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Station 7: Water as a Source of Energy


The Importance of Water Power

Already in the preindustrial period, streaming water was used to power mills, hammermills and sawmills. Today, in modern day Germany, water is predominantly used to generate electricity. Owing to the topography of Germany however, only 3.4 % of its power is hydroelectric. In 2014, this amounted to 20.8 billion kilowatts of electricity. In terms of percentage of total energy produced through waterpower by nation, Norway is at the very top, with 99 % of its energy generated hydroelectrically. Hydroelectric power accounts for 16 % of power produced globally, ranking as the second highest source of renewal energy.

In Germany, the southern federal states possess the greatest potential for harnessing waterpower. Above all, the replacement, modernization and reactivation, as well as the reconstruction of pre-existing transverse structures play a primary role. Implementation must be accompanied by the consideration of all environmental concerns, in order to square increased energy performance with better aquatic ecology.

What Types of Hydroelectric Power Plants are there?

Hydroelectric power plants can be divided into the following types:


Hydropower Plants

Hydropower plants are the most common of hydroelectric power plants in Germany. This type of structure utilizes the currents of rivers and canals.

Fortifications dam the river and lead its water through a turbine, and down into the lower reaches of the river course. The currents cause the mechanical rotation of the turbine that in turn drives the generator, which converts the mechanical energy into electrical power. A transformer assists the process by boosting the voltage, and the electricity can be fed into the power grid.

Examples of hydropower plants can be found on the Danube, Iller, Lech, Inn, Rhine, Isar and Moselle rivers [Bundesministerium für Umwelt, Naturschutz, Bau und Reaktorsicherheit]


Storage Power Plants

Storage power plants utilize differences in altitude between a reservoir and the powerhouse, and capitalize on the storage capacities of mountain lakes and reservoirs. The lower-lying powerhouses are either connected underground to the reservoir, or connected above the ground with pipelines. Water is diverted and drives the turbines, creating electrical power with the help of a generator.

Altogether there are 59 pumped-storage plants in Germany, some of which have a power output of 240 MW [Bundesministerium für Umwelt, Naturschutz, Bau und Reaktorsicherheit].


Tidal Power Plant

The constant alternation of ebb and flow are used by tidal power plants to generate energy. In this type of power plant, the difference in water level is used to drive the production of energy. At high tide, water is impounded behind a dam, and at low tide the water is released. Its way of functioning is not all that different from that of a hydropower plant. The only major difference is that this type of power plant works in both directions. Indeed a two-way harnessing of tidal water flow is possible, however, turbines must be laid out for both directions [Bundesministerium für Umwelt, Naturschutz, Bau und Reaktorsicherheit o.J., o.S.].

St. Malo’s tidal power plant is an example of this type of hydroelectric power generation.


Pumped-Storage Power Plant

The method of generating power that is used in pumped-storage power plants is basically identical to the way in which power is made by a storage power plant. Turbines are driven by rushing water from a higher reservoir, and a generator enables the production of power. Subsequently, the water arrives in a lower-lying body of water, most of the time ordinary lakes or rivers.

Pumped-storage power plants can however pump the water from the lower basin back up into the reservoir. This serves above all reservoirs that have no natural inflow, as the water supply will not be exhausted. However, it should be noted that the pumping of water back into the reservoir requires more energy than it can later generate. Thus it is sensible that the process of pumping the water back be carried out at night, when demand for electricity is low and the prices are low. In this way, unused capacity does not go to waste.

The largest pumped-storage power plants can be found in the Black Forest, Lower Saxony, Hessen and the new eastern states of Germany [Bundesministerium für Umwelt, Naturschutz, Bau und Reaktorsicherheit ].


Figures: [Brennstoffzelle 2014]