Hydroelectrical Power Generation Traditional Methods of Hydroelectric Generation Low Head Power Generation Medium Head Power Generation High Head Power Generation Large Dams (Three Gorges, Itaipu) Environmental Effects of Large Dams

Energy in the News

Breast Shot Wheel Breast shot wheel: One type of traditional Water wheel Water wheels: source Of power for the Industrial revolution

Overshot Wheel More efficient that breast shot Wheel. Some mills using These wheels still in operation In rural appalachia in 1950’s Miller: Mrs. Aarendale

Typical Hydroelectrical Station Outflow water: can be very cold. Why? (Grand Canyon)

Low Head Hydroelectrical Generators Propellor type Turbines Power = Change in Potential Energy per Unit time = weight* Vertical drop/time Energy = Power*time

Microhydro Installation Small stream with Hydroelectrical generator: Power for one family (Jim Keener)

Moderate Head Hydro Head: height difference Between water level in Reservoir and water Level entering turbine Head= height in potential Energy equation Penstock: tube water flows Through

Francis turbine Turbine used for moderate Head hydroelectrical power statiosn

Water Flow in a Francis Turbine Left: relative to turbine blades Right: true water path

High Head Hydro

Pelton Water Wheel Used for high head applications: (above 250 meters) Are impulse turbines. Francis and Propeller type turbine Are reaction turbines. Reaction turbines: run submerged. Impulse turbines: run in normal air

Jets of Water Hitting Pelton Wheel Jets of water are directed through a nozzle onto Pelton wheel Cups on the wheel transfer kinetic energy from water to wheel.

Optimum Hydroelectric Turbine Type Optimum water Wheel: not Just a function Of head, also Depends on Water flow rate

Hydropower Output by Nation Lure of Hydropower Big Dams Vs Rebar

Itaipu Dam Presently world’s largest Hydroelectric plant On Parana river between Brazil and Paraguay Capacity: 12,600 MW (drought a problem recently): Provides: 25% of Brazil power 78% of Paraguay power

Three Gorges Area of Yangtze River Under construction Three Gorges Dam in China Moving 1.2 million People Capacity of 18,600 MW Will finish in 2009

Three Gorges Area Great beauty Many historic Sights Still pressing Ahead on dam construction Gorge length; ~San Francisco To LA

Environmental Problems with Dams 1) Silt buildup fills reservoir (Yangtze; levees) 2) Fish migration disrupted (Columbia) 3)Water temperature decreases (Colorado) 4) Water gets more saline (Colorado) 5) Water loses oxygen (Brazil) 6) Water slows down, increases disease (mosquitos, schitosomiasis (Aswan)) 7) Water traps pollution, slows pollution flushing 8) Induced seismicity may occur