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Plant turns electricity into hydrogen


Pilot facility in Frankfurt converts electricity from renewable sources into hydrogen, which can then be injected into the gas grid

A first-of-a-kind power-to-gas energy storage plant that features at its heart electrolyser technology designed and built by a British company has started operating in Germany.

The pilot facility in Frankfurt, owned by the Thüga Group, converts electricity from renewable sources into hydrogen, which can then be injected into the gas grid. This means excess energy generated by wind can be stored for release at a specific time.

The power-to-gas conversion process relies on a proton exchange membrane (PEM) electrolyser designed and built by Sheffield-based ITM Power.

Thüga board member Michael Riechel said: “This is the first plant to convert electricity into hydrogen and subsequently inject it into the German gas distribution network.”

The system worked as planned, said Riechel, with trial operation due to begin in the next couple of months. By the end of 2016, the partners will have gained experience of how the system works under real-world conditions, he added.

The core of the system is an ITM Power PEM electrolyser which converts electrical energy into chemical energy. A mixing plant ensures that the proportion of hydrogen in the natural gas stream does not exceed 2% by volume, the technically permissible maximum when a gas filling station is situated in the local distribution network. 

The electrolyser supplies the hydrogen-methane mixture at the same pressure as the gas distribution network, namely 3.5bar. “We were thus able to avoid using a compressor and save costs,” said Riechel.

The project partners decided to deploy a PEM electrolyser as this technology, in comparison with alkaline systems, uses water rather than a potassium hydroxide solution, and is therefore more environmentally friendly. 

In addition, the system can respond more quickly to changes in the electrical load. 

The power consumption of the electrolyser is 315kW. It produces 60m3 per hour of hydrogen, so in one hour can feed 3,000m3 of hydrogen-enriched natural gas into the network.

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