pollutants, thus avoiding cleaning or maintenance of the sensor, and protecting the sensor from any chemical attack (for example: atmospheric pollutants), mechanical attack (for example: hail) or erosion (for example: sandstorms).

The omniphobic protective layer may be, for example, of the MOF (metal organic framework) type, or consist of a porous organometallic structure, which uses hydrocarbon bonds to connect metal ions in a multidimensional structure.

All the processes for manufacturing the film and its various constituent layers can be ideally carried out under ultra-vacuum on a wide-format machine that continuously unwinds, thus allowing high industrial productivity and very low production costs. In this case, the machine is ideally equipped with a process for cleaning the surface by ion bombardment or any method suitable for this purpose, which makes it possible to discharge any contaminants that are detrimental to the manufacturing quality of the layers.

The membrane 1 is fixed by gluing or any other method on a rigid support 7, the rigid support 7 being preferably planar and slightly inclined. The rigid support may be constituted by a flattened and compressed slab of sand or cement, or an assembly of metal sheets or glass roofs, such as in a greenhouse, or even by a system for tensioning the membrane 1 or a photovoltaic structure, the inefficiencies of which would be advantageously replaced by the present invention.

The support 7 desirably has a slight slope of at least several degrees to allow for drainage of rain and other contaminants, such as dust.

Description of an aggregator

The concentrator receives a pre-concentrated solar flux from a sensor whose focus moves according to the travel of the sun. The concentrator acts as a heliostat and returns the pre-concentrated solar flux to the target after correcting certain optical concentration defects. The necessary optical corrections come from the geometry of the sensor structure, which generates optical deformations that are detrimental to obtaining a high quality focus, but also from defects originating from irregularities in the support of the sensor. Correction may also be necessary when the sensor is, for example, square and the receiver is another shape (e.g., circular).

According to different variants, the concentrator according to the invention has one or more of the following features taken in any combination: the concentrator is deformable under the action of one or more actuators or equivalent means in order to ensure dynamic compensation.

The concentrator may comprise secondary compensation means constituted by any actuator means, such as a motor acting on the entire surface of the secondary optics through one or more axes. The deformation of the concentrator makes it possible to optimize the focus on the target to adjust the necessary power, in particular by zooming in or out it.

The concentrator is arranged on a frame allowing for sun tracking.

The frame has movable supports of the hoop type hinged along one or more axes and optionally translation means, which may be of the movable carriage type, supporting the secondary optics, to compensate for the annual and daily amplitude and variations due to certain factors, such as the wind.

The frame has arms controlled by one or more actuators, the movement of which is controlled by suitable control means.

The concentrator may desirably comprise a camera or any sensor suitable for acquiring a solar image formed on the heat collecting element, absorber or target, and wherein the frame comprises one or more actuators, for example controlled by a computer optionally comprising means for analysing the focused image to recalculate the position of the carrier, and optionally comprising other functions such as temperature or focused image control, or even safety concealment means. Also, the actuator may be controlled by a suitable mechanical device.

The concentrator may inject the super-concentrated luminous flux into an optical fiber or a bundle of dedicated solar fibers that transmit the light energy to a target or remote thermal converter.

The concentrator 2 may consist of several different mirrors (several concentrators in series) so that complex motions to the target can be generated or a set of concentrators.

The heliostat may include one or more supports disposed near or remote from the sensor, driven by suitable means, such as micromotors, positioners, jacks, reducers, mechanical devices and any automated or non-automated methods. In the best version, the heliostat may comprise or consist of a single arm supporting the secondary optics, which is moved by means of a device on one or more axes and fixed on suitable supports, the whole being able to receive the position, safety, stop or offset sensors and to be set in a safe position during extreme weather conditions, installation or maintenance.

This arm or any support may optionally contain and protect the control cable and other cables or components or devices or fluids of the adaptive optics (such as a coolant or air stream or cleaning fluid intended to protect and cool the optical surface).

The arm or the concentrator assembly may advantageously have an adjustment axis or an additional automatic or non-automatic axis, so that seasonal variations may be followed and corrections performed depending on geographical location. The device is particularly suitable for equipping satellites, space stations or spacecraft.

At the end of the arm is an adaptive optics assembly of the concentrator whose mirror comprises a very highly reflective surface for the desired wavelength, for example of the dielectric or multi-dielectric type, which is able to withstand the intense solar flux from the sensor and is protected in various ways from external aggressions such as dust, pollutants, meteorological elements, etc.

An advantage of adaptive optics is the ability to modify the final focus and correct any defects or aberrations as required. If starting with a circular sensor, the primary focus will also be circular when it is perpendicular to the normal (the sun at the zenith of the equator). When the sun is at grazing incidence (tangential to the normal), the optical aberrations distort the focus, which becomes a more or less elongated ellipsoid. Such deformations may impair the quality of the final focus and may even impair the receiver or the target intended to receive the concentrated energy.

The adaptive optics thus absorbs these aberrations and corrects them by modifying the predicted or non-predicted evolving deformation caused by the deformable mirror. The mirror is designed in a suitable material (or set of materials), has a very low thickness, is able to receive the reflective substrate and undergoes more or less significant deformation. The use of thin materials with high thermal conductivity allows any possible temperature increase that is prone to degrade or damage the deformable mirror and its supports, which are able to receive thermal drains and temperature maintenance or stabilization means, to be easily drained.

The concentrator 2 can also be constituted by an assembly of deformable mirrors or mirrors with a corolla or rigid circular sector, the inclination of which allows to change the focus.

The deformable mirror may take different shapes, circular, square or other, and may be one piece or be made up of multiple elements that are relatively soft or flexible to enable reversible deformation at large angles, allowing a high quality focus to be obtained.

