The cement that could turn your house into a giant battery

Concrete is perhaps the most commonly used building material in the world. With a bit of tweaking, it could help to power our homes too.

On a laboratory bench in Cambridge, Massachusetts, a stack of polished cylinders of black-coloured concrete sit bathed in liquid and entwined in cables. To a casual observer, they aren't doing much. But then Damian Stefaniuk flicks a switch. The blocks of human-made rock are wired up to an LED – and the bulb flickers into life.

"At first I didn't believe it," says Stefaniuk, describing the first time the LED lit up. "I thought that I hadn't disconnected the external power source, and that was why the LED was on.

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