Fused salt energy storage system and method suitable for rapid peak and frequency regulation

Abstract

The invention discloses a fused salt energy storage system suitable for rapid peak and frequency modulation, which comprises a high-level cold salt tank and a low-level hot salt tank, and further comprises a management and control device, the high-level cold salt tank and the low-level hot salt tank have a first preset height difference therebetween, and the high-level cold salt tank and the low-level hot salt tank have a second preset height difference therebetween. The controller is used for starting the low-temperature tank pump according to a power grid peak regulation and frequency modulation instruction so as to quickly lift the fused salt and enter the high-position cold salt tank, opening the first valve and starting the fused salt electric heater, so that the fused salt in the high-position cold salt tank flows to the low-position hot salt tank through the fused salt electric heater under the action of gravity; the power of the fused salt electric heater is gradually increased to heat the fused salt, meanwhile, the power of the low-temperature tank pump is controlled to be reduced to enable the sum of the two powers to be matched with a power grid peak regulation and frequency modulation instruction, and finally the low-temperature tank pump is closed to achieve transition to a frequency regulation and peak regulation main mode of the fused salt electric heater. Therefore, rapid peak and frequency regulation response of the fused salt energy storage system can be realized on the basis of low cost, safety and high efficiency. The invention further discloses a fused salt energy storage method suitable for rapid peak and frequency regulation.

Description

Technical Field

[0001] The present invention belongs to the technical field of molten salt energy storage equipment, and in particular relates to a molten salt energy storage system and method suitable for rapid peak load regulation and frequency modulation. Background Art

[0002] With the continuous advancement of the construction of new power systems, the proportion of renewable energy in the current power system is increasing. Therefore, the power grid system has an increasingly strong demand for auxiliary services such as peak-shaving and frequency regulation. In the future, with the gradual withdrawal of thermal power, this contradiction will become more and more acute. Therefore, seeking efficient and low-cost flexible resources is the trend of future development.

[0003] In the existing technology, molten salt energy storage is a flexible regulation method with the prospect of large-scale development. However, due to the physical property of easy solidification, molten salt requires heat preservation and heating, and the startup speed is slow, which makes it difficult to meet the needs of new power systems for rapid response to peak and frequency regulation. One solution in the existing technology is to use molten salt + electrochemical battery to combine peak and frequency regulation. However, due to the huge difference in energy storage principles between molten salt energy storage and electrochemical energy storage, there are inevitably some barriers between the two to be coupled, and the construction of two completely independent systems also has the problem of high cost. In addition, electrochemical energy storage has great safety hazards, making it difficult to apply this coupling system to scenarios with high safety requirements.

[0004] In summary, how to achieve rapid peak-shaving and frequency-regulating response of molten salt energy storage systems on the basis of low cost, safety and high efficiency is an urgent problem to be solved. Summary of the invention

[0005] To solve the above problems, the present invention provides a molten salt energy storage system and method suitable for rapid peak-shaving and frequency regulation, which can achieve rapid peak-shaving and frequency regulation response of the molten salt energy storage system on the basis of low cost, safety and high efficiency, so that the molten salt energy storage system can be fully integrated into the power grid system to participate in peak-shaving and frequency regulation services.

[0006] The present invention provides a molten salt energy storage system suitable for rapid peak-shaving and frequency regulation, comprising a high-level cold salt tank connected by a low-temperature tank pump and a low-level hot salt tank connected by a high-temperature tank pump arranged on a molten salt pipeline, wherein the high-level cold salt tank is connected to the molten salt inlet end of the molten salt electric heater by a first valve, and the low-level hot salt tank is connected to the molten salt outlet end of the molten salt electric heater, and there is a first preset height difference between the high-level cold salt tank and the low-level hot salt tank, and also includes a control device, which is used to start the control device according to the peak-shaving and frequency regulation instructions of the power grid. The low-temperature tank pump quickly raises the molten salt and enters the high-level cold salt tank, quickly converts electrical energy into gravitational potential energy, opens the first valve, and starts the molten salt electric heater, so that the molten salt in the high-level cold salt tank flows to the low-level hot salt tank through the molten salt electric heater under the action of gravity, gradually increases the power of the molten salt electric heater, and controls the reduction of the power of the low-temperature tank pump so that the sum of the two powers matches the peak-shaving and frequency-regulating instructions of the power grid, and finally shuts down the low-temperature tank pump to realize the transition to the main mode of frequency-regulating and peak-shaving of the molten salt electric heater.

