Steam medium variable frequency heat storage power generation system

Abstract

A steam medium frequency heat storage power generation system, comprising a steam medium frequency heat storage power generation system, characterized by the steam medium frequency heat storage power generation system comprising a low-temperature hot water tank, a high-temperature hot water tank, a molten salt energy storage device, a counterflow heat exchanger, a compressor, an expander, a generator, four electromagnetic valves and connecting pipelines therebetween; the low-temperature hot water tank is communicated with the inlet of the compressor and the outlet of the expander; the outlet of the compressor and the inlet of the expander are communicated with one end of the counterflow heat exchanger steam channel; the other end of the counterflow heat exchanger steam channel is communicated with the high-temperature hot water tank. The application adopts water vapor as the working medium and liquid molten salt as the heat storage medium, realizes phase change access to heat energy through the design of high-temperature and low-temperature hot water tanks and the variable working condition of the compressor and the expander, improves the energy storage power generation efficiency, and is easy to implement commercially.

Description

Technical Field

[0001] This invention belongs to the field of energy storage and power generation technology in new energy, and specifically relates to a steam medium frequency conversion thermal energy storage power generation system. Background Technology

[0002] Energy storage technology is a key technology for solving the problems of large-scale integration of renewable energy and curtailment of wind and solar power; it is an essential technology for the development of distributed energy, smart grids, and the energy internet; and it is also an important supporting technology for solving peak shaving and valley filling of conventional power, improving the efficiency, security, and economy of conventional energy generation and transmission. As green energy begins to gradually replace global electricity supply, large-scale energy storage will be needed all over the world, and new technologies such as carbon dioxide energy storage, compressed air energy storage, and hydrogen energy storage are emerging one after another.

[0003] Compressed air energy storage boasts a large capacity, with single-unit capacities exceeding hundreds of megawatts, second only to pumped hydro storage. However, the compressed air used for energy storage is heated, leading to energy loss during the conversion process and low energy utilization efficiency. It has not yet been commercialized and is heavily limited by geographical conditions. To address the technical and application bottlenecks of compressed air energy storage systems, carbon dioxide energy storage is proposed. Compared to air, carbon dioxide offers unique advantages as a medium; however, its cost is high, and the main equipment is still in the research stage, requiring extensive research and development to make it more feasible. Hydrogen energy storage faces challenges due to high hydrogen costs, high power plant construction costs, low energy conversion efficiency, low technological maturity, and a long process from hydrogen production to storage, transportation, and power generation. These factors pose significant challenges to the widespread application of hydrogen energy storage power generation. Therefore, finding a new energy storage technology solution is essential. Summary of the Invention

[0004] To achieve low-cost and high-efficiency energy storage, this invention provides a steam-medium frequency conversion thermal energy storage power generation system. Compared with existing technologies, it uses steam as the working medium and molten salt as the thermal storage medium. Through the design of high and low temperature hot water tanks and the variable operating conditions of the compressor and expander, phase change thermal energy storage and extraction are achieved, improving the efficiency of energy storage power generation and facilitating commercial implementation. The specific description is as follows:

[0005] A steam medium variable frequency thermal energy storage power generation system, characterized in that the steam medium variable frequency thermal energy storage power generation system includes a low temperature hot water tank, a high temperature hot water tank, a molten salt energy storage device, a countercurrent heat exchanger, a compressor, an expander, a generator, four solenoid valves and connecting pipelines between them;

[0006] The countercurrent heat exchanger is equipped with a steam channel and a molten salt channel. One end of the steam channel is connected to the outlet of the compressor and the inlet of the expander, respectively. The other end of the steam channel is connected to the inlet of the high-temperature hot water tank through a fourth solenoid valve. At the same time, the other end of the steam channel is also connected to the outlet of the high-temperature hot water tank through a third solenoid valve.

[0007] The outlet of the low-temperature hot water tank is connected to the inlet of the compressor and the outlet of the expander through a first solenoid valve; the inlet of the low-temperature hot water tank is also connected to the inlet of the compressor and the outlet of the expander 7 through a second solenoid valve.

