Special Issue "Airborne Wind Energy Systems"
A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A3: Wind, Wave and Tidal Energy".
Deadline for manuscript submissions: 31 January 2023 | Viewed by 17166
Special Issue Editors

Interests: modeling; control; efficiency enhancements; fault detection and condition monitoring of mechatronic and renewable energy systems
Special Issues, Collections and Topics in MDPI journals

Interests: airborne wind energy; fluid–structure interaction; two-phase flows; liquid droplet; modeling; renewable energy technologies; numerical analysis; power generation; engineering thermodynamics; computational fluid dynamics; fluid mechanics; numerical simulation; thermal engineering; numerical modeling; aerodynamics
Special Issue Information
Dear colleagues,
Airborne wind energy (AWE) systems convert wind energy into electrical energy using autonomous tethered flying devices. Deemed a potentially game-changing solution to clean and sustainable energy generation, AWE is increasingly attracting the attention of governments, policymakers and industry worldwide. AWE technology can significantly reduce the levelized cost of energy (LCoE) by eliminating (i) the drive-train installation, (ii) a large part of the rotor blades, (iii) the tower, and (iv) the foundation, which make up for about 50% of the conventional turbine costs. On the other hand, the development of this technology is also facing substantial technical challenges. Important aspects are, for example, autonomous, efficient, reliable, safe, and uninterrupted operation of AWE systems and their interconnection with the future power grid.
We cordially invite original manuscripts presenting recent advances in this important and interdisciplinary research field with particular focus on but not limited to the following:
- Aerodynamics, aeroelasticity, and structural dynamics;
- Flight dynamic modeling;
- Flightpath planning and control of AWE systems;
- AWE design optimization;
- Higher altitude wind resources;
- Experimental testing of prototypes;
- Efficiency enhancements (by, e.g., intelligent design and/or control);
- Nonlinear, optimal, and fault-tolerant control strategies;
- Fault detection methods and condition monitoring approaches;
- Robust, fault-tolerant and flexible grid connection/integration (e.g., grid-supporting, -feeding, -forming including black start capability);
- Economic and market analysis;
- AWE policy-making, environmental impact, and societal acceptance.
The Special Issue will present cutting-edge research results connected to AWE technology as a basis for enduring operation. All research results must be presented in a mathematically thorough (e.g., in state space) but understandable manner to encourage insights and re-implementation by the readers so that the knowledge basis is shared, spread, and extended to promote AWE systems to the market. All results should be validated by simulation and measurement results (if possible).
Prof. Dr. Christoph M. Hackl
Dr. Roland Schmehl
Guest Editors
Manuscript Submission Information
Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.
Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.
Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.
Keywords
- airborne wind energy system
- aerodynamics
- aeroelasticity
- dynamic modeling
- performance modeling
- fault-tolerance
- reliable operation
- safety engineering
- flexible grid connection
Planned Papers
The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.
Title: Swinging Motion of a Flexible Membrane Kite with Suspended Control Unit During Turning Manoeuvres
Authors: Mark Schelbergen and Roland Schmehl
Affiliation: Delft University of Technology
Abstract: xxx
Title: Life Cycle Assessment of Multi-Megawatt Airborne Wind Energy
Authors: Luuk Van Hagen; Kristian Petrick; Stefan Wilhelm; Roland Schmehl
Affiliation: Delft University of Technology
Abstract: A key motivation for airborne wind energy is its potential to reduce the amount of material required for the generation of renewable energy. On the other hand, the materials that are used for the airborne system components are generally linked to higher environmental impacts. This study presents comparative life cycle analyses for future multi-megawatt airborne wind energy systems and conventional wind turbines, with both technologies operating in the same farm configuration and under matching environmental conditions. The analyses quantify the global warming potential and cumulative energy demand of the emerging and established wind energy technologies. The cumulative energy demand is subsequently also used to determine the energy payback time and the energy return of investment. The selected airborne wind energy system is based on the design of Ampyx Power, using a fixed-wing aircraft that is tethered to a generator on the ground. The conventional wind turbine is primarily based on the NREL 5 MW reference turbine. The results confirm that an airborne wind energy system uses significantly fewer materials and generates electricity at notably lower impacts than the conventional wind turbine. Furthermore, the impacts of the wind turbine depend strongly on the local environmental conditions, while the impacts of the airborne wind energy system show only a minimal dependency. Airborne wind energy is found to be most advantageous for operation at unfavourable environmental conditions for the conventional systems, where the turbines require a large hub height.
