Hydroelectric energy is the biggest renewable energy source on the planet, accounting for 18% of the world’s electricity output and 15% of national demand.
This source is based on two of the key properties of water: its potential energy and its kinetic energy.
The former is due to the phenomenon of the evaporation of the sea which, in the form of precipitation (rain, snow or hail), returns the water to the land instilling it with potential energy.
As the water moves from its source to its outflow its potential energy is transformed into kinetic energy. By exploiting height differences (whether natural or artificial) and channelling the water into special turbines, electricity is generated.
The dams or pipelines created to channel river and lake water have various forms but all share two characteristics that determine the capacity of the plant: volume and height difference.
There are dams that exploit significant height differences, as is the case in mountain areas, and others used for the large quantity of river water, made up of little barrages.
In order to develop levels of production in line with electricity demand, pump systems have been created that exploit the energy produced during the night when demand is lower. Water is pumped into tanks positioned above the turbines that are emptied when demand peaks so that the volume of water increases and, as a consequence, more electricity is produced.
In some cases hydroelectric energy is obtained by exploiting waves, tides and marine currents: in these cases we talk about tidal power.