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.

Thermal switches contribute to efficient and safe thermal management of components and overall systems in various technical applications by actively controlling heat transfer in response to varying thermal loads and ambient conditions. Heat pipes are passive heat transfer devices constituting an integral part of various thermal management systems such as in spacecraft or consumer electronics thermal control. Heat pipes also form a promising approach for thermal switches due to their high effective thermal conductivity. In this paper, a wickless copper-water heat pipe based thermal switch with an electromagnetic linear actuator is presented. The magnetically actuated motion of a plunger integrated into the heat pipe affects the latent heat transport cycle leading to a switchable heat transfer. Thermal measurements conducted to determine the total thermal resistance of the heat pipe demonstrate the efficacy of the thermal switch. It was found that the thermal resistance of the heat pipe was increased by up to 53% in off state while the heat pipe performance in on state was not significantly affected by the integrated mechanism.

The lack of suitable connectors for thin‐walled carbon concrete elements with their known resource and material saving properties still represents a major obstacle for practical application. On top, the on‐site installation remains a labor‐intensive task. To overcome this limitation, we report the development of an active assembly connector that enables simple and safe installation of carbon concrete façade elements and increases assembly efficiency. Moreover, the active assembly features permit an assembly without physical access to the connector, called blind assembly. Its concept is based on the recovery expansion of iron‐based shape memory alloys (Fe‐SMA). This paper presents material characteristics such as recovery stress and strain of the Fe‐SMA in compression. The connector concept uses an anchor rail that blocks the recovery extraction of a Fe‐SMA‐fastener to produce a stable, frictional and linear connection. Tensile tests show the impact of design parameters and high pull‐out forces with sufficient design. Also, ongoing long term tensile tests show small creep, so far. The anchor channels integrate well with carbon concrete façade panels. The heating concept with heating cartridges works well, even under cold winter conditions. Wind test results exceed requirements. Finally, a field test shows excellent installation results and proves the ease of assembly as well as the ability for blind assembly.