A submersible liquid-cooled energy storage system and its control method

Abstract

The application provides an immersed liquid-cooled energy storage system and a control method thereof. The liquid-cooled battery cabinet adopts an immersed mode to carry energy storage battery modules, efficiently transfers heat, and ensures stable operation of the energy storage battery device. The refrigerant pipeline of the condenser, the liquid storage tank, and the refrigerant pipeline of the liquid circulating pump constitute a main refrigerant circuit, which is responsible for cooling gaseous refrigerant into liquid refrigerant for recycling. Further, the refrigerant branch A is a small-capacity gas recooling path, which solves the problem of heat exchange efficiency reduction of the condenser after long-term use. Since the gaseous refrigerant entering the gas recooler has passed through the gas-liquid separator, the humidity is low, and the use frequency is relatively low, so impurities and scale are not easy to produce. The gas recooler and the condenser share an external cold source, and the amount of the external cold source can be adjusted through a valve. Through the external cold source, the gas recooler can effectively and slightly reduce the return liquid temperature when the return liquid temperature is high after long-term use. Moreover, the small-capacity recooler is also convenient for the modification of the existing system, and the cost is relatively low.

Description

Technical Field

[0001] This application relates to the field of cooling technology, and in particular to an immersion liquid-cooled energy storage system and its control method. Background Technology

[0002] Immersion liquid cooling technology is a thermal management technology that uses liquid as the heat transfer medium. It utilizes the high heat capacity and heat transfer coefficient of liquid to exchange heat between the low-temperature liquid and the heat dissipation object, thereby achieving the purpose of cooling. It also has good explosion-proof and flame-retardant functions.

[0003] Based on the heat dissipation requirements of energy storage power station applications, immersion liquid cooling thermal management has significant advantages over air cooling and cold plate indirect liquid cooling. It can quickly improve the cooling performance, safety performance and operating efficiency of energy storage systems, and therefore it is gradually being promoted and scaled up in the commercial field.

[0004] In energy storage power station applications, the main components include heat-generating equipment such as energy storage battery devices, energy storage converters, and integrated transformer substations. Energy storage converters and integrated transformer substations have relatively low modularity, and the protection level of critical modules is often insufficient, making it difficult to apply immersion liquid cooling technology for heat dissipation. Since energy storage battery devices have relatively independent battery packs and their protection capabilities can be improved to a sufficient level through various protective measures, current immersion liquid cooling technology in energy storage power stations is mainly applied within the energy storage battery devices themselves, such as energy storage battery cabinets and energy storage battery containers.

[0005] Large-scale energy storage power stations, comprising numerous energy storage battery cabinets, involve a massive engineering project and typically require phased construction. The total capacity of the energy storage batteries is determined before construction begins, along with the corresponding heat exchange capacity for battery cooling. In practice, if a power station is designed with N energy storage battery cabinets and a corresponding heat exchange capacity of 100 NkW, the project owner may want to commercialize the project as soon as M (M < N, especially M < N / 2) battery cabinets are ready to generate a return on investment quickly. The resulting problem is that the immersion liquid cooling system for the battery cabinets, being part of the project infrastructure, includes extensive and complex liquid cooling piping and an external cold source. Unlike the highly modular battery cabinets, it cannot be constructed in phases; it must be built as comprehensively as possible in the early stages of the project. In this scenario, with the liquid cooling system and M energy storage battery cabinets already in place and the project owner hoping to put them into operation ahead of schedule, the M energy storage battery cabinets will have to be cooled by the entire liquid cooling system, which was originally intended to cool N energy storage battery cabinets. This will undoubtedly result in a waste of the liquid cooling system's cooling capacity or a decrease in its cooling efficiency, especially when there is a significant difference between M and N.

[0006] In addition, heat exchangers in liquid cooling systems are prone to accumulating impurities or scale after long-term use, which reduces heat exchange efficiency and fails to meet the cooling requirements of the load. Replacing or cleaning the heat exchanger at this time will incur considerable costs and difficulties. Summary of the Invention

[0007] This application provides an immersion liquid-cooled energy storage system, a control method for the liquid-cooled system, and an energy storage power station, which can address the problem of heat exchangers in liquid-cooled systems easily generating impurities or scale after long-term use, leading to a decrease in heat exchange efficiency at a lower cost.

[0008] In a first aspect, embodiments of this application provide an immersion liquid-cooled energy storage system, comprising: multiple liquid-cooled battery cabinets connected to a liquid refrigerant and including multiple energy storage battery modules submerged therein, generating gaseous refrigerant during phase change heat transfer of the energy storage battery modules; a main refrigerant circuit including a refrigerant pipeline of a condenser, a liquid storage tank, and a liquid circulation pump connected in sequence to connect to and cool the gaseous refrigerant and form the liquid refrigerant; an external cold source circuit including an external cold source pipeline of the condenser connected to an external cold source, used to cool the main refrigerant circuit; and a refrigerant branch A including a gas-liquid separator connected in sequence. A and the refrigerant piping of the gas recooler; the gas-liquid separator A is connected to the refrigerant piping outlet of the condenser, and its liquid outlet is connected to the liquid storage tank; the outlet of the gas recooler is connected to the liquid storage tank, so that the refrigerant branch A collects and drives the uncondensed gaseous refrigerant at the refrigerant piping outlet of the condenser to be condensed again by the gas recooler; wherein, the external cold source piping of the gas recooler is connected to the external cold source, the heat exchange of the gas recooler is less than the design heat exchange of the condenser, and the sum of the design heat exchange of the condenser and the design heat exchange of the gas recooler is not greater than the design heat exchange of the external cold source.

