CN116487770A - Thermal management method for battery energy storage system - Google Patents
Thermal management method for battery energy storage system Download PDFInfo
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- 238000004146 energy storage Methods 0.000 title claims abstract description 46
- 238000007726 management method Methods 0.000 title claims abstract description 45
- 239000007788 liquid Substances 0.000 claims abstract description 330
- 238000001816 cooling Methods 0.000 claims abstract description 192
- 238000010438 heat treatment Methods 0.000 claims abstract description 44
- 238000000034 method Methods 0.000 claims abstract description 44
- 238000005057 refrigeration Methods 0.000 claims abstract description 26
- 230000017525 heat dissipation Effects 0.000 claims abstract description 19
- 101150055297 SET1 gene Proteins 0.000 claims abstract description 10
- 101150117538 Set2 gene Proteins 0.000 claims abstract description 10
- 230000008569 process Effects 0.000 claims abstract description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 32
- 239000000110 cooling liquid Substances 0.000 claims description 30
- 239000011248 coating agent Substances 0.000 claims description 5
- 238000000576 coating method Methods 0.000 claims description 5
- 238000007791 dehumidification Methods 0.000 claims description 4
- 238000012423 maintenance Methods 0.000 claims description 3
- 238000012546 transfer Methods 0.000 claims description 3
- 238000009413 insulation Methods 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract description 4
- 238000013461 design Methods 0.000 description 16
- 239000002826 coolant Substances 0.000 description 10
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 6
- 238000010586 diagram Methods 0.000 description 4
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
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- 230000008859 change Effects 0.000 description 2
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- 238000012983 electrochemical energy storage Methods 0.000 description 2
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- 229910052744 lithium Inorganic materials 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
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- NAWXUBYGYWOOIX-SFHVURJKSA-N (2s)-2-[[4-[2-(2,4-diaminoquinazolin-6-yl)ethyl]benzoyl]amino]-4-methylidenepentanedioic acid Chemical compound C1=CC2=NC(N)=NC(N)=C2C=C1CCC1=CC=C(C(=O)N[C@@H](CC(=C)C(O)=O)C(O)=O)C=C1 NAWXUBYGYWOOIX-SFHVURJKSA-N 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/60—Heating or cooling; Temperature control
- H01M10/63—Control systems
- H01M10/633—Control systems characterised by algorithms, flow charts, software details or the like
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/60—Heating or cooling; Temperature control
- H01M10/61—Types of temperature control
- H01M10/613—Cooling or keeping cold
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/60—Heating or cooling; Temperature control
- H01M10/61—Types of temperature control
- H01M10/615—Heating or keeping warm
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/60—Heating or cooling; Temperature control
- H01M10/61—Types of temperature control
- H01M10/617—Types of temperature control for achieving uniformity or desired distribution of temperature
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/60—Heating or cooling; Temperature control
- H01M10/62—Heating or cooling; Temperature control specially adapted for specific applications
- H01M10/627—Stationary installations, e.g. power plant buffering or backup power supplies
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/60—Heating or cooling; Temperature control
- H01M10/65—Means for temperature control structurally associated with the cells
- H01M10/655—Solid structures for heat exchange or heat conduction
- H01M10/6556—Solid parts with flow channel passages or pipes for heat exchange
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/60—Heating or cooling; Temperature control
- H01M10/65—Means for temperature control structurally associated with the cells
- H01M10/656—Means for temperature control structurally associated with the cells characterised by the type of heat-exchange fluid
- H01M10/6567—Liquids
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention relates to a battery energy storage system heat management method, when the battery temperature exceeds the limit, the liquid cooling unit of a liquid cooling system is controlled to work, and the battery temperature is controlled to 20-25 ℃; the method comprises two working modes of refrigeration and heating; and (3) refrigerating: when the battery is at the highest temperatureT cell_max >T 1 When the battery management system issues instructions to the liquid cooling unit, the battery management system wraps the liquid cooling unitTarget value of liquid temperatureT set1 Sum and return difference deltaT margin1 The method comprises the steps of carrying out a first treatment on the surface of the The instruction is maintained toT cell_max Cooling to 25 ℃; if the actual liquid temperature of the outlet of the liquid cooling unit is higher than the target value by delta in the instruction maintaining periodT margin1 Starting refrigeration; if the outlet actual liquid temperature is lower than the target value by deltaT margin1 Stopping refrigeration; heating: when the battery has the lowest temperatureT cell_min <T 2 When the battery management system issues instructions to the liquid cooling unit, the instructions comprise a liquid temperature target valueT set2 Sum and return difference deltaT margin2 The method comprises the steps of carrying out a first treatment on the surface of the The instruction is held toT cell_min Raising the temperature to 20 ℃; and during the instruction maintaining period, the heating start-stop is controlled by the return difference in the same way as the refrigerating process. The method can improve the heat dissipation and temperature equalization effects of the battery cell and improve the temperature uniformity of the battery pack and the battery cell therein.
Description
Technical Field
The invention relates to the field of energy storage systems, in particular to a battery energy storage system thermal management method based on liquid cooling.
Background
The energy storage system can provide various services such as peak shaving, black start and the like for the power grid, so that new energy consumption is promoted, and electrochemical energy storage is an important development direction of a large-scale energy storage technology. Prefabricated cabin battery energy storage systems are becoming a dominant form of large-scale electrochemical energy storage systems by virtue of outstanding flexibility and convenience. Compared with the traditional fixed energy storage power station, the prefabricated cabin type battery energy storage system has the advantages of short installation and construction period, small occupied area, flexible movement and the like. On the other hand, the prefabricated cabin is airtight, and as the system capacity is larger and larger, the battery density is higher and higher, and the requirement on efficient heat dissipation is also continuously improved. The operating temperature of lithium batteries and the consistency of temperature between batteries have an important impact on the overall life and safe operation of the energy storage system.
The design of the lithium ion battery thermal management system adopts one or more thermal management techniques to control the heat exchange between the inside and the outside of the battery according to the operation requirement of the battery and the conditions of the internal and the external thermal loads to be suffered during the operation of the lithium ion battery. At present, cooling modes of the lithium ion battery mainly comprise air cooling, liquid cooling, phase change cooling and heat pipe cooling. Air cooling has advantages such as simple structure, with low costs, but heat dissipation rate and radiating efficiency are not high to it is difficult to maintain single battery temperature homogeneity. This makes air cooling more suitable for applications where the heat generation rate of the battery is low. The liquid cooling has higher heat dissipation speed and heat dissipation efficiency, is easy to ensure the temperature uniformity of the battery, and has the cost between that of air cooling and phase change cooling/heat pipe cooling. With the improvement of the capacity, the energy density and the working multiplying power of the lithium battery, people have higher requirements on heat dissipation of a battery system, and the technical and economic advantages of liquid cooling are highlighted. At present, most electric automobiles adopt a liquid cooling system. In energy storage application occasions, although air cooling is still a main cooling mode, higher heat dissipation requirements are brought by compact and intensive development of the system, and liquid cooling is beginning to be popularized and applied. There is a need to design a liquid-cooled thermal management scheme for energy storage systems.
