Power Generation:

Disadvantages to power plants that use coal, oil, and gas fuel:

They use up valuable and limited natural resources
They can produce a lot of pollution
Companies have to dig up the earth or drill wells to get the coal, oil, and gas


For nuclear power plants there are waste-disposal problems

Fuel is not burned so there is minimal pollution
Water to run the power plant is provided free by nature
It's renewable - rainfall renews the water in the reservoir, so the fuel is almost always there

World's Biggest Hydro Power Plan

Grand Coulee Dam

Hydro Power in California

What about the Three Gorges Dam Project? (18,000 MegaWatts) Good or Bad?

Historical Growth of Hydroelectric power:

• Currently Hydro power is 7% of the total US Energy Budget. This has been going decreasing with time
• This varies considerably with region in the US due to the availability of freely flowing streams
• Dam building really was initiated in the 1930's as part of a public works program to combat the depression
• Low cost per KWH (see below) caused exponential increase of dam building from 1950-1970 (lots of this on the Columbia)
• Since 1970 hydro-production has leveled off and therefore becomes an increasingly smaller percentage of the US energy budget.

Hydropower is a natural renewable energy source as it makes use of The Hydrological Cycle:

About 30% of the hydro-potential in the US has been tapped to date but this is unlikely to increase in the near future.

Why is Hydro so attractive?

• BECAUSE ITS CHEAP! for the consumer average price in the PNW is 4-4.5 cents per KWH this is at least 50% of the national average!

  • Low cost to the consumer reflect relatively low operating costs of the Hydro Facility. Most of the cost is in building the dam
  • Operating costs about 0.6 cents per KWH
  • Coal Plant averages around 2.2 cents per KWH which reflects costs of mining, transport and distribution.

Potential energy = mgh

m = mass of water
g = gravitational acceleration on Earth (9.8 meters/sec² which we will approximate as 10)
h = height above earth's surface.

Energy density in stored elevated water is high:

• So one liter of water per second when dropped from a height of 90 meters on a turbine generates 720 watts of power.

• If this power can be continuously generated for 24 hours per day for one month then the total number of KWH per month is then:
  720 watts x 24 hours/day x 30 days/month = 518 KWH/month.

  Power generating capacity is directly proportional to the height the water falls. For a fall of say only 3 m, 30 times less electricity would be generated (e.g. 17 KWH/month) - but this is just for a miniscule flow rate of 1 kg/sec.

  Capacities of some large dams:

  Grand Coulee            1942 6500 MW
  John Day                1969 2200 MW
  Niagara (NY)            1961 2000 MW
  The Dalles              1957 1800 MW
  Chief Joseph            1956 1500 MW
  McNary                  1954 1400 MW
  Hoover                  1936 1345 MW
  Glen Canyon             1964  950 MW
  Three Gorges            2005 18000 Mw
  

  Controversy over the 3 Gorges Dam

  Pacific Northwest has 58 hydroelectric dams 63% of total electricity generated. Most of the rest comes from coal fired steam plants (e.g. Centralia Washington).

  Note, the Trojan Nuclear Power Plant was relatively easy to shut down because replacement power was immediately available.

  Again the main advantages of Hydro are a) its renewable and b) there is a lot of energy available:

  

  Some Real Disadvantages:

  

  Hydroelectric Power - The Risks:

  Dams are frequently located upstream from major population centers:
  • 1918--1958: 33 Major dam failures resulting in 1680 documented fatalities
  • 1959--1965: 9 major dams failed throughout the world
  • 1976: Teton Dam failure in Idaho
  • Most of the dams on the Colombia have been built since 1950 and are not close to their failure points

    Internet Resources:

  • Overview of Hydropower and the Issues

  • The Columbia River Salmon Passage model (CRiSP)