On the accuracy of X-band Dual-Doppler Radar for wind energy applications: a comparison study.

Wind energy research relies on remote sensing technologies like dual-Doppler (DD) lidar and radar, or space-born SAR data to estimate complex meteorological conditions and the flow field around wind farms. Offshore measurement campaigns over the last decade accentuate the potential of DD wind radar technology for wind energy application. Onshore, promising results were also reported as part of the American WAKE ExperimeNt (AWAKEN).
The main drawback of wind radar technology is that further characterisation of radar measurement accuracy is required for industry implementation. We investigate X-band wind radar measurement accuracy in a comparison study, using meteorological mast data and wind lidars from an onshore measurement campaign.
Despite their cost, meteorological masts provide very accurate point measurements over specific heights, and are the preferred reference for wind validation. Wind lidars are a proven alternative, as demonstrated in several offshore campaigns. Like for lidars, radar's measurement principle is based on the Doppler effect, and both devices allow for wind field estimates. Yet, radars can scan over larger distances at a much higher sampling rate, with increased resolution along the beam due to the use of a compressed pulse. However, unlike pulsed lidars that emit collimated beams, the radar beam expands with distance, which arguably adds uncertainty to the measurements at far ranges.
A dual-Doppler lidar-radar set-up is used with the remote sensing devices collocated in space, but measuring a-synchronously. We conduct the analysis on wind component basis (u, v) and wind speed and direction, focusing on inflow in front of a large wind turbine (OPUS 1) at the onshore Wivaldi Test Site in Northern Germany, as part of the radar Krummendeich Campaign. Lidars and radars are deployed approximately 3 km to 4 km away from the collocated lidar - meteorological mast - radar measurements. Although the influence of increased probe volume averaging, due to beam expansion, in distance is unclear due to campaign set-up, the results presented set a ground base for further use of long range wind lidars as validation for upcoming radar measurement campaigns.