An independent performance verification of a nacelle-mounted ZephIR Lidar has been undertaken by DNV GL on the test site in Janneby, Germany. In the verification, the ZephIR DM nacelle-mounted lidar was mounted horizontally on a raised platform (FW-MM) – 180 metres away from two reference met masts (T-MM-N and T-MM-S) equipped with calibrated anemometers at DNV GL’s test site, located 20 kilometres southwest of Flensburg, Germany.
A series of tests and subsequent analysis was undertaken by DNV GL on the performance of the ZephIR DM with respect to:
- Verification of inclinometers. ZephIR DM uses highly sensitive positional sensors to account for turbine sway and nod to ensure a true Hub Height measurement is reported at several rotor diameters in front of the turbine within +/- 1% of Hub Height
- Availability. ZephIR DM achieved a 100% availability of both system and data during the performance verification. A Continuous Wave lidar, all power from the system’s laser is focused at each measurement range, which helps to ensure the highest levels of sensitivity and therefore data availability, in all environmental conditions
- Wind speed comparison. White box test results are shown below where a correlation gradient of 1.00026 was achieved, i.e. a 0.026% difference between the lidar line-of-sight and mast wind speeds were observed
ZephIR Lidar’s nacelle-based wind profiler, ZephIR DM, has been demonstrated to measure wind speed when mounted on a wind turbine at a very accurate level. Additionally, the ZephIR DM offers the advantage of being mobile and scanning at up to several hundred metres ahead of the rotor in free stream wind flow for a power curve measurement.