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Construction has begun in Germany of a power-to-gas energy storage plant which at its heart will feature electrolyser technology designed and built by a British company.
The pilot facility in Frankfurt will convert electricity from renewable sources into hydrogen, which can then be injected into the gas grid. This approach means excess energy generated by wind can effectively 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. The PEM device was chosen because it is claimed to react more quickly to changes in the electrical load on the grid compared to other rival technologies. It also uses water as an operating medium, as opposed to potassium hydroxide commonly used by alkaline electrolysers, and is therefore deemed more environmentally friendly.
The plant, which is being built by the Thüga Group, will be operational by the end of the year, and will run for a period of three years.
It will produce around 60m3 of hydrogen per hour to feed 3,000m3 of natural gas enriched with hydrogen into the grid per hour. An expansion of the pilot plant is planned from 2016, from which the hydrogen will then be converted to methane and fed into the gas distribution network.
Simon Bourne, ITM's chief technology officer, said that the use of power-to-gas plants to store energy from renewable supplies was an emerging technology that could enable countries to better manage the integration of renewable energy onto their networks.
He said: “If you were to use electricity to make hydrogen, there would be several things you can do with that hydrogen, such as using it as a feedstock for agricultural processes.
“But some of the more recent applications are using that hydrogen as a means for storing energy. One way of doing that is to blend the hydrogen with natural gas and use it in the natural gas mains network. What that means is that any application downstream that uses natural gas will effectively be decarbonised to some extent.”
Bourne said that the rapid response capability of ITM's PEM electrolyser meant that it was ideally suited for dealing with the intermittent nature of renewable energy supply.
“The thing that is unique about our technology is that it can be switched on and off very rapidly,” he said. “That means that if all of a sudden there is excess renewable power, you can turn the equipment on and it can be very quickly assimilated. Without the ability to do that the solution is no way near as effective. Also, from an environmental perspective, our system contains no caustic materials.”
The Frankfurt plant will inject pure hydrogen into the gas network. The percentage rate that hydrogen can be mixed with natural gas depends on the laws of individual countries, but it usually accounts for 2-5%.
Alternatively, the hydrogen could be combined with CO2 from an industrial process to produce a synthetic natural gas that could also be fed into the grid. “Our electrolyser is agnostic to either,” said Bourne.
There are several other similar power-to-gas facilities being built in Germany, which compared with other European countries derives a relatively high percentage of its energy from renewable sources.
Thüga said that energy storage requirements in Germany could be 17TWh in 2020 and up to 50TWh in 2050. Michael Riechel, member of the Thüga management board, said that, in principle, the municipal gas distribution networks could manage such a load.
“Our gas distribution networks could therefore be the battery of the future,” he said.
However, Riechel said that, in order for the power-to-gas storage technology to realise its full potential, there was a requirement for temporary start-up funding in the form of state grants, as well as a legal foundation for the technology.
In the UK, meanwhile, ITM said that there was an appetite for power-to-gas technology and that discussions with energy companies were already under way.
“However, we are not in a position where we can say anything about that yet,” said Bourne.