Hydroelectric

Hydroelectric power, or hydropower, is electricity generated by converting the energy of moving water into mechanical energy via turbines and generators. It is one of the oldest and most widely used renewable energy sources.

In most installations, water is stored in a reservoir behind a dam or diverted via a canal or penstock to turbines. The flowing water spins turbines connected to electrical generators, producing alternating current.

Types include reservoir-based hydroelectric plants that use storage to regulate output, and run-of-river systems that rely on natural water flow with little or no storage. Pumped-storage facilities use reversible pumps to move water between reservoirs for energy storage.

Advantages include high reliability, long lifespan, low operating costs, and the ability to provide rapid ramping and peak-load support. It has near-zero emissions during operation and can contribute to grid stability.

Environmental and social impacts include ecosystem disruption, sediment transport changes, habitat loss, and displacement. Dam safety, sedimentation, and methane release from reservoirs are considerations, especially in tropical reservoirs.

Globally, hydropower is a major electricity source in many countries, with large schemes such as the Three Gorges Dam, Itaipu, and the Hoover Dam illustrating its scale. Costs are front-loaded, with long-term operational savings.

Limitations include variability in water availability due to droughts and climate change, high capital costs, and environmental concerns. Ongoing research seeks to improve fish passage, biodiversity, and pumped-storage efficiency.