A pressure self-balancing high-temperature hot water thermal storage system and its operation method

Abstract

This invention discloses a pressure self-balancing high-temperature hot water thermal storage system and its operation method. The system includes: at least one hot water storage tank for storing high-temperature hot water; at least one cold water storage tank for storing low-temperature water; the at least one cold water storage tank and the at least one hot water storage tank are interconnected by a gas connecting pipe, the input end of which is connected to a gas supply mechanism, which provides high-pressure gas to the cold water and hot water storage tanks through the gas connecting pipe and maintains the gas pressure inside the tanks; the at least one cold water storage tank and the at least one hot water storage tank are connected by at least one set of water conveying systems, each set of water conveying systems including a water conveying pipe, a heat exchanger, and a water pump, the water pump being used to pump water from the hot water storage tank towards the cold water storage tank and / or from the cold water storage tank towards the hot water storage tank through the water conveying pipe. This invention uses 180℃ high-temperature hot water for thermal storage, solving the problem of high investment in thermal storage systems, and simultaneously solving the problem of maintaining pressure in high-pressure, high-temperature hot water thermal storage systems.

Description

Technical Field

[0001] This invention relates to the field of thermal storage technology in compressed air energy storage power stations, specifically to a pressure self-balancing high-temperature hot water thermal storage system and its operation method. Background Technology

[0002] Currently, there are two main technical approaches for non-combustion compressed air energy storage power stations: isothermal compression and adiabatic compression. The isothermal compression approach uses 120℃ low-pressure hot water for thermal storage, while the adiabatic compression approach uses 330℃ heat transfer oil. As the thermal storage temperature increases, the overall efficiency of the power station improves.

[0003] However, as the unit capacity increases, if high-temperature heat transfer oil is used for heat storage, the required capacity of heat transfer oil would be enormous, resulting in excessive investment. Using 120℃ low-temperature hot water for heat storage would lead to low overall power plant efficiency.

[0004] Using high-temperature hot water for thermal storage can significantly reduce investment in the system while maintaining high efficiency in compressed air energy storage power stations. To ensure the hot water remains liquid and prevent overheating, the storage tank needs to maintain high pressure. Without pressurization, the pressure inside the tank decreases as the water level drops, causing the water to boil and affecting system safety. Using external high-pressure air to maintain the pressure results in significant waste of both high-pressure air and energy.

[0005] Based on the above, this invention proposes a pressure self-balancing high-temperature hot water storage system and its operation method, which can effectively solve the above problems. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a pressure-self-balancing high-temperature hot water thermal storage system and its operation method. This invention utilizes 180℃ high-temperature hot water for thermal storage, solving the problem of high investment in high-temperature thermal oil thermal storage systems, while also addressing the low efficiency of compressed air energy storage power stations caused by 120℃ low-temperature hot water thermal storage. By connecting the cold water storage tank and the hot water storage tank through a gas interconnection pipe, the problem of maintaining pressure in high-pressure, high-temperature hot water thermal storage systems is solved.

[0007] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0008] On one hand, the present invention provides a pressure self-balancing high-temperature hot water thermal storage system, the high-temperature hot water thermal storage system comprising:

[0009] At least one hot water storage tank for storing high-temperature hot water (180°C);

[0010] At least one cold water storage tank for storing low-temperature cold water (50°C);

[0011] The at least one cold water storage tank and the at least one hot water storage tank are interconnected by a gas connecting pipe. The input end of the gas connecting pipe is connected to a gas supply mechanism. The gas supply mechanism is used to supply high-pressure gas for initial filling to the cold water storage tank and the hot water storage tank through the gas connecting pipe and to maintain the gas pressure inside the tank after the system is running. Nitrogen is preferred as the high-pressure gas, but high-pressure air can also be used.

[0012] The at least one cold water storage tank and the at least one hot water storage tank are connected by at least one set of water conveyance systems. Each set of water conveyance systems includes a water conveyance pipe, a heat exchanger, and a water pump. The water pump is used to pump water from the hot water storage tank to the cold water storage tank and / or from the cold water storage tank to the hot water storage tank through the water conveyance pipe.

[0013] Preferably, the at least one cold water storage tank and the at least one hot water storage tank have the same capacity, or the capacity of the at least one cold water storage tank is slightly smaller than the capacity of the at least one hot water storage tank.

