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Hydropower Generation Basics

The process of generating electrical power involves converting one form of energy to another. Energy can never be created or destroyed but it can change form. Hydroelectric power production converts moving water into electrical power. Kinetic, or moving energy, is created by water in motion such as a waterfall or river. The amount of kinetic energy created depends on the speed of the moving water which varies depending on factors such as streamflow and change in elevation (head).

To generate hydroelectricity, water from a river or reservoir is directed into a large pipe called a penstock. Water flows from the penstock through the turbine, causing the turbine to rotate at a fast speed. The turbine is connected to a rotor by a shaft so the rotor rotates at the same speed as the turbine. The outside edge of the rotor is comprised of very strong electromagnets connected in a way to provide alternating polarity around the rotor. 

Another generator component is called a stator. The stator encompasses the rotor, is made of steel with many coils of small copper wire inside, and is placed close to the rotor. The energy produced by the water pressure turning the turbine and rotor, combined with the strong electromagnets, creates voltage across the stator coils which are connected in patterns that allow the voltage to be controlled. By changing the strength of the magnets on the rotor and the amount of the water flowing in the penstock, the amount of electricity being generated can be regulated.

Once generated, the electricity is conveyed to transformers via large copper bars called buses, where it is converted to a very high voltage for long-distance transmission to power customers.

drawing: hydroelectric power generation process
Above:  Hydroelectric power generation process
Right:  Water flow through penstock, scroll case, turbine, and draft tube
drawing: water flow throug penstock, scroll case, turbine, and draft tube


Last updated: December 1, 2008