Seriously: a cerium solar reactor turns sunlight into fuel

Solar energy has the potential provide all our power needs. But costs and technological challenges limits the economical utility of solar power. Perhaps the solution is to emulate those ubiquitous but often unnoticed solar energy collectors: plants. A team of researchers recently unveiled a device that, like plants, uses sunlight and a unique catalyst to convert carbon dioxide or water into fuel.

The sun is the ultimate source of energy on the planet. Fossil fuels, biomass, and even wind, derive their origin from sunlight. The earth directly absorbs 3,850,000 exajoules (EJ) of energy from the sun every year. Humans consume around 500 EJ of energy a year, with over 80% provided by fossil fuels. Only capturing a fraction of sunlight could reduce the world’s dependence on fossil fuels.

Yet, in spite of the huge potential, solar energy provides less than 1% of human energy needs. Solar devices require rare materials and are expensive. And a stand-alone solar energy system would have to store energy for the time when the sun doesn’t shine. With these drawbacks, solar panels are most often used as a complement to fossil fuels, not as a replacement.

An international team of researchers, led by Professor Sossina Haile of the California Institute of Technology, developed a solar device that addresses both the expense and the energy storage problems. The device concentrates sunlight to heat a cerium oxide catalyst that converts carbon dioxide to carbon monoxide (a precursor to synfuel) or water to hydrogen. According to Dr. Haile, cerium is nearly as abundant as copper, so cost or availability shouldn’t limit the manufacture of the device.

The prototype is still very inefficient – it converts less than 1% of the solar energy entering the reactor into fuel – but the researchers are confident that with better insulation and an improved collector design the efficiency could be boosted to nearly 20%. That high of an efficiency should make the device commercially viable.

Dr. Haile envisions rooftop reactors that make around three gallons of fuel a day. The idea of directly turning sunlight into fuel that can be used to heat homes and fuel cars seems to be the stuff of science fiction, but plants have been doing it for millions of years. It’s about time that we catch up.

Here’s to sunny New Year.