[0007] Preferably, in the above-mentioned molten salt energy storage system suitable for rapid peak shaving and frequency regulation, it also includes a low-level cold salt tank arranged on the molten salt pipeline and connected to the high-level cold salt tank by the low-temperature tank pump, and a high-level hot salt tank connected to the low-level hot salt tank by the high-temperature tank pump, there is a second preset height difference between the high-level hot salt tank and the low-level cold salt tank, and the low-temperature tank pump is used to pump the molten salt from the low-level cold salt tank to the high-level cold salt tank, and the high-temperature tank pump is used to pump the molten salt from the low-level hot salt tank to the high-level hot salt tank.

[0008] Preferably, the above-mentioned molten salt energy storage system suitable for rapid peak and frequency regulation also includes a molten salt-steam heat exchanger arranged on the molten salt pipeline, the molten salt-steam heat exchanger is connected to the power grid by means of a steam turbine power generation equipment, and the molten salt-steam heat exchanger is arranged between the high-level hot salt tank and the low-level cold salt tank, and a second valve is provided between it and the high-level hot salt tank, the molten salt-steam heat exchanger is used to convert the high-temperature molten salt from the high-level hot salt tank into steam for the steam turbine power generation equipment to generate electricity and to send the low-temperature molten salt obtained after cooling into the low-level cold salt tank.

[0009] Preferably, the above-mentioned molten salt energy storage system suitable for rapid peak load regulation and frequency modulation further includes a first circulation pump connected in parallel with the first valve, and a second circulation pump connected in parallel with the second valve.

[0010] Preferably, in the above-mentioned molten salt energy storage system suitable for rapid peak and frequency regulation, a third valve is also arranged between the high-temperature tank pump and the low-level hot salt tank, a fourth valve is also arranged between the low-temperature tank pump and the low-level cold salt tank, and a fifth valve is also arranged between the molten salt-steam heat exchanger and the steam turbine power generation equipment.

[0011] Preferably, in the above-mentioned molten salt energy storage system suitable for rapid peak load regulation and frequency modulation, the molten salt-steam heat exchanger is also provided with a steam output pipeline, and a temperature and pressure reducing valve is also provided on the steam output pipeline.

[0012] Preferably, in the above-mentioned molten salt energy storage system suitable for rapid peak shaving and frequency regulation, it also includes a liquid level gauge arranged on the low-level cold salt tank, and the liquid level gauge is electrically connected to the control device to transmit the liquid level information of the low-level cold salt tank to the control device in real time, and the control device is used to start the high temperature tank pump to match the peak shaving and frequency regulation instructions of the power grid when the liquid level of the low-level cold salt tank is too low.

[0013] Preferably, in the above-mentioned molten salt energy storage system suitable for rapid peak load regulation and frequency modulation, the high-position hot salt tank and the low-position hot salt tank are integral hot salt tanks with a gap in the middle, and the high-temperature tank pump is arranged at the bottom of the integral hot salt tank, and the molten salt pipeline connecting the high-position hot salt tank and the low-position hot salt tank is located inside the integral hot salt tank;

[0014] The high-position cold salt tank and the low-position cold salt tank are integral cold salt tanks with a gap in the middle, and the low-temperature tank pump is arranged at the bottom of the integral cold salt tank, and the molten salt pipeline connecting the high-position cold salt tank and the low-position cold salt tank is located inside the integral cold salt tank.

[0015] Preferably, in the above-mentioned molten salt energy storage system suitable for rapid peak and frequency regulation, it also includes a heating device arranged on the outer periphery of the molten salt pipeline, the control device is electrically connected to the heating device, and the control device is used to start the heating device at the same time as starting the low-temperature tank pump.

[0016] The present invention provides a molten salt energy storage method suitable for rapid peak-shaving and frequency modulation, using the molten salt energy storage system suitable for rapid peak-shaving and frequency modulation as described in any one of the above items, comprising:

[0017] Receive power grid peak and frequency regulation instructions;

[0018] Starting the cryogenic tank pump to quickly raise the molten salt and put it into the high-position cold salt tank, and quickly converting the electrical energy into gravitational potential energy;

[0019] Open the first valve and start the molten salt electric heater, so that the molten salt in the high-position cold salt tank flows to the low-position hot salt tank through the molten salt electric heater under the action of gravity;

[0020] While gradually increasing the power of the molten salt electric heater, controlling to reduce the power of the cryogenic tank pump, so that the sum of the two powers matches the peak load and frequency regulation instruction of the power grid;

[0021] The cryogenic tank pump is turned off, and only the molten salt electric heater is kept on, so as to realize the transition to the main mode of frequency and peak regulation of the molten salt electric heater.

