Enviro News - August 2012

Air-Breathing Battery Renewable Energy Storage Solution

Posted by Rebecca Watson - Enviro News Reporter on 03/08/2012 - 07:40:00

Renewable Energy Storage

USC researchers have developed an eco-friendly battery that could be the answer to renewable energy storage.

The team led by Sri Narayan, professor of chemistry at the USC Dornsife College of Letters, Arts and Sciences, created an air-breathing battery that works in a similar process to rusting. It uses the chemical energy generated by oxidisation when iron plates are exposed to oxygen in the air.

The storage of renewable energy is necessary to cover dark times at a photovoltaic plant or calm days a wind farm, but utility-scale battery storage is limited and expensive. Most of the power is stored via pumped-storage hydroelectricity, a process where water is pumped up into a reservoir then released through turbines to create electricity when needed.

However, significant losses can be made when the water is stored in open reservoirs due to evaporation, and the process is not really viable in areas prone to drought.

Renewable Energy Storage Solution

This is not the first time that iron-air batteries have made an appearance; there was a large interest spike during the 1970s energy crisis. However hydrolysis, the chemical reaction of hydrogen generation, competed with oxidisation within the battery and absorbed 50% of the battery's energy, rendering it too inefficient to use.

Narayan and his team managed to solve this issue by adding a tiny amount of bismuth sulfide to the battery, stopping the hydrolysis and reducing energy loss to just 4%.

"Adding lead or mercury might also have worked to improve the battery's efficiency, but wouldn't have been as safe," said Narayan, "A very small amount of bismuth sulfide doesn't compromise on the promise of an eco-friendly battery that we started with."

The batteries currently have the capacity to store between eight and twenty-four hours' worth of energy, and can be produced at 10% of the cost of rechargeable lithium-ion batteries.

Narayan's team, which includes fellow USC researchers G. K. Surya Prakash, Aswin Manohar, Souradip Malkhandi, Bo Yang, Robert Aniszfeld, Chenguang Yang, Phong Trinh and Andrew Kindler of NASA's Jet Propulsion Laboratory, are continuing to develop the technology. Their next step is to make the iron-air battery out of less materials, but able to store even more energy.

"Iron is cheap and air is free," says Narayan. "It's the future."

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