Via FuturePundit, CalTech chemist Harry Gray pours some cold water on the notion that electricity from solar photovoltaic cells will be competitive with fossil fuels in the immediate future:

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.

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."

Of course, a carbon tax or cap-and-trade scheme would enhance solar's competitiveness, and there have been some promising advances lately in developing solar panels that use less silicon, which has become dramatically more expensive in recent years. Gray also sounds relatively optimistic about the possibility of using sunlight to split water, producing hydrogen for use in fuel cells. That prospect is often described as the "holy grail" of clean energy, but it's a ways off.

--Josh Patashnik