The current standard for wind measurements in wind energy is based on data obtained from cup anemometers. However, theses standard anemometers suffer from so-called over-speeding under turbulent wind conditions as always present in atmospheric flow. Additionally, moving parts of the sensor lead to wear of bearings and thus yield a loss of calibration in time.
Motivated by these issues, the sphere anemometer was developed to serve as a robust alternative sensor without wearing parts.
The sphere anemometer makes use of the velocity-dependent drag force acting on a sphere, which is attached to the tip of a flexible tube. The deflection of the sphere can be measured by means of a highly resolving light pointer and the prevailing wind speed and direction can be obtained via calibration.
The small displacements and the low moment of inertia of the sphere-tube-systems allows for a higher spatial and temporal resolution compared to cup anemometers.
The research project "Weiterentwicklung eines Kugelanemometers fur die Verwendung in der Windenergie" aims at the optimization of the current sphere anemometer prototype. Data obtained from two offshore sites in the German Wadden Sea will be compared to data of standard anemometers, namely cup anemometer and ultra-sonic anemometer. The comparison shall give evidence about the performance of the new sphere anemometer and thus give an estimate of the opportunities for wind energy.
|Fig. 1: Sphere anemometer
|Fig. 2:Velocity measurement done with different anemometer types