A lithium battery energy storage system and its liquid cooling pipe network automation design method

Abstract

The present invention belongs to the field related to energy storage technology, and discloses a lithium battery energy storage system and its liquid cooling pipe network automatic design method, which includes: obtaining the number of battery packs of the energy storage system and performing thermal and flow simulation of the single battery pack and the water-cooled plate to determine the minimum refrigerant flow, flow difference and water-cooled plate flow resistance coefficient S1; outputting the liquid cooling pipe network parameters that can meet the temperature uniformity conditions and have the best economic performance according to the design method; and building the actual liquid cooling pipe network of the energy storage system according to the liquid cooling pipe network parameters. The present invention can obtain a high-average temperature and high-reliability energy storage system liquid cooling pipe network module, which can effectively solve the technical problems such as capacity loss and life reduction caused by uneven temperature distribution of the current energy storage system compared with the prior art.

Description

Technical Field

[0001] The present invention belongs to the field related to energy storage technology, and more specifically, relates to a lithium battery energy storage system and an automated design method for a liquid cooling pipe network thereof. Background Art

[0002] Due to the rapid development of new energy technologies, the development of energy storage technology is imminent in order to ensure the safety of new energy such as wind energy and solar energy access to the power grid. Among them, lithium battery energy storage systems have been widely used in power grids due to their small footprint, easy installation and high mobility to effectively and flexibly balance energy demand and supply. Temperature has an important impact on key performance of lithium batteries such as capacity, power and safety. In lithium battery energy storage systems, many large-capacity and high-power batteries are closely arranged in a confined space, and the operating conditions are complex and changeable, which can easily cause uneven heat generation, uneven temperature distribution, and large temperature differences between batteries. This will lead to a decrease in battery charging and discharging performance, capacity and life. If the lithium battery energy storage system is not effectively thermally managed, thermal runaway will occur in severe cases, causing serious accidents. In addition to the temperature control function, the battery thermal management system itself will also consume a certain amount of energy. Therefore, it is necessary to take into account high performance and high efficiency in the design process, and strive to reduce manufacturing and operating costs. In order to achieve high performance and high safety of large-capacity lithium battery energy storage systems, efficient thermal management of energy storage systems is required.

[0003] As the scale of lithium battery energy storage systems gradually increases, among many heat dissipation solutions, active cold plate liquid cooling technology stands out in energy storage systems. With its advantages of good heat dissipation effect and precise temperature control, it has become the mainstream heat dissipation solution for future applications. It can effectively reduce the maximum temperature of the battery, improve the uniformity of temperature distribution and the consistency of system charge and discharge. The active cold plate liquid cooling system of the lithium battery energy storage station consists of a liquid cold plate and a corresponding liquid cooling pipe network. The refrigerant flows through the cold plate and exchanges heat with the battery indirectly to achieve battery cooling. At the same time, the liquid cooling pipe network is used to connect all cold plates to provide refrigerant to each battery pack. The main challenge in its design is that due to factors such as loss along the way and height difference, the flow distribution between the cold plates of each battery pack is uneven, which will reduce the temperature consistency of the whole machine, resulting in poor system charge and discharge consistency and increased battery capacity loss. The high design requirements and complex process of the liquid cooling pipe network restrict the promotion and development of large-scale lithium battery energy storage systems in my country. Summary of the invention

[0004] In view of the above shortcomings and improvement needs of the prior art, the present invention not only automatically arranges and designs the structure of the liquid cooling network by closely combining the characteristics and needs of the application conditions of the lithium battery energy storage system, but also optimizes and improves the operating conditions of the battery in a targeted manner, so that it can not only meet the operating temperature range of the battery pack, but also control the temperature difference of the whole machine, and effectively improve the economy of the liquid cooling network of the energy storage system and reduce the proportion of energy consumption. In addition, actual tests have shown that it is simple to operate manually, has good design efficiency, can obtain excellent design effects, and is suitable for the development of lithium battery energy storage system products of any scale.

