Experimental and numerical analysis of holistic active and passive thermal management systems for electric vehicles: Fast charge and discharge applications

Lithium-ion capacitors (LiCs) are commonly used as power sources for electric vehicles (EVs) due to the combined advantages of electric double-layer capacitors (EDLCs) and lithium-ion batteries (LiBs) comprising high energy density, high power density, and long lifetime. However, the performance of the LiCs is susceptible to temperature. Therefore, a robust thermal management system (TMS) is crucial for EVs to operate efficiently and safely. In this work, holistic active and passive TMSs are designed to control the maximum temperature of the cell. In this regard, an air-cooled TMS (ACTMS) and a compact liquid-cooled TMS (LCTMS) are among the active cooling systems, where pure paraffin phase change material (PCM), PCM with added aluminum mesh grid foil (PCM-Al), PCM with an added heat sink (PCM-HS), and heat pipe cooling system (HPCS) are the investigated passive TMSs. Moreover, the experimental results are verified against numerical analysis using a computational fluid dynamics (CFD) software, COMSOL Multiphysics. The most efficient active and passive cooling systems are then selected in the CFD simulations to make a robust hybrid TMS for a module of LiC cells. The results exhibit that the LCTMS has the best performance where the maximum temperature of the cell is controlled at 32.5 ?, which shows the reduction of 41.2% compared to the natural convection (NC) case study. The PCM-HS has the best performance among the passive cooling systems, decreasing 38.3% compared to the NC. Moreover, the hybrid TMS decreases the maximum temperature by 50.1% while uniformizing the temperature along with the module by keeping the temperature difference below 4.5 ? between the coldest and hottest points on the cell.

Automated summary

This study designs comprehensive active and passive thermal management systems to control the maximum temperature of lithium-ion capacitor cells. Experimental results and numerical analysis show that the liquid-cooled thermal management system performs the best, reducing the maximum temperature by 41.2%. Among the passive cooling systems, the heat sink thermal management system achieves the best performance, reducing the temperature by 38.3%. Lastly, the hybrid thermal management system decreases the maximum temperature by 50.1% and ensures a temperature difference of less than 4.5℃ between the coldest and hottest points on the battery module.