High-efficiency flow battery system based on heat recovery

Abstract

The utility model discloses a high-efficiency flow battery system based on heat recovery. The high-efficiency flow battery system comprises a flow battery system, a heat pump and a heat storage water tank, the heat pump comprises two heat pump cycles which are composed of a condenser, a throttling valve, an evaporator, a secondary evaporation heat exchanger and a compressor and can be switched through a three-way valve. The heat storage water tank is connected with the heat exchange medium side of the condenser to form a heat storage loop; a first coil pipe is arranged in an electrolyte storage tank of the flow battery system, and the first coil pipe is connected with a heat exchange medium side of a secondary evaporation heat exchanger to form a heat recovery loop; a second coil pipe is arranged in the heat storage water tank and is connected with the first coil pipe to form an electrolyte preheating loop; and the heat recovery loop and the electrolyte preheating loop can be switched through corresponding three-way valves. According to the system, the problems of electrolyte waste heat recycling and electrolyte preheating during cold start are solved through cooperation of one set of system, the heat utilization rate of the system is improved, and meanwhile the design and operation difficulty is lowered.

Description

Technical Field

[0001] This utility model relates to the field of flow battery technology, and in particular to a high-efficiency flow battery system based on heat recovery. Background Technology

[0002] Flow batteries are an electrochemical energy storage technology, mainly composed of a stack unit, electrolyte, electrolyte storage and supply unit, and management and control unit. They utilize the principle of separate, independently circulating positive and negative electrolytes to achieve the conversion of chemical energy into electrical energy. During the charging and discharging process, there is some energy loss in the conversion between electrical and chemical energy in flow batteries. Most of this lost energy remains in the electrolyte, causing its temperature to rise. In flow battery systems operating in continuous charge and discharge mode, measures need to be taken to cool the electrolyte. At low temperatures, the viscosity of the electrolyte increases, and its fluidity decreases, leading to a slower chemical reaction rate inside the battery and a longer start-up time. Effective heating measures are needed to raise the electrolyte temperature and shorten the start-up time.

[0003] In existing technologies, most electrolyte waste heat recovery solutions involve drawing the electrolyte outside the battery system, exchanging heat, and then returning it to the battery system. Because the electrolyte waste heat temperature is low, there is some energy loss during energy conversion, resulting in low waste heat utilization efficiency. Furthermore, using a separate preheating system to preheat the electrolyte during cold starts increases the complexity of the flow battery system, requiring coordination and control of waste heat collection, transmission, and utilization, thus increasing the design and operation difficulty of the system. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a high-efficiency flow battery system based on heat recovery. The aim is to use a single system to collaboratively solve the problems of electrolyte waste heat recovery and electrolyte preheating during cold start, thereby improving the system's thermal efficiency while reducing its design and operation complexity.

[0005] The technical solution adopted in this utility model is as follows:

[0006] A high-efficiency flow battery system based on heat recovery includes a flow battery system, a heat pump, and a hot water storage tank;

[0007] The heat pump includes a condenser, a throttle valve, an evaporator, a secondary evaporation heat exchanger, and a compressor. The condenser, throttle valve, evaporator, and compressor are connected in sequence on the refrigerant side to form a first heat pump cycle. The condenser, throttle valve, evaporator, secondary evaporation heat exchanger, and compressor are connected in sequence on the refrigerant side to form a second heat pump cycle. The refrigerant outlet of the evaporator, the refrigerant inlet of the secondary evaporation heat exchanger, and the inlet of the compressor are connected by a first three-way valve to achieve switching between the two heat pump cycles.

[0008] The hot water storage tank is connected to the heat exchange medium side of the condenser to form a heat storage circuit;

[0009] The electrolyte storage tank of the flow battery system is equipped with a first coil, which is connected to the heat exchange medium side of the secondary evaporation heat exchanger to form a heat recovery loop.

[0010] The hot water storage tank is equipped with a second coil, which is connected to the first coil to form an electrolyte preheating circuit.

[0011] The first coil inlet, the heat exchange medium side outlet of the secondary evaporation heat exchanger, and the second coil outlet are connected by a second three-way valve, and the first coil outlet, the heat exchange medium side inlet of the secondary evaporation heat exchanger, and the second coil inlet are connected by a third three-way valve to realize the switching between the heat recovery circuit and the electrolyte preheating circuit.

[0012] The further technical solution is as follows:

[0013] The heat exchange medium used in the heat recovery circuit and the electrolyte preheating circuit is water or ethylene glycol.

