2.4 PCM cooled BTMS
PCM cooling principle and characteristics: As an alternative to active cooling systems, phase change material (PCM) cooling absorbs and stores a large amount of thermal energy during the phase change process to regulate battery temperature, provide passive thermal management, reduce coolant management risks, simplify thermal management systems, improve reliability, help maintain battery performance, extend lifespan, and enhance safety. But after complete melting, PCM’s ability to absorb heat decreases, and it often needs to be combined with active cooling systems (such as liquid cooling or air cooling), especially in long-term high-power operation or high-temperature environments.
Design and Effectiveness of Hybrid Systems
PCM air cooling hybrid system: Combining PCM with air cooling can reduce battery pack temperature gradients and hotspots. For example, hybrid BTMS combines PCM with air cooling and uses biomimetic variable cross-section fins to reduce power consumption through delayed air cooling strategy; The enhancement effect of honeycomb design on thermal storage and cooling system; PCM covers prismatic battery cells and improves thermal performance through innovative design of Z-shaped air channels.
PCM liquid cooling hybrid system: The combination of PCM and liquid cooling has many advantages. The hybrid system of wavy microchannel cold plate and PCM improves the active and passive cooling of cylindrical lithium-ion battery packs, maintaining uniform temperature; The passive thermal regulator that uses composite phase change materials to control the volume change of cooling water flow reduces the maximum battery temperature, improves temperature uniformity and fluctuation control, and demonstrates the potential of passive thermal management systems to improve battery performance and lifespan under different operating conditions. This hybrid system also has the advantages of high heat transfer efficiency, good temperature uniformity, high reliability, energy saving, scalability, and customization, and is suitable for various battery application scenarios.
2.5 Thermal electric cooler BTMS
Principle and advantages of thermoelectric cooling: Thermoelectric coolers (TECs) use the Peltier effect to dissipate heat in the medium through electric current. They have the advantages of lightweight, compact design, low noise, simple operation, and long service life, and are widely used in many industries. Thermoelectric generators (TEGs) utilize the Seebeck effect to convert thermal energy into electrical energy.
Application and achievements of TEC in BTMS: Based on TEC, the innovative battery pack design of BTMS combines acrylic container, copper bracket, thermoelectric cooling system, and liquid and air circulation, significantly improving thermal management and reducing battery temperature; TEC-TEG hybrid BTMS, combined with thermoelectric cooling and power generation with forced air, effectively reduces the maximum surface temperature of a single lithium iron phosphate (LiFePO ₄) battery.
3 Discussion and Summary
3.1 Summary of Key Findings
Air cooling: Air cooling methods include natural convection and forced convection, which have the advantages of simplicity, low cost, and easy maintenance, but their efficiency is significantly reduced in high-temperature environments. Improvement measures such as wind duct improvement (X-shaped, honeycomb structure, multiple inlet/outlet design, etc.), battery arrangement improvement (such as Z-shaped and staggered arrangement system), and addition of fin structure (radial fins and guide plates, etc.) can significantly improve the performance of air-cooled BTMS, help maintain battery temperature within the optimal range, and enhance the overall performance and safety of lithium-ion batteries for electric vehicles.
Liquid cooling: Liquid cooling methods (including liquid indirect cooling LIDC-BTMS and liquid direct cooling LDC-BTMS) are very effective for high demand applications such as electric vehicles, and their heat transfer ability is superior to air cooling, making them suitable for high-power density scenarios. Cold plate optimization (such as spider web, mini channel, and diamond channel cold plates) and cooling channel improvement (optimizing fluid flow, using wavy microchannels, increasing heat dissipation surface area, and using advanced materials) can improve cooling efficiency. The hybrid system combining PCM and liquid cooling can further enhance temperature control capabilities, ensuring stable battery performance under extreme conditions.
PCM cooling: PCM cooling provides passive thermal management, absorbs heat during phase transition, and can effectively maintain consistent battery temperature. However, active cooling system needs to be supplemented for long-term high-power operation. PCM configurations with different shapes (square, circular, rectangular) can optimize thermal management within specific temperature ranges. Hybrid PCM systems combined with air cooling or liquid cooling can improve temperature regulation and energy efficiency, especially at high discharge rates. Innovative designs (such as advanced fin structures and optimized configurations) can enhance heat transfer efficiency, reduce temperature differences, and extend battery operating time, making them suitable for various application scenarios.
Thermoelectric cooling: Thermoelectric coolers (TECs) effectively control temperature using the Peltier effect, and have advantages such as compactness, low noise, and long lifespan, making them suitable for BTMS. The hybrid TEC-TEG system utilizes the advantages of TEC and TEG to significantly improve cooling efficiency and reduce battery temperature; The active passive hybrid system combining TEC with PCM or fins enhances temperature regulation and energy efficiency, and is effective at high discharge rates; Innovative TEC designs, such as dual active cooling systems and TEC with cold plates, provide advanced thermal management solutions to maintain battery temperature within the optimal range under extreme conditions. By integrating with other cooling technologies and optimizing system design, battery performance and safety can be significantly improved, making it suitable for high demand scenarios such as electric vehicles.
3.2 Technical and Economic Comparative Analysis of Cooling Methods
Evaluation index definition: It defines cooling efficiency (CE, measuring the effectiveness of cooling methods in maintaining battery temperature within the optimal range), temperature uniformity (TU, evaluating the ability of cooling methods to maintain a uniform distribution of battery pack temperature), maximum temperature reduction (MTR, the degree to which cooling methods reduce the highest battery temperature), energy consumption (EC, the energy required to maintain the optimal battery temperature), system complexity (SC, the complexity of implementing and maintaining cooling methods), response time (RT, the speed at which cooling methods adapt to changes in thermal load), cost-effectiveness (C-E, the relative relationship between the total cost and performance benefits of implementing and operating cooling methods), scalability (S, the ease of adapting cooling methods to different battery sizes and configurations), safety Regarding reliability (SR, Key terms such as the degree to which cooling methods enhance battery safety and operational reliability are used to evaluate the performance, efficiency, and applicability of four cooling methods (air cooling, liquid cooling, PCM cooling, and thermoelectric cooling).
Comparison of Characteristics of Various Methods
The air-cooled system has high cost-effectiveness, low initial and maintenance costs, and is suitable for applications that require moderate cooling performance and pursue system simplicity. However, its efficiency is lower under high heat loads.
The liquid cooling system has high cooling efficiency and reliability, suitable for high demand applications such as electric vehicles, but it is costly and complex, involving energy consumption.
The PCM cooling method has good cost-effectiveness, low operating costs, moderate system complexity, and is suitable for applications that require continuous thermal management and low energy consumption, such as passive cooling scenarios.
Thermoelectric cooling method has high performance and precise control, suitable for high-end applications with strict temperature management requirements, but it has high costs and energy consumption.
Selection criteria and advantages of hybrid systems: Choosing the appropriate cooling method depends on specific application requirements, including performance, cost constraints, system complexity, and operating conditions. A hybrid system combined with multiple cooling methods can leverage the advantages of each method to achieve optimal performance and cost-effectiveness.