Solar power generation system
The solar power generation system addresses inefficiencies in supercritical carbon dioxide Brayton cycle systems by employing a dual-loop design with endothermic and exothermic reactions, stabilizing pressures, and enabling direct heat exchange, thus reducing costs and improving efficiency.
Patent Information
- Application Number
- CN202010813925.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2020-08-13
- Publication Date
- 2024-12-10
- Estimated Expiration
- 2040-08-13
AI Technical Summary
Current solar thermal power generation systems using the supercritical carbon dioxide Brayton cycle face challenges with high costs, inefficiencies due to indirect heat exchange, low energy storage density, and significant heat losses, particularly in the absorber, lacking thermochemical energy storage solutions.
A solar power generation system utilizing a medium flow path with a first and second loop, incorporating heat storage/release units and a pressure regulating unit, where endothermic and exothermic reactions occur at different pressures and temperatures, stabilizing gas pressures and enabling direct heat exchange with carbon dioxide as the medium, reducing material requirements and heat losses.
The system achieves efficient medium-temperature heat storage and high-temperature heat release, lowering manufacturing costs, improving efficiency, and ensuring stable power output by utilizing carbon dioxide reactions, enhancing the Brayton cycle's performance.
Smart Images
Figure CN111828268B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of energy technology, in particular to a solar power generation system. Background Art
[0002] With the massive consumption of traditional fossil energy and the increasingly prominent environmental problems, the development of renewable energy has received widespread attention. As the cleanest energy with the most abundant reserves, solar energy is the focus of future renewable energy development.
[0003] Solar power generation technology is mainly divided into two categories: photovoltaic power generation and solar thermal power generation. Compared with photovoltaic power generation, solar thermal power generation uses cheap energy storage technology and has the advantages of stable and continuous power output. It can be used as a basic charge power supply and as a peak-shaving power supply, and has great development potential.
[0004] Solar thermal power generation technologies mainly include tower, trough, dish and linear Fresnel types. Among them, tower thermal power stations have relatively high concentration, high system operating temperature and high heat collection efficiency. They are currently a hot research topic. However, compared with traditional power stations, the cost of solar tower thermal power generation is still relatively high. In order to further improve the efficiency of solar thermal power generation, reduce costs and accelerate the commercialization process, it is crucial to find a high-efficiency and compact power cycle.
[0005] The supercritical carbon dioxide Brayton cycle uses supercritical carbon dioxide (critical pressure 7.38MPa, critical temperature 30.98℃) as the working medium and uses the Brayton cycle to achieve energy conversion. Compared with the water vapor Rankine cycle, the supercritical carbon dioxide Brayton cycle performs work in a single phase, has a simple system design, and reduces the complexity of operation; supercritical carbon dioxide maintains a high density throughout the power cycle, requires less compression work, and has smaller turbine and heat exchanger sizes, a small footprint, and higher thermal efficiency; in addition, the cooling method of the supercritical carbon dioxide Brayton cycle can be air cooling, which is not limited by water resources and can be used in arid areas with abundant sunlight and tight water resources. Therefore, the high-efficiency and compact supercritical carbon dioxide Brayton cycle is an ideal choice for solar thermal power generation.
[0006] The coupling mode of supercritical carbon dioxide Brayton cycle and solar thermal power station is divided into two modes: direct coupling and indirect coupling. In the direct coupling mode, supercritical carbon dioxide acts as both a heat transfer medium and a working medium. It first passes through a solar absorber to absorb high-temperature solar energy, and then enters the power cycle system to do work. The heat transfer medium and the working medium do not need to exchange heat, the heat exchanger is omitted, the device is simplified, and the heat exchange loss is reduced. The working medium has a higher temperature and a higher thermal efficiency, but the requirements for the absorber are more stringent, and the control process under high temperature and high pressure is more difficult to achieve; in the indirect coupling mode, supercritical carbon dioxide is only used as a working medium, and other substances are used as heat transfer media. First, the heat transfer medium passes through a solar absorber, and the heated high-temperature heat transfer medium transfers heat to the working medium supercritical carbon dioxide through a heat exchanger. The formed high-temperature supercritical carbon dioxide enters the power cycle system to do work. Compared with the direct coupling mode, the indirect coupling mode is easier to realize the combination with the heat storage system.
[0007] At present, the research on energy storage system of solar supercritical carbon dioxide Brayton cycle thermal power station is mainly based on indirect coupling mode, generally using molten salt or solid particles as heat transfer medium and heat storage medium. Molten salt or solid particles pass through solar absorber to absorb high temperature solar energy. After absorbing heat, the heat transfer medium is divided into two parts, one part enters the storage tank as heat storage medium to store heat, and the other part enters the heat exchanger to transfer heat to supercritical carbon dioxide as working medium. The heated supercritical carbon dioxide enters the power cycle system to do work externally. The way of storing energy by increasing the temperature of molten salt or solid particles belongs to sensible heat storage, which has low energy storage density. Most of the heat transfer medium and working medium adopt indirect heat exchange, which has low heat exchange efficiency. In addition, the heat exchange process inevitably has temperature drop and energy quality reduction. The transportation of molten salt and solid particles requires work. At the same time, the high temperature absorber has large heat loss, which affects the overall efficiency. In addition, there is a lack of thermochemical energy storage technology combined with solar supercritical carbon dioxide thermal power station, and the system cost is high. Therefore, it is very important to develop a thermochemical energy storage technology with high heat storage density, high use temperature, low cost, high efficiency and environmental friendliness for solar supercritical carbon dioxide Brayton cycle thermal power station. Summary of the invention
[0008] In response to the above problems, the present invention provides a solar power generation system, which realizes medium-temperature heat storage and high-temperature heat release by adjusting the partial pressure of carbon dioxide during the heat storage and release process. The operating pressure and temperature of the heat transfer medium are relatively low, which greatly reduces the requirements on the strength of the absorber and pipeline materials, reduces the manufacturing costs of the absorber and pipelines, improves the safety of system operation, and ensures that the power generation system works under high temperature conditions while the absorber absorbs heat under medium temperature conditions, thus avoiding large heat losses of the high-temperature absorber, which is conducive to improving the overall efficiency and can effectively solve the problems in the background technology.
