A flow battery cold thermal auxiliary system

Abstract

A flow battery cooling and heating auxiliary system, belonging to the field of flow battery technology, includes a condenser, a receiver, an electronic expansion valve, an evaporator, and a compressor. The condenser outlet is connected to the receiver, the receiver is connected to the electronic expansion valve, the electronic expansion valve is connected to the evaporator, the evaporator is connected to the compressor, and the compressor is connected to the condenser, forming a refrigeration cycle. A bypass is added after the condenser outlet dryer filter, and a Freon pump is installed in the bypass. Another bypass is added after the evaporator, resulting in two paths after the evaporator, one connected to the compressor and the other connected to the condenser inlet. Compared with pure compressor refrigeration, the pump-driven + compressor refrigeration system is more energy-efficient. Under the same cooling capacity, the power consumption of the pump is about 10% of that of the compressor. The COP of compressor refrigeration is generally above 3, while the COP of pump-driven phase change natural cooling is above 20.

Description

Technical Field

[0001] This invention belongs to the field of flow battery technology, and specifically relates to a flow battery cooling and heating auxiliary system. Background Technology

[0002] In a vanadium redox flow battery system, the electrolyte acts as a medium, transferring the heat released by the battery to the flow battery's cooling and heating auxiliary system. Typically, the electrolyte operating temperature is required to be below 35-45°C. Traditionally, a compressor-based refrigeration cycle is used to cool the electrolyte.

[0003] The compressor refrigeration cycle utilizes Freon refrigerant for energy transfer. Freon is in a gas-liquid two-phase state at the evaporator inlet. After absorbing heat from the electrolyte in the evaporator, it becomes a superheated gaseous refrigerant and enters the compressor. The compressor compresses the low-temperature, low-pressure gaseous refrigerant into a high-temperature, high-pressure refrigerant gas, which then enters the condenser. In the condenser, the heat absorbed by the refrigerant in the evaporator is released to the atmosphere or recovered for use in domestic water systems. The refrigerant at the condenser outlet is a subcooled liquid refrigerant. After being throttled by the expansion valve, it transforms from a high-temperature, high-pressure liquid refrigerant into a gas-liquid two-phase refrigerant before reaching the evaporator inlet, completing one refrigeration cycle. During the operation of the auxiliary cooling and heating system, the refrigerant remains in this refrigeration cycle throughout this stage.

[0004] According to the second law of thermodynamics, heat cannot spontaneously transfer from a low-temperature object to a high-temperature object. Therefore, the refrigeration cycle completes the heat conversion at the expense of the compressor's energy consumption.

[0005] Deficiencies of existing technology: 1. According to the second law of thermodynamics, the compressor refrigeration system completes the energy conversion by consuming the energy of the compressor. The compressor consumes a lot of energy, which increases the self-power consumption of the flow battery system and reduces the energy efficiency of the battery system.

[0006] 2. In winter, in areas with low outdoor temperatures, the refrigerant remains in liquid form in the compressor after shutdown. When the compressor is restarted, there is a risk of liquid slugging, and the compressor oil has reduced fluidity, which may damage the compressor.

[0007] 3. When an outdoor refrigeration unit is running with two evaporators simultaneously, the impact of pipeline resistance or expansion valve opening is relatively large, making it difficult to ensure that the cooling capacity of the two evaporators is consistent. Therefore, during the operation of the refrigeration unit, the temperature difference of the electrolyte in the two battery systems gradually increases, affecting the uniformity of the battery systems.

[0008] 4. Some electrolytes require an operating temperature range of 48-55℃. For electrolytes within this temperature range, the optimal evaporation temperature range for the refrigeration system is 30-35℃. Each compressor has a suitable operating range. An evaporation temperature of 30-35℃ exceeds the compressor's operating range, preventing it from operating. Lowering the evaporation temperature to 25℃, where the compressor can operate, will reduce the overall energy efficiency of the refrigeration system. Summary of the Invention

[0009] To address the aforementioned problems, this invention proposes a flow battery cooling and heating auxiliary system, comprising a condenser, a receiver, an electronic expansion valve, an evaporator, and a compressor. The condenser outlet is connected to the receiver, the receiver is connected to the electronic expansion valve, the electronic expansion valve is connected to the evaporator, the evaporator is connected to the compressor, and the compressor is connected to the condenser, forming a refrigeration cycle. A bypass is added after the condenser outlet dryer filter, and a Freon pump is installed in the bypass. Another bypass is added after the evaporator, resulting in two bypasses after the evaporator, one of which is connected to the compressor, and the other is connected to the condenser inlet.

