Storing excess electricity as high-temperature heat

Late last November, the energy-transition start-up company Lumenion GmbH (Berlin, Germany; www.lumenion.com) received the 2020 Berlin Brandenburg Innovation Prize for its high-temperature, steel-based energy-storage technology. The system stores peaks of wind and solar energy by heating a steel core to temperaures of up to 650°C. Steel was selected because its thermal conductivity makes it easy and inexpensive to heat. Insulation keeps the steel hot until it is needed, either as process heat for industry, or for district heating (diagram). Because of the high storage temperature, it is also possible to convert some (about 25%) of the thermal energy back into electricity using a turbine. The system has a 95% efficiency (25% electric, 70% thermal) when used for combined power and heat distribution.

The technology was first tested with a 450-kWh prototype on the campus of Berlin’s University of Applied Sciences. In December 2019, a 2.4-MWh storage system was integrated into the district electricity and local heating supply of a residential estate in Berlin-Tegel, operated by Vattenfall Energy Solutions GmbH. This system started up in August 2020 as part of the WindNODE program. Lumenion plans to develop further systems with 40 or even 500 MWh.