Solar power generation system

Abstract

The present invention belongs to the field of solar energy. In view of the problems of complex structure, poor stability and low energy utilization rate of solar power generation system, the present invention provides a solar power generation system, including a heliostat field, a solar collector, a turbine expander, a generator, a precooler, a compressor, a heat exchanger, a first valve, a second valve, a low-pressure gas storage tank, a high-pressure thermal storage gas tank, a supplementary heat device, and a third valve. Diversion is performed before the turbine expander, and the excess solar energy is converted into the pressure energy and thermal energy of high-pressure carbon dioxide and stored through the high-pressure thermal storage gas tank. At night, the carbon dioxide in the high-pressure thermal storage gas tank is released to enter the turbine to do work, and the high-temperature and low-pressure working fluid after doing work enters the low-pressure gas tank for storage, thereby realizing the utilization of excess solar energy and maintaining the continuous use of the solar power generation system at night.

Description

Technical Field

[0001] The invention belongs to the technical field of solar energy, and in particular relates to a solar power generation system. Background Art

[0002] Solar thermal power generation technology is a general term for a power generation technology that converts solar energy into thermal energy through certain technical means, and then uses a certain thermodynamic cycle method to do work, so that the generator generates electricity. It is a high-quality way to utilize solar energy. At present, there are many thermodynamic cycles used in solar power generation, among which the supercritical carbon dioxide (S-CO2) Brayton cycle has many advantages. As the only circulating working fluid in this cycle, supercritical carbon dioxide has a low critical point (7.38MPa, 304K), which is easier to reach a supercritical state than other working fluids such as water, which is conducive to engineering applications; it has the characteristics of both liquid and gas, with high density, high heat transfer efficiency, strong work capacity, low viscosity, strong fluidity, and low system cycle loss; and in the entire power system, the cycle operates in a supercritical state, the working fluid remains dense, making the turbine expander and compressor smaller than traditional power cycles.

[0003] However, since the intensity of solar radiation fluctuates with time, weather and other factors, the output parameters of most traditional solar thermal power generation systems cannot reach the set values ​​when the weather conditions are bad or at night, affecting the normal use of the solar energy system. Therefore, reducing or even eliminating the impact of fluctuations in solar radiation intensity on the solar energy system is an urgent problem to be solved in the field of solar thermal power generation. In response to the need for improvement of this technology, researchers have proposed different solutions:

[0004] Solution 1: Patent application number CN201310743891.5 proposes a new solution based on molten salt heat storage to solve the heat storage problem of solar thermal power generation system: using molten salt with a lower melting point as the heat absorbing medium of the solar system, and introducing a binary salt as the working medium of the heat storage system to provide heat for the system when solar radiation is insufficient.

[0005] Solution 2: The patent application with application number CN202120988320.8 proposes a molten salt heat storage peak-shaving system for different turbine output power requirements. When the required turbine output power is small, the molten salt is heated by high-temperature working fluid and stored in a hot tank. When the required output power is large, the molten salt heat storage is used to heat the working fluid to achieve heat storage peak-shaving.

[0006] Solution 3: Patent application number CN201911169727.1 proposes a solution to address the problem of excess solar energy during the day in order to make full use of energy: coupling a compressed air energy storage system to a solar supercritical carbon dioxide Brayton cycle power generation system to fully utilize excess solar energy.

[0007] Solution 4: Patent application number CN201710243325.6 proposes a scheme for compressed supercritical carbon dioxide energy storage and heat storage in response to the changes in high and low loads of the power grid: electric energy is used to compress supercritical carbon dioxide during the low load period of the power grid, and the stored carbon dioxide is released during the peak load period to drive the turbine to do work, thereby achieving "peak shaving and valley filling".

[0008] These existing solutions have obvious problems in terms of system complexity, stability and power generation efficiency.

[0009] The method of adding molten salt heat storage to the solar thermal power generation system proposed in Scheme 1 has a single form of energy storage. When the solar radiation is weak, additional pressurizing equipment is required to increase the working fluid pressure to ensure the normal operation of the system. This leads to increased energy consumption of the system, reduced power generation efficiency, and poor economic performance.

[0010] The molten salt heat storage peak-shaving system proposed in Scheme 2 includes two molten salt heat storage systems, A and B. There are too many system components, which increases the complexity of the system, may increase the risk of system failure, and increase the system maintenance cost.

