A hydropower plant is made up with a collection of the necessary installations to transform the potential energy of a watercourse – as a result of the level difference between to points – into available electric power.
Depending on the location of the installation, they can be classified into three large groups:
Run-of-the-river power station: these are exploitations that capture part of the streamflow by means of an inlet at a water wheel; the waterflow is led to the station to further go through a turbine and it is then returned to the river.
Stations at the foot of the dam: these facilities take advantage of the difference in height of the very dam, which can regulate the outgoing stream flow rate passing through the turbines, depending on the uses of the dam (hydro, irrigation or water supply).
Station at irrigation channels or for water supply: these exploitations make use of the difference in height between the channel (or pipe) through an inlet in the channel, a penstock that takes the water up to the turbine to further return it to the channel.
The concept of a mini-hydro is a hydroelectric plant whose installed capacity is up to or less than 10 MW.