An open supercritical carbon dioxide energy storage system and method of operation

Abstract

The application discloses an open supercritical carbon dioxide energy storage system and an operation method thereof, which comprises a thermal power plant unit, a supercritical carbon dioxide energy storage unit, a calcium carbonate heat storage unit and a microalgae unit; carbon dioxide discharged from the thermal power plant unit is used as a working medium of the supercritical carbon dioxide energy storage; the supercritical carbon dioxide energy storage unit can store surplus power during a wind energy and solar energy power generation peak period; the calcium carbonate heat storage unit can store compression heat in a compression process and solar heat, and the stored heat is used for preheating before supercritical carbon dioxide expansion; the microalgae unit can use the discharged carbon dioxide after work is finished as raw material of a microalgae reaction to generate biodiesel; during the wind energy and solar energy power generation peak period, the energy storage time can be prolonged, and the supercritical carbon dioxide can be sealed to the seabed, so that the problems of high carbon emission of the thermal power plant and randomness and fluctuation of the wind energy and the solar energy are solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of physical energy storage, and particularly relates to an open supercritical carbon dioxide energy storage system and an operation method thereof. BACKGROUND

[0002] Thermal power generation produces a large amount of carbon emissions. Data shows that the proportion of carbon dioxide emissions from thermal power generation is continuously high. Under the background of emission reduction, it is imperative to reduce the carbon emissions of the thermal power industry. On the one hand, the emitted carbon dioxide can be collected by carbon capture technology and stored (such as injected into the seabed or underground) or reused (such as fixed by plants or microorganisms through photosynthesis); on the other hand, small and old thermal power units can be eliminated, and renewable energy such as wind energy and solar energy can be used for power generation to reduce carbon emissions.

[0003] In order to achieve the carbon emission target, the installed capacity of renewable energy power generation is increasing year by year. However, renewable energy, especially wind power and photovoltaic power generation, has significant volatility and randomness. The energy storage system can store the excess power generated by wind and solar power during the low power consumption period, and release it during the peak power consumption period, helping the power grid to balance peak and valley, relieving the load pressure of the power grid, and improving the overall operation efficiency of the power grid. At the same time, without energy storage, when wind power and photovoltaic power generation exceed the receiving capacity of the power grid or the transmission channel limit, wind power or photovoltaic power may be forced to be abandoned. The energy storage system can store this part of energy that would otherwise be wasted, improving the actual utilization rate of renewable energy.

[0004] Supercritical carbon dioxide energy storage is a technology that uses supercritical state carbon dioxide as working medium for energy storage and conversion. When renewable energy such as wind and solar energy is at the peak of power generation period and power is abundant, the excess power is used to drive the compressor to compress the carbon dioxide at normal temperature and pressure to a supercritical state, and store it in a specially designed pressure vessel, and the energy storage stage is completed. When the power grid is at the peak of power consumption and the output of wind and solar energy is insufficient, the supercritical carbon dioxide is released into the expander, rapidly expands and does work, driving the generator to generate electricity, and the energy release stage is completed. Since a large amount of heat energy is generated during the compression process, the heat energy is usually stored through a heat exchanger and used to supplement the heat of carbon dioxide during the energy release process. The advantage is that compared with air, the supercritical carbon dioxide energy storage system has higher energy storage density and energy conversion efficiency, and carbon dioxide is non-toxic, non-flammable, and weakly corrosive to metals. In a closed cycle, it is not directly discharged to the atmosphere, which helps to reduce greenhouse gas emissions.

[0005] Microalgae diesel production technology is a green technology for converting solar energy and carbon dioxide into renewable fuel by using efficient photosynthetic organisms. The technology first needs to select or improve microalgae species with high oil content, rapid growth, easy cultivation and other excellent properties by genetic engineering from nature, and then cultivate the microalgae in a photobioreactor. When the microalgae reach a certain biomass and the oil accumulation reaches the peak, the microalgae biomass is harvested by physical or chemical methods. The harvested microalgae biomass is subjected to oil extraction and transesterification to produce biodiesel. The advantages of the technology are that the microalgae can absorb a large amount of carbon dioxide in the process of photosynthesis, which helps to reduce carbon emissions; the microalgae can be cultured in seawater and can tolerate desert, drought and other environments, and can be cultured in vertical space, so the land occupation is small; the produced biodiesel has a high heat value of about 80% of that of petrochemical fuel, and basically does not contain sulfur and aromatic hydrocarbons, so the combustion product pollution is small. SUMMARY

