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How does hydropower work?

Most hydroelectric stations use either the natural drop of a river, such as a waterfall or rapids, or a dam is built across a river to raise the water level, and provide the drop needed to create a driving force.

Water at the higher level is collected in the reservoir or forebay. It flows through the station's intake into a pipe, called a penstock, which carries it down to a turbine. The turbine is a type of water wheel that is connected to a generator. As the water flows down the penstock the water pressure increases. It is this pressure and flow that causes the turbine to revolve which in turn spins a generator.

Inside the generator are large electromagnets attached to a rotor that is located within a coil of copper wires called the stator. As the generator rotor spins the magnets, a flow of electrons is created in the coils of the stator. This flow of electrons generates electricity that can be stepped up in voltage through the station’s transformers and sent across transmissions lines. The falling water, having served its purpose, exits the generating station through the tailrace, where it rejoins the main stream of the river.

There are four main types of hydropower facilities:

  1. Reservoir Storage: These systems use reservoirs to store water during periods of high flow, such as the spring to be used to generate electricity during low flow periods such as the winter or summer.
  2. Run-of-River: A run-of-river facility uses the natural flows in the river for generation. Therefore, all flow in the river is either passed through the plant, or partially released around the plant if the flow exceeds the capacity of the plant.
  3. Pumped Storage: Pumped storage facilities pump water from a lower reservoir to a higher reservoir during off-peak periods. This water is then released from the upper reservoir through the plant to generate electricity during peak periods.
  4. Kinetic Hydro: Kinetic waterpower systems are an emerging technology. Turbines are placed in the river and use only the existing water flow to generate electricity.