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What Are the Causes of Hydroelectric Energy Resources?

Hydroelectric power is the leading renewable energy source, contributing to 81 percent of renewable energy use in the United States. Approximately 90 percent of hydroelectric energy produced is converted to electricity at one-third the cost of fossil fuel and one-sixth the cost of natural gas. Power is generated by utilizing a turbine and alternator to convert kinetic energy of water flow into electrical energy. There are several causes of hydroelectric resources, including dams, Run of River, tidal and pumped hydroelectric energy storage.

  1. Dams

    • There is only one undammed river longer than 600 miles in the U.S. There are more than 75,000 dams, but fewer than 3 percent are used to generate electricity. Water is stored in the dam with a gate to regulate the amount of water released according to energy requirements. Dams alter the natural flow of rivers, affecting the habitats of aquatic species. It also floods large areas of land, which affects riverside communities.

    Run of River

    • Run of River diverts the flow of the river towards turbines that generate electricity. Afterwards the water is re-diverted to its natural course. The low head technique temporarily stores water in a small dam, while the high head technique relies on gravity from mountainous regions. Run of River reduces the effect on water levels and natural river flow compared with conventional dams, and does not cause flooding.

    Tidal Energy

    • Tidal energy is harnessed from the changing tides at ocean bays. Incoming tides flow through low dams or barrages containing one-way gates. As the tide flows out, water passes through built-in turbines. This method is not as cost-effective as others, as barrages are expensive to build. Moon cycles and seasonal fluctuations of tides also affect the amount of energy produced.

    Pumped Hydroelectric Energy Storage

    • In this system, water is pumped from an upper reservoir through to a turbine and then collects in the lower reservoir. When energy demand is low, water is pumped in reverse and stored in the upper reservoir, allowing large amounts of energy to be stored for long periods. Areas where two reservoirs exist are hard to locate. This is overcome by developing underground storage systems, thus only one reservoir needs to be on the surface.

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