// CoolEV – Recovering waste heat during fast charging

People who buy an electric car do not want to waste a lot of time charging up on long distance trips. Today, it takes around 20 to 30 minutes to replenish the charge of a midsized electric car with a 400-kilometer (km) range for it to travel another 280 km. That is just too long to wait for most customers, which is why fast-charging capability is so crucial to enabling long-distance trips and winning customers over to electric vehicles. The CoolEV project, an initiative to develop an innovative cooling system for ultrafast charging, is helping to advance both causes. This will be a holistic system engineered to achieve both, cooling of vehicle-bound and stationary charging components and at the same time recover waste heat generated by the charging process. The goals are to enable fast charging with up to 400 kW DC and thus reduce today’s 20-to-30 minute wait significantly and to improve electric vehicles’ overall energy footprint.

Although new battery concepts enable this kind of fast charging, they do so at the expense of charging losses ranging up to 40 kW. A cooling system would have to dissipate this waste heat from the vehicle. As it stands today, this system would be much too large, heavy and expensive for the mass market. It will take more research to further reduce charging times or at least maintain current charging times for larger batteries.

The idea behind and objectives for this project

This initiative goes to investigate future fast charging options and sound out the limits with respect to heat dissipation, efficiency and economy. The researchers aim to develop an innovative cooling system that takes into account the different requirements of individual vehicle components and of charging infrastructure. A special thermal interface is to transfer part of the required cooling power from the vehicle to the charging station.

Another goal is to make productive use of the waste heat generated during fast charging. The idea is to improve electric vehicles’ overall energy footprint and thereby decisively contribute to future electric vehicles’ competitiveness, cost-effectiveness and market penetration.

Practical applications

For one, a demonstrator vehicle with optimized cooling for battery and the electric drive components will be developed in the course of this project. For the other, prototype charging infrastructure will serve to simulate how heat lost during fast charging can best be utilized.

The researchers’ findings will underpin further efforts to develop range-extending concepts and ramp up batteries for mass production. These concepts are highly relevant for premium vehicles, but are also needed to drive the electrification of commercial vehicles.

How ZSW is contributing to this research effort

Moving the cooling system from the vehicle to the fixed charging station allows for waste heat to be reused and thus increasing the overall energy efficiency of the fast-charging processes. Highly frequented e-charging parks at freeway service stations and the like are going to generate a lot of heat that can be utilized. Possible scenarios are to provide heating and hot water to buildings or car wash facilities at service stations. Being partner in this project, ZSW is developing suitable concepts and potential business models for such utilization of waste heat.

About the CoolEV joint project

ZSW is pursuing the CoolEV project alongside the Institute of Automotive Engineering Stuttgart (IFS), Esslingen University of Applied Sciences, and HYDAC INTERNATIONAL GmbH in a consortium headed up by Dr. Ing. h.c. F. Porsche AG. The German Federal Ministry for Economic Affairs and Climate Action (BMWK) is funding the project as part of the Elektro-Mobil grant program.

Funding period: Jan. 1, 2020 to Dec. 31, 2022


Dennis Huschenhöfer
A diagram of proposed waste heat utilization during fast charging (Source: HSE-MT/Deininger)
A diagram of proposed waste heat utilization during fast charging (Source: HSE-MT/Deininger)

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