[0011] Scheme 3 proposes the method of adding a compressed air energy storage system to store excess solar energy during the day. This method requires filling the system with two working fluids, carbon dioxide and air, which increases the system operation and maintenance costs and increases the risk of working fluid leakage.

[0012] Although the energy storage scheme proposed in Scheme 4 achieves both heat storage and pressure storage, the high-temperature and high-pressure working fluid must first undergo a heat release process before being stored in a high-pressure gas storage tank, resulting in a complex system structure. The large number of heat exchange devices also reduces the system's economic efficiency. In addition, in this scheme, heat transfer oil is used as the heat transfer medium, and the temperature cannot be too high, resulting in a decrease in heat quality and a decrease in cycle efficiency.

[0013] Therefore, it is necessary to study a solar power generation system with simple structure, good stability and high energy utilization rate. Summary of the invention

[0014] In view of the above problems, the present invention provides a solar power generation system. On the basis of the traditional solar thermal power generation system based on the supercritical carbon dioxide Brayton cycle, the system performs diversion before the turbine expander, and converts the excess solar energy into the pressure energy and thermal energy of high-pressure carbon dioxide through the high-pressure thermal storage tank and stores it. The high-temperature and high-pressure working fluid after passing through the heat exchanger is stored in the high-pressure thermal storage tank, and at the same time, the high-temperature and low-pressure working fluid in the low-pressure tank is combined with the working fluid at the outlet of the turbine expander to enter other cycles. At night, the carbon dioxide in the high-pressure thermal storage tank is released to enter the turbine to do work, and the high-temperature and low-pressure working fluid after doing work enters the low-pressure gas tank for storage, thereby realizing the utilization of excess solar energy and maintaining the continuous use of the solar power generation system at night.

[0015] The technical solution of the present invention is as follows:

[0016] A solar power generation system, including a heliostat field, a solar collector, a turbo expander, a generator, a precooler, a compressor, a heat exchanger, a first valve, a second valve, a low-pressure gas storage tank, a high-pressure thermal storage tank, a supplementary heat device, and a third valve;

[0017] The heliostat field is connected to the solar collector, the outlet of the solar collector is connected to the inlet of the turbine expander, and the turbine expander is connected to the generator, the outlet of the turbine expander is connected to the inlet of the high-temperature side of the heat exchanger, a first valve is arranged on the connecting pipeline, the outlet of the high-temperature side of the heat exchanger is connected to the inlet of the precooler, the outlet of the precooler is connected to the inlet of the compressor, the outlet of the compressor is connected to the inlet of the low-temperature side of the heat exchanger, and the outlet of the low-temperature side of the heat exchanger is connected to the inlet of the solar collector; a supplementary heat device is arranged on the pipeline between the outlet of the solar collector and the inlet of the turbine expander, the pipeline is connected to the outlet of the supplementary heat device through a third valve, the inlet of the supplementary heat device is connected to the high-pressure heat storage gas tank, and the low-pressure gas tank is connected to the pipeline between the outlet of the turbine expander and the first valve through a second valve.

[0018] Furthermore, the make-up heat device is relocated on the pipeline between the solar collector inlet and the low-temperature side outlet of the heat exchanger, the make-up heat device inlet is connected to the high-pressure heat storage gas tank, and the make-up heat device outlet is connected to the fourth valve. The solar power generation system also includes a direct-heating heat accumulator, which is integrated into the solar collector. One end of the direct-heating heat accumulator is connected to the pipeline between the solar collector outlet and the turbine expander inlet, and the other end is connected to the pipeline between the solar collector inlet and the make-up heat device outlet through the third valve.

[0019] Furthermore, when the daytime light conditions are sufficient, the first valve is opened, and the second valve and the third valve are closed. The heat absorbed by the solar collector is used to heat the carbon dioxide fluid in the pipeline. The high-temperature fluid performs work in the turbine expander, driving the turbine expander to rotate, so that it generates electricity outward through the generator. After completing the work, the high-temperature, low-pressure supercritical carbon dioxide passes through the first valve, and then passes through the heat exchanger to recover the waste heat into the system, and then flows through the precooler to make the supercritical carbon dioxide fluid state reach near the critical point. The fluid flowing out of the precooler is compressed by the compressor, and after compression, it is heated by the heat exchanger, and after flowing out of the heat exchanger, it enters the solar collector to start a new round of circulation.

