Intermittency of wind and solar energy are considered as major obstacles to the use of renewable energy: how to avoid power cuts during night or winter when there is neither wind nor sunshine?
One answer are transnational grids, assuming that there will always be sunshine or wind in a broader geographical area. That is certainly correct, but fails to offer the 100 per cent security of supply that clients expect from their utilities.
Another answer are gas power plants that can rapidly respond to power shortages . But investors do not like to build gas power stations that will lie idle most of the time.
The most conventional response to the storage needs has been pump storage. That is definitely an economic answer; but the number of necessary power stations will by far exceed the physical potential when Europe will one day depend essentially on renewable sources.
Power-to-gas installations may be offer the potential for the large scale and long-term storage needs of the future: they use surplus wind- or solar- generated electricity to splitting water into hydrogen and oxygen through hydrolysis.
By combining these with carbon dioxide the installation produces methane that can be stored in depleted gas or salt caves and burnt in gas-fired power plants whenever needed in times of lull or darkness. A small 250 kW installation is presently being tested for its technical feasibility in Stuttgart. Others are due to follow next year.
Power conversion losses and storage costs will ultimately decide on the future of this storage technology.
For Germany with its objective of replacing nuclear electricity by energy efficiency and renewable sources until 2022 the rapid development of cost-efficient electricity storage will be crucial for the success of its “energy revolution”. It has therefore little choice but to be the front-runner, hoping to develop by the same token a new export technology.
Eberhard Rhein, Brussels