[0022] From the above description, it can be seen that in the molten salt energy storage system suitable for rapid peak and frequency regulation provided by the present invention, since there is a first preset height difference between the high-level cold salt tank and the low-level hot salt tank, the control device is used to start the low-temperature tank pump according to the peak and frequency regulation instructions of the power grid to quickly raise the molten salt and enter the high-level cold salt tank, and quickly convert the electrical energy into gravitational potential energy, and open the first valve, start the molten salt electric heater, so that the molten salt in the high-level cold salt tank flows to the low-level hot salt tank through the molten salt electric heater under the action of gravity, gradually increase the power of the molten salt electric heater, and control the reduction of the power of the low-temperature tank pump so that the sum of the two powers matches the peak and frequency regulation instructions of the power grid, and finally turn off the low-temperature tank pump to achieve the transition to the main mode of frequency and peak regulation of the molten salt electric heater. It can be seen that the system can use the low-temperature tank pump to raise the molten salt to quickly convert electrical energy into gravitational potential energy for energy when receiving the frequency and peak regulation instructions. Storage, this low-temperature tank pump has the performance of rapid response, so it can better meet the rapid response requirements for peak-shaving and frequency modulation compared to the main mode of molten salt electric heating that requires preheating, but this electric energy stored by gravitational potential energy is limited and can only play a transitional role. Therefore, when the preheating is gradually completed, the power of the low-temperature tank pump can be gradually reduced, and the power of the molten salt electric heater can be gradually increased to achieve the transition between the two peak-shaving and frequency modulation modes. In this peak-shaving and frequency modulation process, it can always be ensured that the sum of the powers of the two is equal to the power value in the peak-shaving and frequency modulation instruction, and because the cold salt falls into the molten salt electric heater under the action of gravity to achieve heating, gravity can be used to overcome part of the flow resistance, and the flow is faster and smoother. It can be seen that the system can realize the rapid peak-shaving and frequency modulation response of the molten salt energy storage system on the basis of low cost, safety and efficiency, so that the molten salt energy storage system can be fully integrated into the power grid system to participate in peak-shaving and frequency modulation services. The above-mentioned molten salt energy storage method suitable for rapid peak-shaving and frequency modulation provided by the present invention has the same advantages as the above-mentioned system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0024] Figure 1 A schematic diagram of the composition of an embodiment of a molten salt energy storage system suitable for rapid peak load regulation and frequency modulation provided by the present invention;

[0025] Figure 2 A schematic diagram of an embodiment of a molten salt energy storage method suitable for rapid peak and frequency regulation provided by the present invention. DETAILED DESCRIPTION

[0026] The core of the present invention is to provide a molten salt energy storage system and method suitable for rapid peak-shaving and frequency regulation, which can achieve rapid peak-shaving and frequency regulation response of the molten salt energy storage system on the basis of low cost, safety and high efficiency, so that the molten salt energy storage system can be fully integrated into the power grid system to participate in peak-shaving and frequency regulation services.

[0027] 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.

[0028] An implementation example of a molten salt energy storage system suitable for rapid peak and frequency regulation provided by the present invention is as follows: Figure 1 As shown, Figure 1 A schematic diagram of the composition of an embodiment of a molten salt energy storage system suitable for rapid peak-shaving and frequency regulation provided by the present invention, the system may include a high-level cold salt tank G4 connected to a low-temperature tank pump B2 and a low-level hot salt tank G1 connected to a high-temperature tank pump B1, both the high-temperature tank pump and the low-temperature tank pump here use pumps with rapid frequency conversion functions, which consume electrical energy as variable loads, so as to achieve rapid response to peak-shaving and frequency regulation instructions of the power grid, the high-level cold salt tank G4 is connected to the molten salt inlet end of the molten salt electric heater 1 by a first valve F4, and the low-level hot salt tank G1 is connected to the molten salt inlet end of the molten salt electric heater 1 by a first valve F4. At the outlet end, there is a first preset height difference between the high-position cold salt tank G4 and the low-position hot salt tank G1, and the low-position hot salt tank G1 can be buried in the soil. The first preset height difference can be between 2 meters and 10 meters, which can be selected according to actual needs. In this case, after opening the first valve F4, the high-position cold salt tank G4, the molten salt electric heater 1 and the low-position hot salt tank G1 can form a molten salt passage, and the molten salt flow rate can be adjusted by controlling the opening degree of the first valve F4. It also includes a control device 4, which is electrically connected to the high-temperature tank pump B1, the low-temperature tank pump B2, the molten salt electric heater 1 and the first valve F4 ( Figure 1These electrical connections are not shown), the control device 4 is used to start the low-temperature tank pump B2 according to the peak-shaving and frequency-regulating instructions of the power grid to quickly raise the molten salt and enter the high-level cold salt tank G4, and quickly convert the electrical energy into gravitational potential energy. When more electrical energy needs to be converted, the frequency of the low-temperature tank pump B2 is adjusted to a higher level to allow the molten salt to be transported to the high-level cold salt tank G4 more quickly, and vice versa. The first valve F4 is opened and the molten salt electric heater 1 is started, so that the molten salt in the high-level cold salt tank G4 flows to the low-level hot salt tank G1 through the molten salt electric heater 1 under the action of gravity. In the initial situation, this molten salt electric heater 1 cannot respond quickly, but requires a certain amount of preheating time to enter a normal state. Therefore, the initial state In this state, the above-mentioned low-temperature tank pump frequency modulation is needed to achieve assistance, and then gradually increase the power of the molten salt electric heater 1 while controlling the reduction of the power of the low-temperature tank pump B2 so that the sum of the two powers matches the grid peak-shaving and frequency modulation instructions, and finally shut down the low-temperature tank pump B2 to achieve the transition to the molten salt electric heater frequency modulation and peak-shaving main mode. It should be noted here that the low-temperature tank pump B2 cannot transport the molten salt to it indefinitely, because the molten salt is limited after all. Therefore, the role of the low-temperature tank pump B2 is only to respond quickly in the initial stage, and in the subsequent stages, it is no longer necessary to assist, and it is only necessary to use the molten salt electric heater for frequency modulation and peak regulation, because the subsequent preheating has been completed, and the molten salt electric heater can work normally.