[0020] When there is excess solar energy during the day, the second valve and the third valve are opened, and part of the high-temperature and high-pressure supercritical carbon dioxide fluid flowing out of the solar collector passes through the third valve and the supplementary heat device to reach the high-pressure thermal storage tank for heat storage and gas storage. The carbon dioxide fluid in the low-pressure gas tank flows into the system through the second valve to supplement the reduced carbon dioxide flow in the circulation system. When the gas in the low-pressure gas tank is fully supplemented to the system, the storage capacity of the high-pressure thermal storage tank reaches the maximum, and the maximum value is the gas volume in the low-pressure gas tank. At this time, the second valve and the third valve are closed, and the compressed carbon dioxide energy storage system is completed.

[0021] When the lighting conditions are poor or there is no light at night, the first valve is closed, the second valve and the third valve are opened, and the high-pressure carbon dioxide fluid flows out from the high-pressure heat storage tank, passes through the heater and the third valve, and flows into the turbine to perform work, driving the turbine to rotate, so that it generates electricity through the generator. After completing the work, the low-pressure carbon dioxide gas flows into the low-pressure tank through the second valve. In this process, if the heat storage tank does not have enough heat, the heater will be turned on to assist in heating the carbon dioxide fluid.

[0022] Furthermore, during the day, when the sun heats the solar collector through the heliostat field, the heat accumulator is also heated to store heat; when the lighting conditions are poor or there is no lighting at night, the fourth valve is closed and the third valve is opened, and the high-pressure carbon dioxide fluid is released from the high-pressure gas storage tank, passes through the valve, passes through the heat accumulator, and then passes through the turbine to do work and finally returns to the low-pressure gas storage tank.

[0023] Beneficial effects:

[0024] (1) Compared with Solution 1, the present invention can store excess heat during the day, so that the system can be used at night when the lighting conditions are poor or there is no light.

[0025] (2) Compared with Scheme 2, the present invention not only stores heat but also stores high-pressure gas, so that when the system is used at night under poor lighting conditions or without lighting, no additional equipment is required to increase the carbon dioxide pressure, thereby improving the efficiency of the system.

[0026] (3) Compared with Scheme 3, the present invention does not need to add some additional systems to run synchronously with it, which reduces the complexity of the overall structure of the cycle power generation system and saves production and maintenance costs.

[0027] (4) Compared with Scheme 4, the present invention does not require an additional compressor or additional air as a working fluid. The energy storage and work performance of the entire system are completed by carbon dioxide as a working fluid, which greatly reduces the structural complexity of the system and the possibility of working fluid leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic structural diagram of a solar power generation system according to Embodiment 1;

[0029] Figure 2 This is a schematic structural diagram of a solar power generation system according to Embodiment 2. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below with reference to specific embodiments.

[0031] Example 1

[0032] A solar power generation system, the main structure and connection relationship are as follows Figure 1 As shown, it includes a heliostat field 1, a solar collector 2, a turbo expander 3, a generator 4, a precooler 5, a compressor 6, a motor 7, a heat exchanger 8, a first valve 9, a second valve 10, a low-pressure gas storage tank 11, a high-pressure thermal storage tank 12, a supplementary heat device 13, and a third valve 14.

[0033] The heliostat field 1 is connected to the solar collector 2, the outlet of the solar collector 2 is connected to the inlet of the turbine expander 3, and the turbine expander 3 is connected to the generator 4, the outlet of the turbine expander 3 is connected to the inlet of the high temperature side of the heat exchanger 8, and the first valve 9 is arranged on the connecting pipeline, the outlet of the high temperature side of the heat exchanger 8 is connected to the inlet of the precooler 5, the outlet of the precooler 5 is connected to the inlet of the compressor 6, and the compressor 6 is connected to the motor 7, the outlet of the compressor 6 is connected to the inlet of the low temperature side of the heat exchanger 8, and the outlet of the low temperature side of the heat exchanger 8 is connected to the inlet of the solar collector 2. A supplementary heat device 13 is arranged on the pipeline between the outlet of the solar collector 2 and the inlet of the turbine expander 3, and the pipeline is connected to the outlet of the supplementary heat device 13 through the third valve 14, and the inlet of the supplementary heat device 13 is connected to the high pressure heat storage gas tank 12. The low pressure gas tank 11 is connected to the pipeline between the outlet of the turbine expander 3 and the first valve 9 through the second valve 10.

