Engineers and scientists from the University of Texas at Austin, led by Rod Ruoff, a mechanical engineering professor and physical chemist, have created a one-atom thick layer of carbon, called “graphene”, and they put it to use in electrical storage systems, such as ultracapacitors, a viable way to clean and efficient energy storage.
The researchers believe their breakthrough shows promise that graphene could eventually double the capacity of existing ultracapacitors, which are manufactured using an entirely different form of carbon.
“Through such a device, electrical charge can be rapidly stored on the graphene sheets, and released from them as well for the delivery of electrical current and, thus, electrical power,” says Rod Ruoff. “There are reasons to think that the ability to store electrical charge can be about double that of current commercially used materials. We are working to see if that prediction will be borne out in the laboratory.”
Currently, two methods exist to store electrical energy: in rechargeable batteries and ultracapacitors, the latter becoming more and more commercialized but are not yet as known as the rechargeable batteries. An ultracapacitor can be used in a wide range of energy capture and storage applications and are used either by themselves as the primary power source or in combination with batteries or fuel cells. Some advantages of ultracapacitors over more traditional energy storage devices (such as batteries) include: higher power capability, longer life, a wider thermal operating range, lighter, more flexible packaging and lower maintenance, Ruoff says.
Ruoff and his team prepared chemically modified graphene material and, using several types of common electrolytes, have constructed and electrically tested graphene-based ultracapacitor cells. The amount of electrical charge stored per weight (called “specific capacitance”) of the graphene material has already rivaled the values available in existing ultracapacitors, and modeling suggests the possibility of doubling the capacity.
“Our interest derives from the exceptional properties of these atom-thick and electrically conductive graphene sheets, because in principle all of the surface of this new carbon material can be in contact with the electrolyte,” says Ruoff, who holds the Cockrell Family Regents Chair in Engineering #7. “Graphene’s surface area of 2630 m2/gram (almost the area of a football field in about 1/500th of a pound of material) means that a greater number of positive or negative ions in the electrolyte can form a layer on the graphene sheets resulting in exceptional levels of stored charge.”
The new discovery could be used in storing the power for hybrid/electric cars, trams, buses, trucks, or whatever device needs to be fed with electricity. Even your cell phone could benefit from these graphite-based ultracapacitors. You wouldn’t have to charge it as often as you do today, and when you would, you’ll do it in a matter of minutes, or even less, because of their fast-charging abilities.
Also, the storage of wind and solar power is in the view of the Department of Energy (DOE), that has said that storing the energy is one of their greatest issues today.
“While it is unlikely that such explosive installation and use of wind can continue at this growth rate for 20 years, one can see the possibilities, and also ponder the issues of scale,” says Ruof. “Electrical energy storage becomes a critical component when very large quantities of renewable electrical energy are being generated.”