A heat pump energy storage system for combined heat and power

Abstract

The present invention discloses a heat pump energy storage system for combined heat and power supply, which is characterized by comprising a high-temperature heat pump system, an energy storage system, a power generation system and a first heat pump system. The high-temperature heat pump system includes a first motor, an expander, a compressor, a heat exchanger, a recuperator and an absorber. The energy storage system includes a high-temperature heat storage tank, a high-temperature cold storage tank and a steam generator. The power generation system includes a generator, a steam turbine, a condenser and high and low pressure heaters. The high-temperature heat pump is connected to the energy storage system through the heat exchanger. The power generation system and the energy storage system are connected through the steam generator. The high-temperature heat pump system is connected to the power generation system through the first heat pump system. The present invention couples the high-temperature heat pump system, the energy storage system and the power generation system with each other, completes the storage and cascade utilization of heat in the process of electric-thermal-electric conversion, realizes combined heat and power supply, achieves the purpose of improving the energy utilization rate of the system, and has the advantages of high stability, no special geographical conditions requirements, long service life and low operation cost.

Description

Technical Field

[0001] The present invention belongs to the field of energy storage, and particularly relates to a heat pump energy storage system for combined heat and power supply. Background Art

[0002] Under the background of "dual carbon", renewable energy power generation technologies such as photovoltaic power generation and wind power generation have been continuously developing and growing, and the demand for energy storage is becoming increasingly strong. At present, the main forms of large-scale energy storage include pumped storage, compressed air energy storage, and chemical energy storage, etc.

[0003] Both pumped storage and compressed air energy storage utilize physical potential energy to achieve energy storage, with relatively high efficiency, but they require specific geographical conditions, such as lakes with a certain height difference and large-scale underground salt caverns, abandoned mine shafts, etc. Otherwise, the construction cost and cycle will increase significantly, and the energy storage cannot meet the requirements of flexible and low-cost application. While the cost of lithium battery energy storage is high, the service life is short, and there are safety risks.

[0004] "Carnot battery" is a new concept of energy storage developed in recent years. Its essence is that during charging, electricity is converted into heat for storage, and during discharging, the stored heat is converted into electricity through a heat engine driving a generator. Heat pump energy storage is a typical "Carnot battery" technology, but the energy utilization efficiency of existing heat pump energy storage technologies is less than 60%. If high efficiency is to be achieved, higher technical requirements are put forward for equipment such as compressors, turbines, and heat exchangers. Summary of the Invention

[0005] The present invention provides a heat pump energy storage system for combined heat and power supply, in which a high-temperature heat pump system, an energy storage system, and a power generation system are coupled with each other. Since the COP of the high-temperature heat pump is greater than 1 and its performance is superior to that of resistance heating technology, and then the economical valley electricity and the waste heat of the steam power generation system are used to provide energy for the high-temperature heat pump. Therefore, the energy storage system can efficiently heat the heat storage medium and store heat, and the power generation system is used to convert the heat energy into electrical energy to achieve combined heat and power supply, so as to achieve the purpose of improving the energy utilization efficiency of the system.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A heat pump energy storage system for combined heat and power supply, comprising a high-temperature heat pump system, an energy storage system, a power generation system, and a first heat pump system,

[0008] The high-temperature heat pump system includes a first motor, an expander, a compressor, a heat exchanger, a regenerator, and a heat absorber. The first motor, the expander, and the compressor are coaxially arranged. The first working fluid flows through the high-temperature side of the heat exchanger and the high-temperature side of the regenerator after exiting the compressor, enters the expander, and then flows through the low-temperature side of the heat absorber and the low-temperature side of the regenerator after exiting the expander, and returns to the compressor;

[0009] The power generation system includes a generator, a steam turbine, a condenser, a steam generator, and a first heating device. The generator is connected to the steam turbine. The steam working medium flows through the condensation side of the condenser, the first heating device, and the evaporation side of the steam generator after exiting the steam turbine, and then enters the steam turbine.

[0010] The energy storage system includes a high-temperature heat storage tank and a high-temperature cold storage tank. The heat storage medium in the high-temperature heat storage tank enters the high-temperature cold storage tank through the high-temperature side of the steam generator. The heat storage medium in the high-temperature cold storage tank enters the high-temperature heat storage tank through the low-temperature side of the heat exchanger.