[0006] In order to solve the problems in the prior art, the present application provides an open supercritical carbon dioxide energy storage system and operating method, which combines carbon dioxide energy storage, microalgae diesel production technology and carbon dioxide seabed storage technology, uses carbon dioxide emitted by a thermal power plant as a working medium for energy storage, and solidifies the carbon dioxide through a microalgae reaction or transports the carbon dioxide to the seabed for storage, thereby achieving economic and environmental benefits.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: an open supercritical carbon dioxide energy storage system, comprising a thermal power plant unit, a supercritical carbon dioxide energy storage unit, a calcium carbonate heat storage unit and a microalgae unit.

[0008] A multi-stage compression energy storage unit and a multi-stage expansion energy release unit are arranged in the supercritical carbon dioxide energy storage unit, heat exchangers are arranged between the stages of the multi-stage compression energy storage unit, and a heat accumulator is arranged at the inlet of each stage of the multi-stage expansion energy release unit; the carbon dioxide outlet of the thermal power plant unit is connected to the multi-stage compression energy storage unit and the multi-stage expansion energy release unit in sequence; the calcium carbonate heat storage unit comprises a calcium carbonate reaction device, a solar heat collector and a calcium oxide reaction device; the cold side of the heat exchanger is connected to the calcium carbonate reaction device, and the solar heat collector is used to heat the calcium carbonate reaction device; the hot gas inlet and outlet of the calcium oxide reaction device are communicated with the hot side of the heat accumulator; the gas outlet of the microalgae unit is connected to the calcium oxide reaction device; and the gas outlet of the supercritical carbon dioxide energy storage unit is also communicated with the seabed.

[0009] Furthermore, the thermal power plant unit includes a boiler, a furnace-fed induced draft fan, and an absorption tower connected in sequence. The outlet of the absorption tower is connected to the gas inlet of the multi-stage compression energy storage unit in the supercritical carbon dioxide energy storage unit via a first inlet valve. The heat exchanger includes a first heat exchanger and a second heat exchanger. The multi-stage compression energy storage unit includes a first-stage compressor, a second-stage compressor, and a third-stage compressor. In the multi-stage compression energy storage unit, the first inlet valve, the carbon dioxide storage tank, the first exhaust valve, the first-stage compressor, the first heat exchanger, the second-stage compressor, the second heat exchanger, the third-stage compressor, the second inlet valve, and the supercritical carbon dioxide storage tank are connected in sequence along the gas flow direction. The power ends of the first-stage compressor, the second-stage compressor, and the third-stage compressor are connected to electric motors.

[0010] Furthermore, the heat accumulator includes a first heat accumulator, a second heat accumulator, and a third heat accumulator, and the multi-stage expander energy release unit includes a first expander, a second expander, and a third expander; in the multi-stage expander energy release unit: the cold side of the first heat accumulator, the first expander, the cold side of the second heat accumulator, the second expander, the cold side of the third heat accumulator, and the third expander are connected sequentially along the carbon dioxide flow direction, and the first expander, the second expander, and the third expander are connected to the first generator.

[0011] Furthermore, the hot gas inlet and outlet of the calcium oxide reaction device are respectively connected to the hot side of the first accumulator, the hot side of the second accumulator, and the hot side of the third accumulator.

[0012] Furthermore, the calcium carbonate reaction device is equipped with a heat exchange structure, a calcium oxide outlet, and a calcium carbonate inlet; the heat exchange structure is used to absorb the heat energy from the heat exchanger and the solar collector to heat the calcium carbonate; the microalgae unit includes a microalgae reaction chamber, a microalgae biomass treatment device, an internal combustion engine, a second generator, and a dehumidification device. The microalgae reaction chamber, the microalgae biomass treatment device, and the internal combustion engine are connected in sequence, and the gas outlet of the internal combustion engine is connected in sequence to the calcium oxide reaction device and the dehumidification device.

[0013] Furthermore, the supercritical carbon dioxide energy storage unit is equipped with a supercritical carbon dioxide storage tank. A second intake valve is installed on the intake pipe connected to the top of the supercritical carbon dioxide storage tank. The outlet of the multi-stage compressor unit is connected before the second intake valve. A second exhaust valve and a third exhaust valve are installed on the exhaust pipe connected to the bottom of the supercritical carbon dioxide storage tank. The second exhaust valve is connected to the multi-stage expander unit, and the third exhaust valve is connected to the pipeline leading to the seabed.