The deformable mirror is actuated by suitable means, called actuators, which act on the structure of the mirror to obtain the desired result. These actuators can be produced in various ways and according to various methods, such as: piezoceramic, micromotor, electromagnet, jack and any mechanical device that makes it possible to act on the mirror temporarily or continuously, and can be a set of methods and techniques that achieve the final aim.

The deformable mirror assembly may be equipped with sensors and control elements so that a number of parameters may be checked, such as: temperature rise, reflectivity level, dimensional control, actuator position, testing, geometric deformation, geometric correction, control, and focus correction.

The deformable mirror and heliostat assembly and all accessories may be independently powered via any PV or other type of method, or may be powered by a remote control and steering station.

The deformable mirror assembly and its accessories are protected in a dome or other type of device having a geometry adapted to the assembly, or the device may have any shape, such as a flower shape. The protection device comprises a deformable mirror, its actuators, possible control or command electronics and one or more protection devices, such as a shutter (shutter) or a device intended to generate an air flow that protects and possibly cools the mirror.

The dome or protection device can also house certain control and command elements intended to check certain parameters related to the sensor, in particular its geometry, general surface condition, reflectivity, quality of the primary focus or presence or absence of foreign elements (snow, drippings, pollutants, objects, animals, etc.).

The dome or guard may optionally be oriented in one or more axes as desired, for example to protect the assembly during special conditions (snow, hail, sand storm, work, test, maintenance, etc.), or to hit a target at a particular angle or orientation. The dome or guard may also support other mirrors, which may be fixed or movable and may or may not be deformable for very specific needs.

The dome or protection device may also incorporate a set of sensors intended, for example, to control parameters of a target, weather control devices, or to scan the sky to predict cloudy channels or abnormal conditions requiring protection of components.

The dome or protection device may include a shutter or hiding mechanism that also acts as a safety device in the event of failure of the assembly and makes it possible to interrupt all or part of the solar flux from the sensor.

When power is exceeded, the deformable mirror of the concentrator can defocus the solar flux to avoid any overheating or even temporarily sending all or part of the flux to a surface outside the target.

The concentrator device is positioned either in the focus of the sensor or slightly out of focus, so that the optical flow, which may be disruptive, can be limited or geometric corrections can be facilitated.

The concentrator benefits from a method that allows for the correction of faults from sensors that may be mounted on a surface that is not perfectly flat.

The concentrator device 2 may advantageously be equipped with a spare mirror assembly that can be replaced manually or automatically in case of deterioration of the primary mirror, in order to avoid any intervention or interruption during solar energy production.

To avoid or limit any deterioration of the mirror, a peripheral protection, for example in the form of a cone, can be envisaged. The protection is also used to avoid burning birds or insects that may be present in the flux.

During strong winds or gusts, the support arm of the concentrator assembly may move or vibrate and thus lose the quality of the focus. However, the invention makes it possible to compensate in real time for large changes due to very short response times and large deformation amplitudes of the concentrating mirror, or even to anticipate any movement by applying the desired correction.

Furthermore, the device according to the invention may have a method that allows correction of chromatic aberrations due to the broad solar spectrum used, which method comprises forming a correcting optical layer or element of an achromatic or apochromatic group for the wavelength range, for example using optical doublets or elements of different refractive indices that compensate for the chromatic aberrations. The concentrator may ideally have a shape similar to the sensor, thereby optimizing the "active" surface and increasing the optical correlation with the sensor.

Claims (11)

1. A solar concentrator comprising at least one reflective or semi-reflective first primary collector (1) that pre-focuses light towards a heliostat secondary collector (2) that concentrates the light onto any target or energy conversion unit (3), characterized in that the primary collector (1) is planar and static.

2. A solar concentrator, the primary reflector of which is constituted by a flexible or rigid film that can be used as a support structure, which is engraved or embossed to form a fresnel-type optical structure that is reflected by metallization and fixed on a support (7).

3. A solar concentrator in which the surfaces of the primary and secondary reflectors are constructed of a self-cleaning omniphobic coating to prevent the deposition of particles such as water, dust and droplets that would otherwise impair optical performance and eliminate cleaning and therefore any water consumption.

4. A solar concentrator, wherein the primary and secondary reflectors are coated with a protective layer that prevents abrasion or corrosion and chemical attack, and the application of the protective layer allows filling of the prismatic cavities, thereby preventing the concentration of optical contaminants.

5. A solar concentrator according to claim 1, characterized in that the secondary concentrator (2) is supported by a frame (4), the frame (4) ensuring that the concentrator is displaced along one or more dimensions, allowing heliostat tracking.

6. Solar concentrator according to claim 1, characterized in that the secondary concentrator is of small size (1) and deformable under the action of one or more actuators controlled by a set of sensors and a computer to ensure dynamic optical correction, allowing perfect focusing on the target (.

7. A solar concentrator, the primary reflector of which comprises an additional optical structure, which can be of the prismatic type, enabling an increase in the solar acceptance angle and energy production efficiency.

8. A solar concentrator, the primary reflector of which can be semi-reflective to allow transmission of part of the light, in particular for greenhouses.

9. A solar concentrator according to claim 1, characterized in that the concentrator (3) comprises a solar optical fiber or fiber bundle that transmits highly concentrated light energy to any remote target or converter.

10. A planar and static solar concentrator, the shape of which, preferably square or rectangular, enables optimization of the solar collection surface, avoiding shadowing effects and limiting production and installation costs.

11. A planar and static solar concentrator whose sensors comprise a layer of optically transparent material, enabling the filling of the interstices of three-dimensional fresnel-type reflective optical microstructures, preventing their filling with optical and other contaminants, such as dust.

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