Experimental Investigation and Evaluation of a Directly Heated High-Temperature Solid Media Thermal Energy Storage System for Cabin Heating in Battery Electric Vehicles

Thermal management of battery electric vehicles (BEVs) at low ambient temperatures increases battery energy consumption due to electric heating and reduces driving range. Thermal energy storage (TES) systems mitigate this issue by decoupling heat generation from heat demand. During charge, integrated electrical resistance heaters inside the TES system are used to increase the storage medium temperature, while a bypass operation controls the TES air outlet temperature for discharging. However, these heating systems limit the effective heating power or increase the risk of thermally induced stresses due to indirect heat transfer and localized heat sources. To overcome such limitations, a directly electrically heated solid media TES system based on a SiSiC honeycomb structure was designed and experimentally investigated, with the honeycomb simultaneously serving as both the heating element and storage medium. For this purpose, a test rig was constructed to characterize the electrothermal charging and thermal discharge behavior. The results confirm stable electrical charging with low contact resistance enabled by metallized honeycomb side faces and homogeneous heating to relevant operating temperatures up to 600 °C. Simultaneously, thermal utilizations of over 90% relating to the stored thermal energy is reached due to the effective heat transport in the honeycomb structure during convective discharging. Despite the small dimensions of the test rig with relatively high heat losses, gravimetric and volumetric storage densities of up to 200 Wh/kg and 385 kWh/m3, respectively, were achieved with regard to the honeycomb. Overall, the successfully validated models and experimental findings demonstrate that efficient electrothermal charging and thermal discharge can be achieved within one multifunctional component, providing a solid basis for further optimization and scaling of TES systems as an alternative heat supply in BEVs.