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.