NREL.GOV — Often one innovation begets another. Take photovoltaics: the panels’ elegant tilt toward the sun leaves a sizable space behind them, especially if they are installed on a flat roof.

That’s a lot of space, especially for design engineers whose job it is to pack things in as tightly as possible. What could go there? Why not a battery?

For years, the dream has been to develop a battery system that could withstand the heat, the cold, the rain—the general harsh conditions outside—in order to take advantage of this space.

Most behind-the-meter battery systems—such as those built to save commercial building owners thousands in demand charges—are sensitive creatures. They often need climate control, sometimes their own ventilation system, and most critically, real estate: significant floor space in a busy factory, hospital, or hotel.

Taking those batteries off the floor and fitting them in that unused space behind PV panels is the goal of Yotta Solar, an Austin-based startup that is working with NREL to characterize its prototype battery unit under the auspices of the Wells Fargo Innovation Incubator program.