[0029] It should be noted that in the initial startup stage of the above-mentioned system, the tank pump regulation mode is used as a transition mode, and then gradually transitions to the main mode of peak and frequency regulation of the molten salt electric heater, which overcomes the problem in the prior art that the molten salt needs to wait for heating when starting from static state, shortens the response time, and compared with the molten salt + electrochemical energy storage combined peak and frequency regulation mode, it has the advantages of simple structure, easy coupling, good safety, high reliability and low cost. Since the tank pump can quickly change the frequency of operation, the frequency regulation function can be realized more easily. During the main mode operation, it can also assist in operation to improve the comprehensive peak and frequency regulation effect of the system.

[0030] It can be seen from the above description that in the embodiment of the molten salt energy storage system suitable for rapid peak and frequency regulation provided by the present invention, since there is a first preset height difference between the high-level cold salt tank and the low-level hot salt tank, the control equipment is used to start the low-temperature tank pump according to the peak and frequency regulation instructions of the power grid to quickly raise the molten salt and enter the high-level cold salt tank, and quickly convert the electrical energy into gravitational potential energy, and open the first valve, start the molten salt electric heater, so that the molten salt in the high-level cold salt tank flows to the low-level hot salt tank through the molten salt electric heater under the action of gravity, gradually increase the power of the molten salt electric heater, and control the reduction of the power of the low-temperature tank pump so that the sum of the two powers matches the peak and frequency regulation instructions of the power grid, and finally turn off the low-temperature tank pump to achieve the transition to the main mode of frequency and peak regulation of the molten salt electric heater. It can be seen that the system can use the low-temperature tank pump to raise the molten salt when receiving the frequency and peak regulation instructions to quickly convert the electrical energy into gravitational potential energy for energy storage. This low-temperature tank pump has the characteristics of rapid The performance of rapid response is better than that of the main mode of molten salt electric heating that requires preheating. It can better meet the rapid response requirements for peak-shaving and frequency regulation. However, the electric energy stored by gravitational potential energy is limited and can only play a transitional role. Therefore, after the preheating is gradually completed, the power of the cryogenic tank pump can be gradually reduced, and the power of the molten salt electric heater can be gradually increased to achieve the transition between the two peak-shaving and frequency regulation modes. In this peak-shaving and frequency regulation process, the sum of the powers of the two can be ensured to be equal to the power value in the peak-shaving and frequency regulation instruction. Moreover, since the cold salt falls into the molten salt electric heater under the action of gravity to achieve heating, gravity can be used to overcome part of the flow resistance, so the flow is faster and smoother. It can be seen that the system can realize the rapid peak-shaving and frequency regulation response of the molten salt energy storage system on the basis of low cost, safety and efficiency, so that the molten salt energy storage system can be fully integrated into the power grid system to participate in peak-shaving and frequency regulation services.

[0031] Continue to refer Figure 1 In a specific embodiment of the above-mentioned molten salt energy storage system suitable for rapid peak-shaving and frequency regulation, on the basis of the above-mentioned embodiment, it also includes a low-level cold salt tank G3 arranged on the molten salt pipeline and connected to the high-level cold salt tank G4 by means of a low-temperature tank pump B2, and a high-level hot salt tank G2 connected to the low-level hot salt tank G1 by means of a high-temperature tank pump B1, and there is a second preset height difference between the high-level hot salt tank G2 and the low-level cold salt tank G3, and the second preset height difference can also be preferably 2 meters to 10 meters, and the low-temperature tank pump B2 is used to pump the molten salt from the low-level cold salt tank G3 to the high-level cold salt tank G4, and the high-temperature tank pump B1 is used to pump the molten salt from the low-level hot salt tank G1 to the high-level hot salt tank G2.