[0008] The molten salt energy storage device includes a high-temperature molten salt tank, a low-temperature molten salt tank, a first molten salt pump, a second molten salt pump, a first one-way valve, a second one-way valve, and connecting pipelines between them; the first molten salt pump and the first one-way valve are connected in parallel between the high-temperature molten salt tank and the molten salt channel of the countercurrent heat exchanger; the second molten salt pump and the second one-way valve are connected in parallel between the low-temperature molten salt tank and the molten salt channel of the countercurrent heat exchanger.

[0009] Furthermore, the molten salt energy storage device includes a high-temperature molten salt tank, a low-temperature molten salt tank, a four-way valve, a second molten salt pump, and connecting pipelines between them; the high-temperature molten salt tank is directly connected to the molten salt channel in the countercurrent heat exchanger, and the four-way valve and the second molten salt pump are installed between the low-temperature molten salt tank and the countercurrent heat exchanger.

[0010] Furthermore, the bottom of the low-temperature hot water tank is provided with a diverter, and the top of the diverter is provided with a diversion port, which is connected to the inlet of the low-temperature hot water tank.

[0011] Furthermore, the bottom of the high-temperature hot water tank is provided with a diverter, and the top of the diverter is provided with a diversion port, which is connected to the inlet of the high-temperature hot water tank.

[0012] Furthermore, the compressor is a variable frequency compressor; the expander is a variable frequency expander.

[0013] Furthermore, the expander is electrically connected to the generator.

[0014] The steam-medium frequency conversion thermal energy storage power generation system of this invention uses steam as the working medium and molten salt as the thermal storage medium. By reserving liquid water for consuming phase change heat in high and low temperature hot water tanks and designing a distributor, coupled with a frequency conversion compressor and frequency conversion expander operating under varying conditions according to work requirements, phase change thermal energy storage and extraction are achieved. This system features reversible energy storage and power generation, which not only improves work efficiency but also facilitates commercial implementation. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Appendix Figure 1 This is a schematic diagram of the first structure of the steam medium frequency conversion thermal energy storage power generation system of the present invention.

[0017] Appendix Figure 2 This is a schematic diagram of the second structure of the steam medium frequency conversion thermal energy storage power generation system of the present invention.

[0018] In the diagram: 1. Low-temperature hot water tank; 2. High-temperature hot water tank; 3. High-temperature molten salt tank; 4. Low-temperature molten salt tank; 5. Countercurrent heat exchanger; 6. Compressor; 7. Expander; 8. Generator; 91. First molten salt pump; 92. Second molten salt pump; 101~102. Check valve; 103. Four-way valve; 111. First solenoid valve; 112. Second solenoid valve; 113. Third solenoid valve; 114. Fourth solenoid valve; 12. Heat release valve; 131~132. Diverter. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below.

[0020] Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. To facilitate understanding of the embodiments, various embodiments or implementation methods are provided below to illustrate the relevant devices, modules, and functions of this invention. Specific Implementation Method 1

[0023] As attached Figure 1 As shown, the steam medium variable frequency thermal energy storage power generation system includes a low temperature hot water tank 1, a high temperature hot water tank 2, a molten salt energy storage device, a countercurrent heat exchanger 5, a compressor 6, an expander 7, a generator 8, four solenoid valves 111~114 and connecting pipelines between them, and the expander 7 is connected to the generator 8.

