If the world is going to get off of fossil fuels, we’re going to need batteries—big batteries, and lots of them, to smooth out intermittent power sources like wind and solar. But we aren’t doing nearly enough to develop the technologies that will allow us to build the cheap, grid-scale storage we need, according to Don Sadoway of MIT.

Sadoway is the cofounder of a grid battery startup called Ambri that’s trying to find a solution. Its technology, inspired by aluminum smelters, uses two liquid metals as electrodes and a salt electrolyte to form a battery cell. But it’s not alone: other startups, including Eos Energy Storage, Aquion, and Sun Catalytix, are all trying to build similar devices.

One thing unifies them: they all have ambitions to build cheap electricity storage using abundant materials. “To make something dirt cheap, make it out of dirt,” Sadoway quipped during his talk at EmTech MIT 2016 on Wednesday. “Using rare elements in battery technology cannot scale.”

And dirt cheap is certainly what they have to aim for. Currently, around 99 percent of grid storage is in the form of “pumped hydro”—where water is pumped uphill when there’s electricity to spare, then released to turn a generator during times of demand. It's far cheaper per kilowatt-hour of storage than today's grid-scale batteries, and they won't be widely adopted until they can compete on cost.

Progress toward that goal, though, is slow. These startups don’t just have to develop new kinds of electrochemistry using common elements—they have to build a finished product that’s affordable and works all the time. And there are many bumps along the road to development that can slow progress.

Money can help. But while the U.S. government spends $5 billion per year on energy research, according to Sadoway not enough of it is being directed toward research that will enable grid batteries. “Right now, the vast majority of battery technology funding is going toward incremental improvements in lithium-ion,” he explained. “We have to have the courage to say we’re looking for audacious ideas that, if they succeed, can be hugely impactful.”