Hydro power

The power of moving water has been used since ancient times to mill flour, pump water, move grindstones and sawmills, and help drive simple machinery. But it was only towards the end of the 19th century that the energy generated by flowing water was first harnessed to produce electricity.

A hydroelectric system involves putting up a dam to store vast quantities of water in a reservoir. The power of the “falling” water, which is released on a regular basis, is used to turn the blades of a turbine. The turbine in turn drives a generator, which produces electricity.

Hydroelectric power plants work day and night and can generate electricity depending on the demand. In a pumped-storage facility, a special type of hydro power plant which contains two reservoirs, the plant can pump water back to the upper reservoir using a reversible turbine. This is done in off-peak hours. By pumping water back to the upper reservoir, the plant has more water to generate electricity during periods of peak consumption.

Water-rich mountainous countries such as Norway can meet almost their entire electricity needs from hydro power. In Alpine nations such as Switzerland and Austria, it accounts for almost two thirds of electricity generation. By contrast, hydro power makes up just 3.5 percent of the energy mix in Germany, according to the environment ministry. Hydroelectric power supplies a sixth of the world's electricity demands.

Mega hydroelectric projects such as the Three Gorges dam in China are expected to produce up to 18 gigawatts of energy. In addition to big hydro plants and dams, small-scale hydroelectric plants with capacities in the kilowatt range play a crucial role in providing electricity to remote mountainous regions.

Author: Antonia Roetger/ Helmholtz Society (sp)
Editor: Jennifer Abramsohn