With nonrenewable energy sources such as fossil fuels being quickly depleted as humans require more energy in the daily lives of modern society, renewable energy sources are becoming increasingly popular. For example, many energy sources such as wind power, solar power, and water power are being used throughout the world. Among these, hydroelectricity, the harnessing of energy from moving water and one form of renewable energy, is an efficient, economical, and nonpolluting alternative to fossil fuels with the potential to provide a larger percentage of world energy in the future.
Hydroelectric energy is generated from moving water and is currently the largest source of renewable energy in the world. (Union of Concerned Scientists, 2005) As shown in Figure 1, small and large hydroelectric energy together constituted over 63% of all renewable energy used worldwide in 2005. Small hydroelectric plants usually encompass plants that generate up to 10 megawatts of power, while large hydroelectric plants can generate thousands of megawatts. (Global Status Report, 2006)
Figure 1: Hydroelectricity compared to Other Renewable Energy Sources
Since the Greeks used water wheels over two thousand years ago, humans have been using movement of water to create energy. (U.S. Department of Energy, 2005) The development of the water turbine began with French engineer Bernard Forest de B�lidor in the 1700?s, and the first hydroelectric power plant in the world was built in Wisconsin in 1882. (U.S. Department of Energy, 2005) This power plant was based on a combination of a water turbine and an electric generator. (U.S. Department of Energy, 2005) Hydroelectric power now constitutes approximately 20% of all energy in the world, with a capacity of 776 GW. (Union of Concerned Scientists, 2005)
The process of generating hydroelectricity has evolved tremendously over the last century with the advance of technology. Hydropower is most commonly created through the use of moving water, in combination with manmade parts such as a dam, turbine, generator, and transformer, which can be seen in Figure 2. Most hydropower plants use a dam to create a large reservoir of water. The water is led down through a pipe called a penstock toward the turbine. The force of the moving water turns the blades of the turbine, which is connected to a generator. As the turbine?s blades turn, magnets inside the generator also rotate, creating alternating current. A transformer turns the AC into higher voltage electricity, which exits through power lines, while the used water exits back into the river. The amount of energy generated depends on the volume of the water and the height difference between the intake and the outflow. (Bonsor, 2007)