One of the disadvantages of renewable energy sources like wind and solar is the difficulty in managing their fluctuating electrical output to coincide with power demand. Audi's e-gas project has a solution. Excess electrical power would be used to produce hydrogen by electrolysis and e-gas –synthetic methane – by the methanation of hydrogen.
This would provide hydrogen for fuel cell vehicles, e-gas for natural gas vehicles, and electricity for electric models. It would also allow storage of excess electrical capacity, when converted to e-gas, in the largest available energy-storage system: the natural gas network.
Audi is building an e-gas plant consisting of two main elements, an electrolyzer and a methanation unit The electrolyzer running on green electricity uses polymer electrolyte membranes to split water into hydrogen and oxygen. Since there are still few fuel cell vehicles, initially the hydrogen will be used by the methanation unit. Here, hydrogen is combined with carbon dioxide to create e-gas. Methanation uses CO2 rather than discharging it into the atmosphere. Although e-gas is really synthetic natural gas or methane, Audi calls it e-gas.
After three years of research, Audi is now entering the practical phase. In January 2011, a lab facility with an output of 25 kilowatts was set up for testing purposes. In mid-2011, Audi and several partners will invest several tens of millions of euros to begin construction of an e-gas facility in Werlte, Germany. The Audi e-gas project can easily be replicated in any country with an existing natural-gas network.
Starting in 2013, Audi will begin series production of the Audi A3 TCNG with an engine using Audi's TFSI technology that can operate on e-gas, CNG, or conventional gasoline when neither alternative fuel is available.
Audi is also contributing to the construction of offshore North Sea wind turbines. During the project’s first phase, four large powerplants at an offshore wind park in the North Sea are being financed by Audi and a regional power supply company. Rated at 3.6 megawatts each, these four turbines can supply some 53 gigawatt-hours of electricity annually.