Iron-air batteries: ‘Eco-friendly’ storage solutions for renewable power

“We have to build batteries that are not just inexpensive but also environmentally friendly, because renewable and other forms of sustainable energy generation are,”

Economical and yet effective means of storing energy are necessary for maximizing the benefits of renewable energy. But in the rush to develop energy storage for renewable energy generation, scientists say we must make sure the solution is environmentally acceptable.

“We have to build batteries that are not just inexpensive but also environmentally friendly, because renewable and other forms of sustainable energy generation are,” said Sri Narayan a professor of chemistry at the University of Southern California’s Dornsife College of Arts and Sciences.

“We negate our original objective when people propose exotic battery systems with toxic materials in them,” Mr. Narayan told EcoSeed.

As an example, Mr. Narayan pointed towards lithium-ion batteries, a popular form of rechargeable, high-energy density material often used in personal devices but made with expensive materials that can be problematic to dispose of.

What Mr. Narayan and a team of researchers he led developed is an iron-air battery, one that uses the chemical energy generated by the oxidation of iron plates when exposed to air. They believe it can provide a cheap, rechargeable and eco-friendly means to store energy from solar and wind power plants.

Old idea to solve new problems

The idea behind an iron-air battery is not new. During the oil crisis of the 70’s and the 80’s, there was considerable interest in developing this kind of battery, mostly for use in vehicles. However interest waned as oil prices came down.

But with oil and fossil fuels having been recognized as finite resources, the researchers decided to take another look at iron-air batteries as large but inexpensive large energy storage systems for renewable energy projects. As the materials for an iron-air battery are easy to obtain, it cuts the costs of the entire system.

Mr. Narayan’s team was able to enhance the energy efficiency of iron-air batteries by suppressing a competing chemical reaction known as hydrolysis. Hydrolysis generates hydrogen gas and causes a loss of as much as 50 percent of the battery’s energy.

The team managed to reduce the energy loss from hydrolysis to 4 percent, making their iron-air battery around 10 times more efficient than their predecessors.

“A laptop battery, usually a lithium-ion battery, can store about 150 watt-hours per kilogram. We can store very close to that number and with the improvements we are continuing to make, we should be able to attain that number,” said Mr. Narayan.

To shut down wasteful hydrogen generation, the team added a very small amount of bismuth sulfide, an active ingredient in over-the-counter stomach remedy, into the battery.

The use of bismuth doesn’t just keep down hydrogen production, but it will also ensure that the battery keeps its “eco-friendly” promise. Other materials that might be able to get the same reaction are the toxins lead and mercury.

Flexible and scalable system

The iron-air batteries are meant to be used as part of a modular system.

“Typical modules would be somewhere in the range of 25 to 50 kilowatt-hours. If we want a megawatt hour of energy stored, then we would add 20 or so modules and so on,” said Mr. Narayan.

The modular nature of the storage system would not only allow for greater flexibility by tailoring it to meet specific demands. It would also make things easier from a maintenance stand point.

“If something goes wrong, you can just take out a module to replace it, rather than having to replace a large system,” he said.

As currently developed, the iron-air batteries have the capacity to store between eight and 24 hours’ worth of energy. A patent is pending on the technology with both the federal government and a California utility expressing interest.

The project was funded by the Department of Energy’s Advanced Research Projects Agency for Energy.

“It won’t be sitting in the lab to much longer,” Mr. Narayan shared with EcoSeed.

Mr. Narayan believes that the next two to three years would see the batteries being demonstrated on a large scale, with actual market penetration taking anywhere from three to five years.

The ARPA-E funding will support another year of research and development efforts after which larger prototypes will be developed to enable the technology to go into the market. The team is already working on finding outside companies to pursue this next step. –



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