Turning sunlight into hydrogen

A novel design might be the next big breakthrough in the pursuit of hydrogen from clean sources.

University of Delaware doctoral student Erik Koepf’s self-sustaining solar reactor uses mirrors to concentrate sunlight – enough to reach a sizzling 3,000 degrees Fahrenheit.

“This is probably the most complex device built by a graduate student in the history of our department,” Ajay Prasad, one of Erik’s advisors, says in a university statement.

The cylindrical reactor, about 2 feet by 3 feet, weighs 1,750 pounds and contains layers of insulation and ceramic materials.

When heated, hoppers feed the reactant, zinc oxide powder, into the system where it is transformed to pure zinc vapor. The zinc vapor is then reacted with water to form solar hydrogen. Cooling blocks are strategically placed within the reactor to keep motors, a quartz window and the aperture ring at suitable temperatures.

The new solar reactor is undergoing testing now at the Swiss Federal Institute of Technology in Zurich. “Essentially, we take zinc oxide powder and thermochemically store the energy of the sun in it, then bottle it up,” explains Koepf, who won the Laird Fellowship Award because of his passion for environmental awareness, education and outreach. The $22,000 award is given annually to an up-and-coming graduate student in engineering to encourage broad intellectual pursuits.

The next step is finding out whether this new design is reliable and efficient. With successful test results, the prototype could be scaled up to produce hydrogen for fuel at an industrial level. The model has not been tested outside of the lab until now, so no one knows just how much fuel it will produce.

Hydrogen, the simplest and most abundant element on earth, is nontoxic. If we can use it to operate vehicles, we can reduce our carbon footprint as well as our dependence on oil.

Since it does not exist naturally in its molecular form, it must be produced from other sources, typically fossil fuels. 

Production is rather expensive and usually involves undesirable emissions like carbon dioxide. That’s why Erik Koepf’s design could be so important. It does not produce those unwanted emissions, and the zinc oxide can be reused.

If the new solar reactor is successful in testing, Prasad says, “we can imagine a huge array of mirrors out in the desert concentrating sunlight up into a large central tower containing a larger version of Erik’s reactor and making hydrogen on an industrial scale.”

Vehicle manufacturers will surely follow Koepf’s research. Other new breakthroughs in fuel cell technology for cars are already pointing to ways of bringing down the cost of manufacturing, but the system needs to be optimized before hydrogen powered cars will be affordable to the general public.

In 2010, the Hawaii Hydrogen Initiative was launched with the goal of developing a hydrogen infrastructure in the state. Hydrogen can also be used to power airplanes and boats, and the U.S. military has had investments in hydrogen power for years. Work continues on the challenges of hydrogen fuel storage.

* Leah Jones, EarthTechling