6 Scientists on the Cutting Edge of Energy and Environmental Research

That effort, says Hugenholtz, who heads the institute’s Microbial Ecology Program, “was just the tip of the iceberg. It was just one species in one part of the gut.” The focus has since turned to grass-feeding termites, where discoveries might be even more applicable to commercial biofuel production, given the interest in cellulosic ethanol made from switch grass. “One of the goals is to find these novel enzymes, enzymes that haven’t been found before in other places,” says Warnecke.
These findings, in turn, are being compared with data from other animals that break down cellulose, including cows, wallabies, and birds. The DNA sequencing itself, Warnecke notes, offers only “a few clues” about which enzyme would be most efficient. “That would be the next step of the analysis,” he says. –Kent Garber

Daniel Nocera: Storing Solar Energy

Harnessing the sun’s power requires, first, capturing solar energy. That’s what solar panels do. But capture isn’t the only hurdle, says Daniel Nocera, director of the Solar Revolution Project at MIT. Finding an affordable way to store the energy for later use is crucial. “If you can only use the sun when it’s shining, you’re in trouble,” he says.

That’s why the inexpensive catalyst that Nocera has created, using cobalt and phosphate, is such a breakthrough. It efficiently splits water molecules into oxygen and hydrogen, elements that serve as fuel for energy generation. When the catalyst receives electricity from a solar panel’s photo¬voltaic cell, “it rips water apart to make oxygen,” he says. That process previously required an expensive catalyst or extreme heat, pressure, and low acidity; the new catalyst does the trick under standard conditions. “The hard part of water-splitting was getting the oxygen out,” he says. What’s left can be readily stored as hydrogen.

Using solar energy, the average American household would need to split a bit more than a gallon of water a day to provide it with ample fuel for its electricity needs. Homes with energy-storage capacity ¬wouldn’t even need to be on the electrical grid, Nocera says.

The next challenge, he adds, will be making more affordable photovoltaics and fuel cells. Fuel cells, which use stored oxygen and hydrogen to make electricity, are pricey in part because they depend on a plati¬num catalyst. Nocera hopes he can replace it with a version of his. That’s just one more way his material could help cata¬lyze a revolution in renewable energy. –B.H.

Harry Atwater: Reinventing Photovoltaics

When Harry Atwater was a student in Pennsylvania during the oil shocks of the 1970s, his elementary school had to close for weeks at a time during the winter because of a fuel shortage.
“That made a powerful impression,” says Atwater, now the director of the center for sustainable energy research at the California Institute of Technology, where he has devoted his career to finding a more reliable source of energy. Long an evangelist for photovoltaic solar cells and next-generation thin-film PV materials, Atwater has spent the past few years testing a technology that could reinvent photovoltaics altogether. Instead of cutting silicon into thinner and thinner wafers, as many scientists are doing, Atwater is researching ways to make arrays of silicon nanorods, small clusters of wires a hundredth the size of a human hair, convert sunlight into electricity.

Because the wires, bunched together like bristles on a brush, can absorb light along the entire length of each wire—while also “trapping” the sunlight on the semiconductor—a pack of nano¬rods is much more efficient than a conventional, flat wafer, even though it requires much less silicon. In recent tests, Atwater has found that the wires concentrate light at an intensity five to 10 times greater than traditional solar panels. “It’s one of those things that’s so obvious in retrospect, but it works unexpectedly well,” he says.
Atwater may not be able to get schools through the winter yet. But he’s getting closer. –J.E.