[0014] Furthermore, the calcium oxide reaction device is equipped with two sets of heat exchange structures and inlet / outlet ports. The first set of heat exchange structures exchanges heat with the exhaust gas of the internal combustion engine to bring the calcium oxide and carbon dioxide to the reaction temperature. The second set of heat exchange structures transfers the heat generated by the reaction of calcium oxide and carbon dioxide to the accumulator in front of the expander unit to heat the carbon dioxide. Calcium oxide and carbon dioxide are introduced through the inlet port.

[0015] The operation method of the open supercritical carbon dioxide energy storage system of the present invention includes: a pre-setting stage in which carbon dioxide generated by the absorption tower enters a multi-stage compressor unit and is compressed into supercritical carbon dioxide; and an energy storage stage in which heat is transferred to the calcium carbonate reactor through a heat exchanger during the carbon dioxide compression process.

[0016] During the energy release stage, supercritical carbon dioxide is heated by a thermal accumulator and then enters a multi-stage expander unit to generate electricity.

[0017] The solar collector in the calcium carbonate reactor further heats the calcium carbonate to its decomposition temperature. The calcium carbonate decomposes into carbon dioxide and calcium oxide, converting thermal energy into chemical energy for storage. The carbon dioxide generated by the microalgae unit enters the calcium oxide reactor, where the reaction between calcium oxide and carbon dioxide releases heat. The heat in the heat storage unit comes from the heat released by the reaction between calcium oxide and carbon dioxide.

[0018] Furthermore, when wind and solar power generation reaches its peak and the energy storage phase is completed, supercritical carbon dioxide will be transported via pipeline to the seabed for storage.

[0019] Furthermore, the exhaust port of the final stage expander discharges carbon dioxide into the microalgae reaction chamber through the exhaust pipe. Under set conditions, the microalgae generate microalgae biomass, which is then sent to the microalgae biomass treatment device for processing to produce biodiesel. A portion of the biodiesel is used as fuel for an internal combustion engine to drive a second generator to generate electricity. The high-temperature carbon dioxide and water vapor mixture generated by the combustion of biodiesel transfers heat to the calcium oxide reaction device and is then sent to the dehumidification device. The exhaust gas contains only carbon dioxide, which is then passed back into the microalgae reaction chamber for recycling. The remaining biodiesel is recovered.

[0020] Compared with existing technologies, the present invention has at least the following beneficial effects: Based on existing equipment in thermal power plants, the present invention combines carbon dioxide energy storage, microalgae diesel production technology, and carbon dioxide seabed sequestration technology. It uses carbon dioxide emitted from thermal power plants as the energy storage medium. In the energy storage stage, surplus wind and solar power is used to drive a compressor to compress carbon dioxide to a supercritical state for storage. At the same time, a heat exchanger collects the heat generated during the compression of carbon dioxide to preheat calcium carbonate. The calcium carbonate is further heated to the decomposition temperature by a solar collector, thereby converting thermal energy into chemical energy for storage. The generated calcium oxide also has certain industrial and commercial value. In the energy release stage, the supercritical carbon dioxide expands and does work. After the work is completed, the discharged carbon dioxide enters the microalgae reaction chamber as a raw material for microalgae to produce biomass. The calcium oxide and carbon dioxide react after heating to release a large amount of heat. This heat is used by a heat accumulator to heat the carbon dioxide working medium before the expander, thereby improving its work capacity.

[0021] Furthermore, microalgae generate microalgal biomass under conditions of carbon dioxide, light, and nutrients. After processing, this biomass is converted into biodiesel, which can be used as fuel for internal combustion engines. The internal combustion engine drives a generator to produce electricity, and the heat from the high-temperature exhaust gas can be used to heat calcium oxide and carbon dioxide to the reaction conditions through heat exchange. After dehumidification, only carbon dioxide remains in the exhaust gas, which can be recycled into the microalgae reaction chamber. The reaction of calcium oxide and carbon dioxide generates a large amount of heat, improving the quality of the thermal energy of the internal combustion engine exhaust gas.

