Combined cooling heating power Carnot battery energy storage system and methodTechnical Field
The invention relates to the technical field of energy storage, in particular to a combined cooling heating and power Carnot battery energy storage system and method for coupling liquefied natural gas vaporization.
Background
With the continuous advancement of technology, the energy industry is facing higher demands and challenges. Fossil fuels relied on the traditional energy system are not easy to store, and fluctuation intermittence of renewable energy sources such as solar energy, wind energy and the like causes great impact on the safety and stability of the power system. The rapid development of renewable energy sources makes energy storage technology particularly important so as to solve the problem of instability of intermittent renewable energy sources and ensure the sustainability of energy source supply. The energy storage technology stores and releases redundant energy when needed so as to smooth the load curve of the power network, reduce peak load, reduce energy waste and improve energy utilization rate.
At present, the main large-scale commercial energy storage technologies are pumped storage and compressed air storage, and the two technologies have the problems of geographical condition limitation, long construction period, high initial investment cost and the like. On a smaller scale, energy storage schemes such as supercapacitors, flywheels, batteries, and the like are applied. However, these energy storage schemes are more suitable for short charge-discharge cycles due to their higher cost per unit capacity and the inherent correlation between power and energy storage capacity.
In recent years, carnot cells have grown as a new type of thermomechanical energy storage technology. The Carnot battery is a novel energy storage technology based on thermoelectric conversion, is not limited by geographical conditions due to high energy conversion and flexible stability, can realize large-scale energy storage and the like, and provides an effective solution for high-efficiency utilization of new energy.
The Chinese patent document with the publication number of CN118687270A discloses a cascade heat pump Carnot battery energy storage system for combined cooling, heating and power, which comprises three subsystems of a cascade heat pump circulation unit, an organic Rankine circulation unit and a cold and heat storage unit, wherein when the electric quantity of a power grid is excessive, the cascade heat pump circulation unit converts electric energy into heat energy and cold energy at the same time and stores the heat energy and the heat energy into the cold and heat storage unit through a heat exchanger based on inverse Rankine circulation, a heat exchanger is arranged between the water heat and heat storage unit and the organic Rankine circulation unit, and when the electric quantity of the power grid is insufficient, the water heat and heat storage unit drives the organic Rankine circulation unit to generate electricity through the heat exchanger, meanwhile, the water heat storage tank can meet the conventional cold supply requirement, and the water heat storage tank can meet the industrial heat requirement.
The chinese patent document with publication number CN116247828B discloses an energy storage system of carnot battery and geothermal energy, which comprises a heat storage element, an electricity storage circulation system, a power generation circulation system and a geothermal heat exchange system, wherein in transitional seasons, the temperature fluctuation is large, low-temperature low-pressure liquid flows into the geothermal heat exchange system for heat exchange and heating in the charging process, the temperature is lower in winter, the soil temperature is relatively higher, and low-temperature low-pressure liquid flowing out from a decompression mechanism in the charging process flows into the geothermal heat exchange system for heat exchange and heating.
However, the existing Carnot battery energy storage technology has single energy utilization means, poor energy supply flexibility and high dependence on power grid buying electricity, so that the system has low circulation efficiency, low economy and long return on investment years.
Disclosure of Invention
The invention provides a combined cooling heating power Carnot battery energy storage system for coupling liquefied natural gas vaporization, which applies the liquefied natural gas (Liquefied Natural Gas, LNG) vaporization process to the Carnot battery energy storage system to construct a novel high-efficiency energy storage system capable of realizing combined cooling heating power supply so as to achieve the purposes of relieving peak load of a power grid, guaranteeing the stability of energy supply and the like.
The technical scheme of the invention is as follows:
A cogeneration carnot battery energy storage system comprising:
The two-stage heat pump circulation unit comprises a first-stage compressor (1), an LNG-heat pump working medium heat exchanger (2), a second-stage compressor (3), a combustion heater (4), a heat pump working medium-heat storage medium heat exchanger (5), a pressure reducing valve (6) and an evaporator (7) which are sequentially communicated end to end by pipelines to form closed circulation;
the heat storage circulation unit comprises a high-temperature pump (8), a high-temperature heat storage tank (9), a heat storage medium-working medium heat exchanger (10) and a heat storage tank (11) which are sequentially communicated end to end by pipelines to form closed circulation;
the Rankine cycle unit comprises an expander (12), a heat regenerator (13), a working medium-cold storage medium heat exchanger (14) and a working medium pump (15) which are sequentially communicated end to end by pipelines to form closed cycle;
The cold accumulation circulation unit comprises a cold accumulation tank (16), an LNG-cold accumulation medium heat exchanger (17), a low-temperature pump (18) and a low-temperature cold accumulation tank (19) which are sequentially communicated end to end by pipelines to form closed circulation;
The LNG vaporization utilization unit comprises an LNG storage tank (20), an LNG pump (21), an LNG expander (22) and a natural gas pipe network (23) which are sequentially connected in series through pipelines.