[0014] Preferably, the maximum pressure withstand value of the at least one cold water storage tank and the at least one hot water storage tank must be at least 1.5 MPa, and the maximum temperature withstand value of the at least one hot water storage tank must be at least 180°C; the operating temperature of the hot water storage tank is 180°C, and the pressure of the high-pressure gas is not less than 1 MPa.

[0015] Preferably, the number of cold water storage tanks and hot water storage tanks is set to multiple, and the multiple cold water storage tanks and multiple hot water storage tanks are arranged at intervals and are all on the same horizontal plane.

[0016] Preferably, the water supply system is configured in two sets, with one set of water pumps drawing water from the hot water storage tank to the cold water storage tank via a water supply pipe, and the other set of water pumps drawing water from the cold water storage tank to the hot water storage tank via a water supply pipe.

[0017] Preferably, the water pump is a unidirectional water pump or a bidirectional water pump.

[0018] Preferably, valves are installed on the water supply pipes near the cold water storage tank and the hot water storage tank, on the delivery pipes near the water pump, and on the gas connection pipes near the gas supply mechanism.

[0019] Preferably, both the cold water storage tank and the hot water storage tank are spherical tanks or C-shaped horizontal tanks.

[0020] On the other hand, the present invention also provides an operation method for a pressure self-balancing high-temperature hot water storage system, wherein the pressure self-balancing high-temperature hot water storage system of the above scheme is pre-assembled, and the operation method includes:

[0021] Preparation:

[0022] Before the system is started, water is first injected into the cold water storage tank and the water supply pipe. Then, the gas supply mechanism is started to input high-pressure gas into the cold water storage tank and the hot water storage tank so that the gas pressure in the tank reaches the pressure set value. After the system is started, when the gas pressure drops, the gas supply mechanism is automatically started to replenish the gas to the system and maintain the gas pressure not lower than the pressure set value.

[0023] Thermal storage process:

[0024] Low-temperature water in the cold water storage tank is pumped to the heat exchanger and heated to the high temperature set value. Then it is sent to the hot water storage tank for storage. The high-pressure gas in the hot water storage tank flows to the cold water storage tank through the gas connection pipe as the water level rises. When the heat storage process ends, the water level in the cold water storage tank drops to the protection level, and the upper part is replaced by high-pressure gas.

[0025] Exothermic process:

[0026] The high-temperature hot water in the hot water storage tank is pumped to the heat exchanger to heat the gas. After the hot water is cooled to the low temperature set value, it is sent to the cold water storage tank for storage. The high-pressure gas in the cold water storage tank flows to the hot water storage tank through the gas connection pipe as the water level rises. When the heat release process ends, the water level in the hot water storage tank drops to the protection water level, and the upper part is replaced by high-pressure gas.

[0027] By repeating the above heat storage and release process, heat storage and release can be achieved in a cyclical manner.

[0028] Preferably, the water injected into the cold water storage tank and the water supply pipe is demineralized water or industrial water.

[0029] Preferably, the high temperature setting is 180°C, the low temperature setting is 50°C, and the pressure setting is 1 MPa.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] 1. Taking into account both investment and power plant efficiency, and based on the physical properties of water and steam, this invention proposes a scheme for thermal storage using 180°C high-temperature hot water. This not only significantly reduces the investment in the thermal storage system (the maximum pressure withstand value of the hot water storage tank and the cold water storage tank only needs to reach 1.5MPa or higher), but also maintains high efficiency in the compressed air energy storage power station. This solves the problems of high investment in thermal storage systems and low efficiency in compressed air energy storage power stations caused by the use of low-temperature hot water for thermal storage, thus balancing both investment and power plant efficiency.

[0032] 2. This invention connects hot water and cold water storage tanks via an upper air duct. During the initial operation of the system, high-pressure air is injected to maintain a certain pressure within the system. When the hot water tank supplies water to the cold water tank, the high-pressure air is forced into the hot water tank, maintaining a high-pressure state thereafter, and vice versa. This avoids the significant energy waste caused by using external high-pressure air to maintain pressure and solves the problem of maintaining pressure in high-pressure, high-temperature hot water storage systems. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a pressure self-balancing high-temperature hot water storage system according to Embodiment 1 of the present invention.

[0034] Figure 2 This is a schematic diagram of a pressure self-balancing high-temperature hot water storage system according to Embodiment 2 of the present invention.