[0005] To achieve the above object, according to one aspect of the present invention, a method for automatically designing a liquid cooling network for a lithium battery energy storage system is provided, the method comprising the following steps:

[0006] (i) Obtaining the number of battery packs in the energy storage system and performing thermal and flow simulations on the single battery packs and the water cooling plate to determine the minimum refrigerant flow rate, flow difference, and water cooling plate flow resistance coefficient S1;

[0007] Specifically, obtain the battery pack information of the energy storage system and perform simulation calculations of the single battery pack;

[0008] To design the liquid cooling network of a lithium battery energy storage power station, we first need to obtain the number of battery packs and perform thermal and flow simulations of the single battery pack-water cooling plate to obtain the following required values: the minimum refrigerant flow Q of the single battery pack to meet the operating temperature index stand , the flow rate that meets the temperature difference index and the minimum refrigerant flow rate Q stand The difference δQ stand , water cooling plate flow resistance coefficient S 1 .

[0009] (ii) Output the liquid cooling network parameters that meet the temperature uniformity conditions and economic performance according to the design method; specifically including:

[0010] (1) Establish a mathematical description of the mapping of the number of battery packs to various liquid cooling pipe network arrangements;

[0011] After obtaining the number of battery packs, establish a mapping of the number of battery packs N to X types of liquid cooling pipe network arrangements A X The mathematical description of the network can be automatically converted into a variety of pipe network mathematical diagrams. The mathematical description of this process is provided below. In the parallel liquid cooling network, the network can be constructed with given parameters. First, the graph consists of nodes and branches, the branches represent the pipes, and the nodes represent the intersections of the pipes. Here is a general expression for the liquid cooling network. Assume that there are N battery packs, divided into m rows, and arranged in A i =[n 1 ,n 2 ,…,n m ], where n1 +n 2 +…+n m = N. To construct a graph, we need to determine the sequence numbers of nodes and branches. The total number of nodes is 2m+2N. For the nodes on the main pipeline, they are labeled from 1 to 2m. For the nodes on group I as the third-level pipeline, we introduce the function Then they will be labeled O(i)+1 to O(i)+2n i , the total number of pipes / branches is 2m-1+3N. The branches on the main pipe are labeled 1 to 2m-1. For the branches on group I as the third-level pipe, a function is introduced Then they will be labeled B(i)+1 to B(i)+3n i After obtaining the sequence numbers of nodes and branches, connect each branch to its corresponding start and end nodes. For example, Figure 3 The mathematical diagram of different liquid cooling network arrangements for battery pack number N=40 is shown in FIG.

[0012] (2) Establish a hydraulic solution model for the liquid cooling network;

[0013] In order to solve the hydraulic parameters of the pipe network based on the pipe network structure, geometric parameters and pipe network component parameters, a pipe network hydraulic solution model was established. The pipe network hydraulic calculation model is based on the pipe network balance equation, which includes the node flow balance equation:

[0014]

[0015] In the formula, n represents the number of pipes in the network, m represents the number of nodes in the network, and b kj is the directional characteristic number of pipeline flow j to node k. When the working fluid in the pipeline flows into the node, b kj =1; when the working fluid in the pipeline flows out of the node, b kj = -1; when the pipeline is not connected to the node, b kj =0; and the circuit pressure balance equation:

[0016]

[0017] In the formula, b represents the number of loops in the pipe network, C ij is the directional characteristic number of pipeline flow j to loop i. When the working fluid flow direction in the pipeline is the same as the assumed loop direction, C ij =1; when the working fluid flow direction in the pipeline is opposite to the assumed loop direction, C ij =-1; when the pipeline is not connected to the loop, C ij =0;S j is the pipe resistance coefficient, H fj is the pump head in the pipeline, H Njis the potential energy difference between two nodes of the pipeline.

