In addition to testing the technical feasibility of power-to-gas, the companies are calling for framework conditions that will enable reliable and economical operation of this technology.

The basic concept of power-to-gas (or e-Gas, as Audi calls it), is to “store” excess renewable electricity by producing hydrogen, which can then either be converted to methane; injected into the gas distribution grid directly; or used as a vehicle fuel. An analysis by Thüga has shown that the storage requirements for renewable electricity could be 17 terawatt hours (TWh) in 2020 and could even reach 50 TWh in 2050. The municipal gas distribution networks can manage these quantities in principle.

The Thüga plant’s conversion of electricity to hydrogen and the feeding into the local gas distribution network should begin by the end of 2013.

The operational data will be shared by the whole Thüga group. The project partners include: badenova AG & Co. KG; Erdgas Mittelsachsen GmbH; Energieversorgung Mittelrhein GmbH; erdgas schwaben GmbH; Gasversorgung Westerwald GmbH; Mainova Aktiengesellschaft; Stadtwerke Ansbach GmbH; Stadtwerke Bad Hersfeld GmbH; Thüga Energienetze GmbH; WEMAG AG; e-rp GmbH; and ESWE Versorgungs AG with Thüga Aktiengesellschaft as project coordinator. Scientific partners will participate in the operational phase.

At the core of the plant is a proton exchange membrane (PEM) electrolyzer produced by ITM Power. The project partners opted for this system because, in comparison with alkaline electrolyzers, the operating medium is water rather than a potassium hydroxide solution and is therefore more environmentally friendly.

Furthermore, the system reacts more quickly to changes in the electrical load on the grid thanks to the PEM electrolyzer. A further advantage is the compact design, as a higher output can be achieved in the same unit area. The plant will produce around 60 cubic meters of hydrogen per hour and so feed 3000 cubic meters of natural gas enriched with hydrogen into the grid per hour. An expansion of the pilot plant is planned from 2016 and the hydrogen will then be converted to methane and fed into the gas distribution network.