On the theory of SODAR measurement techniques (final reporting on WP1, EU WISE project NNE5-2001-297)

The need for alternative means to measure the wind speed for wind energy purposes has increased withthe increase of the size of wind turbines. The cost and the technical difficulties for performing windspeed measurements has also increased with the size of the wind turbines, since it is demanded that thewind speed has to be measured at the rotor center of the turbine and the size of both the rotor and thehub height have grown following the increase in the size of the wind turbines. The SODAR (SOundDetection And Ranging) is an alternative to the use of cup anemometers and offers the possibility ofmeasuring both the wind speed distribution with height and the wind direction.At the same time the SODAR presents a number of serious drawbacks such as the low number ofmeasurements per time period, the dependence of the ability to measure on the atmospheric conditionsand the difficulty of measuring at higher wind speeds due to either background noise or the neutralcondition of the atmosphere.Within the WISE project (EU project number NNE5-2001-297), a number of work packages have beendefined in order to deal with the SODAR. The present report is the result of the work package 1. Withinthis package the objective has been to present and achieve the following:- An accurate theoretic model that describes all the relevant aspects of the interaction of the soundbeam with the atmosphere in the level of detail needed for wind energy applications.- Understanding of dependence of SODAR performance on hard- and software configuration.- Quantification of principal difference between SODAR wind measurement and wind speedmeasurements with cup anemometers with regard to power performance measurements.The work associated to the above is described in the work program as follows:a) Draw up an accurate model of the theoretic background of the SODAR. The necessary depth isreached when the influences of various variables in the model on the accuracy of the measurementhave been assessed.b) Describe the general algorithm SODAR uses for sending the beam and measuring the reflections.Describe the influence of various settings on the working of the algorithm.c) Using the data set from work package two analyse the differences between point measurements andprofile measurements.All the above issues are addressed in the following repor