hydropower

Hydropower, or hydroelectric power, is electricity generated from the energy of moving water. It relies on the conversion of water’s potential and kinetic energy into mechanical energy by a turbine, which drives an electrical generator. The available energy depends on water flow and height difference (head). In impoundment systems, a dam creates a reservoir; water released through turbines produces electricity. Run-of-river systems divert a portion of a river's flow with little or no storage. Pumped-storage facilities store energy by pumping water uphill to a reservoir during low-demand periods and releasing it through turbines to meet peak demand.

Key components include a dam or diversion structure, reservoir or intake, a penstock or tunnel, turbines, generators, transformers, and transmission lines. Hydropower is highly efficient and capable of providing baseload power as well as rapid ramping for grid balancing. It is a renewable source with very low greenhouse gas emissions during operation, though reservoirs may emit methane in tropical regions and large developments can affect local ecosystems, fish migration, sediment transport, and communities.

Development began in the late 19th century; the first hydroelectric power plant began operation in 1882 at Appleton, Wisconsin, and the technology expanded rapidly thereafter. Global deployment ranges from small-scale micro-hydro to large-scale plants. Hydropower has been a central part of modern electricity systems for over a century and remains a major source of renewable electricity, with pumped storage playing a key role in energy storage and grid resilience.