Solar power generation system and method

Abstract

The present invention discloses a solar power generation system and method, which relates to the technical field of solar thermal power stations. It includes a supercritical carbon dioxide circulation loop and a second solar collector field; the supercritical carbon dioxide circulation loop includes a precooler, a main compressor, a low-temperature regenerator, a recompressor, a high-temperature regenerator, a heat exchanger, a high-pressure turbine, a reheater, a low-pressure turbine, a generator, a first solar collector field and a preheater. The first solar collector field and the preheater are redundant with each other. When there is sufficient sunlight, the first solar collector field can use solar energy to directly heat the carbon dioxide circulating inside it. When there is insufficient sunlight, the preheater can be used to heat the carbon dioxide, thereby making the most of solar energy resources. The diameters of the mother pipes are set in sections in the first solar collector field and the second solar collector field to achieve self-balancing of the flow in the pipeline, reduce the use of valves, and reduce the construction investment cost of the solar thermal power station.

Description

Technical Field

[0001] The present invention relates to the technical field of photothermal power stations, and in particular to a solar power generation system and method. Background Art

[0002] Solar thermal power generation has the advantage of large-scale heat storage. Under good weather conditions, it can generate electricity continuously during the day and at night. It can undertake both peak-shaving tasks and base loads, and has great advantages in increasing the proportion of renewable energy power generation.

[0003] Typical solar thermal collection systems include trough, tower, linear Fresnel, and dish. Among them, trough and tower have entered the commercial development stage, linear Fresnel is in the pilot project development stage, and dish is in the demonstration stage. The working fluids of solar thermal collection systems include thermal oil, molten salt, and water. Molten salt has many advantages as a heat collection, heat storage, and heat exchange medium and is widely used. On the power generation side, the most widely used cycle is the steam Rankine cycle, while the supercritical carbon dioxide Brayton cycle has attracted much attention due to its high cycle efficiency and is expected to become a circulation system for solar thermal power generation. However, the efficient coupling of the supercritical carbon dioxide Brayton cycle and the thermal collection system is a key issue in the development of solar thermal power generation.

[0004] The difficulty of efficient coupling lies in the fact that the solar thermal power station adopts an advanced power generation cycle, namely the supercritical carbon dioxide Brayton cycle. While improving the power generation efficiency, the temperature of supercritical carbon dioxide is still relatively low when it enters the heat exchanger relying solely on heat recovery. The temperature in the heat exchanger may still drop below the freezing point of the molten salt after heat exchange with the molten salt, causing freezing of the molten salt. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a solar power generation system and method in view of the shortcomings of the existing technology, add a medium-temperature thermal collection system, and use photothermal collection to directly heat the supercritical carbon dioxide with a lower temperature to a temperature above the freezing point of the molten salt, so as to ensure that the temperature of the molten salt in the heat exchanger is always above its freezing point.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a solar power generation system, including a supercritical carbon dioxide circulation loop and a second heat collection field; the supercritical carbon dioxide circulation loop includes a precooler, a main compressor, a low-temperature regenerator, a recompressor, a high-temperature regenerator, a heat exchanger, a high-pressure turbine, a reheater, a low-pressure turbine and a generator. The output end of the high-temperature regenerator tube side is connected to the input end of the low-temperature regenerator tube side, and the output end of the low-temperature regenerator tube side is respectively connected to the input end of the precooler and the recompressor; the output end of the precooler is connected to the input end of the main compressor; the output end of the main compressor is connected to the input end of the low-temperature regenerator shell side, and the output end of the low-temperature regenerator shell side is connected to the output end of the recompressor and then connected to the input end of the high-temperature regenerator shell side. The generator, the low-pressure turbine and the high-pressure turbine are coaxially connected, the output end of the reheater tube side is connected to the input end of the low-pressure turbine, and the output end of the heat exchanger tube side is connected to the input end of the high-pressure turbine.

[0007] The supercritical carbon dioxide circulation loop also includes a first heat collecting field and a preheater; the output end of the high-temperature reheater shell side is respectively connected to the input end of the first heat collecting field and the input end of the preheater tube side; the output end of the first heat collecting field is connected to the output end of the preheater tube side and then connected to the input end of the heat exchanger tube side; the output end of the heat exchanger tube side is connected to the input end of the high-pressure turbine, and the output end of the high-pressure turbine is respectively connected to the input end of the preheater shell side and the input end of the reheater tube side; the output end of the preheater shell side is connected to the input end of the high-temperature reheater tube side.

