Basics of Renewable Energy Supply - Renewable Energy: Technology, Economics and Environment - page 58

Instruments to measure the mean value are
− Cup anemometers, anemometers which either measure the mean wind velocity
over a few seconds (approximately 10 to 30 s) or the wind path, i.e. the product
of the mean wind velocity and the time. Cup anemometers are currently the
most widely used measuring instruments for 10-minute mean values as well as
the 2-second-gust);
− Impeller anemometers, offering principally the same features as the cup ane-
mometers.
Wind distribution. The measuring instruments outlined above are in use world-
wide. The measured wind speeds can be analysed and the annual mean value can
be calculated. If the yearly mean wind velocity is averaged over various years,
areas of similar wind speeds can be identified. Fig. 2.27 shows these values on a
worldwide scale referring to 10 m above ground.
< 2
2 - 3
3 - 4
4 - 5
> 5
Values in m/s
Fig. 2.27 Distribution of yearly annual mean values of the wind speed for 10 m above
ground worldwide (data according to /2-11/)
According to that high average wind velocities are given especially in coastal
regions; this is for example the case at the north coast of Australia, the Atlantic
coast in Patagonia/Argentina, and the west coast of Canada. But also some moun-
tain areas like the west side of the Andes in e.g. Peru or Bolivia as well as some
plains (like the Midwest of the USA) are characterised by considerable wind
speeds. When interpreting such a wind speed distribution on a worldwide scale,
we need to consider that the data bases for some areas are rather poor.
If, for instance, the average mean wind velocity at 50 m above ground meas-
ured at different sites throughout Germany is applied to the entire area of Ger-
many we arrive at the conditions outlined in Fig. 2.28. According to this, the
North Sea is characterised by an annual mean wind velocity of over 8 m/s far
before the coastline. On the East and West Frisian Islands and the mud flats, the
long-term mean air-flow speed varies between 7 and 8 m/s and above. At the