[0011] The first heat pump system includes a first heat pump, a second motor, a first low-temperature heat storage tank, and a first low-temperature cold storage tank. The second motor is connected to the first heat pump, and the condensation side of the first heat pump is communicated with the high-temperature side of the heat absorber.

[0012] The second working medium in the first low-temperature heat storage tank flows through the evaporation side of the first heat pump, the first low-temperature cold storage tank, and the cold side of the condenser, and then returns to the first low-temperature heat storage tank. The second working medium is preferably water.

[0013] A high-temperature heat pump system, an energy storage system, and a power generation system are provided. Inexpensive valley electricity is used to provide energy for the high-temperature heat pump. The heat energy generated by the compressor in the high-temperature heat pump is transferred to the energy storage system through a heat exchanger for storage. The energy of the energy storage system generates superheated steam through a steam generator, and the superheated steam drives the steam turbine to do work and drive the generator to generate electricity, realizing the storage of heat during the electricity-thermal-electricity conversion process.

[0014] Under normal circumstances, the first working medium flowing out of the expander in the high-temperature heat pump system needs to be gradually heated before entering the compressor. Generally, it needs to be heated at a low temperature by a heating device and then enter the regenerator. In this embodiment, a heat absorber is designed before entering the regenerator. The low-temperature side of the heat absorber participates in the cycle of the high-temperature heat pump system. The high-temperature side of the heat absorber is connected to the power generation system through the first heat pump system. The waste heat in the power generation system is stored through the first low-temperature heat storage tank, further circulated and heated by the first heat pump, and transferred to the third working medium. The heated third working medium releases heat on the high-temperature side of the heat absorber. After the first working medium on the low-temperature side of the heat absorber absorbs the heat, it then enters the low-temperature side of the regenerator. Therefore, setting the first heat pump can increase the heat absorption temperature of the high-temperature heat pump and improve the COP of the high-temperature heat pump.

[0015] The heat pump energy storage system further includes a second heat pump, a third motor, a second low-temperature heat storage tank, and a second low-temperature cold storage tank. The third motor is connected to the second heat pump. The third working medium flows through the evaporation side outlet of the second heat pump, the condensation side of the first heat pump, and the high-temperature side of the heat absorber, and then returns to the evaporation side of the second heat pump.

[0016] The second low-temperature heat tank is connected to the second low-temperature cold tank through the condensation side of the second heat pump. The fourth working fluid flows out of the second low-temperature cold tank, flows through the condensation side of the second heat pump, and enters the second low-temperature heat tank for storage.

[0017] The purpose of setting the second heat pump is to use the high-temperature heat pump system to absorb the heat of the third working fluid as a low-temperature heat source, use the second heat pump cycle to raise the temperature of its low-temperature heat source, transfer it to the fourth working fluid, and store it in the first low-temperature heat tank. The fourth working fluid is preferably a water working fluid to achieve efficient heat supply or heating, etc., realize the cascaded utilization of energy, and greatly improve the energy utilization rate of the system.

[0018] The third working fluid circulating in the condensation side of the first heat pump, the evaporation side of the second heat pump, and the high-temperature side of the heat absorber is an organic working fluid or carbon dioxide.

[0019] The heat storage medium in the energy storage system is molten salt.

[0020] The energy storage system further includes a second heating device, which is arranged between the low-temperature side of the heat exchanger and the high-temperature heat tank to further heat the heat storage medium in the high-temperature heat tank.

[0021] The first working fluid in the high-temperature heat pump system is air, argon, helium or nitrogen.

[0022] Due to the adoption of the above technical solutions, the present invention has the following advantages and positive effects compared with the prior art:

[0023] In the embodiment of the present invention, cheap valley electricity is used to provide energy for the compressor in the high-temperature heat pump system. The high-temperature and high-pressure working fluid flowing out of the compressor releases heat through the high-temperature side of the heat exchanger, transfers the heat to the heat storage medium on the low-temperature side, and the heat storage medium that obtains the heat is stored in the high-temperature heat tank; the heat in the high-temperature heat tank is transferred to water through the steam generator to generate steam, and the steam drives the steam turbine to do work and the generator generates electricity. Since the COP (Coefficient of Performance, the COP of the heat pump refers to the ratio of the heat output that the heat pump can achieve to the input power, and the larger the value, the higher the efficiency and the more energy-saving the heat pump system) of the high-temperature heat pump is greater than 1, its performance is superior to the resistance heating technology. Therefore, by setting the high-temperature heat pump, it is possible to efficiently heat the heat storage medium and store heat using valley electricity, and achieve efficient utilization of energy.

