Research Projects

Current electric vehicles (EVs) employ lithium-ion batteries for energy storage owing to their high energy density. The battery kinetics can drive chain reactions leading to heat generation, which could develop into a fire or explosion, posing a risk to the safety of passengers. An efficient thermal management system is thus crucial for maintaining a safe environment inside EVs by extracting the generated heat away from batteries. Most EV companies today employ air-based cooling systems since they are cost-friendly. Low specific heat of air inhibits the cooling system from extracting heat faster in case of thermal runaway. The PI proposes utilizing an adaptive cooling system encompassing air and phase change material (PCM). This hybrid approach relies on sensible cooling for regular operation and latent cooling during thermal runaway. Usually, PCMs are embedded with fins to compensate for their low thermal conductivity and weak structural stability. The matrix thus formed is attached to a heat sink to dissipate the heat into the ambient. The PI proposes developing a control system that monitors the PCM's temperature and adjusts the airflow over the heat sink. The airflow is maintained so that only sensible heat from the matrix will be utilized during regular operation. In the presence of a trigger from the early warning alarm indicating the possibility of thermal runaway, the airflow is adjusted to operate the PCM in the latent cooling mode. Research Plan 1.Fabrication of battery hardware simulators: Using actual lithium-ion batteries is often time-consuming due to the required relaxation times between charging and discharging cycles. The PI proposes to develop an electrical resistance based heating element with a controllable heat generation rate. Thermal equivalence of the actual battery and the simulator will be justified through thermal imaging. 2.Simulation and design for PCM matrix: Simulations to identify the optimal composition of PCM and embedding fins will be performed to optimize the performance of the matrix. A modular design will be developed to accommodate each battery in the matrix. A heat sink will also be designed considering the airflow from the passenger cabin. 3.Training of control algorithm: Based on the phase change temperature of the matrix, the algorithm will be trained to adjust the airflow rate over the heat sink to maintain the temperature of PCM, depending on the operating regime of the batteries. 4.Visualisation studies to determine the cycle life of the PCM matrix: Thermal imaging of the PCM will ensure the temperatures are within the operating limits. The response time and heat extraction rate will be compared with the simulations, and the cycle life of PCM will be experimentally determined. 5.Testing of the algorithm: Current EV policies require a 5-minute evacuation time for passengers in case of thermal runaway. PCM's delay effectiveness will be quantified by comparing it with an air-based cooling system.