Preferably, in the heat storage circulation unit, an outlet of the heat storage tank (11) is connected with a cold end inlet of the heat pump working medium-heat storage medium heat exchanger (5), and a cold end outlet of the heat pump working medium-heat storage medium heat exchanger (5) is connected with an inlet of the high-temperature pump (8).
Preferably, in the rankine cycle unit, the cold end outlet of the regenerator (13) is connected with the cold end inlet of the heat storage medium-working medium heat exchanger (10), and the cold end outlet of the heat storage medium-working medium heat exchanger (10) is connected with the inlet of the expander (12).
Preferably, in the cold accumulation circulation unit, an outlet of the low-temperature cold accumulation tank (19) is connected with a cold end inlet of the working medium-cold accumulation medium heat exchanger (14), and a cold end outlet of the working medium-cold accumulation medium heat exchanger (14) is connected with an inlet of the cold accumulation tank (16).
Preferably, in the LNG vaporization utilization unit, an outlet of an LNG pump (21) is connected with a cold end inlet of the LNG-cold storage medium heat exchanger (17), the cold end outlet of the LNG-cold storage medium heat exchanger (17) is connected with a cold end inlet of the LNG-heat pump working medium heat exchanger (2), the cold end outlet of the LNG-heat pump working medium heat exchanger (2) is connected with an inlet of an LNG expansion machine (22), one path of the outlet of the LNG expansion machine (22) is connected with a natural gas pipe network (23), and the other path of the outlet of the LNG expansion machine is connected with a combustion heater (4).
In the two-stage heat pump circulation unit, an outlet of the primary compressor (1) is connected with a hot end inlet of the LNG-heat pump working medium heat exchanger (2), an outlet of the hot end of the LNG-heat pump working medium heat exchanger (2) is connected with an inlet of the secondary compressor (3), an outlet of the secondary compressor (3) is connected with a heating inlet of the combustion heater (4), a heating outlet of the combustion heater (4) is connected with a hot end inlet of the heat pump working medium-heat storage medium heat exchanger (5), an outlet of the heat pump working medium-heat storage medium heat exchanger (5) is connected with an inlet of the pressure reducing valve (6), an outlet of the pressure reducing valve (6) is connected with an inlet of the evaporator (7), and an outlet of the evaporator (7) is connected with an inlet of the compressor (1) so as to form a closed circulation.
In the heat storage circulation unit, an outlet of a heat storage tank (11) is connected with a cold end inlet of a heat pump working medium-heat storage medium heat exchanger (5), a cold end outlet of the heat pump working medium-heat storage medium heat exchanger (5) is connected with an inlet of a high-temperature pump (8), an outlet of the high-temperature pump (8) is connected with an inlet of a high-temperature heat storage tank (9), an outlet of the high-temperature heat storage tank (9) is connected with a hot end inlet of a heat storage medium-working medium heat exchanger (10), and a hot end outlet of the heat storage medium-working medium heat exchanger (10) is connected with the inlet of the heat storage tank (11) so as to form a closed cycle.
In the Rankine cycle unit, a cold end outlet of a heat regenerator (13) is connected with a cold end inlet of a heat storage medium-working medium heat exchanger (10), the cold end outlet of the heat storage medium-working medium heat exchanger (10) is connected with an inlet of an expander (12), an outlet of the expander (12) is connected with a hot end inlet of the heat regenerator (13), a hot end outlet of the heat regenerator (13) is connected with a hot end inlet of a working medium-cold storage medium heat exchanger (14), a hot end outlet of the working medium-cold storage medium heat exchanger (14) is connected with an inlet of a working medium pump (15), and an outlet of the working medium pump (15) is connected with the cold end inlet of the heat regenerator (13) to form a closed cycle.
In the cold accumulation circulation unit, an outlet of a cold accumulation tank (16) is connected with a hot end inlet of an LNG-cold accumulation medium heat exchanger (17), an outlet of the hot end of the LNG-cold accumulation medium heat exchanger (17) is connected with an inlet of a low-temperature pump (18), an outlet of the low-temperature pump (18) is connected with an inlet of a low-temperature cold accumulation tank (19), an outlet of the low-temperature cold accumulation tank (19) is connected with a cold end inlet of the working medium-cold accumulation medium heat exchanger (14), and a cold end outlet of the working medium-cold accumulation medium heat exchanger (14) is connected with the inlet of the cold accumulation tank (16) so as to form a closed cycle.