[0009] The solar power generation system provided by the present invention has a medium flow path for accommodating a medium circulating in the solar power generation system, and the medium flow path includes a first loop and a second loop, wherein:
[0010] The first circuit connects the solar thermal absorber and the first heat storage / release unit.
[0011] The first heat storage / release unit is disposed downstream of the flow path of the solar thermal absorber and stores energy by utilizing an endothermic reaction occurring at a first temperature and a first pressure;
[0012] The endothermic reaction decomposes the first solid substance into a second solid substance and a medium, and the generated medium flows into the first loop;
[0013] The second loop connects the Brayton cycle system and the second heat storage / release unit.
[0014] A second heat storage / release unit releases energy by utilizing an exothermic reaction occurring at a second temperature higher than the first temperature and a second pressure higher than the first pressure;
[0015] The exothermic reaction is the reverse reaction of the endothermic reaction, and the exothermic reaction generates the first solid substance by combining the second solid substance with the medium in the second loop;
[0016] The compressor of the Brayton cycle system compresses the medium in the second circuit and supplies it to the second heat storage / release unit;
[0017] The turbine of the Brayton cycle system receives the medium flowing out from the second heat storage / release unit and uses the flowing out medium as a working medium;
[0018] The medium flow path also includes a pressure regulating unit, which connects the first circuit and the second circuit. The pressure regulating unit can stabilize the air pressure in the first circuit below a specified threshold by transporting the medium in the first circuit to the second circuit.
[0019] By adopting the above technical solution, when the first storage / release unit is used as a heat storage module, an endothermic reaction occurs therein, and when the second storage / release unit is used as a heat release module, an exothermic reaction occurs therein; because the solar thermal absorber is connected to the first storage / release unit in the first circuit, and the first storage / release unit is arranged downstream of the flow path of the solar thermal absorber, after the solar thermal absorber heats the medium flowing through itself, the medium carrying solar energy flows into the first storage / release unit, because the endothermic reaction occurs in the first storage / release unit, and the medium is generated, as the amount of the medium in the first storage / release unit increases, the gas pressure of the first circuit increases. The pressure regulating unit connects the first circuit and the second circuit, and the reactions occurring in the first storage / release unit and the second storage / release unit are reverse reactions to each other. When the medium generated by the endothermic reaction exceeds the pressure setting value of the first circuit, the gas reactant introduced into the second circuit as the exothermic reaction through the pressure regulating unit is consumed, because the total amount of the medium in the first circuit and the second circuit is conserved, the pressure of each of the first circuit and the second circuit can be stabilized. Because the Brayton cycle system and the second heat storage / release unit are connected in the second loop, the medium compressed to high pressure by the compressor of the Brayton cycle system and then heated can flow into the second heat storage / release unit through the medium flow path, satisfying the high-temperature heat release reaction condition in the second heat storage / release unit. Because another part of the medium is heated by the heat released by the reaction in the second heat storage / release unit, the medium flowing into the turbine from the outlet of the second heat storage / release unit reaches a temperature capable of driving the turbine to do work. Because the medium flowing into the inlet of the second heat storage / release unit is compressed to a pressure capable of driving the turbine to do work by the compressor of the Brayton cycle system, the temperature and pressure of the working medium flowing into the turbine from the outlet of the second heat storage / release unit both satisfy the conditions for driving the turbine to do work. The turbine does work and further drives the generator connected to the downstream of the turbine to generate electricity. The power generation system realizes medium-temperature heat storage and high-temperature heat release, reduces the requirements on the strength of the heat absorber and pipeline materials, reduces the manufacturing cost, and at the same time satisfies the conditions that the working medium of the turbine needs to be at high temperature and high pressure, avoids the large heat loss of the high-temperature heat absorber, and improves the overall efficiency.
[0020] A technical solution of the present invention is further configured to include a circuit switching device, which can switch the first heat storage / release unit to the second circuit so that it occupies the original position of the second heat storage / release unit, and switch the second heat storage / release unit to the first circuit so that it occupies the original position of the first heat storage / release unit.
[0021] By adopting the above technical solution, because the loop switching device can exchange the first heat storage / release unit and the second heat storage / release unit in the connecting device of the power generation system, and the reactions occurring in the first heat storage / release unit and the second heat storage / release unit are reverse reactions to each other, the reactant of the first heat storage / release unit is the product in the second heat storage / release unit, and switching the respective connecting devices of the first heat storage / release unit and the second heat storage / release unit is equivalent to switching the storage / release state of the first heat storage / release unit and the second heat storage / release unit, and the cyclic switching ensures the stability and continuity of the output power of the power cycle system.
[0022] A technical solution of the present invention is further configured that the pressure regulating unit includes a back pressure valve connected to the first circuit; an air storage tank is arranged in the medium flow path between the back pressure valve and the second circuit; and a pre-compressor is arranged in the medium flow path between the back pressure valve and the air storage tank.
