NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

This report is available at no cost from the National Renewable Energy

Laboratory (NREL) at www.nrel.gov/publications.

Contract No. DE-AC36-08GO28308

Technical Report

NREL/TP-5000-73292

February 2019

Array Effects in Large Wind Farms

Cooperative Research and Development Final 

Report

CRADA Number: CRD-15-590

NREL Technical Contact: Patrick Moriarty
NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

This report is available at no cost from the National Renewable Energy

Laboratory (NREL) at www.nrel.gov/publications.

Contract No. DE-AC36-08GO28308

National Renewable Energy Laboratory

15013 Denver West Parkway

Golden, CO 80401

303-275-3000 • www.nrel.gov

Technical Report

NREL/TP-5000-73292

February 2019

Array Effects in Large Wind Farms

Cooperative Research and Development Final 

Report

CRADA Number: CRD-15-590

NREL Technical Contact: Patrick Moriarty

Suggested Citation

Moriarty, Patrick. 2019. Array Effects in Large Wind Farms: Cooperative Research and 

Development Final Report, CRADA Number CRD-15-590. Golden, CO: National Renewable 

Energy Laboratory. NREL/TP-5000-73292. https://www.nrel.gov/docs/fy19osti/73292.pdf.
NOTICE

This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable 

Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding 

provided by the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Wind Energy 

Technologies Office. The views expressed herein do not necessarily represent the views of the DOE or the U.S. 

Government.

This report is available at no cost from the National Renewable 

Energy Laboratory (NREL) at www.nrel.gov/publications.

U.S. Department of Energy (DOE) reports produced after 1991 

and a growing number of pre-1991 documents are available 

free via www.OSTI.gov.

Cover Photos by Dennis Schroeder: (clockwise, left to right) NREL 51934, NREL 45897, NREL 42160, NREL 45891, NREL 48097, 

NREL 46526.

NREL prints on paper that contains recycled content.
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This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications

Cooperative Research and Development Final Report

Report Date: December 17, 2018

In accordance with requirements set forth in the terms of the CRADA agreement, this document 

is the final CRADA report, including a list of subject inventions, to be forwarded to the DOE 

Office of Science and Technical Information as part of the commitment to the public to 

demonstrate results of federally funded research.

Parties to the Agreement: Sibley School of Mechanical and Aerospace Engineering, 

Cornell University

CRADA Number: CRD-15-590

CRADA Title: Array Effects in Large Wind Farms

Joint Work Statement Funding Table showing DOE commitment:

Estimated Costs NREL Shared Resources a/k/a 

Government In-Kind

Year 1

Year 2

Year 3

$ 10,000.00

$ 10,000.00

$ 10,000.00

TOTALS $ 30,000.00

Abstract of CRADA Work:

The effects of wind turbine wakes within operating wind farms has a substantial impact on the 

overall energy production from the farm. The current generation of models drastically 

underpredicts the impact of these wakes offshore leading to non-conservative estimates of energy 

capture and financial losses to wind farm operators and developers. To improve these models, 

detailed research of operating wind farms is necessary. Cornell University is a world leader of 

wind farm wakes effects and would like to partner with NREL to help improve wind farm 

modeling (by gathering additional wind farm data), develop better models and increase 

collaboration with European researchers working in the same area.

Summary of Research Results:

The work accomplished under this agreement included advanced observations of wakes in full 

scale operating wind farms and a comparison to simulations using NREL-developed, large eddy 

simulation tools. The comparisons allowed researchers to quantify the uncertainty introduced 
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This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications

through observational campaigns—more specifically, lidar scanning patterns. Based on these 

uncertainty estimates, researchers recommend higher frequency and spatial fidelity scans to 

improve future wake measurement campaigns. The observations and large eddy simulation 

results were used to develop a new wind turbine wake model that was not dependent on 

axisymmetry to better capture the intermittent behavior of wake dynamics.

Under this agreement, researchers examined a series of lidar measurements from an offshore 

wind farm to determine if the data were of sufficient quality for wake model validation. The data 

were deemed too coarse and further examination with new complimentary data channels were 

deemed necessary. Additional analysis is being pursued as follow-on work.

Also under this agreement, researchers across institutes discussed needs for new future utility 

scale wake observational campaigns. Researchers hosted an international workshop of wake 

experts, refined science goals and shared lessons learned from previous wake field campaigns.

Planning for future wake field campaigns continues.

The results from this work were presented at international conferences focused on wind energy 

and atmospheric science and published in the journals Wind Energy and Remote Sensing. Links 

to the journals are below.

Doubrawa, P., Barthelmie, R.J., Wang, H., Churchfield, M.J., 2017. A stochastic wind turbine 

wake model based on new metrics for wake characterization. Wind Energy 20, 449–463. 

https://doi.org/10.1002/we.2015

Doubrawa, P., Barthelmie, R.J., Wang, H., Pryor, S.C., Churchfield, M.J., 2016. Wind Turbine 

Wake Characterization from Temporally Disjunct 3-D Measurements. Remote Sensing 8, 939. 

https://doi.org/10.3390/rs8110939

Subject Inventions Listing:

None

ROI #:

None

Responsible Technical Contact at Alliance/NREL:

Patrick Moriarty

Name and Email Address of POC at Company:

Rebecca J. Barthelmie, rb737@cornell.edu

DOE Program Office:

Office of Energy Efficiency and Renewable Energy Wind Energy Technologies Office

This document contains NO confidential, protectable, or proprietary information.