[0008] The first heat collection field comprises a first mother pipe, a second mother pipe and n1 first heat collection loops, the first mother pipe and the second mother pipe are arranged in the same route; the n1 first heat collection loops are arranged in parallel between the first mother pipe and the second mother pipe; the first mother pipe or the second mother pipe each comprises j pipe sections, j=1, 2, ..., n1-1;

[0009] The inner diameter of the jth pipe section of the first mother pipe is D c1,j , and its calculation formula is: m1 is the total flow rate of supercritical carbon dioxide flowing in the first collector field, D1 is the maximum diameter of the first mother pipe and the second mother pipe, M c1,j is the supercritical carbon dioxide flow rate of the jth pipe section of the first mother pipe;

[0010] The inner diameter of the jth pipe section of the second mother pipe is D h1,j , and its calculation formula is λ1 is the resistance loss coefficient of supercritical carbon dioxide along the way, w1 is the length of each section of the first mother pipe or the second mother pipe, ρ c1 is the density of supercritical carbon dioxide in the first mother tube; ξ c1,j is the local resistance loss coefficient at the first mother pipe tee, ρ h1 is the density of supercritical carbon dioxide in the second mother tube; ξ h1,j is the local resistance loss coefficient at the second mother pipe tee, M h1,j is the supercritical carbon dioxide flow rate of the j-th pipe section of the second mother pipe.

[0011] The first solar collector field and the preheater are redundant. When there is sufficient sunlight, the first solar collector field can use solar energy to directly heat the carbon dioxide circulating inside it. When there is insufficient sunlight, the preheater can be used to heat the carbon dioxide, making maximum use of solar energy resources. In the first solar collector field, the first mother pipe and the second mother pipe section are arranged with their pipe diameters so that the carbon dioxide flow in each of the first solar collector loops is balanced to achieve uniform heating. Both of the above points can ensure that the carbon dioxide maintains a high temperature when entering the tube side of the heat exchanger, preventing the molten salt on the shell side of the heat exchanger from freezing.

[0012] Specifically, the supercritical carbon dioxide flow rate M of the j-th pipe section of the first mother pipe c1,j The calculation formula is M c1,j =M c1,j-1 -m 1,j ;m 1,j is the actual supercritical carbon dioxide mass flow rate in the first collector loop of the jth article, M c1,0 =m1; supercritical carbon dioxide flow rate M of the jth section of the second mother pipe h1,j The calculation formula is M h1,j =M h1,j-1 +m 1,j , M h1,0 =0.

[0013] Specifically, the local resistance loss coefficient ξ at the first mother pipe tee c1,j The local resistance loss coefficient ξ at the second mother pipe tee h1,j The value is 20λ1. K1 is the roughness of the pipeline; d1 is the inner diameter of the first heat collection loop pipe; Re1 is the first Reynolds number.

[0014] Specifically, it also includes a first valve, a second valve and a third valve. The first valve is arranged at the input end of the first collector field; the second valve is arranged at the input end of the preheater tube side; and the third valve is arranged at the input end of the preheater shell side.

[0015] Specifically, the second solar collector field includes a cold molten salt pump, a cold molten salt tank, a cold molten salt mother pipe, a hot molten salt pump, a hot molten salt tank, a hot molten salt mother pipe and n2 second solar collector circuits. The outlet of the hot molten salt mother pipe is respectively connected to the hot molten salt pump and the hot molten salt tank; the output end of the hot molten salt pump is respectively connected to the input end of the heat exchanger shell side and the input end of the reheater shell side, and the output end of the heat exchanger shell side is connected to the output end of the reheater shell side and then connected to the cold molten salt tank; the cold molten salt tank is connected to the inlet of the cold molten salt mother pipe through the cold molten salt pump.

[0016] The cold molten salt mother pipe and the hot molten salt mother pipe are arranged in the same route; n2 second heat collection loops are arranged in parallel between the cold molten salt mother pipe and the hot molten salt mother pipe. The cold molten salt mother pipe includes i pipe sections, i = 1, 2, ..., n2-1. The inner diameter value of the i-th pipe section of the cold molten salt mother pipe is D c2,i , and its calculation formula is: m2 is the total flow rate of molten salt flowing in the collector field, D2 is the maximum diameter of the mother pipe, M c2,i is the molten salt flow rate of the i-th section of the cold molten salt main pipe.

[0017] The diameters of the cold molten salt main pipe and the hot molten salt main pipe branch sections are set so that the molten salt flow in each of the second heat collection loops is balanced to achieve uniform heating, and a higher temperature is ensured when the molten salt flows into the shell side of the heat exchanger.

[0018] The inner diameter of the ith section of the molten salt main pipe is D h2,i , and its calculation formula is λ2 is the resistance loss coefficient of binary molten salt along the way, ρ c2 is the density of cold molten salt; w2 is the length of each section of cold / hot molten salt mother pipe, ξ c2,i is the local resistance loss coefficient at the tee of the cold molten salt mother pipe, ρ h2 is the density of molten salt; h2,i is the local resistance loss coefficient at the tee of the hot molten salt mother pipe, M h2,i is the molten salt flow rate of the i-th section of the hot molten salt mother pipe.

[0019] Specifically, the molten salt flow rate M of the i-th section of the cold molten salt mother pipe is c2,i The calculation formula is M c2,i =M c2,i-1 -m 2,i ;m 2,i is the actual molten salt mass flow rate in the second collector loop of the i-th article, M c2,0 = m2; molten salt flow rate M of the ith section of the hot molten salt main pipe h2,i The calculation formula is M h2,i =M h2,i-1 +m 2,i , Mh2,0 =0.

