Recommended Practice DNV-RP-0661 supports the wind industry for a cost effective and reliable measurement of turbulence intensity.
Wind farm project developers are often confronted with high costs for both wind speed and turbulence intensity (TI) measurements. These are often caused by high installation costs for met masts and long waiting periods for building permissions. At the same time light detection and ranging (lidar) systems are now commonly used in many wind energy applications as they provide a cost-efficient way of measuring horizontal wind speeds and directions in comparison to conventional anemometers and wind vanes on meteorological (met) masts.
To address this trend, DNV has issued a recommended practice (RP) for lidar measured turbulence intensity which has been developed together with industry partners in a Joint Industry Project.
This RP provides recommendations for the use of TI measured by ground-based vertical profiling lidars (GBL) in wind energy applications. The RP’s main purpose is to define acceptance criteria that provide clear limits when GBL TI is used as an alternative to a co-located cup or sonic anemometer TI. The acceptance criteria employ error metrics to represent the deviation between lidar and met mast (cup or sonic anemometry) TI in a meaningful way.
Applicable standards are currently based on the use of TI measurements from cup or sonic anemometry. This impedes the application of lidar-measured TI. This RP provides a method for accepting TI measurements from GBL when validated against a co-located met mast.
The recommended practice supplements DNV-ST-0437.