"By 2030 the cost will be comparable to electricity produced by a nuclear power plant," said Machida, speaking on the fringes of the IFA trade fair in Berlin, the world's biggest consumer electronics fair.

Asked how the costs were likely to compare with those for producing electricity from fossil fuels such as coal, Machida replied: "Fossil fuel resources will be totally out by then."

Solar electricity currently costs about US$0.50 per kilowatt hour to produce, more than eight times as much as that produced from fossil fuel.

The market is growing at a rate of more than 30 percent per year but solar power still produces just a small fraction of one percent of the world's energy.

The solar industry in general expects the cost of producing solar power to fall by about 5 percent per year, on average.

Machida said he expected that a shortage of solar-grade silicon, the raw material from which solar panels that harness the sun's energy are made, would ease by 2008 as silicon makers step up production to catch up with soaring demand.

"In the first half of 2007, supply capacity will be increased, so once we go into 2008, supply will be catching up," he said.

Sharp has also been moving towards producing more so-called thin-film solar panels, which use less silicon but are less efficient than traditional solar panels.

Machida said the cost to produce solar energy from thin film was still around one-and-a-half times as high as making it from the normal, multicrystalline type.

"The mainstream will still be multicrystalline," Machida said, but he added that demand for thin-film would also continue to increase, for example, for specialist varieties such as see-through panels for window glass.

Machida said the sun could send enough energy to Earth in as little as an hour to provide for all the world's energy needs for one year.