Power2Gas (P2G) refers to a process of creating, storing and transporting gas using excess renewable energy (accounting for the variable nature of wind and solar energy - times when the wind blows or the sun shines, but the energy is not used right away). Power2Gas uses excess renewable energy to convert water with electrolysis, first in the process, to hydrogen, which can then undergo methanation, to create synthetic methane. Both types of gas can be combined with natural gas (or used separately, as stand-alone energy sources), and injected into the natural gas network. Existing natural gas infrastructure (pipelines, generators etc…) can be used to create, store and transport the synthetic natural gas (SNG) and/ or hydrogen.
All that is required for electrolysis is water and energy. Electrolysis in P2G uses excess renewable energy to power the conversion of water into hydrogen (and also into oxygen, separating the H2 from H2O). A methanation process can then begin, using the renewable energy source again, to power the mixing of the hydrogen with CO (carbon monoxide), or with C02 (carbon dioxide) to generate synthetic methane. Also, the hydrogen from the electrolysis process can be mixed with biogas from a biogas plant, upgrading the quality of the biogas. Potentially, this method of energy storage can result in far more energy production than simply storing electricity. The gases created in the P2G and also the P2G + biogas plant processes -- SNG, hydrogen and/ or upgraded biogas, can be used in existing natural gas networks for the storage and distribution of the gas.
There are currently around 30 small (under 10 MW) P2G projects (both operating and demonstration) in Europe, mostly in Germany, with some in other European countries. SoCalGas recently launched the first P2G project in the U.S., using excess electricity from renewable energy sources to create hydrogen and methane. SoCalGas uses its natural gas pipelines to store the excess power, and then transports the gas when and where it’s needed.
Much larger than their German counterparts, a 12+ MW P2G project in the Energy Valley region of the Netherlands is set to open in 2016. The project is the largest of its kind, and will not only use the standard P2G processes, but will also create syngas in the unique Torrgas biocoal-gasification process. The unique process of torrefication converts organic wood materials into biocoal, using the oxygen created in P2G. The biocoal is then fed into a gasifier to create syngas, which can then be upgraded using the hydrogen from the electrolysis part of the P2G process. The upgraded syngas will be used to supply power to homes, and other purposes. Other gases, and bio-SNG (synthetic natural gas created from biogas), created in the P2G and gasification processes in this project will also be used in transportation, the chemical industry and other industries.