How Hydroelectric Power Works

http://wwwga.usgs.gov/edu/hyhowworks.html

Hydroelectric power can be defined as the generation of electricity by flowing water; potential energy from the weight of water falling through a vertical distance is converted to electrical energy. The amount of electric power P that can be generated is given by the equation below, where Q is the volume flow of water, h is the height through which the water falls, and k is a constant equal to 0.102 when Q is in cubic meters and h is in meters (SI units).

-McGraw-Hill Encyclopedia of Environmental Science & Engineering, 3 ed.,1993

 

P = Qh/k (kW units)

 

• Dam - Most hydropower plants rely on a dam that holds back water, creating a large reservoir .
• Intake - Gates on the dam open and gravity pulls the water through the penstock , a pipeline that leads to the turbine. Water builds up pressure as it flows through this pipe.
• Turbine - The water strikes and turns the large blades of a turbine, which is attached to a generator above it by way of a shaft. The most common type of turbine for hydropower plants is the Francis Turbine, which looks like a big disc with curved blades. A turbine can weigh as much as 172 tons and turn at a rate of 90 revolutions per minute (rpm), according to the Foundation for Water & Energy Education (FWEE)
• Generators - As the turbine blades turn, so do a series of magnets inside the generator. Giant magnets rotate past copper coils, producing alternating current (AC) by moving electrons.
• Transformer - The transformer inside the powerhouse takes the AC and converts it to higher-voltage current.
• Power lines - Out of every power plant come four wires: the three phases of power being produced simultaneously plus a neutral or ground common to all three.
• Outflow - Used water is carried through pipelines, called tailraces , and re-enters the river downstream.

*words and picture courtesy of:

http://people.howstuffworks.com/hydropower-plant1.htm



photo taken by Mr. Roy Schmidt; Minnesota Power, Hydropower Dam in Little Falls, MN