Hydroelectric energy

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Hydroelectric energy (also known as hydroelectric power or hydropower) is produced by using the flow of water to generate electricity. According to the U.S. Energy Information Administration, hydroelectricity accounted for approximately 6 percent of total U.S. electricity generation and 46 percent of electricity generated from renewable energy sources, including wind, solar, and geothermal energy, as of 2015.^[1][2]

Background[edit]

The Chief Joseph Dam in Washington is a run-of-the-river station.

The amount of water available for producing hydroelectricity depends on the amount of precipitation that flows into streams and rivers. The potential for hydroelectric power also depends on seasonal variations in precipitation and the likelihood of changes in precipitation trends, such as droughts.^[3]

Water must move at a sufficient speed and volume to spin a turbine to generate electricity. Impoundments or dams are generally used to increase the volume of moving water. For example, a dam contains an opening in which water is dropped down a pipe. At a sufficient speed and volume, the moving water is able to rotate a turbine. Different kinds of turbines are used at hydroelectric facilities depending on the distance between the turbine and the dam. The turbine rotates the magnets inside a generator to produce electricity. The magnets are mounted near a rotor attached to the turbine shaft. As the rotor turns, the magnets move past nearby conductors. This causes electricity to flow. Hydroelectric facilities with dams can control the generation of electricity by controlling the timing and flow of the water that rotates the turbines.^[2][4][5]

A diagram of a hydroelectric dam

Hydroelectricity can be generated without a dam. The process, known as run-of-the-river, involves capturing kinetic energy from the moving water in a river. This energy is used to spin turbine blades. Run-of-the-river projects cannot store water. Consequently, these projects cannot control the timing and amount of electricity generation as hydroelectric facilities with dams can.^[2][4]

Other hydroelectric facilities use a process called pumped storage. At these facilities, water is pumped into a higher reservoir from a lower reservoir. After water is pumped uphill, it may be used to generate electricity at a later time. When demand for electricity rises, the water is released into the lower reservoir through turbines. Though this process can be used to generate electricity at a later time, some electric power is lost during the process.^[2][4]

Production[edit]

According to the U.S. Energy Information Administration, hydroelectricity accounted for approximately 6 percent of total U.S. electricity generation and 46 percent of electricity generated from renewable energy sources, including wind, solar, and geothermal energy, as of 2015.^[3]

Approximately half of U.S. hydroelectric power was concentrated in Washington, California, and Oregon as of 2015. The largest hydroelectric facility in the United States as of February 2017 was the Grand Coulee Dam in Washington.^[6]

Hydroelectric capacity[edit]

Hydroelectric capacity refers to a facility or state's installed capacity power. The largest share of U.S. total hydroelectricity capacity in 2015 was in the following five states:^[6]

• Washington (27 percent)
• California (13 percent)
• Oregon (11 percent)
• New York (6 percent)
• Alabama (4 percent)

Hydroelectric generation[edit]

Hydroelectric generation refers to the actual energy produced by a facility or state in a given period of time, such as a year. According to the U.S. Energy Information Administration, "Because the amount of electricity generation from hydropower depends on precipitation, the ranking of each state in annual hydroelectricity generation may be different from its ranking in generation capacity." The largest share of U.S. total hydropower generation in 2015 were in the following five states:^[6]

• Washington (38 percent)
• Oregon (13 percent)
• New York (11 percent)
• California (6 percent)
• Alabama (4 percent)

According to the U.S. Department of Energy in 2012, approximately 2,500 dams (3 percent) of the approximately 80,000 dams in the United States produced hydroelectricity. The remaining dams were used to suppress floods and/or provide water for human consumption, irrigation, industrial use, or navigability.^[7]

The chart below shows hydroelectric power generation compared to other renewable energy sources from 1995 to 2015.^[3]

Hydroelectric power generation compared to other renewable energy sources from 1995 to 2015

Regulation[edit]

The Federal Power Act authorizes the Federal Energy Regulatory Commission (FERC) to issue licenses for the construction of new hydroelectric facilities. FERC also renews licenses for existing hydroelectric facilities. FERC staff prepare and use environmental assessments and environmental impact statements in setting licence conditions for hydropower operators. As of July 2015, FERC regulated approximately 1,700 privately owned dams in the United States. Under the Federal Power Act, FERC must consider whether a proposed or existing hydroelectric project is consistent with federal and state plans aimed at developing and conserving bodies of water. FERC is required to examine any potential waters that may be affected by a hydroelectric project. The agency also inspects hydroelectric dams for safety.^[8]

