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All components for storing energy with hydrogen are being tested at Mainz Energy Park. The plant will be completed by 2015 and will be around the size of a supermarket.
© Energiepark Mainz, Montage BINE Informationsdienst
Mainz Energy Park

In electrolysis, water in its liquid form is broken down into its individual components on the anode side of the electrolysis cell. The oxygen molecules are discharged to the anode side whereas the protons are transported via a conducting membrane to the cathode side where, by each absorbing two electrons, they combine to form hydrogen molecules.
© Energiepark Mainz

Storing wind energy in the form of hydrogen

An energy park is set to be created in Mainz for completion by 2015. The idea is to temporarily store electricity from wind energy as hydrogen. This can be used as fuel, for generating heat or for reconverting the stored energy back into electricity. An electrolysis plant shall store up to six megawatts of electricity and balance out fluctuations in the distribution grid. This would make it the largest plant of its kind to date.

It is intended that renewables shall supply around 80 per cent of the electricity requirement by 2050. The German federal government’s Energy Storage Funding Initiative is therefore supporting technological developments that lower costs and contribute to rapid market introductions.

Together with Linde, Siemens and RheinMain University of Applied Sciences, the Mainz municipal utility company is using wind energy to generate hydrogen in the new Mainz Energy Park. The electrolysis plant absorbs surplus wind energy and produces hydrogen.

“The hydrogen can be easily stored and can be used in diverse ways, such as for hydrogen filling stations or as fuel for power plants,” says Jonas Aichinger, project coordinator for the energy park scheme. The Mainz Energy Park is being created in the business park in Mainz-Hechtsheim. The plant is scheduled to begin construction at the beginning of next year and is set to go into operation in spring 2015. “The plant can store up to six megawatts of electricity and has therefore an output class that is relevant for bottlenecks in the distribution grid,” explains Aichinger further. This would make it the largest plant of its kind to date.

Use as fuel, for generating heat and for reconversion back into electricity

The hydrogen shall be fed into the natural gas network, where it can be used for heating or in gas-fired power plants and CHP units for providing combined heat and electricity generation. The companies also want to investigate whether the hydrogen produced can be used in combined cycle gas turbine plants as a fuel for regenerating electricity.

The core of the research plant is a hydrogen electrolysis system developed by Siemens. This breaks down water into its components hydrogen and oxygen. The hydrogen is compressed with a hydrogen compressor from Linde and is then stored or filled in trailers.

All the main components for storing energy using hydrogen are being tested out in the Energy Park, such as electrolysis, gas injection, hydrogen compressors, pressure accumulators and trailer filling. Further details about Mainz Energy Park are available on its website.

About the Energy Storage funding initiative

The Energy Park is being supported by the German Federal Ministry of Economics and Technology as part of its Energy Storage funding initiative. It forms one of the flagship projects in the initiative’s “Combined Wind-Hydrogen” programme. This programme bundles projects that are conducting research into the generation of hydrogen or methane from surplus wind energy. The main focus is on optimising the electrolysis to achieve greater efficiency when splitting water to form storable hydrogen and oxygen.



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Project management
Stadtwerke Mainz AG

Project partner
Siemens AG

Project partner
Linde AG

Project partner
Hochschule RheinMain