Disclosure of Invention
The invention aims to provide a thermal management method of a battery energy storage system, which can improve the effects of heat dissipation and temperature balance of a battery cell and improve the temperature uniformity of the battery pack and the battery cell therein.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: when the temperature of the battery exceeds a set range, the battery management system controls the liquid cooling unit of the liquid cooling system to work, and the temperature of the battery is controlled to be within a range of 20-25 ℃; the method comprises two working modes of refrigeration and heating:
refrigeration operation mode: when the single battery is at the highest temperature T cell_max >T 1 When the battery management system issues instructions to the liquid cooling unit, the instructions comprise a liquid temperature target value T set1 And return difference delta T margin1 The method comprises the steps of carrying out a first treatment on the surface of the The instruction is maintained until the highest temperature T of the single battery cell_max Cooling to 25 ℃; if the actual liquid temperature of the outlet of the liquid cooling unit is higher than the target value by delta T during the instruction maintenance period margin1 Starting refrigeration; if the actual liquid temperature of the outlet of the liquid cooling unit is lower than the target value by delta T margin1 Stopping refrigeration; frequent starting and closing of the unit are prevented through setting of return difference;
heating operation mode: when the minimum temperature T of the single battery cell_min <T 2 When the battery management system issues instructions to the liquid cooling unit, the instructions comprise a liquid temperature target value T set2 And return difference delta T margin2 The method comprises the steps of carrying out a first treatment on the surface of the The instruction is maintained until the highest temperature T of the single battery cell_min Raising the temperature to 20 ℃; and during the instruction maintaining period, the heating start-stop is controlled by the return difference in the same way as the refrigerating process.
Further, for the cooling mode of operation, T 1 ＝30℃，T set1 ＝18℃，ΔT margin1 =3deg.C, i.e. when the cell is at the highest temperature T cell_max >At 30 ℃, the battery management system issues instructions to the liquid cooling unit, including a liquid temperature target value T set1 =18 ℃ and return difference Δt margin1 =3 ℃; during the instruction maintaining period, the liquid cooling unit is started to cool when the liquid outlet temperature is higher than 21 ℃, and the liquid cooling unit is closed to cool when the liquid outlet temperature is lower than 15 ℃;
for heating operation mode, T 2 ＝15℃，T set2 ＝30℃，ΔT margin2 =5 ℃, i.e. when the cell has the lowest temperature T cell_min <At 15 ℃, the battery management system issues instructions to the liquid cooling unit, which comprisesTarget value T of liquid temperature set2 =30deg.C and return difference ΔT margin2 =5 ℃; and during the instruction maintaining period, starting heating when the liquid cooling unit liquid outlet temperature is lower than 25 ℃, and stopping heating when the liquid cooling unit liquid outlet temperature is higher than 35 ℃.
Further, the liquid cooling system comprises liquid cooling plates, liquid cooling pipelines and liquid cooling units, the number of the liquid cooling plates is matched with that of the battery modules in the battery energy storage system, each liquid cooling plate is respectively arranged on the lower side of the corresponding battery module and is in contact with the bottom of the battery core, and the liquid cooling plates and the battery modules are integrated in the battery pack; the liquid cooling pipeline comprises a main liquid inlet pipe, a battery cabinet liquid inlet branch pipe, a battery pack liquid outlet branch pipe, a battery cabinet liquid outlet branch pipe and a main liquid outlet pipe, wherein the liquid inlet and outlet ports of each liquid cooling plate are respectively connected with the battery pack liquid inlet and outlet branch pipes, all the battery pack liquid inlet and outlet branch pipes of a single battery cabinet are respectively connected with the battery cabinet liquid inlet and outlet branch pipes in parallel, all the battery cabinet liquid inlet and outlet branch pipes are respectively connected with the main liquid inlet and outlet pipes in parallel, and the main liquid inlet and outlet pipes are connected with the liquid cooling unit.
Further, the battery energy storage system comprises k subsystems, each subsystem is formed by parallelly connecting n battery cabinets, the n battery cabinets are arranged side by side in the transverse direction, each battery cabinet is formed by serially connecting m battery packs, the m battery packs are stacked layer by layer in the vertical direction, each battery pack comprises a x b serial battery cores, and the a x b serial battery cores are arranged in an array along the horizontal direction according to a row b; the liquid cooling system is provided with k sets of liquid cooling pipelines and k liquid cooling units corresponding to k subsystems.
Further, a U-shaped flow channel is formed in the liquid cooling plate, the U-shaped flow channel consists of a liquid inlet side flow channel, a bottom flow channel and a liquid outlet side flow channel, and the liquid inlet side flow channel and the liquid outlet side flow channel are respectively connected with a battery pack liquid inlet branch pipe and a battery pack liquid outlet branch pipe; the liquid inlet side flow channel comprises a plurality of liquid inlet branch flow channels, the liquid outlet side flow channel comprises a plurality of liquid outlet branch flow channels, and all the liquid inlet branch flow channels are converged into the bottom flow channel and then distributed to all the liquid outlet branch flow channels; all the liquid inlet branch flow passages, the bottom flow passages and the liquid outlet branch flow passages are contacted with the bottoms of all the electric cores in the battery pack so as to exchange heat with all the electric cores, and heat dissipation of all the electric cores is realized.
Further, if the battery pack is provided with the odd-numbered rows of cells, that is, b is odd, the liquid inlet side flow channel further comprises a liquid inlet half branch flow channel with a flow channel width being half of that of the liquid inlet branch flow channel, the liquid outlet side flow channel further comprises a liquid outlet half branch flow channel with a flow channel width being half of that of the liquid outlet branch flow channel, and the liquid inlet half branch flow channel and the liquid outlet half branch flow channel are both in contact with the bottoms of the cells in the middle row.
Further, the channel widths of the liquid inlet branch channel, the bottom channel and the liquid outlet branch channel are calculated by the following formula:
wherein D is the width of the flow channel, W is the thickness of the single cell, A is the area of the heat exchange surface, and the heat exchange surface is calculated by the following formula:
P cell ＝h·ΔT·A
wherein P is cell The heat exchange power of the single cell is that h is the heat transfer coefficient of the liquid cooling plate and the cooling liquid, and DeltaT is the temperature difference between the cooling liquid and the wall surface of the liquid cooling plate;
the height of the flow channel in the liquid cooling plate is calculated by the following formula:
P pack ＝cρVΔT rise ＝cρvH·zD·ΔT rise
wherein P is pack The maximum heating power of the battery pack is calculated by C, rho, V, delta T, and the specific heat capacity of the cooling liquid rise For the temperature rise of the cooling liquid, v is the flow velocity of the cooling liquid, H is the height of the flow channel, and z is the flow channel coefficient determined according to the number of the branch flow channels.
