Hydro Electricity

Hydroelectric power or hydropower is the power generated by harnessing the power of moving water.

Flowing water creates energy that can be captured and turned into electricity that is both inexpensive and abundant, it is the largest source of emissions-free, renewable electricity worldwide.
Hydropower is very convenient because it can respond quickly to fluctuations in demand. The production of hydroelectricity is often slowed in the night time when people use less energy. When a facility is functioning, no water is wasted or released in an altered state; it simply returns unharmed to continue the hydrologic cycle. The reservoir of water resulting from dam construction, which is essentially, stored energy.
Power is generated in stations; these electrical generators are attached to a turbine device which spins at great speeds as a result of water rushing through them. These power station turbines are much more efficient at extracting the kinetic energy from the moving water and converting that energy it into power through these generators.

The most common type of hydroelectric power plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. A dam and reservoir is a flexible source of electricity since the amount produced by the station can be changed up or down very quickly to adapt to changing energy demands. The power extracted from the water depends on the volume and on the difference in height between the source and the water's outflow.

Run-of-the-river hydroelectric stations are those with small or no reservoir capacity, so that only the water coming from upstream is available for generation at that moment, it spins the turbine blades by capturing the kinetic energy of the moving water in the river, and any oversupply must pass unused. The volume and speed of water is not augmented by a dam. A constant supply of water from a lake or existing reservoir upstream is a significant advantage in choosing sites for run-of-the-river, they have much less ability to control the amount and timing of when electricity is generated.

Another type of hydroelectric power plant is called a pumped storage plant. This method produces electricity to supply high peak demands by moving water between reservoirs at different elevations. At times of low electrical demand, the excess generation capacity is used to pump water into the higher reservoir. When the demand becomes greater, water is released back into the lower reservoir through a turbine.

A tidal power station makes use of the daily rise and fall of ocean water due to tides. Tidal power is viable in a relatively small number of locations around the world.

Although the generation of hydropower does not emit air pollution or greenhouse gas emissions, it can have negative environmental and social consequences.
Dams that have flooded areas with live vegetation can emit methane.
Hydropower projects can reduce the flows in rivers downstream, lowering the flows in a river can alter water temperatures and degrade habitat for plants and animals.
Dams can also block the migration of fish that swim upstream to reach spawning grounds.
The flooding of land to create reservoirs can also eliminate areas where people live or grow crops.