[0009] Secondly, this application provides a control method for a liquid cooling system, used in the aforementioned immersion liquid-cooled energy storage system, comprising: acquiring the return liquid temperature of the liquid-cooled battery cabinet, and controlling the refrigerant branch A to open when the return liquid temperature is higher than a preset return liquid temperature threshold, otherwise controlling the refrigerant branch A to close.

[0010] This application provides an immersion liquid-cooled energy storage system and its control method. The liquid-cooled battery cabinet uses an immersion method to carry the energy storage battery module, efficiently transferring heat and ensuring the stable operation of the energy storage battery device. The refrigerant pipeline of the condenser, the liquid storage tank, and the refrigerant pipeline of the liquid circulation pump constitute the main refrigerant circuit, responsible for cooling the gaseous refrigerant into liquid refrigerant for recycling. Furthermore, refrigerant branch A serves as a small-capacity gas recooling path, solving the problem of decreased heat exchange efficiency of the condenser after prolonged use. Since the gaseous refrigerant entering the gas recooler has passed through a gas-liquid separator, its humidity is low, and its usage frequency is relatively low, thus it is less prone to impurities and scale buildup. The gas recooler shares an external cold source with the condenser, and the amount of external cold source can be adjusted via a valve. This external cold source allows the gas recooler to effectively reduce the return liquid temperature slightly when it is high after prolonged use. Moreover, the small-capacity recooler facilitates the modification of existing systems at a relatively low cost. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this application, 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 this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the structure of an immersion liquid-cooled energy storage system provided in an embodiment of this application;

[0013] Figure 2 This is a schematic diagram of the structure of an immersion liquid-cooled energy storage system provided in another embodiment of this application;

[0014] Figure 3 This is a schematic diagram of the structure of an immersion liquid-cooled energy storage system provided in another embodiment of this application;

[0015] Figure 4 This is a schematic diagram of the structure of an immersion liquid-cooled energy storage system provided in another embodiment of this application. Detailed Implementation

[0016] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0017] The terms "first," "second," "A," "B," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0018] Unless otherwise stated, the term "multiple" means two or more. The character " / " indicates that the preceding and following objects are in an "or" relationship. For example, A / B means: A or B. The term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or, A and B.

[0019] The terms used in this application are for describing embodiments only and are not intended to limit the claims. As used in the description of embodiments and claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Similarly, the term “and / or” as used herein means including one or more of the associated listed elements and all possible combinations thereof. Additionally, when used in this application, the terms “comprise” and its variations “comprises” and / or “comprising” refer to the presence of stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof. Without further limitation, an element defined by the phrase “comprising an…” does not exclude the presence of additional identical elements in the process, method, or apparatus that includes said element.

[0020] In this application, each embodiment focuses on describing the differences from other embodiments, and similar or identical parts between embodiments can be referred to mutually. For methods, products, etc., disclosed in the embodiments, if they correspond to the method section disclosed in the embodiments, then the relevant parts can be referred to the description of the method section.

[0021] Furthermore, the correspondence between refrigerant branch A, refrigerant branch B, gas-liquid separator A, and gas-liquid separator B in the claims of this application and the respective refrigerant branches and gas-liquid separators in the embodiments will be explained first. Refrigerant branch A can be either the second refrigerant branch or the fourth refrigerant branch described below. Refrigerant branch B can be either the third refrigerant branch described below. Gas-liquid separator A can be either the second or the third gas-liquid separator described below. Gas-liquid separator B is the fourth gas-liquid separator described below.

[0022] To make the objectives, technical solutions, and advantages of this application clearer, the following description will be provided in conjunction with the accompanying drawings and specific embodiments.

[0023] Figure 1 This is a schematic diagram of the structure of an immersion liquid-cooled energy storage system provided in an embodiment of this application, as shown below. Figure 1 As shown, it includes: multiple liquid-cooled battery cabinets, a main refrigerant circuit, and an external cold source circuit.

[0024] Multiple liquid-cooled battery cabinets constitute an energy storage battery device. Each liquid-cooled battery cabinet is connected to a liquid refrigerant and is used to submerge the energy storage battery module to generate gaseous refrigerant when the energy storage battery module undergoes phase change heat transfer.

[0025] Among them, the energy storage battery module is an energy storage battery pack. The energy storage battery module generates a lot of heat during operation. If it is not dissipated in time, it will seriously affect the performance and stability of the equipment.

