An artist's impression of Highview's planned energy storage facility It sounds like magic but it is real - a plan to store cheap night-time wind energy in the form of liquid air. Here is how: you use the off-peak electricity to compress and cool air in a tank, so it becomes a freezing liquid. When demand peaks, you warm the liquid back into a gas, and as that expands it drives a turbine to create more electricity. The technology, promoted by a backyard inventor, is about to hit the big time. It has been tried at a small scale but now the firm behind it, Highview, has announced that a grid-scale 50MW plant will be built in the north of England on the site of a former conventional power plant. The technology has been supported by the UK government. One attractive feature is that it uses existing simple technology developed for storing and compressing liquefied natural gas (LNG), so unlike battery storage, it does not require mining for rare minerals. The key innovation is to stor...