renewables – Made in Germany

36 hydropower | industry overview
g Technology and
market overview
Hydroelectric power plants can reliably generate lowcost
electricity over a period of more than 100 years.
Their high degree of operational and supply security
allow fossil fuels costs to be circumvented over the
long term and provide a cost-effective way of securing
a basic source of electricity. Because some types of
hydroelectric power plants can store energy and
quickly supply electricity on demand, they contribute
significantly to grid stability. Hydroelectric power
plants reduce dependency on energy imports and
their associated risks and can form a basis for economic
development in regions without a comprehensive
energy supply. German companies have been
developing, installing and operating hydroelectric
power plants for over 100 years. This extensive experience
forms the basis for the excellent quality of German
products. Hydroelectric power plants designed
and produced by German companies can provide outputs
ranging from a few kilowatts up to several megawatts.
German technology is also being used in many
projects currently in planning all over the world.
Technologies and applications
There are three basic types of hydroelectric power
plant: the run-of-the-river, reservoir and pumped
storage power plants. The most common type used
worldwide is the run-of-the-river power plant, also
known as a river power plant, which uses a river’s flow
energy. These plants achieve an efficiency factor of
almost 94 % and are usually used to cover base load.
These plants’ output is determined by the river’s flow
velocity and water level. Some run-of-the river power
plants can also store water when energy demand is
low, using it as reserve water at times of increased
demand for electricity. One particular type of run-ofthe-river
power plant is the diversion hydropower
plant. Here, the water is dammed in a weir and redirected
through a separate intake canal to drive the turbines.
With a standard run-of-the-river power plant,
there is only a slight difference in altitude between
the upper and lower water levels, but a diversion
hydropower plant exploits the greater difference in
altitude (or higher head) created by the damming.
Schluchseewerk AG
g This pumped storage power plant in Häusern, Germany,
gene rates an annual average of around 120 million KWh
of electricity.
f Cette centrale de pompage hydro-électrique, située à
Häusern en Allemagne, produit environ 120 millions de
KWh d‘électricité en moyenne par an.
e Esta central hidroeléctrica combinada de bombeo y embalse
en Häusern, Alemania, produce un promedio anual de
alrededor de 120 millones de KWh de electricidad.
A reservoir power plant stores water in a natural
or artificial lake, from where it is fed via penstock into
the lower-lying power station. Since reservoir hydropower
plants can function independently of natural
water flows, they are ideally suited to balancing fluctuations
in regional and national electricity generation
and consumption. In contrast to the reservoir power
plant, a pumped storage power plant �p 36 uses
two water reservoirs to store water, with the greatest
possible difference in altitude between the upper and
lower reservoirs. If the amount of power generated
exceeds the amount required (e.g. at night), the
resulting overcapacity is used to pump water from
the lower reservoir into the upper reservoir, where
it is available for electricity generation in peak load
periods. The generator is driven by impulse turbines,
one type of which is the so-called Pelton turbine �p 38.
The type of turbine used depends on the flow rate
and head height (pressure) of the water. One of the
oldest types of turbine is the conventional Francis
turbine, which is used mainly by small hydropower
plants with low head heights and medium flow rates.
Archimedean screw turbines, which work on the
principle of the Archimedean screw, can also be used
in plants with low head heights and small outputs.