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."

(Shanghai Daily June 30, 2009)