Hydropower is one of the most long-established source of energy used to provide mechanical and electrical energy. Hydropower relies fully on the water cycle, which is renewed by the energy of the sun; therefore, it is a renewable energy source. The first well-known use of hydropower was to generate mechanical energy for grinding grain, for instance. Nowadays, hydro energy is mainly used to generate electricity. In a hydropower plant, the force (mechanical energy) of the moving water will rotate the rotors of the turbine that is connected to a generator. When the turbine spins, the generator connected to it will then produce electricity.
There are 2 main types of conventional hydroelectric facilities:
- Dam: the water accumulates in reservoirs created by dams. Dams are major barriers built to raise the water level and control its flow. In this sort of facility, the elevation of the water created by the dam generates gravitational force that will rotate the turbine when the water is released. Some storage systems may also contain a lower reservoir that can pump water to the upper storage during peak periods. This kind of facility is called pumped-storage hydropower facility.
- Run of river: this type of facility also uses turbines and generators, but instead of building a dam to reserve water, it relies on the natural force of the river to turn the turbine, redirecting only a portion of the water to the turbines.