Design of a Battery Cooling System for Hybrid Electric Aircraft

A battery thermal management system (BTMS) for a hybrid electric aircraft is designed. Hot-day takeoff conditions are assumed, resulting in an ambient temperature higher than the allowed battery temperature. Thus, a heat pump has to be employed in the BTMS. All available heat pump technologies are assessed and compared. In a qualitative downselection process, thermoelectric cooling is chosen as heat pump technology. A computational model of the thermoelectric modules (TEMs), as well as a finned ram air heat exchanger with a puller fan (HEX) as heat sink, and a simple heat pipe model for heat acquisition from the battery are developed. Sensitivity analyses of the TEM and HEX models are conducted for comprehension of the relevant design variables. Finally, a BTMS is designed and optimized for a 19-seat hybrid electric aircraft with an all-electric design mission and a combustion engine for range extension. The temperature deviation from the International Standard Atmosphere, the battery operating temperature, and the battery efficiency span a three-dimensional design space rather than being defined to three discrete values. The most adverse combination of these three parameters results in an optimized BTMS that increases the maximum takeoff mass of the aircraft by 16% without the consideration of any snowball effects, whereas the most advantageous combination leads to a 2% increase.