Modeling and analysis of liquid-cooling thermal management of an in-house developed 100 kW/500 kWh energy storage container consisting of lithium-ion batteries retired from electric vehicles

As electric vehicles (EVs) are gradually becoming the mainstream in the transportation sector, the number of lithium-ion batteries (LIBs) retired from EVs grows continuously. Repurposing retired EV LIBs into energy storage systems (ESS) for electricity grid is an effective way to utilize them. However, the potential safety hazard of retired EV LIBs in echelon utilization poses to become a major concern nowadays. In this work is considered an in-house developed 100 kW/500 kWh ESS containing different types of retired EV LIBs. A self-developed thermal safety management system (TSMS), which can evaluate the cooling demand and safety state of batteries in realtime, is equipped with the energy storage container; a liquid-cooling battery thermal management system (BTMS) is utilized for the thermal management of the batteries. To study the performance of the BTMS, the temperature variation and temperature difference of the LIBs in the process of charging and discharging are experimentally and numerically analyzed. With a self-developed full-scale thermal-fluidic model, the temperature and temperature inconsistency of the 100 kW/500 kWh ESS under different coolant flow rates and different ambient temperatures are simulated. The experimental results corroborate the effectiveness of the liquid cooling BTMS; the maximum temperature rise of the batteries during the discharging and charging processes is less than 3 degrees C and 5 degrees C, respectively, and the maximum temperature difference between the batteries is always less than 2 degrees C. The simulation results show that the liquid cooling system can significantly reduce the peak temperature and temperature inconsistency in the ESS; the ambient temperature and coolant flow rate of the liquid cooling system are found to have important influence on the ESS thermal behavior. The developed ESS prototype and the full-scale thermal-fluidic model are combined to construct a research platform for future thermal safety study on the echelon utilization of retired EV LIBs.