Articles | Volume 11, issue 1
https://doi.org/10.5194/wes-11-195-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/wes-11-195-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Concurrent aerodynamic design of the wing and the turbines of airborne wind energy systems
Filippo Trevisi
CORRESPONDING AUTHOR
Department of Electronics, Information and Bioengineering, Politecnico di Milano, Via Ponzio, 34, 20133 Milano, Italy
Gianni Cassoni
Department of Aeronautical Technologies Engineering, Roma Tre University, Via della Vasca Navale, 79, 00146 Rome, Italy
Department of Aerospace Science and Technology, Politecnico di Milano, Via La Masa, 34, 20156 Milano, Italy
Mac Gaunaa
DTU Wind Energy, Frederiksborgvej 399, 4000 Roskilde, Denmark
Lorenzo Mario Fagiano
Department of Electronics, Information and Bioengineering, Politecnico di Milano, Via Ponzio, 34, 20133 Milano, Italy
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Wind Energ. Sci., 8, 1639–1650, https://doi.org/10.5194/wes-8-1639-2023, https://doi.org/10.5194/wes-8-1639-2023, 2023
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The power equations of crosswind Ground-Gen and Fly-Gen airborne wind energy systems (AWESs) are refined to include the contribution from the aerodynamic wake. A novel power coefficient is defined by normalizing the aerodynamic power with the wind power passing through a disk with a radius equal to the AWES wingspan, allowing us to compare systems with different wingspans. Ground-Gen and Fly-Gen AWESs are compared in terms of their aerodynamic power potential.
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Modeling the aerodynamic wake of airborne wind energy systems (AWESs) is crucial to properly estimating power production and to designing such systems. The velocities induced at the AWES from its own wake are studied with a model for the near wake and one for the far wake, using vortex methods. The model is validated with the lifting-line free-vortex wake method implemented in QBlade.
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The optimal control problem for the flight trajectories of Fly-Gen AWESs is expressed with a novel methodology in the frequency domain through a harmonic balance formulation. The solution gives the optimal trajectory and the optimal control inputs. Optimal trajectories have a circular shape squashed along the vertical direction, and the optimal control inputs can be modeled with only one or two harmonics. Analytical approximations for optimal trajectory characteristics are also given.
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Wind Energ. Sci. Discuss., https://doi.org/10.5194/wes-2025-258, https://doi.org/10.5194/wes-2025-258, 2025
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When wind turbines operate in conditions, which they were not actively designed for, e.g. complex terrain, they might show unexpected performance variations. Two causes for this, performance constraints due to flow physics , and wind turbine control are analyzed in detailed. Results show, that maximum power performance varies in complex terrain and that rotor-torque based control strategies might operate suboptimally in these conditions.
Ang Li, Mac Gaunaa, and Georg Raimund Pirrung
Wind Energ. Sci., 10, 2515–2550, https://doi.org/10.5194/wes-10-2515-2025, https://doi.org/10.5194/wes-10-2515-2025, 2025
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Wind Energ. Sci., 10, 2299–2349, https://doi.org/10.5194/wes-10-2299-2025, https://doi.org/10.5194/wes-10-2299-2025, 2025
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Clemens Paul Zengler, Niels Troldborg, and Mac Gaunaa
Wind Energ. Sci., 10, 1485–1497, https://doi.org/10.5194/wes-10-1485-2025, https://doi.org/10.5194/wes-10-1485-2025, 2025
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Wind turbine power performance is mostly calculated based on the wind speed measured at the turbine position. The presented results imply that it is necessary to also assess how the undisturbed wind speed changes in the flow direction to accurately predict the power performance. In other words, the acceleration of the flow is relevant for the energy production. An outcome of this work is a simple model that can be used to include flow acceleration in power performance predictions.
Nanako Sasanuma, Akihiro Honda, Christian Bak, Niels Troldborg, Mac Gaunaa, Morten Nielsen, and Teruhisa Shimada
Wind Energ. Sci. Discuss., https://doi.org/10.5194/wes-2025-130, https://doi.org/10.5194/wes-2025-130, 2025
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We verify wake effects between two turbines in complex terrain using Supervisory Control and Data Acquisition data. By identifying “wake conditions” and “no-wake conditions” by the blade pitch angle of the upstream wind turbine, we evaluate wake effects on wind speed, turbulent intensity, and power output. Results show that flow downhill has a significant impact on wake effects compared to flow uphill. The method offers a practical alternative to field measurements in complex terrain.
Jelle Agatho Wilhelm Poland, Johannes Marinus van Spronsen, Mac Gaunaa, and Roland Schmehl
Wind Energ. Sci. Discuss., https://doi.org/10.5194/wes-2025-77, https://doi.org/10.5194/wes-2025-77, 2025
Revised manuscript accepted for WES
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We tested a small model of an energy-generating kite in a wind tunnel to study its aerodynamic behavior. By comparing measurements to computer simulations, we validated the models and identified where they match the real performance and where they fall short. These insights will guide more accurate aerodynamic modeling and inform design choices for kites used in airborne wind energy systems.