[0034] The solar supercritical carbon dioxide Brayton cycle operation process of the present invention is as follows:

[0035] When the daytime light conditions are sufficient, the heliostat field 1 collects sunlight to the solar collector 2 to absorb heat, and the absorbed heat is used to heat the carbon dioxide fluid in the pipeline to increase the temperature of the fluid. The high-temperature fluid performs work in the turbine expander 3, driving the turbine expander 3 to rotate, so that it generates electricity outward through the generator 4. After completing the work, the high-temperature, low-pressure supercritical carbon dioxide passes through the first valve 9, and then passes through the heat exchanger 8 to recover the waste heat into the system, and then flows through the precooler 5 to make the supercritical carbon dioxide fluid state reach the critical point, so as to reduce the compression work consumed by the compressor 6. The fluid flowing out of the precooler 5 is compressed by the compressor 6 under the drive of the motor 7, and after compression, it is heated by the heat exchanger 8, and after flowing out of the heat exchanger 8, it enters the solar collector 2 to start a new cycle.

[0036] When there is excess solar energy during the day, it is necessary to store excess energy on the basis of stabilizing the system's external power generation. At this time, based on the above cycle, the third valve 14 is opened, and the supplementary heat device 13 is in a closed state. After part of the high-temperature and high-pressure supercritical carbon dioxide fluid flows out of the solar collector 2, it passes through the third valve 14 and the supplementary heat device 13 to reach the high-pressure thermal storage gas tank 12 for heat storage and gas storage, and the high-temperature and high-pressure carbon dioxide fluid is stored. In order to avoid the reduction of carbon dioxide flow in the cycle caused by diversion and ensure the circulation flow, the second valve 10 is opened, and the carbon dioxide fluid in the low-pressure gas tank 11 flows into the system through the second valve 10 to supplement the carbon dioxide flow reduced by the circulation system. When the gas in the low-pressure gas tank 11 is fully supplemented to the system, the storage capacity of the high-pressure thermal storage gas tank 12 reaches the maximum, and the maximum value is the amount of gas in the low-pressure gas tank 11. At this time, the second valve 10 and the third valve 14 are closed, and the compressed carbon dioxide energy storage system is completed.

[0037] When the lighting conditions are poor or there is no light at night, the first valve 9 is closed, and the second valve 10 and the third valve 14 are opened. The high-pressure carbon dioxide fluid flows out of the high-pressure heat storage tank 12, passes through the supplementary heat device 13 and the third valve 14, and flows into the turbine 3 to perform work, driving the turbine 3 to rotate, so that it generates electricity through the generator 4. After the work is completed, the low-pressure carbon dioxide gas flows into the low-pressure gas storage tank 11 through the second valve 10, so as to be used during the next day. In this process, if the heat of the heat storage device is insufficient, the supplementary heat device 13 will be turned on to assist in heating the carbon dioxide fluid.

[0038] Example 2

[0039] Another structure of the present invention is as follows Figure 2 As shown, the energy storage circuit is improved on the basis of Example 1, and the supplementary heat device 13 is changed to the pipeline between the inlet of the solar collector 2 and the outlet of the low temperature side of the heat exchanger 8, the inlet of the supplementary heat device 13 is connected to the high-pressure heat storage gas tank 12, and the outlet of the supplementary heat device 13 is connected to the fourth valve 15. The solar power generation system also includes a direct heating type heat accumulator 16, which is integrated into the solar collector 2, one end of the direct heating type heat accumulator 16 is connected to the pipeline between the outlet of the solar collector 2 and the inlet of the turbine expander 3, and the other end is connected to the pipeline between the inlet of the solar collector 2 and the outlet of the supplementary heat device 13 through the third valve 14. When the sun heats the solar collector through the heliostat field during the day, the heat accumulator 16 is heated together to store heat. When the lighting conditions are poor or there is no lighting at night, the fourth valve 15 is closed and the third valve 14 is opened. The high-pressure carbon dioxide fluid is released from the high-pressure gas storage tank 12, passes through the valve 14, passes through the heat accumulator 16, and finally returns to the low-pressure gas storage tank 11 after passing through the turbine 3 to do work.

[0040] The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the protection scope determined by the claims of the present invention.