[0020] Specifically, the local resistance loss coefficient ξ at the tee of the cold molten salt mother pipe is c2,i Local resistance loss coefficient ξ at the tee of the hot molten salt main pipe h2,i The value is 20λ2. K2 is the roughness of the pipeline; d2 is the inner diameter of the second heat collection loop pipe; Re2 is the second Reynolds number.

[0021] Based on the same technical concept, the present invention also provides a power generation method of a solar power generation system, when the sunlight is sufficient, the first valve is opened, and the second valve and the third valve are closed. When the sunlight is insufficient, the first valve is closed, and the second valve and the third valve are opened.

[0022] The sufficient sunshine refers to a situation where there is sunshine 1 and the weather is "sunny" or "a little cloudy", and the insufficient sunshine refers to a situation where the weather is "cloudy" or "overcast" or "rainy".

[0023] Refer to the "Explanation of Weather Forecast Terms" published by Ji Wenchang in the "China Meteorological News" on August 25, 1989 ( http: / / www.cma.gov.cn / kppd / kppdqxsj / kppdqxgc / 201212 / t20121212_195901.html ): A sky without clouds or with scattered clouds but with cloud cover less than 1 / 10 of the sky area is called "clear". Sometimes there are very thin high clouds in the sky, but the sun can shine through, which is also called "clear". A situation where the amount of medium and low clouds occupies 1 / 10 to 3 / 10 of the sky area or the amount of high clouds occupies 4 / 10 to 5 / 10 of the sky area is called "few clouds". A situation where the amount of medium and low clouds occupies 4 / 10 to 7 / 10 of the sky area or the amount of high clouds occupies 6 / 10 to 10 / 10 of the sky area is called "overcast". When the amount of medium and low clouds occupies 8 / 10 or more of the sky area and the sun cannot shine through or shines through the clouds very little, it is called "overcast". A 24-hour precipitation of 0.1 to 9.9 mm or more is called "rain".

[0024] When there is sufficient sunlight, the first valve is opened, the first solar collector field works, the second valve and the third valve are closed, the preheater does not work, and the solar energy resources are fully utilized to heat the carbon dioxide.

[0025] The carbon dioxide working medium flows out from the tube side of the low-temperature regenerator and is divided. One part is cooled and reduced in temperature by the precooler, and then compressed and increased in pressure by the main compressor, and then flows into the shell side of the low-temperature regenerator to absorb heat and increase in temperature; the other part is compressed and increased in pressure by the recompressor, and then merges with the carbon dioxide at the output end of the shell side of the low-temperature regenerator to flow into the shell side of the high-temperature regenerator to absorb heat and increase in temperature, and then flows into the first collector field for preheating and temperature increase, and then flows into the tube side of the heat exchanger. At this time, the shell side of the heat exchanger is passed by the hot molten salt heated by the second collector field, and the high temperature of the molten salt can indirectly further heat the carbon dioxide on the tube side of the heat exchanger. The further heated carbon dioxide enters the high-pressure turbine to expand and do work, and then is exhausted to the reheater through the high-pressure turbine. After the reheater reheats the carbon dioxide, the carbon dioxide enters the low-pressure turbine to do work, thereby driving the generator to generate electricity. The carbon dioxide working medium after doing work flows into the tube side of the high-temperature regenerator and the tube side of the low-temperature regenerator in turn to release heat and reduce in temperature, and then enters the next cycle.

[0026] When the sunlight is insufficient, the first valve is closed and the first solar collector does not work. The second valve and the third valve are closed and the preheater works, which can ensure that the carbon dioxide can be heated to a temperature above the freezing point of the molten salt when the sunlight is insufficient.

[0027] The carbon dioxide working medium flows out from the tube side of the low-temperature regenerator and is divided. One part is cooled and reduced in temperature by the precooler, and then compressed and increased in pressure by the main compressor, and then flows into the shell side of the low-temperature regenerator to absorb heat and increase in temperature; the other part is compressed and increased in pressure by the recompressor, and then merges with the carbon dioxide at the output end of the shell side of the low-temperature regenerator and flows into the shell side of the high-temperature regenerator to absorb heat and increase in temperature, and then flows into the preheater for preheating and temperature increase, and then flows into the tube side of the heat exchanger. At this time, the shell side of the heat exchanger is passed by the hot molten salt heated by the second solar collector. The high temperature of the molten salt can indirectly further heat the carbon dioxide on the tube side of the heat exchanger. The further heated carbon dioxide enters the high-pressure turbine to expand and do work, and then is exhausted to the reheater through the high-pressure turbine. After the reheater reheats the carbon dioxide, the carbon dioxide enters the low-pressure turbine to do work, thereby driving the generator to generate electricity. The carbon dioxide working medium after doing work flows into the tube side of the high-temperature regenerator and the tube side of the low-temperature regenerator in turn to release heat and reduce in temperature, and then enters the next cycle.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention improves the power generation efficiency while preheating the carbon dioxide and setting up the first collector field and the preheater. When the carbon dioxide reaches the heat exchanger tube side, it maintains a relatively high temperature, which not only efficiently utilizes solar energy resources, but also greatly reduces the risk of molten salt freezing on the shell side of the heat exchanger. The mother pipe diameters are set in sections in the first collector field and the second collector field to achieve self-balancing of the flow in the pipeline, reduce the use of valves, and reduce the construction investment cost of the solar thermal power station. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 FIG. 4 is a structural diagram of a solar power generation system according to an embodiment of the present invention.