In the LNG vaporization utilization unit, LNG is stored in an LNG storage tank (20), an outlet of the LNG storage tank (20) is connected with an inlet of an LNG pump (21), an outlet of the LNG pump (21) is connected with an inlet of a cold end of an LNG-cold storage medium heat exchanger (17), an outlet of a cold end of the LNG-cold storage medium heat exchanger (17) is connected with an inlet of a cold end of an LNG-heat pump working medium heat exchanger (2), an outlet of the cold end of the LNG-heat pump working medium heat exchanger (2) is connected with an inlet of an LNG expansion machine (22), one path of the outlet of the LNG expansion machine (22) is connected with a natural gas pipe network (23), and the other path of the outlet of the LNG expansion machine is connected with a combustion heater (4).
Preferably, the circulating working medium used by the two-stage heat pump circulating unit is R1234yf or R134a, and the evaporator (7) is used for evaporating by utilizing an air heat source.
Preferably, in the heat storage circulation unit, the heat storage tank (11) and the high-temperature heat storage tank (9) both use high-pressure water with the pressure not lower than 1MPa, the temperature of the high-pressure water in the heat storage tank (11) is 20-80 ℃, the temperature of the high-pressure water in the high-temperature heat storage tank (9) is 150-200 ℃, and the high-temperature pump (8) is used for compensating the pressure loss of the high-pressure water in the heat storage circulation flow.
Preferably, the circulating working medium used by the Rankine cycle unit is carbon dioxide, the condensed liquid carbon dioxide circulating working medium is pressurized to more than 8MPa by a working medium pump (15), and the temperature of the carbon dioxide entering the expander (12) is not lower than 150 ℃.
Preferably, the working medium used by the cold accumulation circulation unit is pressurized liquid carbon dioxide, the boiling point of the pressurized liquid carbon dioxide is not higher than 0 ℃, the temperature of the liquid carbon dioxide in the cold accumulation tank (16) is not higher than-20 ℃, the temperature of the liquid carbon dioxide in the low-temperature cold accumulation tank (19) is-50 to-100 ℃, and the low-temperature pump (18) is used for compensating the pressure loss of the liquid carbon dioxide in the cold accumulation circulation flow.
Preferably, the pressure of liquefied gas in the LNG vaporization utilization unit is 7-12 MPa after the liquefied gas is pressurized by an LNG pump (21), and the proportion of the natural gas entering the combustion heater (4) after the natural gas is expanded by an LNG expander (22) is not more than 20%.
The invention also provides a combined cooling heating power Carnot battery energy storage method, which comprises the following steps:
The two-stage heat pump circulation unit, the heat storage circulation unit, the cold storage circulation unit and the LNG vaporization utilization unit are operated in the electricity consumption valley period of the power grid;
And (5) operating the Rankine cycle unit in the peak period of power consumption of the power grid.
Preferably, the power consumption during the operation of the primary compressor (1) and the secondary compressor (3) is partially sourced from a power grid, and the power generated by the LNG expander (22) is used for compensating the power consumption of the rest part.
Preferably, the power generated by the LNG expander (22) during operation is used for compensating the power consumption of the high-temperature pump (8), the working medium pump (15) and the low-temperature pump (18), and the rest part of power is used for inputting into a power grid to stabilize the peak-valley power consumption requirement of the power grid.
Compared with the prior art, the invention has the beneficial effects that:
According to the invention, through coupling LNG cold energy and cascade utilization, the system can realize combined cooling, heating and refrigerating, namely, simultaneously provide power, heat supply and refrigeration, thereby remarkably improving the utilization efficiency of energy sources and having better economy. Meanwhile, the system is suitable for energy supply of multiple application scenes, reduces energy cost, and is beneficial to energy saving, carbon reduction and flexibility transformation of industry.