[0024] The low-temperature hot water tank 1 has a distributor 131 at its bottom and a diversion port on its top. The function of the distributor 131 is to divert the low-temperature steam medium entering the low-temperature hot water tank 1 through the distributor 131, and then allow it to enter the bottom of the tank through the diversion port. The low-temperature steam medium rises from the bottom of the tank and exchanges heat with the hot water inside. During this heat exchange, the low-temperature steam medium undergoes a phase change, becoming low-temperature hot water. The hot water in the tank absorbs the heat from the low-temperature steam medium, causing its temperature to rise. The outlet of the low-temperature hot water tank 1 is connected to the inlet of the compressor 6 and the outlet of the expander 7 via a first solenoid valve 111. The distributor 131 of the low-temperature hot water tank 1 is connected to the inside of the outlet, and the outside of the outlet is connected to the inlet of the compressor 6 and the outlet of the expander 7 via a second solenoid valve 112.

[0025] The countercurrent heat exchanger 5 is provided with a steam channel and a molten salt channel. One end of the steam channel of the countercurrent heat exchanger 5 is connected to the outlet of the compressor 6 and the inlet of the expander 7, respectively. The other end of the steam channel of the countercurrent heat exchanger 5 is connected to the inlet and outlet of the high-temperature hot water tank 2, respectively.

[0026] The molten salt energy storage device includes a high-temperature molten salt tank 3, a low-temperature molten salt tank 4, a first molten salt pump 91, a second molten salt pump 92, a first one-way valve 101, a second one-way valve 102, and connecting pipelines between them. The first molten salt pump 91 and the first one-way valve 101 are connected in parallel between the high-temperature molten salt tank 3 and the molten salt channel of the countercurrent heat exchanger 5. The second molten salt pump 92 and the second one-way valve 102 are connected in parallel between the low-temperature molten salt tank 4 and the molten salt channel of the countercurrent heat exchanger 5. The high-temperature molten salt tank 3 and the low-temperature molten salt tank 4 are installed below the countercurrent heat exchanger 5, forming a certain height difference. When the molten salt energy storage device stores heat, the second molten salt pump 92 draws molten salt from the low-temperature molten salt tank 4 and sends it into the molten salt channel of the countercurrent heat exchanger 5. The low-temperature molten salt absorbs heat from the heat transfer medium in another channel of the countercurrent heat exchanger 5 and becomes high-temperature molten salt. Then, the high-temperature molten salt returns to the high-temperature molten salt tank 3 by gravity through the first one-way valve 101. When the molten salt energy storage device releases heat, the first molten salt pump 91 draws molten salt from the high-temperature molten salt tank 3. The high-temperature molten salt is sent into the molten salt channel of the countercurrent heat exchanger 5. The high-temperature molten salt exchanges heat with the heat transfer medium in another channel of the countercurrent heat exchanger 5 and becomes low-temperature molten salt. Then, the low-temperature molten salt returns to the low-temperature molten salt tank 4 by gravity through the second one-way valve 102.

[0027] The bottom of the high-temperature hot water tank 2 is equipped with a diverter 132, and a diversion port is provided on the top of the diverter 132. Its function is to divert the high-temperature steam medium entering the high-temperature hot water tank 2 through the diverter 132, and then allow it to enter the bottom of the high-temperature hot water tank 2 through the diversion port on the diverter 131. The high-temperature steam medium rises from the bottom of the high-temperature hot water tank 2 and exchanges heat with the medium-temperature hot water in the high-temperature hot water tank 2. During the heat exchange, the high-temperature steam medium undergoes a phase change, becoming high-temperature hot water. The medium-temperature hot water in the high-temperature hot water tank 2 absorbs the heat from the high-temperature steam medium and becomes high-temperature hot water as well. The outlet of the high-temperature hot water tank 2 is connected to the steam channel of the counter-current heat exchanger 5 through a third solenoid valve 113; the inside of the inlet of the high-temperature hot water tank 2 is connected to the diverter 132, and the outside of the inlet of the high-temperature hot water tank 2 is connected to the steam channel of the counter-current heat exchanger 5 through a fourth solenoid valve 114.

[0028] The compressor 6 is a variable frequency compressor; the expander 7 is a variable frequency expander.

[0029] The steam medium variable frequency thermal energy storage power generation system of the present invention has two working modes: thermal energy storage working mode and power generation working mode.

