How a Hydroelectric Dam Turns Water Into Watts

A hydro plant converts the potential energy of stored water into rotation. Head, the height water falls, times flow sets the power available: double either and power doubles.

Turbine types follow the site: Francis for medium head, Pelton wheels for high mountain drops, Kaplan propellers for low river dams. A generator converts spin into electricity at grid frequency.

Pumped storage reverses the machine, pumping water uphill cheaply at night and generating at peak. Capacity factors range from about 40 percent for run of river schemes to above 50 for storage dams, and modern units exceed 90 percent efficiency..