Drawings
FIG. 1 is a flow chart of a coupled LNG cogeneration Carnot battery energy storage system of the present invention;
FIG. 2 is a flow chart of the working state of the power grid in the electricity consumption valley period in the invention;
FIG. 3 is a flow chart of the working state of the power grid in the peak period of power consumption in the invention;
In the figure, a primary compressor, a2 LNG-heat pump working medium heat exchanger, a 3, a secondary compressor, a 4, a combustion heater, a 5, a heat pump working medium-heat storage medium heat exchanger, a 6, a pressure reducing valve, a7, an evaporator, an 8, a high-temperature pump, a 9, a high-temperature heat storage tank, a 10, a heat storage medium-working medium heat exchanger, an 11, a heat storage tank, a 12, an expander, a 13, a regenerator, a 14, a working medium-cold storage medium heat exchanger, a 15, a working medium pump, a 16, a cold storage tank, a 17, an LNG-cold storage medium heat exchanger, a 18, a low-temperature pump, a 19, a low-temperature cold storage tank, a 20, an LNG storage tank, a 21, an LNG pump, a 22, an expansion machine, a 23 and a natural gas pipe network are arranged.
Detailed Description
The invention will be described in further detail below with reference to the drawings and examples, it being noted that the examples described below are intended to facilitate an understanding of the invention and are not intended to limit the invention in any way.
A combined cooling, heating and power Carnot battery energy storage system for coupling LNG cold energy is shown in figure 1 and comprises a two-stage heat pump circulation unit, a heat storage circulation unit, a Rankine circulation unit, a cold storage circulation unit and an LNG cold energy utilization unit.
The two-stage heat pump circulation unit is formed by sequentially connecting a first-stage compressor 1, an LNG-heat pump working medium heat exchanger 2, a second-stage compressor 3, a combustion heater 4, a heat pump working medium-heat storage medium heat exchanger 5, a pressure reducing valve 6 and an evaporator 7 in series. In the two-stage heat pump circulation unit, after the heat pump working medium is compressed and pressurized by the first-stage compressor 1, heat is released in the LNG-heat pump working medium heat exchanger 2, the cooled heat pump working medium is subjected to secondary compression by the second-stage compressor 3, the boosted high-pressure heat pump working medium absorbs heat energy by the combustion heater 4, and is subjected to condensation and heat release by the heat pump working medium-heat storage medium heat exchanger 5, and then is decompressed by the decompression valve 6, and the environment heat source is absorbed by the evaporator 7 to be vaporized, so that the heat pump working medium enters the first-stage compressor 1 to perform a new round of two-stage heat pump circulation unit.
The heat storage circulation unit is formed by sequentially connecting a high-temperature pump 8, a high-temperature heat storage tank 9, a heat storage medium-working medium heat exchanger 10, a heat storage tank 11 and a heat pump working medium-heat storage medium heat exchanger 5 in series. In the heat storage circulation unit, heat storage medium in the heat storage tank 11 exchanges heat in the heat pump working medium-heat storage medium heat exchanger 5, so that heat energy is obtained, and the heat energy is stored in the high-temperature heat storage tank 9 after being pressurized by the high-temperature pump 8. The heat storage medium in the high-temperature heat storage tank 9 realizes the release of heat energy in the heat storage medium-working medium heat exchanger 10. The cooled heat storage medium is stored in the heat storage tank 11, and a new heat storage cycle is performed. The high temperature pump 8 is used for compensating the pressure loss of the high pressure water in the heat storage circulation flow.
The Rankine cycle unit is formed by sequentially connecting a heat storage medium-working medium heat exchanger 10, an expander 12, a heat regenerator 13, a working medium-cold storage medium heat exchanger 14 and a working medium pump 15 in series. After a small amount of heat energy is absorbed by the liquid Rankine cycle working medium pressurized by the working medium pump 15 through the heat regenerator 13, the liquid Rankine cycle working medium is heated and vaporized in the heat storage medium-working medium heat exchanger 10 and then enters the expander 12 to perform isentropic expansion to realize the outward output of electric power, after the heat energy of part of the expanded working medium is released by the heat regenerator 13, the liquefied condensation is realized in the working medium-cold storage medium heat exchanger 14, and the condensed liquid working medium enters the working medium pump 15 to perform a new round of Rankine cycle.
The cold accumulation circulation unit is formed by sequentially connecting a cold accumulation tank 16, an LNG-cold accumulation medium heat exchanger 17, a low-temperature pump 18, a low-temperature cold accumulation tank 19 and a working medium-cold accumulation medium heat exchanger 14 in series. In the cold accumulation circulation unit, the liquid cold accumulation medium in the low-temperature cold accumulation tank 19 releases cold energy in the working medium-cold accumulation medium heat exchanger 14, the warmed liquid cold accumulation medium is stored in the cold accumulation tank 16, and cold energy is acquired in the LNG-cold accumulation medium heat exchanger 17, so that a new round of rankine cycle is performed. The cryopump 18 is used to compensate for the pressure loss of the liquid carbon dioxide in the cold storage circulation flow.
