Tethered Wing System with Flexible Membrane and Bridle
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Solution Overview
Problem
Existing tethered wing systems for airborne wind turbines face challenges in achieving efficient energy conversion across a wide wind range, with limitations in weight, durability, and control, particularly in yoyo operations, due to high surface loads and weight, and inefficiencies in load transfer and retrieval.
Innovation Solution
A wing system combining flexible membrane sections with rigid profile elements and bending torsion beams, utilizing a central bridle line for load transfer and allowing free rotation, and controlled via ground-based tethers, enabling efficient lift generation and stabilization across varying wind speeds without active control mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rigid fiber composite wings are used to eliminate bending torque, then strength and durability are improved, but weight increases to 5-15 kg/kW or 10-25 kg/kW
Solution Approach 1:
The patent applies flexible membrane material to create a wing surface that can adapt to aerodynamic loads without requiring heavy rigid structures. The membrane is tensioned between the leading and trailing edges, allowing it to withstand surface loads of 30-60 kg/m2 while maintaining a weight of only 100 kg/m2 including fuselage and control surfaces.
Solution Approach 2:
The patent employs dynamic tensioning of the membrane through the bridle system, allowing the wing structure to adapt its stiffness and shape in response to varying wind conditions. This dynamic adjustment enables the wing to maintain structural integrity under changing loads without requiring excessive weight for static strength.
2Weight of moving object
If tethered wing designs with surface loads of 30-60 kg/m2 are used, then weight is reduced to approx. 100 kg/m2, but surface area is limited
Solution Approach 1:
The patent divides the wing into modular components including the membrane surface, bridle system, and control elements. This segmentation allows the wing to be scaled in surface area while maintaining the same weight-to-area ratio, enabling larger wing areas to be achieved without proportionally increasing total weight.
3Weight of moving object
If screen designs with surface loads of 3-10 kg/m2 are used, then surface weight is reduced to approx. 0.1-0.2 kg/m2, but load transfer efficiency decreases
Solution Approach 1:
The patent combines the lightweight membrane material with a structured bridle system made of high-strength tensile elements. This composite structure achieves an optimal balance between weight and load transfer efficiency, with the membrane providing aerodynamic surface area while the bridle system efficiently transfers loads to the tether connection points.
4Weight of moving object
If ram pressure wings without rigid elements are used, then weight is minimized, but collapse resistance and retrieval efficiency deteriorate
Solution Approach 1:
The patent introduces the bridle system as an intermediary structure between the membrane and the tether. This bridle acts as a lightweight rigidifying element that prevents membrane collapse under load while maintaining overall system lightness. The bridle distributes loads across multiple attachment points on the membrane, enhancing structural reliability without significant weight penalty.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves a high surface load of 50-150 kg/m2 with a low surface weight of 2-5 kg/m2, allowing for efficient energy generation of 2-10 kW/m2, with improved aerodynamic resistance and reduced energy consumption during retrieval, enabling reliable and efficient operation across a broad wind range.
Implementation Method 1
The flow-induced pressure difference between the stagnation point and along the profile in the flow field is utilized
Implementation Method 2
at least one stable aerodynamic lift surface consisting of one or more membrane sections (laminates, films, fabrics)
Implementation Method 3
one or more bending torsion beams which reduce the surface forces and torques over the profile elements to a main tethering level
Implementation Method 4
connected through one or more tensile elements to a converter unit
Data Source
AI summary
A tethered passive wing system for the conversion of flow energy into electric energy which exhibits optimized aerodynamic and mechanical properties for reliable and efficient operation and is only connected through one or more tensile elements to a converter unit and comprises an optimized combination of rigid, non-flexural structural elements such as, for example, beams and shell structures and flexible fabric structures, such as, for example, membranes, films, laminates.