[0010] Furthermore, the refrigerant outlet of the condenser is directly connected to the liquid receiver. The subcooled liquid refrigerant condensed by the condenser first enters the liquid receiver for temporary storage and gas-liquid separation, ensuring that the refrigerant entering the expansion valve is pure liquid.

[0011] Furthermore, the outlet of the liquid receiver is connected to the inlet of the electronic expansion valve (EEV). The temporarily stored subcooled liquid refrigerant is throttled and depressurized by the electronic expansion valve, transforming into a gas-liquid two-phase refrigerant to prepare for subsequent heat absorption.

[0012] Furthermore, the outlet end of the electronic expansion valve is connected to the inlet end of the evaporator, and the gas-liquid two-phase refrigerant absorbs heat from the electrolyte of the liquid flow battery in the evaporator and is transformed into a superheated gaseous refrigerant.

[0013] Furthermore, the outlet end of the evaporator is connected to the compressor inlet.

[0014] When the compressor refrigeration mode is used, the superheated gaseous refrigerant directly enters the compressor, is compressed by the compressor into a high-temperature and high-pressure gaseous refrigerant, and is then delivered to the condenser inlet. When the pump-driven refrigeration mode is used, the Freon pump draws the subcooled liquid refrigerant from the condenser outlet and delivers it to the evaporator inlet through a bypass line. The gas-liquid two-phase refrigerant at the evaporator outlet flows directly back to the condenser inlet through another bypass line.

[0015] Furthermore, the outlet end of the compressor is connected to the inlet end of the condenser. After the high-temperature and high-pressure gaseous refrigerant enters the condenser, it releases heat by exchanging heat with the external environment and re-condenses into a subcooled liquid refrigerant, completing one refrigeration cycle.

[0016] Furthermore, the system is also equipped with a control device, which is electrically connected to the electronic expansion valve, the Freon pump, and the compressor respectively. This control device is used to control the opening degree of the electronic expansion valve, the start and stop of the Freon pump, and the operating status of the compressor, so as to realize the automatic adjustment and precise temperature control of the entire flow battery cooling and heating auxiliary system according to the actual working conditions of the flow battery.

[0017] Furthermore, the system also includes a temperature control module and a fluid circulation device. The temperature control module maintains the optimal operating state of the flow battery by precisely adjusting the temperature of the working medium, while the fluid circulation device is responsible for uniformly delivering the temperature-regulated working medium to various parts of the battery stack to ensure the uniformity of temperature distribution throughout the system.

[0018] Furthermore, the system adds a Freon pump refrigeration circuit. When the ambient temperature is relatively low, the electrolyte can be cooled by relying solely on the Freon pump without the need for a compressor. When the ambient temperature is higher than 22°C, the Freon pump is still used to cool the electrolyte first. When the cooling capacity provided by the Freon pump cannot meet the cooling requirements of the electrolyte, and the electrolyte temperature rises to the preset temperature, the Freon pump is turned off and the compressor is turned on for refrigeration. When the electrolyte temperature drops to the preset temperature, the compressor is turned off and the Freon pump is turned on.

[0019] Furthermore, when using a Freon pump cycle, the refrigerant directly enters the condenser from the evaporator outlet to dissipate the absorbed heat, without passing through the compressor; the refrigerant from the condenser outlet is pressurized by the Freon pump before entering the evaporator, instead of directly entering the evaporator, and the compressor cycle is consistent with the traditional compressor refrigeration cycle. Furthermore, to ensure the consistency of the electrolyte temperature at both ends, the opening of the expansion valve in the system is adjusted in real time based on the feedback of the electrolyte temperature at both ends, thereby adjusting the refrigerant flow rate and thus adjusting the cooling capacity at both ends, so that the temperature consistency at both ends approaches uniformity.