Further, the main liquid inlet pipe and the main liquid outlet pipe are transversely arranged on the upper side of the battery cabinet, and the liquid inlet branch pipes and the liquid outlet branch pipes of each battery cabinet extend vertically and are respectively connected with the liquid inlet branch pipes and the liquid outlet branch pipes of the battery packs on different layers through tee joints; the horizontal direction interface aperture of the tee on different layers is increased layer by layer from top to bottom or once every other a plurality of layers to reduce the flow resistance of the lower layer pipeline and balance the flow of the cooling liquid in the battery packs on different heights.
Further, the lower surface of each battery pack is sprayed with a heat-insulating coating so as to reduce the temperature difference between the lower surface of the battery pack and air, and further reduce the generation of condensed water; a drainage groove is uniformly distributed above the front side of each battery pack so as to prevent condensed water at the top from dropping onto the high-low pressure connector at the front side of the battery pack; all the drainage tanks are communicated by drain pipes and led out of a battery cabin for placing a battery cabinet; all the battery cabinets are closely arranged in the battery compartment so as to reduce the air content in the battery compartment and further reduce the water vapor quantity; the waterproof grade of the battery compartment reaches IPX5, so that convection between outside air and air in the compartment is reduced, and excessive water vapor is prevented from entering the battery compartment; a dehumidifying air conditioner is arranged in the battery compartment.
Further, in the process of carrying out heat management on the battery energy storage system, the operation of the dehumidifying air conditioner is controlled according to the following method:
1) When the liquid cooling unit is refrigerating, and the ambient temperature T ambt When the temperature is more than 25 ℃ or the humidity RH is more than 50%, starting a dehumidifying air conditioner;
2) Setting the control target as an ambient temperature target T ambt_set =22 ℃, humidity target RH set < 60%, i.e. when the ambient temperature T ambt When the temperature is not higher than 22 ℃ and the humidity RH is less than 60 percent, turning to the step 3);
3) Judging whether the liquid cooling unit stands by, if so, closing the dehumidifying air conditioner, otherwise, continuing to execute the step 2).
Compared with the prior art, the invention has the following beneficial effects: the method provides a liquid cooling heat management method for controlling a liquid cooling system through a battery management system when the temperature of the battery is over-limit, and controls the temperature of the battery to be in a range of 20-25 ℃, so that the heat dissipation and temperature balance effects of the battery cell are improved, and the temperature uniformity of the battery pack and the battery cell therein is improved. In addition, the method also provides a corresponding liquid cooling system, and the liquid cooling plate and the liquid cooling pipeline are designed, so that the liquid cooling plate can reliably and fully exchange heat with the battery cells, and the flow of the cooling liquid in each battery pack is balanced, and the temperature rise is stable, thereby improving the heat dissipation speed and heat dissipation efficiency of the liquid cooling system in the prefabricated cabin type battery energy storage system, and ensuring the temperature uniformity of the battery packs and the battery cells therein. Therefore, the invention has strong practicability and wide application prospect.
Drawings
FIG. 1 is a flow chart of a method implementation of an embodiment of the present invention.
FIG. 2 is a schematic diagram of a liquid cooling system according to an embodiment of the invention.
Fig. 3 is a schematic diagram of a battery energy storage system according to an embodiment of the invention.
Fig. 4 is a schematic view showing the composition of a battery pack according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of a U-shaped flow channel structure in a liquid cooling plate according to an embodiment of the present invention.
FIG. 6 is a schematic diagram of a liquid cooling circuit in accordance with an embodiment of the present invention.
FIG. 7 is a schematic view of a tee set position in an embodiment of the invention.
Fig. 8 is a flowchart of an implementation of controlling the operation of the dehumidifying air conditioner in the embodiment of the present invention.
Fig. 9 is a graph of cooling mode temperature in an embodiment of the invention.
Fig. 10 is a temperature profile of a heating mode in an embodiment of the present invention.
In the figure: 1-a liquid cooling plate; 2-liquid cooling pipeline; 21-a main liquid inlet pipe; 22-a battery cabinet liquid inlet branch pipe; 23-a battery pack liquid inlet branch pipe; 24-a battery pack outlet manifold; 25-a battery cabinet liquid outlet branch pipe; 26-a main liquid outlet pipe; 3-a liquid cooling unit; 4-a battery cabinet; 5-battery pack; 6-a confluence cabinet; 7-a control cabinet; 8-a fire-fighting cabinet; 9-dehumidifying air conditioner; 10-tee joint.
Detailed Description
The invention will be further described with reference to the accompanying drawings and examples.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
Good thermal management methods for battery energy storage systems can maintain battery temperature in a suitable interval. The cooling liquid is in a self-circulation state in daily life. The refrigeration or heating function needs to meet certain conditions before starting.
The embodiment provides a battery energy storage system heat management method, when the battery temperature exceeds a set range, a liquid cooling unit of a liquid cooling system is controlled to work through a battery management system, and the battery temperature is controlled to be within a range of 20-25 ℃. The method comprises two working modes of refrigeration and heating:
(1) Refrigeration operation mode: when the single battery is at the highest temperature T cell_max >T 1 When the battery management system issues instructions to the liquid cooling unit, the instructions comprise a liquid temperature target value T set1 And return difference delta T margin1 The method comprises the steps of carrying out a first treatment on the surface of the The instruction is maintained until the highest temperature T of the single battery cell_max Cooling to 25 ℃; if the actual liquid temperature of the outlet of the liquid cooling unit is higher than the target value by delta T during the instruction maintenance period margin1 Starting refrigeration; if the actual liquid temperature of the outlet of the liquid cooling unit is lower than the target value by delta T margin1 Stopping refrigeration; frequent starting and closing of the unit are prevented through setting of return difference;
(2) Heating operation mode: when the minimum temperature T of the single battery cell_min <T 2 When the battery management system issues instructions to the liquid cooling unit, the instructions comprise a liquid temperature target value T set2 And return difference delta T margin2 The method comprises the steps of carrying out a first treatment on the surface of the The instruction is maintained until the highest temperature T of the single battery cell_min Raising the temperature to 20 ℃; and during the instruction maintaining period, the heating start-stop is controlled by the return difference in the same way as the refrigerating process.
In the present embodiment, as shown in FIG. 1, T is as follows for the cooling mode of operation 1 ＝30℃，T set1 ＝18℃，ΔT margin1 =3deg.C, i.e. when the cell is at the highest temperature T cell_max >At 30 ℃, the battery management system issues instructions to the liquid cooling unit, including a liquid temperature target value T set1 =18 ℃ and return difference Δt margin1 =3 ℃; and during the instruction maintaining period, the liquid cooling unit is started to perform refrigeration when the liquid outlet temperature is higher than 21 ℃, and the liquid cooling unit is stopped to perform refrigeration when the liquid outlet temperature is lower than 15 ℃. For heating operation mode, T 2 ＝15℃，T set2 ＝30℃，ΔT margin2 =5 ℃, i.e. when the cell has the lowest temperature T cell_min <At 15 ℃, the battery management system issues instructions to the liquid cooling unit, including a liquid temperature target value T set2 =30deg.C and return difference ΔT margin2 =5 ℃; and during the instruction maintaining period, starting heating when the liquid cooling unit liquid outlet temperature is lower than 25 ℃, and stopping heating when the liquid cooling unit liquid outlet temperature is higher than 35 ℃.