[0026] In this embodiment, the liquid-cooled battery cabinet uses an immersion method to support the energy storage battery modules. Through contact heat conduction, the device can efficiently transfer heat. During the phase change heat transfer process, the liquid refrigerant effectively absorbs the heat generated by the energy storage battery modules and transforms into a gaseous state, ensuring that heat is transferred rapidly and evenly. Therefore, the liquid-cooled battery cabinet not only significantly improves heat dissipation efficiency but also effectively avoids localized overheating of the equipment, ensuring stable operation.

[0027] The main refrigerant circuit is connected to and cools gaseous refrigerant to form liquid refrigerant, and includes, in sequence, the refrigerant piping of condenser 1, liquid storage tank 2, liquid circulation pump 3, and liquid recooler 4.

[0028] An external cold source circuit is used to cool the main refrigerant circuit and includes an external cold source pipeline for the condenser 1 and an external cold source pipeline for the liquid recooler 4, which are connected in parallel to each other and connected to an external cold source. The external cold source pipeline of the liquid recooler 4 is provided with a parallel control valve 5 for controlling whether the external cold source pipeline is connected to an external cold source.

[0029] Both the condenser 1 and the liquid recooler 4 are indirect heat exchangers and each includes a refrigerant pipeline and an external cold source pipeline. The main function of the two pipelines is to allow the refrigerant to exchange heat with the external cold source as it flows through the refrigerant pipeline, causing the gaseous refrigerant to release heat and transform into a liquid state.

[0030] During system operation, the phase change process of the refrigerant follows this pattern: the refrigerant circulates in the main refrigerant loop, exchanges heat with the external cold source in the refrigerant pipelines of condenser 1 and liquid recooler 4, causing the refrigerant to change from a gaseous phase to a liquid phase. This transformation ensures that the refrigerant can efficiently absorb heat from the energy storage battery module when flowing through the liquid-cooled battery cabinet, causing the refrigerant to change from a liquid phase to a gaseous phase.

[0031] The main function of the liquid recooler 4 is to further cool the liquid refrigerant to ensure that it reaches the ideal low temperature state.

[0032] In this embodiment, the main task of the main refrigerant circuit is to introduce gaseous refrigerant into the system and, after a series of processes, convert it into liquid refrigerant, ensuring that it can efficiently absorb the heat of the energy storage battery module when flowing through the liquid-cooled battery cabinet. The main task of the external cold source circuit is to provide cooling capacity to the main refrigerant circuit, which includes the external cold source pipeline of the condenser 1 and the external cold source pipeline of the liquid recooler 4 connected in parallel to the external cold source.

[0033] The external cold source pipeline of the liquid recooler 4 is equipped with a parallel control valve 5. This design allows the system to flexibly adjust the connection of the external cold source according to actual conditions, such as the phased construction of the project or changes in the cooling demand of the energy storage battery device.

[0034] Specifically, for phased construction of energy storage power station projects, if the power station is not yet fully completed, the external cold source piping of condenser 1 can be used first to provide cooling capacity to the main refrigerant circuit. After the entire power station is completed, the external cold source piping of liquid recooler 4 and the external cold source piping of condenser 1 can be adjusted through parallel control valve 5 to provide cooling capacity to the main refrigerant circuit together. The parallel control valve 5 avoids wasting the cooling capacity of the liquid cooling system before the entire power station is completed and ensures the stable operation of the system. Figure 1 The example shown is a single liquid-cooled battery cabinet. In practice, the number of liquid-cooled battery cabinets may vary depending on the progress of the power plant construction.

[0035] To address changes in the cooling demand of the energy storage battery device, when the cooling demand is low and condenser 1 can meet the cooling requirements, the parallel control valve 5 is closed. In this case, the liquid refrigerant flows directly to the liquid recooler 4 without heat exchange, thus maintaining an appropriate external cold source input and avoiding waste of the liquid cooling system's cooling capacity, thereby improving the liquid cooling system's cooling efficiency. Conversely, when the cooling demand of the energy storage battery device increases and condenser 1 cannot meet the cooling requirements, the parallel control valve 5 is opened to increase the external cold source input. This ensures that the gaseous refrigerant can undergo a complete phase change and form a lower-temperature liquid refrigerant that flows back to the liquid-cooled battery cabinet. This prevents the high-temperature liquid refrigerant from undergoing film boiling within the liquid-cooled battery cabinet, which could damage the energy storage battery modules.

[0036] Additionally, it should be noted that in the actual implementation, the sum of the design heat exchange capacity of condenser 1 and liquid recooler 4 does not exceed the design heat exchange capacity of the external cold source. This design principle ensures that the system maintains a stable thermal balance during operation, avoiding system failure due to heat accumulation. At the same time, it facilitates system optimization and upgrades, enabling the system to maintain efficient and stable operation when facing different cooling demands.

[0037] Optionally, the external cold source can be air, water, or other low-temperature fluids. Through heat exchange with these external resources, the external cold source circuit can effectively remove heat from the main refrigerant circuit, thereby maintaining the stable operation of the system.

[0038] In the aforementioned phase change process of the refrigerant, the liquid storage tank 2 acts as a buffer and stabilizes the refrigerant flow, ensuring a stable supply of refrigerant in the system. The liquid circulation pump 3 is responsible for delivering the liquid refrigerant to the liquid recooler 4, further reducing its temperature. Finally, after passing through the refrigerant pipeline of the liquid recooler 4, the liquid refrigerant completes the cooling process, preparing for the next cycle.

