Editorial Type:
Article
Article Type:
Research Article

Crop Wind Energy Experiment (CWEX): Observations of Surface-Layer, Boundary Layer, and Mesoscale Interactions with a Wind Farm

Daniel A. Rajewski Department of Geological and Atmospheric Sciences, Iowa State University, Ames, Iowa

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Eugene S. Takle Department of Agronomy, Iowa State University, Ames, Iowa

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Julie K. Lundquist Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder, and National Renewable Energy Laboratory, Golden, Colorado

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Steven Oncley National Center for Atmospheric Research, Boulder, Colorado

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John H. Prueger National Laboratory for Agriculture and the Environment, Ames, Iowa

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Thomas W. Horst National Center for Atmospheric Research, Boulder, Colorado

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Michael E. Rhodes Aerospace Engineering Sciences, University of Colorado, Boulder, Colorado

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Richard Pfeiffer National Laboratory for Agriculture and the Environment, Ames, Iowa

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Jerry L. Hatfield National Laboratory for Agriculture and the Environment, Ames, Iowa

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Kristopher K. Spoth Department of Agronomy, Iowa State University, Ames, Iowa

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Russell K. Doorenbos Department of Agronomy, Iowa State University, Ames, Iowa

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Online Publication:
01 May 2013
Print Publication:
01 May 2013
DOI:
https://doi.org/10.1175/BAMS-D-11-00240.1
Page(s):
655–672
Restricted access

Perturbations of mean and turbulent wind characteristics by large wind turbines modify fluxes between the vegetated surface and the lower boundary layer. While simulations have suggested that wind farms could significantly change surface fluxes of heat, momentum, momentum, moisture, and CO2 over hundreds of square kilometers, little observational evidence exists to test these predictions. Quantifying the influences of the “turbine layer” is necessary to quantify how surface fluxes are modified and to better forecast energy production by a wind farm. Changes in fluxes are particularly important in regions of intensely managed agriculture where crop growth and yield are highly dependent on subtle changes in moisture, heat, and CO2. Furthermore, speculations abound about the possible mesoscale consequences of boundary layer changes that are produced by wind farms. To address the lack of observations to answer these questions, we developed the Crop Wind Energy Experiment (CWEX) as a multiagency, multiuniversity field program in central Iowa. Throughout the summer of 2010, surface fluxes were documented within a wind farm test site and a 2-week deployment of a vertically pointing lidar quantified wind profiles. In 2011, we expanded measurements at the site by deploying six flux stations and two wind-profiling lidars to document turbine wakes. The results provide valuable insights into the exchanges over a surface that has been modified by wind turbines and a basis for a more comprehensive measurement program planned for the summer in 2014.

CORRESPONDING AUTHOR: Daniel A. Rajewski, Iowa State University, 3132 Agronomy, Ames, IA 50011, E-mail: drajewsk@iastate.edu

Perturbations of mean and turbulent wind characteristics by large wind turbines modify fluxes between the vegetated surface and the lower boundary layer. While simulations have suggested that wind farms could significantly change surface fluxes of heat, momentum, momentum, moisture, and CO2 over hundreds of square kilometers, little observational evidence exists to test these predictions. Quantifying the influences of the “turbine layer” is necessary to quantify how surface fluxes are modified and to better forecast energy production by a wind farm. Changes in fluxes are particularly important in regions of intensely managed agriculture where crop growth and yield are highly dependent on subtle changes in moisture, heat, and CO2. Furthermore, speculations abound about the possible mesoscale consequences of boundary layer changes that are produced by wind farms. To address the lack of observations to answer these questions, we developed the Crop Wind Energy Experiment (CWEX) as a multiagency, multiuniversity field program in central Iowa. Throughout the summer of 2010, surface fluxes were documented within a wind farm test site and a 2-week deployment of a vertically pointing lidar quantified wind profiles. In 2011, we expanded measurements at the site by deploying six flux stations and two wind-profiling lidars to document turbine wakes. The results provide valuable insights into the exchanges over a surface that has been modified by wind turbines and a basis for a more comprehensive measurement program planned for the summer in 2014.

CORRESPONDING AUTHOR: Daniel A. Rajewski, Iowa State University, 3132 Agronomy, Ames, IA 50011, E-mail: drajewsk@iastate.edu
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