As shown in fig. 2, the liquid cooling system includes a liquid cooling plate 1, a liquid cooling pipeline 2 and a liquid cooling unit 3. The number of the liquid cooling plates is adapted to the number of the battery modules in the battery energy storage system, as shown in fig. 4, each liquid cooling plate is respectively arranged at the lower side of the corresponding battery module and contacts with the bottom of the battery core, and the liquid cooling plates and the battery modules are integrated in the battery pack. As shown in fig. 6, the liquid cooling pipeline 2 includes a main liquid inlet pipe 21, a battery cabinet liquid inlet branch pipe 22, a battery pack liquid inlet branch pipe 23, a battery pack liquid outlet branch pipe 24, a battery cabinet liquid outlet branch pipe 25 and a main liquid outlet pipe 26, wherein the liquid inlet and outlet ports of each liquid cooling plate are respectively connected with the battery pack liquid inlet and outlet branch pipes, all the battery pack liquid inlet and outlet branch pipes of a single battery cabinet are respectively connected with the battery cabinet liquid inlet and outlet branch pipes in parallel, all the battery cabinet liquid inlet and outlet branch pipes are respectively connected with the main liquid inlet and outlet pipes in parallel, and the main liquid inlet and outlet pipes are connected with a liquid cooling unit.
The battery energy storage system comprises k subsystems, each subsystem is formed by parallelly connecting n battery cabinets, the n battery cabinets are arranged side by side in the transverse direction, each battery cabinet is formed by serially connecting m battery packs, the m battery packs are stacked layer by layer in the vertical direction, each battery pack comprises a x b serial battery cores, and the a x b serial battery cores are arranged in an array along the horizontal direction according to a row b; the liquid cooling system is provided with k sets of liquid cooling pipelines and k liquid cooling units corresponding to k subsystems.
As shown in fig. 2 and 3, in the present embodiment, the battery energy storage system includes 2 subsystems, each subsystem includes 5 battery cabinets 4, 1 liquid cooling unit 3, and 1 bus bar 6, each battery cabinet 4 includes 7 battery packs 5, and each battery pack 5 includes 11×3 battery cells. The battery cabinet is positioned in the battery compartment, the battery adopts a 280Ah battery core, the rated voltage of the battery core is 3.2V, and the designed maximum charge-discharge multiplying power is 0.5C. The batteries in the battery pack adopt a 1P33S connection mode, namely 33 battery cells are connected in series. 7 battery packs are connected in series to form a battery cabinet, and 10 battery cabinets are divided into 2 subsystems, and every 5 battery cabinets are electrically connected in parallel. In this example, the stack parameters are shown in table 1.
Table 1 stack parameters
In general engineering, the heat dissipation requirement is greater than the heating requirement, because the battery cell can generate heat during energy storage operation. For the energy storage engineering aimed at by the embodiment, the temperature of the environment where the energy storage engineering is located is more than or equal to 0 ℃, and according to the 280Ah battery cell characteristics, the battery cell temperature is more than or equal to 0 ℃ and can be charged and discharged at 0.5 ℃, so that the requirement on the heating capacity is very low. Therefore, the design of the liquid cooling system mainly considers the heat dissipation requirement. For special engineering with heating requirement greater than heat dissipation requirement, the design method of the system is also applicable, but only needs to start from the heating requirement.
The liquid cooling plate and the battery module are integrated in the battery pack. The liquid cooling plate is arranged below the battery module and is in contact with the bottom of the battery cell for heat dissipation. The flow channel design of the liquid cooling plate mainly has 2 principles: firstly, the flow passage design ensures that the flow resistance is as small as possible so as to ensure that the coolant flows uniformly and smoothly; and the area of the joint surface of the runner and the battery core is enough to ensure that the battery core and the cooling liquid exchange heat fully. In the system, a U-like flow channel is arranged in the liquid cooling plate and consists of a liquid inlet side flow channel, a bottom flow channel and a liquid outlet side flow channel, and the liquid inlet side flow channel and the liquid outlet side flow channel are respectively connected with a battery pack liquid inlet branch pipe and a battery pack liquid outlet branch pipe. The liquid inlet side flow channel comprises a plurality of liquid inlet branch flow channels, the liquid outlet side flow channel comprises a plurality of liquid outlet branch flow channels, and all the liquid inlet branch flow channels are converged into the bottom flow channel and then distributed to all the liquid outlet branch flow channels. All the liquid inlet branch flow passages, the bottom flow passages and the liquid outlet branch flow passages are contacted with the bottoms of all the electric cores in the battery pack so as to exchange heat with all the electric cores, and heat dissipation of all the electric cores is realized.
In this embodiment, 3 rows of cells are disposed in the battery pack, so the liquid inlet side flow channel further includes a liquid inlet half branch flow channel with a flow channel width being half of that of the liquid inlet side flow channel, the liquid outlet side flow channel further includes a liquid outlet half branch flow channel with a flow channel width being half of that of the liquid outlet branch flow channel, and both the liquid inlet half branch flow channel and the liquid outlet half branch flow channel are in contact with the bottom of the middle row of cells, so that the contact between a complete branch flow channel and the bottom of the middle row of cells is equivalent.
In this embodiment, the structure of the U-shaped flow channel in the liquid cooling plate is shown in fig. 5. Fig. 5 (a) is a schematic view of a flow channel structure, and fig. 5 (b) is a schematic view of a contact position between a flow channel and a battery cell.
The channel widths of the liquid inlet branch channel, the bottom channel and the liquid outlet branch channel are calculated by the following formula:
wherein D is the width of the flow channel, W is the thickness of a single cell, A is the area of the heat exchange surface, and the area is calculated by the following heat convection heat exchange calculation formula:
P cell ＝h·ΔT·A (2)
wherein P is cell The heat exchange power is single-cell; h is the heat transfer coefficient of the liquid cooling plate and the cooling liquid, which is about 670W/(m) 2 K); delta T is the temperature difference between the cooling liquid and the wall surface of the liquid cooling plate.
It can be seen from the formula (2) that the larger the temperature difference is, the larger the heat exchange amount is. In this embodiment, the heating power of the single cell at the designed maximum charge-discharge rate of 0.5C is 12W. In order to reduce the battery cell to normal temperature at maximum heating power, the battery cell temperature (i.e., the liquid cooling plate wall temperature) is set to normal temperature 25 ℃ and the cooling liquid temperature is set to the target liquid temperature 18 ℃ during cooling, so Δt=7 ℃. The required heat dissipation area a=2558 mm can be calculated according to equation (2) 2 . In this embodiment, the cell thickness is 68mm, and D is 38mm according to formula (1), i.e. the channel width is at least 38mm。
The height of the flow channel in the liquid cooling plate is calculated by the following formula:
P pack ＝cρVΔT rise ＝cρvH·zD·ΔT rise (3)
wherein P is pack Maximum heating power of the battery pack; c is the specific heat capacity of the coolant, ρ is the density of the coolant, and in this example, ethylene glycol is used as the coolant, so c is about 3 kJ/(kg ℃ C.), ρ is 1071kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the V is the flow rate of the cooling liquid, delta T rise For the temperature rise of the cooling liquid, v is the flow velocity of the cooling liquid, H is the height of the flow channel, and z is the flow channel coefficient determined according to the number of the branch flow channels. For this example, z is taken to be 1.5.
