SHANGHAI is rich in clean green wind power and the city is constructing more and more windmills as part of a sustainable energy plan. Zhang Qian flips the switch. The sails of hundred-meter-high windmills rotate in the wind in the mudflats of suburban Shanghai. Row upon row of turbines with huge vanes are generating new clean electricity.

Shanghai is rich in sustainable wind resources and is increasing its wind energy capacity as part of an overall plan to reduce pollution and develop clean energy.

But wind generates only a tiny fraction of the city's electricity. It cannot be stored and winds can be unpredictable, making reliance on wind unrealistic.

Still, wind is part of the green power mix.

By 2010, Shanghai plans to set up wind power plants with total capacity of 200,000 to 300,000 kilowatts - around 2 percent of installed capacity, according to Shanghai government's "11th Five-year Plan (2006-2010)" on wind power. By 2020, it aims for 1 million kw, or around 5 percent of installed capacity.

Since 2003 several wind power installations have been set up in suburban Shanghai in Fengxian, Nanhui and Chongming.

A major wind power installation is under construction near Donghai Bridge, connecting Nanhui area and Yangshan in Zhejiang Province. With a capacity of 100,000kw, it is the first on-sea installation in China, according to Xinmin Evening News.

Siemens AG began construction of a wind turbine manufacturing plant in Lingang New City, Pudong New Area, in early June.

Three development zones in Minhang District signed contracts with 11 new wind energy-related companies on June 22. The three zones - Zizhu Science Park, Pujiang High-tech Park of Caohejing Development Zone and Xinzhuang Industrial Park - will all be used for new sustainable energy development, including wind.

China is developing sustainable and clean energy sources including wind, solar, geothermal, ocean wave and biomass.

China's 11th Five-year Plan sets the goal of renewable energy consumption at 10 percent of total energy consumption by 2010.

Wind power, with zero emissions, low cost and solid technology, is one of the most popular renewable energy sources worldwide. The worldwide wind-energy capacity was 12.1 million kw in 2008, including 2.7 million kw added in 2008 alone, according to Wang Jing, deputy general manager of the Shanghai Electric Xantrex Power Electronics Co.

In 2008, China had the world's fourth largest installed capacity of wind power.

Wind power has many advantages. Generating geothermal energy requires special geological features like volcanos and hot springs. The drawbacks of nuclear power and dangerous spent fuel are well known.

Solar power, though sustainable and clean, still costs a lot to install on a large scale compared with wind power, says Wang. The initial cost for installing wind power dropped to 2 US cents/kwh in 2007 in the US. The comparable cost for solar power was 50 US cents/kwh in 2008, he says.

Though hydroelectric power is the most widely used renewable energy source, shrinking water resources, especially in China, mean other sources are necessary.

"As long as there are big, steady winds and large depopulated areas, wind power fields and plants can be installed," says Wang.

The Inner Mongolia Autonomous Region, Xinjiang Uygur Autonomous Region, Liaoning Province, Tibet Autonomous Region and coastal areas are all suitable for wind power.

There are around 25 wind power installations in China so far, most of them in coastal regions, Liaoning Province and eastern Inner Mongolia. There is not much in Tibet and Xinjiang due to the limited electricity grids there.

Shanghai is rich in wind, with estimated potential wind energy of around 4.7 million kw a year. The wind at 50 meters high averages almost 6.7 meters/second and there are around 7,300 hours of effective wind a year.

The Yangtze River mudflats are an ideal location for wind power installations, says Hu Chuanyu, senior engineer of the Shanghai Wind Turbine Co. He was involved in wind power programs in Chongming and Nanhui.

By 2015, around 500 square kilometers of mudflats will be used for wind power installations, says Hu. That would mean 3 million kw installed capacity (counting one, 6,000kw windmill per kilometer), says Hu.

Wind resources are even richer at sea areas, yet higher technology is required to build and maintain them.

Shanghai's first wind power installation went up in 2003 near Hangzhou Bay in Fengxian District. It was comprised of four, 70-meter-high windmills with 26-meter-long vanes. Each has a capacity of 850kw.

In 2005, the city built 14 windmills of 1,500kw capacity each in Chongming and Nanhui (three in Chongming and 11 in Nanhui).

In 2007, 10 windmills of 1,500kw capacity each were built in Chongming and in 2008, 11 similar windmills were constructed in Fengxian District.

All the electricity generated by wind is sent directly to the major power grid.

Chongming Island (County) is an ideal site, says Xu Bin, chief of the Social Development Section of the Chongming Development and Reform Commission.

The island currently has 13 windmills that provide 43 million kwh annually, thus supplying the residential electricity needs of 84,000 people. This saves around 14,200 tons of coal, eliminating 40,000 tons of carbon dioxide emissions.

The only problem with wind is that even in coastal areas it can be unpredictable.

"Wind comes and goes as it likes. You cannot ask it to stay or leave according to your needs," says Wang, of the Shanghai Electric Xantrex Power Electronics Co.

It's technically difficult to store wind energy, so it must be used as it's generated, he says, as surges and drops in energy can damage the electricity grid.

Therefore, wind power represents only a small proportion of the city's total power supply.

Though maintenance and operating costs are low for wind power, the air pollution problem means higher maintenance costs.

"It is ironic that when we shift to clean energy," says Wang, "we are still burdened by old pollution."