Hydropower from earth

Hydropower (or waterpower) harnesses the energy of moving or falling water. This is usually in the form of hydroelectricity from a dam, but it can be used directly as a mechanical force. The term refers to a number of systems in which flowing water drives a hydraulic turbine or waterwheel.

Prior to the widespread availability of commercial electricity, hydropower was used for milling, textile manufacture, and the operation of sawmills. In the 1830s, at the height of the canal-building era, hydropower was used to transport barge traffic up and down steep hills using the technology of inclined plane railroads.

Hydroelectric power

Main article: Hydroelectricity
Hydraulic turbine and electrical generator.
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Hydraulic turbine and electrical generator.

Hydroelectric power now supplies about 715,000 MWe or 19% of world electricity (16% in 2003). Large dams are still being designed. Apart from a few countries with an abundance of it, hydro power is normally applied to peak-load demand, because it is readily stopped and started. Nevertheless, hydroelectric power is probably not a major option for the future of energy production in the developed nations because most major sites within these nations with the potential for harnessing gravity in this way are either already being exploited or are unavailable for other reasons such as environmental considerations.

Hydropower produces essentially no carbon dioxide or other harmful emissions, in contrast to burning fossil fuels or gas, and so is not a significant contributor to global warming through CO2. Recent reports have linked reservoir construction to methane, which forms out of decaying submerged plants which grow in the dried up parts of the basis in times of drought. Methane is a greenhouse gas.

Hydroelectric power can be far less expensive than electricity generated from fossil fuel or nuclear energy. Areas with abundant hydroelectric power attract industry with low cost electricity. Recently, increased environmental concerns surrounding hydroelectric power, have begun to outweigh cheap electricity in some countries.

The chief advantage of hydroelectric dams is their ability to handle seasonal (as well as daily) high peak loads. When the electricity demands drop, the dam simply stores more water. Some electricity generators use water dams to store excess energy (often during the night), by using the electricity to pump water up into a basin. The electricity can be re-generated when demand increases. In practice the utilization of stored water in river dams is sometimes complicated by demands for irrigation which may occur out of phase with peak electrical demands.