As can be seen from equation (3), the allowable temperature rise determines the minimum flow rate of the coolant, thereby affecting the coolant flow rate and the height of the liquid cooling plate. In the present embodiment, deltaT rise When the design is carried out, the temperature is 2 ℃, and the minimum flow V of the obtained cooling liquid is 3.4L/min. If the minimum flow velocity v is designed to be 0.5m/s or more, the minimum height H is 2.0mm.
In this embodiment, the final channel width D is 66mm, and the channel height H is 2.8mm, so that the flow rate of the cooling liquid in the channel is uniform and the cooling liquid flows smoothly.
In order to ensure that the temperature of the cooling liquid of each battery pack is uniform, the liquid cooling pipelines are in parallel connection, namely the pipelines of the battery cabinets are connected in parallel, and the pipelines of the battery packs of the single battery cabinet are connected in parallel. As shown in fig. 6 and 7, the main liquid inlet pipe and the main liquid outlet pipe are transversely arranged on the upper sides of the battery cabinets, and the liquid inlet and outlet branch pipes of each battery cabinet extend vertically and are respectively connected with the liquid inlet and outlet branch pipes of the battery packs on different layers through the tee joint 10.
After determining the piping arrangement scheme, the piping flow is further determined. The flow requirements for each cell pack have been calculated above from the allowable temperature rise of the coolant flowing through the cell pack. In this embodiment, the flow requirement of each battery pack is 3.4L/min, i.e., the flow requirement of the battery pack branch line is 3.4L/min. By combining the number of the battery packs and the number of the battery cabinets, the flow requirement of the branch pipelines of the battery cabinets is 23.8L/min, and the flow requirement of the main pipeline is 120L/min.
Considering that the flow of the liquid cooling unit is required to be compatible with different energy storage scales, the final flow of the liquid cooling unit is selected to be 200L/min, namely, the design flow of the main pipeline, the battery cabinet pipeline and the battery pack pipeline is respectively 200L/min, 40L/min and 5.7L/min.
After the pipeline flow is determined, in order to ensure that the flow of the cooling liquid in the battery packs at different heights is balanced, the defect of insufficient flow of the battery packs at the lower layer is avoided, and the flow resistance of each battery pack can be changed by adopting variable-diameter designs for different branch pipelines. In order to reduce the design and manufacturing cost, the pipeline generally adopts a standardized pipeline, and the idea of reducing is to adopt an orifice, namely, a tee joint of a top battery pack and a bottom battery pack adopt different inner diameters. In this embodiment, the horizontal direction interface aperture of the tee on different layers increases from top to bottom or once every several layers. In the design scheme of the throttling hole, the inner diameters of a main pipeline, a battery cabinet branch pipeline and a battery pack branch pipeline are selected firstly, and then the inner diameter of a tee joint is determined.
The flow of coolant creates pressure losses, including path loss, reduced section loss, and expansion loss. For the top and bottom battery packs, the difference in path loss is the difference in path of the cooling liquid in the vertical direction; the loss of the reduced section and the expansion loss are losses flowing through the tee joint, and exist in the vertical direction and the horizontal direction.
The loss along the journey is as follows:
wherein lambda is the along-path resistance coefficient; l is the travel through which the liquid flows; d is the inner diameter of the pipeline; q is flow; s is the cross-sectional area.
In the formula (4), λ is related to the reynolds number Re:
the Reynolds number Re is:
wherein μ is a liquid viscosity and ethylene glycol is 0.00394 Pa.s.
Loss ΔP of reduced cross section by flowing through tee joint ξ1 Resistance coefficient xi 1 The method comprises the following steps:
wherein S is 1 Is the initial cross-sectional area; s is S 2 Is the outlet cross-sectional area.
Expansion loss Δp ξ2 Resistance coefficient xi 2 The method comprises the following steps:
Δp then ξ1 And DeltaP ξ2 The expression of (2) is:
in this embodiment, in terms of the loss along the path, 7 battery packs are provided in total for a single battery cabinet, the branch pipeline of the battery cabinet is divided into 7 sections, from top to bottom, referred to as 1 st section to 7 th section, and each section has a length l=280 mm. The loss along the path through segment 1 is the same for both the top and bottom layer battery packs, and is not a concern. The flow rates Q of the 2 nd section to the 7 th section are respectively 6Q 1 、5Q 1 ，…，Q 1 Wherein Q is 1 =5.7l/min. Substituting formula (5) and formula (6) can calculate Reynolds number Re and resistance coefficient lambda, and substituting formula (4) can calculate the path loss of each segment and accumulate to obtain total loss delta P λ_sum 。
In terms of reduced and enlarged loss of cross section, in the vertical direction, the coolant reaches the bottom cell pack through 6 more tees than the top cell pack, i.eThere are 6 sectional reductions and expansions, and the sectional reduction loss ΔP in the vertical direction can be obtained by the formulas (9) and (10) ξ1_sum_vert And an expansion loss Δp ξ2_sum_vert The method comprises the steps of carrying out a first treatment on the surface of the In the horizontal direction, the difference between the three-way inlet and the horizontal outlet and the difference between the horizontal outlet and the cross section of the battery pack branch pipeline generate shrinkage and expansion losses, and the shrinkage and expansion losses in the horizontal direction can be obtained through the formula (9) and the formula (10) and are delta P for the top battery pack ξ1_top_horiz And DeltaP ξ2_top_horiz Δp for bottom pack ξ1_bttm_horiz And DeltaP ξ2_bttm_horiz 。
In design, the pressure loss of the coolant flowing into the top and bottom cell packs should be the same, so there are:
ΔP λ_sum +ΔP ξ1_sum_vert +ΔP ξ2_sum_vert +ΔP ξ1_bttm_horiz +ΔP ξ2_bttm_horiz ＝ΔP ξ1_top_horiz +ΔP ξ2_top_horiz (11)
the variables of the formula (11) are the inner diameters (or sections) of the tee because the inner diameters of the main pipeline, the battery cabinet branch pipeline and the battery pack branch pipeline are selected in advance. In the embodiment, the inner diameters of the main pipeline, the battery cabinet branch pipeline and the battery pack branch pipeline are respectively selected to be 32mm, 16mm and 12mm; in order to reduce the manufacturing cost, the inner diameter of the inlet and the outlet in the vertical direction of the tee is selected to be 14mm, the inner diameter of the outlet in the horizontal direction of the tee at the bottom is selected to be 10mm, and then the variable in the formula (11) is only the inner diameter of the tee at the top in the horizontal direction, and the calculated result is 5.6mm in the example Wen Chuneng.