[0039] In this embodiment, the energy storage battery modules are supported by an immersion-type liquid-cooled battery cabinet, which efficiently transfers heat and ensures the stable operation of the energy storage battery device. The refrigerant piping of the condenser, the liquid storage tank, the liquid circulation pump, and the refrigerant piping of the liquid recooler constitute the main refrigerant circuit, responsible for cooling the gaseous refrigerant into liquid refrigerant for recycling. The introduction of the liquid recooler for further cooling avoids insufficient cooling efficiency and prevents gaseous refrigerant from entering the liquid-cooled battery cabinet and causing film boiling. Furthermore, the system employs parallel control valves to connect the external cold source piping of the condenser and the liquid recooler to an external cold source. This allows the system to adjust its cooling capacity according to actual conditions, adapting to the phased construction and early commercialization needs of energy storage power station projects, while also ensuring sufficient cooling of the energy storage battery device in later stages, achieving a more efficient and energy-saving cooling effect. The combined heat exchange capacity of the condenser and liquid recooler is strictly controlled within the design heat exchange capacity of the external cold source to ensure the stability and safety of the cooling system during actual operation and to avoid system failure or damage caused by excessive heat exchange.

[0040] In the aforementioned embodiments, under the design principle that the sum of the designed heat exchange capacity of the condenser 1 and the liquid recooler 4 is not greater than the designed heat exchange capacity of the external cold source, the number of condensers 1 and liquid recoolers 4, as well as the heat exchange principle between condensers 1 and liquid recoolers 4, are different.

[0041] In one possible implementation, the design heat exchange of condenser 1 is equal to the design heat exchange of liquid recooler 4, and the sum of the two matches the design heat exchange of the external cold source.

[0042] In this invention, the design heat exchange capacity of condenser 1 and liquid recooler 4 is set to be equal to ensure that their heat handling capabilities are matched during the heat exchange process. When their heat exchange capacities are equal, overheating or undercooling of the refrigerant during circulation can be effectively avoided, thereby ensuring the continuity and stability of the refrigeration process. Furthermore, it should be noted that the matching of the design heat exchange capacity described in this embodiment of the invention does not simply mean that the theoretical heat exchange capacity of the heat exchangers are the same; the actual heat exchange capacity affected by heat exchange efficiency must also be taken into account.

[0043] In terms of system construction, setting the design heat exchange capacity of condenser 1 and liquid recooler 4 to be equal helps simplify the system design and manufacturing process and improves the speed of system construction. Engineers can use this principle to more accurately calculate and select appropriate equipment specifications and parameters, thereby shortening the system commissioning and optimization time and reducing related costs.

[0044] In this embodiment, setting the design heat exchange capacity of condenser 1 and liquid recooler 4 to be equal, and ensuring that their sum matches the design heat exchange capacity of the external cold source, is an efficient and practical system design method. This design not only improves the efficiency and performance of the refrigeration system, but also simplifies the system design and manufacturing process and reduces operating costs.

[0045] In other possible implementations, according to the project construction plan, multiple liquid recoolers 4 are set up, and parallel control valves 5 should be configured on the external cold source pipeline of each liquid recooler 4. According to the specific cooling capacity requirements at different stages of project construction, it is possible to select one or more liquid recooler 4 external cold source pipelines connected in parallel with the external cold source pipeline of condenser 1 and then connected to an external cold source.

[0046] Alternatively, the design heat exchange capacity of condenser 1 and liquid recooler 4 can be set to be equal, or the design heat exchange capacity of liquid recooler 4 can be adaptively determined according to the phased planning of the project construction.

[0047] Figure 2 This is a schematic diagram of the structure of an immersion liquid-cooled energy storage system provided in another embodiment of this application, as shown below. Figure 2 As shown, in Figure 1 Based on the submerged liquid-cooled energy storage system shown, it further includes: a first refrigerant branch, which sequentially includes a first gas-liquid separator 6, a gas storage tank 8, and a gas circulation pump 9, and has a two-way valve 7 located in the first refrigerant branch; the first gas-liquid separator 6 is connected to the refrigerant pipeline outlet of the condenser 1, and the gas circulation pump 9 is connected to the refrigerant pipeline inlet of the condenser 1, so that the first refrigerant branch collects and drives the uncondensed gaseous refrigerant at the refrigerant pipeline outlet of the condenser 1 back to the refrigerant pipeline inlet of the condenser 1 for re-condensation. In this embodiment, the design ventilation rate of the first refrigerant branch is less than the design ventilation rate of the inlet of the condenser 1.

