Washington, September 17 : A team of engineers and scientists at the University of Texas at Austin, US, have shown the usage of graphene as a new carbon-based material for storing large quantities of renewable electrical energy.
They have shown that the material can be used for storing electrical charge in ultracapacitor devices, perhaps paving the way for the massive installation of renewable energies such as wind and solar power.
The researchers believe their breakthrough shows promise that graphene (a form of carbon) 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," said Rod Ruoff, a mechanical engineering professor and a physical chemist.
"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," he added.
Two main methods exist to store electrical energy: in rechargeable batteries and in ultracapacitors, which are becoming increasingly commercialized but are not yet as popularly known.
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 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.
According to Ruoff, "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."
This technology has the promise of significantly improving the efficiency and performance of electric and hybrid cars, buses, trains and trams.
Even everyday devices such as office copiers and cell phones benefit from the improved power delivery and long lifetimes of ultracapacitors.