[0014] The heat recovery circuit and the electrolyte preheating circuit are equipped with a first circulating pump, which is located at the inlet end of the first coil.

[0015] The heat exchange medium in the thermal storage circuit is water.

[0016] The hot water storage tank is connected to the heat user to form a heating circuit, and the heating circuit is equipped with a hot water valve and a return water pump.

[0017] The heat storage circuit is also connected to a water supply pipe, and the output end of the water supply pipe is connected to the heat exchange medium side inlet of the condenser.

[0018] The heat storage circuit is equipped with a second circulation pump, which is located at the outlet end of the heat exchange medium side of the condenser.

[0019] The surface of the first coil is provided with insulating material.

[0020] The electrolyte storage tank includes a cathode electrolyte storage tank and an anode electrolyte storage tank. The first coil includes two coil units connected in series, and the two coil units are respectively located in the cathode electrolyte storage tank and the anode electrolyte storage tank.

[0021] The anode electrolyte storage tank is connected to the anode of the flow battery to form an anode circuit, and the cathode electrolyte storage tank is connected to the cathode of the flow battery to form a cathode circuit. Electrolyte pumps are respectively installed on the anode circuit and the cathode circuit.

[0022] The beneficial effects of this utility model are as follows:

[0023] This invention employs a heat pump system with two heat pump cycles, combined with a flow battery system and a hot water storage tank, to construct a heat recovery circuit, an electrolyte preheating circuit, and a heat storage circuit. During operation, by switching between the two heat pump cycles and between the electrolyte preheating circuit and the heat storage circuit, this invention can recover low-grade electrolyte waste heat during normal operation of the flow battery system, preheat the electrolyte during cold starts, and supply the additional heat generated by the system to heat users. This meets the application needs of the flow battery system under different scenarios and operating conditions, improves the efficiency of the flow battery system and the overall energy utilization rate, and simultaneously reduces the design and operation control complexity of the system.

[0024] The electrolyte waste heat recovery of this utility model adopts an "in-situ" heat exchange method, that is, the electrolyte is always located in the storage tank, which avoids the problem of uneven temperature control caused by temperature changes of the electrolyte during transportation and ensures the stability of operation.

[0025] This invention uses the same system to realize electrolyte waste heat recovery and electrolyte preheating during cold start, which improves the synergy of the system structure and reduces the complexity and difficulty of operation and control of the system.

[0026] The heat pump of this invention has a secondary evaporation heat exchanger installed after the evaporator, which improves the efficiency of the second heat pump cycle.

[0027] Other features and advantages of this invention will be set forth in the following description or may be learned by practicing this invention. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the system structure of an embodiment of the present utility model.

[0029] In the diagram: 1. Electrolyte storage tank; 2. Third three-way valve; 3. Electrolyte pump; 4. Flow battery; 5. Second three-way valve; 6. First circulation pump; 7. Secondary evaporation heat exchanger; 8. First three-way valve; 9. Evaporator; 10. Throttling valve; 11. Condenser; 12. Compressor; 13. Hot water storage tank; 14. Return water pipe; 15. Return water pump; 16. Hot water valve; 17. Water supply pipe; 18. Second circulation pump; 19. Makeup water pipe; 20. First coil; 21. Second coil; 22. Heat user. Detailed Implementation

[0030] The specific embodiments of this utility model are described below with reference to the accompanying drawings.

[0031] See Figure 1 The high-efficiency flow battery system based on heat recovery in this embodiment includes a flow battery system, a heat pump, and a hot water storage tank 13.

[0032] In this embodiment, the heat pump includes a condenser 11, a throttle valve 10, an evaporator 9, a secondary evaporation heat exchanger 7, and a compressor 12. The condenser 11, the throttle valve 10, the evaporator 9, and the compressor 12 are connected sequentially on the refrigerant side to form a first heat pump cycle. The condenser 11, the throttle valve 10, the evaporator 9, the secondary evaporation heat exchanger 7, and the compressor 12 are connected sequentially on the refrigerant side to form a second heat pump cycle. The refrigerant side outlet of the evaporator 9, the refrigerant side inlet of the secondary evaporation heat exchanger 7, and the inlet of the compressor 12 are connected by a first three-way valve 8 to achieve switching between the two heat pump cycles.

[0033] Specifically, the first three-way valve 8 has three ports, a, b, and c, which are respectively connected to the refrigerant side inlet of the secondary evaporator heat exchanger 7, the compressor inlet 12, and the refrigerant side outlet of the evaporator 9.

