US lab's solar reactor extracts fuel from water or CO2

A California research team has come up with a promising technology using solar power to extract fuel from water and carbon dioxide

ABC Radio's The Science Show has reported what could prove a valuable source of non-fossil fuels under investigation at the California Institute of Technology (Caltech).

Following up on an honourable mention in President Obama's State of the Union speech in January, The Science Show reports that a Caltech team has found promising results in the use of concentrated solar radiation to power a reactor capable of extracting the fuels from atmospheric water or CO2. Subjected to temperatures of 1500-1600 degrees C in the presence of a catalyst like cerium dioxide, water and CO2 release their oxygen into the atmosphere. In subsequent cooling, they take oxygen back in again by effectively stealing the oxygen atoms from atmospheric water or CO2. What's left behind is hydrogen, methane or syngas, a mix of hydrogen and car games bon monoxide. Any of these can be condensed into liquid fuels.

Sossina Haile, a professor of material science and chemical engineering at Caltech, began testing the reactor using heat from non-solar sources with her colleagues at their lab in Pasadena. When they were confident the reactor worked, they took it over to Zurich to hitch it up to the Paul Scherrer Institute's solar concentrator. The trial runs work 'fantastically', she told Science Show host Robyn Williams.

Building on all this promise is that none of the constituent materials is hard to come by. Haile said cerium is 'about as abundant as copper' (as Williams mentioned, cerium dioxide is used as an oxidation catalyst in self-cleaning ovens). That means there's little to hinder the manufacture of reactors. And because the energy source it produces is storable, it's possible to integrate it into a continuous supply matrix. So it surmounts one of the great bugbears of direct solar power -- the drop in supply potential when the sun's not around.

With the fundamentals in place, the next step is to start working on boosting the efficiency of the reactors. "I think that if we built better reactors we could easily get to 10 per cent, 20 per cent efficiency for converting solar energy into chemical fuels," Haile told Williams. "The other aspect where one could invest is to develop even better materials than this cerium dioxide."

To those ends, Caltech is pitching for a share of the US$122 million funding allocated to the advancement of solar technologies. "Whenever you invest in materials, exploration, development, discovery, there is no guarantee that there's going to be an answer," she said. The available funds amount to 'a drop in the bucket' of what's needed. "In my laboratory of course, if we put some portion of that to advance what we're doing specifically here it would make a tremendous difference."

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