Hydroelectric power, or hydropower, is an established and reliable form of renewable energy. It uses the natural water cycle, and gravity, to generate electricity.


For 2000 years, waterpower has been harnessed to do useful work. Waterwheels played a vital role in early industrialization in Europe and North America, powering a wide variety of decentralized manufacturing and processing enterprises. The steel water turbine provided more power at a given site than the waterwheel, and in the U.S. many waterwheel-powered mills were converted to water turbines in the late 19th and early 20th centuries. Blacksmiths and foundrymen produced the turbines and modified the designs during this period of great innovation and profitable production. Water-powered mills produced: "... such household products as cutlery and edge tools, brooms and brushes ... furniture, paper ... pencil lead ... needles and pins ... watches and clocks, and even washing machines .... For the farm they turned out fertilizers, gunpowder, axles, agricultural implements, barrels, ax handles, wheels, carriages. There were woolen, cotton, flax, and linen mills ... tannery, boot and shoe mills ... and mills turning out surgical appliances and scientific instruments."

Rural applications in the developing world

The use of water power in the People's Republic of China has reflected the same pattern, with first water wheels and then turbines being built in great numbers as power demands increased along with technical production capabilities. By 1976 an estimated 60,000 small hydroelectric turbines were in operation in South China alone, contributing a major share of the electricity used by rural communes for lighting, small industrial production, and water pumping.

With the rising cost of energy in the United States today, small hydroelectric units are returning in large numbers. Generating stations along New England rivers are being rehabilitated and put back into operation. The number of companies making small waterpower units has jumped. The U.S. Department of Energy has estimated that 50,000 existing agricultural, recreational, and municipal water supply reservoirs could be economically equipped with hydroelectric generating facilities.

In developing countries, the potential for small hydropower installations has never carefully been measured. Past surveys of hydropower potential have focused on possible sites for large dams, as small hydroelectric units were considered uneconomical or ill-suited to the goal of providing large blocks of electric power for cities, industrial estates, or aluminum production. With the rapidly increasing costs of energy, however, the economics are now much more favorable for small hydroelectric units, which are also well-suited to the needs of small rural communities, and do not bring the degree of environmental disruption associated with large reservoirs. Many small units do not require reservoirs at all, and use small diversion canals instead.

The success of waterpower installations can be greatly affected by forest conservation practices in the watershed above. Rapid deforestation brings high rates of soil erosion and subsequent rapid silt filling of reservoirs behind dams. At the same time, greater rain runoff causes increasingly violent floods that threaten hydropower installations. During the months following the floods, low water flows are likely to reduce generating capacity. A program to protect the watershed and the construction of a diversion canal may be necessary to prevent damage to a small waterpower installation.

Method

A large scale hydroelectric power plant forces water, generally held in a dam, through a hydraulic turbine connected to a generator. After the water exits the turbine it returns to the stream or river below the dam.

Because of the dependence on gravity, hydroelectric power is generally more feasible in mountainous regions than in flat country.

Hydroelectricity has relatively low operations and maintenance costs, especially compared to other forms of renewable energy.

Reliability

Hydroelectricity is a long-established technology, and the process itself is very reliable.

However, hydropower is highly dependent upon precipitation (rain and snow) - droughts can effect generating capacity.

Environmental impact

Hydroelectricity has very little impact on air pollution and climate change, as no fuel is burned. However, vegetation in the flood zone when the dam is built will decay in the lake formed by the dam, releasing methane. The net result is still believed to be a very small amount of greenhouse gases for the electricity produced, but it will vary from dam to dam.

The problems with dams

The largest impact of hydropower is generally from the dam. To avoid the serious negative impacts of a dam, a "run of the river" design is far preferable.

See Alternatives to hydroelectric energy.

Big and small

Microhydro is relatively simple and affordable technology used to provide power to a community. However, this is still many thousands of dollars, typically.

Picohydro refers to tiny generators, possibly made from old car alternators, generating power from a stream of water flowing through a large plastic bucket.

The future of hydroelectricity

The ability to build new generating capacity is extremely limited, especially in developed countries, because:

  • Most suitable sites are already being used.
  • Building a dam is extremely controversial, guaranteed to face strong opposition from environmental groups and owners of affected farms and other property. In practice, only an authoritarian government is likely to choose to build a new dam. In other cases, new capacity must be in the form of smaller "run of the river" systems.

See also


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