[0022] Furthermore, since carbon dioxide has a relatively high critical pressure, exceeding 7.3773 MPa, the compressor unit adopts a three-stage compression process. A first heat exchanger is installed after the first-stage compressor, and a second heat exchanger is installed after the second-stage compressor to provide interstage cooling for the carbon dioxide, thereby reducing compressor energy consumption and storing compression heat.

[0023] Furthermore, since carbon dioxide has a low critical temperature of only 31.3 degrees Celsius, a three-stage expansion process is adopted, with a heat accumulator installed before each stage expander to supplement the heat of supercritical carbon dioxide, thereby improving its work capacity.

[0024] Furthermore, the calcium carbonate reaction device is equipped with a heat exchange structure and inlet / outlet ports. The heat exchange structure is used to absorb heat energy from the accumulator and solar collector to heat the calcium carbonate. Since calcium carbonate is very common in nature, and the production of calcium carbonate requires calcination or other methods, a portion of the decomposed calcium oxide can be exported through the calcium oxide outlet for sale to reduce costs, while calcium carbonate can be replenished through the calcium carbonate inlet.

[0025] The calcium oxide reaction device is equipped with two sets of heat exchange structures and inlet and outlet ports. The first set of heat exchange structures exchanges heat with the exhaust gas of the internal combustion engine to bring the calcium oxide and carbon dioxide to the reaction temperature. The second set of heat exchange structures transfers the heat generated by the reaction of calcium oxide and carbon dioxide to the heat exchanger in front of the expander unit to heat the carbon dioxide. Calcium oxide and carbon dioxide are input through the inlet port and calcium oxide is output through the outlet port.

[0026] Furthermore, when energy storage is complete and there is still a surplus of wind and solar power, supercritical carbon dioxide can be transported via pipeline to the seabed for storage, making the system both economically and environmentally beneficial. Attached Figure Description

[0027] Figure 1 This invention relates to an open supercritical carbon dioxide energy storage system.

[0028] In the diagram: 1. Boiler; 2. Furnace exhaust fan; 3. Absorption tower; 4. First inlet valve; 5. Low-pressure carbon dioxide storage tank; 6. First exhaust valve; 7. Electric motor; 8. First-stage compressor; 9. First heat exchanger; 10. Second-stage compressor; 11. Second heat exchanger; 12. Third-stage compressor; 13. Second inlet valve; 14. Supercritical carbon dioxide storage tank; 15. Second exhaust valve; 16. First accumulator; 17. First-stage expander; 18. Second accumulator; 19. Second-stage expander; 20. Third accumulator; 21. Third-stage expander; 22. First generator; 23. Third exhaust valve; 24. Calcium carbonate reaction device; 25. Calcium oxide outlet; 26. Calcium carbonate inlet; 27. Solar collector; 28. Calcium oxide reaction device; 29. ​​Microalgae reaction chamber; 30. Microalgae biomass treatment device; 31. Internal combustion engine; 32. Second generator; 33. Dehumidifier. Detailed Implementation

[0029] The invention will now be described in detail with reference to specific embodiments and accompanying drawings. These descriptions are intended to explain the invention and not to limit it.

[0030] This invention couples a supercritical carbon dioxide energy storage system, a calcium carbonate thermal energy storage system, and a biomass power generation system. The supercritical carbon dioxide energy storage system uses carbon dioxide emitted by thermal power plants to store surplus electricity generated during peak wind and solar power generation. The calcium carbonate thermal energy storage system can store the heat of compression and solar heat during the compression process and use it for heat replenishment before the supercritical carbon dioxide expands. The biomass power generation system uses carbon dioxide emitted by the supercritical carbon dioxide energy storage system after it finishes working as a raw material for microalgae reaction to generate biodiesel for power generation. During peak wind and solar power generation, the energy storage time can be extended and the supercritical carbon dioxide can be sealed to the seabed, solving the problems of excessive carbon emissions from thermal power plants and the randomness and volatility of wind and solar energy.

