Hydro power stations convert the potential energy in water into electrical energy. The water is passed through a turbine, causing it to rotate. This converts the water’s potential energy into mechanical energy. The turbine drives a generator that turns the mechanical energy into electrical energy.
The water flow and the height of the head of water determine how much electricity can be produced by the power station.
Hydro power is the only renewable energy source that is controllable. Electricity itself cannot be stored in large quantities, but the water can. Dams create reservoirs where water can be stored during periods when demand for electricity is lower than potential production. Whenever demand rises, the water can then be used by the power station. This system ensures that the Swedish energy market is always in equilibrium.