China’s Three Gorges Project (TGP) on the Yangtze river will be the world’s largest hydro-electric plant when it is finally completed in 2009 after work started in 1993.
Already, 10 of the planned twenty-six 700 megawatt (MW) generators have been installed, with a possible further six generators under consideration. A generator is installed roughly every three months.
To put this into context, South Africa’s Eskom has a maximum net installed capacity of 36 208 MW spread over 24 power stations.
The initial planned TGP power output is therefore equal to half Eskom’s capacity and the further 4 200 MW will take it to 62% of Eskom’s capacity.
The electricity is distributed to Central China and Chongqing via 500 kilovolt (kV) alternating-current transmission lines and to East China via 500 kV direct-current lines.
A lack of electricity has been a major constraint on China’s growth and in July and August, when domestic demand for air-conditioning peaked with temperatures above 35 degrees Celsius, many factories in Beijing and Shanghai had to lose one week’s production out of every four.
In early September, the easing in temperatures allowed factories to resume their normal 11-hours, six-days-a-week shift routine.
The dam wall is a straight 2 300m across the river at Sandouping, with a crest elevation of 185m and a maximum water height of 181m.
The dam is split into three sections with a central 483m-long spillway with a left (if looking downstream) powerhouse section of 643m and a right powerhouse section of 584m.
The lake that forms upstream of the dam will be more river-like than Kariba-like and will extend for 600km with an equilibrium width of only 1,3km. It will nevertheless contain 39-billion cubic metres of water.
Intense study has been made of the possible “reservoir-induced earthquake” scenario and the conclusion is that due to the narrowness of the lake, no risk is attached to this scenario.
Apart from the electricity generated, the TGP has two other main benefits. The first is flood control with the TGP protecting the central Chinese city of Wuhan from everything but a one-in-1 000-year flood. Before the TGP, the Gezhouba Project, 40km downstream, provided one-in-10-year flood protection.
The second is raising the carrying capacity of the Yangtze river from the current 10-million tons to 50-million tons, as 10 000-ton barges can now go all the way to Chonqing, 660km upstream from Yichang, where trans-shipment to smaller barges previously had to take place.
As Chonqing has a population of 30-million, this opens up a very important market for South African products, which have previously been largely confined to the coastal cities such as Shanghai and Hong Kong. — I-Net Bridge