April 13th, 2020 by Tina Casey, Clean Technica
The renewable energy transition sure makes for some strange bedfellows these days. The latest example is a new energy storage breakthrough from the University of California’s Loker Hydrocarbon Research Institute in Los Angeles. The Loker Institute launched in the 1970s with a focus on fossil fuels and petrochemicals — think OPEC oil crisis and you’re on the right track — but more recently it has been pivoting into fresh new technology.
Energy storage (flow battery) designed for renewable energy (image by USC via Eurekalert).
More & Better Energy Storage For Renewable Energy
The new Loker Institute research involves flow batteries. That’s an area of particular interest for wind and solar fans, due to its potential for rendering utility-scale energy storage at a relatively low cost.
Flow batteries are based on the chemistry that produces electricity when two specialized liquids flow next to each other, separated only by a thin membrane.
Orchestrating the interaction is more complicated than it may seem, but there is a huge energy storage payoff for whoever can figure it out. Flow batteries can be recharged without degrading the way conventional batteries do. They can also provide energy storage over long periods of time, because the two liquids can be stored indefinitely in their own tanks until somebody needs electricity.
Flow batteries are already working their way into the marketplace, but researchers are still tinkering around with various ways to keep flow battery costs down while reducing the use of toxic chemicals. Much of the attention has been focused on finding organic compounds for redox flow batteries.
The Organic Energy Storage Solution
The Loker Institute team is among those searching for just the right organic compound. Back in 2014, USC summed up the state of its research, explaining that “through a combination of molecule design and trial-and-error, the scientists found that certain naturally occurring quinones — oxidized organic compounds — fit the bill.”
“Quinones are found in plants, fungi, bacteria and some animals, and are involved in photosynthesis and cellular respiration,” USC helpfully added.
So, there’s your organic compound — now what?
Next Steps For Cutting-Edge Energy Storage
The initial energy storage research was compelling enough to catch the eye of the Energy Department’s cutting-edge funding office, ARPA-E, and the office has continued to provide financial support for the effort.
Now it looks like all that hard work is about to pay off.
In addition to identifying their quinone — anthraquinone disulfonic acid, to be precise — the Loker flow battery research team also targeted iron sulfate to solve the second part of the puzzle.
The two compounds have been used in prior research, but only in different flow batteries. According to USC, this is the first time they have been combined in a single flow battery.
The proof is in the pudding. Last week, the Journal of the Electrochemical Society published a report by the Loker research team that demonstrates the efficiency of the quinone-based technology under the title, “A Durable, Inexpensive and Scalable Redox Flow Battery Based on Iron Sulfate and Anthraquinone Disulfonic Acid.”
Among other findings, the authors write that “cycling studies of over 500 cycles in the symmetric cell configuration show a negligibly low capacity fade rate of 7.6 × 10−5% per cycle” and “a notably high average coulombic efficiency of 99.63%.”
Got all that? Good! For a plain-language account, let’s turn to the lead author of the study, USC Professor of Chemistry and Electrochemistry Sri Narayan.
“We have demonstrated an inexpensive, long-life, safe and eco-friendly flow battery attractive for storing the energy from solar and wind energy systems at a mass-scale,” Narayan says.
How Low Can Energy Storage Go?
As for the cost of this new energy storage breakthrough, USC notes that iron sulfate is an abundant byproduct of the steel industry that currently goes for about 5 cents per pound.
The anthraquinone disulfonic acid end of things is a bit more challenging, but the research team estimates that a scaled-up production system should be able to pump it out at the rate of $66.00 per kilowatt hour.
There may also be a green twofer involved. Co-author and Loker Institute director Surya Prakash pointed out that just about any carbon-based feedstock can be deployed to produce anthraquinone disulfonic acid, including carbon dioxide.
In other words, the energy storage system of the future could do double duty as a carbon capture system while also storing wind and solar power.
Try that with your coal mine…
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Image: Schematic of flow battery by USC via Eurekalert.