[0031] Among them, 1-precooler, 2-main compressor, 3-low temperature regenerator, 301-low temperature regenerator shell side, 302-low temperature regenerator tube side, 4-recompressor, 5-high temperature regenerator, 501-high temperature regenerator shell side, 502-high temperature regenerator tube side, 6-first valve, 7-first collector field, 701-first mother pipe, 702-first collector loop, 703-second mother pipe, 8-preheater, 801-preheater shell side, 802-preheater tube side, 9-heat exchanger, 901-heat exchanger shell side, 902-heat exchanger tube side, 10-high-pressure turbine, 11-reheater, 1101-reheater shell side, 1102-reheater tube side, 12-third valve, 13-low-pressure turbine, 14-generator, 15-cold molten salt tank, 16-cold molten salt pump, 17-second solar collector field, 1701-cold molten salt mother pipe, 1702-second solar collector loop, 1703-hot molten salt mother pipe, 18-hot molten salt tank, 19-hot molten salt pump, 20-second valve. DETAILED DESCRIPTION

[0032] like Figure 1 As shown, a solar power generation system according to an embodiment of the present invention includes a supercritical carbon dioxide circulation loop and a second collector field 17; the supercritical carbon dioxide circulation loop includes a precooler 1, a main compressor 2, a low-temperature regenerator 3, a recompressor 4, a high-temperature regenerator 5, a heat exchanger 9, a high-pressure turbine 10, a reheater 11, a low-pressure turbine 13, a generator 10, a first collector field 7 and a preheater 8.

[0033] The output end of the high temperature regenerator tube side 502 is connected to the input end of the low temperature regenerator tube side 302, and the output end of the low temperature regenerator tube side 302 is respectively connected to the input end of the precooler 1 and the recompressor 4; the output end of the precooler 1 is connected to the input end of the main compressor 2; the output end of the main compressor 2 is connected to the input end of the low temperature regenerator shell side 301, and the output end of the low temperature regenerator shell side 301 is connected to the output end of the recompressor 4 and then connected to the input end of the high temperature regenerator shell side 501. The generator 10 and the low pressure turbine 13 are coaxially connected to the high pressure turbine 10, the output end of the reheater 11 tube side is connected to the input end of the low pressure turbine 13, and the output end of the heat exchanger 9 tube side is connected to the input end of the high pressure turbine 10.

[0034] The output end of the high-temperature reheater shell side 501 is respectively connected to the input end of the first collector field 7 and the input end of the preheater tube side 802; the output end of the first collector field 7 is connected to the output end of the preheater tube side 802 and then connected to the input end of the heat exchanger tube side 902; the output end of the heat exchanger tube side 902 is connected to the input end of the high-pressure turbine 10, and the output end of the high-pressure turbine 10 is respectively connected to the input end of the preheater shell side 801 and the input end of the reheater tube side 1102; the output end of the preheater shell side 801 is connected to the input end of the high-temperature reheater tube side 502.

[0035] The first heat collecting field 7 includes a first mother pipe 701, a second mother pipe 703 and n1 first heat collecting loops 702. The first mother pipe 701 and the second mother pipe 703 are arranged in the same way. The n1 first heat collecting loops 702 are arranged in parallel between the first mother pipe 701 and the second mother pipe 703. The first mother pipe 701 or the second mother pipe 703 each includes j pipe sections, where j=1, 2, ..., n1-1.

[0036] The inner diameter of the jth tube section of the first mother tube 701 is D c1,j , and its calculation formula is: m1 is the total flow rate of supercritical carbon dioxide flowing in the first collector field 7, D1 is the maximum diameter of the first mother pipe 701 and the second mother pipe 703, M c1,j is the supercritical carbon dioxide flow rate of the jth pipe section of the first mother pipe 701. The inner diameter value of the jth pipe section of the second mother pipe 703 is D h1,j , and its calculation formula is λ1 is the drag loss coefficient of supercritical carbon dioxide along the way, w1 is the length of each section of the first mother pipe 701 or the second mother pipe 703, ρ c1 is the density of supercritical carbon dioxide in the first mother tube 701; ξc1,j is the local resistance loss coefficient at the tee of the first mother pipe 701, ρ h1 is the density of supercritical carbon dioxide in the second mother tube 703; ξ h1,j is the local resistance loss coefficient at the tee of the second mother pipe 703, M h1,j is the supercritical carbon dioxide flow rate of the jth pipe section of the second mother pipe 703.

[0037] The density and specific heat capacity of carbon dioxide at different temperatures are obtained by querying the NIST database.

