Electrical energy can be captured as liquid air

IN THE PAST few decades wind and solar power have gone from being exotic technologies to quotidian pieces of engineering that are competitive, joule for joule, with fossil fuels. Those fuels retain what edge they have only because of their reliability. The wind may not blow, or the sun may not shine, but—short of a blockade or strike—a coal or gas power station will always have something to burn.To overcome the reliability problem requires cheap grid-scale energy storage that can be scaled up indefinitely. At the moment, the market leader is the lithium-ion battery (see ). Such batteries—already the workhorse of applications from mobile phones to electric cars—are reliable, scalable and well understood. Most proposed alternatives are clumsy, poorly understood, unscalable or all three. But there is one that, because it relies on putting together pieces of engineering used routinely elsewhere, and thus proven to work, might give lithium-ion batteries a run for their money: liquid air.