Claims

1. A solar power generation system, characterized in that: It includes a heliostat field, a solar collector, a turbine expander, a generator, a precooler, a compressor, a heat exchanger, a first valve, a second valve, a low-pressure gas storage tank, a high-pressure thermal storage tank, a supplementary heat device, and a third valve; The heliostat field is connected to the solar collector, the outlet of the solar collector is connected to the inlet of the turbine expander, and the turbine expander is connected to the generator, the outlet of the turbine expander is connected to the inlet of the high-temperature side of the heat exchanger, a first valve is arranged on the connecting pipeline, the outlet of the high-temperature side of the heat exchanger is connected to the inlet of the precooler, the outlet of the precooler is connected to the inlet of the compressor, the outlet of the compressor is connected to the inlet of the low-temperature side of the heat exchanger, and the outlet of the low-temperature side of the heat exchanger is connected to the inlet of the solar collector; a supplementary heat device is arranged on the pipeline between the outlet of the solar collector and the inlet of the turbine expander, the pipeline is connected to the outlet of the supplementary heat device through a third valve, the inlet of the supplementary heat device is connected to the high-pressure heat storage gas tank, and the low-pressure gas tank is connected to the pipeline between the outlet of the turbine expander and the first valve through a second valve; The supplementary heat device is re-arranged on the pipeline between the solar collector inlet and the low-temperature side outlet of the heat exchanger, the supplementary heat device inlet is connected to the high-pressure gas storage tank, and the supplementary heat device outlet is connected to the fourth valve. The solar power generation system also includes a direct heating heat accumulator, which is integrated into the solar collector, one end of the direct heating heat accumulator is connected to the pipeline between the solar collector outlet and the turbine expander inlet, and the other end is connected to the pipeline between the solar collector inlet and the supplementary heat device outlet through the third valve; When the daytime light conditions are sufficient, the first valve is opened, and the second and third valves are closed. The heat absorbed by the solar collector is used to heat the carbon dioxide fluid in the pipeline. The high-temperature fluid performs work in the turbine expander, driving the turbine expander to rotate, so that it generates electricity through the generator. After completing the work, the high-temperature, low-pressure supercritical carbon dioxide passes through the first valve, and then passes through the heat exchanger to recover the waste heat into the system. After that, it flows through the precooler to make the supercritical carbon dioxide fluid state reach near the critical point. The fluid flowing out of the precooler is compressed by the compressor, and after compression, it is heated by the heat exchanger. After flowing out of the heat exchanger, it enters the solar collector to start a new cycle. When there is excess solar energy during the day, the second valve and the third valve are opened, and part of the high-temperature and high-pressure supercritical carbon dioxide fluid flowing out of the solar collector passes through the third valve and the supplementary heat device to reach the high-pressure thermal storage tank for heat storage and gas storage. The carbon dioxide fluid in the low-pressure gas tank flows into the system through the second valve to supplement the reduced carbon dioxide flow in the circulation system. When the gas in the low-pressure gas tank is fully supplemented to the system, the storage capacity of the high-pressure thermal storage tank reaches the maximum, and the maximum value is the gas volume in the low-pressure gas tank. At this time, the second valve and the third valve are closed, and the compressed carbon dioxide energy storage system is completed. When the lighting conditions are poor or there is no light at night, the first valve is closed, the second valve and the third valve are opened, and the high-pressure carbon dioxide fluid flows out from the high-pressure heat storage tank, passes through the heater and the third valve, and flows into the turbine to perform work, driving the turbine to rotate, so that it generates electricity through the generator. After completing the work, the low-pressure carbon dioxide gas flows into the low-pressure tank through the second valve. In this process, if the heat storage tank does not have enough heat, the heater will be turned on to assist in heating the carbon dioxide fluid.

2. The solar power generation system according to claim 1, characterized in that: The compressor is connected to a motor to obtain kinetic energy.

3. The solar power generation system according to claim 1, characterized in that: During the day, when the sun passes through the heliostat field to heat the solar collector, it also heats the heat accumulator to store heat; when the lighting conditions are poor or there is no light at night, the fourth valve is closed and the third valve is opened, and the high-pressure carbon dioxide fluid is released from the high-pressure gas storage tank and passes through the valve through the heat accumulator, and finally returns to the low-pressure gas storage tank after passing through the turbine to do work.

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