[0018] Since the cooling water system pipe network is a complex and large system, in order to prevent over-constraints when solving the equation group, this study uses the graph theory in mathematics to simplify the equation group, that is, only by selecting independent loops in the pipe network to establish equations, the required variables such as flow and head of each node and branch can be solved. After the independent loop is found, the loop pressure balance nonlinear equation group is established for it.

[0019]

[0020] Where, i = 1, 2, 3…n-m+1, q y1 ,q y2 ,…,q y(n-m+1) is the flow rate of the remainder pipeline, and n-m+1 is the number of independent loops. The water head of each node in the pipeline network and the flow rate of each pipeline can be solved through iterative solution.

[0021] (3) Liquid cooling network optimization;

[0022] The parameters of the liquid cooling network are optimized based on the genetic algorithm. Specifically, the network layout structure and geometric dimensions including the length of each pipe, the radius of each pipe, the position and opening of each valve, the number of booster pumps and their positions are optimized based on the genetic algorithm. Two constraints are defined in the optimization. Among them, constraint 1 is that the flow rate of each water cooling plate branch is greater than Q in step i. stand ; Constraint 2 is that the flow difference δQ between each water cooling plate is less than δQ stand ; Set the economic objective function Fitness, its expression is:

[0023] Fitness(A,D,L,V,N,P)=C 1 +C 2

[0024]

[0025] In the formula, A is the pipe network layout, D is the array of pipe radii at each level, L is the array of the length of each pipeline, V is the array of the position and opening of each valve, N is the number of booster pumps, and P is the position of the booster pump. r is the annual interest rate of the pipe network, t is the investment recovery time, d i , l i is the pipe diameter and flow rate, and the pipe cost can be calculated by function f, g(v i )S V is the valve cost, N pump is the number of pumps, W i is the pump cost; H, Q, η p are pump head, flow rate and efficiency, τ,c eare the annual working hours and electricity charges respectively, and α is the depreciation rate of the pipeline network;

[0026] The optimization process is as follows: first, the population is initialized and the constraints are determined. Then, the model is input for solution, and the fitness function value corresponding to each chromosome is calculated. Then, the chromosome is selected, crossover and mutated. After the set number of iterations, the chromosome parameter array corresponding to the optimal fitness function value is output. In the optimization process, the diversity of the population is maintained through selection, crossover and mutation operations, and the global optimal solution is gradually searched. Through the evaluation and selection of fitness function values, better individuals will be more likely to be selected and retained in the next generation. Crossover and mutation operations introduce new gene combinations, which are conducive to the evolution and optimization of the population. Through multiple iterations of operations, the chromosome parameter array corresponding to the optimal fitness function value is gradually approached and found. Finally, a set of liquid cooling pipe network layout structures and pipe network geometric dimensions that make the liquid cooling pipe network most economical are output, including the length of each pipe, the radius of each pipe, the position and opening of each valve, and the number of booster pumps.

[0027] (iii) constructing an actual liquid cooling network for the energy storage system according to the liquid cooling network parameters. Specifically, constructing a supporting liquid cooling network device for the target energy storage system according to the output parameters.

[0028] According to the output parameters of the design process, the supporting liquid cooling pipe network device products of the target energy storage system are established and produced for the liquid cooling pipe network of the lithium battery energy storage power station. The battery packs are placed and the liquid cooling pipe network is built according to the pipe network layout. The pipe length and pipe radius are selected one by one according to the geometric dimensions of the pipe network. The valves are set according to the position and opening of the pipe network output valves, and the booster pumps are set according to the number and position of the booster pumps in the pipe network. A set of liquid cooling pipe networks for lithium battery energy storage systems with high average temperature and high economy under rated working conditions is output.

[0029] The present invention also proposes a lithium battery energy storage system, including a liquid cooling pipe network, wherein the liquid cooling pipe network is designed and constructed according to the automatic design method for the liquid cooling pipe network of the lithium battery energy storage system as described in any one of the above embodiments.