[0031] like Figure 1As shown, an open-type supercritical carbon dioxide energy storage system and its operation method are disclosed, comprising a thermal power plant unit, a supercritical carbon dioxide energy storage unit, a calcium carbonate thermal storage unit, and a microalgae unit; specifically including a boiler 1, a furnace exhaust fan 2, an absorption tower 3, a first inlet valve 4, a low-pressure carbon dioxide storage tank 5, a first exhaust valve 6, an electric motor 7, a first-stage compressor 8, a first heat exchanger 9, a second-stage compressor 10, a second heat exchanger 11, a third-stage compressor 12, a second inlet valve 13, and supercritical carbon dioxide... Storage tank 14, second exhaust valve 15, first accumulator 16, first stage expander 17, second accumulator 18, second stage expander 19, third accumulator 20, third stage expander 21, first generator 22, third exhaust valve 23, calcium carbonate reaction device 24, calcium oxide outlet 25, calcium carbonate inlet 26, solar collector 27, calcium oxide reaction device 28, microalgae reaction chamber 29, microalgae biomass treatment device 30, internal combustion engine 31, second generator 32, dehumidification device 33.

[0032] The thermal power plant unit includes a boiler 1, a furnace exhaust fan 2, and an absorption tower 3 connected in sequence; the supercritical carbon dioxide energy storage unit includes a first inlet valve 4, a carbon dioxide storage tank 5, a first exhaust valve 6, an electric motor 7, a first-stage compressor 8, a first heat exchanger 9, a second-stage compressor 10, a second heat exchanger 11, a third-stage compressor 12, a second inlet valve 13, a supercritical carbon dioxide storage tank 14, a second exhaust valve 15, a third exhaust valve 23, a first accumulator 16, a first expander 17, a second accumulator 18, a second expander 19, a third accumulator 20, a third expander 21, and a first generator 22; the calcium carbonate thermal energy storage unit includes a calcium carbonate reaction device 24, a calcium oxide outlet 25, a calcium carbonate inlet 26, a solar collector 27, and a calcium oxide reaction device 28; the microalgae unit includes a microalgae reaction chamber 29, a microalgae biomass treatment device 30, an internal combustion engine 31, a generator 32, and a dehumidification device 33, with all pipes and containers having good sealing performance.

[0033] The carbon dioxide storage tank 5, the first exhaust valve 6, the first stage compressor 8, the hot side of the first heat exchanger 9, the second stage compressor 10, the hot side of the second heat exchanger 11, the third stage compressor 12, the second intake valve 13, the supercritical carbon dioxide storage tank 14, and the second exhaust valve 15 are connected in sequence.

[0034] The outlet of the supercritical carbon dioxide storage tank 14 is sequentially connected to the cold side of the first heat accumulator 16, the first expander 17, the cold side of the second heat accumulator 18, the second expander 19, the cold side of the third heat accumulator 20, and the third expander 21. The first expander 17, the second expander 19, and the third expander 21 are connected to the first generator 22.

[0035] The exhaust port of the third expander 21 is connected to the microalgae reaction chamber 29. The microalgae reaction chamber 29 is connected in sequence to the microalgae biomass treatment device 30, the internal combustion engine 31, and the calcium oxide reaction device 28. The carbon dioxide outlet of the calcium oxide reaction device 28 is also connected in sequence to the dehumidification device and the microalgae reaction chamber 29. The internal combustion engine 31 is connected to the second generator 32.

[0036] Solar collector 27 is used to heat calcium carbonate reactor 24. Calcium carbonate reactor 24 is equipped with a heat exchange structure for exchanging heat with solar collector 27. Calcium carbonate reactor 24 also has a heat exchange device for exchanging heat with the hot gas generated by calcium oxide reactor 28. The hot side of the heat exchange device of calcium carbonate reactor 24 is connected to the cold side of the first heat exchanger 9 and the second heat exchanger 11, respectively. The hot gas inlet of calcium carbonate reactor 24 is connected to the hot gas outlet of calcium oxide reactor 28, and the hot gas inlet of calcium oxide reactor 28 is connected to the hot gas outlet of calcium carbonate reactor 24. The calcium oxide reactor has two sets of heat exchange structures and inlet / outlet ports. The first set of heat exchange structures exchanges heat with the exhaust gas of the internal combustion engine to bring calcium oxide and carbon dioxide to the reaction temperature. The second set of heat exchange structures transfers the heat generated by the reaction of calcium oxide and carbon dioxide to the heat exchanger before the expander unit, thereby heating the carbon dioxide. Calcium oxide and carbon dioxide are input through the inlet port and calcium oxide is output through the outlet port.

