MIT scientists construct low-cost energy storage system out of concrete

Energy-storing concrete could, in the future, be used to hold electricity in houses and other buildings.

In a study, published by scientists from the Massachusetts Institute of Technology earlier this summer, it was demonstrated that a seemingly basic mix of concrete and fine charcoal can create a low-cost and efficient energy storage system.

This innovation could allow homes to store a full day's worth of renewable energy from solar panels or wind turbines in a domestic setting, which would accommodate for the fluctuation of power commonly associated with renewable energy. Concrete roads may even one day be able to store energy that could contactlessly charge electric vehicles on the move.

This intriguing mix of ancient materials demonstrated in testing that it could charge and discharge in over 10,000 cycles. To give context to this, small handheld lithium ion batteries can recharge in cycles up to 1,000 times, with the large-scale batteries powering high-end electric vehicles, such as Tesla, touching near 1,500.

Scientists have been experimenting with the conductive qualities of novel cement mixtures for several years now. The difference in this new method is the cement has an extremely high internal surface area, which contains a complex and interconnected network of conductive carbon within it. This form of super capacitor has never been achieved before and as the cement hardens, carbon spreads throughout it to form a network of conductive paths, like wires.

As promising as this new technology sounds, replacing our energy infrastructure with it is not so simple. Replacing concrete or brick with the flat layered "concrete plywood "referenced in the study would require an overall change in how we approach modern architecture and lay down roadworks.

The conductive salt solution required to carry electrical charge through the design would also mean parts of the structure would have to constantly remain wet, and would carry its own additional maintenance challenges.

Nevertheless, our existing answers for energy storage are far from perfect and an urgent overhaul is needed. Electricity from renewable sources such as solar, wind, or hydro all produce power at inconsistent rates. Wind can fluctuate, clouds can form unpredictably, and water flow is often chaotic minute-to-minute.

These variable times of output do not correspond to human schedules of electricity usage, meaning that the question of how power is stored for a consistent output is a huge issue. Current lithium ion batteries used for this purpose are expensive, hazardous, and rely on limited supplies of the precious element itself.

Meanwhile, calculations from MIT researchers suggest that a simple cube of charcoal concrete sized just 3.5 meters across could hold 10 kilowatt-hours of energy, enough to supply the average household's electricity needs for the day. The prospect of using such cheap and readily available ancient materials to fulfill this role is extremely promising, though it may be a while before you see it on a building site near you.

Barry He is a London-based columnist for China Daily