[0023] By adopting the above technical solution, because the back pressure valve is connected to the first circuit, the back pressure valve introduces the medium generated in the first circuit that exceeds the air pressure threshold of the first circuit into the second circuit to maintain the stability of the air pressure of the first circuit; because the pre-compressor and the air storage tank are sequentially arranged in the medium flow path of the back pressure valve and the second circuit, the medium first flows into the pre-compressor through the back pressure valve to be compressed, and then enters the air storage tank to be stored; because the pressure regulating unit connects the first circuit and the second circuit, the medium flowing out of the air storage tank outlet can flow into the compressor of the Brayton cycle system, and the air storage tank, the pre-compressor and the compressor cooperate to improve the efficiency of the entire power generation system; the air storage tank can replenish the medium into the second circuit, thereby maintaining the air pressure in the second circuit at a higher value.
[0024] A technical solution of the present invention is further configured such that the outlet of the gas storage tank is connected to the inlet of the compressor of the Brayton cycle system, and the medium flowing out of the gas storage tank is combined with the medium from the cooler of the Brayton cycle system into the compressor.
[0025] By adopting the above technical solution, because the outlet of the air storage tank is connected to the inlet of the compressor of the Brayton cycle system, the outlet of the cooler is also connected to the inlet of the compressor of the Brayton cycle system, and the inlet of the air storage tank is connected to the outlet of the pre-compressor, the media of different medium flow paths are pre-compressed and cooled at the same time and converged to the compressor, and then compressed to high pressure, so the high efficiency of the system is guaranteed.
[0026] A technical solution of the present invention is further configured to include a heat exchanger, wherein the inlet on the hot fluid side of the heat exchanger is connected to the back pressure valve, and the inlet on the cold fluid side of the heat exchanger is connected to the outlet of the compressor.
[0027] By adopting the above technical solution, because the inlet on the hot fluid side of the heat exchanger is connected to the back pressure valve, the medium after absorbing heat from the first circuit exchanges heat with the medium on the cold fluid side of the heat exchanger; because the inlet on the cold fluid side of the heat exchanger is connected to the outlet of the compressor, the medium compressed by the compressor exchanges heat with the medium flowing out of the first circuit, thereby improving the utilization efficiency of the medium's thermal energy.
[0028] A technical solution of the present invention is further configured such that the second circuit also includes a regenerator, the inlet of the hot fluid side of the regenerator is connected to the outlet of the turbine, and the inlet of the cold fluid side of the regenerator is connected to the outlet of the cold fluid side of the heat exchanger.
[0029] By adopting the above technical solution, because the inlet of the hot fluid side of the regenerator is connected to the outlet of the turbine, after the working medium drives the turbine to do work, the residual heat of the working medium exchanges heat with the medium on the cold fluid side of the regenerator. Because the inlet of the cold fluid side of the regenerator is connected to the outlet of the cold fluid side of the heat exchanger, the medium flowing out of the cold fluid side of the heat exchanger is preheated by the medium flowing out of the first circuit, and then reheated by the working medium after driving the turbine to do work. Because the Brayton cycle system of the second circuit is connected to the second storage / release unit, the medium flows into the second storage / release unit after being heated again by the regenerator. At this time, the medium reaches the temperature condition of the reaction in the second storage / release unit, and the energy utilization and efficiency of the system are improved.
[0030] A technical solution of the present invention is further configured such that the heat transfer medium is carbon dioxide, the working medium is supercritical carbon dioxide, and the first solid substance is a metal carbonate or a mixture containing a metal carbonate.
[0031] By adopting the above technical scheme, since the heat transfer medium, the working medium and the gaseous product / reactant of the metal carbonate or the mixture containing the metal carbonate are all carbon dioxide, direct contact heat exchange can be adopted in the heat storage / release process, which has higher heat exchange efficiency than indirect heat exchange; in addition, the reciprocal reactions of the decomposition and combination of the metal carbonate or the mixture containing the metal carbonate only generate solid substances or carbon dioxide, and no other products are produced, which is conducive to the construction of the circulation system, and the supercritical carbon dioxide has good compatibility with the Brayton cycle, and is an ideal choice for solar thermal power generation.
[0032] A technical solution of the present invention is further configured such that the focusing system of the solar thermal absorber is one or more of a tower focusing system, a dish focusing system, a trough focusing system or a linear Fresnel focusing system.
[0033] By adopting the above technical solution, different focusing systems of the solar thermal absorber are selected and used in combination, so as to increase the applicability of the power generation system.
[0034] The solar power generation method provided by the present invention comprises the following steps:
[0035] A medium flow path for accommodating a medium circulating in a solar power generation system is provided, wherein the medium flow path includes a first loop and a second loop, wherein the first loop is connected to a solar thermal absorber and a first heat storage / release unit, and the second loop is connected to a Brayton cycle system and a second heat storage / release unit;
[0036] Providing a first heat storage / discharge unit disposed downstream of the flow path of the solar heat absorber;
[0037] Energy is stored by utilizing an endothermic reaction occurring at a first temperature and a first pressure, the medium in the first loop serves as a heat transfer medium, and the endothermic reaction decomposes the first solid substance into a second solid substance and the medium;
[0038] The generated medium is introduced into the first circuit;
[0039] Energy is released by utilizing an exothermic reaction occurring at a second temperature higher than the first temperature and a second pressure higher than the first pressure, wherein the exothermic reaction is a reverse reaction of the endothermic reaction, and the exothermic reaction generates the first solid substance by combining the second solid substance with the medium in the second circuit;
[0040] Using a compressor of the Brayton cycle system, the medium in the second circuit is compressed and supplied to the second heat storage / release unit;
[0041] Using a turbine of the Brayton cycle system to receive the medium flowing out of the second heat storage / release unit, and using the flowing out medium as a working medium;
[0042] By using a pressure regulating unit connecting the first circuit and the second circuit, the gas pressure in the first circuit is stabilized below a specified threshold value by transporting the medium in the first circuit to the second circuit.
