Depending on the type of the turbine, either potential or kinetic energy drives a turbine which is connected to a generator. This finally transforms the mechanical energy into electricity. If the water has passed the turbine it is channeled back into the natural course of the river or the equalising reservoir.
Modern “water wheels” such as the Francis or Pelton turbine can convert almost all of the water power into mechanical energy. They can attain 95 percent efficiency.
Wave Power Stations
The power of the seas can also be used to produce energy. A wave power station on the Scottish island of Islay has been providing electricity since 2001. The technology is actually quite simple: it is not the water which creates energy but the air which the water displaces.
The plant consists of a pipe-shaped reservoir which reaches under the surface of the water. The water level rises and falls with the waves and the air in the pipes is pushed upwards or sucked downwards. The air flow which this creates powers the Wells turbines, named after their inventor.
These turbines are remarkable in that they turn in the same direction whether there is an inflow or outflow of air. Optimum use of wave power is achieved as the turbo generator driven by the turbines also supplies electricity when the waves subside. In this way, the “Limpet 500” produces 500 kilowatts – enough for around 400 households.