But for now, a square meter of the building material holds roughly the energy of two AA batteries.

Concrete, after water, is the world's most used material. Because it already surrounds us in the built environment, researchers have been exploring the idea of using concrete to store electricity—essentially making buildings that act as giant batteries. The idea is gaining ground as many places come to increasingly rely on renewable energy from the wind and sun. Rechargeable batteries are necessary when winds die down or darkness falls, but they are often made of toxic substances that are far from environmentally friendly.

Experimental concrete batteries have managed to hold only a small fraction of what a traditional battery does. But one team describes in the journal Buildings a rechargeable prototype material that could offer a more than 10-fold increase in stored charge, compared with earlier attempts...

Scientific American: Concrete Buildings Could Be Turned into Rechargeable Batteries