The most widely accepted method of measuring the wind at a site has been to use wind sensors mounted on a met mast/tower, recorded by a wind data logger. For best results, the tower should be at least as tall as the hub of a likely wind turbine, says the firm: “This can create a challenge as wind turbines can be 80 metres or above at hub height, while the most popular style of meteorological towers used for prospecting – tilt-up temporary masts – are 50 or 60 metres in height.”

The solution in such instances, say sources at SecondWind, is to use remote sensing technologies, such as its Triton Sonic Wind Profiler, which can measure wind at higher heights. More and more companies are now providing these technologies. “In addition to complete wind resource assessment, remote sensing systems can be used for wind prospecting,” the company adds. “The advantage of remote sensing is the substitution of measured wind data for modelled wind data.”

GL Garrad Hassan agrees. “Remote sensing measurement techniques enable measurements to hub height and beyond.” The company says it makes significant use of “value-adding alternative technologies” and this includes resource measurement using sodar and lidar. Its experts, it adds, have been involved in the testing of remote sensors since their market inception and “are therefore well placed to advise on their use as part of a wind monitoring programme”.

In fact, it is fast becoming standard industry practice to use measured data from validated remote sensing technologies in combination with met tower measurements, something viewed as particularly useful when trying to secure financing for wind farms.

In November, for example, developer Continental Wind Partners (CWP) made use of the Triton Sonic Wind Profiler as part of its standard wind resource assessment practice. With a fleet of 8 Tritons, CWP is using the technology to “expedite wind farm development, reduce project uncertainty and streamline project financing” at sites in five Eastern European countries.

In addition to Eastern Europe, CWP is an investment partner in several projects in Australia with Wind Prospect and also plans to use the technology there. “Although met tower data remains a key part, remote sensing is becoming more and more necessary to reduce uncertainty by measuring hub height wind conditions,” says Konrad Gorzkowski, wind & site engineer at CWP.

The company has already accumulated nearly 100,000 hours of Triton data in Central and Eastern Europe. At the earliest phase of the development cycle, Tritons are deployed for wind prospecting – taking an initial measurement of a site's resources to determine whether the site qualifies for a lengthier study with meteorological towers.

On sites with existing met towers, CWP has deployed the system at several locations around the site to better map the available wind resources, an approach known as micro-siting. “Triton always correlates well to the met tower measurements and provides valuable information on each site's profile,” says Maciej Baginski, wind measurement and GIS specialist at PS Wind Management, CWP's Poland-based development group.