Remote Sensing for Wind Resource Measurement
The wind industry, to date, has largely studied wind patterns and turbine performance using traditional fixed masts; these raise issues such as the need for site permitting, working at height, and increased uncertainty in data due to complex sites and inadequate mast heights. The highest mast currently available on the market reaches 80 metres. The hub height of turbines is becoming greater and greater, but for now wind data from altitudes higher than the masts can reach generally has to be estimated. Remote sensing methods, such as sodar and laser anemometry (lidar), offer a means of obtaining accurate wind profiles for wind resource assessment at greater heights.
{access view=!registered}Only logged in users can view the full text of the article.{/access}{access view=registered}Currently there are several lidar systems on the market. In our November 2004 issue we published the article 'Wind speed at light speed: laser radar', written by QinetiQ (a UK research and development laboratory), which described the principle by which lidar measures velocity. At that time the ‘ZephIR' system was still at an early stage of development. In March 2007, Natural Power exclusively licensed the technology from QinetiQ to bring ZephIR to the global market and commence serial production. In this issue we publish a follow-up story on the ZephIR which reports the results of the evaluation programme (see page 7).
Leosphere from France have developed a similar system called 'Windcube'. It has been co-developed with the French Aerospace Research Agency (ONERA). Because the Windcube uses a pulsed laser source the resolution and accuracy remain the same at any height, with the added benefit of simultaneous measurement. In a future issue we will publish a more detailed technical article about the Windcube.
Another system is the Vindicator from Optical Air Data Systems (OADS). The Vindicator incorporates fibre-optic laser technology adapted from telecommunications and defence industry programmes.
As well as lidar, sonar has also been used for wind measurements, but it could not be deployed in some weather conditions and therefore had a more limited range of applications. Second Wind recently announced the ‘Triton' system, and company officials said that they had reinvented sodar for wind profiling. The Triton sonic wind profiler is designed to address the common challenges that have limited the use of sodar for wind resource assessment. It captures accurate wind data at heights of up to 200 metres, in any weather, at any location, without needing constant supervision. Readings are delivered via satellite and look like anemometry results, with no expert analysis required to understand the data. The Triton product has been designed specifically for wind profiling by users who are not sodar experts. It is expected that the first Triton will be commercially available in September 2007. We will follow this technology as well, of course, and hope to publish more about it in a future issue.
Enjoy reading,
Floris Siteur
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