GLOBAL CHALLENGES

Converting the Sun's Energy in a Natural Way

Salvatore Salamone | Date: 03-31-11 | Comments

Research into artificial leaves is heating up. The goal is to produce a commercially viable solution that mimics the photosynthesis process in leaves to convert solar energy directly into fuel.

Hoping to duplicate the incredibly useful conversion of sunlight to energy in common tree leaves, MIT chemist Daniel Nocera has developed a prototype solar-powered device the size of a playing card that can break water down into hydrogen and oxygen.

According to Nature, this new "artificial leaf" combines a solar cell and the needed electrolysis equipment into one piece by chemically painting a catalyst onto a solar cell and immersing it in water.

Research into this area has been under way for years. Earlier efforts in the late 1990s proved the concept, but the materials required to make the conversion were much too expensive and in such short supply that commercial devices were not possible. Nocera's device uses abundant cheap materials.

Nocera's work is just the latest in much broader efforts to mimic the photosynthesis process in leaves to convert solar energy directly into fuel. What makes this solar-to-fuel conversion process of leaves so enticing is the 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 a U.S. Department of Energy (DOE) effort researching artificial photosynthesis.

Simply put, compared with storing energy in batteries, compressed air or by pumping water, fuels offer a much higher 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. To put the technical challenges into perspective, consider that in a report by the department's Basic Energy Sciences Advisory Committee, solar to fuel research was identified as an area where "transformational science breakthroughs are urgently needed."

To help overcome the technical obstacles, DOE work in this field will be carried out by the newly formed Joint Center for Artificial Photosynthesis. This entity will be led by Lewis' California Institute of Technology in partnership with the DOE's Lawrence Berkeley National Laboratory. The center brings together researchers from six universities and two government labs.

The goal of the group's efforts is to develop an integrated solar energy-to-chemical fuel conversion system and move this system from the discovery phase to a scale where it can be commercialized.

The center's activities will include research into light absorbers to be built from strong, photochemically stable, abundant elements; catalysts to drive the key fuel-producing reactions such as oxidation of water and reduction of carbon dioxide; and other elements of the total system.