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News | 6.7.2015
World’s largest electrolysis plant

Energiepark Mainz inaugurated

The horizontal pressurised hydrogen tanks are used for temporarily storing the hydrogen produced. The storage capacity is approximately 1,000 kg, which corresponds to around 33 MWh of energy.
© Anna Durst, forschung-energiespeicher.info
In the electrolysis hall, a hydrogen-electrolysis system from Siemens produces hydrogen from surplus electricity.
© Siemens AG
The ionic compressor forms the centrepiece of the hydrogen conditioning.
© Anna Durst, forschung-energiespeicher.info
At the on-site filling station, trailers are filled with hydrogen that can then be stored or transported.
© Anna Durst, forschung-energiespeicher.info

At Energiepark Mainz, Linde, Siemens, RheinMain University and the

Stadtwerke Mainz municipal utility company are producing large amounts

of hydrogen by renewable means. Four adjacent wind turbines take over

the largest part of the electricity generation. The hydrogen can be

stored on site, transported in tanks or fed into the natural gas network

for the subsequent generation of electricity or heat. The world's

largest electrolysis plant of its kind has now been inaugurated.

About the size of a supermarket, the electrolysis hall at Energiepark Mainz is situated next to the exhibition grounds in Mainz-Hechtsheim. In a research project, Linde, Siemens, RheinMain University and Mainz’s municipal utility company, Stadtwerke Mainz, want to produce large quantities of hydrogen using renewable electricity. The majority of the electricity is supplied by four adjacent wind turbines. The plant is connected directly to the wind farm’s grid connection cable. “When both the wind turbines and the electrolysis system are in operation, the wind power can also be used,” says Jonas Aichinger, coordinator of the research project.

A special feature is the hydrogen-electrolysis system developed by Siemens: the researchers have installed a highly dynamic, PEM pressure electrolysis unit that is especially suited for high current densities and can respond to large hikes in the electricity produced from wind and solar power plants within milliseconds. That helps to balance out congestion in the electricity grid. The centrepiece is the ionic compressor (pictured centre left) for the hydrogen conditioning. Liquid salt lubricates, cools and seals the hydraulically driven piston compressors without contaminating the hydrogen. The unit was developed for multivariable operation with rapid load changes and high partial load efficiency, and feeds – with two stages – both the storage tank and the trailers. Another special feature is the integrated drying of the hydrogen.

Using the hydrogen produced

In contrast to other smaller pilot projects, the system can accommodate up to six megawatts of electricity and generates 1,000 cubic metres of hydrogen per hour. This makes it the largest plant of its kind to date.

The hydrogen can be stored on site, used for filling trailers (pictured bottom left) or fed directly into the natural gas network where it can be used at a later point for generating electricity or heat. “In principle, the hydrogen produced from electricity can be stored as long as desired in containers,” explains the project coordinator. Using tankers, the energy park can also supply the growing network of hydrogen filling stations used for tanking fuel cell vehicles.

Further tests and next project stage

In a next step, the researchers want to conduct further tests. “Using different operating conditions over a longer period we want to test, for example, how the highly dynamic operation needs to be organised with external requirements from the electricity system,” explains Aichinger. The developers also want to try connecting the power-to-gas plant to the power exchange and the balancing power market. Aichinger adds: “Which electricity volumes flow into the system from which sources will depend on the technical and economic optimisation.”

Supported by: The Federal Government on the basis of a decision by the German Bundestag

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