In partnership with the Technical University Hamburg Harburg (TUHH) and urban utility company Hamburg Energie, Siemens is researching a storage solution in the Northern German city that will set a future standard in efficiency.
How it works: after having been converted to heat in rock fill, excess wind energy is stored and protected with an insulated cover. When there is a need for additional electricity, a steam turbine converts the heat energy back to electricity. The principle of this store promises an extremely low-cost set-up.
The thermal store for wind energy project is a joint study between Siemens, Hamburg Energie, and TUHH. After conversion to heat in rock fill, excess wind energy is stored and protected with an insulated cover. When there is a need for additional electricity, a steam turbine converts the heat energy back to electricity.
Siemens is currently operating a test set-up for the storage solution, named Future Energy Solution (FES), at Hamburg-Bergedorf. The project has received research funding from the German Federal Ministry for Economic Affairs and Energy.
Alongside scientists from the TUHH Institute for Thermofluid Dynamics, Siemens is further 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.
Just like a hot air gun, a fan uses an electrically-heated air flow to heat the stones to the desired temperature. When discharging, the hot stones in turn heat the air current, which then heats a steam boiler — the pressure drives a generator via a steam turbine.
As the current test set-up only tests the thermal requirements for the storage process, no reverse current is generated. However, researchers wish to test the complete energy conversion in spring 2017, from electricity to heat storage in the rock fill and back to electricity. They are establishing a complete thermal store on the Trimet aluminum smelter site in Hamburg-Altenwerder to the south of the River Elbe on the German A7 highway.
The full-size FES will be able to store around 36 MWh of energy in a container with around 2,000 cubic meters of rock. By using a boiler, the heat it contains will generate so much steam that a Siemens compact steam turbine can generate output of up to 1.5 MW of electricity for up to 24 hours a day. The researchers expect to generate effectiveness of around 25%, even in this early development phase.
In the future the concept has the potential for an effectiveness of around 50%. Partner Hamburg Energie will investigate appropriate marketing options for the stored energy.
“The technology of our FES store deliberately 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 just around 15 months.”
Whereas many other stores generate high costs or only permit limited storage capacities, the FES technology can be used in the most varied of sizes and output classes, and therefore always remains extremely economical. The only limit to the concept is the space required for the rock-filled insulated container.
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