Impact[edit]

Environmental impact[edit]

Hydroelectric facilities do not produce air pollutants or water pollution because they do not use fuels such as coal or natural gas. As a result, increased reliance on hydroelectric power facilities rather than coal, oil, or natural gas can result in fewer pollutants released into the air and thus less air pollution, such as smog. Hydroelectricity is also generated by using the water cycle and does not rely on a finite resource, such as natural gas, crude oil, or coal. In addition, hydroelectric plants use running water to generate electricity without reducing water supplies. Other environmental benefits include the creation of reservoirs, which collect rainwater. Reservoirs can be used for fishing, swimming, boating, or other recreational activities. Additionally, dams near hydroelectric power facilities can be used for flood control, irrigation, and drinking water.^[9][10]

Fish ladders (structures on or around a dam) are used at hydroelectric facilities to allow for the natural migration of fish.

Hydroelectric facilities may reduce downstream river flow if upstream river flow is behind a reservoir or diverted to a hydroelectric facility. Because the water is diverted to a facility, downstream river flows may be different from natural flow patterns. For example, some rivers generally have higher flows in winter and spring than in summer and fall. If hydroelectric facilities follow a relatively static flow schedule to divert water for electricity generation compared to what a river may normally have, sediment movements may be disrupted along a river and reduce habitat for fish and other aquatic species.^[2][11][12]

Dams may block the migration of fish such as chinook, coho, and salmon, which move upstream in order to reproduce in spawning areas. Fish may also be prevented from passing downstream from a river to the ocean or be caught in a dam's turbines. To mitigate these impacts, the U.S. National Oceanic and Atmospheric Administration (NOAA) requires hydroelectric dams to provide passages allowing fish to migrate to and from spawning areas and may require hydroelectric operators to agree to protective measures for fish and wildlife as part of their dam licenses.^[11][12][13]

The presence of a hydroelectric facility may affect land use depending on the facility's size. Hydroelectric facilities in flat areas may require more land than in areas with hills or canyons, which contain reservoirs that can hold more water in a smaller space. Some lands may need to be flooded to create a reservoir for hydroelectricity generation. This may result in fewer forested lands, agricultural lands, and potential residential areas.^[11][12][14]

Economic impact[edit]

Depending on the site and materials needed, new hydroelectric power facilities can have high capital costs. Consequently, a higher cost may inhibit the implementation of a hydroelectric facility without sufficient funding. Moreover, a large-scale implementation of hydroelectric facilities may require local, state, or federal government funding to cover initial costs. According to the U.S. Energy Information Administration, the base cost estimate for a hydroelectric facility with a capacity of 500,000 kilowatts in 2012 dollars was $1,467,787. Of that total, the cost to the facility's owner was $244,631.^[15][16]

According to the National Hydropower Association, a hydroelectric power advocacy group, hydroelectric power can include the following economic benefits:^[17]

• States with more hydroelectric power, specifically Idaho, Washington, and Oregon, have lower energy costs on average than other states.
• Hydroelectric facilities do not depend on the price of oil, natural gas, and gasoline.
• Hydroelectricity generation has lower maintenance, operational, and fuel costs compared to other sources of electricity. According to a 2010 study by the American Council of Renewable Energy, a renewable energy advocacy group, hydroelectric power had a cost of 2 cents per kilowatt hour compared to 6 cents for wind energy, 16.5 for solar energy, 6 cents for natural gas, and 7.5 cents for coal.

Total investment costs for hydroelectric facilities depend on the site location, the design of the equipment, and the cost of materials and labor. According to a June 2012 study by the International Renewable Energy Agency (IRENA), an intergovernmental organization that supports renewable energy, total installation costs for large hydroelectric facilities (which produce 100 megawatts or more of electricity) range between $1,000 per kilowatt to $3,500 per kilowatt. Other projects, such as an existing dam that had hydroelectric capacity installed previously, may have costs below this range. Other projects, such as projects in areas with less infrastructure, may go above this range. According to the report, small hydroelectric facilities (which produce between 1 megawatt to 100 megawatts of electricity) had total installation costs from $1,300 per kilowatt to $8,000 kilowatt. The report found that investment costs (per kilowatt) for smaller plants were generally lower if the plants had more reservoir and installed capacity.^[18]

See also[edit]

• 

  Ethanol

• 

  Solar energy

• 

  Wind energy

• 

  Glossary of energy terms

Footnotes[edit]

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