[0020] The beneficial effects of this invention are as follows: 1. Compared with pure compressor refrigeration, pump-driven + compressor refrigeration system is more energy-efficient. Under the same refrigeration capacity, the power consumption of the pump is about 10% of that of the compressor. The energy efficiency ratio (COP) of compressor refrigeration is generally above 3, while the energy efficiency ratio (COP) of pump-driven phase change natural cooling is above 20.

[0021] 2. In winter, when the outdoor temperature is low, the electrolyte can be cooled by pump alone. In addition to being more energy-efficient than the compressor system, it can also prevent the compressor from being damaged by liquid slugging or poor oil flow.

[0022] 3. By monitoring and providing feedback on the electrolyte temperature, the flow rate of the expansion valve can be adjusted to make the temperatures at both ends nearly identical, resulting in good temperature consistency.

[0023] 4. For applications requiring high electrolyte temperatures, the Freon pump refrigeration cycle offers higher efficiency and can meet refrigeration needs across all operating conditions. Compressor-based refrigeration systems, on the other hand, suffer from low evaporation temperatures, high energy consumption, and low efficiency. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the cooling and heating auxiliary system of the flow battery of the present invention. Detailed Implementation

[0025] Example 1 To make the technical means and objectives of this invention easier to understand, the invention is further described below in conjunction with specific embodiments, such as a flow battery cooling and heating auxiliary system. Figure 1 As shown, the system includes a condenser, a receiver, an electronic expansion valve, an evaporator, and a compressor. The condenser outlet is connected to the receiver, the receiver is connected to the electronic expansion valve, the electronic expansion valve is connected to the evaporator, the evaporator is connected to the compressor, and the compressor is connected to the condenser, forming a refrigeration cycle. A bypass is added after the condenser outlet dryer filter, and a Freon pump is installed in the bypass. Another bypass is added after the evaporator, making the system two paths after the evaporator. One path is connected to the compressor, and the other path is connected to the condenser inlet.

[0026] The refrigerant outlet of the condenser is directly connected to the liquid receiver. The subcooled liquid refrigerant condensed by the condenser first enters the liquid receiver for temporary storage and gas-liquid separation, ensuring that the refrigerant entering the expansion valve is pure liquid.

[0027] The outlet of the liquid receiver is connected to the inlet of the electronic expansion valve (EEV). The temporarily stored subcooled liquid refrigerant is throttled and depressurized by the electronic expansion valve, transforming into a gas-liquid two-phase refrigerant to prepare for subsequent heat absorption.

[0028] The outlet of the electronic expansion valve is connected to the inlet of the evaporator. The gas-liquid two-phase refrigerant absorbs heat from the electrolyte of the liquid flow battery in the evaporator and is transformed into a superheated gaseous refrigerant.

[0029] The evaporator outlet is connected to the compressor inlet. In compressor refrigeration mode, the superheated gaseous refrigerant directly enters the compressor, where it is compressed into a high-temperature, high-pressure gaseous refrigerant before being delivered to the condenser inlet. When the pump-driven refrigeration mode is used, the Freon pump draws the subcooled liquid refrigerant from the condenser outlet and delivers it to the evaporator inlet through a bypass line. The gas-liquid two-phase refrigerant at the evaporator outlet flows directly back to the condenser inlet through another bypass line.

[0030] The compressor's outlet is connected to the condenser's inlet. After the high-temperature, high-pressure gaseous refrigerant enters the condenser, it releases heat through heat exchange with the external environment and re-condenses into a subcooled liquid refrigerant, completing one refrigeration cycle.

[0031] The system also includes a control device that is electrically connected to the electronic expansion valve, the Freon pump, and the compressor. This control device controls the opening degree of the electronic expansion valve, the start and stop of the Freon pump, and the operating status of the compressor, so as to enable the entire flow battery cooling and heating auxiliary system to automatically adjust and precisely control the temperature according to the actual working conditions of the flow battery.

