After a decade of development and some corporate rebranding, Imergy Power Systems has unveiled a next-generation vanadium flow battery the company claims will dramatically lower costs and boost performance over competing battery chemistries by using a recycled vanadium electrolyte.

Demand for cost-effective energy storage has grown as intermittent renewables likesolarand wind become cheaper and integrate onto the grid in higher volumes. Batteries also have applications in demand response, energy shifting and backup power.

Flow batteries are one of the most promising storage options. They have the potential to be cheaper and more flexible than lithium-ion competitors, and the design of a flow battery circulates the electrolyte through two tanks that can be sized to match various loads. Vanadium flow batteries are particularly appealing because they use a single electrolyte in both tanks, which prevents cross-contamination -- a significant issue with other flow battery chemistries that use more than one element.  

Vanadium flow batteries can also last much longer than other batteries because the vanadium electrolyte doesn’t degrade over time. In contrast, chemical reactions inherent to lithium-ion batteries will cause them to lose capacity over repeated charge and discharge cycles.

“Vanadium doesn’t go away, it doesn’t get consumed…even after 25 to 35 years,” said Timothy Hennessy, Imergy’s president and COO, in an interview. “Whatever you put in, you get back out.”

The company’s new 50-kilowatt battery comes with a minimum twenty-year cycle life and can store up to 200 kilowatt hours of electricity. The power and capacity of the ESP30 series are well suited for both short- and long-duration storage, with available energy ranging from two to twelve hours of output.

The ability to store energy for hours at a time could help to address California’s so-called duck curve, where there’s a risk of over-generation from solar projects during the afternoon when the sun is shining and the need for ramping in the evening as solar drops off. Longer-duration batteries like vanadium flow batteries help to shift that PV power to later in the day.

The demand for storage isn’t unique to California. New Jersey today launched a solicitation seeking solutions for storing electricity generated by renewable sources so it can be used when electric demand peaks or during power outages.

One of the challenges with vanadium flow batteries is that they are far less energy-dense than lithium-ion batteries. But over the last several years, the Department of Energy’s Pacific Northwest National laboratory (PNNL) has developed a new vanadium electrolyte that could improve the energy density by more than 70 percent.

Imergy is one of three companies to license a new vanadium electrolyte developed by PNNL. Mukilteo, Wash.-based UniEnergy Technologies and Massachusetts-based startup WattJoule have also licensed PNNL technology.

Cost has been another hurdle for vanadium batteries. Vanadium is abundant but expensive to extract from the ground. And existing vanadium batteries have only been able to use a pure form of the electrolyte in order to prevent hydrogen from building up, which adds cost to the battery.

New chemistry, new opportunities

Imergy's ability to use recycled vanadium sets it apart. The company claims it’s the first to use secondary resources of vanadium from mining slag, fly ash and other environmental waste. The company’s unique chemistry also allows the battery to remain stable up to 131 degrees Fahrenheit without the need for cooling.

“Our chemistry is able to mask any side reactions, so we’re able to buy dirty vanadium or vanadium that is less pure vanadium, which means we can get a completely different pricing structure from what’s on the market,” said Hennessy. “Probably half of what you see priced in the forward market or the metal exchange in London.”

As a result of its patented technology and other developments, Imergy will lower the cost of its flow batteries from $500 per kilowatt-hour, which already beats competitor offerings, to $300 per kilowatt-hour.

Because vanadium is recyclable and doesn’t get consumed during use, battery purchasers can also recuperate up to 40 percent of the battery cost by selling it back to the market. Imergy is already starting to sign contracts to buy back vanadium from its customers once the battery reaches its 25-year lifetime.

Getting to this point has been a challenge. Imergy was formed last year out of Deeya Energy when that company decided to walk away from developing an iron-chrome chemistry after four years of research.

Upon relaunching, Imergy adopted its new chemistry and attracted Bill Watkins, former head of the disk drive maker Seagate and CEO of LED company Bridgelux. He brought on board Hennessy, who was previously president of flow battery maker Prudent Energy, and Jack Jenkins-Stark, the former CFO of solar developer BrightSource Energy.

The company, which has raised $100 million from Technology Partners, NEA, Blue Run and other investors, currently has about 100 employees split largely between the U.S. and India. Approximately 75 of Imergy’s smaller battery units have already been deployed in India to serve telecommunications towers and small villages.

Part of the new executive team’s strategy going forward has been to establish Imergy as a battery outsourcer, as opposed to a battery manufacturer, in order to leverage the speed and geographical advantages of existing manufacturing companies like FoxConn Technology Group or Flextronics International.

“The key is we can ramp very fast. We don’t have to spend $5 billion to put together a high-tech plant,” said Hennessy, referring to Tesla Motors’ lithium-ion battery Giga factory. “And everything we have is off-the-shelf. There are no rare earth or environmentally damaging materials with disposal issues.”

Imergy has already sold the first six of its new ESP30 units to sites in Southern California and India where they’ll be connected to PV arrays, microgrids and U.S. military installations.  

The company’s third product size soon to be made public will be a 40-foot container with 250 kilowatts of power designed to be stacked for utility-scale projects. Imergy hopes to release that product by the middle of next year.