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Title:
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Comparative measurements of SODAR systems : Correlation with meteorological masts for onshore and offshore conditions and further measurements to compare SODARs (final draft)
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Author(s):
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Published by:
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Publication date:
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ECN
Wind Energy
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1-3-2003
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ECN report number:
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Document type:
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ECN-C--02-045
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ECN publication
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Number of pages:
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Full text:
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180
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Download PDF
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Abstract:
ECN performed measurements at onshore and offshore locations to validatea MiniSODAR measurement system. A number of different measurements were
done to compare the two SODARs. These were hardware test, background
noise and vibration measurements. Also a comparison with a meteorology
tower has been performed.
The onshore SODAR measurements are compared against a 213-metres height
meteorological mast owned by the KNMI, located at Cabauw in the Netherlands.
Offshore SODAR measurements are compared against a 10-metres meteorological
mast owned by KNMI at the station Noordwijk, about 9 km off the coast
at Noordwijk, in the Dutch part of the North Sea.
Onshore comparison is performed at different height levels and using
different SODAR settings. Two different models of the MiniSODAR were
used for this purpose. Offshore comparison is done at 10 metres height
only (due to limitations of the available tower). A MiniSODAR model,
similar to one of the models used for onshore measurements, was used
offshore.
The aim of the measurements is:
- To gain knowledge of parameters that influence the performance
of
the MiniSODAR;
- To analyse the MiniSODAR?s performance under influence of external
noise and vibrations;
- To check the operation of the SODAR by comparing calibration measurements.
Correlations for measurements using a meteorological mast and a SODAR
system have been derived for onshore and offshore applications. A correlation
between onshore and offshore measurements using SODAR techniques is
also derived.
The results of the measurements offshore are that it is important to
determine the position of the SODAR by measurements and to perform regular
maintenance (at least once every three months) as severe degradation
of equipment has been seen. With regards to the onshore measurements
the measurement results show that the mean difference between SODAR
and the anemometers on the mast is 0.84 m/s (at 80 metres) and 1.73
m/s (at 80 metres) for the same SODAR with different settings. A SODAR
of a different model showed a mean deviation of 1.58 m/s. The conclusion
is that the SODAR performance is heavily influenced by the SODAR settings.
At the moment off-the-shelf SODAR does not perform well enough to be
used for wind energy purposes.
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