IEEE Spectrum has an article on a variant of compressd air energy storage being trialled in the UK - Liquefied Air to Store Energy on U.K. Grid.
U.K.-based Highview Power Storage last week said that it has been awarded an £8 million grant from the U.K. Department of Energy and Climate Change to build a commercial-scale facility that uses liquified air to store energy. Highview is already running a smaller pilot plant, but the full-scale version will be able to store enough energy to deliver five megawatts of power for three hours. That puts it on a scale that would entice utilities to use the technology, says company CEO Gareth Brett. ...
Liquid air energy storage is similar to compressed air energy storage in that air is compressed and released to store and then generate power. With Highview’s technology, though, ambient air is compressed, then cooled and liquified. That liquefied air, which is almost -200 °C, is stored in large tanks.
When power is needed, the liquid air is released and pumped to high pressure. That causes the liquid to evaporate, turning it into a high-pressure gas which is then run through a turbine to generate power. The planned demonstration plant will be located at a waste processing center. Heat from the waste plant’s gas turbines, which run on captured landfill methane, will be piped in to improve the efficiency of the evaporation process.
One of the advantages of liquid air storage is that it uses off-the-shelf equipment. The tanks for storing liquid air, for instance, are the same as those used in the industrial gas industry.