[0043] A technical solution of the present invention is further configured to include the following steps:
[0044] The first heat storage / release unit is switched to the second circuit so that it occupies the original position of the second heat storage / release unit, and the second heat storage / release unit is switched to the first circuit so that it occupies the original position of the first heat storage / release unit. BRIEF DESCRIPTION OF THE DRAWINGS
[0045] Figure 1 A schematic diagram of the structure of a solar power generation system provided in Embodiment 1 of the present invention;
[0046] Figure 2 A schematic diagram of the structure of a solar power generation system including a recompression Brayton cycle system provided in the second embodiment of the present invention;
[0047] Figure 3 A schematic diagram of the structure of a solar power generation system including a recompression partial cooling Brayton cycle system provided in the second embodiment of the present invention;
[0048] Figure 4 This is a schematic structural diagram of a solar power generation system including a recompression and intercooling Brayton cycle system provided in the second embodiment of the present invention.
[0049] Explanation of the reference numerals: 1-solar thermal absorber; 2-first heat storage / release unit; 3-second heat storage / release unit; 4-heat exchanger; 5-pre-compressor; 6-gas storage tank; 7-turbine; 8-generator; 9-compressor; 91-main compressor; 92-recompressor; 10-cooler; 11-regenerator; 111-high-temperature regenerator; 112-low-temperature regenerator; 12-back pressure valve; 13-first compressor; 14-intermediate cooler; 15-medium flow path; 151-first circuit; 152-second circuit; 16-pressure regulating unit; 17-Brayton cycle system; 18-circuit switching device. DETAILED DESCRIPTION
[0050] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0051] Embodiment 1
[0052] This embodiment provides a solar power generation system having a medium flow path 15 for accommodating a medium to circulate in the solar power generation system. The medium flow path 15 includes a first loop 151 and a second loop 152 .
[0053] In the present invention, the first loop 151 is used as a heat transfer medium flow path of the heat transfer cycle of the solar power generation system, and the second loop 152 is used as a working medium flow path of the power cycle of the solar power generation system.
[0054] Accordingly, the medium in the first circuit 151 serves as a heat transfer medium, and the medium in the second circuit 152 serves as a work medium.
[0055] The first loop 151 connects the solar thermal absorber 1 and the first heat storage / release unit 2.
[0056] The first heat storage / release unit 2 is disposed downstream of the flow path of the solar thermal absorber 1 and stores energy by utilizing an endothermic reaction occurring at a first temperature and a first pressure;
[0057] The endothermic reaction decomposes the first solid substance into a second solid substance and a medium, and the generated medium flows into the first loop 151;
[0058] The second loop 152 is connected to the Brayton cycle system 17 and the second heat storage / release unit 3.
[0059] The second heat storage / release unit 3 releases energy by utilizing an exothermic reaction occurring at a second temperature higher than the first temperature and a second pressure higher than the first pressure;
[0060] The exothermic reaction is the reverse reaction of the endothermic reaction, and the exothermic reaction generates the first solid substance by combining the second solid substance with the medium in the second loop;
[0061] The compressor 9 of the Brayton cycle system 17 compresses the medium in the second loop 152 and supplies it to the second heat storage / release unit 3;
[0062] The turbine 7 of the Brayton cycle system 17 receives the medium flowing out from the second heat storage / release unit 3 and uses the flowing out medium as a working medium;
[0063] The medium flow path 15 further includes a pressure regulating unit 16 , which connects the first circuit 151 and the second circuit 152 . The pressure regulating unit 16 can stabilize the air pressure in the first circuit 151 below a specified threshold by transporting the medium in the first circuit 151 to the second circuit 152 .
[0064] When the first storage / release unit 2 is used as a heat storage module, an endothermic reaction occurs therein, and when the second storage / release unit 3 is used as a heat release module, an exothermic reaction occurs therein; because the solar thermal absorber 1 is connected to the first storage / release unit 2 in the first loop 151, and the first storage / release unit 2 is arranged downstream of the flow path of the solar thermal absorber 1, after the solar thermal absorber 1 heats the medium flowing through itself, the medium carrying solar energy flows into the first storage / release unit 2, and the first solid substance undergoes an endothermic reaction in the first storage / release unit 2 to generate a medium, which is heated by the medium in the first storage / release unit 2. As the amount increases, the gas pressure of the first loop 151 increases; because the pressure regulating unit 16 connects the first loop 151 and the second loop 152, and the reactions occurring in the first storage / release unit 2 and the second storage / release unit 3 are reverse reactions to each other, when the medium produced by the endothermic reaction exceeds the pressure setting value of the first loop 151, it will be introduced into the second loop 152 through the pressure regulating unit 16 and consumed as a gas reactant of the exothermic reaction. Because the total amount of the medium in the first loop 151 and the second loop 152 is conserved, the pressures of the first loop 151 and the second loop 152 can be stabilized.
[0065] Because the Brayton cycle system 17 and the second heat storage / release unit 3 are connected in the second loop 152, the medium compressed to high pressure by the compressor 9 of the Brayton cycle system 17 and then heated can flow into the second heat storage / release unit 3 through the medium flow path 15, thereby meeting the high-temperature exothermic reaction conditions in the second heat storage / release unit 3.
