GEO-NET operates a 200 m wind measurement mast for the performance verification of LiDAR and SoDAR devices at eight different heights from 60 m to 200 m near Hannover since September 2022. The site is particularly suitable for verification due to its location, as it is almost free of significant obstacles and allows representative verification even for onshore sites and the large hub heights of current wind turbines. The good wind conditions ensure that the verification can be carried out quickly.
With hub height, rotor diameter and turbine capacity, of course, the challenges also grow, and not only during the construction of the turbines or their operation, but already in the early planning phase - for example with yield assessments and wind measurements. To keep uncertainties as low as possible, a yield assessment needs reference data on wind speed as close as possible to the planned hub height. Many existing turbines are now too low compared to the current turbine generations, so that a wind measurement becomes necessary to gain reliable reference data. For cost reasons, LiDAR devices are now often used for this purpose, which performance must be in turn verified on a reference mast - and also as close as possible to the planned hub height. And it is precisely for this purpose that the wind experts from GEO-NET have now installed a 200 m high reference wind measuring mast close to Hanover for the verification of LiDAR and SoDAR.
The location of GEO-NET offers numerous advantages: It is centrally located, easy to reach via A2, A7 and A27, and offers good wind conditions. Thus, GEO-NET can perform the verification faster and the verified devices can start earlier with the actual measurement. The site has a free flow in the relevant sectors and, in contrast to coastal sites, is more representative of onshore sites, as wind shear, turbulence and precipitation in particular are comparable, which in turn reduces uncertainties in the yield assessment. The reference mast is equipped with special instrumentation for measuring turbulence and meteorological parameters in order to use the measurement data for various research and development projects in the fields of wind energy, meteorology and climatology. In these areas, GEO-NET is already working closely and successfully with Leibniz Universität Hannover and Fraunhofer IWES in the joint projects EWiNo, SUnDAY and ADLER.
The relevant standards TR6 and MEASNET prescribe measurement and verification 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, as here the wind shear ensures quite different wind conditions and thus additional loads between the upper and lower rotor ends.
GEO-NET is internationally accredited for measurements and verifications of LiDAR and SoDAR devices to IEC 61400-50-2 and keeps this accreditation up to date. The devices verified by GEO-NET can be used for bankable wind measurement campaigns and yield assessments and help to reduce uncertainties, thus making it possible to finance certain projects in the first place. In this way, GEO-NET is already making an important contribution to climate protection and security of supply in the project phase.
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