[0038] The supercritical carbon dioxide flow rate M of the jth pipe section of the first mother pipe 701 c1,j The calculation formula is M c1,j =M c1,j-1 -m 1,j ;m 1,j is the actual supercritical carbon dioxide mass flow rate in the first heat collection loop 702 of the jth item, M c1,0 =m1. The supercritical carbon dioxide flow rate M of the jth pipe section of the second mother pipe 703 h1,j The calculation formula is M h1,j =M h1,j-1 +m 1,j , M h1,0 =0.

[0039] The local resistance loss coefficient ξ at the tee of the first mother pipe 701 c1,j The local resistance loss coefficient ξ at the tee of the second mother pipe 703 h1,j The value is 20λ1, using the Aritsuari method Calculate the resistance loss coefficient λ1 of supercritical carbon dioxide along the way, K1 is the roughness of the pipeline; d1 is the inner diameter of the first heat collection loop pipe; Re1 is the first Reynolds number.

[0040] Obtain the actual mass flow rate of carbon dioxide in each first collector loop pipe The method, k1=1,2…,n1, comprises the following steps:

[0041] S101, obtain the actual mass flow rate m of carbon dioxide in the first heat collection loop pipe 1,1 ;

[0042] Since the inlet static pressure of the first solar collector field is set to p1, that is, the static pressure at the cold end of the first solar collector loop is p1, the outlet static pressure of the first solar collector loop is assigned a value of 0.001, and the static pressure difference between the cold and hot ends of the first solar collector loop is calculated according to formula (1); the actual mass flow rate of carbon dioxide in the first solar collector loop pipe is calculated according to formula (2).

[0043]

[0044] is the static pressure difference between the hot and cold ends of the first heat collection circuit in Article k1, is the static pressure at the cold end of the k1th collector circuit, is the static pressure at the hot end of the first heat collection circuit in Article k1.

[0045]

[0046] is the local resistance loss coefficient at the tee of the first heat collection loop pipe in the k1th row, and the value in this embodiment is 20λ1.

[0047] S102, obtaining the actual mass flow rate of carbon dioxide in the second to n1th heat collection loop pipes;

[0048] The carbon dioxide flow rate M in the jth pipe section of the first mother pipe c1，j The calculation method of is shown in formula (3), the carbon dioxide flow rate M in the jth pipe section of the second main pipe h1，j The calculation method of is shown in formula (14).

[0049] M c1，j =M c1，j-1 -m 1，j (3)

[0050] M h1，j =M h1，j-1 +m 1，j (4)

[0051] Since the carbon dioxide in the first pipe section of the second mother pipe comes from the first first collector loop, the carbon dioxide flow rate of the first pipe section of the first wooden pipe is equal to the actual carbon dioxide flow rate of the first collector loop, and equation (5) is obtained. Based on equation (6), the molten salt flow rate M of the first pipe section of the first mother pipe is calculated: c1，1 .

[0052] M h1，1 =m 1，1 (5)

[0053] M c，1 =m1-m 1，1 (6)

[0054] The obtained carbon dioxide flow rate M of the first section of the first main pipe c1，1 and the carbon dioxide flow rate M of the first section of the second main pipe h1，1 Substituting into equations (7) and (8) respectively, we can obtain the molten salt pressure drop ΔP of the cold molten salt main pipe in the first pipe section: c1，1 And the molten salt pressure drop of the first section of the hot molten salt main pipe ΔP h1，1 .

[0055]

[0056]

[0057] The inlet static pressure of the first collector field is p, that is, the cold end static pressure of the first collector loop is P c1，1 =p, the outlet static pressure of the first collector circuit P h1，1 Assigning a value of 0.001, the static pressure P at the cold end of the second collector circuit can be obtained according to equations (9) and (10) respectively: c1，2 and hot end static pressure P h1，2 .

[0058] P c1，j+1 =P c1，j -ΔP c1，j (9)

[0059] P h1，j+1 =P h1，j -ΔP h1，j (10)

[0060] Based on formula (1), the static pressure difference ΔP between the cold and hot ends of the second collector circuit is obtained: 12 , and based on formula (2) obtain the actual mass flow rate m of carbon dioxide in the second collector loop 12 .

[0061] Using the same method, based on equations (3), (4), (7) to (10), the static pressure P at the cold end of the j+1th collector circuit is obtained: c1,j+1 and hot end static pressure P h1,j+1 .

[0062] Based on formula (1), the static pressure difference ΔP between the cold and hot ends of the j+1th collector circuit is obtained: 1,j+1 , and based on formula (2), the actual mass flow rate m of carbon dioxide in the j+1th collector loop is obtained 1,j+1 .

[0063] At this point, the actual mass flow of carbon dioxide in each of the first heat collection loops 702 and the mass flow of carbon dioxide in each pipe section of the first mother pipe and the second mother pipe are obtained, and then the pipe diameter value of each pipe section of the first mother pipe and the second mother pipe is calculated.

[0064] like Figure 1As shown, the supercritical carbon dioxide circulation loop also includes a first valve 6, a second valve 20 and a third valve 12. The first valve 6 is arranged at the input end of the first collector field, and can control the opening and closing of the first collector field 7. The second valve 20 is arranged at the input end of the preheater tube side 802; the third valve 12 is arranged at the input end of the preheater shell side 801, and can control the opening and closing of the preheater 8.