[0035] Figure 3 This is a schematic diagram of a pressure self-balancing high-temperature hot water storage system according to Embodiment 3 of the present invention.

[0036] Figure 4 This is a schematic diagram of a pressure self-balancing high-temperature hot water storage system according to Embodiment 4 of the present invention.

[0037] Figure 5 This is a schematic diagram of a pressure self-balancing high-temperature hot water storage system according to Embodiment 5 of the present invention.

[0038] Figure 6 This is a graph showing the change of water saturation pressure as temperature rises in an embodiment of the present invention.

[0039] Attached reference numerals: 1-Hot water storage tank; 2-Cold water storage tank; 3-Gas connection pipe; 4-Gas supply mechanism; 5-Water supply system; 51-Water supply pipe; 52-Heat exchanger; 53-Water pump; 6-Valve. Detailed Implementation

[0040] To enable those skilled in the art to better understand the technical solutions of the present invention, preferred embodiments of the present invention are described below in conjunction with specific examples. However, it should be understood that the accompanying drawings are for illustrative purposes only and should not be construed as limiting the present patent. For better illustration of this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable that some well-known structures and their descriptions may be omitted in the drawings for those skilled in the art. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting the present patent.

[0041] The following is in conjunction with the appendix Figure 1-6 The embodiments further illustrate the present invention, but are not intended to limit the present invention.

[0042] Example 1

[0043] like Figure 1 As shown, this embodiment provides a pressure self-balancing high-temperature hot water storage system. The high-temperature hot water storage system includes a hot water storage tank 1 and a cold water storage tank 2. The cold water storage tank 2 and the hot water storage tank 1 are interconnected by a gas connecting pipe 3. The input end of the gas connecting pipe 3 is connected to a gas supply mechanism 4. The gas supply mechanism 4 is used to supply high-pressure gas to the cold water storage tank 2 and the hot water storage tank 1 through the gas connecting pipe 3 and maintain the gas pressure inside the tank. The cold water storage tank 2 and the hot water storage tank 1 are connected by a water conveying system 5. The water conveying system 5 includes a water conveying pipe 51, a heat exchanger 52 and a water pump 53. The water pump 53 can be used to pump water from the hot water storage tank 1 to the cold water storage tank 2 and from the cold water storage tank 2 to the hot water storage tank 1 through the water conveying pipe 51.

[0044] Both the hot water storage tank 1 and the cold water storage tank 2 are large-capacity pressure-bearing structures of the same capacity, preferably spherical tanks. Safety valves are installed at the top of both the hot water storage tank 1 and the cold water storage tank 2 to ensure that the pressure inside the tanks remains below a safe level. Nitrogen is preferred as the high-pressure gas, but high-pressure air can also be used.

[0045] The gas connecting pipe 3 is connected to the top of the hot water storage tank 1 and the cold water storage tank 2 respectively, and the inlet and outlet of the water supply pipe 51 are connected to the bottom of the hot water storage tank 1 and the cold water storage tank 2 respectively.

[0046] Specifically, in this embodiment, the gas supply mechanism 4 is an air compressor. The air compressor can fill the tank with air according to the pressure drop in the hot water storage tank 1 and the cold water storage tank 2 to maintain the air pressure inside the tank. The real-time air pressure data can be monitored by a pressure sensor (not shown in the figure, but a conventional selection in the field can be used).

[0047] Specifically, in this embodiment, the water pump 53 is a bidirectional water pump, which can be used to pump water from the hot water storage tank 1 to the cold water storage tank 2 and from the cold water storage tank 2 to the hot water storage tank 1 through the water delivery pipe 51, and the water delivery direction can be switched.

[0048] Specifically, in this embodiment, valves 6 are installed on the water supply pipe 51 near the cold water storage tank 2 and the hot water storage tank 1, on the delivery pipe near the water pump 53, and on the gas connection pipe 3 near the gas supply mechanism 4.

[0049] like Figure 6As shown, within the 50-180℃ range, the corresponding saturation pressure value changes very little with increasing temperature; however, above 180℃, the corresponding saturation pressure value rises sharply, placing high pressure requirements on the storage tank. Considering both investment and power plant efficiency, and based on the physical properties of water and steam, this invention proposes a scheme using 180℃ high-temperature hot water for thermal storage. The saturation pressure corresponding to 180℃ hot water is 1MPa, which offers the best economic efficiency and ensures the hot water does not boil. In this embodiment, to ensure the safe operation of the system equipment, the maximum pressure withstand value of both the cold water storage tank 2 and the hot water storage tank 1 is set at 1.6MPa, and the maximum temperature withstand value of the hot water storage tank 1 is set above 180℃.