[0030] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0031] 1. Through the automated design of the present invention, the structure of the liquid cooling network can not only quickly generate an optimized solution, but also be flexibly adjusted according to actual application requirements. Automated layout reduces potential errors in manual design, making the design process more efficient and reliable. This efficient design method saves time and labor costs, shortens the product development cycle, and improves the standardization of design.

[0032] 2. The present invention realizes temperature difference control under rated working conditions: Effectively controlling the temperature difference of the whole machine is a key factor in improving the overall performance of the energy storage system. By optimizing the design of the liquid cooling pipe network, the uniform distribution of the temperature of the whole machine can be achieved. This temperature difference control not only protects the safety of the battery, but also improves the energy utilization rate of the system. In addition, the uniform temperature distribution helps to delay the aging process of the battery and reduce maintenance costs.

[0033] 3. The present invention improves the economic efficiency of the liquid cooling system in the energy storage system, and reduces the initial investment and subsequent operating costs of the liquid cooling system through precise design and optimization. This design not only reduces the amount of materials used, but also reduces the energy consumption of the system, thereby improving the economic efficiency and conforming to the concept of sustainable development.

[0034] 4. The design scheme in the present invention is universal and can meet the product development needs of lithium battery energy storage systems of different scales, which makes it have a wide range of application prospects in the market. Whether it is a small energy storage device or a large energy storage power station, the system can be flexibly adjusted according to specific needs to provide the best solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the overall process flow of designing and constructing a liquid cooling pipe network for a lithium battery energy storage system constructed according to the present invention;

[0036] Figure 2 It is a mathematical description of the arrangement of the liquid cooling pipe network in the present invention;

[0037] Figure 3 It is a mapping diagram from the number of battery packs to the arrangement of the liquid cooling pipe network in accordance with the present invention;

[0038] Figure 4 It is a structural schematic diagram of a lithium battery energy storage system and a supporting liquid cooling pipe network designed according to a preferred embodiment of the present invention;

[0039] Figure 5 It is a structural front view of a lithium battery energy storage system and a supporting liquid cooling pipe network designed according to a preferred embodiment of the present invention;

[0040] Figure 6 It is a structural schematic diagram of the valves selected in the lithium battery energy storage system and the supporting liquid cooling pipe network after design according to the preferred embodiment of the present invention;

[0041] Figure 7 It is a top view schematic diagram of the valves selected in the lithium battery energy storage system and the supporting liquid cooling pipe network after design according to the preferred embodiment of the present invention. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0043] Figure 1 It is a schematic diagram of the overall process flow of designing and constructing the liquid cooling network of the lithium battery energy storage system constructed according to the present invention, such as Figure 1 As shown, the present invention obtains pending information of the energy storage system of the liquid cooling network to be designed, including the number of lithium battery packs and the heating power of the single lithium battery packs; performs thermal characteristic analysis of the single battery packs and cold plate flow resistance characteristic analysis to determine the cold plate flow condition and the cold plate flow resistance coefficient; establishes a mathematical description of the liquid cooling network structure and a hydraulic solution model for the liquid cooling network; designs the liquid cooling network based on the pending information and the hydraulic solution model for the liquid cooling network in combination with an optimization algorithm; in the optimization process, the liquid cooling network is made to have high economy and meet the requirements of high temperature uniformity by adjusting the distribution structure, geometric dimensions and component parameters of the liquid cooling network; according to the output parameters of the design process, a matching liquid cooling network device product for the target energy storage system is established and produced to have high temperature uniformity and high economy.

