Modular Wind Turbine Blade Joint With Non-Uniform Spar Cap Tapers
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Solution Overview
Problem
Modular wind turbine blades face challenges in load transfer due to split spar caps at module joints, which are difficult to manufacture and assemble accurately, and require long, shallow tapers to distribute loads effectively.
Innovation Solution
A modular wind turbine blade design with spar caps and connecting elements featuring non-uniform tapers, where inner and outer thickness bands have lower taper rates than the intermediate bands, allowing for a shorter joint span and improved load distribution, facilitating easier assembly and transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the spar caps are configured with a very shallow taper (1:100) to gradually transfer loads and provide large bonding surface area, then the load transfer is improved, but the joint length increases to over 10 meters making it difficult to manufacture accurately and challenging to assemble on-site
Solution Approach 1:
The spar cap is divided into multiple discrete blocks along its length. These blocks are connected through bonding interfaces that distribute loads across multiple segments rather than requiring a single continuous long taper. This segmentation allows the joint to achieve adequate load transfer over a shorter overall length while maintaining structural integrity.
Solution Approach 2:
Different regions of the spar cap are given different local properties through varying block dimensions, bonding surface areas, and stacking sequences. The bonding interfaces are designed with optimized local geometries to concentrate load transfer at critical locations while reducing the overall joint length. This local optimization allows effective load transfer without requiring a uniformly long shallow taper throughout the entire joint.
2Reliability
If the spar caps are configured with a very shallow taper to gradually transfer loads, then the stress concentrations at the joint are reduced, but the manufacturing accuracy and assembly difficulty increase due to the extended joint length
Solution Approach 1:
Dividing the spar cap into discrete blocks creates multiple manageable bonding interfaces rather than one extremely long interface. Each block and interface can be manufactured and assembled with standard tolerances, avoiding the cumulative accuracy issues that would arise from maintaining a single 10-meter tapered interface. The segmentation transforms a precision-critical long interface into multiple shorter, more manageable interfaces.
Solution Approach 2:
The spar cap blocks are pre-assembled and bonded in a controlled manufacturing environment where precision can be maintained, rather than attempting to assemble a single long tapered joint on-site. The blocks can be prepared with precise geometries and bonding surfaces before transport, ensuring high manufacturing accuracy is achieved during controlled factory assembly rather than field installation.
3Length of moving object
If the blade is designed as a modular assembly to overcome transportation challenges, then the transportability is improved, but the spar cap structure is split at the joint interrupting the load transfer paths
Solution Approach 1:
The spar cap is intentionally segmented into blocks that align with the modular blade sections. The bonding interfaces between blocks are designed to maintain continuous load transfer paths across the module joints. This segmentation approach allows the blade to be divided into transportable modules while preserving the structural integrity and load transfer continuity of the spar cap through carefully designed bonding interfaces at the module boundaries.
Solution Approach 2:
The bonding interfaces between spar cap blocks act as intermediaries that transfer loads across the module joints. These interfaces are designed with sufficient bonding area and optimized geometry to mediate the load transfer between disconnected spar cap segments, effectively restoring continuity of the load path despite the physical separation at module boundaries.
Data Source
AI summary
A wind turbine blade includes first and second blade modules. The first module includes a first spar cap, and the second module includes a second spar cap. The first spar cap has a tapered end portion where the thickness decreases towards the end of the first spar cap. The blade further includes a connecting element having a first tapered end portion where the thickness decreases towards a first end of the connecting element. The first spar cap and the connecting element each include (i) an intermediate thickness band; (ii) an inner thickness band; (iii) an outer thickness band. A tapered end of the inner thickness band and/or a tapered end of the outer thickness band of the first spar cap has a lower rate of taper than a tapered end of the intermediate thickness band of the first spar cap.