adding more external tanks and replacing the spent electrolyte as you go. In fact, Imergy has plans to build a giant battery module inside a 40-foot cargo container that would contain two power control boxes, two parallel stacks of ion-exchange cells, and an apartment-sized tank of electrolytes (which, admittedly, sounds complicated).
In this configuration, Imergy’s system could supply up to 250 kilowatts of electricity for up to four hours. That’s enough to power a school, a small hospital, or a village with 30 homes.
The company hopes to have these big modules on the market by September 2015. Its biggest units, right now, have a capacity of 10 to 30 kilowatt-hours; they cost $10,000 to $15,000, or about $500 per kilowatt-hour. The company expects to bring that cost down as it scales up its factories in California and India, which it’s doing in partnership with contract electronics manufacturer Flextronics. “We think we can go commercial for under $300 per kilowatt-hour in acquisition costs,” Watkins says. “The cheapest lithium battery we know of is $2,100 per kilowatt-hour.”
Imergy doesn’t have the flow-battery market to itself. A Sunnyvale, CA startup called Enervault, for example, believes iron-chromium electrolytes are still viable, and is building a demonstration system that it plans to connect to a solar array in California, according to a report in Technology Review. A Portland, OR, startup called Energy Storage Systems has won a $1.75 million ARPA-E grant to test an all-iron flow battery that it says performs better than vanadium batteries. Defense giant Raytheon, meanwhile, is investigating zinc-bromine flow batteries for military applications.
Imergy, for its part, just raised an additional $10 million from three of its longtime investors investors—NEA, Blue Run Ventures, and Technology Partners—and is working to raise an additional $20 million from strategic investors. The new name, a combination of “imagination” and “energy,” was needed because the old Hindu name, Deeya, reflected the company’s previous focus on the Indian market, Watkins says.
Developing economies will always have a need for backup and off-grid power, but there’s also a burgeoning demand for energy storage here in the United States. In October, the California Public Utilities Commission mandated that the state’s three big investor-owned utilities—Southern California Edison, Pacific Gas & Electric, and San Diego Gas & Electric—purchase a total of 1,325 megawatts of grid storage capacity by 2020, as a way to balance intermittent wind and solar resources and ensure that enough power is available during periods of peak demand. That’s likely to put billions of dollars into the pockets of energy storage providers.
Imergy plans to focus first on “microgrid” and commercial and industrial opportunities first, but utility-scale applications are on the company’s roadmap. Utilities “need a way of storing excess energy and deploying it when suitable,” says Watkins. “They need a solution that is reliable and cost-effective, and that is the story we have here.”
