Variable Cross Section Tether for Airborne Wind Energy
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Solution Overview
Problem
Current tethers for airborne wind energy systems contribute significantly to drag and weight, affecting system performance and cost, and existing designs do not effectively account for drag distribution and thermal management.
Innovation Solution
A variable cross-section tether design that changes thickness and shape along its length, with a smaller cross-sectional area near the airborne device and a larger area near the ground attachment, optimizing drag, weight, and thermal performance by distributing drag and weight more efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a uniform cross-section tether is used, then the tether maintains consistent strength along its length, but the tether experiences excessive drag and weight
Solution Approach 1:
The tether employs varying cross-sectional dimensions along its length, with the diameter or width changing from the first end to the second end. This local variation allows each section of the tether to have optimized properties for its specific location, reducing overall drag while maintaining necessary strength at critical points.
Solution Approach 2:
The patent applies parameter changes by modifying the cross-sectional dimensions (diameter, width, or area) as a continuous or discrete function along the tether's length. This parameter variation optimizes the balance between strength requirements and drag reduction, allowing the tether to adapt its properties to local conditions.
2Force
If a thicker tether is used near the airborne device, then the tether can handle higher loads, but the overall drag and weight increase
Solution Approach 1:
The tether is designed with non-uniform cross-section where the dimensions vary along the length. This allows the tether to concentrate material where loads are highest (near the airborne device) while using less material in regions where loads are lower, thereby optimizing the weight-strength tradeoff.
Solution Approach 2:
The tether can be viewed as segmented into multiple sections with different cross-sectional properties. Each segment is optimized for the specific load conditions it experiences, with the transition between segments creating a gradual or abrupt change in dimensions that matches the load distribution profile.
3Loss of energy
If the tether cross-section is reduced, then drag and weight decrease, but thermal management becomes more difficult
Solution Approach 1:
The varying cross-section allows different portions of the tether to have optimized thermal properties for their local conditions. Sections with higher thermal loads can maintain larger cross-sections for better heat dissipation, while sections with lower thermal loads can be thinner to reduce drag.
Data Source
AI summary
The exemplary embodiments herein provide a tether for use with an airborne device, where the tether contains an elongate member having a first end for attaching to a ground attachment point and an opposing second end for attaching to the airborne device where the elongate member has a cross-sectional area which varies across the member. In some embodiments, the tether contains one or more electrically conductive elements, an optional strength element, insulation separating any adjacent electrically conductive elements, and a jacket which surrounds and protects each of the tether components.