Electrical energy can be captured as liquid air

The result might give grid-scale batteries a run for their money

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 article). 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.

At a temperature of -196°C, all of air’s component gases will liquefy. Doing this is a routine, electrically driven industrial procedure. Storing liquefied gases in bulk is also a routine piece of engineering. The result occupies a 700th of the volume of those gases at room temperature—so, when liquid air is warmed and allowed to expand, it does so forcefully. Using a device called a Dearman engine (after its inventor, a Briton named Peter Dearman), that forceful expansion can be employed to spin turbines, and thus generators, thereby recovering part of the electricity used to liquefy the air in the first place. MORE