[0037] The outlet of the calcium oxide reaction device 28 is connected to the hot side inlet of the third accumulator 20, the second accumulator 18 and the first accumulator 16 respectively, and the hot side outlet of the third accumulator 20, the second accumulator 18 and the first accumulator 16 are all connected to the calcium oxide reaction device 28.

[0038] A first intake valve 4 is installed on the intake pipe connected to the top of the low-pressure carbon dioxide storage tank 5, and the first intake valve 4 is connected to the absorption tower 3; a first exhaust valve 6 is installed on the exhaust pipe connected to the upper side of the low-pressure carbon dioxide storage tank 5, and the first exhaust valve 6 is connected to the compressor unit.

[0039] A second intake valve 13 is installed on the intake pipe connected to the top of the supercritical carbon dioxide storage tank 14, and a compressor unit is connected before the second intake valve 13; a second exhaust valve 15 and a third exhaust valve 23 are installed on the exhaust pipe connected to the bottom of the supercritical carbon dioxide storage tank 14, the second exhaust valve 15 is connected to the expander unit, and the third exhaust valve 23 is connected to the pipeline leading to the seabed.

[0040] Because carbon dioxide has a high critical pressure, exceeding 7.3773 MPa, the compressor unit adopts three-stage compression. A first heat exchanger 9 is installed after the first-stage compressor 9, and a second heat exchanger 11 is installed after the second-stage compressor 10 to provide interstage cooling for the carbon dioxide, reduce compressor energy consumption, and store compression heat. The critical temperature of carbon dioxide is low, only 31.3 degrees Celsius. In order to improve its work capacity, a three-stage expansion is adopted, and a heat accumulator is installed before each stage expander to supplement the heat of supercritical carbon dioxide.

[0041] The heat generated by the compressor unit is exchanged with the calcium carbonate reaction device 24 via a heat exchanger to heat the calcium carbonate. At the same time, the heat energy generated by the solar collector 27 further heats the calcium carbonate to its decomposition temperature, causing the calcium carbonate to decompose into calcium oxide and carbon dioxide, and the thermal energy is converted into chemical energy and stored.

[0042] The exhaust port of the supercritical carbon dioxide storage tank 14 is connected to the seabed through the third exhaust valve 23 and pipeline.

[0043] The power input terminal of the compressor unit motor 1 is connected to the power output terminal of the wind power and solar power generation system and the power grid. The power of the compressor unit motor 1 comes from the surplus power during the off-peak hours and the abundant power during the peak hours of wind power and solar power generation.

[0044] Silica is added to the calcium carbonate reaction apparatus to promote the thermal decomposition of calcium carbonate.

[0045] The calcium carbonate reaction device is equipped with a heat exchange structure and inlet / outlet ports. The heat exchange structure is used to absorb heat energy from the accumulator and solar collector to heat the calcium carbonate. Since calcium carbonate is very common in nature, and the production of calcium carbonate requires calcination or other methods, a portion of the decomposed calcium oxide can be exported through the outlet port for sale to reduce costs, while calcium carbonate can be replenished through the loading port.

[0046] Based on the above system, the open supercritical carbon dioxide energy storage system and its operation method described in this invention are as follows:

[0047] During the pre-setting stage, the first exhaust valve 6 is closed and the first inlet valve 4 is opened, allowing the carbon dioxide generated by the absorption tower to enter the low-pressure carbon dioxide storage tank 5. When the pressure reaches the set value, the first inlet valve 4 is closed.

[0048] During the energy storage phase, the first intake valve 4, the second exhaust valve 15, and the third exhaust valve 23 are closed, while the first exhaust valve 6 and the second intake valve 13 are opened, allowing gas from the low-pressure carbon dioxide storage tank 5 to enter the compressor unit. After three stages of compression, the low-pressure carbon dioxide becomes supercritical and enters the supercritical carbon dioxide storage tank 14, completing the energy storage phase. During carbon dioxide compression, the heat from interstage cooling is transferred to the calcium carbonate reactor 24 via a heat exchanger. Simultaneously, the calcium carbonate reactor 24 is further heated by the solar collector 27, causing calcium carbonate to decompose into carbon dioxide and calcium oxide at high temperatures.