[0048] Among them, compared to Figure 1 The submerged liquid-cooled energy storage system shown uses a first refrigerant branch as a small-capacity return gas path, primarily addressing the limited condensing capacity of condenser 1. In actual operation, to accommodate phased construction of the project, the aforementioned embodiment divides the large-capacity condenser, originally intended for cooling the entire project, into two smaller heat exchangers: condenser 1 and liquid recooler 4. This may result in limited condensing capacity for condenser 1. Especially during the later stages of project construction, a large amount of gaseous refrigerant enters condenser 1, which is insufficient to condense it. While theoretically, the liquid recooler 4, located downstream of the main refrigerant circuit, can compensate for this missing heat exchange, the refrigerant lines of both are connected in series, unlike the parallel connection of their external cooling source lines. This means that some gaseous refrigerant may not be fully condensed due to the limited condensing capacity of condenser 1 and may directly enter the liquid storage tank 2. This not only leads to insufficient system liquid levels but may also cause cavitation in the liquid circulation pump 3. Therefore, the introduction of the first refrigerant branch avoids the problem of cavitation in the liquid circulation pump 3 caused by gaseous refrigerant, ensuring the stable operation of the system.

[0049] In addition, the first refrigerant branch can make full use of the refrigerant's potential heat exchange capacity by collecting and driving the uncondensed gaseous refrigerant to undergo re-condensation. This not only improves the utilization rate of the gas but also increases the liquid storage capacity of the system, thereby enhancing the system's heat exchange efficiency and further improving the performance of the submerged liquid-cooled energy storage system.

[0050] In this embodiment, the introduction of the first refrigerant branch not only solves the problem of limited condensing capacity of condenser 1 due to the configuration of the heat exchangers of the main refrigerant circuit as condenser 1 and liquid recooler 4, which are relatively small heat exchangers, and prevents the risk of insufficient liquid storage in the system and cavitation of liquid circulation pump 3, but also makes full use of the potential heat exchange capacity of the refrigerant and improves the heat exchange efficiency of the system.

[0051] Figure 3 This is a schematic diagram of the structure of an immersion liquid-cooled energy storage system provided in another embodiment of this application, as shown below. Figure 3 As shown, in Figure 1 Based on the submerged liquid-cooled energy storage system shown, it also includes: a second refrigerant branch, which sequentially includes the refrigerant pipelines of the second gas-liquid separator 10 and the gas recooler 12, and has a two-way valve 11 located in the second refrigerant branch; the second gas-liquid separator 10 is connected to the refrigerant pipeline outlet of the condenser 1, and the refrigerant pipeline of the gas recooler 12 is connected to the liquid storage tank 2, so that the second refrigerant branch collects and drives the uncondensed gaseous refrigerant at the refrigerant pipeline outlet of the condenser 1 to be condensed again by the gas recooler 12;

[0052] The gas recooler 12 is connected to an external cold source via an external cold source pipeline. The design heat exchange of the condenser 1, the design heat exchange of the liquid recooler 4, and the design heat exchange of the gas recooler 12 are all matched to the design heat exchange of the external cold source.

[0053] In practical applications, as condenser 1 is used for many years, impurities or scale may be generated in its refrigerant pipeline, causing a decrease in the heat exchange efficiency of condenser 1. The gaseous refrigerant cannot be condensed into a lower-temperature liquid refrigerant after passing through condenser 1. Even if there is a downstream liquid recooler 4, the return liquid temperature may rise after the system has been running for a long time.

[0054] Compared to Figure 1 The submerged liquid-cooled energy storage system shown uses a second refrigerant branch as a small-capacity gas recooling path to address the issue of decreased heat exchange efficiency in condenser 1 after prolonged use. Because the gaseous refrigerant entering the gas recooler 12 has passed through a second gas-liquid separator, its humidity is low, and its usage frequency is relatively low, thus reducing the likelihood of impurities and scale buildup. The gas recooler 12 shares an external cold source with condenser 1 and liquid recooler 4, and the amount of external cold source can be adjusted via a valve similar to a parallel control valve 5. This external cold source allows the gas recooler 12 to effectively reduce the return liquid temperature slightly after prolonged use when the return liquid temperature is high. Furthermore, the small-capacity recooler facilitates retrofitting of existing systems at a low cost.

[0055] The design principle for heat exchange is as follows: the combined heat exchange capacity of condenser 1, liquid recooler 4, and gas recooler 12 is matched with the heat exchange capacity of the external cold source. This design principle ensures that the system maintains a stable thermal balance during operation, avoiding system failure due to heat accumulation.

[0056] In this embodiment, the introduction of the second refrigerant branch solves the problem of performance degradation of condenser 1 after prolonged use and enables fine-tuning of system heat exchange, thereby improving the overall system performance. It is understood that in this application, when addressing the performance degradation of the condenser after prolonged use by introducing the second refrigerant branch, the main refrigerant circuit and the external cold source circuit may not include... Figure 1 The liquid recooler 4 is shown in the figure.

[0057] Figure 4 This is a schematic diagram of the structure of an immersion liquid-cooled energy storage system provided in another embodiment of this application, as shown below. Figure 4 As shown, in Figure 1 Based on the submerged liquid-cooled energy storage system shown, it also includes: a third gas-liquid separator 13, a third refrigerant branch, a fourth refrigerant branch, a first two-way valve 14, a second two-way valve 15, and a three-way valve 17.

[0058] The third gas-liquid separator 13 is connected to the refrigerant pipeline outlet of the condenser 1, and its liquid outlet is connected to the liquid storage tank 2.

