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 traditionalWater wheel

Water wheels: sourceOf power for theIndustrial revolution

Overshot Wheel

More efficient that breast shotWheel. Some mills usingThese wheels still in operationIn rural appalachia in 1950’s

Miller: Mrs. Aarendale

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

Low Head Hydroelectrical Generators Low head:Propellor typeTurbines

Power =Change in PotentialEnergy per Unit time

= weight* Vertical drop/time

Energy = Power*time

Microhydro Installation

Small stream withHydroelectrical generator:Power for one family

(Jim Keener)

Moderate Head Hydro

Head: height differenceBetween water level inReservoir and waterLevel entering turbine

Head= height in potentialEnergy equation

Penstock: tube water flowsThrough

Francis turbine

Turbine used for moderateHead hydroelectrical powerstatiosn

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 turbineAre 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 wheelCups on the wheel transfer kinetic energy from water to wheel.

Optimum Hydroelectric Turbine Type

Optimum waterWheel: notJust a functionOf head, alsoDepends on Water flow rate

Hydroelectrical Power Use by State

States Producing Most Hydroelectricity

Why is thereSo much Variation in theGallons of waterPer kilowatthour?

Hydropower Output by NationLure of Hydropower

Big DamsVs Rebar

Itaipu Dam

Presently world’s largest Hydroelectric plant

On Parana river betweenBrazil and Paraguay

Capacity: 12,600 MW(drought a problem recently):Provides:25% of Brazil power78% of Paraguay power

Three Gorges Area of Yangtze River

Under construction

Three GorgesDam in ChinaMoving 1.2 millionPeople

Capacity of18,600 MW

Will finish in 2009

Three Gorges Area

Great beauty

Many historicSights

Still pressingAhead on damconstruction

Gorge length;~San FranciscoTo 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 flushing8) Induced seismicity may occur