Heat, cold air and stone: storage that skips lithium

From liquid air to hot stone, a wave of long-duration storage aims to hold clean power for hours or weeks without lithium.

A crop of long-duration storage projects is trying to hold renewable power without leaning on lithium-ion cells. The largest is in the United Arab Emirates, pairing 5.2 GW of solar with 19 GWh of storage, billed as the world's biggest battery scheme, spread across an area likened to 12,600 football fields and able to power the equivalent of half a million homes overnight.

The methods are unusual. The Carrington plant in Trafford, England, built by Highview Power on a former coal site, chills air to -196C to shrink it to one seven-hundredth of its volume, then expands it through a turbine; once running, it is slated to deliver 300 MWh and 50 MW for six hours. Nevada's Crescent Dunes heats a potassium-sodium nitrate mix to 560C and holds it for up to 10 hours after sunset. Denmark unveiled a 1 GWh molten-salt unit that stores heat at about 600C for up to two weeks. In Pornainen, Finland, a sand battery packs roughly 2,000 tonnes of crushed soapstone for 100 MWh, enough to cover close to a month of the town's summer heat and end the local network's use of oil.

Storage is the real bottleneck for round-the-clock clean power. Many of these designs skip critical minerals like lithium, cobalt, and nickel, can be recycled after a roughly 20-year life, and, unlike cells with finite charge cycles, some can keep running far longer. Cheaper long-duration storage is what turns intermittent sun and wind into firm supply.

One caution: the Carrington cryobattery has faced repeated delays and is not yet operating, and its ability to store energy for days or weeks is so far described in theory.

Source: Guardian