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TECHNOLOGY: Hydropower

Hydroelectric (hydropower) systems capture the energy in flowing water and convert it to electricity. Although the potential for small hydroelectric systems depends on the availability of suitable water flow, where the resource exists it can provide cheap, clean, reliable electricity. Small hydroelectric systems blend with their surroundings and have minimal negative environmental impacts. Small- and medium-scale hydroelectric systems are those that produce less than 20 megawatts of electricity. Pumped storage allows excess energy to be stored for later use. Small hydropower, (up to 20 megawatts), with its multiple advantages as a decentralized, low-cost and reliable form of energy, is in the forefront of many countries’ programs to achieve energy self-sufficiency. Small hydro systems allows for rural electrification, petroleum substitution, rural development of isolated areas, and a cleaner environment.

Micro-hydroelectric projects are those that generate less than one megawatt of power.

There are three major types of hydroelectric systems:

?    Impoundment; An impoundment facility, typically a large hydropower system, uses a dam to store river water in a reservoir. The water may be released either to meet changing electricity needs or to maintain a constant reservoir level.
?    Diversion; A diversion, sometimes called run-to-river, system, channels a portion of a river through a canal or penstock. It may not require the use of a dam. Rum-of-the-river plants derive energy from a water flow without disrupting it as much as conventional hydroelectric power plants.
?    Pumped Storage; 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.

Run-of-the-river hydroelectric plants use the power in river water as it passes through the plant without causing an appreciable change in the river flow. Normally such systems are built on small dams that impound little water. Many times a reservoir and a dam are not even required, so a run-of-river project may not cause the water quality changes such as higher temperature, low oxygen, decreased food production, siltation, increased phosphorus and nitrogen, or decomposition products associated with other hydroelectric systems.

Run-of-the-river hydro plants do not normally affect downstream habitat or terrestrial habitat. Effects such as oxygen depletion, temperature elevation, inadequate minimum flows and ladder rejection by fish are not problems. Although run-of-river plants can be quite small, many are large and there is at least one such 10,000 megawatt dam in South America.

A hydropower system may possess other features which offer much more than just electricity or mechanical energy. Hydropower sites often offer means for irrigation, fire control, drinking water, and recreational fishing and boating.



Category/ies:Hydropower Tech.
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