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Hydroelectric Power In California


Hydro power is a major source of California's electricity. During 1999, hydroelectric power plants produced 41,617 gigawatt-hours of electricity -- 15.1 percent of the total. California's 386 hydro plants are mostly located in the eastern mountain ranges and have a total dependable capacity of about 14,116.53 MW of capacity. The state also imports hydro-generated electricity from the Pacific Northwest.

The larger hydro plants on dams in California (such as Shasta [pictured on the right in this U.S. Bureau of Reclamation photo], Folsom, Oroville, etc.) are operated by the U.S. Bureau of Reclamation and the state's Department of Water Resources. Smaller plants are operated by utilities, mainly Southern California Edison, Pacific Gas and Electric Company and Sacramento Municipal Utility District. Licensing of hydro plants is done by the Federal Energy Regulatory Commission with input from environmental protection, fish and wildlife, and water quality agencies.

[Shasta Lake and Dam, USBR photo]
Shasta Dam, Photo Courtesy US Bureau of Reclamation

Hydroelectric power, a renewable resource, is generated by hydraulic turbines that rotate due to the force of moving water as it flows from a higher to a lower elevation. (See the Consumer Energy Center for "How Hydro Works".) The water can be flowing in natural streams and rivers or contained in man-made facilities such as reservoirs, pipelines and canals. There are two main categories of hydroelectric power generation: conventional methods, which produce electricity via water flow in one direction (and are therefore dependent on seasonal runoff), and pumped storage methods, which are both producers and consumers of electricity as the water used to generate electricity can be recycled by pumping it back uphill.

Two types of conventional hydroelectric facilities are dams and run-of-river. Dams raise the water level of a stream or river to an elevation necessary to create a sufficient elevation difference (water pressure, or head). Dams can be constructed of earth, concrete, steel or a combination of such materials. Dams may create secondary benefits such as flood control, recreation opportunities and water storage. Run-of-river, or water diversion, facilities typically divert water from its natural channel to run it through a turbine, and then usually return the water to the channel downstream of the turbine.

Such conventional methods offer the potential for low-cost baseload electricity, but their output is dependent on the time of year as well as annual precipitation. By contrast, pumped storage methods are typically used to provide power during peak demand periods on very short notice and are not dependent solely on runoff.

In a pumped storage facility, water is pumped during off-peak demand periods from a reservoir at a lower elevation for storage in a reservoir at a higher elevation. Electricity is then generated during peak demand periods by releasing the pumped water from the higher reservoir and allowing it to flow downhill through the hydraulic turbine(s) connected to generators.

During the off-peak pumping cycle, the pumped storage facility is a consumer of electricity: in fact, the amount of electricity required to pump the water uphill is greater than the amount of electricity that is generated when the water is released during peak demand periods. Pumped storage facilities, however, are economical because they consume low-cost off-peak electricity, but generate high-value on-peak electricity.

Pumped storage methods include both typical on-stream conventional and modular off-stream technologies. The major differences between modular pumped storage (MPS) and conventional pumped storage is that MPS systems are much smaller, use closed water systems that are artificially created instead of natural waterways or watersheds, and sites are selected with predetermined elevation differences so that modular pre-engineered equipment can be used. With the exception of evaporative losses, reservoirs are charged only once, either with groundwater or even municipal wastewater.

Permitting Issues. Some of the issues associated with conventional hydroelectric power generation and typical on-stream pumped hydroelectric storage facilities include:


Because MPS systems are not dependent on natural waterways and watersheds, they can be sited in areas that avoid many of the issues described above. In fact, desirable sites are not near rivers, lakes, streams and other sensitive environmental areas in order to avoid the regulatory complexity and time associated with conventional pumped hydroelectric storage facilities.

References

  1. Resource: An Encyclopedia of Energy Utility Terms, Pacific Gas and Electric Company, 2nd edition, 1992, pp. 171, 238-239, 341-342, and 363-364.

  2. Small But Powerful -- A Review Guide to Small Alternative Energy Projects for California's Local Decision makers, Association of Bay Area Governments, September 1987, pp. 14, 36-41.

  3. Glenn County Energy Element of the General Plan, June 1993, pp. 119-127.

  4. 1992 Energy Technology Status Report - Final Report, California Energy Commission, Report no. P500-92-007, December 1992. Fact Sheet 7.1 (Conventional Hydroelectric), 16.1.1 (Conventional Pumped Hydroelectric), and 16.1.2 (Modular Pumped Hydroelectric).

  5. 1992 Energy Technology Status Report, Appendix A, Volume II: Detailed Electric Generation Technology Evaluations, California Energy Commission, Report no. P500-92-007A V2, December 1992. Sections 16.1.1 (Pumped Storage Hydroelectric) and 16.1.2 (Modular Pumped Storage).

Source: Energy Aware Planning Guide II: Energy Facilities.



Reports & Documents

California Energy Commission Scoping Comments On PG&E Hydro Valuation & Divestiture (June 1, 2000) (Adobe Acrobat PDF, 15 pages, 43 kilobytes, placed on-line July 18, 2000)

Other Information




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Page Updated: May 22, 2001