How does electricity produce water

Hydropower

Hydropower: advantages and disadvantages | Hydropower plants | Hydropower in Germany

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Hydropower - how electricity is generated from water

By definition, hydropower is the energy contained in flowing or stored water.1 This kinetic or potential energy can be used to generate electricity. Most of the electricity from hydropower is supplied by large power plants, while small hydropower plants only contribute a small proportion.2 The conversion of hydropower into usable energy takes place via turbines.3 Hydro energy accounts for around 15 percent of global electricity generation, and in Latin America more than two thirds of the electricity demand is met by hydropower.4

Advantages and disadvantages of hydropower

A decisive advantage of hydropower is that electricity almost equates to CO2-free and therefore climate-friendly can be produced. However, there are also disadvantages associated with the use of hydro energy. Whether hydropower can be used depends on the location; mountainous regions are particularly favorable. Major interventions in the landscape are often necessary in order to build hydropower plants. The creation of reservoirs can generate strong CO2- and cause methane emissions when land areas with high levels of carbon in the soil are flooded.

In the case of river hydropower plants, there is a risk of negative effects on the flora and fauna of the flowing water, and fish in particular are at risk. If water is taken from the river at one point to generate electricity and fed back into it at a point further downstream, there is a possibility that the required residual water volume in this area will not be exceeded. In addition to flushing reservoirs in storage power plants, they are problematic as they are used to remove deposits such as digested sludge from the reservoir and must be carefully planned so as not to damage the environment.5

Interventions in the landscape to make hydropower usable can have serious ecological consequences. With the construction of dams, the biological continuity of rivers is broken, and the habitat below the dam is also changing due to reduced water runoff. In addition, the passage of turbine systems for fish and other animals harbors a risk, if several hydropower plants follow one another along a river, entire populations can be endangered.6

Most of the rivers and reservoirs are used to generate electricity from hydropower, but the sea is also a potential source of energy. Both the tidal range and the energy content of currents and waves are suitable for generating electricity. The advantage of hydropower and ocean energy is that they are available more consistently than wind and solar energy and that reliable forecasts are possible.7

Types of hydropower plants

There are different types of hydropower plants, which are adapted to the respective location. A basic distinction can be made between run-of-river power plants and storage power plants. Run-of-river power plants can be found on canals, rivers and streams, which are then often dammed by a weir to increase the potentially usable energy. Storage power plants use the water from reservoirs to generate energy, a special form is the so-called pumped storage power plant.8

A run-of-river power plant generates electricity from the flow of a river, which requires relatively large amounts of water and a slight gradient. The cost-effectiveness of the systems is increased by building locks.9 If a river is dammed by a weir with turbines to generate electricity, the water can fall up to 15 meters.10 In run-of-river power plants, no water is stored, it has to be used directly. This results in a fairly even generation of electricity to cover the base load, which can, however, be subject to seasonal fluctuations, for example due to meltwater.11

Storage power plants generate electricity with the help of a large difference in height, the quantities of water required for this are rather small.12 The hydropower can be used both to cover the base load and for peak load operation, since dams and lakes have a high storage capacity. Storage power plants are available in different designs: The dam power plant uses turbines at the foot of the dam to generate electricity. In mountain storage power plants, mountain lakes are connected to power plants in the valley via penstocks. The pumped storage power plant is a special form because it is not fed by natural water resources, but by water that is pumped up from a reservoir below.13

At the sea, tidal power plants are mainly used to generate electricity from hydropower. But there are also other ways of harnessing ocean energy. Ocean current power plants and ship mills generate electricity from the current, wave power plants from the ocean waves - so they not only use water power, but indirectly also wind energy.14

Use of hydro energy in Germany

The history of hydropower goes back centuries; in pre-industrial times, mills and sawmills were operated with the help of water. Nowadays, electricity is mainly generated from hydro energy in Germany. The federal states in the south have the best prerequisites for the use of hydropower, because the gradient in the foothills of the Alps is favorable for the use of hydropower plants. The large plants in Germany include around 80 percent run-of-river power plants and 20 percent storage power plants.15 A large part of the hydropower is generated on the rivers Inn, Danube, Rhine, Isar, Lech, Main, Mosel, Neckar and Iller. In total there are more than 400 large hydropower plants and thousands of small hydropower plants in Germany. According to an analysis by the Federal Environment Ministry, 80 percent of the given potential for generating electricity from hydropower is already being used.16