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The sodar as a screening instrument: Comparison with cup anemometer measurementsand long-term correction studies
2010 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The sodar as a screening instrument - Comparison with cup anemometer measurements

and long-term correction studies

Anders Nilsson

A site assessment including wind measurements is of major importance when planning

a wind farm. Small differences in wind speed can determine if a project will be economically

viable since the power in the wind is proportional to the cube of the wind

speed. It is also important to have knowledge about the long-term wind climate since

the technical lifetime of a wind turbine is about 20 - 25 years.

Traditionally, masts mounted with cup anemometers and wind wanes have been used

for wind measurements during site assessments. However, an instrument called sodar

which measures the wind based on sound waves has entered the market some years ago

and offers some advantages in terms of e.g. mobility compared to the mast equipped

with cup anemometers and wind vanes. Since the sodar is a relatively new instrument in

the wind energy business, it is important to gain knowledge on how the instrument

operates and its performance. To do that, sodar measurements have been compared to

wind measurements performed by a cup anemometer and a wind vane.

In order to estimate the long-term wind climate at a site, a long-term calculation is

performed based on short-term measurements from the site and a long-term reference

wind data. At least one year of wind measurements at the site are needed in order to

obtain a valid result from the calculation. However, for an early evaluation of a site it is

desirable to measure the wind for a shorter period of time. Therefore, it has been studied

in this thesis how the result of the long-term correction depends on the length of the site

measurement period. The seasonal impact on the results has also been studied to

distinguish what season is the most suitable for short measurements.

According to the results, the measurements performed by the sodar used in this study

are as valid as those performed by the cup anemometer and the wind vane. Considering

the advantages with the sodar compared to the mast equipped with cup anemometers

and wind vanes, the sodar is the preferable choice.

The results from the long-term correction calculations improve most rapidly during the

first four months of measurements. It is therefore important to measure the wind for at

least four months. Best results are obtained when the measurements are performed

during the spring and the autumn compared to the summer and the winter.

Place, publisher, year, edition, pages
2010.
Series
UPTEC W, ISSN 1401-5765 ; 10 010
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-350593OAI: oai:DiVA.org:uu-350593DiVA, id: diva2:1205482
Educational program
Master Programme in Environmental and Water Engineering
Supervisors
Examiners
Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2018-05-14Bibliographically approved

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