[0059] The third refrigerant branch includes a gas storage tank 8 and a gas circulation pump 9 in sequence. The gas storage tank 8 is connected to the gas outlet of the third gas-liquid separator 13, and the gas circulation pump 9 is connected to the refrigerant pipeline inlet of the condenser 1, so that the third refrigerant branch collects and drives the uncondensed gaseous refrigerant at the refrigerant pipeline outlet of the condenser 1 back to the refrigerant pipeline inlet of the condenser 1 for re-condensation.

[0060] The fourth refrigerant branch sequentially includes the refrigerant pipeline of the gas recooler 12 and the fourth gas-liquid separator 16; the refrigerant pipeline of the gas recooler 12 is connected to the gas outlet of the third gas-liquid separator 13, the fourth gas-liquid separator 16 is connected to the gas recooler 12 and its gas outlet is connected to the gas storage tank 8, and its liquid outlet is connected to the liquid storage tank 2, so that the fourth refrigerant branch collects and drives the uncondensed gaseous refrigerant at the outlet of the refrigerant pipeline of the condenser 1 to be condensed again by the gas recooler 12; wherein, the external cold source pipeline of the gas recooler 12 is connected to an external cold source, and the design heat exchange of the condenser 1, the design heat exchange of the liquid recooler 4, and the design heat exchange of the gas recooler 12 are matched with the design heat exchange of the external cold source.

[0061] The first two-way valve 14 and the second two-way valve 15 are respectively located in the third refrigerant branch and the fourth refrigerant branch. The three ports of the three-way valve 17 are respectively connected to the refrigerant pipeline outlet of the condenser 1, the third gas-liquid separator 13 and the liquid storage tank 2.

[0062] In summary, Figure 4 Compared to Figure 1 The submerged liquid-cooled energy storage system shown has a third refrigerant branch added as a small-capacity return gas path, and a fourth refrigerant branch added as a small-capacity gas recooling path.

[0063] The third refrigerant branch is used to address the problem of insufficient liquid level in the system and potential cavitation in the liquid circulation pump 3 caused by gas entering the liquid storage tank 2 before it has fully condensed. Furthermore, this fully utilizes the refrigerant's potential heat exchange capacity, improves gas utilization and liquid level, and enhances the system's heat exchange efficiency. Understandably, the third refrigerant branch is related to... Figure 2 The first refrigerant branch in the immersion liquid-cooled energy storage system shown has the same function.

[0064] The fourth refrigerant branch is used to address the issue of decreased heat exchange efficiency in condenser 1 after prolonged use. The gas recooler 12 shares an external cold source with condenser 1 and liquid recooler 4, and the amount of external cold source can be adjusted via a valve similar to parallel control valve 5. This external cold source allows the gas recooler 12 to effectively and slightly reduce the return liquid temperature when it is high after prolonged use. Furthermore, the small capacity of the recooler facilitates retrofitting of the existing system. Understandably, the fourth refrigerant branch... Figure 3 The second refrigerant branch in the immersion liquid-cooled energy storage system shown has a basically the same function, but in addition, the fourth refrigerant branch in this embodiment has other functions.

[0065] Specifically Figure 2 The immersion liquid-cooled energy storage system shown utilizes the first refrigerant branch to form a return gas passage. Although it does reduce the humidity of the gaseous refrigerant entering the condenser 1, making it easier to condense into liquid and thus increase the liquid volume in the storage tank 2, the condenser 1 is designed with limited heat exchange capacity. After circulating gaseous refrigerant with a certain temperature that has not been further cooled by the external cold source into the condenser 1, the heat exchange temperature difference between the refrigerant pipeline and the external cold source pipeline of the condenser 1 will decrease, thereby reducing the heat exchange efficiency of the condenser 1. As a result, although it can increase the liquid volume in the storage tank 2 and reduce cavitation on the liquid circulation pump 3, it may actually lead to an increase in the return liquid temperature.

[0066] To address this, a fourth refrigerant branch with a gas recooler 12 and a fourth gas-liquid separator 16 is introduced. The fourth gas-liquid separator 16 is connected to the gas storage tank 8 and the liquid storage tank 2. This not only functions as a second refrigerant branch to solve the problem of long-term use of the condenser 1, but also allows some or all of the gaseous refrigerant to be cooled by an external cold source via the gas recooler 12 before entering the gas storage tank 8. This reduces the decrease in the heat exchange temperature difference of the condenser 1 and avoids the problems of reduced heat exchange efficiency and increased terminal liquid return temperature caused by only introducing the first or third refrigerant branch into the condenser 1. Similarly, the gas recooler 12 and the fourth gas-liquid separator 16 themselves can increase the liquid level in the liquid storage tank 2, reduce cavitation, and lower the liquid return temperature.

[0067] It can be seen that, compared with setting only the first refrigerant branch or only the second refrigerant branch, the combination of the fourth refrigerant branch and the third refrigerant branch in this embodiment can achieve better results. In this case, the fourth refrigerant branch also has the effect of improving the heat exchange efficiency of the condenser 1 compared with the second refrigerant branch.

