Photovoltaic (PV) is the fastest growing electricity generation technology in the world . The second fastest growing electricity option is wind power . Global solar and wind resource assessment clearly documents sustainable and by far the highest resource potentials for PV and wind of all power technologies available to the market. However the fluctuating solar and wind resources make it necessary to use fossil fuel power plants or storage capacities for balancing reasons. An emerging storage option is the renewable power methane (RPM) storage technology.