Primus Power is replacing large storage tanks with cells the size of hot water tanks. This approach sacrifices some of the potential cost savings of large storage tanks, but it more than makes up for this with the savings possible from mass production in a factory, says Primus CEO Tom Stepien.
The company is also using novel zinc-based energy storage materials and a better design to increase the power output of the battery by about four to five times. These changes would allow for smaller, cheaper batteries that use less material, and that can be easily installed on existing utility property, such as at substations. The system, which is stored inside shipping containers, is portable. This can be a boon for utilities that need battery systems temporarily while waiting for new power lines to be installed. Some other companies are also working on modular systems, but these still use relatively large components capable of delivering one megawatt each or more. Primus Power is taking this approach further—its cells are smaller, delivering only 20 kilowatts each.
Primus Power joins about 20 other companies that are attempting to make cheaper flow batteries. It’s aiming to reach costs near $500 per kilowatt hour of storage capacity. (It will be at least a year before the company can quote solid cost figures, Stepien says.) This would be much cheaper than ones that have been made so far, according to Kamath. Companies often don’t disclose their costs, but he estimates that many are upwards of $2,000 per kilowatt hour.
At $500 per kilowatt hour, the batteries would be cheap enough for widespread use on the grid for applications such as deferring power line construction, Kamath says. It would also be substantially cheaper than the technology’s key competitor now—lithium-ion batteries—which cost about $1,000 per kilowatt hour, he says. But it would still be too expensive to meet the U.S. Department of Energy’s goal of energy storage systems that cost less than $100 per kilowatt hour.
If flow batteries could supply power for as little as $100 per kilowatt hour, they’d be a cheaper option for utilities than the installation of a new fossil-fuel-based power plant to offset the daily variations in wind or solar power, Kamath says. Primus Power recently won a grant from the DOE’s Advanced Research Projects Agency for Energy to develop such a low-cost battery, but that will be a different design than the one it is currently scaling up, and the company isn’t saying much about it yet.
Many other experimental storage technologies are being developed to reach these low costs. A “semi-solid” flow battery technology being developed by a startup called 24M uses much higher concentrations of energy storage materials in the electrolytes, which means they can stores 10 times as much energy as conventional flow batteries. A startup called Liquid Metal Battery is commercializing a battery that uses electrodes and electrolytes that are made of molten metals and salts.