Water turbines produce electricity from kinetic energy by using the force of falling water to stimulate an electric generator. There are two types of water turbines: impulse turbines and reaction turbines. According to the U.S. Geological Survey, water turbines are an effective method for supplying short bursts of energy during peak hours of power demand.
Water turbines work similar to fossil fuel power plants in that they utilize a turbine that rotates a metal shaft in an electric generator.
Water turbines are built at sources of running water with large drops in elevation. The placement of a dam stores water in a reservoir. An intake near the bottom of the dam wall guides water through a penstock to the turbine propeller. The moving water turns the propeller. Field poles, loops of wire wound around stacks of magnetic steel lamination, are mounted on the perimeter of the rotor. When water causes the rotor to spin at a fixed speed, the electromagnetic field poles move past the conductors. This causes electricity to flow and voltage to develop at the output terminals.
Impulse turbines use water velocity to move the runner. After hitting the runner, water flows out of the turbine housing. Reaction turbines utilize both pressure and moving water. Water does not strike every blade individually. Instead, it directly hits the runner. Reaction turbines are more popular than impulse turbines and are used in low- and medium-head applications.