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The promise of flow batteries

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Flow battery startup EnerVault recently demo’ed a 250 kilowatt battery that helps power an almond farm in Northern California. The deployment, which was heavily aided by grants from the California Energy Commission and the Department of Energy, was intended to show the potential of flow battery technology as a small group of ambitious entrepreneurs attempts to tackle the nascent energy storage market.

Its early days in the energy storage market as California became the first state last fall to mandate 1.3 gigawatts of energy storage from three utilities. But globally, all markets from Germany to Italy to Arizona, places where significant amounts of solar and wind energy have hit the grid, will have to soon contend with the need to provide power on demand for when the sun isn’t shining and the wind isn’t blowing. (For a full analysis of the battery storage market, see my report, “How renewable energy deployment is spurring the grid battery storage market.“)

I caught up recently with Primus Power’s CEO Tom Stepien, who had just returned from Kazakhstan where he’d gone to meet with officials about the role battery storage will play in the country’s ambitious renewable energy plan. Primus Power employs zinc flow battery technology that distinguishes itself from other flow batteries by getting rid of the separator/ionic filter which is expensive and can limit a battery’s life cycle. Additionally the battery uses a metal electrode, which is costlier but enables a magnitude greater power, as well as a single flow loop.

At the startup stage that we’re at, every battery technology company has invested considerable capital in trying to produce novel engineering that can maximize reliability, life cycle and energy density while keeping capital costs down.

The argument for flow battery technology has centered around scalability. As power demand grows and renewable energy deployment increases, we’re likely dealing with a dynamic system where grid operators may want to be able to slowly add battery storage over time. Interestingly, some solar advocates have used this argument in the case of solar energy, arguing that unlike natural gas peaking power plants, which can be expensive and must be deployed in one shot, solar can be added incrementally.

Scalability occurs by increasing the size of the tanks. Leggoing systems together is another option, which is the one Primus is employing, since the battery systems are modular and put in shipping containers.

“It changes the planning dynamics at a utility,” Stepien noted. “A utility that wants to install a gas system needs to think five or six years in the future. If instead, you have a mobile home approach, that changes the whole planning dynamic because you don’t have to think 4-5 years in advance. You can think a quarter or 5 or 6 months in advance. And you can pay for it in operating dollars versus a bond.”

As is the situation for many other battery startups, the big utility scale opportunities driven by renewables are not quite there yet. Rather the opportunities are often in simple cost avoidance.

Primus Power is delivering two battery pods to Puget Sound Energy this year that will serve as a deferral of a distribution substation, a situation on Bainbridge Island where Primus’ flow batteries will help the utility avoid having to build a substation to meet winter heating demand response. Primus is also seeing microgrid interest as the startup has been selected to install a backup battery system as part of the microgrid at the Miramar Marine base in San Diego. As time of use electricity pricing increases, Stepien also believes he’ll see battery storage pencil out for big commercial power users that want to avoid demand charges during peak periods.

It remains very early in the energy storage market, but flow battery technology’s scalability offers advantages. And if economies of scale can be improved, we may well see the very necessary reduction in capital costs of battery storage, which has been the major problem for the market. In a changing world where energy storage options increase and prices decrease, we’re likely to see more diverse applications of batteries driven by cost savings.