Hydroelectric Power http://www.nrel.gov/gis/docs/resource_maps_200905.ppt http://www.eia.doe.gov/oiaf/aeo/index.html http://www.window.state.tx.us/specialrpt/energy/exec/hydro.html http://ga.water.usgs.gov/edu/wuhy.html http://www.eia.doe.gov/fuelrenewable.html

Overview Hydroelectric Energy comes from the force of flowing water and has been used for centuries. The sun is a prime influence on natural cycles that create rain and melts ice that makes rivers flow into oceans and lakes. This flow is the source of hydropower. It is the most widely used form of renewable energy in the country and the world providing about 96 percent of the renewable energy in the United States The largest hydroelectric power plant in the world is at Three Gorges Dam in China on theYangtze River. Hydropower is clean in that it does not produce harmful emissions, but habitats have been harmed and many people have been displaced from their traditional villages by damming rivers.

Advantages Hydroelectric generators release almost no CO2. Although start-up costs can be high, hydroelectric power plants have been providing low-cost electricity to much of the world for decades. Because of the water cycle it is renewable. Water flows all day and night, so hydropower provides a constant source of electricity. Hydroelectric plants have long life spans (50+ years) and low operational cost. Hydro power is produced domestically reducing the problems created by dependence on foreign energy sources. Dams can provide recreational areas such as Amistad Reservoir.

Disadvantages Hydropower best serves those living close to waterways. Dams can force people and animals to resettle and can damage river ecosystems. Relocation of peoples causes cultural concerns when such things as burial sites are disturbed. At the Three Gorges Dam recently built in China, over 9,000 archaeological sites have been submerged under water. Plants and other organic matter decaying in the lakes behind dams can produce significant amounts of greenhouse gases. There is no power when droughts occur.

Technical Considerations There are 3 types of hydropower facilities: Impoundment is the most common type of hydroelectric power plant. Usually these are large hydropower systems, using a dam to store river water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which activates a generator to produce electricity. A diversion facility channels a portion of a river through a canal or penstock. It may not require the use of a dam. When the demand for electricity is low, a pumped storage facility stores energy by pumping water from a lower reservoir to an upper reservoir. During periods of high electrical demand, the water is released back to the lower reservoir to generate electricity.

Economic Considerations There are no fuel source costs for hydropower. Although the cost of building hydroelectric plants is high, they have long life spans (50+ years) and low operational costs. Reservoirs provide irrigation for farmers, conservation lands for wildlife, and recreational areas.

Environmental Considerations Stagnation of plant flora in reservoirs can cause a great degree of methane and CO2. In the future, new methods of clearing the land before flooding an area to create a reservoir will prevent this problem. Facilities can cause erosion and damage to flora and fauna above and below the dam. Failures of large dams, while rare, are potentially serious - the Banqiao Dam failure in Southern China resulted in the deaths of 171,000 people and left millions homeless.

Legal/Regulatory Considerations FERC, the Federal Energy Regulatory Commission oversees dam safety and inspections, and licensing for dams. In the U.S. participation of the citizens in the licensing process should make the removal of people in area of reservoir equitable. In other parts of the world. Displacement is a larger problem: The Three Gorges Project has displaced over 1,000,000 people, the world’s largest dam-displaced population Danjiangkou Dam on the Han River (380,000) Sanmenxia Dam on the Yellow River (320,000) Aswan High Dam between Egypt and Sudan (100,000)

Anticipated Status About 10% of U.S. electricity comes from hydropower. Today, there is about 80,000 MW of conventional capacity and 18,000 MW of pumped storage. Research for hydroelectric power is focusing on eliminating the environmental problems since the technology for the facilities is already in place and tested. The U.S. Department of Energy has completed a resource assessment of the states. The completed work has identified 5,677 sites in the United States with undeveloped capacity of about 30,000 MW. By comparison, today there is about 80,000 MW of hydroelectric generating plants in the United States. Scientists are working on harnessing tidal power.

Summary Hydroelectric power sounds great -- so why don't we use it to produce all of our power? Mainly because you need lots of water and a lot of land where you can build a dam and reservoir, which all takes a LOT of money, time, and construction. In fact, most of the good spots to locate hydro plants have already been taken. In the early part of the century hydroelectric plants supplied a bit less than one-half of the nation's power, but the number is down to about 10 percent today. The trend for the future will probably be to build small-scale hydro plants that can generate electricity for a single community.