[0024] In the embodiment of the present invention, an absorber is designed before entering the recuperator. The low-temperature side of the absorber participates in the cycle of the high-temperature heat pump system. The high-temperature side of the absorber is connected to the power generation system through the first heat pump system. The waste heat in the power generation system is stored through the first low-temperature heat storage tank and further circulated and heated by the first heat pump, and then transferred to the third working fluid. The heated third working fluid releases heat on the high-temperature side of the absorber, and the third working fluid on the low-temperature side of the absorber absorbs heat. Therefore, the embodiment of the present invention utilizes the waste heat of the power generation system as the low-temperature heat absorption heat source of the first heat pump, outputs a higher temperature through the first heat pump, provides a heat source with a higher temperature for the high-temperature heat pump system, thereby forming the storage and cascaded temperature rise utilization of the power generation cooling waste heat, and ensuring the efficient and stable operation of the system.

[0025] In the embodiment of the present invention, through the mutual coupling setting of the high-temperature heat pump system, the energy storage system, the power generation system and the first heat pump system, the storage and cascaded utilization of heat in the process of electric-thermal-electric conversion are completed, the combined heat and power supply is realized, and the purpose of improving the energy utilization rate of the system is achieved. It has the advantages of high stability, no special geographical conditions required, long service life and low operation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flow chart of a combined heat and power supply heat pump energy storage system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The following further details a combined heat and power supply heat pump energy storage system proposed by the present invention with reference to the drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer.

[0028] Refer to Figure 1 , a combined heat and power supply heat pump energy storage system, including a high-temperature heat pump system, an energy storage system, a power generation system and a first heat pump system,

[0029] The high-temperature heat pump system includes a first motor 3, an expander 2, a compressor 1, a heat exchanger 4, a recuperator 5, and an absorber 6. The first motor 3, the expander 2 and the compressor 1 can be coaxially connected or indirectly connected through devices such as a gearbox. The work done by the expander 2 can offset part of the energy consumption of the compressor 1;

[0030] The first working fluid flows through the high-temperature side 402 of the heat exchanger 4 and the high-temperature side 502 of the recuperator 5 after exiting the compressor 1, enters the expander 2, flows through the low-temperature side 602 of the absorber 6 and the low-temperature side 501 of the recuperator 5 after exiting the expander 2, and enters the compressor 1;

[0031] The first working fluid in the high-temperature heat pump system is air, argon, helium or nitrogen, preferably helium;

[0032] The power generation system includes a generator 18, a steam turbine 17, a condenser 19, and a first heating device 20. The generator 18 is connected to the steam turbine 17. The steam working medium flows through the condensation side 1901 of the condenser 19, the first heating device 20, and the evaporation side 1601 of the steam generator 16 from the outlet of the steam turbine 17, and then enters the steam turbine 17.

[0033] The energy storage system includes a high-temperature heat storage tank 8 and a high-temperature cold storage tank 9. The heat storage medium in the high-temperature heat storage tank 8 enters the high-temperature cold storage tank 9 through the high-temperature side 1602 of the steam generator 16. The heat storage medium in the high-temperature cold storage tank 9 enters the high-temperature heat storage tank 8 through the low-temperature side 401 of the heat exchanger 4.

[0034] The heat storage medium in the energy storage system is molten salt.

[0035] The first heat pump system includes a first heat pump 10, a second motor 3', a first low-temperature heat storage tank 11, and a first low-temperature cold storage tank 12. The second motor 3' is connected to the first heat pump 10. The condensation side 1002 of the first heat pump 10 is communicated with the high-temperature side 601 of the heat absorber 6. The third medium returns to the high-temperature side 601 of the heat absorber 6 through the condensation side 1002 of the first heat pump 10.

