ESS is a manufacturer of iron flow batteries in the state of Oregon. At the present time, lithium-ion batteries account for about 85% of grid-scale energy storage. That technology is time-tested and reliable. Prices continue to fall, but lithium-ion batteries have some issues.

They use materials like lithium, cobalt, manganese, aluminum, and nickel that can be expensive, especially if they are in short supply. They can also catch fire and begin to degrade after thousands of charge/discharge cycles. But the biggest issue with lithium-ion batteries is they can only put stored electricity back into the grid for 2 to 4 hours.

Iron flow batteries use three of the most abundant elements on Earth — iron, salt, and water. They consist of two storage tanks with a membrane between them. The membrane allows electrons to flow back and forth between the tanks while keeping the liquids separate.

If that sounds easy, it’s not. Getting the right mix of iron, salt, and water is critical, and creating a membrane that lasts a long time is no easy thing. But ESS has products ready to go and has just signed a deal with SB Energy, a division of SoftBank, to provide 2 gigawatt-hours (GWh) of its iron flow batteries between now and 2026. The first of the batteries will be deployed at a solar power plant in Davis, California this month.

In a press release, Rich Hossfeld of SB Energy says, “ESS’s unique ability to manufacture and ship batteries using iron, salt, and water is a game-changer, enabling SB Energy to offer our customers safe, sustainable and low-cost energy storage today. Long duration storage is absolutely critical to providing flexible, affordable renewable energy at scale and aligns perfectly with the Biden administration’s ambitious clean energy initiatives. SB Energy is excited to continue its partnership with ESS and deploy the company’s domestically manufactured batteries into the vast and rapidly growing market for energy storage.”

Eric Dresselhuys, CEO of ESS CEO, agrees. “This agreement exemplifies the accelerating demand for long-duration energy storage and reinforces our strong partnership with SB Energy to supply safe and sustainable technology built in the US. The energy transition will require massive amounts of storage capacity in the coming years and we are focused on scaling up our manufacturing capacity to help meet that demand. We are fortunate to have such great partners as SB Energy and Breakthrough Energy Ventures and look forward to a long and expanding partnership.”

Dresselhuys adds, “This deal is really the culmination of years of work to show that there’s a better mousetrap out there that solves more problems and is better for where the grid is going. Once people see that we’ve been vetted and tested and approved by partners like SB, that provides a lot of confidence.”

Image credit: ESS Inc.

ESS claims its flow batteries last for more than 20,000 charge/discharge cycles and can provide energy for up to 12 hours. In addition, they have a life expectancy of 25 years and are easily recyclable when their useful life is over. The company says it uses the same electrolyte on both the negative and positive sides of the equation,which eliminates the cross-contamination and degradation that shortens the life of other flow batteries.

“Our patented electrode design and control system, coupled with our simple, yet elegant electrochemistry, allows you to operate longer, at higher efficiency and deeper discharge levels. Unlike typical batteries packaged as fixed cells or modules, a flow battery has significantly more energy storage capacity, which gives the user the flexibility to align both the power and amount of electricity stored precisely to a project’s requirements today and for the future.”

In addition to the deal with SB Energy, ESS has also been tapped by Enel to supply 17 of its shipping container-sized Energy Warehouse battery systems with a combined capacity of 8.5 megawatt-hours (MWh) to solar facilities in Spain.

Time-shifting is the operative concept when it comes to energy storage. Some people like to play to the grandstand and suggest smugly that the wind doesn’t always blow and the sun doesn’t always shine, and that’s why we need to keep thermal and nuclear generating plants functioning. But that blather misses the point.

As MIT noted in 2011,”The sunlight that reaches Earth every day dwarfs all the planet’s other energy sources. This solar energy is clearly sufficient in scale to meet all of mankind’s energy needs — if it can be harnessed and stored in a cost-effective way.” It says some 173,000 terawatts of solar energy strike the Earth every day — 10,000 times more energy than necessary to meet the energy needs of the entire human race. And it’s free, people! All we need to do is figure out how to harvest it, store it, and distribute it. That’s where time-shifting comes in. Generate it now, store, and use it later when the sun is over the horizon.

No one is suggesting the ESS iron flow batteries are the only solution to energy storage, but at a projected cost of around $25 per kilowatt-hour, they clearly should be part of the mix of available energy storage technologies.

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