Upwind preview to a horizontal axis wind turbine: a wind tunnel and field‐scale study

Abstract

Data collected at the Eolos wind research facility and in the Saint Anthony Falls Laboratory atmospheric boundary layer wind tunnel are used to study the impact of turbulent inflow conditions on the performance of a horizontal axis wind turbine on flat terrain. The Eolos test facility comprises a 2.5MW Clipper Liberty C96 wind turbine, a meteorological tower and a WindCube LiDAR wind profiler. A second set of experiments was completed using particle image velocimetry upwind and in a wake of a miniature turbine in the wind tunnel to complement LiDAR measurements near the Eolos turbine. Joint statistics, most notably temporal cross‐correlations between wind velocity at different heights and turbine performance, are presented and compared at both the laboratory and field scales. The work (i) confirms that the turbine exerts a blockage effect on the mean flow and (ii) suggests a key, specific elevation, above hub height, where the incoming velocity signal is statistically most relevant to turbine operation and control. Wind tunnel measurements confirm such indication and suggest that hub height velocity measurements are optimal for wind preview and/or as input for active control strategies in aligned turbine configurations. Copyright © 2015 John Wiley & Sons, Ltd.

The spectral signature of wind turbine wake meandering: A wind tunnel and field‐scale study

“…While the laboratory inflow conditions were observed to provide a genuine, scaled representation of the atmospheric surface layer at the Eolos site, the model and utility‐scale turbine performances are significantly different. In particular, the wake deficit in the miniature turbine models is due to a relatively large drag as opposed to an efficient energy harnessing (see discussion of Howard et al).…”

“…Issues arising from the large horizontal sampling area can be partially mitigated by positioning the lidar in “local” orientation . Rather than positioning the Windcube in alignment with global coordinates, ie, having the north LOS oriented with true north, the Windcube was oriented such that the north and south LOSs were aligned with the anticipated mean wind direction.…”

“…The resulting Richardson number R i B = 0.14 indicates weak thermal stability, consistent with typical stability conditions for the early night deployment time. On the basis of the turbine performance parameters in Table , the turbine operated at near‐optimal conditions. Deployments 2 and 3: Measurements for deployments 2 ( x = 2.6 D ) and 3 ( x = 3.1 D ) were used in a previous study . The deployments were at the Eolos field site with the Windcube positioned in the turbine wake and the met tower used to characterize inflow conditions (as shown in the Figure schematic).…”

“…Four of the 5 field deployments in the current study were conducted at the Eolos Wind Research station in the University of Minnesota Outreach, Research, and Education Park in Rosemount, Minnesota. 3,14,16 The site topography is characterized by farmland with small local elevation changes (1-3 m) and sparse trees. The station includes a 2.5-MW Clipper Liberty C96 wind turbine and a met tower 170 m due south of the turbine.…”

“…Since the introduction of coherent lidar devices, wind profiling lidar has become increasingly popular for both nacelle‐mounted and ground‐based remote sensing . Lidar technology represents the best alternative to met towers for wind field experimentation and monitoring, with the exception of snow particle velocimetry measurements, which provide high‐resolution spatial (2‐D)–temporal (1‐D) flow fields in the turbine wake at field scale .…”