Energy-storing concrete

A supercapacitor made from cement and carbon black (a conductive material resembling fine charcoal) could form the basis for a low-cost way to store energy from renewable sources, according to MIT researchers.

The amount of power a capacitor can store depends on the total surface area of its conductive plates. Professors Franz-Josef Ulm, Admir Masic, and Yang Shao-Horn and colleagues found that if carbon black is introduced into a mixture with cement powder and water, the water naturally forms a branching network of openings when the resulting concrete cures-and the carbon migrates into that network to make wire-like structures, yielding a conductive material with an extremely large internal surface area.

Two electrodes made by soaking this material in a standard electrolyte, separated by a thin space or an insulating layer, form a very powerful supercapacitor, the researchers found. A cube about 3.5 meters across could store about 10 kilowatt-hours.

The simple technology could eventually be incorporated into the concrete foundation of a house, where it could store a day's worth of energy. The researchers also envision a roadway that could provide contactless recharging for electric cars as they travel.

It's a new way of looking toward the future of concrete as part of the energy transition," Ulm says.