Hydroelectricity

Hydroelectric power is the simplest, most direct way to produce electricity. A dam is built, and water is released to turn large generators. No heat, no complicated equipment, no fuel transport, and no pollution. The power is available in control­lable amounts any time. This is an ideal situation that no other source can emulate. Of course, it is not available everywhere. Worldwide, hydro accounted for only 2.2% of total energy consumption in 2006, compared with 6.2% for nuclear.85 Some countries, such as Bhutan, depend entirely on hydroelectricity, and Bhutan actually exports part of it. Iceland uses hydro for 73% of its energy. The role of hydro in various parts of the world is shown by the blue bars in Fig. 3.62. In the USA, hydro accounts for 7% of electricity generated and 36% of all electricity from renewable sources.86 Renewables provided 7% of all energy consumed in the USA in 2007. China has the most hydro power. The Three Gorges Dam, completed in 2008, has generating capacity for 26.7 GW of electricity. This is comparable to the output of 25 coal plants.

Construction of dams can change the landscape and displace wildlife, espe­cially fish, but this is a small price to pay for free energy. Dam breaks pose a danger to downstream residents. Climate change can affect the distribution of rain and snow, causing some rivers to increase, and some to decrease their flow rates.

However, these drawbacks are minor, and hydroelectricity will continue to be an important part of our energy mix even if most of the best hydro sources are already being used.