Therefore, the aperture of the tee joint in the horizontal direction in the single battery cabinet is gradually increased from 5.6mm to 10mm, and the average orifice aperture is about 7.8mm, so that the flow uniformity of each battery pack can be ensured. Considering that the tee joint has too many types, the pipeline cost and the production difficulty are too high, and finally 2 tee joint apertures are selected: the aperture of the upper layer 3 battery pack tee joint in the horizontal direction is 7mm, and the aperture of the lower layer 4 battery pack tee joint in the horizontal direction is 10mm.
The liquid cooling unit comprises a water pump and a compressor, and is used for pushing the cooling liquid to circulate, refrigerating the cooling liquid and radiating heat brought by the battery outside the prefabricated cabin. The main content of the liquid cooling unit type selection is water pump characteristic selection and refrigeration power selection.
The water pump characteristic selection mainly comprises the step of selecting a proper water pump model according to the flow-lift characteristic. On the basis of determining the parameters of the liquid cooling plate, the parameters of the liquid cooling pipeline and the flow requirements, the pressure drop of the cooling liquid flowing through the pipeline can be determined.
In this embodiment, it has been determined that the pipeline water inlet flow requirement is 200L/min, i.e., the water pump flow requirement is 200L/min. The pressure drop of the pipeline is difficult to obtain through theoretical calculation due to irregular flow channels. Through simulation, the pressure drop of the water inlet and the water outlet in the embodiment is 292.4kPa. The present embodiment selects a CM15 series of water pumps. For the pressure drop of 292.4kPa, selecting the maximum flow rate of the water pump 15m corresponding to the CM15-2 model 3 And/h (250L/min) meets the requirement, and the water pump can be operated near the flow rate to obtain higher efficiency.
The refrigeration power is selected according to the maximum heating power of the battery cell. In this embodiment, the maximum heating power of the single battery cell under the working condition of 0.5C is 12W, and the heating power can be obtained according to the number of battery packs and battery cabinets as shown in table 2.
Table 2 maximum heat generation power of cell stack
The refrigeration power should be greater than 27.72kW. Because the thermal management system is divided into 2 subsystems and 2 liquid cooling units are configured, the refrigerating power of each liquid cooling unit is greater than 13.86kW. In this example, 2 liquid cooling units of 15kW were used.
In this embodiment, a condensate water prevention design is also performed on the liquid cooling system.
1. Battery pack condensation-proof design
The integrated liquid cooling board in battery package box bottom, box temperature is less than ambient temperature during the refrigeration, easily produces the comdenstion water at the box surface when vapor in the air hits the box. The outer surface of the bottom of the battery pack is in direct contact with air, so that a heat preservation coating is sprayed on the lower surface of each battery pack to reduce the temperature difference between the lower surface of the battery pack and the air, and further reduce the generation of condensed water.
In the embodiment, the polyurethane foam heat-insulating coating is sprayed on the lower surface of the battery pack box body, the heat conductivity coefficient is less than or equal to 0.1W/(m.K), the coating thickness is more than or equal to 2.0mm, the temperature difference between the box body and air can be effectively reduced, and the condensate water is reduced.
2. Battery cabinet condensation-proof design
A drain groove is arranged above the front side of each battery pack to prevent top condensed water from directly dripping onto the high-low pressure connector on the front side of the battery pack. All the drainage tanks are communicated by a drainage pipe and led out of a battery cabin for placing a battery cabinet. When condensate drops to the drain channel, it can flow down the drain and eventually out of the battery compartment.
3. Battery compartment condensation prevention design
In this embodiment, the batteries are arranged with the utility compartment, and all of the battery cabinets are closely arranged in the battery compartment to reduce the air content in the battery compartment and thereby reduce the amount of water vapor. The waterproof grade of the battery compartment reaches IPX5, so that convection between outside air and air in the compartment is reduced, and excessive water vapor is prevented from entering the battery compartment; a dehumidifying air conditioner is arranged in the battery compartment.
4. Dehumidifying air-conditioning arrangement
Preferably, the battery compartment may also be provided with a dehumidifying air conditioner 9. The air conditioner is aimed at dehumidifying and cooling the environment instead of cooling the battery, thereby lowering the dew point temperature and preventing condensed water from being generated. In this embodiment, 4 air conditioners are uniformly arranged on the battery compartment door, as shown in fig. 3.
When designing the operation strategy of the dehumidification air conditioner, the aim of the dehumidification air conditioner is to adjust the dew point temperature to be lower than the temperature of the battery stack components, and the temperature of the battery stack is adjusted by the thermal management strategy, so that the operation strategy of the dehumidification air conditioner needs to be formulated by matching with the thermal management strategy.
In this embodiment, the operation states of the liquid cooling unit are divided into cooling, heating, and standby. Under heating conditions, the temperature of the battery pack and the liquid cooling pipeline is higher than the ambient temperature T ambt No condensed water is generated. Under the standby condition, the battery pack stands still or works, and the temperature is not lower than the ambient temperature T ambt . Due to the cooling liquidSelf-circulation, the temperature is similar to that of the battery pack, so that condensed water is not generated. Under refrigeration conditions, the temperature of the battery pack and the liquid cooling pipeline may be lower than the ambient temperature T ambt Therefore, condensed water may be generated. Therefore, one of the conditions for opening the dehumidifying air conditioner is the refrigeration of the liquid cooling unit.
The second condition of opening the dehumidifying air conditioner is that the dew point temperature is 15 ℃ higher than the lowest temperature of the liquid cooling pipeline, namely, the dew point temperature starts to be regulated when the dew point temperature is higher than 15 ℃. Referring to a dew point thermometer, one point corresponding to the dew point temperature of 15 ℃ is the ambient temperature T ambt =25 ℃, humidity rh=50%, and "dew point temperature is greater than 15 ℃" is "T ambt A subset of > 25℃or RH > 50% "is defined as" T ambt As the second condition of the dehumidifying air conditioner, the temperature of the dew point is higher than 25 ℃ or RH is higher than 50%, and the dehumidifying air conditioner can be started in advance when the dew point temperature is close to 15 ℃.
After the air conditioner is started, the control target is set as an environmental temperature target T through simulation analysis of the air conditioner refrigerating capacity screening process ambt set =22 ℃, humidity target RH set ＜60％。
In order to avoid frequent start-up and shut-down of the air conditioner, the shut-down condition is not a non-set of start-up conditions, but is taken as "stand-by of the liquid cooling unit".
Therefore, as shown in fig. 8, in the process of performing thermal management on the battery energy storage system, the operation of the dehumidifying air conditioner is controlled as follows:
1) When the liquid cooling unit is refrigerating, and the ambient temperature T ambt When the temperature is more than 25 ℃ or the humidity RH is more than 50%, starting a dehumidifying air conditioner;
2) Setting the control target as an ambient temperature target T ambt_set =22 ℃, humidity target RH set < 60%, i.e. when the ambient temperature T ambt When the temperature is not higher than 22 ℃ and the humidity RH is less than 60 percent, turning to the step 3);
3) Judging whether the liquid cooling unit stands by, if so, closing the dehumidifying air conditioner, otherwise, continuing to execute the step 2).
The method is further illustrated by a specific example.