[0068] In one possible implementation, the design heat exchange of condenser 1 is equal to the design heat exchange of liquid recooler 4, and the heat exchange of gas recooler 12 is less than the design heat exchange of condenser 1 and liquid recooler 4.

[0069] Among them, the heat exchange capacity of the gas recooler 12 is less than the design heat exchange capacity of the condenser 1 and the liquid recooler 4, which can meet the fine-tuning requirements of the system heat exchange capacity and reduce the system construction cost.

[0070] In this embodiment, the introduction of the third refrigerant branch not only solves the problem of limited condensing capacity of condenser 1, preventing insufficient system liquid storage and the risk of cavitation in liquid circulation pump 3, but also fully utilizes the potential heat exchange capacity of the refrigerant, improving the system's heat exchange efficiency. The introduction of the fourth refrigerant branch solves the problem of performance degradation of condenser 1 after prolonged use and addresses the issue of low heat exchange efficiency of condenser 1 when only the third refrigerant branch is introduced, thereby reducing the return liquid temperature, enabling fine-tuning of the system's heat exchange capacity, and improving the overall system performance. The introduction of dual branches enhances the system's adaptability to various operating scenarios, thus improving the system's stable operation.

[0071] The above embodiments illustrate in detail the operating mechanisms of different liquid cooling systems. In the actual control phase, the liquid cooling system is comprehensively regulated based on the load rate of multiple energy storage battery devices, the liquid level of the storage tank 2, and the return temperature of the liquid-cooled battery cabinet. Optionally, the parallel control valve 5, the two-way valve, and the three-way valve 17 are electronic control valves, capable of responding to control commands from the control system.

[0072] An embodiment of this application also provides a control method for an immersion liquid-cooled energy storage system, the method comprising the following steps:

[0073] S501, Obtain the load rate of the at least one liquid-cooled battery cabinet;

[0074] If the load rate is greater than the preset load rate threshold, proceed to step S502; otherwise, proceed to step S503.

[0075] S502, controls the opening of parallel control valve 5;

[0076] S503, controls the parallel control valve 5 to close.

[0077] The load factor is the ratio of the heat dissipation of the current energy storage battery device to the total designed heat exchange of the liquid cooling system. It can be determined simply by the number of energy storage battery modules connected, or by obtaining their operating power in real time.

[0078] In this embodiment, the execution entity of the control method for the submerged liquid-cooled energy storage system is a cloud server or a controller with a physical structure. The above is an illustrative description; the execution entity can also be other types of control devices.

[0079] During implementation, the number of liquid-cooled battery cabinets will vary depending on the different stages of project construction, resulting in different load rates for the liquid cooling system. After project completion, the number of liquid-cooled battery cabinets activated will also vary, leading to different load rates for the liquid cooling system. Furthermore, even with varying numbers of activated liquid-cooled battery cabinets, the heat dissipation may differ depending on the operating environment, further affecting the load rate of the liquid cooling system.

[0080] In this embodiment, the load rate is obtained. When the load rate is less than or equal to a preset load rate threshold, the parallel control valve 5 is closed to avoid wasting the cooling capacity of the liquid cooling system, improve the cooling efficiency of the liquid cooling system, and adapt to the needs of phased construction and early commercialization. When the load rate is greater than the preset load rate threshold, the parallel control valve 5 is opened to avoid insufficient cooling efficiency, thereby preventing gaseous refrigerant from entering the liquid-cooled battery cabinet and causing film boiling, and improving the system's operational stability.

[0081] One possible implementation also includes:

[0082] The liquid level of the storage tank 2 is obtained, and the first or third refrigerant branch is opened when the liquid level is lower than the preset liquid level threshold; otherwise, the first or third refrigerant branch is closed.

[0083] When the liquid level in storage tank 2 is lower than the preset threshold, it indicates that the gaseous refrigerant has not condensed sufficiently. If the gaseous refrigerant enters the liquid circulation pump 3, it will cause cavitation in the liquid circulation pump 3. Figure 2 The submerged liquid-cooled energy storage system shown controls the opening of the first refrigerant branch. Figure 3 In the submerged liquid-cooled energy storage system shown, the third refrigerant branch is opened to collect and drive the uncondensed gaseous refrigerant from the refrigerant pipeline outlet of condenser 1 back to the refrigerant pipeline inlet of condenser 1 for re-condensation.

[0084] In one possible implementation, the method further includes: acquiring the return liquid temperature of the liquid-cooled battery cabinet, and controlling the second or fourth refrigerant branch to open when the return liquid temperature is higher than a preset return liquid temperature threshold, otherwise controlling the second or fourth refrigerant branch to close.

[0085] When the return liquid temperature of the liquid-cooled battery cabinet is higher than the preset return liquid temperature threshold, it indicates that the heat exchange efficiency of condenser 1 is insufficient, or that the heat exchange efficiency of condenser 1 and liquid recooler 4 is insufficient, and the control... Figure 3 The second refrigerant branch shown or Figure 4 The fourth refrigerant branch shown is opened, collecting and driving the uncondensed gaseous refrigerant at the outlet of the refrigerant pipeline of condenser 1 to be condensed again by the gas recooler 12.