[0030] In thermal storage mode: the first solenoid valve 111, the fourth solenoid valve 114, the compressor 6, and the second molten salt pump 92 are activated; the second solenoid valve 112, the third solenoid valve 113, the expander 7, and the first molten salt pump 91 are closed. Specifically, under the action of the compressor 6, the low-temperature hot water in the low-temperature hot water tank 1 is released through the first solenoid valve 111, undergoing a phase change to become low-temperature steam. This low-temperature steam then enters the compressor 6 and is compressed into high-temperature, high-pressure superheated steam. This high-temperature, high-pressure superheated steam enters the steam channel of the counter-current heat exchanger 5. Simultaneously, the second molten salt pump 92 draws low-temperature molten salt from the low-temperature molten salt tank 4 and sends it into the molten salt channel of the counter-current heat exchanger 5. The low-temperature molten salt absorbs the heat from the high-temperature, high-pressure superheated steam in the steam channel of the counter-current heat exchanger 5, transforming into high-temperature molten salt. Then, the high-temperature molten salt... Gravity causes the steam to return to the high-temperature molten salt tank 3 via the first one-way valve 101. Meanwhile, the high-temperature and high-pressure superheated steam in the steam channel of the counter-current heat exchanger 5 is converted into high-temperature and high-pressure steam after quantitative heat release. The high-temperature and high-pressure steam then enters the high-temperature hot water tank 2 through the distributor 132 via the fourth solenoid valve 114 for diversion. It then enters the bottom of the high-temperature hot water tank 2 through the diversion port on the distributor 131. The high-temperature and high-pressure steam medium moves upward from the bottom of the high-temperature hot water tank 2 and exchanges heat with the medium-temperature and high-pressure hot water inside the high-temperature hot water tank 2. The high-temperature and high-pressure steam medium undergoes a phase change during the heat exchange, becoming high-temperature and high-pressure hot water. The medium-temperature and high-pressure hot water inside the high-temperature hot water tank 2 absorbs the heat from the high-temperature and high-pressure steam medium and becomes high-temperature and high-pressure hot water. Finally, the heat is stored in the high-temperature hot water tank 2 in the form of high-temperature and high-pressure hot water, thus completing the heat storage working mode.

[0031] In power generation mode: the first solenoid valve 111, the fourth solenoid valve 114, the compressor 6, and the second molten salt pump 92 are closed; the second solenoid valve 112, the third solenoid valve 113, the expander 7, and the first molten salt pump 91 are open. Specifically, when the fourth solenoid valve 114 is opened, the high-temperature, high-pressure hot water in the high-temperature hot water tank 2 undergoes a phase change, becoming high-temperature, high-pressure steam. This high-temperature, high-pressure steam enters the steam channel of the counter-current heat exchanger 5. Simultaneously, the first molten salt pump 91 draws high-temperature molten salt from the high-temperature molten salt tank 3 and sends it into the molten salt channel of the counter-current heat exchanger 5. The high-temperature, high-pressure steam and the high-temperature molten salt exchange heat within the counter-current heat exchanger 5, causing the high-temperature molten salt to release heat and become low-temperature molten salt. The low-temperature molten salt then returns to the low-temperature molten salt tank 4 via the second one-way valve 102 within the counter-current heat exchanger 5 due to gravity. Simultaneously, the high-temperature, high-pressure steam absorbs high-temperature molten salt... The heat from the salt is converted into high-temperature, high-pressure superheated steam. This superheated steam enters the expander 7 to perform work, converting thermal energy into mechanical energy to drive the generator 8 and generate electricity, ultimately achieving the conversion of thermal energy into electrical energy output. The superheated steam, after performing work, is discharged through the expander 7 as low-temperature water vapor. This low-temperature steam medium enters the distributor 131 inside the low-temperature hot water tank 1 through the second solenoid valve 112 for diversion. Then, it enters the bottom of the low-temperature hot water tank 1 through the diversion port on the distributor 131. The low-temperature steam medium rises from the bottom of the low-temperature hot water tank 1 and exchanges heat with the hot water inside. During the heat exchange, the low-temperature steam medium undergoes a phase change, becoming low-temperature hot water. The hot water in the low-temperature hot water tank 1 absorbs the heat from the low-temperature steam medium, causing its temperature to rise slightly. Finally, the low-temperature hot water is stored in the low-temperature hot water tank 1, thus completing the power generation operation mode.