[0034] In this embodiment, the hot water storage tank 13 is connected to the heat exchange medium side of the condenser 11 to form a heat storage circuit.

[0035] As a preferred method, the heat exchange medium in the thermal storage circuit is water.

[0036] As a preferred embodiment, the heat storage circuit is also connected to a water supply pipe 19, the output end of which is connected to the heat exchange medium side inlet of the condenser 11.

[0037] As a preferred embodiment, a second circulation pump 18 is provided on the heat storage circuit, which is located at the outlet end of the heat exchange medium side of the condenser 11.

[0038] In this embodiment, the electrolyte storage tank 1 of the flow battery system is provided with a first coil 20, which is connected to the heat exchange medium side of the secondary evaporation heat exchanger 7 to form a heat recovery circuit.

[0039] The hot water storage tank 13 is equipped with a second coil 21, which is connected to the first coil 20 to form an electrolyte preheating circuit.

[0040] The inlet of the first coil 20, the outlet of the heat exchange medium side of the secondary evaporator heat exchanger 7, and the outlet of the second coil 21 are connected by a second three-way valve 5, and the outlet of the first coil 20, the inlet of the heat exchange medium side of the secondary evaporator heat exchanger 7, and the inlet of the second coil 21 are connected by a third three-way valve 2, so as to realize the switching between the heat recovery circuit and the electrolyte preheating circuit.

[0041] Specifically, the second three-way valve 5 has three ports, a, b, and c, which are respectively connected to the inlet of the first coil 20, the heat exchange medium side outlet of the secondary evaporation heat exchanger 7, and the outlet of the second coil 21.

[0042] Specifically, the third three-way valve 2 has three ports, a, b, and c, which are respectively connected to the outlet of the first coil 20, the heat exchange medium side inlet of the secondary evaporation heat exchanger 7, and the inlet of the second coil 21.

[0043] As a preferred embodiment, the heat exchange medium used in the heat recovery circuit and the electrolyte preheating circuit is water or ethylene glycol. Ethylene glycol, in particular, can meet the requirements of the flow battery system for cold start-up at lower temperatures.

[0044] In a specific implementation, a first circulating pump 6 is provided on the heat recovery circuit and the electrolyte preheating circuit, which is located at the inlet end of the first coil 20.

[0045] In a specific embodiment, the surface of the first coil 20 is provided with insulating material.

[0046] As a preferred embodiment, the hot water storage tank 13 is connected to the heat user 22 to form a heating circuit, thereby recovering the waste heat of the flow battery system for heating the user side. Specifically, the heating circuit includes a water supply pipe 17 and a water return pipe 14. The water supply pipe 17 is equipped with a hot water valve 16, and the water return pipe 14 is equipped with a water return pump 15.

[0047] The flow battery system in this embodiment is a common type, including zinc-bromine flow batteries. Its structure includes a flow battery 4, an electrolyte storage tank 1, and an electrolyte pump 3. The electrolyte storage tank 1 includes a cathode electrolyte storage tank and an anode electrolyte storage tank. The anode electrolyte storage tank is connected to the anode of the flow battery 4 to form an anolyte circuit, and the cathode electrolyte storage tank is connected to the cathode of the flow battery 4 to form a cathode electrolyte circuit. Electrolyte pumps 3 are installed on both the anolyte circuit and the cathode electrolyte circuit. During the charging and discharging process of the flow battery 4, the temperature in the cathode and anode electrolyte storage tanks gradually increases.

[0048] As a preferred embodiment, the first coil 20 includes two coil units connected in series, with the two coil units located in the cathode electrolyte storage tank and the anode electrolyte storage tank, respectively.

[0049] This embodiment of the high-efficiency flow battery system based on heat recovery combines a heat pump with the flow battery system. It recovers the heat from the electrolyte during the operation of the flow battery system for use in the heat pump cycle, and uses the heat generated by the heat pump cycle for the cold start of the flow battery system. The specific operating mode is as follows:

