1. 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

2. Energy in the News

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

4. 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

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

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

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

8. 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

9. Francis turbine Turbine used for moderate Head hydroelectrical power
statiosn

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

11. High Head Hydro

12. 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

13. 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.

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

15. Hydropower Output by Nation
Lure of
Hydropower
Big Dams Vs
Rebar

16. 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

17. 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

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

19. 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