Storage – They are developing a new cement, coal and water device capable of storing energy at a low cost.

MIT researchers who published their research in the journal PNAS, explain that this technology can be combined with water to make a supercapacitor (an alternative to batteries) and provide electricity storage in various areas. For example, they say it could be built into the concrete foundation of a house, where it could store daylight energy with little (or no) foundation costs and structural strength required. Another possibility would be to use it on a concrete road to recharge the electric vehicles that drive on it without the need for power outlets.

The key to the new supercapacitors developed by this team lies in a method to produce a cement-based material with an extremely large internal surface area thanks to a dense interconnected network of conductive material within its volume.

The researchers did this by incorporating highly conductive black carbon into a concrete mixture, along with powdered cement and water, and letting it set. Reacting with the cement, the water naturally forms an extensive network of holes within the structure, and carbon migrates into these spaces, forming cable structures within the hardened concrete.

These structures are fractal in shape, with branches from which smaller ones grow, and from these even smaller branches, and so on, until they end in an extremely large area within a relatively small volume.

The material is then immersed in a standard electrolyte material such as potassium chloride, a salt that provides charged particles that build up in the carbon structures. The researchers found that two electrodes made of this material, separated by a thin gap or insulating layer, form a very powerful supercapacitor.

The two plates of a capacitor function like two poles of a rechargeable battery with equivalent voltage: when connected to a source of electricity, such as a battery, energy is stored in the plates, and when connected to a load, an electric current flows. again to supply energy.

ancient materials
“The material is amazing,” the researchers say. “We have the world’s most used material, cement combined with soot, which is a well-known historical material: the Dead Sea Scrolls were written with it.” These materials, “combined in a certain way, give rise to conductive nanocomposites, and this is where things get really interesting,” they add.

As the mixture sets, “water is systematically consumed by cement hydration reactions, and this hydration primarily affects the carbon nanoparticles because they are hydrophobic (repel water).” to form a connected conducting wire.”

This whole process is easily reproducible using cheap materials that are easy to find anywhere in the world. In addition, the required amount of carbon is very small (only 3% by volume of the mixture), as indicated. The team calculated that a 45 cubic meter concrete block doped with nanocarbon, equivalent to a cube about 3.5 meters in diameter, would have enough capacity to store about 10 kilowatt-hours of energy, which is considered average daily electricity consumption. household consumption.

Since the concrete will retain its strength, a house with a concrete foundation can store daytime energy generated by solar panels or mini winds and use it when needed. In addition, supercapacitors can charge and discharge much faster than batteries.

So far, MIT engineers have created tiny supercapacitors the size of several button batteries, 1 centimeter in diameter and 1 millimeter thick, each capable of being charged with 1 volt. Once the principle is demonstrated, they plan to build a series of larger versions, ranging from the size of a 12-volt car battery to a 45 cubic meter version, to demonstrate its ability to store energy for the home.