Next Generation Car: Coupled Thermochemical Reactionsfor Preheating Vehicle Components

The German Aerospace Center has merged a wide range of technological research and development for future cars in a project called “Next Generation Car”. Within this project, thermal energy storage for improving the efficiency in future vehicles is investigated. This work focuses on thermochemical energy storage able to produce heat even at low ambient temperatures (-20 … +20°C). This heat can be used to preheat the battery for higher electrical power and less degradation. Based on the absorption and desorption of hydrogen between two metal hydrides, the storage is able to produce heat from ambient temperature. Although metal hydrides can react fast even at low temperatures, no experimental data of coupled metal hydride reactions below freezing point and at relevant scale is available in literature. For the development of thermochemical energy storages in future vehicle concepts with high thermal output powers, experimental investigations regarding the main influence factors are needed. Therefore, an experimental test rig of coupled metal hydrides was built and tested at vehicle boundary conditions. Charging by low level thermal energy (130°C), the results showed high thermal power outputs even at low discharging ambient temperatures. The variation of the ambient temperature showed a significant influence on the thermal power. The values ranged from 0.6 kW/kgMH at -20°C up to 1.6 kW/kgMH at +20°C. These are the highest values reported in literature so far.