[0032] It should be noted that in this case, when the peak-shaving and frequency modulation are initially performed, if the liquid level in the low-level cold salt tank G3 is too low to continue to extract cold salt, the high-temperature tank pump B1 can be started to raise the hot salt in the low-level hot salt tank G1 and introduce it into the high-level hot salt tank G2, so that the electric energy on the high-temperature tank side is converted into gravitational potential energy and stored. Since the high-temperature tank pump B1 has the same advantage of fast frequency modulation response as the low-temperature tank pump B2, the two can cooperate with each other to achieve rapid peak-shaving and frequency modulation. At this time, the total power of the high-temperature tank pump B1, the low-temperature tank pump B2 and the molten salt electric heater 1 can be controlled to match the power parameters in the power grid instruction. It can be seen that this embodiment can form a certain redundancy mechanism to achieve more effective and rapid peak-shaving and frequency modulation, and can cope with more special situations.

[0033] Continue to refer Figure 1 In another specific embodiment of the molten salt energy storage system suitable for rapid peak load regulation and frequency regulation, based on the above specific embodiment, it can also include a molten salt-steam heat exchanger 2 arranged on the molten salt pipeline 3, the molten salt-steam heat exchanger 2 is connected to the power grid 8 by the steam turbine power generation equipment 5, and the molten salt-steam heat exchanger 2 is arranged between the high-level hot salt tank G2 and the low-level cold salt tank G3, and a second valve F2 is provided between it and the high-level hot salt tank G2, and the molten salt-steam heat exchanger 2 is used to convert the high-temperature molten salt from the high-level hot salt tank G2 into steam for power generation by the steam turbine power generation equipment 5 and to send the low-temperature molten salt obtained after cooling into the low-level cold salt tank G3.

[0034] In this case, when the power grid needs the molten salt system to provide electricity, the amount of molten salt entering the molten salt-steam heat exchanger 2 from the high-level hot salt tank G2 is immediately increased, and the generated steam passes through the steam turbine power generation equipment 5 to generate electricity and low-temperature steam. Because the system has a heating demand, the molten salt-steam heat exchanger 2 is generally in operation, and the generated steam is directly supplied to the user, that is, there is always molten salt flowing between the high-level cold salt tank G4 and the low-level hot salt tank G1, and the pipeline has no preheating link. However, if it is started from a static state, a period of heating is required. In summary, this embodiment can adjust the peak power generation output of the steam turbine power generation equipment through the heat exchange of the molten salt-steam heat exchanger, so that it can accurately respond to various adjustment instructions of the power grid and better maintain the balance of the power system.

[0035] Continue to refer Figure 1In another specific embodiment of the molten salt energy storage system suitable for rapid peak-shaving and frequency modulation, based on the above another specific embodiment, it can also include a first circulation pump B4 connected in parallel with the first valve F4, and a second circulation pump B3 connected in parallel with the second valve F2. It should be noted that in this case, in the process of peak-shaving and frequency modulation, gravity flow is preferentially used. When the flow rate requirement is not met, the corresponding circulation pump can be started to realize the rapid flow of molten salt, which can further improve the efficiency of peak-shaving and frequency modulation.

[0036] In further embodiments, continue to refer to Figure 1 , a third valve F1 may be provided between the high temperature tank pump B1 and the low position hot salt tank G1, a fourth valve F3 may be provided between the low temperature tank pump B2 and the low position cold salt tank G3, and a fifth valve F5 may be provided between the molten salt-steam heat exchanger 2 and the steam turbine power generation equipment 5. It should be noted that these valves can effectively control the flow of molten salt. When the molten salt needs to pass through, the corresponding valve can be opened, and the molten salt flow rate can be adjusted by controlling the opening size of the valve. These valves can be electrically connected to the above-mentioned control device 4 to accept its unified control, so as to realize overall automatic control.

[0037] In a further embodiment, continue to refer to Figure 1 The molten salt-steam heat exchanger 2 may also be provided with a steam output pipeline (as shown by the arrow printed on the right side thereof), and a temperature-reducing and pressure-reducing valve F- is also provided on the steam output pipeline. It should be noted that the temperature-reducing and pressure-reducing valve F- can adjust the steam supply pressure and temperature. This embodiment can be constructed in an area with a relatively stable steam supply demand, thereby improving the economy of the system and avoiding steam waste.

