The plant in Mainz was launched by German engineering company Siemens in partnership with the Mainz energy utility, as well as industrial gas companies Linde and the Rhein-Main University of Applied Sciences.
Using Proton Exchange Membrane (PEM) technology, water molecules are split into hydrogen and oxygen using the surplus energy provided by a voltage source, and the PEM membrane separates the two precious-metal electrodes where oxygen and hydrogen are formed. The plant captures the hydrogen gas, which is then used as general fuel or stored in natural gas pipelines.
It is the largest PEM plant in the world, and can process up to 6MW of electricity. Siemens says that the technology can be implemented to solve bottlenecks in the grid and in small windfarms, and can respond to fluctuations in energy generation within milliseconds. The development of the plant is a part of the country’s Energy Storage Funding Initiative, in response to the pending closures of its nuclear reactors.