Originally published August 25 2013
Battery breakthrough? Membraneless 'flow battery' stores 10 times the energy of lithium-ion
by J. D. Heyes
(NaturalNews) New technology developed at MIT could revolutionize storable energy power, according to information recently released by the school.
Researchers at the Massachusetts Institute of Technology have managed to engineer a new rechargeable flow battery that isn't reliant on costly membranes to both generate and store electricity. Developers say that the device could one day enable cheaper, large-scale energy storage of the kind necessary to seriously advance green energy production.
The palm-sized prototype generates three times as much power per square centimeter as other membraneless systems - a power density that is an order of magnitude higher than that of many lithium-ion batteries and other commercial and experimental energy-storage systems.
The device stores and releases energy in a device that relies on a phenomenon called laminar flow: Two liquids are pumped through a channel, undergoing electrochemical reactions between two electrodes to store or release energy. Under the right conditions, the solutions stream through in parallel, with very little mixing. The flow naturally separates the liquids, without requiring a costly membrane.
'Remove the membrane'
The institute says reactants in the battery are liquid bromide solution and hydrogen fuel. The research group said it chose the bromine because it is a relatively inexpensive chemical that is available in large quantities. More than 243,000 tons of bromine are produced in the U.S. annually.
Besides the substance's low cost and availability, the chemical reaction between it and the hydrogen has great potential to store energy. But, MIT said, fuel-cell designs based on the two compounds have thus far had mixed results. Hydrobromic acid forms, which tends to destroy a battery's membrane, thereby slowing the energy-storing reaction and reducing the battery's overall life.
In order to fix the problem, the research team came up with a simple solution: remove the membrane.
"This technology has as much promise as anything else being explored for storage, if not more," Cullen Buie, an assistant professor of mechanical engineering at MIT, said. "Contrary to previous opinions that membraneless systems are purely academic, this system could potentially have a large practical impact."
Along with Martin Bazant, a chemical engineering professor, and William Braff, a graduate student in medical engineering, Buie has published the project's findings in Nature Communications.
"Here, we have a system where performance is just as good as previous systems, and now we don't have to worry about issues of the membrane," Bazant said. "This is something that can be a quantum leap in energy-storage technology."
Big news for renewables?
The findings could mean big advances for solar and wind power. Per MIT:
Low-cost energy storage has the potential to foster widespread use of renewable energy, such as solar and wind power. To date, such energy sources have been unreliable: Winds can be capricious, and cloudless days are never guaranteed. With cheap energy-storage technologies, renewable energy might be stored and then distributed via the electric grid at times of peak power demand.
"Energy storage is the key enabling technology for renewables," Buie said. "Until you can make [energy storage] reliable and affordable, it doesn't matter how cheap and efficient you can make wind and solar, because our grid can't handle the intermittency of those renewable technologies."
By removing the membrane, Buie said the research group managed to remove two large barriers to abundant energy storage - cost and performance. Often, membranes are the most expensive of battery components, as well as the most unreliable, as they are prone to corrode with repeated exposure to key reactants.
During experimentation, Braff and his colleagues managed to operate the flow battery at room temperature over various flow rates and reactant concentrations.
"They found that the battery produced a maximum power density of 0.795 watts of stored energy per square centimeter," the press release said.
"We have a design tool now that gives us confidence that as we try to scale up this system, we can make rational decisions about what the optimal system dimensions should be," said Bazant. "We believe we can break records of power density with more engineering guided by the model."
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