Hydropower is the production of power through the use of the gravitational force of water. In traditional Hydropower, the force of water flowing downhill is used to power the station's turbines.

as of 2006, hydroelectric power supplied about 715,000 megawatts or 19% of world electricity. Large dams are still being designed. The world's largest is the Three Gorges Dam on the third longest river in the world, the Yangtze River. Apart from a few countries with an abundance of hydro power, this energy source is normally applied to peak load demand, because it is readily stopped and started. It also provides a high-capacity, low-cost means of energy storage, known as "pumped storage".

Hydropower produces essentially no carbon dioxide or other harmful emissions, in contrast to burning fossil fuels, and is not a significant contributor to global warming through CO₂.

Hydroelectric power can be far less expensive than electricity generated from fossil fuels or nuclear energy. Areas with abundant hydroelectric power attract industry. Environmental concerns about the effects of reservoirs may prohibit development of economic hydropower sources.

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 (which provides more flow when it releases). 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. Electricity can be 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.

Not all hydroelectric power requires a dam; a run-of-river project only uses part of the stream flow and is a characteristic of small hydropower projects. A developing technology example is the Gorlov helical turbine.

Run-of-the-river hydropower is a type of hydroelectric generation whereby the natural flow and elevation drop of a river are used to generate electricity. Run of the river projects do not require a large impoundment of water through a large reservoir. Power stations of this type are built on rivers with a consistent and steady flow. Run of the river diverts some of the water for the generation of electrical energy. The water leaves the generating station and is returned to the river without altering the existing flow or water levels. Flooding the upper part of the river is not required as it doesn't need a reservoir. As a result, people living at or near the river don't need to be relocated and natural habitats are preserved, reducing the environmental impact as compared to reservoirs.

Many run-of-the-river power plants will have a dam across the full width of the river to utilize the entire river's force for electricity generation. Such installations will have a small reservoir behind the dam but since flooding is minimal, they can be considered "run-of-river."

Investments in run of river hydropower plants can produce solid returns for investors.  New technologies and processes present strong upside potential for speculative investing in run of the river hydro power and can also be more risky.

The following are the main requirements for a run of the river project.

•    Intake weir – This system is built to draw water from the river creating a small ‘headpond’ of water.

•    Penstocks – Pipes that deliver the water from the headpond to the turbines in the power station downstream.  Penstocks can represent 50% of a project’s cost.

•    Powerhouse for the turbines and generators – The turbines and generators are the 'heart' of a project. Each turbine and generator is uniquely designed for a site.  Design is determined by the head, or the difference in the elevation of water at the penstock and the elevation of the turbine inlet located in the powerhouse, flow and volume of water at each site.

•    Tailrace – A channel through which the diverted water is returned to its natural flow in the river.

•    Access roads – Roads may have to be constructed to get to and from the project site.

•    Transmission lines – Transmission lines from the powerhouse to the local transmission grid.

There are several forms of water power currently in use or development. Some are purely mechanical but many primarily generate electricity. Broad categories include:

• Waterwheels, used for hundreds of years to power mills and machinery
• Hydroelectricity, usually referring to hydroelectric dams, or run-of-the-river setups (eg hydroelectric-powered watermills)
• Damless hydro, which captures the kinetic energy in rivers, streams and oceans
• Vortex power, which creates vortices which can then be tapped for energy
• Tidal power, which captures energy from the tides in horizontal direction
• Tidal stream power, which does the same vertically
• Wave power, which uses the energy in waves
• Osmotic power, which channels river water into a container separated from sea water by a semipermeable membrane.
• Marine current power which captures the kinetic energy from marine currents.
• Ocean thermal energy conversion which exploits the temperature difference between deep and shallow waters.

Investing in Hydropower

Investments in hydropower can come in the form of direct investments in hydropower generation plants or by investing in companies with new technologies for hydropower generation. Due to the fact that hydropower is not widely invested in, hydropower and investing in hydropower technologies can be considered very speculative.

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This article is licensed under the GNU Free Documentation License. It uses material in whole or in part from the Wikipedia article "Hydropower"

More information from this article was sourced from: http://ga.water.usgs.gov/edu/wuhy.html