Major Technological Challenges Must Be Overcome to Make Solar Energy Competitive

Despite oil prices that hover around $100 a barrel, it may take at least 10 or more years of intensive research and development to reduce the cost of solar energy to levels competitive with petroleum, according to an authority on the topic.

“Solar can potentially provide all the electricity and fuel we need to power the planet,” Harry Gray, Ph.D., scheduled to speak here today at the 235th national meeting of the American Chemical Society (ACS). His presentation, “Powering the Planet with Solar Energy,” is part of a special symposium arranged by Bruce Bursten, Ph.D., president of the ACS, the world’s largest scientific society celebrating the 10th anniversary of the Beckman Scholars Program.

“The Holy Grail of solar research is to use sunlight efficiently and directly to “split” water into its elemental constituents – hydrogen and oxygen – and then use the hydrogen as a clean fuel,” Gray said.

Gray is the Arnold O. Beckman Professor of Chemistry and Founding Director of the Beckman Institute at the California Institute of Technology. He is the principal investigator in an NSF funded Phase I Chemical Bonding Center (CBC) – a Caltech/MIT collaboration – and a principal investigator at the Caltech Center for Sustainable Energy Research (CCSER).

This research has the goal of transforming the industrialized world from one powered by fossil fuels to one powered by sunlight. The CBC research focuses on converting sunlight to chemical fuels while research in the CCSER focuses on generating electricity from sunlight and developing fuel cells.

In his talk at the ACS Presidential Symposium, Gray cited the vast potential of solar energy, noting that more energy from sunlight strikes the Earth in one hour than all of the energy consumed on the planet in one year.

The single biggest challenge, Gray said, is reducing costs so that a large-scale shift away from coal, natural gas and other non-renewable sources of electricity makes economic sense. Gray estimated the average cost of photovoltaic energy at 35 to 50 cents per kilowatt-hour. By comparison, other sources are considerably less expensive, with coal and natural gas hovering around 5-6 cents per kilowatt-hour.

Because of its other advantages – being clean and renewable, for instance – solar energy need not match the cost of conventional energy sources, Gray indicated. The breakthrough for solar energy probably will come when scientists reduce the costs of photovoltaic energy to about 10 cents per kilowatt-hour, he added. “Once it reaches that level, large numbers of consumers will start to buy in, driving the per-kilowatt price down even further. I believe we are at least ten years away from photovoltaics being competitive with more traditional forms of energy.”

Major challenges include developing cheap solar cells that work without deterioration and reducing the amounts of toxic materials used in the manufacture of these cells. But producing low cost photovoltaics is only a step in the right direction. Chemists also need to focus on the generation of clean fuels at costs that can compete with oil and coal.

Gray emphasized this point: “The pressure is on chemists to make hydrogen from something other than natural gas or coal. We’ve got to start making it from sunlight and water.”

Gray noted that the NSF CBC program currently includes Caltech and MIT, but would expand in a second phase to include several additional institutions.

A number of other presentations in the Presidential Sessions during the ACS meeting will focus on future sources of energy. Among them are:

• Alan Heeger, Ph.D., of the University of California, Santa Barbara, who shared the 2000 Nobel Prize in Chemistry for his work on conductive polymers, will give a progress report on the performance of “plastic” solar cells.
• Paul Alivisatos, Ph.D., of the University of California at Berkeley and co-editor of the ACS journal Nano Letters, will describe potential advantages of future solar cells using nanoscale materials, and address some of difficulties that need to be overcome.
• Raymond Orbach, Ph.D., a noted researcher in theoretical and experimental physics who directs the U. S. Department of Energy’s Office of Science. Topic: “Assuring a Secure Energy Future.”
• Nathan S. Lewis, George L. Argyros Professor Chemistry, Division of Chemistry and Chemical Engineering, California Institute of Technology. Topic: “Solar Energy Utilization.”
• James B. Roberto, Deputy Director for Science and Technology, Oak Ridge National Laboratory, Oak Ridge National Laboratory. Topic: “Advanced Nuclear Energy Systems.”
• Mildred S. Dresselhaus, Institute Professor of Physics & Electrical Engineering, Massachusetts Institute of Technology. Topic: “Hydrogen Economy.”
• Héctor D. Abruña, Emile M. Chamot Professor and Chair, Department of Chemistry and Chemical Biology, Cornell University. Topic: “Electrical Energy Storage.”
• Bruce C. Gates, Distinguished Professor, Department of Chemical Engineering and Materials Science, University of California-Davis. Topic: “Catalysis for Transportation Fuels.”