Diver originally designed the machine with the hydrogen economy in mind. The idea was to avoid the inefficiency of electrolysis and build instead a solar heat engine that could produce hydrogen and oxygen directly, cutting out electricity as the middleman. It’s an approach also being pursued by researchers in Japan, France, and Germany.
But the Sandia team soon realized that the same process could turn CO2 into carbon monoxide. Even if the hydrogen economy didn’t take off, they still had a way to make the fuels we depend on today in a way that limits the impact of burning coal and natural gas for electricity and other industrial processes.
Diver says the challenge now is to improve the efficiency of the system. If the Sandia team can demonstrate higher efficiency, “it could be a significant step forward,” said Vladimir Krstic, director of the Centre for Manufacturing of Advanced Ceramics and Nanomaterials at Queen’s University in Kingston, Ontario.
Scientists figure it will be 15 to 20 years before the technology is ready for market. In the meantime, the goal is to develop a new generation prototype every three years that shows an increase in solar-to-fuel conversion efficiency and a decrease in cost. Part of that will come from the development of new ceramic composites that release oxygen molecules at lower temperatures, allowing for more of the sun’s energy to be converted into hydrogen or carbon monoxide.
“Our short-term goal is to get this to a few percent efficiency,” says Miller. “It might seem like a low number, but we like to compare that to photosynthesis, which is actually a very inefficient way to use sunlight.”
He says the theoretical maximum efficiency for photosynthesis is around 5 percent, but in the real world it tends to fall to around 1 percent. “So we may be starting very low, but we’d like to keep it in the context of what we have to beat. Ultimately, we believe we have to get in the range of 10 percent sunlight-to-fuels, and we’re a long way from doing that.”