[0066] Because another part of the medium is heated by the heat released by the reaction in the second storage / release unit 3, the medium flowing into the turbine 7 from the outlet of the second storage / release unit 3 reaches a temperature capable of driving the turbine to do work. Because the medium flowing into the inlet of the second storage / release unit 3 is compressed by the compressor 9 of the Brayton cycle system 17 to a pressure capable of driving the turbine 7 to do work, the temperature and pressure of the medium flowing into the turbine 7 from the outlet of the second storage / release unit 3 both meet the conditions for driving the turbine 7 to do work. The turbine 7 works and further drives the generator 8 connected to the downstream of the turbine 7 to generate electricity. The power generation system realizes medium-temperature heat storage and high-temperature heat release, reduces the requirements on the strength of the heat absorber and pipeline materials, reduces the manufacturing cost, and at the same time meets the conditions that the working medium of the turbine 7 needs to be high temperature and high pressure, avoids the large heat loss of the high-temperature heat absorber, and improves the overall efficiency.
[0067] Furthermore, the solar power generation system also includes a circuit switching device 18, which can switch the first heat storage / release unit 2 to the second circuit 152 so that it occupies the original position of the second heat storage / release unit 3, and switch the second heat storage / release unit 3 to the first circuit 151 so that it occupies the original position of the first heat storage / release unit 2.
[0068] Because the loop switching device 18 can exchange the connection device of the first heat storage / release unit 2 and the second heat storage / release unit 3 in the power generation system, and the reactions occurring in the first heat storage / release unit 2 and the second heat storage / release unit 3 are reverse reactions to each other, the reactant of the first heat storage / release unit 2 is the product in the second heat storage / release unit 3, and switching the respective connection devices of the first heat storage / release unit 2 and the second heat storage / release unit 3 is equivalent to switching the storage / release state of the first heat storage / release unit 2 and the second heat storage / release unit 3, and cyclic switching ensures the stability and continuity of the output power of the power cycle system.
[0069] Furthermore, the pressure regulating unit 16 includes a back pressure valve 12 connected to the first circuit 151; an air storage tank 6 arranged in the medium flow path 15 between the back pressure valve 12 and the second circuit 152; and a pre-compressor 5 arranged in the medium flow path 15 between the back pressure valve 12 and the air storage tank 6.
[0070] Because the back pressure valve 12 is connected to the first circuit 151, the back pressure valve 12 introduces the medium generated in the first circuit 151 that exceeds the air pressure threshold of the first circuit 151 into the second circuit 152 to maintain the stability of the air pressure of the first circuit 151; because the pre-compressor 5 and the air storage tank 6 are arranged in the medium flow path 15 of the back pressure valve 12 and the second circuit 152 respectively, the medium first flows into the pre-compressor 5 through the back pressure valve 12 to be compressed, and then enters the air storage tank 6 to be stored; because the pressure regulating unit 16 connects the first circuit 151 and the second circuit 152, the medium flowing out of the outlet of the air storage tank 6 can flow into the compressor 9 of the Brayton cycle system 17, and the cooperation of the air storage tank 6, the pre-compressor 95 and the compressor 9 improves the efficiency of the entire power generation system.
[0071] The gas storage tank 6 can replenish the medium in the second loop 152, and the gas reactant is consumed as the exothermic reaction, thereby maintaining the gas pressure in the second loop 152 at a higher value.
[0072] Furthermore, the outlet of the gas storage tank 6 is connected to the inlet of the compressor 9 of the Brayton cycle system 17 , and the medium flowing out of the gas storage tank 6 is merged into the compressor 9 together with the medium from the cooler 10 of the Brayton cycle system 17 .
[0073] Because the outlet of the air storage tank 6 is connected to the inlet of the compressor 9 of the Brayton cycle system 17, the outlet of the cooler 10 is also connected to the inlet of the compressor 9 of the Brayton cycle system 17, and the inlet of the air storage tank 6 is connected to the outlet of the pre-compressor 95, the media in different medium flow paths 15 are pre-compressed and cooled at the same time and converged to the compressor 9 to be compressed to high pressure, thereby ensuring the high efficiency of the system.
[0074] The pressure regulating unit 16 further includes a heat exchanger 4 , the hot fluid side of the heat exchanger 4 is connected to the back pressure valve 12 , and the cold fluid side of the heat exchanger 4 is connected to the outlet of the compressor 9 .
[0075] Furthermore, the second circuit 152 also includes a regenerator 11 , the hot fluid side of the regenerator 11 is connected to the outlet of the turbine 7 , and the cold fluid side of the regenerator 11 is connected to the cold fluid side outlet of the heat exchanger 4 .
[0076] The heat exchanger 4 and the heat regenerator 11 are of printing type or other types.
[0077] In this embodiment, the heat exchanger 4 and the regenerator 11 are both printed versions.
[0078] Because the inlet on the hot fluid side of the heat exchanger 4 is connected to the back pressure valve 12, the medium that has absorbed heat from the first loop 151 exchanges heat with the medium on the cold fluid side of the heat exchanger 4. Because the inlet on the cold fluid side of the heat exchanger 4 is connected to the outlet of the compressor 9, the medium compressed by the compressor 9 exchanges heat with the medium flowing out of the first loop 151, thereby improving the utilization efficiency of the medium's thermal energy.