[0086] Specifically, when the fourth refrigerant branch is opened, the two-way valve 14 in the third refrigerant branch can be opened to allow some gaseous refrigerant to enter the gas recooler 12, or the two-way valve 14 can be closed to allow all gaseous refrigerant to enter the gas recooler 12 and then return to the condenser 1 via the gas storage tank of the third refrigerant branch. This can be determined based on the degree of increase in the return liquid temperature.

[0087] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0088] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. An immersion liquid-cooled energy storage system, characterized in that, include: Multiple liquid-cooled battery cabinets are connected to liquid refrigerant and include multiple energy storage battery modules submerged within them, and generate gaseous refrigerant when the energy storage battery modules undergo phase change heat transfer. The main refrigerant circuit includes a refrigerant pipeline, a liquid storage tank, and a liquid circulation pump connected in sequence to the condenser, so as to receive and cool the gaseous refrigerant and form the liquid refrigerant; An external cold source circuit, comprising external cold source piping connected to the condenser of an external cold source and used to cool the main refrigerant circuit; and Refrigerant branch A includes a refrigerant line connected in sequence to a gas-liquid separator A and a gas recooler; the gas-liquid separator A is connected to the refrigerant line outlet of the condenser, and its liquid outlet is connected to the liquid storage tank; the outlet of the gas recooler is connected to the liquid storage tank, so that the refrigerant branch A collects and drives the uncondensed gaseous refrigerant at the refrigerant line outlet of the condenser to be condensed again by the gas recooler; The gas recooler is connected to the external cold source via an external cold source. The heat exchange capacity of the gas recooler is less than the design heat exchange capacity of the condenser, and the sum of the design heat exchange capacity of the condenser and the design heat exchange capacity of the gas recooler is not greater than the design heat exchange capacity of the external cold source.

2. The immersion liquid-cooled energy storage system according to claim 1, characterized in that: The main refrigerant circuit also includes the refrigerant piping of the liquid recooler. The refrigerant piping of the condenser, the liquid storage tank, the liquid circulation pump and the refrigerant piping of the liquid recooler are connected in sequence to form the main refrigerant circuit. The external cold source circuit also includes the external cold source pipeline of the liquid recooler, and the external cold source pipeline of the condenser and the external cold source pipeline of the liquid recooler are connected in parallel to the external cold source; The liquid recooler is equipped with a parallel control valve on its external cold source pipeline for controlling whether the external cold source pipeline is connected to the external cold source; the design heat exchange of the condenser, the design heat exchange of the liquid recooler, and the design heat exchange of the gas recooler are combined to match the design heat exchange of the external cold source.

3. The immersion liquid-cooled energy storage system according to claim 2, characterized in that, The design heat exchange capacity of the condenser is equal to the design heat exchange capacity of the liquid recooler; It also includes: refrigerant branch B, which includes a gas storage tank and a gas circulation pump connected in sequence; the gas storage tank is connected to the gas outlet of the gas-liquid separator A, and the gas circulation pump is connected to the refrigerant pipeline inlet of the condenser, so that the refrigerant branch A collects and drives the uncondensed gaseous refrigerant at the refrigerant pipeline outlet of the condenser back to the refrigerant pipeline inlet of the condenser for re-condensation; The design ventilation rate of the refrigerant branch B is less than the design ventilation rate of the condenser inlet.

4. The immersion liquid-cooled energy storage system according to claim 3, characterized in that, Also includes: Gas-liquid separator B, the inlet of which is connected to the gas recooler, the gas outlet of which is connected to the gas storage tank, and the liquid outlet of which is connected to the liquid storage tank.

5. The immersion liquid-cooled energy storage system according to claim 4, characterized in that, It also includes a three-way valve; the three ports of the three-way valve are respectively connected to the refrigerant pipeline outlet of the condenser, the gas-liquid separator A, and the liquid storage tank.

6. A control method for a liquid-cooled energy storage system, used in the submersible liquid-cooled energy storage system of claim 1, characterized in that, include: The return liquid temperature of the liquid-cooled battery cabinet is obtained, and the refrigerant branch A is turned on when the return liquid temperature is higher than the preset return liquid temperature threshold; otherwise, the refrigerant branch A is turned off.

7. The control method for the liquid-cooled energy storage system according to claim 6, characterized in that, The method is used in the immersion liquid-cooled energy storage system of claim 2; and further includes: The load rate of at least one of the liquid-cooled battery cabinets is obtained, and the parallel control valve is opened when the load rate is greater than a preset load rate threshold; otherwise, the parallel control valve is closed.

8. The control method for the liquid-cooled energy storage system according to claim 7, characterized in that: Also includes: The liquid level of the storage tank is obtained, and the refrigerant branch B is opened when the liquid level is lower than a preset liquid level threshold; otherwise, the refrigerant branch B is closed.

9. The control method for the liquid-cooled energy storage system according to claim 8, characterized in that, Also includes: When refrigerant branch A is turned on, the uncondensed gaseous refrigerant is controlled to first pass through the gas recooler of refrigerant branch A, and then return to the condenser through the gas storage tank of refrigerant branch B.

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