Converting wind energy to natural gas

MAN and Audi have geared up to create renewable fuel on an industrial scale for the first time. The vehicle manufacturer will produce and feed synthetic methane (Audi e-gas) into the public natural gas network starting summer 2013.

The core component of the plant, which is being built in cooperation with equipment manufacturer SolarFuel GmbH in Werlte (Emsland region), is a MAN Diesel & Turbo methanation reactor.

The 16-m high e-gas plant unit was constructed and produced by MAN's specialists for chemical and physical reactors at its Deggendorf site. In December 2012, a heavy-duty transport took the ready-for-use tower to Werlte which is 782 kilometers away.

What makes this facility special is its ability to produce carbon neutral fuel from renewable electricity. Audi e-gas can be stored and transported with the infrastructure currently available, as it is almost identical to fossil-based natural gas, chemically speaking. As such, it can easily be distributed via the natural gas network and delivered to CNG stations.

At Audi's plant, electricity from wind or solar energy is converted into e-gas in two major steps. In the first, the electricity is used for the electrolysis of water which splits the compound (H2O) into oxygen (O2) and hydrogen (H2). The hydrogen then reacts with carbon dioxide (CO2), a waste product from a nearby biogas plant, to become methane (CH4).

The dual electricity/gas principle of Audi's e-gas project is a practical example of how to make good use of the wind energy excess on stormy days when the existing German grid is insufficient to carry the load. The Werlte facility will generate enough CO2-neutral e-gas to power 1,500 CNG cars over 15,000 kilometers every year.