In May 2014 Siemens, together with the public utilities of Mainz, Linde and the RheinMain University of Applied Sciences, has laid the foundation stone for a new type of energy storage system. Now, time has come: By pressing a symbolic button, the Chairman of the Board of Linde Group, Dr. Wolfgang Bchele, Siemens board member Professor Siegfried Russwurm, two board members of Stadtwerke Mainz AG, Detlev Hhne and Dr. Tobias Brosze, and Professor Dr. Detlev Reymann, President of RheinMain University, officially launched a hydrogen production plant at the Energiepark Mainz on July 2, 2015. With the support of the German Federal Ministry of Economics and Technology as part of the Energy Storage Funding Initiative the 17-million-project could be realized. The system, equipped with an electrolyzer from Siemens, will convert surplus electricity from wind farms to hydrogen from now on. In this way, it will be possible to store electricity from renewable sources over longer periods of time. With a peak rating of up to 6 megawatts the plant is the largest of its kind in the world.
The principle of electrolysis has been tried and tested for decades. What is special about the Mainz system is that it involves highly dynamic PEM high-pressure electrolysis which is particularly suitable for high current density and can react within milliseconds to sharp increases in power generation from wind and solar sources. In this electrolyzer a proton exchange membrane (PEM) separates the two electrodes at which oxygen and hydrogen are formed. On the front and back of the membrane are precious-metal electrodes that are connected to the positive and negative poles of the voltage source. This is where the water is split. The system in Mainz will thus have a capacity relevant for bottlenecks in the grid and small wind farms.
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