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Hydropower is now used principally for hydroelectric power generation, and is also applied as one half of an energy storage system known as pumped-storage hydroelectricity. Hydropower is an attractive alternative to fossil fuels as it does not directly produce carbon dioxide or other atmospheric pollutants and it provides a relatively ...
Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator. The power extracted from the water depends on the volume and on the difference in height between the source and the water's outflow. This height difference is called the head.
Kaplan turbine and electrical generator cut-away view. The runner of the small water turbine. A water turbine is a rotary machine that converts kinetic energy and potential energy of water into mechanical work. Water turbines were developed in the 19th century and were widely used for industrial power prior to electrical grids. Now, they are ...
The system is prevented from 100% efficiency (from obtaining all 5.65 kW) due to the real world, such as: turbine efficiency, friction in pipe, and conversion from potential to kinetic energy. Turbine efficiency is generally between 50-80%, and pipe friction is accounted for using the Hazen–Williams equation. [8]
The energy storage in gigawatt-hours (GWh) is the capacity to store energy, determined by the size of the upper reservoir, the elevation difference, and the generation efficiency. Countries with the largest power pumped-storage hydro capacity in 2017 [ 65 ]
Most current hydroelectric projects use a large hydraulic head to power turbines to generate electricity. The hydraulic head either occurs naturally, such as a waterfall, or is created by constructing a dam in a river valley, creating a reservoir. Using a controlled release of water from the reservoir drives the turbines.
The pump-turbine units were uprated in July 1972 from their initial rating of 175 MW each to 204 MW each, increasing the plant's overall rating from 350 MW to 408 MW. [3] [16] From 1998–1999, the turbine runners for both units were upgraded, resulting in improved flow rates and another power uprate to 225 MW per unit (450 MW total). [17] [16]
The turbine drives a generator, thus transforming its mechanical energy into electrical energy by electromagnetic induction. There are many different methods of developing mechanical energy, including heat engines, hydro, wind and tidal power. Most electric generation is driven by heat engines.