Currently, wind turbines available in the market are providing a nominal power of 5 MW with the length of the blades in the order of 60 metres. Future applications will require significantly longer blades so the industry will be facing tremendous challenges in manufacturing, transport and assembly operations.
Developing technologies that allow not only manufacturing blades in sections, but also their easy assembly at the erection site, will help overcome these challenges.
INDEOL has developed a double T-bolt joint system for wind turbine modular blades. It comprises two parallel cross bolts that pass through the laminate of each blade section, and two fastening bolts that connect the two cross bolts at both sides of the laminate.
In addition, different mechanical solutions are provided between the fastening bolts and the cross bolts in order to ensure proper torque tightening for each blade design.
The joint system defines an advantageous connection for modular blades that offers some benefits, among others:
- At the connection portion, there is no reduction of the working area of the laminate which, in consequence, will not be weakened.
- Symmetric loads and moments are achieved.
- A pre-stressed connection is obtained, which helps reduce the stresses affecting the metallic components, therefore fatigue resistance is improved.
- No adhesives are used, hence defects and uncertainties related to bonding connections are avoided.
- Assembly, inspection and maintenance tasks can be carried out from the outside of the blade.
- Maintenance frequency will be reduced, and it will only be determined by the selected mechanical solution between the fastening bolt and the cross bolt.