Airborne Wind Energy

MOST of wind energy systems, like wind turbines, extract power at low altitudes. Although an extensive wind exploitation and a remarkable growth happened thanks to conventional technologies, important benefits can be obtained by making the systems operate at high altitudes, where winds are stronger and less intermittent. In addition, the substitution of wind turbines by lightweight structures placed at a high altitude, such as kites, would reduce the costs and the visual impact. Airborne wind energy (AWE) systems are technologies that convert wind energy into electrical energy and are made of one or more aerial autonomous vehicle linked to the ground by at least one tether. These systems generate electricity by using the tether tension to move a generator on the ground (ground-generation) or using on-board wind turbines (fly-generation).

Although some activities on kite dynamics and control were carried out from 2004 to 2006, UC3M activities on AWE systems formally started in 2015 thanks to a Leonardo Grant funded by BBVA Foundation. From 2016 to 2019, the team performed research and development activities thanks to GreenKite, a project supported by the Spanish Government. Recently, project GreenKite-2 by the Spanish Government has been granted as a continuation of the latter project lasting from 2020 to 2023. In parallel, many Bachelor and Master Aerospace students developed their minor theses in our group, one PhD thesis was defended in 2021 and another is in progress. The topics include the modelling, simulation and control of AWE systems, as well as the aerodynamic and aeroelastic characterization through numerical and experimental analysis.

Research capabilities

AWE simulator

UC3M has developed LAKSA, an open source simulation package to study the dynamic and control of AWE systems (Download). The software has 5 modules aimed at different machine architectures. The equations of motion of four of them were found by using a Lagrangian formulation with a minimal coordinate approach. This feature, and the inelastic but flexible character of the tethers of the models, yield a non-stiff system of ordinary differential equations that is not coupled with algebraic constraints. As a consequece, the code is robust and efficient. LAKSA’s module named KiteFlex can be used to study ground-generation and fly-generation systems. It considers the self-consistent dynamics of the aircraft (a rigid body), the on-board rotors, and a flexible tether. Its control vector in the most sophisticated configuration involves the length of the main tether for making reel-in and reel-out, the lengths of the lines of the bridle and the deflections of ailerons, rudder and elevator for steering the aircraft, and the torque of the motor controllers of the rotors. As a consequence, the code is prepared for analyzing a great variety of AWE machines, including the ones developed by companies such as Makani, Kitepower, Ampyxpower, TwingTec and Enerkite among others.

Typo: dynamics

Flight testing of power kites

UC3M has experience on flight testing activities of power and acrobatic kites. The main goal is getting real flight data to feed an already prepared Extended Kalman Filter that provides an estimation of the full state vector of the kites, including the aerodynamic force and torque. Such estimation can be used to find an appropriate aerodynamic model of the kites by using estimation before modelling techniques. The team developed an infrastructure for performing flight testing activities with two different leading-edge inflatable kites (Cabrinha Switchblade 10m2 and Cabrinha Contra 13m2) and an acrobatic kite (Fazer XXL, 3.6m wingspan). Currently, UC3M can perform flight testing to get real data of the kite position, velocity, Euler angles, angular velocity, acceleration, aerodynamic velocity vector, tether tensions, and state of the control bar. The most sophisticated and precise instrument in the infrastructure is a multi-hole pitot tube from Aeroprobe Corporation that provides the magnitude of the aerodynamic velocity and the angle of attack and the sideslip angle.

Typo: the magnitude of the aerodynamic velocity, the angle of attack and the sideslip angle

Mechanical Control System of two-line kites

UC3M has developed a testbed for the aerodynamic characterization of kites. It involves a mechanical control system with a linear actuator, inertial navigation unit with GNSS and a multihole pitot tube onboard the kite for the measurement of the kite kinematic state and the in-situ measurement of the full aerodynamic velocity vector (modulus, angle of attack and sideslip angle), load cells at the tethers, and a weather station for measuring the wind velocity (modulus and direction). Several visiting PhD, Bachelor, and Master students collaborated in the design, manufacturing and testing of the testbed. 

The video on the top shows a breadboard of the mechanical control system of the testbed that was commanded with a radio. The figure on the right shows the actual state of the testbed. All the sensors are connected to a computer and the kite is controlled with a joystick. The team is working on closing the control loop and reaching autonomous operation of the testbed.

Computational aerodynamic characterization of kites

An in-house three-dimensional unsteady panel method (UnPaM, hyperlink linked to text “UnPaM”: has been adapted to Rigid-Framed Delta (RFD) kites. This work opens the possibility to compare theoretical aerodynamic forces and moments to experimental ones (from flight-testing campaigns) for a deeper characterization and understanding of kites’ aerodynamics.