[0079] Because the inlet on the hot fluid side of the regenerator 11 is connected to the outlet of the turbine 7, after the working medium drives the turbine 7 to do work, the remaining heat of the working medium exchanges heat with the medium on the cold fluid side of the regenerator 11. Because the inlet of the cold side fluid of the regenerator 11 is connected to the outlet of the cold side fluid of the heat exchanger 4, the medium flowing out of the cold side fluid outlet of the heat exchanger 4 is preheated by the medium flowing out of the first loop 151, and then is reheated by the working medium after driving the turbine 7 to do work. Because the Brayton cycle system 17 of the second loop 152 is connected to the second storage / release unit 3, the medium is heated again by the regenerator 11 and flows into the second storage / release unit 3. At this time, the medium reaches the temperature condition for the reaction in the second storage / release unit 3, and the energy utilization and efficiency of the system are improved.
[0080] Preferably, the heat transfer medium is carbon dioxide, the working medium is supercritical carbon dioxide, and the first solid substance is a metal carbonate or a mixture containing a metal carbonate.
[0081] Because the heat transfer medium, the working medium and the gaseous product / reactant of the metal carbonate or the mixture containing the metal carbonate are all carbon dioxide, direct contact heat exchange can be used in the heat storage / release process, which has higher heat exchange efficiency than indirect heat exchange.
[0082] In addition, the reciprocal reactions of decomposition and combination of metal carbonates or mixtures containing metal carbonates only produce solids or carbon dioxide without producing other products, which is conducive to the construction of a circulation system. Moreover, supercritical carbon dioxide is well compatible with the Brayton cycle and is an ideal choice for solar thermal power generation.
[0083] Preferably, the focusing system of the solar thermal absorber 1 is one or more of a tower focusing system, a dish focusing system, a trough focusing system or a linear Fresnel focusing system.
[0084] The selection and coordinated use of different concentrating systems of the solar thermal absorber 1 increase the applicability of the power generation system.
[0085] Preferably, the first heat storage / release unit 2 and the second heat storage / release unit 3 are any one of a fixed bed, a bubbling bed, a fluidized bed, a porous medium or a honeycomb ceramic.
[0086] The storage tanks of the first heat storage / release unit 2 and the second heat storage / release unit 3 are of different types. According to actual conditions, a storage tank with high system operation efficiency is selected to improve applicability.
[0087] Here, the first heat storage / release unit 2 undergoes an endothermic reaction as an example for illustration.
[0088] like Figure 1 As shown, low-temperature solar energy is concentrated and collected through heliostats to form high-temperature solar energy. The low-temperature and low-pressure heat transfer fluid carbon dioxide (~400°C, 1-3MPa) flowing out of the first storage / release unit 2 enters the solar thermal absorber 1 and is heated by the high-temperature solar energy. The heated carbon dioxide gas (~550°C, 1-3MPa) enters the first storage / release unit 2 to heat the metal carbonate. Taking sodium magnesium carbonate (MgNa2(CO3)2) as an example, the metal carbonate undergoes a decomposition reaction when heated, as shown in reaction equation (1), and the thermal energy is stored in the form of chemical energy.
[0089] In order to maintain a stable pressure in the first loop 151, a back pressure valve 12 is installed on the branch of the first loop 151. When the pressure value in the first loop 151 exceeds the threshold value set by the back pressure valve 12, the carbon dioxide gas generated by thermal decomposition will be discharged through the back pressure valve 12, and the remaining carbon dioxide gas will continue to be used as a heat transfer fluid for energy storage circulation. The carbon dioxide gas discharged through the back pressure valve 12 is cooled by the heat exchanger 4 and pressurized to ~7MPa by the pre-compressor 5, and then enters the gas storage tank 6 for storage, and is mixed with the supercritical carbon dioxide that has passed through the cooler 10 of the Brayton cycle system, and enters the compressor 9 together to be pressurized to ~25Mpa. The pressurized carbon dioxide gas is heated by the heat exchanger 4 and the regenerator 11, and enters the second storage / release unit 3 to react with the metal oxide in the second storage / release unit 3, as shown in reaction equation (2). The heat released by the reaction heats the high-pressure carbon dioxide fluid to ~700°C, and the supercritical carbon dioxide (~700°C, 25MPa) flowing out of the second storage / release unit 3 enters the turbine 7 to perform work, and drives the generator 8 to output electrical energy to the outside, performing work in a cycle.
[0090] After the second heat storage / release unit 3 completes heat release, the storage and release modules can be switched through the loop switching device 18, the valve between the first heat storage / release unit 2 and the solar thermal absorber 1 is closed, and the valve connecting the first heat storage / release unit 2 and the Brayton cycle system 17 is opened. At the same time, the valve between the second heat storage / release unit 3 and the Brayton cycle system 17 is closed, and the valve connecting the second heat storage / release unit 3 and the solar thermal absorber 1 is opened to complete the switching of the storage and release modules, and this cycle is repeated to ensure that the power cycle output power is stable and continuous.
[0091] MgNa 2 (CO3 ) 2 →MgO+Na 2 CO 3 +CO 2 (1)
[0092] MgO+Na 2 CO 3 +CO 2 →MgNa 2 (CO 3 ) 2 (2)
[0093] The circuit switching device 18 switches the first heat storage / release unit 2 to the second circuit 152, and the first heat storage / release unit 2 is connected to the Brayton cycle system 17;
[0094] The first heat storage / release unit 2 releases energy by utilizing an exothermic reaction occurring at a second temperature higher than the first temperature and a second pressure higher than the first pressure;
[0095] The circuit switching device 18 switches the second heat storage / release unit 3 to the first circuit 151, and the second heat storage / release unit 3 is connected to the solar thermal absorber 1 and is arranged downstream of the flow path of the solar thermal absorber 1;
[0096] The second heat storage / release unit 3 stores energy by utilizing an endothermic reaction occurring at a first temperature and a first pressure.