[0065] The second heat collection field includes a cold molten salt pump 16, a cold molten salt tank 15, a cold molten salt mother pipe 1701, a hot molten salt pump 19, a hot molten salt tank 18, a hot molten salt mother pipe 1703 and n2 second heat collection loops 1702. The outlet of the hot molten salt mother pipe 1703 is connected to the hot molten salt pump 19 and the hot molten salt tank respectively; the output end of the hot molten salt pump is connected to the input end of the heat exchanger shell side 901 and the input end of the reheater shell side 1101 respectively, and the output end of the heat exchanger shell side 901 is connected to the output end of the reheater shell side 1101 and then connected to the cold molten salt tank; the cold molten salt tank 15 is connected to the inlet of the cold molten salt mother pipe 1703 via the cold molten salt pump 16.

[0066] The cold molten salt mother pipe 1701 and the hot molten salt mother pipe 1703 are arranged in the same route; n2 second heat collecting loops 1702 are arranged in parallel between the cold molten salt mother pipe 1701 and the hot molten salt mother pipe 1703. The cold molten salt mother pipe 1701 includes i pipe sections, i = 1, 2, ..., n2-1. The inner diameter value of the i-th pipe section of the cold molten salt mother pipe is D c2,i , and its calculation formula is: m2 is the total flow rate of molten salt flowing in the collector field, D2 is the maximum diameter of the mother pipe, M c2,i is the molten salt flow rate of the i-th section of the cold molten salt main pipe.

[0067] The diameters of the cold molten salt main pipe and the hot molten salt main pipe branch sections are set so that the molten salt flow in each of the second heat collection loops is balanced to achieve uniform heating, and a higher temperature is ensured when the molten salt flows into the shell side of the heat exchanger.

[0068] The inner diameter of the ith section of the molten salt main pipe is D h2,i , and its calculation formula is λ2 is the resistance loss coefficient of binary molten salt along the way, ρ c2 is the density of cold molten salt; w2 is the length of each section of cold / hot molten salt mother pipe, ξ c2,i is the local resistance loss coefficient at the tee of the cold molten salt mother pipe, ρ h2 is the density of molten salt; h2，i is the local resistance loss coefficient at the tee of the hot molten salt mother pipe, M h2，i is the molten salt flow rate of the i-th section of the hot molten salt mother pipe.

[0069] The heat transfer medium flowing in the second collector field is binary molten salt, and the component structure of the binary molten salt is: 60wt% NaNO3+40wt% KNO3, and the relationship between its physical properties and temperature is as follows:

[0070] ρ m =2085.5-0.6258t m (11)

[0071] λ m =0.4407+1.926×10 -4 t m (12)

[0072] C p，m =1442.3+0.1735t m (13)

[0073]

[0074] in,

[0075] ρ m ——Density of binary molten salt, kg / m 3

[0076] λ m ——Thermal conductivity of binary molten salt, W / m / K

[0077] C p，m ——Specific heat capacity of binary molten salt, J / kg / K

[0078] μ——dynamic viscosity of binary molten salt, Pa·s

[0079] t m ——Temperature, °C

[0080] By knowing the inlet temperature of the cold molten salt main pipe, the physical properties of the cold molten salt can be calculated. By knowing the outlet temperature of the hot molten salt main pipe, the physical properties of the hot molten salt can be calculated.

[0081] Molten salt flow rate M of the i-th section of the cold molten salt main pipe c2，i The calculation formula is M c2，i =M c2，i-1 -m 2，i ;m 2，i is the actual molten salt mass flow rate in the second collector loop of the i-th article, M c2，0 = m2; molten salt flow rate M of the ith section of the hot molten salt main pipe h2，i The calculation formula is M h2，i =M h2，i-1 +m 2，i , M h2，0 =0.

[0082] Local resistance loss coefficient ξ at the tee of cold molten salt main pipe c2，i Local resistance loss coefficient ξ at the tee of the hot molten salt main pipe h2，i The value is 20λ2, using the Aritsuari method Calculate the resistance loss coefficient λ2 of the binary molten salt along the way, K2 is the roughness of the pipeline; d2 is the inner diameter of the second heat collection loop pipe; Re2 is the second Reynolds number.

[0083] The actual molten salt mass flow rate in each of the second collector loops The method for obtaining the actual mass flow rate of carbon dioxide in each first heat collecting loop pipe is as follows: The method is consistent.

[0084] After obtaining the actual mass flow rate of the molten salt in each of the second heat collection loops and the mass flow rate of the molten salt in each pipe section of the cold molten salt mother pipe and the hot molten salt mother pipe, the pipe diameter value of each pipe section of the cold molten salt mother pipe and the hot molten salt mother pipe is calculated.

[0085] A power generation method of a solar power generation system according to an embodiment of the present invention includes:

[0086] When there is sufficient sunlight, the first valve 6 is opened, and the second valve 20 and the third valve 12 are closed. The first solar collector 7 is in operation, the preheater 8 is not in operation, and the carbon dioxide is heated by the first solar collector 7.

