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The Three Gorges Project

In Hong Kong, we do not have a giant waterfall or a large river that provides us with a powerful flow of water to generate electricity. However, on China's largest river the Yangtze River, we can find the world's largest hydroelectric project ever built, the Three Gorges Project.

Fig. 4   In a hydroelectric power plant, water from the reservoir is controlled to flow through the dam to turn the turbine generator.

The dam site of the project is situated on part of the Yangtze River in Sandouping, Yichang City, Hubei Province. The dam is about 2,309 m long and 185 m tall at its highest point [1]. When the project is finished, a reservoir will be formed with a normal water level 175 m higher than the water level on the other side of the dam [2]. The water from the reservoir is controlled to flow through the dam so as to turn the turbine generator units installed behind the dam to generate electricity. On completion, there will be 26 sets of turbine generator units of 700 MW power output each. This will provide a total of 18,200 MW of electricity generating capacity [2]. By comparison, the CLP Power's Castle Peak Power Station in Hong Kong has a generating capacity of 4,110 MW [3].

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To understand the operation of a hydroelectric power plant, click on the animation below.

Flash animation: Hydroelectric power plant

Hydroelectric generation does not consume any fuel or produce air pollution or greenhouse gas emission. It is a source of renewable energy. The electricity produced by the Three Gorges Project could save the burning of huge amounts of coal and help improve the air quality in China. Hydroelectric power, however, also has drawbacks. The building of dams is very expensive and dams may disrupt the natural flow of water. This disturbs the ecology and blocks the movement of fish and other organisms. The reservoirs often flood large areas of land, destroying the habitat. Heavy metal like mercury and other contaminants may accumulate in the reservoir, causing environmental problems. Although hydroelectric generation is considered a source of renewable energy, large-scale hydroelectric projects may not be sustainable in the long run because of their impact on the environment [4]. For large-scale projects like the Three Gorges project, there is also the need to resettle large populations to make room for the dam and the reservoir.

Do you want to make a model of a hydroelectric turbine generator that can actually produce electricity? The activity below will show you how.

Activity: Hydroelectric turbine generator model