A new study by scientists from the Massachusetts Institute of Technology has found that two of humanity's most prevalent materials, cement and carbon black (similar to fine-grained charcoal), could form the basis for a new, low-cost energy storage system.
This technology can facilitate the use of renewable energy sources, such as solar, wind and tidal energy, by allowing power grids to remain stable despite fluctuations in renewable energy supplies.
The researchers found that the two materials could be combined with water to create a supercapacitor — an alternative to batteries — that could provide storage of electrical energy. MIT researchers who developed the system say that the supercapacitor can eventually be integrated into a house's concrete foundations, where it can store enough energy for an entire day while adding little to the cost of the foundations, maintaining the required structural strength.
The researchers also envision the possibility of creating concrete roads that could provide contactless recharging for electric vehicles as they travel through those roads.
The simple and innovative technology was described in a paper published in the journal Proceedings of the National Academy of Sciences (PNAS) on July 31.
Capacitors are very simple devices consisting of two electrically conductive plates immersed in an electrolyte (Wikipedia)
How do we understand this innovation?
To understand this innovation, let's understand the idea of capacitors and their work in electrical energy. Capacitors, in principle, are very simple devices consisting of two electrically conductive plates immersed in an electrolyte and separated by a membrane. When a voltage is applied through the capacitor, positively charged ions of the electrolyte accumulate on the negatively charged plate, while negatively charged ions accumulate on the positively charged plate.
Because the membrane between the plates prevents charged ions from traveling through them, this charge separation creates an electric field between the plates, and the capacitor becomes charged. The plates can hold this pair of charges for a long time, and then connect them very quickly when needed.
Super capacitors can store exceptionally large charges. The amount of energy a capacitor can store depends on the total area of its conductive panels. The key to the new supercapacitors developed by the U.S. team comes from the method of producing a cement-based material with an extremely high internal surface area due to a dense and interconnected network of conductive materials within its larger size.
Carbon black – high conductivity – introduced into a concrete mixture along with cement powder and water (Getty Images)
Carbon black and water mixture
The researchers inserted high-conductivity carbon black into a concrete mixture along with cement powder and water, and let it dry, and the water naturally forms a branching network of openings within the structure where it interacts with the cement, and the carbon moves into these spaces to make wire-like structures inside the hardened cement.
These structures have a fracture-like structure, with larger branches sprouting smaller branches, from which smaller branches grow, and so on, ending with a very large area within the boundaries of a relatively small size.
The material is then soaked in a standard electrolyte material, such as potassium chloride, a type of salt, that provides charged particles that accumulate on carbon structures. The researchers found that two electrodes made of this material, separated by a thin area or insulating layer, form a very strong supercapacitor.
The two capacitor panels work just like two poles of a rechargeable battery with an equivalent voltage when connected to an electricity source, where energy is stored in the panels, and then when connected to a load, the electric current flows again to save power.
New supercapacitors have great potential to help the world's transition to renewable energy (Shutterstock)
Great opportunity for the transition to renewable energies
Researchers say supercapacitors made from this material have great potential to help the world's transition to renewable energy, as major renewable sources – such as wind, solar and tidal energy – produce energy at variable times that often do not correspond to peak electricity use, so methods of storing this energy are essential.
With a huge need for massive energy storage, and the high cost of current batteries that rely mostly on limited materials such as lithium, there is an urgent need for cheaper alternatives, and here comes the importance of the new discovery, because cement is everywhere.
According to the US team, a block of carbon black coated nanoconcrete with a volume of 45 cubic meters - equivalent to a cube about 3.5 meters wide - will have enough capacity to store about 10 kilowatt-hours of energy, which is the average daily use of electricity per household. A home with a foundation made of this material can store daily energy produced by solar panels or windmills and allow it to be used when needed. Super capacitors can be charged and discharged much more quickly than batteries.
After a series of tests used to determine the most effective proportions of cement, carbon black and water, the team made small supercapacitors, about 1 centimeter wide and 12 millimeter thick, each of which can be charged to 45 volt, and the team is currently planning to build a series of larger versions of the batteries, starting with a battery the size of a typical <>-volt car battery, and then working until the <>-cubic-meter version to prove its ability to store the electrical energy needed for the home.