Supply edges closer to urban demand

CHINA: China is ramping up efforts to deliver power from wind farms in the blustery north and west of the country to economic centres in eastern and central China through ultra-high-voltage (UHV) transmission lines.

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Chinese transmission firm State Grid has announced that it has mapped out a plan to send wind power from Jiuquan, in northwest China's Gansu province - host to the country's first of seven planned wind power complexes each exceeding 10GW - to power-thirsty Hunan province in the centre of the country, through 800kV UHV direct-current transmission lines.

Long-distance travel

China's need to send wind power over long distances results from the mismatch in remote areas of rich wind resource and low levels of economic development - and thus power consumption. Wind farms in northern and western China are 800-3,000 kilometres away from the country's economic hubs. China's existing power transmission lines - mainly 110kV, 220kV and 500kV - are unable to accommodate long-distance transmission of wind power from large wind farms.

Industry officials say the solution is a sophisticated grid of UHV lines for trans-regional connection. State Grid believes 1,000kV UHV alternating-current (AC) transmission lines may transmit electric power over 1,500 kilometres, and 800kV direct-current (DC) transmission lines may be able to send power 3,000 kilometres and further. The 1,000kV AC lines have a quarter of the resistance loss of 500kV lines, while 800kV lines, likewise, have a fraction of the losses of 500kV lines.

Also, 1,000kV UHV lines use only about half the land used by 500kV lines, and 800kV lines use about a quarter the land used by 500kV lines.

There has been talk of progress for years. But in late January, Jiang Zuobin, director of Hunan provincial development and reform, inspected wind farms in Jiuquan and soon afterwards pushed for inclusion of an 800kV UHV DC transmission line over the 2,000 kilometres from Jiuquan to Hunan, in China's 12th five-year plan (see page 35).

Soon after that, State Grid announced that it had found the project technologically viable and economically sound. All that is needed now is approval by the National Energy Bureau (NEB). Should the project go ahead, it will fill a hole in a jigsaw puzzle: Hunan is expected to import over half of its electricity by 2015 and Jiuquan has plans for 20GW of installed wind capacity by that year.

The stakes are high. Although China has grabbed the global lead in terms of installed wind capacity, the NEB acknowledges that at the end of 2010 about 26% of installed wind was not online.

"If it succeeds in this project of sending an immense amount of wind power through long distances, China will emancipate itself from the predicament of advancing with rapidly expanded wind installed capacity but lagging in grid construction - an enormous waste of installed wind capacity," says Zhou Fengqi, vice-president of China's National Energy Society.

Pilot lines

China put into operation a pilot 1,000kV UHV AC transmission line spanning the 654 kilometres between the south-east corner of Shanxi Province to Jinmen, Hubei Province, in late December 2008. It also carried out a pilot 800kV project stretching 1,907 kilometres from Xiangjiaba, south-west Sichuan Province, to east China's Shanghai, in July 2010. The two have run smoothly. Zhou concludes that 800kV transmission lines are best suited to wind.

Liu Zhenya, general manager of State Grid, has announced that his company will invest CNY 500 billion ($76 billion) in the next five years to construct a high-tech grid of long-distance UHV AC transmission lines. Three are to run north/south and three east/west. Also planned are 11 UHV DC transmission lines. State Grid plans to accommodate 100GW of wind power by 2015.

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