GEO-NET Umweltconsulting GmbH

Bigger, higher, stronger - what applies to sport also applies to the wind industry. With greater hub heights, larger rotors and more powerful generators, windturbines are becoming ever more efficient, windpower ever cheaper, and thus windenergy is making an increasingly important contribution to climateprotection and security of energysupply. To support this progress and reduce risk and uncertainties in the energy yield assessment for such projects GEO-NET now installed a new 200 m metmast for LiDAR verification and research in North Germany.

The relevant standard MEASNET prescribe a verification of remote sensing devices (RSD) such as LiDAR and SoDAR devices at least at three quarters of the planned hub height. However, uncertainties can be further reduced by a higher measurement, which of course must also be verified at the corresponding height. In addition, more data is obtained over a larger part of the rotor circle - which is particularly interesting for large rotors, where the wind shear results in quite different wind conditions between the upper and lower rotor ends, causing additional loads on the rotor blades, bearings, shaft etc.

The devices verified by GEO-NET can be used for bankable wind measurement campaigns, energy yield assessments, AEP-reports, FESR etc., and help to reduce uncertainties, thus making it possible to finance certain projects in the first place. GEO-NET is internationally accredited for all these services and keeps this accreditation up to date.

GEO-NET installed the first two 160 m met masts in SouthAfrica for wind and energy yield assessments for their customer. These are the highest wind measuring masts in South Africa for wind farm development.

Technology in the wind power business is advancing rapidly. Today’s turbines boast hub heights of up to 160 m and more, which was hard to imagine in the early days of wind power. But the higher the distance between met mast and turbine hub height, the higher the uncertainties in the energy yield assessment in the development phase.

Higher uncertainties lead to higher risk, and that is what investors, lenders and banks want to avoid. Thus, these projects are usually financed on the P75 or even P90 value of the energy yield (which is the value of the energy yield which will be matched or exceeded with a 75 % or 90 % probability).

A higher uncertainty leads to a lower P75 / P90 level of the energy yield – and in low wind conditions this could be the end of a project, even if the average wind speed (P50) would be sufficient. For two of such projects, far away from the stormy coasts of the Western and Northern Cape, GEO-NET installed the two 160 m masts.