[0038] Based on the above specific embodiments of the molten salt energy storage system suitable for rapid peak load regulation and frequency modulation, Figure 1 As shown, it includes a liquid level meter 7 arranged on the low-level cold salt tank G3, and the liquid level meter 7 is electrically connected to the control device 4 to transmit the liquid level information of the low-level cold salt tank G3 to the control device 4 in real time. The control device 4 is used to start the high-temperature tank pump B1 to match the peak-shaving and frequency-regulating instructions of the power grid when the liquid level of the low-level cold salt tank G3 is too low. It should be noted that this can avoid the situation where the peak-shaving and frequency-regulating cannot be achieved when there is too little cold salt. When such a situation of too little cold salt occurs, the high-temperature tank pump B1 can be immediately controlled to make up for the power difference. It can be seen that the power regulation of the two pumps can be automatically realized to adapt to more situations.

[0039] In addition, based on the above specific embodiments of the molten salt energy storage system suitable for rapid peak load regulation and frequency modulation, continue to refer to Figure 1The high-position hot salt tank G2 and the low-position hot salt tank G1 can preferably be an integral hot salt tank with a gap in the middle, and the high-temperature tank pump B1 is arranged at the bottom of the integral hot salt tank, and the molten salt pipeline connecting the high-position hot salt tank G2 and the low-position hot salt tank G1 can be located inside the integral hot salt tank;

[0040] Moreover, the high-level cold salt tank G4 and the low-level cold salt tank G3 can preferably be an integral cold salt tank with a gap in the middle, and the low-temperature tank pump B2 can be arranged at the bottom of the integral cold salt tank, and the molten salt pipeline connecting the high-level cold salt tank G4 and the low-level cold salt tank G3 can be located inside the integral cold salt tank.

[0041] In this case, the heat of the two hot salt tanks and their molten salt pipelines can be retained inside the overall hot salt tank to avoid being dissipated into the external environment. Moreover, the low temperature of the two cold salt tanks and their molten salt pipelines can also be limited to the inside of the overall cold salt tank to avoid the entry of heat from the external environment. It can be seen that this embodiment can reduce the overall heat loss and further increase the amount of electrical energy storage.

[0042] Based on the above embodiments of the molten salt energy storage system suitable for rapid peak load regulation and frequency regulation, Figure 1 The heat tracing device 6 is shown to be arranged on the outer periphery of the molten salt pipeline 3, and the control device is electrically connected to the heat tracing device, and the control device is used to start the heat tracing device while starting the cryogenic tank pump. On this basis, molten salt with a wide temperature range can be selected, such as solar salt (binary salt, the available temperature range is 280℃ to 565℃), HiTec salt and quaternary salt (temperature range is 180℃ to 580℃), so as to reduce the cost of heat tracing to a greater extent.

[0043] The present invention provides a molten salt energy storage method suitable for rapid peak and frequency regulation. Figure 2 As shown, Figure 2 A schematic diagram of an embodiment of a molten salt energy storage method suitable for rapid peak shaving and frequency modulation provided by the present invention, using a molten salt energy storage system suitable for rapid peak shaving and frequency modulation as any of the above, may include the following steps:

[0044] S1: Receive power grid peak and frequency regulation instructions;

[0045] S2: Start the cryogenic tank pump to quickly raise the molten salt and put it into the high-position cold salt tank, and quickly convert the electrical energy into gravitational potential energy;

[0046] S3: Open the first valve and start the molten salt electric heater, so that the molten salt in the high-level cold salt tank flows to the low-level hot salt tank through the molten salt electric heater under the action of gravity;

[0047] S4: While gradually increasing the power of the molten salt electric heater, control the reduction of the power of the cryogenic tank pump so that the sum of the two powers matches the peak and frequency regulation instructions of the power grid;

[0048] S5: Turn off the cryogenic tank pump and only keep the molten salt electric heater on to achieve the transition to the main mode of frequency and peak regulation of the molten salt electric heater.

[0049] It should be noted that this method uses the tank pump regulation mode as a transition mode in the initial startup stage, and then gradually transitions to the main mode of peak and frequency regulation of the molten salt electric heater. This overcomes the problem in the prior art that the molten salt needs to wait for heating when starting from a static state, shortens the response time, and compared with the molten salt + electrochemical energy storage combined peak and frequency regulation mode, it has the advantages of simple structure, easy coupling, good safety, high reliability and low cost. Since the tank pump can quickly change the frequency of the operation, the frequency regulation function can be realized more easily. During the main mode operation, it can also assist in operation to improve the comprehensive peak and frequency regulation effect of the system.

