ESS Makes 12+ Hour Flow Battery For Sustainable Energy Storage

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The siren call of the flow battery has lured many a renewable energy researcher with its promise of large scale, long duration energy storage. In contrast to conventional battery arrays that pour out the juice for four hours or so, flow batteries can store a day’s worth of wind or solar power. That kind of long duration output is something that the US Department of Energy has been dreaming about, and with that in mind let’s take a look at the flow battery specialist ESS Inc.

US Energy Department Hearts Long Duration Energy Storage

Even though the previous administration professed a love for all things fossil, the US Department of Energy has been holding the torch for energy storage and renewable energy all throughout the past four years. That includes a focus on flow batteries and other forms of long duration energy storage, and now it looks like all that hard work is about to pay off.

Flow batteries work through the magic that happens when two specialized liquids flow adjacent to each other, separated only by a thin membrane (or not, as the case may be). Scaling is simply a matter of building larger (or smaller) tanks to keep the liquids apart until needed.

So, what’s holding things up? Cost is one key factor. The Energy Department has tapped various federal labs and private companies to help push down the cost of flow batteries, and it looks like earth-abundant, low-cost, non-toxic iron has been tasked with the heavy lifting.

In 2016 the agency’s cutting edge energy R&D funding office, ARPA-E, awarded a $2. 8 million grant to ESS for the development of a new iron-based flow battery — and not just any old new flow battery.

“Energy Storage Systems (ESS) is developing a cost-effective, reliable, and environmentally friendly all-iron hybrid flow battery,” enthused ARPA-E. They went on to note that “The ESS flow battery technology is distinguished by its cost-effective electrolytes, based on earth-abundant iron, and its innovative battery hardware design that dramatically increases power density and enables a smaller and less costly battery.”

“Creating a high-performing and low-cost storage system would enable broad adoption of distributed energy storage systems and help bring more renewable energy technologies—such as wind and solar—onto the grid,” ARPA-E added.

ESS Brings The Iron To Long Duration Energy Storage

There being no such thing as a free lunch, back in 2016 ARPA-E noted that there was just one little thing in the way.

“Currently, flow batteries account for less than 1% of the grid-scale energy storage market because of their high system costs,” they explained.

Well, that was then. ESS showcased its all-iron flow battery at Intersolar North America in 2017 and reached another milestone in 2019 when the US Department of Defensea big fan of clean tech — installed the company’s Energy Warehouse™ flow battery at Marine Corps Base Camp Pendleton in San Diego, where renewable energy has been a thing since 2011. The new energy storage system complements an existing solar array and integrates with a CleanSpark microgrid for up to eight hours of storage.

In the latest development, earlier this week ESS launched a new version in the form of the Energy Center™, which it describes as a “flexible, scalable, and environmentally sustainable long-duration battery storage system.”

They’re not kidding. The Energy Center sports the next-generation of the ESS flow battery, which is good for 6 to 16 hours of energy storage, depending on scale. ESS also fine-tuned its containerized design to allow for stacking and other configurations, which provides for fitting and scaling the battery into existing facilities and campuses.

Energy Storage That Puts The Clean In Clean Tech

There is more to renewable energy than zero emission kilowatts, and industry stakeholders are beginning to pay more attention to cradle-to-grave lifecycle impacts including recycling and reuse as well as hazardous materials risks.

Some interesting activity is afoot in the field of conventional batteries, including the development of new chemistries that provide for a more sustainable lifecycle profile. Pumped hydro stakeholders are also looking for improvements that minimize the environmental footprint while lowering costs.

The flow battery field is also turning more attention to lifecycle issues and environmental impacts, and ESS is paying attention.

“The Energy Center utilizes an environmentally benign and sustainable flow battery chemistry composed of earth-abundant iron, salt, and water, and containing no hazardous chemicals or rare-earth metals,” ESS explains. “The iron flow battery presents no fire, chemical, or explosive risk, eliminating the need for fire suppression, secondary containment, and hazmat precautions, resulting in the greenest, most sustainable, and easiest-to-permit storage technology available.”

In a somewhat more dry review of the technology, a research team based at the University of California-Irvine included all-iron iron chemistry in an energy storage study published in the Journal of Cleaner Production last fall, in which the researchers describe the importance of focusing attention on energy storage lifecycle impacts.

“While a primary goal of increased renewable energy use on the grid is to mitigate environmental impact, the production of enabling technologies like energy storage systems causes environmental impact. Thus, understanding the impact of producing energy storage systems is crucial for determining the overall environmental performance of renewable energy from a systems perspective,” they wrote.

The team took a whole-of-systems approach and analyzed eight areas, including raw materials manufacturing. In a comparison of iron with vanadium and zinc flow battery chemistries, the team found that “production of all-iron flow batteries led to the lowest impact scores in six of the eight impact categories such as global warming potential, 73 kg CO2 eq/kWh; and cumulative energy demand, 1090 MJ/kWh.

“Our results indicate that materials options change the relative environmental impact of producing the three flow batteries and provide the potential to significantly reduce the environmental impact associated with flow battery production and deployment,” they concluded.

Renewable Energy Revolution: You Ain’t Seen Nothing Yet

Energy storage is the key to adding more wind and solar, so the interesting thing about all this is the timeline. In terms of sheer bulk, almost all of the energy storage technology supporting renewable energy growth so far in the US is good old fashioned pumped hydro, with conventional batteries running a solid but distant second.

Now imagine how rapidly the US — and global — economy could decarbonize if an additional high bulk, low cost energy storage technology were to burst upon the scene.

If you are, you are not alone. Last December ESS scored a mention in the 2021 edition of Cleantech Group’s annual top 100 list of sustainability companies and trends, for the third time in five years.

Stay tuned for more. Along with ARPA-E the company’s US partners include the Energy Department’s National Renewable Energy Laboratory and Wells Fargo (which has established a clean tech incubator in partnership with the lab), and an international cast of characters including Canada’s Switch Power, EU-based InoBat, and Power Africa.

Among the A-list investors backing the firm is  Breakthrough Energy Ventures, which grew out of the Bill Gates-backed Breakthrough Energy Coalition that launched itself in a publicity blitz around the signing of the 2015 Paris Agreement. At the time its focus appeared to be on nuclear energy but it seems that gears have been shifting since then.

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Image (cropped): All-iron flow battery courtesy of ESS.

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Tina Casey

Tina specializes in advanced energy technology, military sustainability, emerging materials, biofuels, ESG and related policy and political matters. Views expressed are her own. Follow her on LinkedIn, Threads, or Bluesky.

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