The LNG vaporization utilization unit is formed by sequentially connecting an LNG storage tank 20, an LNG pump 21, an LNG-cold storage medium heat exchanger 17, an LNG-heat pump working medium heat exchanger 2, an LNG expander 22 and a natural gas pipe network 23 in series. In the LNG vaporization utilization unit, LNG in an LNG storage tank 20 is pressurized by an LNG pump 21 and then released in an LNG-cold storage medium heat exchanger 17, vaporized natural gas absorbs heat in an LNG-heat pump working medium heat exchanger 2, the warmed natural gas carries out external output of electric energy in an LNG expander 22, the electric energy is used for partial power consumption of a primary compressor 1 and a secondary compressor 3 which work simultaneously therewith, the expanded natural gas is conveyed in a natural gas pipe network 23, and no more than 20% of natural gas enters a combustion heater 4 for combustion heating.
When LNG in the LNG storage tank (20) is input into the system at the flow rate of 5t/h, the low-temperature cold storage medium at-50 ℃ in the cold storage tank (16) can be cooled to-100 ℃ at 10t/h and stored in the low-temperature cold storage tank (19), the COP of the two-stage heat pump circulation unit reaches 3.8, and meanwhile, the heat storage medium at 10 ℃ and 3.6t/h in the heat storage tank (11) can be heated to 160 ℃ and stored in the high-temperature heat storage tank (9).
The power consumption of the two-stage heat pump cycle, the heat storage cycle unit and the cold accumulation cycle unit is 120kW, the net output power of the Rankine cycle unit is 101kW, the net output power of the LNG vaporization utilization unit is 89kW, and the comprehensive performance index is up to 3.258.
And when the power grid is in a low electricity consumption period, the two-stage heat pump circulation unit, the heat storage circulation unit, the cold storage circulation unit and the LNG vaporization utilization unit are operated, and the system stores energy, as shown in figure 2.
When the two-stage heat pump circulation unit works, the first-stage compressor 1 compresses a low-pressure heat pump working medium into high pressure. The high-pressure heat pump working medium releases heat in the LNG-heat pump working medium heat exchanger 2, and the LNG is preheated. The secondary compressor 3 further compresses the heat pump working medium to raise the temperature and pressure thereof. The combustion heater 4 provides additional heat energy to heat the high-pressure heat pump working medium. In the heat pump working medium-heat storage medium heat exchanger 5, the heat pump working medium transfers heat to the heat storage medium. The pressure reducing valve 6 reduces the pressure of the heat pump working medium in preparation for its absorption of ambient heat sources in the evaporator 7. The evaporator 7 utilizes an air heat source to evaporate the heat pump working medium to complete the circulation.
When the heat storage circulation unit works, the high-temperature pump 8 pressurizes the pressurized water heated in the heat pump working medium-heat storage medium heat exchanger 5 and conveys the pressurized water to the high-temperature heat storage tank 9 for storage.
When the cold accumulation circulation unit works, the low-temperature pump 18 pressurizes the low-temperature liquid carbon dioxide cooled in the LNG-cold accumulation medium heat exchanger 17 and conveys the low-temperature liquid carbon dioxide to the low-temperature cold accumulation tank 19 for storage.
When the LNG vaporization utilization unit is operated, LNG in the LNG tank 20 is pressurized by the LNG pump 21. In the LNG-cold storage medium heat exchanger 17, LNG releases cold energy, cooling the cold storage medium. LNG expander 22 expands the high pressure natural gas and the generated power is used to compensate for system power consumption.
During peak power grid use, the system operates primarily the rankine cycle unit to provide power, as shown in fig. 3.
In the heat storage medium-working medium heat exchanger 10, the liquid carbon dioxide absorbs heat and is converted into high-temperature and high-pressure gas. The LNG expander 12 performs work by expanding high-temperature and high-pressure carbon dioxide to generate electric power. In the regenerator 13, the carbon dioxide releases part of the heat and the temperature is lowered. In the working medium-cold storage medium heat exchanger 14, the carbon dioxide releases the remaining heat and condenses into a liquid state. The liquid carbon dioxide is pressurized by the working medium pump 15 to complete the cycle. During peak hours, the power generated by the LNG expander 12 may compensate for the power consumption of the system and input excess power into the power grid to meet the high load demands of the grid.
The foregoing embodiments have described the technical solutions and advantages of the present invention in detail, and it should be understood that the foregoing embodiments are merely illustrative of the present invention and are not intended to limit the invention, and any modifications, additions, substitutions and the like that fall within the principles of the present invention should be included in the scope of the invention.