[0050] In this method, when a frequency and peak regulation instruction is received, a cryogenic tank pump is used to raise the molten salt to quickly convert electrical energy into gravitational potential energy for energy storage. This cryogenic tank pump has a fast response performance, so compared with the molten salt electric heating main mode that requires preheating, it can better meet the fast response requirements for peak and frequency regulation. However, this electrical energy stored using gravitational potential energy is limited and can only play a transitional role. Therefore, after the preheating is gradually completed, the power of the cryogenic tank pump can be gradually reduced, and the power of the molten salt electric heater can be gradually increased to achieve the transition between the two peak and frequency regulation modes. In this peak and frequency regulation process, the sum of the powers of the two can be ensured to be equal to the power value in the peak and frequency regulation instruction. Moreover, since the cold salt falls into the molten salt electric heater under the action of gravity to achieve heating, the flow is faster and smoother. Therefore, this method can achieve rapid peak and frequency regulation response of the molten salt energy storage system on the basis of low cost, safety and efficiency, so that the molten salt energy storage system can be fully integrated into the power grid system to participate in peak and frequency regulation services.

[0051] The above system and method are described in detail below with a specific example:

[0052] The molten salt energy storage system is controlled by the control equipment to operate in coordination and participate in the peak-shaving and frequency-regulation of the power grid. The system can consume electric energy through the molten salt electric heater and high / low temperature tank pump (B1, B2) as variable loads to achieve the response to the peak-shaving and frequency-regulation instructions of the power grid; the peak-shaving and frequency-regulation of the molten salt electric heater is the main mode, and the high / low temperature tank pump (B1, B2) operates as a transition mode. Since the tank pump can be used for rapid frequency conversion operation, the frequency regulation function can be realized more easily. During the main mode operation, it can also be operated in an auxiliary manner to improve the comprehensive peak-shaving and frequency-regulation effect of the system; the system can also adjust the steam turbine power generation equipment 5 to provide peak power generation output through the heat exchange of the molten salt-steam heat exchanger 2, accurately respond to various regulation instructions of the power grid, and maintain the balance of the power system. The molten salt-steam heat exchanger 2 also plays the role of supplying steam to users. After the heat exchange generates high-temperature and high-pressure steam, the steam supply pressure and temperature are adjusted through the temperature reduction and pressure relief valve F-, and the steam can be introduced into the steam turbine power generation equipment 5 by opening the valve F5. The above-mentioned molten salt system receives the peak-shaving and frequency-regulating instructions from the power grid 8 when it is static. For a quick response, the low-temperature tank pump B2 is immediately started, and the peak-shaving and frequency-regulating requirements are accurately matched. At the same time, the heating system 6 is started. When the molten salt pipeline 3 reaches the operating temperature, the valve F4 is opened to allow the molten salt in the high-level cold salt tank G4 to flow to the low-level hot salt tank G1. The molten salt passes through the molten salt electric heater 1, and the molten salt electric heater 1 is started and its power is gradually increased. At the same time, the power of the low-temperature tank pump B2 is gradually reduced to achieve a smooth transition. The sum of the powers of the two always matches the instructions of the power grid 8. The reading of the liquid level gauge 7 in the low-temperature tank pump B2 is fed back to the control device 4 in real time. If the low-temperature tank pump B2 runs continuously and the liquid level of the low-level cold salt tank G3 is low and cannot be pumped, the high-temperature tank pump B1 is started to match the system load with the power grid instructions. When the power grid needs the molten salt system to provide electricity, the amount of molten salt entering the molten salt-steam heat exchanger 2 from the high-level hot salt tank G2 is immediately increased, and the steam generated passes through the steam turbine power generation equipment 5 to generate electricity and low-temperature steam. Because the system has a heating demand, the molten salt-steam heat exchanger 2 is usually in operation, and the steam generated is directly supplied to the user, that is, there is always molten salt flowing between the high-level cold salt tank G4 and the low-level hot salt tank G1, and the pipeline has no preheating link. If it is started from a static state, it will take some time for heating.

[0053] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A molten salt energy storage system suitable for rapid peak load regulation and frequency modulation, characterized in that: The invention comprises a high-position cold salt tank connected by a low-temperature tank pump and a low-position hot salt tank connected by a high-temperature tank pump, the high-position cold salt tank is connected to the molten salt inlet end of the molten salt electric heater by a first valve, and the low-position hot salt tank is connected to the molten salt outlet end of the molten salt electric heater, and a first preset height difference is provided between the high-position cold salt tank and the low-position hot salt tank. The invention also comprises a control device, which is used to start the low-temperature tank pump according to the peak-shaving and frequency-regulating instruction of the power grid to quickly raise the molten salt and let it enter the high-position cold salt tank, quickly convert the electric energy into gravitational potential energy, open the first valve, start the molten salt electric heater, so that the molten salt in the high-position cold salt tank flows to the low-position hot salt tank through the molten salt electric heater under the action of gravity, gradually increase the power of the molten salt electric heater to heat the molten salt, and control the reduction of the power of the low-temperature tank pump so that the sum of the two powers matches the peak-shaving and frequency-regulating instruction of the power grid, and finally shut down the low-temperature tank pump to realize the transition to the main mode of frequency and peak regulation of the molten salt electric heater.