[0036] The second working medium in the first low-temperature heat storage tank 11 flows through the evaporation side 1001 of the first heat pump 10, the first low-temperature cold storage tank 12, and the cold side 1902 of the condenser 19, and then enters the first low-temperature heat storage tank 11.

[0037] Cheap off-peak electricity is used to provide energy for the compressor 1 in the high-temperature heat pump system. The high-temperature and high-pressure first working medium flowing out of the compressor 1 releases heat through the high-temperature side 402 of the heat exchanger 4, transfers the heat to the heat storage medium on the low-temperature side 401, and the heat storage medium that obtains the heat is stored in the high-temperature heat storage tank 8. The heat in the high-temperature heat storage tank 8 is transferred to water through the steam generator 16 to generate superheated steam, and the superheated steam drives the steam turbine 17 to do work, and the generator 18 generates electricity. Since the COP (Coefficient of Performance, the COP of the heat pump refers to the ratio of the heat output that the heat pump can achieve to the input power, and the larger the value, the higher the efficiency and the more energy-saving of the heat pump system) of the high-temperature heat pump is greater than 1, its performance is better than that of the resistance heating technology. Therefore, by setting up the high-temperature heat pump system, the efficient heating and storage of the heat storage medium using off-peak electricity is realized, and the efficient utilization of energy is achieved.

[0038] Under normal circumstances, the first working fluid flowing out of the expander 2 in the high-temperature heat pump system needs to be gradually heated before entering the compressor 1. Generally, it needs to be heated at a low temperature by a heating device and then enter the recuperator 5. In this embodiment, a heat absorber 6 is designed before entering the recuperator 5. The low-temperature side 602 of the heat absorber 6 participates in the cycle of the high-temperature heat pump system. The high-temperature side 601 of the heat absorber 6 is connected to the power generation system through the first heat pump system. The waste heat in the power generation system is stored in the first low-temperature heat storage tank 11, and further circulated and heated by the first heat pump 10, and transferred to the third working fluid. The heated third working fluid releases heat on the high-temperature side 601 of the heat absorber 6, and the first working fluid absorbs heat on the low-temperature side 601 of the heat absorber 6. Therefore, the first heat pump system is set up to store the waste heat of the power generation system in the first low-temperature heat storage tank 11. The first heat pump 10 further increases the heat and transfers it to the high-temperature heat pump system, providing a heat absorption heat source with a higher temperature for the high-temperature heat pump, improving the COP of the high-temperature heat pump, thereby forming the cooling waste heat storage and cascade temperature rise utilization of the power generation system, so as to ensure the efficient and stable operation of the system.

[0039] The heat pump energy storage system further includes a second heat pump 13, a third motor 3", a second low-temperature heat storage tank 14 and a second low-temperature cold storage tank 15. The third motor 3" is connected to the second heat pump 13. The third working fluid flows out of the evaporation side 1301 outlet of the second heat pump 13, flows through the condensation side 1002 of the first heat pump 10 and the high-temperature side 601 of the heat absorber 6, and returns to the evaporation side 1301 of the second heat pump 13;

[0040] The second low-temperature heat storage tank 14 is communicated with the second low-temperature cold storage tank 15 through the condensation side 1302 of the second heat pump 13. The fourth working fluid flows out of the second low-temperature cold storage tank 15, flows through the condensation side 1302 of the second heat pump 13, and enters the second low-temperature heat storage tank 14 for storage. Preferably, water is stored in the second low-temperature heat storage tank 14 and the second low-temperature cold storage tank 15. The cold water in the second low-temperature cold storage tank 15 enters the condensation side 1302 of the second heat pump 13 to absorb heat and enters the second low-temperature heat storage tank 14 for storage. The hot water in the second low-temperature heat storage tank 14 can be used as domestic hot water, heating, etc.

[0041] The purpose of setting the second heat pump 13 is to use the waste heat of the third working fluid after being absorbed by the high-temperature heat pump system as the low-temperature heat source of the fourth working fluid, and use the second heat pump 13 to circulate and increase the temperature of its low-temperature heat source, store it in the second low-temperature heat storage tank 14, realize efficient heat supply or heating, etc., realize the cascade utilization of energy, and greatly improve the energy utilization rate of the system.

