By Sara Ver-Bruggen –
Where does electricity come from when renewable energies cannot deliver during calm spells and in the hours of darkness? Storage media are essential for the overhaul of energy policy. The conversion of green power into storable methane is one of the most promising options.
Researchers all over the world have a goal: They want to develop storage media that allows for complete global supply using renewable energies. Power plants that generate storable methane gas using solar and wind power and convert this back into electricity when required could bring us closer to achieving this goal.
Scientists from the Reiner Lemoine Institute (Reiner Lemoine Institut, RLI), the University of Kassel, the Fraunhofer Institute for Wind Energy and Energy Systems Technology (Fraunhofer-Institut für Windenergie und Energiesystemtechnik, IWES) and the companies Q-Cells and Solarfuel are demonstrating that with further technical progress and at locations abundant in sun and wind, these power plants will be able to supply power to fossil fuel plants competitively, i.e., for less than ten euro cents per kilowatt hour, by as early as 2020. The work has been published in a study, entitled “Hybrid solar-wind-methane power plants as the cornerstone of global energy supply” (“Hybride Sonne-Wind-Methan-Kraftwerke als Eckpfeiler der globalen Energieversorgung”).
“With a crude oil price of $150 a barrel, this technology could be the cheapest form of power generation for 90% of the world population in about 10 years,” explains managing director of the RLI Christian Breyer. This is why researchers and engineers are now intensively driving the technology forward.
The idea is simple: Solar power and wind power are dependent upon the weather as well as the time of day and year, meaning that availability fluctuates. In order to avoid fossil fuel power plants jumping in as soon as the demand exceeds the supply of green electricity, the renewable energies must be combined with storage media such as methane.
The IWES, Solarfuel and the Centre for Solar Energy and Hydrogen Research (Zentrum für Sonnenenergie- und Wasserstoff-Forschung, ZSW) have developed a special process for this called “power-to-gas”: Whenever solar parks are producing an excess of electricity, for example, this is diverted to electrolysis units where the power is used to split water into oxygen and hydrogen. In a second step, the hydrogen is combined with carbon dioxide in order to create methane, the main component of natural gas. This can be stored in the natural gas network to the desired extent and is used to supply heating systems, power plants and filling stations. “Enormous storage capacities are available to green energy. Therefore, we tend not to need as many new high voltage lines,” says Breyer.