Power-to-Gas: Energy Storage System of the Future?
"Power-to-gas" is the name given to an energy process and storage technology which allows electricity to be held in reserve in the megawatt range. Existing network infrastructure can be utilized by linking existing power and natural gas grids. This allows seasonally adjusted storage of significant amounts of power and the provision of CO2-neutral fuels in the form of the resulting renewable energy source gas.
Power-to-gas represents a complete system solution to the problem of surplus energy reserves on the way to a new renewable energy age. Hydrogen - and methane in a second additional step - is produced from surplus wind energy by a process of electrolyzation. The hydrogen produced can be stored in the existing natural gas network for later use.
The idea of separating water into its individual components of hydrogen and oxygen is not new, but the coupling of the power grid with the natural gas storage network is. Hydrogen production (70 percent energy conversion efficiency level) is just the first step in a process which will ultimately result in the production of synthetic gas (i.e. methane - 55 to 65 percent energy conversion efficiency level) which can replace natural gas on a like-for-like basis.
Existing energy storage technologies like compressed-air energy Storage (CAES) and pumped storage hydroelectricity certainly have a role to play in the future, but alone they are not able to meet the expected surpluses of solar and wind energy or expected energy shortfalls in periods of low sunshine and wind (future renewable energy-based domestic power supply requires a storage capacity between 20 to 40 terawatt hours - current energy storage capacity is approximately 0.04 terawatt hours).
At present, a compensating capacity level of 17GW is already required to maintain domestic supply and demand balance. This figure is set to rise to 28GW in 2025. To date, balancing power has largely been provided by hydro pumped storage and gas power plants. However, hydro pumped storage is dependent on a number of supporting geographical factors and capacity limitations which restrict universal application. Gas storage, on the other hand, is not encumbered by any of the restrictions associated with extant energy storage technologies.