Ampyx Power’s Quetzalcoatlus Project
Written by Edward Fagan
Airborne Wind Energy Systems (AWES) have the potential to expand the global wind energy resource by tapping into higher altitude winds than traditional turbines can feasibly reach. However, to achieve this goal at a scale relevant to global energy production over the coming decades, requires a race down the cost curve for this emerging technology.
The Quetzalcoatlus project has been set up to achieve low-cost manufacturing for the wing structure of the next generation of Remotely Piloted Aircraft (RPA) for the Ampyx Power AWES. The project involves a strategic partnership of five enterprises and two universities. The companies involved represent various parts of the supply chain, from design (Ampyx Power) and simulation (Siemens Digital Industries Software) to manufacturing (SABCA, Stellar Space Industries, InfraCore Company). With the two universities (National University of Ireland Galway, Ghent University) providing support with numerical modeling of manufacturing processes and mechanical behaviour of the materials. Additionally, material testing is provided by Composites Testing Laboratory (CTL) and Techspert, and engineering and project management support by 6Synct Consulting Inc.
A lightweight structure made of advanced materials is needed to meet the performance requirements of the RPA wing At the same time, the AWES structure must be competitive with traditional wind turbines, eventually meeting similar CAPEX targets. A major advantage of airborne wind energy over traditional wind turbines is a more compact system, which can result in reduced installation and maintenance costs. Nevertheless, the long-term challenge is to advance the design and manufacturing of the aircraft towards aviation standard at a cost close to that of a wind turbine blade.
The project uses a multi-scale analysis approach to tackle this problem. First, a high-level concept design of the wing structures identifies the geometry, loading, and design requirements for material selection. Coupon-scale material modeling is then supported by a testing campaign to characterise the material parameters. The wing concept is assessed in two ways: (i) the manufacturing processes are modeled and tested on a scaled, 3-m long, section of a wing and (ii) key structural elements are modeled and tested under static, fatigue, and impact loading conditions. The analysis results feed into the detailed design of the wing and provide a baseline set of data for aerostructure acceptance. All of this is within the new regulatory framework set out in EASA’s recently defined safety of operations approach for Unmanned Aircraft Systems (UAS), Regulation (EU) 2019/947.
The concept design phase explored novel manufacturing approaches, from applying the InfraCore© oblique layered structures technology to a wing, to 3D printing of wing-fuselage interface components. A technical cost model was also developed to support techno-economic analyses of various manufacturing approaches. The concept for a low-cost wing construction was developed here in collaboration with the project partners.
A techno-economic study identified cost savings for the wing composite structures through a combination of structural analysis and cost modeling. Out-of-autoclave prepreg manufacturing and vacuum assisted resin infusion were compared, with an eye towards long-term automation of the fabrication process. A trade-off study of over 100 materials found the optimum material based on mechanical properties (resin strength, fibre strength/stiffness), material unit costs, and manufacturing characteristics (curing profiles, glass transition temperature). Advanced material modeling is at the core of the Quetzalcoatlus development work. The selected material is now undergoing a novel material testing campaign to characterise both interlaminar and intralaminar mechanical properties for static and fatigue loading conditions. Siemens Simcenter 3D will be used for the Parameter Identification (PI) process to support multi-scale modeling of the wing. An optimized PI procedure, aimed at reducing material testing efforts while determining the material behaviour, is also being developed.
In addition to the material characterisation work, the wing production demonstrator is currently being designed. The features in the demonstrator wing will provide insight into reducing the overall cost of manufacturing and assembly of the RPA wing, as well as the design of features for long-term maintainability. The demonstrator will be produced in two parts via resin infusion, with the entire lower wing surface, spars, and stringers infused in one-shot. Quality inspections, assembly, and integration trials, and non-destructive inspection (NDI) of the demonstrator will provide invaluable lessons for the design teams.
The next stage of the Quetzalcoatlus project is to design, model and test the key structural segments (i.e. design features) under a variety of loading conditions. The computational damage models developed at the coupon level will be used to define mitigation strategies for extreme loading conditions on the airframe. The assessment of both production method and structural design will advance the design methodologies for the team as they begin detailed design of the full-scale wing.
Ultimately, the Quetzalcoatlus project will lead to the development of a commercially viable low-cost wing structure for the first commercial Ampyx Power system, with design for safety and performance as it’s driving ideology.
This project is supported by Interreg NWE (MegaAWE project) and by Science Foundation Ireland under Grant number 18/IF/6362.
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