A startup called Primus Power has received $11 million in venture capital to help it build the first full-scale version of a new, low-cost flow battery. The company earlier received $18 million via multiple government grants. Its battery is designed to help stabilize the power grid, making electricity cheaper, and making it easier for utilities to integrate intermittent renewable power sources like wind and solar.

Primus Power is trying to overcome one of the fundamental problems that have plagued flow batteries. The technology, in theory, at least, could be one of the cheapest forms of grid storage, since it requires inexpensive and abundant materials. But in practice, flow batteries have been very expensive, in part because they're large and have to be custom-built on site. Primus is hoping get around this with a new design that can be mass-produced in factories.

The need for such batteries has been growing as utilities anticipate increases in demand that could overload the power grid. Also, many states, most notably California, require the use of large amounts of renewable energy, but because such forms of energy are intermittent, it's difficult for utilities to maintain the match between supply and demand needed to prevent blackouts.

Batteries could even out the spikes in supply and demand by rapidly charging or delivering power to the grid, preventing blackouts and reducing the need for new power lines. But they've been too expensive for widespread use. In almost all cases, it's cheaper to build new power lines or to use natural gas power plants to make up for changes in power output from solar and wind plants. While Primus Power's technology is still too expensive to solve all of the energy storage problems on the grid, it will have many uses.

With flow batteries, a mixture of electrolyte and energy storage materials are stored in massive tanks—some as large as 10 meters high and 20 meters wide—and then pumped into a device where current is generated. Because flow batteries use cheap materials such as water-based electrolytes and energy storage materials made of abundant materials such as iron and zinc, the initial high costs could come down once enough of them are built, says Haresh Kamath, a senior project manager for energy storage at the Electric Power Research Institute, a nonprofit research organization supported by the electricity industry. But so far, the high cost of initial demonstration projects has stifled investment.