In partnership with Technical University Hamburg Harburg and urban utility Hamburg Energie, Siemens is researching an energy storage solution in the northern German city of Hamburg that it says will set a future standard in efficiency.
It is intended as an economic solution for excess wind energy storage and takes the form of an insulated thermal store made of rock fill, combined with steam generation and turbine equipment.
The simple principle of this store promises an extremely low-cost set-up, and the project has received research funding from the German Federal Ministry for Economic Affairs and Energy.
Siemens is currently operating a test set-up, designated Future Energy Solution (FES), at Hamburg-Bergedorf. Alongside scientists from the TUHH Institute for Thermofluid Dynamics, the company is researching how to make charging and discharging the store particularly efficient. The arrangement of the rock fill and the form of the surrounding insulating container are crucial. The store is being tested at temperatures over 600°C. Heat is supplied to the rockfill via an electrically heated air gun to heat the stones to the desired temperature. When discharging, the hot stones heat the air current, which energises a steam boiler driving a steam turbine.
As the current test set-up only tests the thermal requirements for the storage
process, no reverse current is generated at present. However, in the spring of 2017 researchers will test the complete energy conversion process in both directions.
The thermal store is being established at the Trimet aluminum smelter site in Hamburg-Altenwerder. At its full size it will be able to store around 36 MWh of energy in about 2000 cubic metres of rock. The heat it contains will be able to drive a Siemens compact steam turbine at up to 1.5 MWe for up to 24 hours a day.
The research team expects to generate at an efficiency of around 25% even in this early development phase, rising potentially to 50% in the future.
“The technology of our FES store … uses mainly tried and trusted
technology,” says Till Barmeier, Siemens’ project manager. “Because we are
working here with tested thermal components and a series-ready steam turbine, we will be able to offer a practical solution within a few years. Our complete experimental system will be operational in around 15 months.”
The FES technology can be used for a wide variety of sizes and output classes, and always remains extremely economical, says Siemens. The only limit to the concept is the space required for the rock-filled insulated container.