[0049] During the energy release phase, the first intake valve 4, the second intake valve 13, the first exhaust valve 6, and the third exhaust valve 23 are closed, while the second exhaust valve 15 is opened, allowing supercritical carbon dioxide to enter the expander unit via the heat exchanger for expansion and power generation, thus completing the energy release phase. During carbon dioxide expansion, each stage of the expander receives supplemental heat via a heat accumulator to enhance the carbon dioxide's work-generating capacity. The heat in the heat accumulator comes from the calcium oxide reactor 28.

[0050] When energy storage is complete and there is still a surplus of wind and solar power, supercritical carbon dioxide will be transported to the seabed via pipeline for storage, so that the system can be both economically and environmentally beneficial.

[0051] The expander unit's exhaust port discharges high-concentration carbon dioxide into the microalgae reaction chamber 29 through the exhaust pipe. Under conditions of carbon dioxide and light, the microalgae generate microalgae biomass, which is then sent to the microalgae biomass treatment device 30 for processing to produce biodiesel. Part of this biodiesel can be sold as an industrial product to increase revenue, while the remainder can be used as fuel for the internal combustion engine 31 to drive the second generator 32 to generate electricity. The high-temperature carbon dioxide and water vapor mixture generated by the combustion of biodiesel transfers heat to the calcium oxide reaction device 28, causing the calcium oxide and carbon dioxide to react and release heat, thereby improving the exhaust heat energy quality. The exhaust gas is then sent to the dehumidification device 33, at which point only carbon dioxide remains in the exhaust gas, which is then passed into the microalgae reaction chamber 29 for recycling.

[0052] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. An open supercritical carbon dioxide energy storage system, characterized by, The system comprises a thermal power plant unit, a supercritical carbon dioxide energy storage unit, a calcium carbonate heat storage unit and a microalgae unit. The supercritical carbon dioxide energy storage unit is provided with a multi-stage compression energy storage unit and a multi-stage expansion energy release unit, heat exchangers are arranged between the stages of the multi-stage compression energy storage unit, and a heat accumulator is arranged at the inlet of each stage of the multi-stage expansion energy release unit; the carbon dioxide outlet of the thermal power plant unit is connected to the multi-stage compression energy storage unit and the multi-stage expansion energy release unit in sequence; the calcium carbonate heat storage unit comprises a calcium carbonate reaction device (24), a solar heat collector (27) and a calcium oxide reaction device (28); the cold side of the heat exchanger is connected to the calcium carbonate reaction device (24), and the solar heat collector (27) is used for heating the calcium carbonate reaction device (24); the hot gas inlet and outlet of the calcium oxide reaction device (28) are communicated with the hot side of the heat accumulator; the gas outlet of the microalgae unit is connected to the calcium oxide reaction device (28); the gas outlet of the supercritical carbon dioxide energy storage unit is also communicated with the seabed; the calcium carbonate reaction device (24) is provided with a heat exchange structure, a calcium oxide outlet (25) and a calcium carbonate inlet (26); the heat exchange structure is used for absorbing the heat energy of the heat exchanger and the solar heat collector to heat the calcium carbonate; the microalgae unit comprises a microalgae reaction chamber (29), a microalgae biomass treatment device (30), an internal combustion engine (31), a second generator (32) and a dehumidification device (33), which are connected in sequence, and the gas outlet of the internal combustion engine (31) is connected to the calcium oxide reaction device (28) and the dehumidification device (33) in sequence.

2. The open supercritical carbon dioxide energy storage system of claim 1, wherein, The thermal power plant unit comprises a boiler (1), a post-combustion induced draft fan (2) and an absorption tower (3) connected in sequence, and the outlet of the absorption tower (3) is connected to the gas inlet of the multi-stage compression energy storage unit in the supercritical carbon dioxide energy storage unit through a first gas inlet valve (4); the heat exchanger comprises a first heat exchanger (9) and a second heat exchanger (11), the multi-stage compression energy storage unit comprises a first-stage compressor (8), a second-stage compressor (10) and a third-stage compressor (12), and in the multi-stage compression energy storage unit, the first gas inlet valve (4), a carbon dioxide storage tank (5), a first gas outlet valve (6), the first-stage compressor (8), the first heat exchanger (9), the second-stage compressor (10), the second heat exchanger (11), the third-stage compressor (12), a second gas inlet valve (13) and a supercritical carbon dioxide storage tank (14) are connected in sequence along the gas flow direction; the power end of the first-stage compressor (8), the second-stage compressor (10) and the third-stage compressor (12) is connected to an electric motor (7).

