Green Energy

Biography

Biography: Byeong Hee Chang

Abstract

Generally, wind turbine anemometers are installed on the nacelle behind wind turbine. So, they are in the wind turbine wake flow and the measured wind speed and direction are influenced by the wake and different from the freestream’s. Recently, the ROMO Wind developed a spinner anemometer of 3 single-axis ultrasonic sensors installed on the spinner for measuring undistured wind speed and direction. In this study, it was checked if a 3-axis ultrasonic anemometer could replace the 3 single-axis ultrasonic sensors as a spinner anemometer. The technique is based on the coordinate transform from the rotating sensor axis to the fixed coordinate for measuring wind speed and direction. Its validation tests were done with a roll-rotating test stand in the Korea Aerospace Reseach Institute (KARI) Low Speed Wind Tunnel. Even after the coordinate tranform, small rotating effect still remains in wind speed and direction. But, after one revolution of wind turbine, its mean values were converged to the test values within certain limits. The mean values were not much afftected by RPM (revolutions per minute), but affected by yaw angle and wind speed. The less yaw angle, the errors decrease. Upto 20° yaw angle, the errors of the mean values from the test values were less than double of the sensor own accuracy. At 10° yaw angle, the mean value errors were 2.0% RMS (root mean square) in wind speed and 1.7° in wind direction. But, in high yaw angle such as 60° or above, the mean value errors were drastically increased. So, in real application, if initial yaw angle is too large for this measuring technique, it could be reduced with a conventional nacell anemometer to within 20° and then it could be aligned more preciously with this technique including 3-axis ultrasonic anemometer installed on the spinner. This concept will be applied and checked to some operating wind turbines in real field in near future.