Hydroelectric generators harness the power of water being forced through a dam to turn the blades of turbines, generating electricity. These plants work with gravity instead of steam as is the case with coal-fired power plants.
Hydroelectric power plants depend on natural drops in elevation occurring somewhere along the length of a broad, powerful river. This drop allows the falling water to be harnessed to turn the turbine, but they are next to impossible to create artificially. The dam attendant to the plant makes sure that there is an adequate reservoir behind the turbine so that the power plant can run reliably.
Some famous hydroelectric plants include:
- Russia, Sayano-Shushenskaya.
- The United States, the Hoover Dam.
- Egypt, the Aswan Dam.
Hydroelectric energy is very clean in terms of the air pollution produced by its operation, especially when compared to the pollutants produced by coal-fired power plants. Their reservoirs function like reserve batteries and their output in terms of electricity is much easier to scale to the needs of the moment, as demand for electricity varies broadly over the course of a 24-hour cycle. Some dams are even equipped to pump water back into their reservoirs during the "down" portion of these cycles, typically overnight when demand is low.