# Primus Power Raises $11M for Grid Flow Batteries Large tanks filled with fluids could be the next low-cost way to provide energy storage for the power grid. A quiet company called Primus Power is developing so-called flow batteries, and on Tuesday morning, announced it has raised a round of$11 million from a group of venture capitalists including DBL Investors, I2BF Global Ventures, Chrysalix Energy Venture Capital and Kleiner Perkins Caufield & Byers.

Primus Power has been building a flow battery farm that when completed offer between 25 MW to 75 MW on energy storage capacity for the Modesto Irrigation District. The battery farm will be Primus Power’s demonstration facility and will provide storage technology to make up for the variable nature of wind power in the area. The company said these new funds will go towards completing that facility and for wider scale commercialization.

While I don’t know all the intricacies of Primus Power’s technology, flow batteries, in general, use large storage tanks full of electrolytes and pumps that circulate the solution throughout the system (see image of Sumitomo’s tech). Flow batteries can be safer and more reliable (compared to lithium-ion batteries), can be lower cost than other forms of energy storage, and can be deployed relatively quickly. Some flow battery technology can run around $100 per kWh, compared to some batteries which can range in cost between$200 per kWh to $500 per kWh and up to$1,000 per kWh for more advanced batteries.

According to a Department of Energy website, Primus Power is working on an inexpensive metal electrode for a flow battery, and is also employing manufacturing processes common in high volume metal production to develop the electrode. Primus Power was awarded two grants from the Department of Energy for the innovation. Greentech Media reported earlier this month that the technology is based on a zinc bromine system.

Other startup flow battery makers include EnerVault and Deeya Energy. Deeya Energy is a 6-year-old company that has raised $53 million from Technology Partners, BlueRun Ventures, Draper Fisher Jurvetson and New Enterprise Associates and has redox flow battery inventor Lawrence Thaller as a technical adviser. EnerVault has raised$3.5 million in venture funding, from Oceanshore Ventures and U.S. Invest.