3. The open supercritical carbon dioxide energy storage system of claim 1, wherein, The heat accumulator comprises a first heat accumulator (16), a second heat accumulator (18) and a third heat accumulator (20), and the multi-stage expansion machine energy release unit comprises a first expansion machine (17), a second expansion machine (19) and a third expansion machine (21); in the multi-stage expansion machine energy release unit: the cold side of the first heat accumulator (16), the first expansion machine (17), the cold side of the second heat accumulator (18), the second expansion machine (19), the cold side of the third heat accumulator (20) and the third expansion machine (21) are sequentially connected along the flow direction of carbon dioxide, and the first expansion machine (17), the second expansion machine (19) and the third expansion machine (21) are connected with a first generator (22).

4. The open supercritical carbon dioxide energy storage system of claim 3, wherein, The hot gas inlets and outlets of the calcium oxide reaction device (28) are respectively communicated with the hot side of the first heat accumulator (16), the hot side of the second heat accumulator (18) and the hot side of the third heat accumulator (20).

5. An open supercritical carbon dioxide energy storage system according to claim 1, wherein, The supercritical carbon dioxide storage tank (14) is arranged in the supercritical carbon dioxide energy storage unit, a second air inlet valve (13) is arranged on the air inlet pipeline communicated with the top of the supercritical carbon dioxide storage tank (14), and the outlet of the multi-stage compressor unit is connected before the second air inlet valve (13); a second air outlet valve (15) and a third air outlet valve (23) are arranged on the air outlet pipeline communicated with the bottom of the supercritical carbon dioxide storage tank (14), the second air outlet valve (15) is connected with the multi-stage expansion machine unit, and the third air outlet valve (23) is connected with the pipeline leading to the seabed.

6. An open supercritical carbon dioxide energy storage system according to claim 1, wherein, The calcium oxide reaction device is provided with two sets of heat exchange structures and inlet and outlet ports, heat exchange is performed between the calcium oxide and the exhaust gas of the internal combustion engine through the first set of heat exchange structures so that the calcium oxide and the carbon dioxide reach the reaction temperature, the heat generated by the reaction between the calcium oxide and the carbon dioxide is transferred to the heat accumulator before the expansion machine unit through the second set of heat exchange structures so as to heat the carbon dioxide, and the calcium oxide and the carbon dioxide are input through the inlet port.

7. The method of operating an open supercritical carbon dioxide energy storage system of any of claims 1-6, wherein, The method comprises: In the pre-setting stage, the carbon dioxide generated by the absorption tower is compressed to supercritical carbon dioxide by the multi-stage compressor unit; In the energy storage stage, the heat is transferred to the calcium carbonate reaction device (24) through the heat exchanger during the compression of the carbon dioxide; In the energy release stage, the supercritical carbon dioxide is heated by the heat accumulator and then enters the multi-stage expansion machine unit to expand and generate electricity; The calcium carbonate reaction device (24) is further heated by the solar heat collector so that the calcium carbonate reaches its decomposition temperature, and the calcium carbonate is decomposed to generate carbon dioxide and calcium oxide, and the heat energy is converted into chemical energy for storage; the carbon dioxide generated by the microalgae unit enters the calcium oxide reaction device (28), the calcium oxide and the carbon dioxide react to release heat in the calcium oxide reaction device (28), and the heat of the heat accumulator comes from the heat released by the reaction between the calcium oxide and the carbon dioxide.

8. The method of operating of claim 7, wherein, When the wind power and solar power generation peak and the energy storage stage is completed, the supercritical carbon dioxide is transported to the seabed through the pipeline for storage.

9. The method of operating of claim 7, wherein, The last stage expander exhaust port discharges carbon dioxide to the microalgae reactor (29) through the exhaust pipeline, and the microalgae generates microalgae biomass under the set conditions. The microalgae biomass is sent to the microalgae biomass treatment device (30) to generate biodiesel after treatment. A part of the biodiesel is used as fuel for the internal combustion engine (31) to drive the second generator (32) to generate electricity. The high-temperature carbon dioxide and water vapor mixture generated by the combustion of the biodiesel transmits heat to the calcium oxide reaction device (28), and is then sent to the dehumidification device (33). Only carbon dioxide is in the tail gas, which is discharged into the microalgae reactor (29) for recycling. The remaining biodiesel is recycled.

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