[0044] According to the basic concept of the present invention, the above-mentioned lithium battery energy storage system liquid cooling pipe network design method mainly includes the following steps:

[0045] First, obtain the pending information of the energy storage system for the liquid cooling network to be designed, including the number of lithium battery packs N, the heat generation power P of the single lithium battery pack, and the geometric dimensions of the single battery pack (length, width, height L, W, H); perform thermal characteristics analysis of the single battery pack and cold plate flow resistance characteristics analysis to determine the cold plate flow condition Q stand , δQ stand And the cold plate flow resistance coefficient S1;

[0046] Then, a liquid cooling pipe network arrangement A corresponding to the battery pack arrangement is established through mathematical description;

[0047] Establish and utilize the network hydraulic solution model, and couple it with the genetic algorithm to optimize the design of the liquid cooling network. In the optimization process, the liquid cooling network distribution structure, geometric dimensions and component parameters are optimized to make the liquid cooling network highly economical, and the flow condition Q is met by controlling the flow. stand , δQ stand To ensure high uniformity of system temperature;

[0048] The optimization process outputs the best parameter set, including the liquid cooling network distribution structure, geometric dimensions and component parameters, according to which the liquid cooling network is built.

[0049] In this process, according to the preferred embodiment of the present invention, the following parameter settings are preferably adopted: In the pipe network hydraulic solution model, the convergence judgment condition is that the error is at least less than 10 -6 ;

[0050] Next comes the optimization design step of the liquid cooling network.

[0051] During the optimization process, if the number of battery packs N<30, the number of populations in the optimization process is 100 and the number of iterations is 50. If 30<=N<60, the number of populations in the optimization process is 100 and the number of iterations is 100. Considering the pump power and system efficiency, if N>=60, it needs to be split into multiple energy storage systems consisting of a smaller number of battery packs.

[0052] According to the geometric dimensions of the battery pack, the length range of the pipeline is 1.5L-3L for the first-level pipeline, 1.5H-2H for the second-level pipeline, and 0.3L-0.7L for the third-level pipeline. The diameter range of the pipeline is 40-80mm for the first-level pipeline, 20-30mm for the second-level pipeline, and 8-15mm for the third-level pipeline.

[0053] The variation factor and crossover factor of the optimization process are 0.4 and 0.5 respectively;

[0054] Finally, it is the step of building the liquid cooling network of the energy storage system.

[0055] During the construction process, you first need to arrange the battery pack according to the output value battery pack arrangement structure A and design the cabinet. Then determine the liquid cooling network structure according to the output value liquid cooling network mathematical diagram; select appropriate pipes according to the radius of each level of output value pipes; cut pipes according to the length of each output value pipe; select three-way joints of corresponding sizes to connect each pipe, and rubber rings and raw tape are required between each thread to ensure the sealing of the liquid cooling network. During the construction process, select valves with dials.

[0056] The present invention will be explained more clearly below through a specific embodiment.

[0057] Input the number of battery packs N = 40 for the energy storage system to be designed, the battery pack size is 300*400*200mm, the battery heating power is 700w, and the working fluid is 25℃ water. According to the thermal simulation results, the minimum flow rate is Q = 8L / min, and the flow difference standard is 1.5L / min. Various arrangements are obtained based on the number of battery packs, such as Figure 3 As shown (12 types are selected for display).

[0058] According to the geometric dimensions of the battery pack, the length of the first-level pipeline is 450-1200mm, the length of the second-level pipeline is 300-400mm, and the length of the third-level pipeline is 90-210mm;

[0059] Take the population size as 100 and the number of iterations as 100;

[0060] Build a liquid cooling network based on the output optimal parameter group:

[0061] The battery pack arrangement in the output parameter group is [8 8 8 8 8] (e.g. Figure 3 , 12);

[0062] The length group is primary pipeline [1100, 600, 600, 600, 600]; secondary pipeline

[300] ; tertiary pipeline

[90] ; valve position [1 2 3 4 5 6 7 8; 9 11 12 14 15; 18 20 22 24; 28 30 32; 40] and corresponding opening [60°50°50°30°30°10°10°; 50°30°20°20°10°; 40°20°10°20°; 30°20°10°; 20°]; the number of booster pumps is 0;