2. The molten salt energy storage system suitable for rapid peak load regulation and frequency modulation according to claim 1, characterized in that: It also includes a low-level cold salt tank arranged on the molten salt pipeline and connected to the high-level cold salt tank by the low-level tank pump, and a high-level hot salt tank connected to the low-level hot salt tank by the high-level tank pump, wherein a second preset height difference is provided between the high-level hot salt tank and the low-level cold salt tank, and the low-level tank pump is used to pump the molten salt from the low-level cold salt tank to the high-level cold salt tank, and the high-level tank pump is used to pump the molten salt from the low-level hot salt tank to the high-level hot salt tank.

3. The molten salt energy storage system suitable for rapid peak load regulation and frequency modulation according to claim 2, characterized in that: It also includes a molten salt-steam heat exchanger arranged on the molten salt pipeline, the molten salt-steam heat exchanger is connected to the power grid by means of a steam turbine power generation equipment, and the molten salt-steam heat exchanger is arranged between the high-level hot salt tank and the low-level cold salt tank, and a second valve is provided between the molten salt-steam heat exchanger and the high-level hot salt tank, the molten salt-steam heat exchanger is used to convert the high-temperature molten salt from the high-level hot salt tank into steam for power generation by the steam turbine power generation equipment and to send the low-temperature molten salt obtained after cooling into the low-level cold salt tank.

4. The molten salt energy storage system suitable for rapid peak load regulation and frequency modulation according to claim 3, characterized in that: The invention also includes a first circulation pump connected in parallel with the first valve, and a second circulation pump connected in parallel with the second valve.

5. The molten salt energy storage system suitable for rapid peak load regulation and frequency modulation according to claim 4, characterized in that: A third valve is provided between the high-temperature tank pump and the low-level hot salt tank, a fourth valve is provided between the low-temperature tank pump and the low-level cold salt tank, and a fifth valve is provided between the molten salt-steam heat exchanger and the steam turbine power generation equipment.

6. The molten salt energy storage system suitable for rapid peak load regulation and frequency modulation according to claim 5, characterized in that: The molten salt-steam heat exchanger is also provided with a steam output pipeline, and a temperature and pressure reducing valve is also provided on the steam output pipeline.

7. The molten salt energy storage system suitable for rapid peak load regulation and frequency modulation according to claim 2, characterized in that: It also includes a liquid level gauge arranged on the low-level cold salt tank, which is electrically connected to the control device to transmit the liquid level information of the low-level cold salt tank to the control device in real time. The control device is used to start the high-temperature tank pump to match the peak-shaving and frequency regulation instructions of the power grid when the liquid level of the low-level cold salt tank is too low.

8. The molten salt energy storage system suitable for rapid peak load regulation and frequency modulation according to claim 2, characterized in that: The high-position hot salt tank and the low-position hot salt tank are integral hot salt tanks with a gap in the middle, and the high-temperature tank pump is arranged at the bottom of the integral hot salt tank, and the molten salt pipeline connecting the high-position hot salt tank and the low-position hot salt tank is located inside the integral hot salt tank; The high-position cold salt tank and the low-position cold salt tank are integral cold salt tanks with a gap in the middle, and the low-temperature tank pump is arranged at the bottom of the integral cold salt tank, and the molten salt pipeline connecting the high-position cold salt tank and the low-position cold salt tank is located inside the integral cold salt tank.

9. The molten salt energy storage system suitable for rapid peak load regulation and frequency modulation according to any one of claims 1 to 8, characterized in that: It also includes a heating device arranged on the outer periphery of the molten salt pipeline, the control device is electrically connected to the heating device, and the control device is used to start the heating device while starting the cryogenic tank pump.

10. A molten salt energy storage method suitable for rapid peak and frequency regulation, characterized in that: A molten salt energy storage system suitable for rapid peak load regulation and frequency regulation as claimed in any one of claims 1 to 9, comprising: Receive power grid peak and frequency regulation instructions; Starting the cryogenic tank pump to quickly raise the molten salt and put it into the high-position cold salt tank, and quickly converting the electrical energy into gravitational potential energy; Open the first valve and start the molten salt electric heater, so that the molten salt in the high-level cold salt tank flows to the low-level hot salt tank through the molten salt electric heater under the action of gravity; While gradually increasing the power of the molten salt electric heater, controlling to reduce the power of the cryogenic tank pump, so that the sum of the two powers matches the peak load and frequency regulation instruction of the power grid; The cryogenic tank pump is turned off, and only the molten salt electric heater is kept on, so as to realize the transition to the main mode of frequency and peak regulation of the molten salt electric heater.

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