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Operations at the Three Gorges Dam

September 28, 2012

When construction began, it was believed that the dam would provide up to 10% of China’s demand for electricity.

Fully operational this year, the dam is actually providing less than 2% of China’s electricity.

The completed dam is shown here, from upstream and downstream sides of the dam. The red crane structures on the dam are for opening the sluice gates. The ship-lift that is still under construction is in the foreground of the second picture.

There are 14, 700 MW generators in the north section of the dam (closest turbine hall mostly blocked by ship-lift), 12 in the south section and an additional 6 located at the extreme south section of the dam (on other side of river in turbine hall in front of dam proper). The total installed generating capacity is 22,500 MW, including two 50 MW units used for local power.

Three Gorges Dam from upstream side. Photo by Dears

 

Three Gorges Dam from downstream side. Photo by Dears

The difference between the 10% estimate and the less than 2% realized, has been caused by the rapid growth of the Chinese economy, and possibly to a misjudgment of the capacity factor during the planning stages. The capacity factor has turned out to be 53%, while 73% may have been used when planning the dam.

Bryan Leyland from New Zealand, an expert on hydropower who recently returned from Mongolia working on a hydropower scheme, says that the 53% is entirely reasonable for the Three Gorges Dam, and that there is no “correct” worldwide figure for capacity factor. If an error was made in estimating capacity factor during the planning stage, it would seem to have been an entirely reasonable misestimate.

The reservoir level is maintained at 145 meters during the spring and summer when there is the potential for flooding, and 175 meters during the winter.

This picture shows how signs along the river mark water levels. Some show levels ranging from 130 to 175 meters marked as in a vertical ruler along the bank.

 

Water level sign on Yangtze River.

The dam is constructed with sluice gates that allow silt to flow through and prevent a build-up of silt along the base of the upstream side of the dam.

The dam is built on granite and relies on the weight of the dam to hold it in place against the water pressure of the river.

This is different from the Hoover Dam where the force of water pressure is transmitted to the canyon walls by the curved, convex (upstream) shape of the dam.

The first of the five stages of locks is shown in the first picture. (Left downstream lock is open, but empty.) The second picture with six craft in one lock (the four, plus the Viking Emerald, and another alongside the Viking Emerald, which isn’t shown).

It requires three to four hours to transit the five locks.

 

First of five locks at Three Gorges Dam. Photo by Dears

 

Boats loaded into first lock. Photo by Dears

The Three Gorges Dam has been a success, both in flood control and power generation. Without the Three Gorges Dam, it would be necessary to build 18, large 800 MW coal-fired power plants to provide the electricity being provided by the Three Gorges Dam.

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