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Hydropower (from Ancient Greek ὑδρο-, "water"), also known as water power, is the use of falling or fast-running water to produce electricity or to power machines. This is achieved by converting the gravitational potential or kinetic energy of a water source to produce power. [1] Hydropower is a method of sustainable energy production.
Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity , almost 4,210 TWh in 2023, [ 1 ] which is more than all other renewable sources combined and also more than nuclear power . [ 2 ]
During periods of high electrical demand, the stored water is released through turbines to produce electric power. Pumped-storage hydroelectricity allows energy from intermittent sources (such as solar , wind , and other renewables) or excess electricity from continuous base-load sources (such as coal or nuclear) to be saved for periods of ...
Marine energy or marine power (also sometimes referred to as ocean energy, ocean power, or marine and hydrokinetic energy) refers to the energy carried by ocean waves, tides, salinity, and ocean temperature differences.
Water is stored in the reservoir during periods of low demand and released when demand is high. The net effect is similar to pumped storage, but without the pumping loss. While a hydroelectric dam does not directly store energy from other generating units, it behaves equivalently by lowering output in periods of excess electricity from other ...
The stored potential energy is later converted to electricity that is added to the power grid, even when the original energy source is not available. Electricity can be stored directly for a short time in capacitors, somewhat longer electrochemically in batteries , and much longer chemically (e.g. hydrogen), mechanically (e.g. pumped hydropower ...
Once built, the water stored behind the dam raises the water table and is then extracted with wells. A sand-storage dam is a weir built in stages across a stream or wadi. It must be strong, as floods will wash over its crest. Over time, sand accumulates in layers behind the dam, which helps store water and, most importantly, prevent evaporation ...
Some reservoirs generating hydroelectricity use pumped recharge: a high-level reservoir is filled with water using high-performance electric pumps at times when electricity demand is low, and then uses this stored water to generate electricity by releasing the stored water into a low-level reservoir when electricity demand is high.