Hydropower is basically flowing water that creates energy, which is captured and turned into electricity. The most common type of hydropower plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, and activating a generator that produces electricity (see figure). But, surprisingly, only 2 percent of the dams in the U.S. produce electricity. According to the DOE, by adding hydroelectric projects to those dams where it is financially and environmentally feasible, the U.S. could increase its hydropower capacity by 17,000 MW.
The National Hydropower Association (NHA) estimates that today’s hydropower turbines can convert more than 90% of available energy into electricity, making them more efficient than any other form of generation.
When the price of oil skyrocketed in the 1970s, so did interest in wind turbine generators. Wind turbine technology development in the 1980s introduced new ways of converting wind energy into power. These technologies were used to build “wind farms” or wind power plants — groups of turbines that feed electricity into the utility grid.
Wind turbines capture the wind’s energy with two or three propeller-like blades, which are mounted on a rotor, to generate electricity. The turbines sit on towers, taking advantage of the stronger and less turbulent wind at 100 feet or more above ground. Wind turbines can be used as standalone systems, or they can be connected to a utility power grid. Standalone turbines typically are used for water pumping, but farmers in windy areas also use them to generate electricity. Wind farms are used as utility-scale sources of wind energy.
Wind energy continues to be one of the world’s fastest-growing energy technologies. In 2005, the U.S. wind energy industry installed more than 2,300 megawatts of new wind energy capacity — or more than $3 billion worth of new generating equipment — in 22 states.
The United States has many areas with abundant winds, particularly in California, the Midwest, and the Great Plains. Researchers estimate that 50% of the U.S. has enough wind resources for small turbine development, and 60% of U.S. homes are located in those wind resource areas. Areas with good wind resources have the potential to supply up to 20% of the electricity consumption of the U.S.