A low-cost, high-performance battery chemistry developed by University of Colorado Boulder researchers could one day lead to scalable grid-level storage for wind and solar energy that could help electrical utilities reduce their dependency on fossil fuels.
The new innovation, described today in the journal Joule, outlines two aqueous flow batteries, also known as redox flow batteries, which use chromium and organic binding agents to achieve exceptional voltage and high efficiencies. The components are abundant in nature, offering future promise for cost-effective manufacturing.
“We’re excited to report some of highest performing battery chemistries ever, beyond previous limits,” said Michael Marshak, senior author of the study and an assistant professor in CU Boulder’s Department of Chemistry. “The materials are low-cost, non-toxic and readily available.”
Renewable energy sources provide a growing share of U.S. electrical production, but currently lack a large-scale solution for storing harvested energy and re-deploying it to meet demand during periods when the sun isn’t shining and the wind isn’t blowing.
“There are mismatches between supply and demand on the energy grid during the day,” said Marshak, who is also a fellow in the Renewable and Sustainable Energy Institute (RASEI). “The sun might meet the grid’s needs in the morning, but demand tends to peak in the late afternoon and continue into the evening after the sun has set. Right now, utility companies have to fill that gap by quickly revving up their coal and natural gas production, just like you’d take a car from zero to sixty.”
Although lithium ion can provide power for smaller scale applications, you would need millions of batteries to backup even a small fossil fuel power plant for an hour, Marshak says. But while the lithium ion chemistry is effective, it’s ill-suited to meet the capacity of an entire wind turbine field or solar panel array.
“The basic problem with lithium ion batteries is that they don’t scale very well,” Marshak said. “The more solid material you add, the more resistance you add and then all of the other components need to increase in tandem. So in essence, if you want twice the energy, you need to build twice the batteries and that’s just not cost-effective when you’re talking about this many megawatt hours.”
Flow batteries have been identified as a more promising avenue. Aqueous batteries keep their active ingredients separated in liquid form in large tanks, allowing the system to distribute energy in a managed fashion, similar to the way a gas tank provides steady fuel combustion to a car’s engine when you push the pedal.
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