[0050] This embodiment also provides an operation method for a pressure self-balancing high-temperature hot water thermal storage system. The pressure self-balancing high-temperature hot water thermal storage system described above is pre-assembled. The operation method includes:

[0051] Preparation:

[0052] Before the system is started, water is first injected into the cold water storage tank 2 and the water supply pipe 51. Then, the gas supply mechanism 4 is started to input high-pressure gas into the cold water storage tank 2 and the hot water storage tank 1 so that the gas pressure in the tank reaches the pressure set value. After the system is started, when the gas pressure drops, the gas supply mechanism 4 is automatically started to replenish the gas to the system and maintain the gas pressure not lower than the pressure set value of 1MPa.

[0053] Thermal storage process:

[0054] The low-temperature water in the cold water storage tank 2 is pumped to the heat exchanger 52 by the water pump 53 and heated to the high temperature set value of 180°C. Then it is sent to the hot water storage tank 1 for storage. The high-pressure gas in the hot water storage tank 1 flows to the cold water storage tank 2 through the gas connecting pipe 3 as the water level rises. When the heat storage process ends, the water level in the cold water storage tank 2 drops to the protection water level, and the upper part is replaced by high-pressure gas.

[0055] Exothermic process:

[0056] The high-temperature hot water in the hot water storage tank 1 is sent to the heat exchanger 52 to heat the gas via the water pump 53. After the hot water is cooled to the low temperature set value of 50°C, it is sent to the cold water storage tank 2 for storage. The high-pressure gas in the cold water storage tank 2 flows to the hot water storage tank 1 through the gas connecting pipe 3 as the water level rises. When the heat release process ends, the water level in the hot water storage tank 1 drops to the protection water level, and the upper part is replaced by high-pressure gas.

[0057] By repeating the above heat storage and release process, heat storage and release can be achieved in a cyclical manner.

[0058] The water injected into the cold water storage tank 2 and the water supply pipe 51 is either demineralized water or tap water. The air in the water supply pipe 51 must be purged, and the water level in the cold water storage tank 2 must not be lower than the protection water level.

[0059] Example 2

[0060] like Figure 2 As shown, the difference between this embodiment and Embodiment 1 is that this embodiment includes three hot water storage tanks 1 and three cold water storage tanks 2. These three hot water storage tanks 1 and three cold water storage tanks 2 are arranged at intervals and are all on the same horizontal plane. Appropriately increasing the number of hot water storage tanks 1 and cold water storage tanks 2 can increase the overall heat storage capacity of the system and improve heat storage efficiency. Specifically, to supply the water flow between the three hot water storage tanks 1 and the three cold water storage tanks 2, three water pumps 53 are installed on the water supply pipe 51 to improve water supply efficiency.

[0061] Example 3

[0062] like Figure 3 As shown, the difference between this embodiment and embodiment one is that this embodiment is provided with two sets of water supply systems 5. The pumping components on each set of water supply systems 5 are all unidirectional water pumps. That is, one unidirectional water pump pumps water from the hot water storage tank 1 to the cold water storage tank 2, and the other unidirectional water pump pumps water from the cold water storage tank 2 to the hot water storage tank 1.

[0063] Example 4

[0064] like Figure 4 As shown, the difference between this embodiment and Embodiment 3 is that this embodiment includes three hot water storage tanks 1 and three cold water storage tanks 2. Appropriately increasing the number of hot water storage tanks 1 and cold water storage tanks 2 can increase the overall heat storage capacity of the system and improve the heat storage efficiency. Specifically, in order to supply the water volume between the three hot water storage tanks 1 and the three cold water storage tanks 2, three water pumps 53 are installed on the water supply pipe 51 to improve the water supply efficiency.

[0065] Example 5

[0066] like Figure 5 As shown, the difference between this embodiment and embodiment four is that both the cold water storage tank 2 and the hot water storage tank 1 in this embodiment are C-shaped horizontal tanks, which are suitable for thermal storage systems with smaller volume requirements.

[0067] Based on the description and accompanying drawings of this invention, those skilled in the art can easily manufacture or use the pressure self-balancing high-temperature hot water storage system of this invention, and can produce the positive effects described in this invention.

