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Virtual Tower Measurements during AWAKEN

 
Poster PDF

Authors

Rob K Newsom — Pacific Northwest National Laboratory *
Raghavendra Krishnamurthy — Pacific Northwest National Laboratory
Duli Chand — Pacific Northwest National Laboratory
Mikhail S. Pekour — Pacific Northwest National Laboratory
Colleen Kaul — Pacific Northwest National Laboratory
* presenting author

Category

ARM field campaigns – Results from recent ARM field campaigns

Description

The American Wake experimeNt (AWAKEN) is an international, multi-institutional wind energy field campaign which is currently underway in the vicinity of the King Plains wind farm, south of the ARM Southern Great Plains (SGP) Central Facility. The goal of AWAKEN is to provide observations to better understand interactions between wind turbines in a wind farm as well as the overall impact of the wind farm on the lower atmospheric boundary layer. From ARM’s perspective, there is a need to understand how the numerous large wind farms in the region are affecting measurements at any of the SGP facilities. Thus, the ARM program is providing valuable support to the AWAKEN project including help with logistics, instrument deployments and data management.

One component of AWAKEN involves the use of dual-Doppler measurement techniques to characterize the inflow into the King Plains Wind Farm. Asynchronous dual-Doppler scanning methods are being used to create a linear array of three virtual towers extending southward from the leading row of turbines in the King Plains wind farm. Virtual towers are formed at the intersection of two Range-Height-Indicator (RHI) scans, where radial velocity measurements from both lidars are used to compute profiles of wind speed and direction, as well as estimates of uncertainty.

The virtual tower approach offers certain advantages over traditional surface-based profiling methods. The primary advantage is that the method does not rely on any assumption of horizontal homogeneity of the wind field. This is crucial for accurate wind profiling near wind turbines (or in complex terrain) where there is significant spatial variability in the wind field. Another advantage is that the virtual tower method enables much finer vertical resolution and allows measurements to be made much closer to the surface. In our case, scans were done using an angular resolution of 0.2o, which enabled post-processing using a vertical grid resolution of 10 m. The maximum heights of the virtual towers ranged from 209 to 432 mAGL.

Data collection for the dual-Doppler experiment began on 11 November 2022 and will continue until September 2023. In this poster we describe the dual-Doppler configuration, scan strategies, and data processing methods. Preliminary results from six virtual towers are presented, including comparisons with collocated profiling lidars.