Switchable Heat Pipes for Eco-Friendly Battery Cooling in Electric Vehicles: A Life Cycle Assessment

Abstract

Battery thermal management systems (BTMSs) ensure that lithium-ion batteries (LIBs) in electric vehicles (EVs) are operated in an optimal temperature range to achieve high performance and reduce risks. A conventional BTMS operates either as an active system that uses forced air, water or immersion cooling, or as a complete passive system without any temperature control. Passive systems function without any active energy supply and are therefore economically and environmentally advantageous. However, today’s passive BTMSs have limited cooling performance, which additionally cannot be controlled. To overcome this issue, an innovative BTMS approach based on heat pipes with an integrated thermal switch, developed by the Fraunhofer Cluster of Excellence Programmable Materials (CPM), is presented in this paper. The suggested BTMS consists of switchable heat pipes which couple a passive fin-based cold plate with the battery cells. In cold state, the battery is insulated. If the switching temperature is reached, the heat pipes start working and conduct the battery heat to the cold plate where it is dissipated. The environmental benefits of this novel BTMS approach were then analysed with a Life Cycle Assessment (LCA). Here, a comparison is made between the suggested passive and an active BTMS. For the passive system, significantly lower environmental impacts were observed in nearly all impact categories assessed. It was identified as a technically promising and environmentally friendly approach for battery cooling in EVs of the compact class. Furthermore, the results show that passive BTMS in general are superior from an environmental point of view, due their energy self-sufficient nature.

Keywords

• electric vehicles
• lithium-ion batteries
• battery thermal management system
• switchable heat pipes
• programmable materials
• life cycle assessment