[0097] Because the first heat storage / release unit 2 is placed in the first circuit 151 before switching to the second circuit 152, an endothermic reaction occurs, and the first solid matter in the first heat storage / release unit 2 is decomposed to generate a second solid matter. Before the second heat storage / release unit 3 is switched to the first circuit 151, it is placed in the second circuit 151, an exothermic reaction occurs, and the second solid matter in the second heat storage / release unit 3 is combined with the medium to generate the first solid matter. In addition, because the circuit switching device 18 switches the first heat storage / release unit 2 and the second heat storage / release unit 3, after switching, The first heat storage / release unit 2 is connected to the Brayton cycle system 17, and the second heat storage / release unit 3 is connected to the solar thermal absorber 1. Because the second solid substance and the medium in the first heat storage / release unit 2 are combined to generate the first solid substance and release heat, the medium in the second loop 152 is heated to a temperature of a working medium sufficient to drive the turbine 7 to do work. Because the first solid substance in the second heat storage / release unit 3 is decomposed to generate the second solid substance and the medium and absorb heat, the medium in the first loop 151 circulates in the first loop 151 to transfer heat.
[0098] Embodiment 1 of the present invention further provides a solar power generation method, comprising the following steps:
[0099] A medium flow path for accommodating a medium circulating in a solar power generation system is provided, wherein the medium flow path includes a first loop and a second loop, wherein the first loop is connected to a solar thermal absorber and a first heat storage / release unit, and the second loop is connected to a Brayton cycle system and a second heat storage / release unit, and the first heat storage / release unit is arranged downstream of the flow path of the solar thermal absorber;
[0100] Energy is stored by utilizing an endothermic reaction occurring at a first temperature and a first pressure, the medium in the first loop serves as a heat transfer medium, and the endothermic reaction decomposes the first solid substance into a second solid substance and the medium;
[0101] The generated medium is introduced into the first circuit;
[0102] Energy is released by utilizing an exothermic reaction occurring at a second temperature higher than the first temperature and a second pressure higher than the first pressure, wherein the exothermic reaction is a reverse reaction of the endothermic reaction, and the exothermic reaction generates the first solid substance by combining the second solid substance with the medium in the second circuit;
[0103] Using a compressor of the Brayton cycle system, the medium in the second circuit is compressed and supplied to the second heat storage / release unit;
[0104] Using a turbine of the Brayton cycle system to receive the medium flowing out of the second heat storage / release unit, and using the flowing out medium as a working medium;
[0105] By using a pressure regulating unit connecting the first circuit and the second circuit, the gas pressure in the first circuit is stabilized below a specified threshold value by transporting the medium in the first circuit to the second circuit.
[0106] Furthermore, the method further comprises the following steps:
[0107] The first heat storage / release unit is switched to the second circuit so that it occupies the original position of the second heat storage / release unit, and the second heat storage / release unit is switched to the first circuit so that it occupies the original position of the first heat storage / release unit.
[0108] Embodiment 2
[0109] Embodiment 2 of the present invention also relates to a solar power generation system based on MgNa2(CO3)2 / MgO-Na2CO3 energy storage, which differs from Embodiment 1 in that the Brayton cycle arrangement is different.
[0110] Preferably, the Brayton cycle system 17 is any one of a simple Brayton cycle system, a recompression Brayton cycle system, a recompression partially cooled Brayton cycle system or a recompression inter-cooled Brayton cycle system.
[0111] The selection and coordination of different Brayton cycle systems 17 improve the overall operating efficiency. For example, the difference between the operating effect of the recompression partial cooling Brayton cycle system and the recompression intermediate cooling Brayton unit and the recompression Brayton cycle system is that the overall efficiency is improved and it is suitable for use in larger pressure ratio systems.
[0112] Figure 2 The system shown includes a recompression Brayton cycle system, which is different from the first embodiment in that the compressor 9 in this embodiment includes a main compressor 91 and a recompressor 92 , and the regenerator 11 includes a high-temperature regenerator 111 and a low-temperature regenerator 112 .
[0113] The supercritical carbon dioxide entering the regenerator 11 first enters the high-temperature regenerator 111 and then enters the low-temperature regenerator 112. The supercritical carbon dioxide flowing out of the low-temperature regenerator 112 is divided into two fluids. One fluid is cooled by the cooler 10, pressurized by the main compressor 91, heated by the low-temperature regenerator 112, and mixed with the other supercritical carbon dioxide fluid pressurized by the re-compressor 92, preheated by the heat exchanger 4, and enters the high-temperature regenerator 111.
[0114] Figure 3 The system shown includes a recompression partial cooling Brayton cycle system, which is different from the above-mentioned recompression Brayton cycle system implementation method in that a first compressor 13 and an intercooler 14 are added in this implementation method. The first compressor 13 is located before the main compressor 91 and the recompressor 92, and the intercooler 14 is located between the first compressor 13 and the main compressor 91. The supercritical carbon dioxide flowing out of the low-temperature regenerator 112 is first cooled by the cooler 10, and then enters the first compressor 13 for pressurization. The pressurized supercritical carbon dioxide fluid is divided into two fluids. One fluid is cooled by the intercooler 14, pressurized by the main compressor 91, heated by the low-temperature regenerator 112, and mixed with the other supercritical carbon dioxide fluid pressurized by the recompressor 92, heated by the heat exchanger 4, and enters the high-temperature regenerator 111.
