Flow Batteries: EnerVault Quietly Building Energy Storage for the Grid

Many technologies for storing energy on the power grid are either expensive (advanced batteries), mired in regulations (pumping water uphill and then letting the water move downhill) or just in a really early stage (the gravel-plus-heat-pump approach). But there is a technology that’s had decades of research, could offer one of the lowest cost options out there and is getting increasing attention from investors: flow batteries.

Flow batteries are similar to large fuel cells but generally use large storage tanks full of electrolytes and pumps that circulate the solution through the system. This week we had the chance to connect with Craig Horne, president and CEO of a quiet, year-old company called EnerVault based in Sunnyvale, Calif., that’s building flow batteries for energy storage for the power grid. Horne tells us that EnerVault’s flow batteries are competitive with the lowest-cost energy storage options on the market, are a good fit for distributed power needs (they can be plugged in next to a solar system or wind farm) and are safer and more reliable than other energy storage technologies like advanced batteries, which can easily become overheated.

Horne won’t tell us what the chemical solutions or design of the storage system are (EnerVault is still running under the radar, Horne says), but he and his team have strong backgrounds in energy storage through universities and startups. Horne himself is a chemical engineer from UC Berkeley (he gave a talk at the Berkeley Energy Storage conference) and has worked on energy storage technologies, from fuel cells to lithium-ion batteries, and worked at companies including NanoGram, NeoPhotonics, Kainos Energy and World Energy Labs. Other members of the company hail from fuel cell maker Bloom Energy, as well as other energy storage heavyweights.

So how cheap is EnerVault’s flow battery solution? Horne says it can run around $100 per kWh, but says that price could also come down when the company scales up production. In comparison, advanced lithium-ion batteries can cost between $500 per kWh on the low end to $1,000 per kWh for more advanced batteries with more expensive materials. Less advanced batteries can cost around $200 per kWh.

Well, first the company has to go into production. Horne says EnerVault is currently looking to raise its first round of funding to build a demonstration of the flow battery. Over the past few years venture investors haven’t been that interested in funding energy storage technology in general — it’s a complex topic and technology like flow batteries are bulky and industrial. But that’s starting to change as stimulus funds and government incentives spur more companies to pay attention to the remaking of the grid.

Earlier this month flow battery maker Deeya Energy closed a $30 million financing round from Technology Partners, BlueRun Ventures, Draper Fisher Jurvetson and New Enterprise Associates. Deeya — a 5-year-old firm that hails redox (dissolved liquid) flow battery inventor Lawrence Thaller as a technical adviser and has raised $53 million — is a hefty competitor. But the energy storage space is in the very beginning — or as Horne puts it, in “the Wild West” — development stage right now. Anything can happen.