[0042] The first heat pump 10 and the second heat pump 13 are conventional heat pumps. The circulating third working fluid on the condensation side 1002 of the first heat pump 10, the evaporation side 1301 of the second heat pump 13 and the high-temperature side 601 of the heat absorber 6 is an organic working fluid or carbon dioxide.

[0043] The energy storage system further includes a second heating device 7, which is arranged between the low-temperature side 401 of the heat exchanger 4 and the high-temperature heat storage tank 8 to further heat the heat storage medium flowing into the high-temperature heat storage tank 8 and improve the high-temperature heat storage temperature.

[0044] The working principle of the heat pump energy storage system with combined heat and power generation in this embodiment:

[0045] The heat storage medium in the energy storage system is molten salt, and the medium in the low-temperature cooling system is water.

[0046] During energy storage, the first motor 3 is used to drive the compressor 1 to compress the first circulating working medium (preferably argon) by using valley electricity or low-price electricity. The temperature of the circulating working medium at its outlet increases (to about 600 °C). The circulating working medium enters the high-temperature side 402 of the heat exchanger 4 to release heat, and its temperature decreases (to about 300 °C). Then it enters the high-temperature side 502 of the regenerator 5 for secondary heat release (the temperature decreases to about 100 °C). Then it enters the expander 2 to expand and do work, and its temperature further decreases (to about 5 °C). Then it enters the low-temperature side 602 of the heat absorber 6 to absorb low-temperature heat (about 90 °C), and then enters the low-temperature side 501 of the regenerator 5 to absorb heat, and then enters the compressor 1 to complete a high-temperature heat pump compression cycle.

[0047] During the high-temperature heat pump compression cycle, the low-temperature molten salt stored in the high-temperature cold storage tank 9 flows through the low-temperature side 401 of the heat exchanger 4 and exchanges heat with the high-temperature circulating first working medium (about 600 °C) on the high-temperature side 402 of the heat exchanger 4. The low-temperature molten salt is heated (to 580 °C) and flows into the high-temperature heat storage tank 8 for storage. The second heating device 7 can further heat the high-temperature molten salt flowing into the high-temperature heat storage tank 8 to improve the high-temperature heat storage temperature.

[0048] While the high-temperature heat pump compression cycle is in progress, the second motor 3' and the third motor 3" respectively drive the first heat pump 10 and the second heat pump 13 to operate. The hot water (35 °C) stored in the first low-temperature heat storage tank 11 flows through the evaporation side 1001 of the first heat pump 10. The hot water is cooled (to about 15 °C) after absorbing heat on the evaporation side 1001 and flows into the first low-temperature cold storage tank 12 for storage. Through the compression cycle of the first heat pump 10, the evaporation side 1001 of the first heat pump 10 absorbs the heat of the low-temperature hot water and releases heat on its condensation side 1002, that is, the third working medium absorbs heat on the condensation side 1002, increasing the temperature of the working medium entering the high-temperature side 601 of the heat absorber 6 (to about 90 °C) and improving the coefficient of performance (COP) of the high-temperature heat pump.

[0049] The third working fluid (~90 °C) releases heat through the high-temperature side 601 of the heat absorber 6 and then cools down (~40 °C). It then enters the evaporation side 1301 of the second heat pump 13 to absorb heat. The heat temperature is increased through the heat pump compression cycle, and heat is released from the condensation side 1302 of the second heat pump 13 to heat the water (~70 °C) from the second low-temperature cold tank 15 to (90 °C). The heated hot water enters the second low-temperature hot tank 14 for heat supply (such as heating, domestic hot water, etc.).

