How Three Gorges Dam Powers Shanghai

In case you haven't noticed, China's quickly becoming an production powerhouse. And to power these industries, China requires a massive, steady supply of power. Like the 18,300MW generated by the Three Gorges Dam's massive turbines.

The Three Gorges Dam utilises 32 generator -- 30 700MW units and two 50MW -- known as Francis turbines. Named after James B. Francis, who invented the design in 1848, these turbines are reaction-types: water loses its pressure (and energy) as it moves through the turbine and drives the runner.

As high pressure water enters through the spiral casing surrounding the guide vanes, they direct the water flow towards the runner blades (shown above). These blades spin at 75 revolutions per minute, driving a vertical shaft attached to an immense electromagnetic generator. The generator's stator -- the stationary outer ring -- is more than 3m tall, 20m wide, and is the largest of its kind.

The main array of 700MW turbines each weigh approximately 6000 tons and pass between 595-963 cubic metres of water every second. These turbines achieve an average efficiency -- how much of the water's energy is converted into mechanical energy -- of nearly 95 per cent.

Currently, only 29 of the 32 generators are online, the remaining turbines are undergoing testing and are expected to be operational by the end of 2012. However, even without them, the Three Gorges Dam is the largest capacity hydroelectric generator on the planet by capacity -- a stunning 18,300MW. And, in the eight years, the dam has been even partially operational, it has produced over 500TWh of electricity. However, even though the dam was originally planned to produce 10 per cent of China's power, the country's hyper-expansion has already reduced that figure to to just three per cent of 2006 numbers. And falling.

[Power-Technology, Bright Hub, Francis Turbine Wiki, Three Gorges Dam Wiki]

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