Technology Status - NET Nowak Energie & Technologie AG

Turbine efficiency [%]
Turbines
100
75
50
25
During the 20 th century, the technology for harnessing water power
developed rapidly and turbine efficiencies close to 100% were achieved (see
Figure 4). Typically, larger turbines have higher efficiencies. For example,
efficiency is usually above 90% for turbines producing several hundred kW
or more, whereas the efficiency of a micro-hydropower turbine of 10 KW is
likely to be in the order of 60% to 80%.
Figure 4
Turbine Efficiency Over Time
0
1700 1750 1800 1850 1900 1950 2000 2050
Year
Sources: NET Ltd., Switzerland; World Energy Council (WEC).
Hydraulic turbines transform the water’s potential energy into mechanical
rotational energy by one or two basically different mechanisms:
● In reaction turbines water pressure applies force onto the face of the
runner blades, which decreases as it proceeds through the turbine. Reaction
turbines run full of water and generate hydrodynamic “lift” forces to propel
the runner blades. The most common types of reaction turbines are the
Francis and Kaplan turbines. Francis turbines are generally used in a head
range of 5 to 250 metres and can be designed with either a vertical or
horizontal shaft. Kaplan turbines are axial-flow reaction turbines, generally
used for low-heads.
2
SMALL HYDROPOWER
33