Title: High fidelity fluid-structure interaction simulation of a multi-megawatt airborne wind energy reference system in cross-wind flight
Authors: N Pynaert 1,2; J Wauters 1,2; G Crevecoeur 1,2 and J Degroote 1,2
Affiliation: 1 Department of Electromechanical, Systems and Metal Engineering, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent, Belgium; 2 Core lab EEDT, Flanders Make, Belgium
Abstract: xxx
Title: Modelling Aeroelastic Deformation of Flexible Membrane Kites
Authors: Jelle A.W. Poland; Roland Schmehl
Affiliation: Delft University of Technology
Abstract: Airborne wind energy systems using flexible membrane wings have the advantages of low weight, small packing volume, high mobility and rapid deployment. In this paper, we propose a particle system approach for simulating the deformation of a leading-edge inflatable kite. In this approach, each wing segment is represented by four point masses whose relative position along the tubular frame is kept constant by linear spring-damper elements. The billowing of the trailing edge of the wing is taken into account by an empirical correlation. Line segments of the bridle line system are modelled by two point masses connected by a spring-damper element. A pulley model is provided to connect three line
segments. The generated aerodynamic force balances the spring- and damper forces and is determined using the lift equation with a linear lift polar for each wing segment separately. The particle system model can be used to describe the symmetric deformation of the wing in response to a symmetric actuation of the bridle lines used for depowering the kite, changing the pitch angle. The model also reproduces the typical twist deformation of the wing in response to an asymmetric
line actuation used for steering the kite. Simulated wing shapes are compared with photogrammetric information taken from the video camera on the kite control unit that looks at the kite during flight. The results demonstrate how a particle system model can accurately predict the shape of a soft wing for low computational cost, making it an ideal structural building block towards the next generation of soft wing kite models.
Title: Low and high fidelity aerodynamic simulations of box wing kites for airborne wind energy applications
Authors: Dylan Eijkelhof; Gabriel Buendía; Roland Schmehl
Affiliation: Delft University of Technology
Abstract: Airborne wind energy systems (AWES) convert the kinetic energy of the wind into electricity, from which the power is directly proportional to the aerodynamic efficiency. The need of a high aerodynamic coefficient implies high aerodynamic loads and thus, for conventional AWE wings, a high thickness-to-chord ratio. The box wing concept opens the possibility of exploring thinner aerofoil profiles as the load distribution can be changed with a lower wing span and reinforcements between the wings. This study focuses on creating a tool for reliable aerodynamic simulations that check the superior performance of box wings to conventional wings and automating the design and meshing processes involved. The aerodynamic tools used, include a steady panel method solver (APAME) and CFD simulations based on a RANS model using a k-\texorpdfstring{$\omega$}{Omega} SST turbulence model (OpenFOAM). The CFD mesh is created automatically using Pointwise commands from a set of eight physical design parameters, 5 aerofoil profiles and mesh refinement specifications. Fast simulations and accurate values were obtained using the panel method for the linear region of the lift coefficient, but CFD simulations with high to medium quality meshes were required to obtain good agreement with experiments in the lift and drag coefficient. The CFD simulations showed delayed stall of the upper wing with respect to the lower one, increasing the stall angle of attack. Also, the wing tip boundary layer separation is delayed compared to the wing root for the straight rectangular box wing. Choosing the design point and operational envelope smartly could enhance the aerodynamic performance of AWE kites, which are likely to operate at high angles of attack to increase the aerodynamic forces, which maximises the tether force, leading to a higher power output.
