Concrete as low-cost energy storage
Researchers at MIT developed a way to use concrete as energy storage, by mixing cement with carbon black.
The process uses the way that water and cement react together to its advantage. Water forms a branching network of channels in the concrete as it starts to harden. The mixed in carbon black follows those channels, that exhibit a fractal-like structure. Larger branches split off into smaller and smaller ones, which creates carbon electrodes with an extremely large surface area running throughout the concrete.
Two branches are separated by an insulating layer, and work as the plates of a supercapacitor once the concrete has been bathed in a standard electrolyte like potassium chloride. Supercapacitors can charge up and discharge almost immediately, so power density and output are generally much higher than a standard lithium battery.
The more carbon black is added, the more energy can be stored, but it does come at the cost of weaker concrete, so a tradeoff has to be made. However, since concrete is usually used in bulk, this doesn’t have to be a disadvantage. The MIT team says a 45 m3 block of nanocarbon black-doped concrete will store around 10 kWh of electricity, enough to cover around a third of the power consumption of the average American home.