TOM BEARDEN, NewsHour correspondent: Solar panels like these may soon spread over 500,000 acres of California's Mojave Desert and on public lands in many other states. Wind farms have already sprouted in 28 states, and more are on the way.
The Obama administration wants to spend $209 billion on renewable energy projects like these over the next 10 years, but there's a huge obstacle to renewables taking a larger share of the nation's utility burden: What happens when the sun isn't shining and the wind isn't blowing?
Two scientists at the Massachusetts Institute of Technology are experimenting with innovative approaches that might provide a way to store renewable energy.
DON SADOWAY, Massachusetts Institute of Technology: Just above us is the Radiation Laboratory where radar was first practiced.
TOM BEARDEN: Professor Donald Sadoway often jokes about the long, dark hallway that leads to his subterranean battery laboratory. He says the biosciences get better spaces because they're currently considered sexier.
DON SADOWAY: It's interesting how the upper electrode has more curvature to it.
TOM BEARDEN: But Sadoway and his group of graduate students think what they're doing might turn out to be just as important.
DON SADOWAY: This is the key to enabling renewable energy. The big problems in photovoltaics, solar, and wind is storage. And you can't just go to the auto store and buy a whole bunch of lead acid batteries and lie them down in a field. You've got to have high-density, high-powered energy storage capability, and so the battery is the key enabling technology.
TOM BEARDEN: Sadoway's research is focused on what batteries are made of and how to scale them up to store large amounts of electricity. All batteries have an anode, where a current flows in, and a cathode, usually made of metal, where a current flows out. Both are immersed in a liquid electrolyte, something that conducts electricity.
Since Alessandro Volta invented the battery in 1800, scientists have been experimenting with various materials. Most of us have heard of some of these ingredients because today's batteries are often described by what's inside: lithium ion, nickel cadmium, lead acid.
But the Sadoway group is trying something completely different. They're experimenting with batteries that contain liquid metals heated to high temperatures.
DON SADOWAY: So this is a battery that's designed for large-scale energy storage. We're talking here about in the extreme grid level storage, also important for things like renewables, solar and wind.
And it's a very, very different design. It consists of three liquid layers, so we call it liquid battery. There's no solid in here, except for, obviously, the case. But we have a liquid metal on top of a liquid salt on top of a liquid metal, and the two liquid metals are two different electrodes.
And they naturally -- they separate, sort of like salad oil and vinegar, because when you're storing the grid, you've got to be able to store not just a lot of energy, but take it down and give it back at very, very high current rates. So we need megawatt hour storage at megawatt power delivery rates.
TOM BEARDEN: This is just a small test device. Sadoway envisions liquid metal batteries the size of electrical substations routinely storing megawatts of power generated by solar collectors during the day or by wind farms. Sadoway is also working on much smaller batteries for more common applications, like this thin, flexible design that, unlike most, contains no liquid at all.
DON SADOWAY: You can imagine, in biomedical applications, this thing can't leak if the case is punctured. You know, if you want to change the batteries in the watch, you change the band.
It opens up new design possibilities, impregnating fabrics, draperies with photo detectors, and then having a flexible battery so that the drapes actually harvest light and then give back electricity when it's dark. And you can't do that if you've got batteries that have the form factor of the regular right circular cylinder that will break your toe if you drop the thing.