NPR's Richard Harris examined a question posed by Eric Toone, a chemist at Duke University: How can we take solar photons and convert that into a liquid fuel at higher efficiencies than we can using plants?
One answer is to create liquid fuel using the not-so-rare element Cerium, chemically similar to rare earth metals, but much more abundant (about as much so as copper.) At 3,000 degrees Cerium can turn carbon dioxide and water into energy-rich fuels, and it can be reused!
Of course, using an energy-guzzling furnace to do this is like using alchemy to turn platinum into gold. Why bother?
But what if you can use a furnace that doesn't guzzle energy?
Earlier this year, Sossina Haile, a professor of materials science and chemical engineering at Caltech, got together with some colleagues in Switzerland and figured out how to put cerium inside a device that can generate those tremendous temperatures by concentrating solar energy.Toone, even though he directs an ARPA-E program supporting research on ideas that incorporate biology to do what Haile is trying to do with straight chemistry and engineering, is refreshingly nonparochial about Haile's approach:
And they did it — they were able to make synthetic fuel from just water and carbon dioxide. As they report in the journal Science, the system wasn't very efficient — less than 1 percent of the solar energy got converted into fuel. But there is hope."If we had a perfect reactor," Haile says, "we should easily get 10 percent efficient.""We went through the big numbers and said, 'Would this make any dent on U.S. energy production?' And the answer is yes," she says.
"The ultimate goal is the same, right? ...Green plants typically convert far less than 1 percent of sunlight into fuel. "So the name of the game is to say, 'Well, can we do better than that?'To find out, ARPA-E has pumped research dollars into more than a dozen universities and small companies across the country. Most projects are just getting under way, and Toone... is full of optimism."This is absolutely a solvable problem... I suspect we are 10 to 15 years away from actual fuels that you can buy at a pump and put into your vehicle," he says. "But I do very, very, very strongly believe that this is going to happen."Haile doesn't say her approach is the best, but it is an example of something that could pan out: "I personally view that the challenges that remain are very surmountable."