[0032] The system also includes a temperature control module and a fluid circulation device. The temperature control module maintains the optimal operating state of the flow battery by precisely adjusting the temperature of the working medium, while the fluid circulation device is responsible for uniformly delivering the temperature-regulated working medium to various parts of the battery stack to ensure the uniformity of temperature distribution throughout the system.

[0033] When the electrolyte temperature is within the suitable range for pump-driven refrigeration, the Freon pump starts, drawing subcooled liquid refrigerant from the condenser outlet and directly delivering it to the evaporator inlet via a bypass. At this point, the refrigerant does not pass through the compressor. After entering the evaporator, the refrigerant absorbs heat from the electrolyte and turns into a gaseous state. The gaseous refrigerant then returns to the condenser inlet through the evaporator outlet bypass, completing one pump-driven refrigeration cycle.

[0034] When the electrolyte temperature exceeds the suitable range for pump-driven refrigeration or when faster cooling is required, the compressor and Freon pump operate simultaneously. The compressor compresses the low-temperature, low-pressure gaseous refrigerant into a high-temperature, high-pressure gaseous refrigerant, which is then sent to the condenser. The Freon pump assists by delivering a portion of the subcooled liquid refrigerant to the evaporator inlet. Together, they work to improve refrigeration efficiency.

[0035] The system monitors the electrolyte temperature in real time using a temperature sensor and feeds the data back to the control system. When the temperature approaches the upper limit of the set range, the control system increases the flow rate of the Freon pump or starts the compressor; when the temperature approaches the lower limit of the set range, the control system reduces the flow rate of the Freon pump or shuts it down, relying solely on natural cooling to maintain the temperature. This dynamic adjustment ensures that the electrolyte temperature is always within the optimal operating range.

[0036] In a multi-evaporator parallel system, each evaporator outlet is equipped with a temperature sensor and an expansion valve. The control system independently adjusts the opening of the corresponding expansion valve based on the outlet temperature of each evaporator, ensuring that the refrigerant flow rate into each evaporator matches the heat load. When the load on a particular evaporator increases, its outlet temperature rises, and the control system increases the opening of the corresponding expansion valve, increasing the refrigerant flow rate; conversely, it decreases the opening. Through this distributed control, the outlet temperatures of all evaporators are made closer to uniform, ensuring the homogeneity of the battery system.

[0037] Example 2 Since the power consumption of the Freon pump is much less than that of the compressor, a bypass is added after the dryer filter at the condenser outlet, based on the traditional compressor refrigeration cycle. The Freon pump is installed in the bypass. Another bypass is added at the rear end of the evaporator outlet, connected in parallel with the compressor. The other end of the bypass is connected to the condenser inlet.

[0038] This auxiliary cooling system adds a Freon pump refrigeration circuit. When the ambient temperature is relatively low (typically below 22°C), the Freon pump alone can cool the electrolyte without the need for a compressor. When the ambient temperature is above 22°C, the Freon pump is still used to cool the electrolyte initially. When the cooling capacity provided by the Freon pump is insufficient to meet the electrolyte's cooling requirements, and the electrolyte temperature rises to the preset temperature, the Freon pump is turned off and the compressor is activated for refrigeration. When the electrolyte temperature drops to the preset temperature, the compressor is turned off and the Freon pump is activated.

[0039] When using a Freon pump cycle, the refrigerant enters the condenser directly from the evaporator outlet to dissipate the absorbed heat, bypassing the compressor. The refrigerant exiting the condenser outlet is pressurized by the Freon pump before entering the evaporator, not directly. The compressor cycle is consistent with a traditional compressor refrigeration cycle.

[0040] Furthermore, to ensure the consistency of the electrolyte temperature at both ends, the opening of the expansion valve in the system is adjusted in real time based on the feedback of the electrolyte temperature at both ends, thereby adjusting the refrigerant flow rate and thus adjusting the cooling capacity at both ends, so that the temperature consistency at both ends approaches uniformity.

