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LiDAR Technology |
Wind sensors in a new light Our wind sensor measures the wind using laser light. The principle is known as LIDAR and was invented back in the 1970s. But we have fine-tuned the technology and replaced expensive light sources with a less expensive and much more affordable laser. We have filed a patent for the use of LIDAR. The result is a wind sensor unlike any other, which is well worth putting on a wind turbine.
Researchers in the wind industry envision tomorrow’s wind turbines as “smart machines” capable of maximizing power production and minimizing dynamic load according to changes in the oncoming wind. This requires that each turbine is equipped with an instrument that can obtain accurate and timely knowledge of the wind inflow. Wind LIDARs, which use laser beams to remotely probe the flow of aerosols (i.e. wind velocity) are the right sensor for this task. In the wind energy sector, laser-based wind sensors or wind LIDARs have become popular alternative to conventional anemometry instruments (fixed sensors like cup anemometers, wind direction vanes and sonic anemometers). The successful introduction of wind LIDARs can be attributed to their ability to accurately measure wind speed and direction, remotely. A number of interesting research and engineering applications are now being explored due to the increased commercial availability of this remote sensing technology. A wind LIDAR relies on the Doppler effect – a slight change in frequency of the backscattered light – caused by moving air-borne particles passing through the laser beam’s focus in the atmosphere. The Doppler frequency shift gives direct information of the wind speed component along the line-of-sight of the beam. Due to ultra-low power levels of typical backscatter (in the order of 1 part in ~100 billion of the transmitted laser power) associated with the lower atmospheric boundary layer, a very sensitive optical detection scheme and a relatively high power, narrow-linewidth laser has to be employed. The most widely used scheme to extract Doppler shift information is the so-called “optical heterodyne detection”. For commercial wind LIDARs, stringent eye-safety requirements have led to the preference for lasers operating near the 1550 nm wavelength. A review of the existing wind LIDAR products will show that they employ expensive fiber laser and/or fiber amplifier technologies; to achieve the required laser output power and linewidth at 1550 nm operation. A previous study has found that up to 25% of the total system cost can be attributed to such laser source alone. Windar Photonics aim is to deliver LIDAR systems for wind velocity sensing using cheaper and compact lasers at 1550 nm and novel methods developed and patented during the past three years. For more information about the application of LiDAR technology in relation to the Windar Photonics' products, please visit our white paper section. |
Proof of conceptBack in 2010, the LIDAR system underwent a proof-of-concept verification test. This test was conducted at a distance of 80 metres, with the LIDAR system measuring towards the cup anemometer.
Power versus yawIt is a generally accepted fact that most wind turbines suffer from yaw misalignment to a greater or lesser extent. Various tests – including the Risø test below – have verified that there is a relatively large power reduction factor for each degree of yaw misalignment on a wind turbine.
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Windar Photonics A/S | Helgeshøj Alle 16-18 | DK-2630 Taastrup | Denmark | Copyright © 2012 Windar Photonics A/S | All rights reserved.