In order to verify the actual operation effect, the refrigerating and heating conditions in the actual operation of the liquid cooling system are selected for analysis. In the test, the data of the battery management system is called, and the temperature of the battery cell, the temperature of the water outlet and the temperature of the water inlet of the liquid cooling unit are analyzed in a key way.
1. Refrigeration condition
During 9h of a certain day of 12 of 2021, the battery energy storage system performs a complete charge-discharge cycle, and the charge-discharge multiplying power is 0.5C of the designed maximum charge-discharge multiplying power. During which the thermal management system automatically enters a cooling mode.
The current, state of charge (SOC), cell temperature, and inlet/outlet fluid temperature curves of the subsystems 1 and 2 are shown in fig. 9.
From the above curves, it can be concluded that:
(1) About time t=0.5 h, the highest temperature of the battery cell is more than 30 ℃, and the unit starts refrigeration; about t=6 hours, the highest temperature of the battery cell is less than 25 ℃, and the unit stands by.
(2) In the refrigerating process, the outlet temperature of the unit fluctuates at 15-22 ℃, the temperature of the battery cell is maintained below 34 ℃, and the battery cell operates normally.
(3) The maximum temperature difference of the battery core is not more than 3 ℃.
2. Heating working condition
During a period of 96 hours at 12 months 2021, the battery energy storage system is stationary, but due to the low air temperature, the liquid cooling system automatically enters a heating mode during this period.
The current, SOC, cell temperature and inlet-outlet liquid temperature curves of the subsystems 1 and 2 are shown in figure 10.
From the above curves, it can be concluded that:
(1) About time t= 72.68h, the lowest temperature of the battery cell of the subsystem 1 is less than 15 ℃, and the unit 1 is started for heating; about t=80 h, the lowest temperature of the battery cell is more than 20 ℃, and the unit 1 stands by. Similarly, the times for starting and stopping heating of the unit 2 are approximately t=36.5 h and t=43.9 h.
(2) In the standing process, the temperature drop rate of the battery cell is stable and maintained at 0.2 ℃/h under the influence of the ambient temperature.
(3) In the heating process, the heating rate is stabilized at about 0.95 ℃/h, the temperature of the battery cell is maintained at 14-22 ℃, and the battery cell operates normally.
(4) The maximum temperature difference of the battery core is not more than 3 ℃.
Compared with air cooling, the cost of the liquid cooling scheme provided by the method is increased. The cost increase is mainly that a liquid cooling unit, a liquid cooling pipeline and a liquid cooling plate are adopted in the liquid cooling scheme. According to measurement, the cost of the embodiment is increased by about 10 ten thousand yuan compared with that of air cooling. But the liquid cooling has high heat conduction efficiency and is advantageous in the aspect of electric power consumption. In addition, the liquid cooling mode omits an air duct, reduces the occupied area of the battery energy storage system, and improves the energy density of the system.
In the aspect of electric power consumption, taking a 2MWh energy storage system as an example, the air cooling and liquid cooling refrigerating capacity requirements are basically the same. The electric power consumption can be calculated by combining the energy efficiency ratio of mainstream products in the market. Furthermore, in the air cooling scheme, a single air-cooled battery is provided with a fan, the electric power consumption of the single fan is about 15W, and the 2MWh system is provided with about 160 battery packs. The power consumption of the obtained electricity is 17.4kW compared with that of the obtained electricity in the table 3, the power consumption of the air cooling scheme is 12kW, and the power consumption of the liquid cooling scheme is reduced by 31%.
Table 3 comparison of electric Power consumption of 2MWh air-cooled and liquid-cooled energy storage systems
In terms of energy density improvement, taking a 40 inch standard prefabricated cabin as an example, the prefabricated cabin is 12190 multiplied by 2438 multiplied by 2896mm in size, and the reference sizes of the air cooling and liquid cooling battery cabinets are 12007252300mm and 76610872440mm respectively. Because the air-cooled battery cabinet is top air inlet, front air outlet, the top and the front need to reserve enough air channel space, and 14 air-cooled battery cabinets can be maximally arranged in the container, and the total electric quantity is about 2.8MWh. The liquid cooling pipelines of the liquid cooling battery cabinets occupy small space, the electric cabinets can be closely arranged, and the maximum 20 liquid cooling battery cabinets can be arranged, so that the total electric quantity is about 4MWh. Therefore, the energy density of the liquid cooling energy storage system can be increased by 43% compared with that of the wind energy storage system.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the invention in any way, and any person skilled in the art may make modifications or alterations to the disclosed technical content to the equivalent embodiments. However, any simple modification, equivalent variation and variation of the above embodiments according to the technical substance of the present invention still fall within the protection scope of the technical solution of the present invention.
Claims (10)
1. The heat management method of the battery energy storage system is characterized in that when the temperature of the battery exceeds a set range, the battery management system controls a liquid cooling unit of a liquid cooling system to work, and the temperature of the battery is controlled to be within a range of 20-25 ℃; the method comprises two working modes of refrigeration and heating:
refrigeration operation mode: when the single battery is at the highest temperature T cell_max >T 1 When the battery management system issues instructions to the liquid cooling unit, the instructions comprise a liquid temperature target value T set1 And return difference delta T margin1 The method comprises the steps of carrying out a first treatment on the surface of the The instruction is maintained until the highest temperature T of the single battery cell_max Cooling to 25 ℃; if the actual liquid temperature of the outlet of the liquid cooling unit is higher than the target value by delta T during the instruction maintenance period margin1 Starting refrigeration; if the actual liquid temperature of the outlet of the liquid cooling unit is lower than the target value by delta T margin1 Stopping refrigeration; frequent starting and closing of the unit are prevented through setting of return difference;
heating operation mode: when the minimum temperature T of the single battery cell_min <T 2 When the battery management system issues instructions to the liquid cooling unit, the instructions comprise a liquid temperature target value T set2 And return difference delta T margin2 The method comprises the steps of carrying out a first treatment on the surface of the The instruction is maintained until the highest temperature T of the single battery cell_min Raising the temperature to 20 ℃; and during the instruction maintaining period, the heating start-stop is controlled by the return difference in the same way as the refrigerating process.
2. A method of thermal management of a battery energy storage system according to claim 1, wherein for a cooling mode of operation, T 1 ＝30℃，T set1 ＝18℃，ΔT margin1 =3deg.C, i.e. when the cell is at the highest temperature T cell_max >At 30 ℃, the battery management system issues instructions to the liquid cooling unit, including a liquid temperature target value T set1 =18 ℃ and return difference Δt margin1 ＝3℃The method comprises the steps of carrying out a first treatment on the surface of the During the instruction maintaining period, the liquid cooling unit is started to cool when the liquid outlet temperature is higher than 21 ℃, and the liquid cooling unit is closed to cool when the liquid outlet temperature is lower than 15 ℃;
for heating operation mode, T 2 ＝15℃，T set2 ＝30℃，ΔT margin2 =5 ℃, i.e. when the cell has the lowest temperature T cell_min <At 15 ℃, the battery management system issues instructions to the liquid cooling unit, including a liquid temperature target value T set2 =30deg.C and return difference ΔT margin2 =5 ℃; and during the instruction maintaining period, starting heating when the liquid cooling unit liquid outlet temperature is lower than 25 ℃, and stopping heating when the liquid cooling unit liquid outlet temperature is higher than 35 ℃.
