Hydro electric power plants utilize water in huge reservoirs to generate electricity. A dam is usually built across a body of water, creating a reservoir behind it. The dam is built with huge turbines located inside the dam. Outlets are created for the water from the reservoir to flow to the other side of the river when the reservoir is full. The outlets are opened and closed when required. When the outlets are opened, water rushes in at high speeds and drives the turbines. The turbines are connected to alternators which produce electricity. The cost of hydroelectricity is low, making it a competitive source of renewable energy. The hydro station consumes no water at all, unlike gas or coal stations. It is a flexible source of electricity, as this source of energy generation can be varied upwards or downwards rapidly, to adapt to changing energy demands. Once this plant is constructed, it produces no waste and its emission of greenhouse gases is considerably lower than other power generating plants like coal or gas.
2. Pumped storage
3. Run of the river
This involves the use of dams through which water flows at high pressure to drive a series of turbines. The turbines are connected to a generator which produces electricity. As the turbines rotate, they drive the generator to produce electricity. The amount of electricity produced varies with the water flow, thus huge amounts of electricity are produced during the rainy season and the amount drops during the dry season where there is little or no rain.
This method produces electricity to supply when the demand is high by moving water between reservoirs at different elevations. At times of low demand of electricity, the excess generation capacity is used to pump water into the higher reservoir. When the demand increases, water is released back into the lower reservoir through a turbine. This method currently provide the most commercially important means of large scale energy grid storage and improve the daily capacity factor of the generation system.
Run of The River.
These hydroelectric stations are those with small or no reservoir capacity, so that only water coming from upstream is available for generation at the moment. Any oversupply must pass unused. A constant supply of water from a lake or reservoir upstream is a significant advantage in choosing sites for this hydro plant type.
This power station utilizes the daily rise and fall of the ocean tides to generate electricity. It allows for construction of reservoirs which are dispatchable to generate power during high demand periods. Tidal power generation is viable in small parts of the world, and research and development are ongoing on these sites to determine how much electricity can be developed using this technology.