OSLO, Sept 20 (Reuters) - Wind power could generate almost 30 percent of the world's electricity by 2030 and is growing faster than any other clean energy source, a wind business group and environmental lobby Greenpeace said on Wednesday.

"At good locations wind can compete with the cost of both coal and gas-fired power," the Global Wind Energy Council (GWEC) and Greenpeace said in the study.

The two said that wind, which now accounts for 0.8 percent of the world's electricity supply, was expanding faster than other renewable energies such as solar, geothermal or tidal power in a shift from fossil fuels.

"Wind energy could provide as much as 29 percent of the world's electricity needs by 2030, given the political will to promote its large scale development paired with far-reaching energy efficiency measures," the report said.

GWEC says it represents more than 1,500 companies and other groups in more than 50 nations. Corporate members include General Electric <GE.N>, Shell, Vestas <VWS.CO> and Siemens <SIEGn.DE>.

Many countries are seeking non-polluting energy sources because of high oil prices and concerns about global warming, widely blamed on burning fossil fuels in power plants, factories and cars.

The report, to be released at a conference in Adelaide, Australia, said that wind was the most attractive alternative energy since it was free and available in all nations. Solar power is a non-starter in the Arctic in winter, for instance.

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Nations now generating most wind power are Germany, Spain, the United States, India and Denmark, it said.

The 60-page "Global Wind Energy Outlook 2006" said the problem that the wind does not always blow could be overcome by choosing good sites and using back-up sources of power.

And it said that turbines' benefits in cutting pollution far outweighed any damaging environmental impact. Some people denounce the turbines as eyesores, for instance.

While the report said that wind could make up 29 percent of electricity by 2030 assuming favourable government policies, the report projected two other scenarios with wind expanding to 5 or 16 percent of electricity demand by 2030.

All the projections are far more optimistic than a forecast that wind will account for 3.5 percent of electricity by 2030 made by the International Energy Agency, which advises rich nations.

Greenpeace issued another report with the main solar industry group earlier this month which projected that solar power could rise to generate 2.5 percent of the world's electricity by 2025.

The wind report said that modern turbines, whose rotors can be 100 metres in diameter, generated 180 times more electricity for half the cost of turbines built 20 years ago.

The report urged governments to set targets for wind energy, to phase out subsidies for fossil fuels or nuclear power and step up the fight against climate change.