[0041] This high-efficiency cooling system is used in our company's mixed-acid battery system. The actual ambient temperature at the test site was between 10 and 40°C. The heat exchange system consisted of a 130kW outdoor unit driving two 65kW evaporators simultaneously. We first tested the system energy consumption using a conventional compressor refrigeration system, and then conducted a comparative test using a pump + compressor refrigeration system. The following conclusions were drawn: 1. Pump + compressor refrigeration system is more energy-efficient 15℃ low ambient temperature conditions a) Pump + compressor refrigeration system Cooling capacity: 150kW, total power: 4.59kW, COP: 32.68 b. Conventional compressor refrigeration system Cooling capacity: 138kW, Total power: 10.02kW, COP: 13.7 35℃ high ambient temperature conditions a) Pump + compressor refrigeration system Cooling capacity: 136kW, total power: 10.3kW, COP: 13.2 b. Conventional compressor refrigeration system Cooling capacity: 153kW, total power: 28.72kW, COP: 5.33 2. In winter, projects in regions like Jilin and Heilongjiang experience very low outdoor temperatures. For conventional compressor refrigeration systems, heating wires are needed to heat the oil separator and the compressor itself, converting the liquid refrigerant inside the compressor into a gaseous state to prevent liquid slugging. Heating the oil separator also increases the fluidity of the compressor oil, preventing excessive viscosity and reduced fluidity at low temperatures, which would affect compressor lubrication. Despite these additional steps, compressor damage is still possible in low-temperature environments.

[0042] The pump + compressor refrigeration system can meet the electrolyte heat release requirements using only a Freon pump at low temperatures. With Freon pumps, there's no need to consider liquid slugging or other issues at low temperatures, making them more convenient to use and reducing the possibility of damage.

[0043] 3. The expansion valve opening is adjusted according to the final electrolyte temperature using the flow battery cooling and heating auxiliary control system. For example, in a project using two sets of equipment, one of which uses the flow battery cooling and heating auxiliary control system, the electrolyte temperature difference between the A and B tanks is 2℃. With the flow battery cooling and heating auxiliary control system, there is initially a 1℃ temperature difference. As the chiller operates, the expansion valve dynamically adjusts its opening according to the electrolyte temperature, gradually reducing the flow rate in the lower-temperature B tank while increasing the opening of the expansion valve in the A tank, until the temperatures of the A and B tanks eventually become closer to the same.

[0044] 4. A project uses electrolyte at 48-55℃. Comparative tests were conducted using a Freon pump + compressor refrigeration system and a traditional compressor refrigeration system. For a Freon pump + compressor refrigeration system, the Freon pump alone can meet the cooling requirements when the ambient temperature is below 35℃. When the ambient temperature exceeds 35℃, short-term compressor startup can also meet the requirements, minimizing energy consumption. For a pure compressor refrigeration cycle, the compressor's operating power is inherently higher than that of the pump system. Furthermore, due to compressor limitations, although the electrolyte requires a temperature rise, the evaporation temperature cannot be set too high, otherwise the compressor will be damaged due to overheating, resulting in lower efficiency. At an ambient temperature of 35℃ a) Pump + compressor refrigeration system Cooling capacity: 70kW, total power: 4.9kW, COP: 14.3 b. Conventional compressor refrigeration system Cooling capacity: 72kW, total power: 18.9kW, COP: 3.8.

[0045] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A flow battery cooling and heating auxiliary system, characterized in that, It includes a condenser, a receiver, an electronic expansion valve, an evaporator, and a compressor. The condenser outlet is connected to the receiver, the receiver is connected to the electronic expansion valve, the electronic expansion valve is connected to the evaporator, the evaporator is connected to the compressor, and the compressor is connected to the condenser, forming a refrigeration cycle. A bypass is added after the condenser outlet dryer filter, and a Freon pump is installed in the bypass. Another bypass is added after the evaporator, so the evaporator becomes two paths, one of which is connected to the compressor and the other is connected to the condenser inlet.