Competitive research projects

  1. Desarrollo de sistemas de generación de energía con sistemas aerotransportados. CT Ingenieros, 2021-2022. PI: G. Sánchez-Arriaga
  2. Modelling and flight testing of airborne wind energy and traction systems (GreenKite-2)
    Agencia Estatal de Investigación (Ministerio de Ciencia, Innovación y Universidades), 48.000€, PID2019-110146RB-I00, 2020-2023,
    PI: G. Sánchez-Arriaga
  3. Simulation and Flight Testing of Power Kites Applied to Wind Energy Generation (GreenKite)
    Ministerio de Economía, Industria y Competitividad of Spain, 53.240€, ENE2015-69937-R, 2016-2019, PI: G. Sánchez-Arriaga
  4. Leonardo Grant, Fundación BBVA, Generación Limpia de Energía con Cometas de Tracción
    Fundación BBVA, 40.000€, 2015-2016, PI: G. Sánchez-Arriaga

Recent publications

  1. Modeling and Natural Mode Analysis of Tethered Multi-Aircraft Systems
    G. Sánchez-Arriaga, J. A. Serrano-Iglesias, R. Leuthold and M. Diehl, Guidance, Control and Dynamics, (2021) []
  2. Identification of kite aerodynamics using the estimation before modeling technique
    R. Borobia-Moreno, D. Ramiro-Rebollo, R. Schmehl and G. Sánchez-Arriaga,
    Wind Energy, (2021) []
  3. Activities and Roadmap on Airborne Wind Energy Systems at UC3M
    R. Borobia-Moreno, I. Castro, A. Pastor, H. Endo, C. Cobos, R. Cavallaro and G. Sánchez-Arriaga, Wind Energy (Japan Wind Energy Society), (2020) []
  4. A lagrangian flight simulator for airborne wind energy systems
    G. Sanchez-Arriaga, A. Pastor-Rodríguez, M. Sanjurjo-Rivo, R. Schmehl, Applied Mathematical Modelling, (2019) [DOI]
  5. Flight Path Reconstruction and Flight Test of Four-line Power Kites
    R. Borobia-Moreno, G. Sanchez-Arriaga, A. Serino, R. Schmehl, Journal of Guidance Control and Dynamics, (2018) [DOI]
  6. A constraint-free flight simulator package for airborne wind energy systems
    G. Sanchez-Arriaga, A. Pastror-Rodríguez, R. Borobia-Moreno, R. Schmehl, Journal of Physics: Conference Series, (2018) [DOI]
  7. Modeling and stability analysis of tethered kites at high-altitudes
    A. Pastror-Rodríguez, G. Sanchez-Arriaga, M. Sanjurjo-Rivo, American Institute of Aeronautics and Astronautics, (2017) [DOI]
  8. Modeling and dynamics of a two-line kite
    G. Sanchez-Arriaga, M. García-Villalba, R. Schmehl, Applied Mathematical Modelling, (2017) [DOI]
  9. A Kite model with bridle control for wind power generation
    J. Alonso and G. Sanchez-Arriaga, Journal of Aircraft, (2015) [DOI]
  10. Flight dynamics and stability of kites in steady and unsteady wind conditions
    L. Salord and G. Sanchez-Arriaga, Journal of Aircraft, (2014) [DOI]
  11. Dynamics and control of single-line kites
    G. Sanchez-Arriaga, The Aeronautical Journal, (2006) [DOI]

