Hydropower was one of the first energy sources to be used by man. In ancient times, water mills were used to grind grain and to lift water. Mills were replaced with hydroelectric power plants in the middle of the 19th century.
Currently 90% of all electricity generated through renewable sources is hydroelectric.
How does it work?
Hydropower uses the power of rivers or waterfalls, transforming the water’s driving force into electricity. The weight and speed of the water power a turbine and convert hydraulic energy into mechanical energy. The turbine then powers an alternator (or a generator), converting mechanical energy into electrical energy.
What is it used for?
If the power plant is isolated and not connected to the power grid, electricity is used on-site. In most case, however, the energy is made available to the distribution grid to supply many users with electricity.
Large Hydropower Plants and Small Hydropower Plants
Present and future development of hydro power is based mainly on Small Hydropower Plants. There are two types of hydropower plants: Small Hydropower (SHP) Plants, with a power production capacity of less than 10 MW, and Large Hydropower Plants. Other types of SHP plants are called mini-hydropower plants (0.5 to 2 MW), micro-hydropower plants (0.02 to 0.5 MW) and pico-hydropower plants (capacity below 0.02 MW, or 20 kW). By way of comparison, some large dams have a capacity in excess than 10,000 MW!
Small hydropower plants are called “run-of-the-river power plants” because they do not stock water in a reservoir and only slightly affect the river. Their capacity depends on the season and changes in water levels. They can be set up in a wide variety of locations and they have major development potential, given that Europe cannot accommodate any more large hydropower plants. SHP plants can also maintain or create economic activity in rural areas, such as through jobs, taxes, fees and tourism.
Large dams adapt to natural constraints and fluctuations in electricity demand by using water reservoirs. Reservoirs can be natural lakes (for example Lake Victoria in Uganda) or can be artificially constructed with dams. The world’s biggest artificial reservoirs, such as the dams in Bratsk (Russia), Assouan (Egypt) and Kariba (Zimbabwe-Zambia) contain more than 160 billion cubic metres of water.
What are the impacts?
Small Hydropower Plants do not release any waste into the water and do not emit any atmospheric pollutants. By limiting changes to the flow water (for example, by not damming up or draining), plants of this type only have a minor impact on hydrology, biology, water quality, and do not disrupt the peace and quiet of the area for anyone in the vicinity.
Dams and artificial reservoirs however can have significant environmental impacts, such as preventing aquatic species from migrating, blocking sediment flows, causing the water quality to deteriorate, increase water-borne diseases and causing coastal erosion. It is therefore necessary to carefully monitor dam construction and maintenance.
It is estimated that every year a 1 MW hydropower plant avoids approximately 2500 tonnes of CO2 emission, that would otherwise by produced by standard combustion power plants.