[0032] All processes in the described thermal storage and power generation modes are reversible.

[0033] The low-temperature hot water tank 1 described above is also connected to a heat release valve 12, which is connected to a place that requires low-quality heat. In this way, the hot water in the low-temperature hot water tank 1 can be used for different places such as low-temperature low-pressure power generation, winter heating or industrial hot water.

[0034] The first check valve 101 and the second check valve 102 mentioned above can be replaced by solenoid valves. Specific Implementation Method Two

[0036] like Figure 2 As shown, compared with Example 1 Figure 1In contrast, the molten salt energy storage device in the steam medium variable frequency thermal energy storage power generation system of the present invention includes a high-temperature molten salt tank 3, a low-temperature molten salt tank 4, a four-way valve 103, a second molten salt pump 92, and connecting pipelines between them. The high-temperature molten salt tank 3 is directly connected to the molten salt channel in the countercurrent heat exchanger 5. The low-temperature molten salt tank 4 is connected to the countercurrent heat exchanger 5 by the four-way valve 103 and the second molten salt pump 92. The connections of other components are the same as in Embodiment 1. When the molten salt energy storage device stores heat, under the action of the second molten salt pump 92, the molten salt in the low-temperature molten salt tank 4 enters the second molten salt pump 92 through the four-way valve 103, and then is sent to the molten salt channel of the countercurrent heat exchanger 5 again through the four-way valve 103. The low-temperature molten salt absorbs the heat of the high-temperature and high-pressure superheated steam in the countercurrent heat exchanger 5 and becomes high-temperature molten salt. Then the high-temperature molten salt directly returns to the high-temperature molten salt tank 3. When the molten salt energy storage device releases heat, under the action of the second molten salt pump 92, the high-temperature molten salt in the high-temperature molten salt tank 3 is sent into the molten salt channel of the counter-current heat exchanger 5. The high-temperature molten salt exchanges heat with the high-temperature and high-pressure steam of the counter-current heat exchanger 5. The high-temperature and high-pressure steam absorbs heat and becomes superheated steam, while the high-temperature molten salt releases heat and becomes low-temperature molten salt. Then, the low-temperature molten salt returns to the low-temperature molten salt tank 4 through the four-way valve 103 and the second molten salt pump 92. The installation positions of the high-temperature molten salt tank 3 and the low-temperature molten salt tank 4 are not restricted. Figure 2 The working principle of the other components in the steam medium variable frequency thermal energy storage power generation system shown is the same as that in Embodiment 1, except for the molten salt energy storage device.