[0050] During power generation, the high-temperature molten salt stored in the high-temperature hot tank 8 flows through the high-temperature side 1602 of the steam generator 16. Through heat transfer, the high-pressure water (~230 °C) entering the evaporation side 1601 of the steam generator 16 is vaporized to form superheated steam (570 °C). The superheated steam enters the steam turbine 17 to drive it to do work, driving the generator 18 to generate electricity. The low-temperature steam (42 °C) discharged from the steam turbine 17 enters the condensation side 1901 of the condenser 19. At the same time, the low-temperature cooling water (~15 °C) stored in the first low-temperature cold tank 12 enters the cold side 1902 of the condenser 19. The low-temperature steam in the condensation side 1901 is isothermally cooled by the low-temperature water in the cold side 1902 to form condensed water (42 °C) and then enters the first heating device 20 for reheating, forming a Rankine power generation cycle. The low-temperature cooling water flowing out of the cold side 1902 of the condenser 19 is heated to (~35 °C) and enters the first low-temperature hot tank 11 for storage, serving as the low-temperature heat source for the high-temperature heat pump compression cycle.

[0051] The temperatures described in the above working process are for the convenience of explaining the working process and can be changed accordingly according to the actual situation in actual applications.

[0052] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, provided that these changes fall within the scope of the claims of the present invention and their equivalent technologies, they still fall within the protection scope of the present invention.

Claims

1. A combined heat and power heat pump energy storage system, characterized in that, It includes a high-temperature heat pump system, an energy storage system, a power generation system, and a first heat pump system. The high-temperature heat pump system includes a first motor, an expander, a compressor, a heat exchanger, a regenerator, and a heat absorber. The first motor, the expander, and the compressor are coaxially arranged. The first working fluid flows through the high-temperature side of the heat exchanger and the high-temperature side of the regenerator from the outlet of the compressor, enters the expander, flows through the low-temperature side of the heat absorber and the low-temperature side of the regenerator from the outlet of the expander, and returns to the compressor. The power generation system includes a generator, a steam turbine, a condenser, a steam generator, and a first heating device. The generator is connected to the steam turbine. The steam working fluid flows through the condensation side of the condenser, the first heating device, and the evaporation side of the steam generator from the outlet of the steam turbine, and returns to the steam turbine. The energy storage system includes a high-temperature heat storage tank and a high-temperature cold storage tank. The heat storage medium in the high-temperature heat storage tank enters the high-temperature cold storage tank through the high-temperature side of the steam generator. The heat storage medium in the high-temperature cold storage tank enters the high-temperature heat storage tank through the low-temperature side of the heat exchanger. The first heat pump system includes a second motor, a first heat pump, a first low-temperature heat storage tank, and a first low-temperature cold storage tank. The second motor is connected to the first heat pump. The condensation side of the first heat pump is communicated with the high-temperature side of the heat absorber. The second working fluid in the first low-temperature heat storage tank flows through the evaporation side of the first heat pump, the first low-temperature cold storage tank, and the cold side of the condenser, and returns to the first low-temperature heat storage tank.

2. The combined heat and power heat pump energy storage system according to claim 1, characterized in that, It further includes a second heat pump, a third motor, a second low-temperature heat storage tank, and a second low-temperature cold storage tank. The third motor is connected to the second heat pump. The third working fluid flows through the outlet of the evaporation side of the second heat pump, the condensation side of the first heat pump, and the high-temperature side of the heat absorber, and returns to the evaporation side of the second heat pump. The second low-temperature heat storage tank is communicated with the second low-temperature cold storage tank through the condensation side of the second heat pump. The fourth working fluid flows out of the second low-temperature cold storage tank, flows through the condensation side of the second heat pump, and enters the second low-temperature heat storage tank for storage.

3. The combined heat and power heat pump energy storage system according to claim 2, characterized in that, The third working fluid is an organic working fluid or carbon dioxide.

4. The combined heat and power heat pump energy storage system according to claim 2, characterized in that, The fourth working fluid is water.

5. The combined heat and power heat pump energy storage system according to claim 1, characterized in that, The second working fluid is water.

6. The combined heat and power heat pump energy storage system according to any one of claims 1 or 2, characterized in that, The heat storage medium in the energy storage system is molten salt.

7. The combined heat and power heat pump energy storage system according to any one of claims 1 or 2, characterized in that, The energy storage system further includes a second heating device, and the second heating device is arranged between the low-temperature side of the heat exchanger and the high-temperature heat storage tank.

8. The combined heat and power heat pump energy storage system according to any one of claims 1 or 2, characterized in that, The circulating first working fluid in the high-temperature heat pump system is air, argon, helium, or nitrogen.

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