Thermal Energy Storage Concept Increases Efficiency of Electric Cars

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While fuel-driven vehicles can use the engine’s waste heat to heat the interior, the traction battery in electric cars also supplies the heater, thereby cutting the vehicle’s range by up to half. Scientists at the German Aerospace Center (DLR, Deutsches Zentrum für Luft- und Raumfahrt), together with the Institute of Material Physics in Space (Cologne), Audi and the Bavarian Center for Applied Energy Research, have now showcased a heat accumulator. It is meant to reduce the influence of the heater on the range of electric vehicles at low ambient temperatures. 

Metallic latent heat accumulators have a high energy density and thermal conductivity. They absorb so-called latent or hidden heat during a phase change, for example from solid to liquid, and can release the heat again. This principle is known from small pocket warmers, which can store considerable energy in a small mass.

Duotherm designed to improve overall efficiency

"By using metallic latent heat accumulators, we have succeeded in designing an energy storage system that can store heat at a very high energy level and hence relieve the traction battery from heating the vehicle interior," says project manager and DLR scientist Mirko Klein Altstedde. The Duotherm concept is intended to improve the efficiency of electric vehicles in addition to increasing the range, by absorbing braking energy, reducing charge losses or cooling the battery with an additional high-temperature accumulator. The system should be cheaper than having a second battery in the vehicle.

The system is to be developed for serial production in the next two to three years. "For this purpose, basic research in the area of metallic latent heat storage tanks has to be conducted first in order to then enable long-term testing in the vehicle", Klein Altstedde says.