Filippo Trevisi, Carlo E. D. Riboldi, and Alessandro Croce
Wind Energ. Sci., 8, 1639–1650, https://doi.org/10.5194/wes-8-1639-2023, https://doi.org/10.5194/wes-8-1639-2023, 2023
Short summary
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The power equations of crosswind Ground-Gen and Fly-Gen airborne wind energy systems (AWESs) are refined to include the contribution from the aerodynamic wake. A novel power coefficient is defined by normalizing the aerodynamic power with the wind power passing through a disk with a radius equal to the AWES wingspan, allowing us to compare systems with different wingspans. Ground-Gen and Fly-Gen AWESs are compared in terms of their aerodynamic power potential.
Filippo Trevisi, Carlo E. D. Riboldi, and Alessandro Croce
Wind Energ. Sci., 8, 999–1016, https://doi.org/10.5194/wes-8-999-2023, https://doi.org/10.5194/wes-8-999-2023, 2023
Short summary
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Modeling the aerodynamic wake of airborne wind energy systems (AWESs) is crucial to properly estimating power production and to designing such systems. The velocities induced at the AWES from its own wake are studied with a model for the near wake and one for the far wake, using vortex methods. The model is validated with the lifting-line free-vortex wake method implemented in QBlade.
Mac Gaunaa, Niels Troldborg, and Emmanuel Branlard
Wind Energ. Sci., 8, 503–513, https://doi.org/10.5194/wes-8-503-2023, https://doi.org/10.5194/wes-8-503-2023, 2023
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We present an analytical vortex model. Despite its simplicity, the model is fully consistent with 1D momentum theory. It shows that the flow through a non-uniformly loaded rotor operating in non-uniform inflow behaves locally as predicted by 1D momentum theory. As a consequence, the local power coefficient (based on local inflow) of an ideal rotor is unaltered by the presence of shear. Finally, the model shows that there is no cross-shear deflection of the wake of a rotor in sheared inflow.
Filippo Trevisi, Iván Castro-Fernández, Gregorio Pasquinelli, Carlo Emanuele Dionigi Riboldi, and Alessandro Croce
Wind Energ. Sci., 7, 2039–2058, https://doi.org/10.5194/wes-7-2039-2022, https://doi.org/10.5194/wes-7-2039-2022, 2022
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The optimal control problem for the flight trajectories of Fly-Gen AWESs is expressed with a novel methodology in the frequency domain through a harmonic balance formulation. The solution gives the optimal trajectory and the optimal control inputs. Optimal trajectories have a circular shape squashed along the vertical direction, and the optimal control inputs can be modeled with only one or two harmonics. Analytical approximations for optimal trajectory characteristics are also given.
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A consistent method of using two-dimensional airfoil data when using generalized lifting-line methods for the aerodynamic load calculation of non-planar horizontal-axis wind turbines is described. The important conclusions from the unsteady two-dimensional airfoil aerodynamics are highlighted. The impact of using a simplified approach instead of using the full model on the prediction of the aerodynamic performance of non-planar rotors is shown numerically for different aerodynamic models.
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Wind Energ. Sci., 7, 129–160, https://doi.org/10.5194/wes-7-129-2022, https://doi.org/10.5194/wes-7-129-2022, 2022
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An engineering aerodynamic model for the swept horizontal-axis wind turbine blades is proposed. It uses a combination of analytical results and engineering approximations. The performance of the model is comparable with heavier high-fidelity models but has similarly low computational cost as currently used low-fidelity models. The model could be used for an efficient and accurate load calculation of swept wind turbine blades and could eventually be integrated in a design optimization framework.
Ang Li, Mac Gaunaa, Georg Raimund Pirrung, and Sergio González Horcas
Wind Energ. Sci., 7, 75–104, https://doi.org/10.5194/wes-7-75-2022, https://doi.org/10.5194/wes-7-75-2022, 2022
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An engineering aerodynamic model for non-planar horizontal-axis wind turbines is proposed. The performance of the model is comparable with high-fidelity models but has similarly low computational cost as currently used low-fidelity models, which do not have the capability to model non-planar rotors. The developed model could be used for an efficient and accurate load calculation of non-planar wind turbines and eventually be integrated in a design optimization framework.
Thanasis Barlas, Georg Raimund Pirrung, Néstor Ramos-García, Sergio González Horcas, Robert Flemming Mikkelsen, Anders Smærup Olsen, and Mac Gaunaa
Wind Energ. Sci., 6, 1311–1324, https://doi.org/10.5194/wes-6-1311-2021, https://doi.org/10.5194/wes-6-1311-2021, 2021
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Curved blade tips can potentially have a significant impact on wind turbine performance and loads. A swept tip shape optimized for wind turbine applications is tested in a wind tunnel. A range of numerical aerodynamic simulation tools with various levels of fidelity are compared. We show that all numerical tools except for the simplest blade element momentum based are in good agreement with the measurements, suggesting the required level of model fidelity necessary for the design of such tips.
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Short summary
This paper investigates the optimal aerodynamic design of the wing and the onboard turbines of the fly-gen airborne wind energy system aircraft, named wind plane here, with a novel comprehensive engineering aerodynamic model and with the vortex particle method. Placing the turbines at the wing tips, rotating them inboard downward with a low tip speed ratio, and using conventional efficient airfoils for the wing are found to be optimal for wind planes.
This paper investigates the optimal aerodynamic design of the wing and the onboard turbines of...
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