In the German city of Mainz 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.
From next year, the energy storage system, equipped with an electrolyzer from Siemens, will convert excess electricity from wind farms into hydrogen. The hydrogen will then be stored locally in tankers or fed directly into the natural gas grid for subsequent power or heat generation.
This will make it possible to store electricity from renewable sources over longer periods of time. The tankers will also supply the growing network of hydrogen-filling stations for emission-free fuel-cell vehicles.
Storage system has unique features
The system will have a peak rating of up to 6MW, making it the largest of its kind in the world. The 17 million project is being financed with the support of the German Federal Ministry of Economics and Technology as part of the Energy Storage Funding Initiative.
The principle of electrolysis has been tried and tested for decades. However, the Mainz system is unique in that it involves highly dynamic Proton Exchange Membrane (PEM) high-pressure electrolysis which is suitable for high current density and can react within milliseconds to sharp increases in power generation from wind and solar sources.
In the electrolyzer, the proton exchange membrane 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 now have a capacity relevant for bottlenecks in the grid and small wind farms.
A valuable resource for customers
Hydrogen obtained from electrolysis offers many advantages and can be used in many ways.
Using excess green electricity, hydrogen can be produced by electrolysis and stored as an energy medium, for example, in underground caverns. When demand increases, the energy-rich gas can also drive turbines and produce electricity, which is then fed into the grid ("reconversion"). The Proton Exchange Membrane electrolyzer acts as a dynamic control load component to compensate for fluctuations in power grids. The electrolyzer will become a strategic key component for power utilities, grid operators and suppliers of renewable energy.
The material exploitation of hydrogen in industrial processes is also possible, for example, for the production of fertilizers, as a component in the chemical industry, for hardening fats in the food industry and in the production of copper.
Over 500 billion cubic meters of hydrogen is used globally every year-95% of this is produced by a carbon dioxide-producing gas reforming process. With hydrogen from electrolysis, this process can be substituted, which can greatly improve the emissions balance of industrial processes.
Hydrogen can also be used as fuel for variations of fuel cell powered vehicles.
If electrolysis uses electricity from renewable sources, hydrogen production is also virtually carbon neutral.
Gaelle Hotellier, head of the Hydrogen Solutions business segment, points out, We have succeeded in producing 'green hydrogen', which can help both to avoid carbon dioxide emissions to a relevant degree as well as to make available emission-free fuel for mobility.
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