Claims

1. A steam-medium frequency conversion thermal energy storage power generation system, characterized in that, The steam-medium frequency conversion thermal energy storage power generation system has two operating modes: thermal energy storage mode and power generation mode. It includes a low-temperature hot water tank, a high-temperature hot water tank, a molten salt energy storage device, a counter-current heat exchanger, a compressor, an expander, a generator, four solenoid valves, and connecting pipelines between them. The counter-current heat exchanger has internal steam and molten salt channels. One end of the steam channel is connected to the compressor outlet and the expander inlet, respectively. The other end of the steam channel is connected to the inlet of the high-temperature hot water tank via a fourth solenoid valve. Simultaneously, the other end of the steam channel is connected to a third solenoid valve... The solenoid valve is also connected to the outlet of the high-temperature hot water tank; the outlet of the low-temperature hot water tank is connected to the inlet of the compressor and the outlet of the expander through a first solenoid valve; the inlet of the low-temperature hot water tank is also connected to the inlet of the compressor and the outlet of the expander through a second solenoid valve; the molten salt energy storage device includes a high-temperature molten salt tank, a low-temperature molten salt tank, a first molten salt pump, a second molten salt pump, a first one-way valve, a second one-way valve, and connecting pipelines between them; the first molten salt pump and the first one-way valve are connected in parallel between the high-temperature molten salt tank and the molten salt channel of the countercurrent heat exchanger; the second molten salt pump and the second one-way valve are connected in parallel between the low-temperature molten salt tank and the molten salt channel of the countercurrent heat exchanger; The working process of the heat storage mode includes: the compressor draws low-temperature hot water from the low-temperature hot water tank, which is then converted into low-temperature steam after passing through the first solenoid valve, and compressed into high-temperature and high-pressure superheated steam, which enters the steam channel of the counter-current heat exchanger; the second molten salt pump sends the low-temperature molten salt from the low-temperature molten salt tank into the molten salt channel of the heat exchanger, where it absorbs the heat of the steam and becomes high-temperature molten salt, which returns to the high-temperature molten salt tank through the first one-way valve; after the steam releases heat, it becomes high-temperature and high-pressure steam, which enters the high-temperature hot water tank through the fourth solenoid valve, where it exchanges heat with the medium-temperature and high-pressure hot water in the tank and is converted into high-temperature and high-pressure hot water. The medium-temperature hot water absorbs heat and becomes high-temperature and high-pressure hot water for storage, thus completing the heat storage; The power generation operation mode includes the following steps: Opening the fourth solenoid valve causes the high-temperature, high-pressure hot water in the high-temperature hot water tank to transform into high-temperature, high-pressure steam, which then enters the steam channel of the counter-current heat exchanger via the third solenoid valve; the first molten salt pump sends the high-temperature molten salt from the high-temperature molten salt tank into the molten salt channel of the heat exchanger, where it releases heat and transforms into low-temperature molten salt, which then returns to the low-temperature molten salt tank via the second one-way valve; the steam absorbs heat and transforms into high-temperature, high-pressure superheated steam, which enters the expander to drive the generator and generate electricity; the low-temperature steam after absorbing heat enters the low-temperature hot water tank via the second solenoid valve, where it exchanges heat with the hot water and transforms into low-temperature hot water. The hot water in the tank absorbs heat and stores the low-temperature hot water, thus completing the power generation process. All processes in the heat storage and power generation modes are reversible. The low-temperature hot water tank is also connected to a heat release valve, which connects to a location with low-quality heat. The hot water in the low-temperature hot water tank is used for low-temperature, low-pressure power generation, winter heating, or industrial hot water applications.

2. The steam medium variable frequency thermal energy storage power generation system as described in claim 1, characterized in that, The molten salt energy storage device includes a high-temperature molten salt tank, a low-temperature molten salt tank, a four-way valve, a second molten salt pump, and connecting pipelines between them; the high-temperature molten salt tank is directly connected to the molten salt channel in the countercurrent heat exchanger, and the four-way valve and the second molten salt pump are installed between the low-temperature molten salt tank and the countercurrent heat exchanger.

3. The steam medium variable frequency thermal energy storage power generation system as described in claim 1, characterized in that, The bottom of the low-temperature hot water tank is equipped with a diverter, and the top of the diverter is equipped with a diversion port. The diverter is connected to the inlet of the low-temperature hot water tank.

4. The steam medium variable frequency thermal energy storage power generation system as described in claim 1, characterized in that, The bottom of the high-temperature hot water tank is equipped with a diverter, and the top of the diverter is equipped with a diversion port. The diverter is connected to the inlet of the high-temperature hot water tank.

5. The steam medium variable frequency thermal energy storage power generation system as described in claim 1, characterized in that, The compressor is a variable frequency compressor; the expander is a variable frequency expander.

6. The steam medium variable frequency thermal energy storage power generation system as described in claim 1, characterized in that, The expander is electrically connected to the generator.

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