Environmental scientists from the U.S. and China estimate that wind power alone could meet China's projected electricity needs for 2030 using wind turbines installed over a combined area nearly the size of Manitoba.

The goal of the study is to determine the practicality of switching China from generating electricity using coal and other fossil fuels to a greener energy source, to reduce greenhouse gas emissions and pollution.

China has the second-largest national electricity generating capacity, next to the U.S., and is the world's leading emitter of carbon dioxide. The country's energy demands are projected to increase by 10 per cent a year.

The researchers at Harvard and Tsinghua University in Beijing used geographic data and weather patterns, as well as information about China's energy bidding rules and financial restrictions, to determine where wind turbines could be installed.

They assumed that a network of wind turbines, each producing 1.5 megawatts of power, could be installed in rural areas without forests or ice cover, with a slope of no more than 20 per cent.

They found that such a network running at 20 per cent capacity could produce 24.5 billion megawatt-hours of electricity every year, or more than seven times China's current energy production.

The wind farms would cover a combined area of 500,000 square kilometres, or nearly the size of Manitoba. However, the turbines themselves would have a small enough footprint that the areas could still be used for farming, the researchers said. China uses about 1.4 million square kilometres of land every year for growing crops.

Meeting China's demand over the next 20 years using coal-fired power plants would result in more pollution and more greenhouse gas emissions, a potential increase of 3.5 billion tonnes of carbon dioxide every year, the study estimated.

"The real question for the globe is: What alternatives does China have?" said Michael McElroy of Harvard's School of Engineering and Applied Sciences. The study is published in this week's issue of Science.

About 0.4 per cent of China's current electricity supply comes from wind energy. The plan outlined in the study would cost about $900 billion over 20 years at current prices, an amount the researchers considered reasonable given the size of the country's economy. They argue that some of that cost would go toward an expanded energy supply grid that China would need anyway, given its current growth in energy demand.

"China is bringing on several coal fire power plants a week. By publicizing the opportunity for a different way to go we will hope to have a positive influence," said McElroy.

China passed a renewable energy law in 2005 giving preferred tax status to alternative energy projects, including wind power.