[0115] Figure 4 The system shown includes a recompression intercooling Brayton cycle system, which is different from the above-mentioned compression Brayton cycle system implementation in that a first compressor 13 and an intercooler 14 are added in this implementation, and the first compressor 13 is located after the cooler 10 and before the intercooler 14, and the intercooler 14 is located between the first compressor 13 and the main compressor 91.
[0116] The supercritical carbon dioxide flowing out of the low-temperature regenerator 112 is divided into two fluids. One fluid is cooled by the cooler 10, pressurized by the first compressor 13, cooled by the intermediate cooler 14, pressurized by the main compressor 91, heated by the low-temperature regenerator 112, and mixed with the other supercritical carbon dioxide pressurized by the re-compressor 92, heated by the heat exchanger 4, and enters the high-temperature regenerator 111.
[0117] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. A solar power generation system having a medium flow path for accommodating a medium circulating in the solar power generation system, characterized in that: The medium flow path includes a first loop and a second loop, wherein: The first circuit is connected to the solar thermal absorber and the first heat storage / release unit. The first heat storage / release unit is disposed downstream of the flow path of the solar thermal absorber and stores energy by utilizing an endothermic reaction occurring at a first temperature and a first pressure; The medium acts as a heat transfer medium in the first circuit; The endothermic reaction decomposes the first solid substance into a second solid substance and the medium, and the generated medium flows into the first loop; The second loop is connected to the Brayton cycle system and the second heat storage / release unit. The second heat storage / release unit releases energy by utilizing an exothermic reaction occurring at a second temperature higher than the first temperature and a second pressure higher than the first pressure; The exothermic reaction is a reverse reaction of the endothermic reaction, and the exothermic reaction generates the first solid substance by the combination of the second solid substance and the medium in the second circuit; The compressor of the Brayton cycle system compresses the medium in the second circuit and supplies it to the second heat storage / release unit; The turbine of the Brayton cycle system receives the medium flowing out from the second heat storage / release unit and uses the flowing out medium as a working medium; The medium flow path also includes A pressure regulating unit connects the first circuit and the second circuit, and the pressure regulating unit can stabilize the air pressure in the first circuit below a specified threshold by transporting the medium in the first circuit to the second circuit.
2. The solar power generation system according to claim 1, characterized in that: Also includes A circuit switching device, wherein the circuit switching device is capable of switching the first heat storage / release unit to the second circuit so that it occupies the original position of the second heat storage / release unit, and switching the second heat storage / release unit to the first circuit so that it occupies the original position of the first heat storage / release unit.
3. The solar power generation system according to claim 1, characterized in that: The voltage regulating unit comprises a back pressure valve connected to the first circuit; an air storage tank, disposed in the medium flow path between the back pressure valve and the second circuit; A pre-compressor is arranged in the medium flow path between the back pressure valve and the gas storage tank.
4. The solar power generation system according to claim 3, characterized in that: The outlet of the gas storage tank is connected to the inlet of the compressor of the Brayton cycle system, and the medium flowing out of the gas storage tank is merged into the compressor together with the medium from the cooler of the Brayton cycle system.
5. The solar power generation system according to claim 4, characterized in that: Also includes A heat exchanger, wherein the inlet of the hot fluid side of the heat exchanger is connected to the back pressure valve, and the inlet of the cold fluid side of the heat exchanger is connected to the outlet of the compressor.
6. The solar power generation system according to claim 5, characterized in that: The second circuit also includes A regenerator, wherein the inlet of the hot fluid side of the regenerator is connected to the outlet of the turbine, and the inlet of the cold fluid side of the regenerator is connected to the outlet of the cold fluid side of the heat exchanger.
7. The solar power generation system according to claim 1, characterized in that: The heat transfer medium is carbon dioxide gas, the working medium is supercritical carbon dioxide, and the first solid substance is metal carbonate or a mixture containing metal carbonate.
8. The solar power generation system according to claim 1, characterized in that: The focusing system of the solar thermal absorber is one or more of a tower focusing system, a dish focusing system, a trough focusing system or a linear Fresnel focusing system.
9. A solar power generation method, characterized in that: The following steps are involved: Providing a medium flow path for accommodating a medium circulating in the solar power generation system, the medium flow path includes a first loop and a second loop, wherein the first loop is connected to a solar thermal absorber and a first heat storage / release unit, the second loop is connected to a Brayton cycle system and a second heat storage / release unit, and the first heat storage / release unit is arranged downstream of the flow path of the solar thermal absorber; Energy is stored by utilizing an endothermic reaction occurring at a first temperature and a first pressure, the medium serving as a heat transfer medium in the first loop, and the endothermic reaction decomposes the first solid substance into a second solid substance and the medium; Merging the generated medium into the first circuit; releasing energy by utilizing an exothermic reaction occurring at a second temperature higher than the first temperature and a second pressure higher than the first pressure, wherein the exothermic reaction is a reverse reaction of the endothermic reaction, and the exothermic reaction generates the first solid substance by combining the second solid substance with the medium in the second circuit; Using the compressor of the Brayton cycle system, compressing the medium in the second circuit and supplying it to the second heat storage / release unit; Using the turbine of the Brayton cycle system to receive the medium flowing out of the second heat storage / release unit, and using the flowing out medium as a working medium; The pressure regulating unit connecting the first circuit and the second circuit is used to stabilize the gas pressure in the first circuit below a predetermined threshold value by transporting the medium in the first circuit to the second circuit.
10. The solar power generation method according to claim 9, characterized in that: The following steps are also included: The first heat storage / release unit is switched to the second circuit so that it occupies the original position of the second heat storage / release unit, and the second heat storage / release unit is switched to the first circuit so that it occupies the original position of the first heat storage / release unit.