Title: Hybrid Power Systems Using Airborne Wind Energy
Authors: Sweder Reuchlin; Rishikesh Joshi; Roland Schmehl
Affiliation: Delft University of Technology
Abstract: A majority of the remote area locations which are not connected to the main electricity grid rely on diesel generators for meeting their electricity requirement. High transportation costs for fuel along with significant carbon emissions has motivated the development and installation of hybrid renewable energy systems in these locations. Hybrid power systems combining wind and solar are of interest due to the their negative correlation on a daily as well as seasonal timescales. Since these resources are intermittent by nature, they are usually combined with a storage solution for a more secure power supply. This paper presents a modelling and sizing framework for hybrid power systems using airborne wind energy as one of its components. The framework uses hourly timeseries data of wind and solar combining with the load data to estimate the optimal sizing of the hybrid power system configuration based on the objective of minimzing the levelized cost of electricity of the system. Case-study results from a location in Marseille, France show that the cost of electricity could reduce by around 60\% by shifting from purely diesel based electricity generation to a hybrid power system comprising of airborne wind energy, solar PV, batteries and diesel.
Title: Optimization of a Multi-Element Airfoil for a Rigid Airborne Wind Energy Kite
Authors: Agustí Porta Ko; , Sture Smidt; Roland Schmehl 1 and Manoj Mandru
Affiliation: 1 Delft University of Technology, 2 Kitemill AS
Abstract: Airborne wind energy (AWE) systems benefit from a high lift airfoil to increase the power output, to that end, multi-element airfoils are investigated for AWE applications. This paper aims to design through
optimization a multi-element airfoil for a rigid AWE kite that operates in a pumping cycle or ground-gen. Since the kite has distinct operational phases, i.e., reel-out and reel-in phase, the airfoil design
must take into account the different design objectives for each phase. The airfoil is first optimized for reel-out or production phase and then it is adapted for the reel-in or return phase requirements by modifying its flap setting. The optimization is performed through a multi-objective genetic algorithm coupled to MSES as the aerodynamic solver. Once the multi-element airfoil has been optimized, its
aerodynamic performance is verified through CFD RANS simulations, computed with OpenFOAM. The resulting airfoil offers a satisfactory performance for production and return phase; and the CFD verification shows a fairly good agreement in terms of lift coefficient although the drag has been significantly overpredicted by MSES.
Title: Fast aeroelastic model of a leading-edge inflatable kite
Authors: Oriol Cayon Domingo; , Mac Gaunaa; Roland Schmehl
Affiliation: 1. Technical University of Denmark, Department of Wind Energy, 4000 Roskilde, Denmark
2. Delft University of Technology, Faculty of Aerospace Engineering, 2629 HS Delft, The Netherlands
Abstract: Membrane kites used in airborne wind energy (AWE) function as a morphing structure whose shape depends on its aerodynamic loading and vice versa, posing a complex fluid-structure interaction (FSI) problem. Due to this complexity, kite design is usually done on an experimental basis since no model meets the requirements of being both accurate and fast. This paper presents a fast aeroelastic model of leading-edge inflatable (LEI) kites for the design phase of airborne wind energy systems. The FSI methodology couples two fast and modular models; a particle system model of the wing and the bridle line system \cite{Poland} and a 3D nonlinear vortex step method (VSM) coupled with viscous 2D polars. The aerodynamic model has been validated with several geometries proving to be accurate and inexpensive for pre-stall angles of attack. The coupled model has been validated using experimental data showing good agreement in the deformations and aerodynamic forces. Therefore, the speed and accuracy of this model make it an excellent foundation for a kite design tool.
Title: Ring Kite Turbine Systems with Tensile Rotary Power Transmission – Modelling, Analysis and Improved Design
Authors: Oliver Tulloch; Hong Yue; Abbas Mehrad Kazemi Amiri; Rod Read
Affiliation: University of Strathclyde
Abstract: A rotary kite turbine designed to use tensile rotary power transmission (TRPT) has a stable lifting structure, less tether drag and is easier to automate for larger deployments. In this work, a modular framework model is developed for this airborne wind energy (AWE) system. The ring kite turbine model includes power extraction, power transmission and the ground station, among which the TRPT system is the core component in power transmission. Models with different levels of complexity are proposed for TRPT, one steady state model and two dynamic models with spring-disc and multi-spring representations, respectively. To assess the torque loss on TRPT, a simple drag model is written for the steady state TRPT, followed by an improved model for the dynamic TRPT. The modular framework allows for multiple versions of the rotor, tether aerodynamics and TRPT representations. The developed models are validated by experimental data, then comparisons are made over a range of modelling options. Impacts of TRPT design, rotor design and tether drag on the kite turbine operations are analysed using a steady state analysis. Improved designs are discussed through multi-parameter optimisation based on steady state performance.