Posts Tagged ‘Wind power’

Sodar’s Overview

January 3, 2012

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Sodar (Sonic Detection And Ranging) is device for measuring remotely wind profiles from the ground by projecting sound waves. By sending an acoustic pulse away at sound velocity, it interacts with density fluctuations in the air and the frequency of backscattered signal is interpreted. This is possible due to the Doppler Effect that means frequencies between the sent signal and the backscattered one are different. Hence, wind speed can be interpreted.  Hence, wind profiles (wind speed and wind directions in function of height) at that place can be obtained.

Reliable Sodar ranges are typically around several hundred meters and basically, it depends on ambient noises and atmospheric humidity. First Sodars were developed in late 1950’s, but the first commercial ones appeared in 70’s in California (AeroVironment, Inc). Prizes are around 50.000 USD per unit.

Advantages:

– Higher altitudes than met masts.

– Cheap and easy-to-install.

– Accurate at appropriated atmospheric conditions.

Disadvantages:

– Not accurate under rainy, noisy, and low humidity conditions (sound is attenuated more rapidly in dry air).

– Data are obtained by averaging the received data. Hence, wind speed and wind direction standards are not reliable.

– Not appropriate when high obstacles are nearby (buildings, trees, towers).

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