Conference presentations

  1. 3D Unsteady Aerodynamic Analysis of a Rigid-Framed Delta Kite applied to AWES
    I. Castro-Fernández, R. Borobia-Moreno, R. Cavallaro, G. Sánchez-Arriaga, Wind Energy Science Conference (WESC 2021), Hannover, (2021)
  2. Flight Testing, Aerodynamic Parameter Identification and Dynamic Simulation of Rigid and Flexible Kites Applied to Airborne Wind Energy Systems
    R. Borobia-Moreno, D. Ramiro-Rebollo, G. Sánchez-Arriaga, R. Schmehl, Airborne Wind Energy Conference, Glasgow, (2019)
  3. A Small-Scale Experimental Setup aimed at the aerodynamic parameter identification of flexible and rigid kites applied to airborne wind energy systems
    R. Borobia-Moreno, G. Sánchez-Arriaga, 7th European Conference on Renewable Energy Systems, Madrid, (2019)
  4. Lagrangian and classical multi-drone dynamic simulators with application to airborne wind energy systems
    J. A. Serrano-Iglesias, G. Sánchez-Arriaga, 7th European Conference on Renewable Energy Systems, Madrid, (2019)
  5. A constraint-free flight simulator package for airborne wind energy systems
    G. Sanchez-Arriaga, A. Pastor-Rodríguez, R. Borobia-Moreno, R. Schmehl, Torque2018, Milan, (2018)
  6. Application of the Estimation Before Modelling (EBM) technique to the Aerodynamic Characterization of Power Kites
    R. Borobia-Moreno, G. Sanchez-Arriaga, R. Schmehl, Airborne Wind Energy Conference, Freiburg, (2017)
  7. Determination of Optimal Control Laws in Airborne Wind Energy Scenarios With a Self-Consistent Kite Dynamics Model
    D. Expósito, M. Soler, G. Sanchez-Arriaga, Airborne Wind Energy Conference, Freiburg, (2017)
  8. Experimental setup to study airborne wind energy generation using a train of kites
    H. Endo, K. Arakawa, G. Sanchez-Arriaga, H. Fujii, H. Okubo, Y. Takahashi, Airborne Wind Energy Conference, Freiburg, (2017)
  9. Kite Flight Simulators Based on Minimal Coordinate Formulations
    G. Sanchez-Arriaga, A. Pastor-Rodríguez, M. García-Villalba, M. Sanjurjo-Rivo, R. Borobia-Moreno, R. Schmehl, Airborne Wind Energy Conference, Freiburg, (2017)
  10. A low-cost experimental platform for airborne wind energy generation using kites
    H. Hendo, G. Sanchez-Arriaga, World Wind Energy Conference, Malmoe, (2017)
  11. Flight Testing Setup for the Aerodynamic Characterisation of Power Kites Applied to Airborne Wind Energy Generation
    R. Borobia-Moreno, A. Serino, H. Hendo, G. Sanchez-Arriaga, World Wind Energy Conference, Malmoe, (2017)
  12. Kite Flight Simulator
    G. Sanchez-Arriaga, AIAA Pegasus Student Conference, Toulouse, (2005)

PhD Theses

  1. Aplication of Flight Testing Techniques to the Aerodynamic Charaterization of Power Kites
    R. Borobia-Moreno. Director: G. Sánchez-Arriaga. On-going Thesis
  2. Aeroelastic Analysis of Kites Applied to Airborne Wind Energy Systems
    I. Castro-Fernández. Directors: R. Cavallaro and G. Sánchez-Arriaga. On-going Thesis

Bachelor and Master Theses

  1. Readiness of a Mechanical Control System for Dual-Line Kites Applied to Airborne Wind Energy Systems
    M. Fernández-Jiménez. Director: I. Castro-Fernández, UC3M, (2021)
  2. Real-Time Visual Motion Tracker for Airborne Wind Energy Systems Control
    M. Zas-Bustingorri. Director: I. Castro-Fernández, UC3M, (2021)
  3. A Telemetry System Applied to a Small-Scale Airborne Wind Energy System
    A. Tarek Ghobaissi-González. Director: G. Sánchez-Arriaga, UC3M, (2021)
  4. Robust Mechanical Control System for a Dual-Line Kite Applied to Airborne Wind Energy Systems
    S. Rashwan. Director: I. Castro-Fernández, UC3M, (2020)
  5. Visual Motion Tracking for a Control System in an Airborne Wind Energy Application
    K. Best. Director: G. Sánchez-Arriaga, UC3M, (2020)
  6. Flight Testing Rig for Airborne Wind Energy Systems
    D. Ramiro-Rebollo. Director: G. Sánchez-Arriaga, UC3M, (2019)
  7. Design and Manufacturing of a Control System for a Dual-Line Kite
    M. Poole. Director: G. Sánchez-Arriaga, UC3M, (2018)
  8. Design of a mechanical assembly for power kites automatic control
    A. Huerta, Director: G. Sánchez-Arriaga, UC3M, (2018)
  9. Modeling and simulation of a train of kites
    J. A. Serrano, Director: G. Sánchez-Arriaga, UC3M, (2018)
  10. Path Controller Implementation for Airborne Wind Energy Systems
    G. Escribano, Director: G. Sánchez-Arriaga, UC3M, (2018)
  11. Control System and Hardware-related Elements Applied to Flight Testing of Airborne Wind Energy Systems
    A. Otero, Director: G. Sánchez-Arriaga, UC3M, (2018)
  12. Flight Testing of Power Kites
    I. Martín, Director: G. Sánchez-Arriaga, UC3M, (2017)
  13. Dynamics and control of acrobatic kites
    P. Muñoz, Director: G. Sánchez-Arriaga, UC3M, (2016)
  14. On-board instruments and flight tests of giant kites applied to wind power generation
    A. Serino, Director: G. Sánchez-Arriaga, Politecnico de Torino, (2016)
  15. Dinámica y Control de Cometas con bridas de geometría variable
    J. A. Pardo, Director: G. Sánchez-Arriaga, Politécnica de Madrid, (2014)
  16. Dinámica y control de cometas de una línea
    L. Salord, Director: G. Sánchez-Arriaga, Politécnica de Madrid, (2013)