People have always used renewable energy sources, such as burning biomass to heat food, wind to propel ships, or water to power mills. Today, renewables are important for the transition to clean and sustainable energy.

Renewable sources are clean, safe and easy to operate, but they have also low output density and a strong dependence on weather, location and season, which places certain demands on the electricity production from them.

Water energy is constantly renewed through the natural cycle and is used in hydroelectric power plants to drive turbines. Due to the diversity of river flows, there are many types of power plants, dams and turbines.

Water turbines are the main parts of hydroelectric power plants — an ecological renewable resource. Turbines have gone through a long period of development and today three main types are in use: the Francis, Kaplan, and Pelton turbines.

Mankind has used the wind to propel ships, drive irrigation or grind grain since ancient times. Many types of turbines are used to convert wind energy into electricity. The most successful is horizontal axis lift turbine.

The sun is a giant sphere of hot hydrogen at the centre of our solar system. Inside it, thermonuclear fusion takes place, releasing huge amounts of energy.

Solar energy can be used to generate electricity in a number of ways. Concentrating power plants focus the sun’s heat at a single point, driving a steam turbine, while photovoltaics convert the sun’s rays into electricity.