Britannica Sources used in this answer

How do hydroelectric power plants turn falling water into electricity?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Study how a series of gears in a waterwheel translates a stream's energy to a millstone — energy conversion Before the Industrial Revolution, power came from three main sources: humans, draft animals, and water.
The ingenuity people used in harnessing waterpower can be seen in this medieval-style mill. The waterwheel is turned by a stream and is connected to a shaft that leads into the building. At the other end of the shaft is a gear. The connection of a series of gears translates the power from the stream to a shaft that drives a millstone, which grinds flour from grain.
(30 sec; 1.84MB)

Hydroelectric power plants generate electricity by converting the potential energy of water stored at a higher elevation into mechanical energy and, ultimately, into electricity.1

The process follows these key steps:

Collection and Transport: Water is stored behind a dam to create a "head," which is the vertical distance between the water's surface and the turbines located below. The water is directed downward through large pipes or tunnels known as penstocks.1
Energy Conversion: As the water flows down, it gains velocity. This falling water strikes the blades of a turbine, causing it to rotate. In impulse turbines, the water's head is first converted into kinetic energy via a nozzle before striking the turbine buckets.12
Generation: The rotating turbine is connected to a generator, which converts the mechanical energy of the spinning turbine into electrical energy.1
Transmission: Transformers then increase the voltage of the generated electricity to make it suitable for efficient long-distance transmission.1

This system is a reliable and renewable method of power generation, though it requires careful management of water flow to match varying electrical demands.1