[0087] The carbon dioxide working medium flows out from the low-temperature regenerator tube side 302 and is divided. A part of it is cooled and reduced in temperature by the precooler 1, and then compressed and increased in pressure by the main compressor 2, and then flows into the low-temperature regenerator shell side 301 to absorb heat and increase in temperature; the other part is compressed and increased in pressure by the recompressor 4, and then merges with the carbon dioxide at the output end of the low-temperature regenerator shell side 301 and flows into the shell side of the high-temperature regenerator 501 to absorb heat and increase in temperature, and then flows into the first collector field 7 for preheating and temperature increase, and then flows into the heat exchanger tube side 902. At this time, the heat exchanger shell side 901 is heated by the second The hot molten salt heated by the solar collector 17 flows through, and the high temperature of the molten salt can indirectly further heat the carbon dioxide on the tube side 902 of the heat exchanger. The further heated carbon dioxide enters the high-pressure turbine 10 to expand and do work, and then is exhausted to the reheater through the high-pressure turbine 10. After the reheater 11 reheats the carbon dioxide, the carbon dioxide enters the low-pressure turbine 13 to do work, and then drives the generator 14 to generate electricity. The carbon dioxide working fluid after doing work flows into the high-temperature regenerator tube side 502 and the low-temperature regenerator tube side 302 in turn to release heat and reduce temperature, and enters the next cycle.

[0088] When the sunlight is insufficient, the first valve 6 is closed, and the second valve 20 and the third valve 12 are opened. The first solar field 7 does not work, and the preheater 8 works, and the carbon dioxide is heated by the preheater 8.

[0089] The carbon dioxide working medium flows out from the low-temperature regenerator tube side 302 and is divided. A part of it is cooled and reduced in temperature by the precooler 1, and then compressed and increased in pressure by the main compressor 2, and then flows into the low-temperature regenerator shell side 301 to absorb heat and increase in temperature; the other part is compressed and increased in pressure by the recompressor 4, and then merges with the carbon dioxide at the output end of the low-temperature regenerator shell side 301 and flows into the high-temperature regenerator shell side 501 to absorb heat and increase in temperature, and then flows into the preheater 8 for preheating and increasing in temperature, and then flows into the heat exchanger tube side 902. At this time, the heat exchanger shell side 901 is compressed by the first The hot molten salt heated by the second collector field flows through, and the high temperature of the molten salt can indirectly further heat the carbon dioxide on the heat exchanger tube side 902. The further heated carbon dioxide enters the high-pressure turbine 10 to expand and do work, and then is exhausted to the reheater 11 through the high-pressure turbine 10. After the reheater reheats the carbon dioxide, the carbon dioxide enters the low-pressure turbine 13 to do work, and then drives the generator 14 to generate electricity. The carbon dioxide working fluid after doing work flows into the high-temperature reheater tube side 502 and the low-temperature reheater tube side 302 in turn to release heat and reduce temperature, and then enters the next cycle.

Claims

1. A solar power generation system, comprising a supercritical carbon dioxide circulation loop and a second collector field; the supercritical carbon dioxide circulation loop comprises a precooler, a main compressor, a low-temperature regenerator, a recompressor, a high-temperature regenerator, a heat exchanger, a high-pressure turbine, a reheater, a low-pressure turbine and a generator; The output end of the high-temperature regenerator tube side is connected to the input end of the low-temperature regenerator tube side, and the output end of the low-temperature regenerator tube side is respectively connected to the input ends of the precooler and the recompressor; the output end of the precooler is connected to the input end of the main compressor; the output end of the main compressor is connected to the input end of the low-temperature regenerator shell side, and the output end of the low-temperature regenerator shell side is connected to the output end of the recompressor and then connected to the input end of the high-temperature regenerator shell side; The generator, the low-pressure turbine and the high-pressure turbine are coaxially connected; The output end of the reheater tube side is connected to the input end of the low-pressure turbine, and the output end of the heat exchanger tube side is connected to the input end of the high-pressure turbine; Features: The supercritical carbon dioxide circulation loop also includes a first heat collecting field and a preheater; the output end of the high-temperature regenerator shell side is respectively connected to the input end of the first heat collecting field and the input end of the preheater tube side; the output end of the first heat collecting field is connected to the output end of the preheater tube side and then connected to the input end of the heat exchanger tube side; the output end of the heat exchanger tube side is connected to the input end of the high-pressure turbine, and the output end of the high-pressure turbine is respectively connected to the input end of the preheater shell side and the input end of the reheater tube side; the output end of the preheater shell side is connected to the input end of the high-temperature regenerator tube side; The first heat collection field comprises a first mother pipe, a second mother pipe and n1 first heat collection loops, the first mother pipe and the second mother pipe are arranged in the same route; the n1 first heat collection loops are arranged in parallel between the first mother pipe and the second mother pipe; the first mother pipe or the second mother pipe each comprises j pipe sections, j=1, 2, ..., n1-1; The inner diameter of the jth pipe section of the first mother pipe is D c1,j , and its calculation formula is: m1 is the total flow rate of supercritical carbon dioxide flowing in the first collector field, D1 is the maximum diameter of the first mother pipe and the second mother pipe, M c1,j is the supercritical carbon dioxide flow rate of the j-th pipe section of the first mother pipe; The inner diameter of the jth pipe section of the second mother pipe is D h1,j , and its calculation formula is λ1 is the resistance loss coefficient of supercritical carbon dioxide along the way, w1 is the length of each section of the first mother pipe or the second mother pipe, ρ c1 is the density of supercritical carbon dioxide in the first mother tube; ξ c1,j is the local resistance loss coefficient at the first mother pipe tee, ρ h1 is the density of supercritical carbon dioxide in the second mother tube; ξ h1,j is the local resistance loss coefficient at the second mother pipe tee, M h1,j is the supercritical carbon dioxide flow rate of the j-th pipe section of the second mother pipe.