[0068] Unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" in this invention should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A pressure self-balancing high-temperature hot water storage system, characterized in that, The high-temperature hot water storage system includes: At least one hot water storage tank for storing high-temperature hot water; At least one cold water storage tank for storing low-temperature cold water; The at least one cold water storage tank and the at least one hot water storage tank are interconnected by a gas connecting pipe. The input end of the gas connecting pipe is connected to a gas supply mechanism. The gas supply mechanism is used to provide high-pressure gas for initial filling to the cold water storage tank and the hot water storage tank through the gas connecting pipe and to maintain the gas pressure inside the tank after the system is running. The at least one cold water storage tank and the at least one hot water storage tank are connected by at least one set of water conveyance systems. Each set of water conveyance systems includes a water conveyance pipe, a heat exchanger and a water pump. The water pump is used to pump water from the hot water storage tank to the cold water storage tank and / or from the cold water storage tank to the hot water storage tank through the water conveyance pipe. The maximum pressure withstand value of the at least one cold water storage tank and the at least one hot water storage tank must be at least 1.5 MPa, and the maximum temperature withstand value of the at least one hot water storage tank must be at least 180°C; the operating temperature of the hot water storage tank is 180°C, and the pressure of the high-pressure gas is not less than 1 MPa; the high-pressure gas is high-pressure nitrogen or high-pressure air. The operation method of the high-temperature hot water storage system includes: Preparation: Before the system is started, water is first injected into the cold water storage tank and the water supply pipe. Then, the gas supply mechanism is started to input high-pressure gas into the cold water storage tank and the hot water storage tank so that the gas pressure in the tank reaches the pressure set value. After the system is started, when the gas pressure drops, the gas supply mechanism is automatically started to replenish the gas to the system and maintain the gas pressure not lower than the pressure set value. Thermal storage process: Low-temperature water in the cold water storage tank is pumped to the heat exchanger and heated to the high temperature set value. Then it is sent to the hot water storage tank for storage. The high-pressure gas in the hot water storage tank flows to the cold water storage tank through the gas connection pipe as the water level rises. When the heat storage process ends, the water level in the cold water storage tank drops to the protection level, and the upper part is replaced by high-pressure gas. Exothermic process: The high-temperature hot water in the hot water storage tank is pumped to the heat exchanger to heat the gas. After the hot water is cooled to the low temperature set value, it is sent to the cold water storage tank for storage. The high-pressure gas in the cold water storage tank flows to the hot water storage tank through the gas connection pipe as the water level rises. When the heat release process ends, the water level in the hot water storage tank drops to the protection water level, and the upper part is replaced by high-pressure gas. By repeating the above heat storage and release process, heat storage and release can be achieved in a cyclical manner.

2. The pressure self-balancing high-temperature hot water storage system according to claim 1, characterized in that: The at least one cold water storage tank and the at least one hot water storage tank have the same capacity, or the at least one cold water storage tank has a slightly smaller capacity than the at least one hot water storage tank.

3. The pressure self-balancing high-temperature hot water storage system according to claim 1, characterized in that: The number of cold water storage tanks and hot water storage tanks is set to multiple, and the multiple cold water storage tanks and multiple hot water storage tanks are arranged at intervals and are all on the same horizontal plane.

4. The pressure self-balancing high-temperature hot water storage system according to claim 1, characterized in that: The water supply system is configured in two sets. In one set, the water pumps draw water from the hot water storage tank to the cold water storage tank through the water supply pipe. In the other set, the water pumps draw water from the cold water storage tank to the hot water storage tank through the water supply pipe.

5. The pressure self-balancing high-temperature hot water storage system according to claim 1, characterized in that: The water pump is either a unidirectional water pump or a bidirectional water pump.

6. The pressure self-balancing high-temperature hot water storage system according to claim 1, characterized in that: Valves are installed on the water supply pipes near the cold water storage tank and hot water storage tank, on the delivery pipes near the water pump, and on the gas connection pipes near the gas supply mechanism.

7. The pressure self-balancing high-temperature hot water storage system according to claim 1, characterized in that: The water injected into the cold water storage tank and the water supply pipe is demineralized water or industrial water.

8. The pressure self-balancing high-temperature hot water storage system according to claim 1, characterized in that: The high temperature setting is 180℃, the low temperature setting is 50℃, and the pressure setting is 1MPa.

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