HYDROELECTRIC (Also see Hydro and Pumped Storage Flash animations)

There are two kinds of hydroelectric plants (dams)

1. "run-of-the-river": water is used continuously with limited reservoir storage (e.g., Bonneville on lower Columbia)
2. "storage": water is released as needed and available (e.g., Glen Canyon in Arizona)

The dams may have several purposes including

• electricity generation,
• flood control,
• navigation,
• irrigation,
• public water supply, and
• recreation.

Advantages of hydroelectric plants include

• operation and maintenance costs are low
• generating plants have a long lifetime
• unscheduled breakdowns are relatively infrequent and short in duration since the equipment is relatively simple
• hydroelectric turbine-generators can be started and put "on-line" very rapidly

Disadvantages of hydroelectric plants include

• very land-use oriented and may flood large regions
• fish migration is restricted
• fish health affected by water temperature change and insertion of excess nitrogen into water at spillways
• available water and its temperature may be affected
• reservoirs alter silt-flow patterns

The basis of hydroelectric power generation is that water at height has certain potential energy. The height is referred to as the head. The maximum power obtained from a hydro plant may be computed by multiplying the head, water density, and volumetric flow rate.

Also related to hydroelectric is the practice of using pumped storage facilities as an energy storage device. Pumped storage facilities consist of both high-elevation and low-elevation reservoirs. The pumped storage uses electricity during low demand times to pump water from the low-elevation reservoir to the high-elevation reservoir. Then during peak power demands the water is allowed to flow back down, turning a turbine like that used in a dam.

Electric Nuclear Hydro Solar