It may take at least 10 years of intensive research and development to reduce the cost of solar energy to levels competitive with petroleum, an expert warned today.

"Solar can potentially provide all the electricity and fuel we need to power the planet," Professor Harry Gray told the 235th national meeting of the American Chemical Society (ACS) in New Orleans.

He added: "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."

The professor 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, he said, was reducing costs so that a large-scale shift away from coal, natural gas and other non-renewable sources of electricity made economic sense.

Major challenges included developing cheap solar cells that worked without deterioration and reducing the amounts of toxic materials used in the manufacture of these cells.

Professor Gray is the Arnold O Beckman Professor of Chemistry and founding director of the Beckman Institute at the California Institute of Technology, and is seeking ways of transforming the industrialised world from one powered by fossil fuels to one powered by sunlight.