Caltech’s Solar Oven Bakes Up Fuel

The way they describe it, the technology developed by Sossina Haile and her colleagues at Caltech could practically have been done right at home. A self-cleaning oven, a magnifying glass and, voila, a breakthrough in converting carbon dioxide and water into fuels!

Of course, the actual work was rather more complicated, but the analogies are helpful in understanding how the solar reactor Haile’s team constructed strips oxygen from water and carbon dioxide and leaves hydrogen gas and carbon monoxide behind.

Caltech solar reactor, Sossina Haile

image via Caltech

To begin with, the reactor is lined with cerium oxide, aka ceria, which is commonly used in the walls of self-cleaning ovens because it helps catalyze reactions and is a boost to the cleaning process. The top of the reactor, meanwhile, has a quartz window and a cavity that absorbs concentrated sunlight (the magnifying glass, if you will). As the reactor is heated at extremely high temperatures, the ceria-lined reactor “exhales” oxygen, the researchers explained – and it does this while maintaining its crystal structure, a key quality that allows the reactor to “inhale” oxygen as it cools down.

Now imagine if carbon dioxide and/or water gas molecules were pumped into the reactor; this inhaling strips oxygen from the CO2 and H20, rendering CO and H2. And hydrogen gas, of course, can be used in fuel cells, or combined with carbon monoxide to make synthetic gases.

What about using the carbon dioxide emitted by vehicles to make fuel? Probably not viable, Haile said – but she did suggest that CO2 emissions from coal-powered electric plants could be converted to transportation fuels. Or, as Caltech put it: “The reactor could be used in a ‘zero CO2 emissions’ cycle: H2O and CO2 would be converted to methane (and) would fuel electricity-producing power plants that generate more CO2 and H2O, to keep the process going.”

Pete Danko is a writer and editor based in Portland, Oregon. His work has appeared in Breaking Energy, National Geographic's Energy Blog, The New York Times, San Francisco Chronicle and elsewhere.