[0063] According to the above parameters, Figure 4 , Figure 5 The liquid cooling network is shown in the figure. Since the total number of battery packs is 40, there are 5 rows of 8 batteries in each row. Figure 3 ,12 for arrangement, Figure 4 , 13 is the primary pipeline (export), 14 is the secondary pipeline (import), 15 is the secondary pipeline (export); 16 is the cold plate, 17 is the battery pack, 18 is the primary pipeline (import);

[0064] See also Figure 5 , 20 is the main pump outlet, 19 is the main pump inlet; 21 is the valve, 22 is the third-level pipeline outlet, 23 is the third-level pipeline (import); 24 is the energy storage system cabinet, which is designed according to the battery pack sequence;

[0065] See also Figure 6 and Figure 7 , for the selected valve style, twisting the valve switch 27 can clearly confirm the accurate valve opening on the instrument panel 25 according to the valve pointer 26;

[0066] In this embodiment, the energy storage system liquid cooling network designed by the design method can achieve good heat distribution uniformity, the temperature difference of the whole machine is within 3°C, and the batteries all work within the normal temperature range (30-33°C); the economic cost is low, and the economy is improved by 35% compared with the energy storage liquid cooling network that is not optimized; it shows that the liquid cooling network designed by the method of the present invention has high temperature uniformity, high economy, and high reliability;

[0067] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for automated design of a liquid cooling network for a lithium battery energy storage system, characterized in that: The following steps are involved: (i) Obtaining the number of battery packs in the energy storage system and performing thermal and flow simulations on the single battery packs and the water cooling plate to determine the minimum refrigerant flow rate, flow difference, and water cooling plate flow resistance coefficient S1; (ii) outputting the liquid cooling network parameters that meet the temperature uniformity conditions and economic performance according to the design method; (iii) Build the actual liquid cooling network of the energy storage system according to the liquid cooling network parameters.

2. The method for automated design of a liquid cooling network for a lithium battery energy storage system according to claim 1, characterized in that: In step (ii), further including establishing the number of battery packs N, the arrangement of the battery packs A X , a mathematical model between the mathematical diagrams of the liquid cooling network to achieve automatic conversion between the number of battery packs and various network diagrams.

3. The method for automated design of a liquid cooling network for a lithium battery energy storage system according to claim 2, characterized in that: The mathematical graph of the liquid cooling pipe network is composed of nodes and branches, wherein the nodes are pipe intersections and the branches are pipes.

4. The method for automated design of a liquid cooling network for a lithium battery energy storage system according to any one of claims 1 to 3, characterized in that: A hydraulic solution model based on the pipe network balance equation is established, including the node flow balance equation and the loop pressure balance equation. Graph theory is used to select independent loops to simplify the equation group, and the water head at each node and the pipeline flow are obtained through iterative solution.

5. The method for automated design of a liquid cooling network for a lithium battery energy storage system according to any one of claims 1 to 4, characterized in that: Genetic algorithms are used to optimize the layout structure and geometric dimensions of the liquid cooling network, set constraints to ensure that the flow meets the requirements, and define the economic objective function Fitness. The optimal economic liquid cooling network configuration is finally output through optimization.

6. The method for automated design of a liquid cooling network for a lithium battery energy storage system according to any one of claims 1 to 5, characterized in that: Based on the optimized output parameters, a high-average-temperature, high-economic lithium battery energy storage system liquid cooling pipe network device is built, including battery packs, pipe network distribution, pipe geometry, the position and opening of valves with precisely adjustable openings, and the number and position of booster pumps.

7. A lithium battery energy storage system, characterized in that: It includes a liquid cooling pipeline network, which is designed and constructed according to the automated design method for liquid cooling pipeline network of a lithium battery energy storage system as claimed in any one of claims 1 to 6.

Images