Powering Up with Manmade Leaves

 

A DEPARTMENT OF ENERGY-FUNDED initiative seeks to mimic the photosynthesis process in leaves to convert solar energy directly into fuel.

U.S. Deputy Secretary of Energy Daniel Poneman noted what was at stake with this program. "Finding a cost-effective way to produce fuels as plants do, combining sunlight, water and carbon dioxide, would be a game changer, reducing our dependence on oil and enhancing energy security," he said when funding for this work was announced last year.

What makes solar-to-fuel conversion so enticing is fuel's capacity to store energy. "Fuel has a high energy density," said Nate Lewis, a chemistry professor at the California Institute of Technology, and the person heading up the DOE research into artificial photosynthesis. In particular, he noted that compared with storing energy in batteries, compressed air, or by pumping water, fuels offer a much higher energy density capacity.

Solar-to-fuel research has been under way for years. Past attempts have produced prototypes that were either too costly, did not last, were not efficient, or a combination of all three.

Simply put, the technology challenges for success are enormous. Solar-to-fuel research was identified by the Energy Department's Basic Energy Sciences Advisory Committee as an area in which "transformational science breakthroughs are urgently needed."

In particular, past efforts tried to take the sun's energy, and using a catalyst, split water and carbon dioxide to produce fuels. In most cases, the catalyst was based on extremely expensive or rare materials. Additionally, the conversion process can be highly corrosive. As a result, most solutions quickly degrade, thus limiting the amount of energy that could potentially be produced by a device.

The work Lewis and his colleagues are doing is in one of three areas the DOE has focused on through its relatively new Energy Innovation Hubs approach.

The hubs are designed to be multidisciplinary, multi-investigator, multi-institutional integrated research centers. In addition to the solar-to-fuel hub, the other hubs will focus on improving the energy efficiency of buildings and modeling and simulation for nuclear reactors.

The solar-to-fuel hub was announced in July. The DOE committed $122 million over five years to the research.

The work will be carried out by the newly formed Joint Center for Artificial Photosynthesis. The center brings together researchers from six universities and two government labs. Lewis serves as the principal investigator. The center is led by the California Institute of Technology in partnership with the U.S. Department of Energy's Lawrence Berkeley National Laboratory.

Over the next five years, the center's activities will include research into light absorbers, catalysts, membranes, and other elements of the total system. Longer-term, the goal is to move from the discovery phase to commercialization, to improve process efficiencies, and to produce a variety of fuels using the manmade leaf approach.