Hydropower is the term referring to the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy, accounting for 16 percent of global electricity generation – 3,427 terawatt-hours of electricity production in 2010 and is expected to increase about 3.1% each year for the next 25 years.
The cost of hydroelectricity is relatively low, making it a competitive source of renewable electricity. The average cost of electricity from a hydro plant larger than 10 megawatts is 3 to 5 U.S. cents per kilowatt-hour. Hydro is also a flexible source of electricity since plants can be ramped up and down very quickly to adapt to changing energy demands. Once a hydroelectric complex is constructed, the project produces no direct waste, and has a considerably lower output level of the greenhouse gas carbon dioxide (CO2) than fossil fuel powered energy plants.
This type of turbine is used in low pressure plants that use large quantities of water with heads less than 40 meters.
Kaplan Turbines are impeller-turbines, where the runner turns in the water flow like a ship´s propeller. Runner blades and wicket gate are designed adjustable, to ensure an adaption to an unsteady water level and a changing head. These turbines are mostly used in run-of-river power stations.
This type of turbine is regarded as the "all-rounder" and commonly used for medium heads from 20m - 150m.
The Francis-Turbine is a type of turbine, where the water ows radial from the outside inward and sluices axial. Only the wicket gate can be adjusted, therefore it is particularly used with power plants which have a relative constant discharge.
The Pelton Turbine is a type of turbine, which reminds of a tradtional water wheel regarding appearance and mode of operation. The water is conducted through nozzles to the Pelton-cups, is being deflected for almost 180 degrees and releases its energy almost compeltely to the turbine.
This turbine is used at sites featuring high heads up to about 1000 m and low quantities of water, it is the typcial type for plants in high mountains or for reservoir power stations.