3. The method for thermal management of a battery energy storage system according to claim 1, wherein the liquid cooling system comprises liquid cooling plates, liquid cooling pipelines and liquid cooling units, the number of the liquid cooling plates is adapted to the number of the battery modules in the battery energy storage system, each liquid cooling plate is respectively arranged on the lower side of a corresponding battery module and contacts with the bottom of a battery core, and the liquid cooling plates and the battery modules are integrated in a battery pack; the liquid cooling pipeline comprises a main liquid inlet pipe, a battery cabinet liquid inlet branch pipe, a battery pack liquid outlet branch pipe, a battery cabinet liquid outlet branch pipe and a main liquid outlet pipe, wherein the liquid inlet and outlet ports of each liquid cooling plate are respectively connected with the battery pack liquid inlet and outlet branch pipes, all the battery pack liquid inlet and outlet branch pipes of a single battery cabinet are respectively connected with the battery cabinet liquid inlet and outlet branch pipes in parallel, all the battery cabinet liquid inlet and outlet branch pipes are respectively connected with the main liquid inlet and outlet pipes in parallel, and the main liquid inlet and outlet pipes are connected with the liquid cooling unit.
4. A method of thermal management of a battery energy storage system according to claim 3, wherein the battery energy storage system comprises k subsystems, each subsystem is composed of n battery cabinets in parallel, the n battery cabinets are arranged side by side in the transverse direction, each battery cabinet is composed of m battery packs in series, the m battery packs are stacked vertically layer by layer, each battery pack comprises a x b series-connected battery cells, and the a x b series-connected battery cells are arranged in a row a and a column b in an array in the horizontal direction; the liquid cooling system is provided with k sets of liquid cooling pipelines and k liquid cooling units corresponding to k subsystems.
5. The method for thermal management of a battery energy storage system according to claim 4, wherein the liquid cooling plate is provided with a U-shaped flow channel, the U-shaped flow channel is composed of a liquid inlet side flow channel, a bottom flow channel and a liquid outlet side flow channel, and the liquid inlet side flow channel and the liquid outlet side flow channel are respectively connected with a battery pack liquid inlet branch pipe and a battery pack liquid outlet branch pipe; the liquid inlet side flow channel comprises a plurality of liquid inlet branch flow channels, the liquid outlet side flow channel comprises a plurality of liquid outlet branch flow channels, and all the liquid inlet branch flow channels are converged into the bottom flow channel and then distributed to all the liquid outlet branch flow channels; all the liquid inlet branch flow passages, the bottom flow passages and the liquid outlet branch flow passages are contacted with the bottoms of all the electric cores in the battery pack so as to exchange heat with all the electric cores, and heat dissipation of all the electric cores is realized.
6. The method of claim 5, wherein if the battery pack is provided with odd columns of cells, i.e. b is odd, the liquid inlet side flow channel further comprises a liquid inlet half branch flow channel with a flow channel width half of that of the liquid inlet branch flow channel, the liquid outlet side flow channel further comprises a liquid outlet half branch flow channel with a flow channel width half of that of the liquid outlet branch flow channel, and the liquid inlet half branch flow channel and the liquid outlet half branch flow channel are both in contact with the bottoms of the cells in the middle column.
7. The method of claim 5, wherein the widths of the liquid inlet branch flow channel, the liquid outlet branch flow channel and the liquid outlet branch flow channel are calculated by the following formula:
wherein D is the width of the flow channel, W is the thickness of the single cell, A is the area of the heat exchange surface, and the heat exchange surface is calculated by the following formula:
P cell ＝h·ΔT·A
wherein P is cell The heat exchange power of a single cell is that h is the heat transfer coefficient of the liquid cooling plate and the cooling liquid,delta T is the temperature difference between the cooling liquid and the wall surface of the liquid cooling plate;
the height of the flow channel in the liquid cooling plate is calculated by the following formula:
P pack ＝cρVΔT rise ＝cρvH·zD·ΔT rise
wherein P is pack The maximum heating power of the battery pack is calculated by C, rho, V, delta T, and the specific heat capacity of the cooling liquid rise For the temperature rise of the cooling liquid, v is the flow velocity of the cooling liquid, H is the height of the flow channel, and z is the flow channel coefficient determined according to the number of the branch flow channels.
8. The method for thermal management of a battery energy storage system according to claim 3, wherein the main liquid inlet pipe and the main liquid outlet pipe are transversely arranged on the upper side of the battery cabinet, and the liquid inlet branch pipe and the liquid outlet branch pipe of each battery cabinet extend vertically and are respectively connected with the liquid inlet branch pipe and the liquid outlet branch pipe of the battery pack on different layers through tee joints; the horizontal direction interface aperture of the tee on different layers is increased layer by layer from top to bottom or once every other a plurality of layers to reduce the flow resistance of the lower layer pipeline and balance the flow of the cooling liquid in the battery packs on different heights.
9. The method of claim 3, wherein a thermal insulation coating is sprayed on the lower surface of each battery pack to reduce the temperature difference between the lower surface of the battery pack and air, thereby reducing the generation of condensed water; a drainage groove is uniformly distributed above the front side of each battery pack so as to prevent condensed water at the top from dropping onto the high-low pressure connector at the front side of the battery pack; all the drainage tanks are communicated by drain pipes and led out of a battery cabin for placing a battery cabinet; all the battery cabinets are closely arranged in the battery compartment so as to reduce the air content in the battery compartment and further reduce the water vapor quantity; the waterproof grade of the battery compartment reaches IPX5, so that convection between outside air and air in the compartment is reduced, and excessive water vapor is prevented from entering the battery compartment; a dehumidifying air conditioner is arranged in the battery compartment.
10. The method for thermal management of a battery energy storage system according to claim 2, wherein the operation of the dehumidification air conditioner is controlled in the thermal management of the battery energy storage system as follows:
1) When the liquid cooling unit is refrigerating, and the ambient temperature T ambt When the temperature is more than 25 ℃ or the humidity RH is more than 50%, starting a dehumidifying air conditioner;
2) Setting the control target as an ambient temperature target T ambt_set =22 ℃, humidity target RH set < 60%, i.e. when the ambient temperature T ambt When the temperature is not higher than 22 ℃ and the humidity RH is less than 60 percent, turning to the step 3);
3) Judging whether the liquid cooling unit stands by, if so, closing the dehumidifying air conditioner, otherwise, continuing to execute the step 2).
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| CN116666838A (en) * | 2023-07-31 | 2023-08-29 | 四川沃轮电气制造有限公司 | Thermal management method of liquid-cooled energy storage system |
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| CN116666838A (en) * | 2023-07-31 | 2023-08-29 | 四川沃轮电气制造有限公司 | Thermal management method of liquid-cooled energy storage system |
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