2. The solar power generation system according to claim 1, characterized in that: The supercritical carbon dioxide flow rate M of the jth pipe section of the first mother pipe c1,j The calculation formula is M c1,j =M c1,j-1 -m 1,j ;m 1,j is the actual supercritical carbon dioxide mass flow rate in the first collector loop of the jth article, M c1,0 =m1; supercritical carbon dioxide flow rate M of the jth section of the second mother pipe h1,j The calculation formula is M h1,j =M h1,j-1 +m 1,j , M h1,0 =0.

3. The solar power generation system according to claim 1, characterized in that: The local resistance loss coefficient ξ at the tee of the first mother pipe c1,j The local resistance loss coefficient ξ at the second mother pipe tee h1,j The value is 20λ1. K1 is the roughness of the pipeline; d1 is the inner diameter of the first heat collection loop pipe; Re1 is the first Reynolds number.

4. The solar power generation system according to any one of claims 1 to 3, characterized in that: It also includes a first valve, a second valve and a third valve. The first valve is arranged at the input end of the first collector field; the second valve is arranged at the input end of the preheater tube side; and the third valve is arranged at the input end of the preheater shell side.

5. The solar power generation system according to claim 4, characterized in that: The second solar collector field includes a cold molten salt pump, a cold molten salt tank, a cold molten salt mother pipe, a hot molten salt pump, a hot molten salt tank, a hot molten salt mother pipe and n2 second solar collector loops; The outlet of the hot molten salt mother pipe is respectively connected to the hot molten salt pump and the hot molten salt tank; the output end of the hot molten salt pump is respectively connected to the input end of the heat exchanger shell side and the input end of the reheater shell side, and the output end of the heat exchanger shell side is connected to the output end of the reheater shell side and then connected to the cold molten salt tank; the cold molten salt tank is connected to the inlet of the cold molten salt mother pipe via the cold molten salt pump; The cold molten salt mother pipe and the hot molten salt mother pipe are arranged in the same route; n2 second heat collection loops are arranged in parallel between the cold molten salt mother pipe and the hot molten salt mother pipe; The cold molten salt mother pipe includes i pipe sections, i=1, 2, ..., n2-1; The inner diameter of the i-th section of the cold molten salt mother pipe is D c2,i , and its calculation formula is: m2 is the total flow rate of molten salt flowing in the collector field, D2 is the maximum diameter of the mother pipe, M c2,i is the molten salt flow rate of the i-th section of the cold molten salt main pipe; The inner diameter of the ith section of the molten salt main pipe is D h2,i , and its calculation formula is λ2 is the resistance loss coefficient of binary molten salt along the way, ρ c2 is the density of cold molten salt; w2 is the length of each section of cold / hot molten salt mother pipe, ξ c2,i is the local resistance loss coefficient at the tee of the cold molten salt mother pipe, ρ h2 is the density of molten salt; h2,i is the local resistance loss coefficient at the tee of the hot molten salt mother pipe, M h2,i is the molten salt flow rate of the i-th section of the hot molten salt mother pipe.

6. The solar power generation system according to claim 5, characterized in that: Molten salt flow rate M of the i-th section of the cold molten salt main pipe c2,i The calculation formula is M c2,i =M c2,i-1 -m 2,i ;m 2,i is the actual molten salt mass flow rate in the second collector loop of the i-th article, M c2,0 = m2; molten salt flow rate M of the ith section of the hot molten salt main pipe h2,i The calculation formula is M h2,i =M h2,i-1 +m 2,i , M h2,0 =0.

7. The solar power generation system according to claim 5, characterized in that: Local resistance loss coefficient ξ at the tee of cold molten salt main pipe c2,i Local resistance loss coefficient ξ at the tee of the hot molten salt main pipe h2,i The value is 20λ2. K2 is the roughness of the pipeline; d2 is the inner diameter of the second heat collection loop pipe; Re2 is the second Reynolds number.

8. The power generation method of the solar power generation system according to any one of claims 4 to 7, characterized in that: When there is sufficient sunlight, the first valve is opened, and the second valve and the third valve are closed; When the sunlight is insufficient, the first valve is closed, and the second valve and the third valve are opened.

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