[0050] (1) When the flow battery system is working normally, if the electrolyte temperature in the electrolyte storage tank 1 exceeds the first set value (e.g., 35°C), then the a and c ports of the first three-way valve 8 are connected, and the b port is closed, starting the second heat pump cycle. The a and b ports of the second three-way valve 5 are connected, and the c port is closed; the a and b ports of the third three-way valve 2 are connected, and the c port is closed, starting the first circulation pump 6 and connecting the heat recovery circuit. The second circulation pump 18 is started and connecting the heat storage circuit. After passing through the throttling valve 10, the heat pump working fluid (refrigerant) undergoes its first evaporation and heat absorption at the evaporator 9, exchanging heat with the external heat exchange medium to form low-temperature, low-pressure gaseous vapor. Then, in the secondary evaporation heat exchanger 7, it exchanges heat with the heat recovery loop, absorbing heat from the electrolyte in the electrolyte storage tank 1 to further evaporate and form superheated steam (i.e., the steam temperature is higher than the saturation temperature at the same pressure). This superheated steam is then pressurized and heated by the compressor 12, transforming it into a high-temperature, high-pressure state. Next, it exchanges heat with the heat storage loop in the condenser 11, releasing heat to the hot water storage tank 13. The heat-released working fluid then passes through the throttling valve 10 again for a second heat pump cycle. Under this operating condition, the system not only recovers the waste heat generated by the electrolyte for use in the heat pump cycle but also stores the heat generated by the heat pump operation in the hot water storage tank 13, realizing the recovery and reuse of waste heat from the flow battery system.

[0051] When the electrolyte temperature in the electrolyte storage tank 1 is lower than the second set value (e.g., 20°C), the first circulation pump 6 is shut down, the c and b ports of the first three-way valve 8 are connected, the a port is closed, the second heat pump cycle is stopped, and the system switches to the first heat pump cycle. After passing through the throttling valve 10, the heat pump working fluid (refrigerant) undergoes a single evaporation and heat absorption process at the evaporator 9 with the external heat exchange medium, forming a low-temperature, low-pressure gaseous vapor. This vapor is then increased in pressure and temperature by the compressor 12, transforming it into a high-temperature, high-pressure state. Next, it exchanges heat with the heat storage circuit in the condenser 11, releasing heat to the hot water storage tank 13. The heat pump working fluid, after releasing heat, passes through the throttling valve 10 again for the first heat pump cycle. Under this condition, the system only stores the heat generated by the heat pump operation in the hot water storage tank 13 through the heat storage circuit.

[0052] Specifically, if there is a certain water loss in the heat storage circuit during long-term operation, water can be replenished to the circuit through the water replenishment pipe 19.

[0053] Specifically, in the second heat pump cycle, the heat exchange medium on the heat exchange medium side of the evaporator 9 can be air, and the temperature of the air source can be the ambient temperature; when the heat exchange medium on the heat exchange medium side (i.e., the heat recovery loop) of the secondary evaporator heat exchanger 7 is water, its operating temperature range is greater than 5℃, and when the heat exchange medium is ethylene glycol, its operating temperature range is greater than -25℃.

[0054] (2) When the flow battery system needs to be started in a low-temperature environment (electrolyte temperature is usually less than 5°C), the heat pump starts the first heat pump cycle, and the a and c ports of the second three-way valve 5 are connected while the b port is closed. The a and c ports of the third three-way valve 2 are connected while the b port is closed. The first circulation pump 6 is started, and the electrolyte preheating circuit is connected. The water or ethylene glycol heat exchange medium in the electrolyte preheating circuit exchanges heat with the hot water in the hot water storage tank 13, absorbing the heat from the hot water to heat the electrolyte in the electrolyte storage tank 1 until the electrolyte temperature reaches the third set temperature (e.g., 8°C). The flow battery system can then start and operate normally. Then, the first circulation pump 6 is turned off to complete the electrolyte preheating. Under this condition, the system stores the heat generated by the heat pump operation in the hot water storage tank 13 through the heat storage circuit and uses it for electrolyte preheating.

[0055] (3) The hot water storage tank 13 supplies heat to the heat user 22 through the heating circuit. Specifically, the hot water valve 16 on the return water pump 15 and the supply water pipe 17 is turned on to connect the heating circuit and provide hot water to the heat user 22. After the hot water releases heat to the heat user 22, it returns to the hot water storage tank 13 through the return water pipe 14 to absorb heat again, forming a cycle.

[0056] (4) After the flow battery system is shut down, the second and third three-way valves are shut off, and the heat pump can work independently under the first heat pump cycle.

[0057] For the first and second heat pump cycles, the medium circulation paths in the heat recovery circuit, the electrolyte preheating circuit, the heat storage circuit, and the heating circuit mentioned above, please refer to [link / reference]. Figure 1 The corresponding arrow direction.

