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. …Despite some new discoveries of lithium reserves, the finite supply of this material… has driven the search for alternative battery materials. This is where Stefaniuk and his concrete come in. He and his colleagues at Massachusetts Institute of Technology (MIT) have found a way of creating an energy storage device known as a supercapacitor from three basic, cheap materials – water, cement and a soot-like substance called carbon black.