2. The flow battery cooling and heating auxiliary system as described in claim 1, characterized in that, The refrigerant outlet of the condenser is directly connected to the liquid receiver. The subcooled liquid refrigerant condensed by the condenser first enters the liquid receiver for temporary storage and gas-liquid separation, ensuring that the refrigerant entering the expansion valve is pure liquid.

3. The flow battery cooling and heating auxiliary system as described in claim 2, characterized in that, The outlet of the liquid receiver is connected to the inlet of the electronic expansion valve (EEV). The temporarily stored subcooled liquid refrigerant is throttled and depressurized by the electronic expansion valve, transforming into a gas-liquid two-phase refrigerant to prepare for subsequent heat absorption.

4. The flow battery cooling and heating auxiliary system as described in claim 3, characterized in that, The outlet of the electronic expansion valve is connected to the inlet of the evaporator. The gas-liquid two-phase refrigerant absorbs heat from the electrolyte of the liquid flow battery in the evaporator and is transformed into a superheated gaseous refrigerant.

5. The flow battery cooling and heating auxiliary system as described in claim 4, characterized in that, The outlet of the evaporator is connected to the compressor inlet; when the compressor refrigeration mode is used, the superheated gaseous refrigerant directly enters the compressor, is compressed by the compressor into a high-temperature and high-pressure gaseous refrigerant, and is then delivered to the condenser inlet. When the pump-driven refrigeration mode is used, the Freon pump draws the subcooled liquid refrigerant from the condenser outlet and delivers it to the evaporator inlet through a bypass line. The gas-liquid two-phase refrigerant at the evaporator outlet flows directly back to the condenser inlet through another bypass line.

6. The flow battery cooling and heating auxiliary system as described in claim 5, characterized in that, The compressor's outlet is connected to the condenser's inlet. After the high-temperature, high-pressure gaseous refrigerant enters the condenser, it releases heat through heat exchange with the external environment and re-condenses into a subcooled liquid refrigerant, completing one refrigeration cycle.

7. The flow battery cooling and heating auxiliary system as described in claim 6, characterized in that, The system is also equipped with a control device, which is electrically connected to the electronic expansion valve, the Freon pump, and the compressor. This control device is used to control the opening degree of the electronic expansion valve, the start and stop of the Freon pump, and the operating status of the compressor, so as to realize the automatic adjustment and precise temperature control of the entire flow battery cooling and heating auxiliary system according to the actual working conditions of the flow battery.

8. The flow battery cooling and heating auxiliary system as described in claim 7, characterized in that, The system also includes a temperature control module and a fluid circulation device. The temperature control module maintains the optimal operating state of the flow battery by precisely adjusting the temperature of the working medium, while the fluid circulation device is responsible for uniformly delivering the temperature-regulated working medium to various parts of the battery stack to ensure the uniformity of temperature distribution throughout the system.

9. The flow battery cooling and heating auxiliary system as described in claim 8, characterized in that, The system adds a Freon pump refrigeration circuit. When the ambient temperature is low, the Freon pump alone can cool the electrolyte without the need for a compressor. When the ambient temperature is higher than 22°C, the Freon pump is still used to cool the electrolyte first. When the cooling capacity provided by the Freon pump cannot meet the cooling requirements of the electrolyte, and the electrolyte temperature rises to the preset temperature, the Freon pump is turned off and the compressor is turned on for refrigeration. When the electrolyte temperature drops to the preset temperature, the compressor is turned off and the Freon pump is turned on.

10. The flow battery cooling and heating auxiliary system as described in claim 9, characterized in that, When using a Freon pump cycle, the refrigerant directly enters the condenser from the evaporator outlet to dissipate the absorbed heat, without passing through the compressor; the refrigerant from the condenser outlet is pressurized by the Freon pump before entering the evaporator, instead of directly entering the evaporator, and the compressor cycle is consistent with the traditional compressor refrigeration cycle. Furthermore, to ensure the consistency of the electrolyte temperature at both ends, the opening of the expansion valve in the system is adjusted in real time based on the feedback of the electrolyte temperature at both ends, thereby adjusting the refrigerant flow rate and thus adjusting the cooling capacity at both ends, so that the temperature consistency at both ends approaches uniformity.

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