[0058] In summary, this invention employs a heat pump system with two heat pump cycles, combined with a flow battery system and a hot water storage tank, to construct a heat recovery loop, an electrolyte preheating loop, and a heat storage loop. By switching between the two heat pump cycles and between the electrolyte preheating loop and the heat storage loop, it achieves the recovery of waste heat from the electrolyte during normal operation of the flow battery system, preheating of the electrolyte during cold starts, and supplies the additional heat generated by the system to heat users. This meets the application requirements of the flow battery system under different scenarios and operating conditions, improving the thermal efficiency of the flow battery system and the overall energy utilization rate of the system.

[0059] It will be understood by those skilled in the art that the above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A high-efficiency flow battery system based on heat recovery, characterized in that, Including flow battery systems, heat pumps and hot water storage tanks (13); The heat pump includes a condenser (11), a throttle valve (10), an evaporator (9), a secondary evaporation heat exchanger (7), and a compressor (12). The condenser (11), throttle valve (10), evaporator (9), and compressor (12) are connected in sequence on the refrigerant side to form a first heat pump cycle. The condenser (11), throttle valve (10), evaporator (9), secondary evaporation heat exchanger (7), and compressor (12) are connected in sequence on the refrigerant side to form a second heat pump cycle. The refrigerant side outlet of the evaporator (9), the refrigerant side inlet of the secondary evaporation heat exchanger (7), and the inlet of the compressor (12) are connected by a first three-way valve (8) to realize the switching between the two heat pump cycles. The hot water storage tank (13) is connected to the heat exchange medium side of the condenser (11) to form a heat storage circuit; The electrolyte storage tank (1) of the flow battery system is provided with a first coil (20), which is connected to the heat exchange medium side of the secondary evaporation heat exchanger (7) to form a heat recovery loop; The hot water storage tank (13) is equipped with a second coil (21), which is connected to the first coil (20) to form an electrolyte preheating circuit; The inlet of the first coil (20), the outlet of the heat exchange medium side of the secondary evaporation heat exchanger (7), and the outlet of the second coil (21) are connected by a second three-way valve (5), and the outlet of the first coil (20), the inlet of the heat exchange medium side of the secondary evaporation heat exchanger (7), and the inlet of the second coil (21) are connected by a third three-way valve (2) to realize the switching between the heat recovery circuit and the electrolyte preheating circuit.

2. In the high-efficiency flow battery system based on heat recovery according to claim 1, the heat exchange medium used in the heat recovery circuit and the electrolyte preheating circuit is water or ethylene glycol.

3. The high-efficiency flow battery system based on heat recovery according to claim 1, characterized in that, The heat recovery circuit and the electrolyte preheating circuit are equipped with a first circulating pump (6), which is located at the inlet end of the first coil (20).

4. In the high-efficiency flow battery system based on heat recovery according to claim 1, the heat exchange medium in the heat storage circuit is water.

5. The high-efficiency flow battery system based on heat recovery according to claim 4, characterized in that, The hot water storage tank (13) is connected to the heat user (22) to form a heating circuit. The heating circuit is equipped with a hot water valve (16) and a return water pump (15).

6. The high-efficiency flow battery system based on heat recovery according to claim 4, characterized in that, The heat storage circuit is also connected to a water supply pipe (19), and the output end of the water supply pipe (19) is connected to the heat exchange medium side inlet of the condenser (11).

7. The high-efficiency flow battery system based on heat recovery according to claim 1 or 4, characterized in that, The heat storage circuit is equipped with a second circulation pump (18), which is located at the heat exchange medium side outlet end of the condenser (11).

8. The high-efficiency flow battery system based on heat recovery according to claim 1, characterized in that, The surface of the first coil (20) is provided with insulating material.

9. The high-efficiency flow battery system based on heat recovery according to claim 1, characterized in that, The electrolyte storage tank (1) includes a cathode electrolyte storage tank and an anode electrolyte storage tank. The first coil (20) includes two coil units connected in series, which are located in the cathode electrolyte storage tank and the anode electrolyte storage tank, respectively.

10. The high-efficiency flow battery system based on heat recovery according to claim 9, characterized in that, The anode electrolyte storage tank is connected to the anode of the flow battery (4) to form an anode circuit, and the cathode electrolyte storage tank is connected to the cathode of the flow battery (4) to form a cathode circuit. Electrolyte pumps (3) are respectively provided on the anode circuit and the cathode circuit.

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