hydroelectricity

Hydroelectricity is electricity generated from the energy of flowing or falling water. In a hydroelectric power plant, water stored at height or diverted from a river is directed through a turbine. The turbine turns a generator, producing electricity that is transmitted to the power grid. The process converts hydraulic energy into mechanical energy and then into electrical energy, with minimal fuel consumption once built.

The principal configurations are impoundment systems that use a dam and reservoir, run-of-river installations that rely on natural river flow, and pumped-storage facilities that move water between two reservoirs to store energy for times of high demand. Micro-hydro systems operate at small scales. Key components include a water intake, penstock or conduit, turbine, generator, transformer, and transmission lines.

Hydropower plants are known for high efficiency, with modern turbines and generators achieving overall efficiencies around 85-95%. They can ramp quickly to meet demand and, in pumped-storage arrangements, provide storage and grid balancing. They often have long lifespans and relatively low operating costs compared with fossil-fuel plants.

Advantages include low operating emissions, a large and reliable supply of electricity, and the ability to provide additional benefits such as flood control, irrigation support, and water supply. Disadvantages include high upfront capital costs, ecological and social disruption from dam construction, sedimentation and methane emissions in reservoirs, and sensitivity to drought and climate variability. Mitigation measures include environmental flow requirements, fish passages, and careful reservoir management.

Globally, hydroelectricity accounts for a substantial share of renewable energy and a significant portion of total electricity generation. Global installed hydro capacity is on the order of over a terawatt. Hydropower has a long history dating to the late 19th century and remains a dominant form of renewable power, though development is increasingly constrained by environmental and social considerations.