The CORTIR III Project: Cost and Risk and Trailing Edge Innovative Reinforcement (pr. no. 640232-511715)
This project headed by Bladena is a continuation of CORTIR Phase II, with a primary focus in minimizing Operational Expenditure (OPEX) of wind turbine blades and maximizing the Annual Energy Production (AEP) of wind turbines, using a risk based approach. The CORTIR III project is supported by the Energy Technology Development and Demonstration Program (EUDP), which is administered by the Danish Energy Agency.
The lack of quantification methodologies in determining the effects of torsional loads result in increased OPEX due to downtime because of unexpected repair campaigns. When it comes to offshore wind turbines, where the access is limited compared to onshore sites, and as the limitations on vessel availability and weather conditions is also limited, the downtime issues are more challenging and the OPEX costs are much higher. As both the failure rate, due to larger, heavier blades installed in offshore sites, and the consequent cost of downtime are inflated in offshore wind farms, there is a need to both reduce the uncertainty during the design phase for future blades and to develop a permanent solution that mitigates trailing edge issues for blades in operation.
This track of the project will focus on assisting the validation process by field measurements during operation. The chosen approach is to use the collected measurements from the first phase of the field demonstration. The methodology followed during the project will initially include re-engineering of the FEM model of the selected blade. FEM simulations will provide the baseline in terms of out-of-plane deformations, which will then be compared to the real field measurements.
The trailing edge of a blade, especially in the max chord and root transition zone regions, are the most vulnerable areas of a blade. Even though the mid-span region is part of the aerodynamic section of the blade, trailing edge splits can occur due to the increased buckling. Failures in bondlines and cracks along the trailing edge are occurring either due to imperfections or flaws during the manufacturing processes or due to the increased edgewise fatigue loads in longer blades. For blade designs with large flatback trailing edge, the adhesive bondline in the corners are specifically more vulnerable due to the high bending of the pressure side panel. As a mitigation, solution to reinforce the trailing edge is needed.
An additional aim of this project is to establish a framework that ensures that the knowledge gained through any relevant activity is utilized by the WTOs to a level that improves the understanding of the industry concerning wind turbine blades and their structural issues. Inspired by more mature industries, e.g., Civil Engineering, Aircraft, Naval Architecture and Oil & Gas, such as a knowledge framework can be established by following similar methodology but adjusted to the specific pre-requisites in the wind energy industry.
As blades grow larger, the need of realistic f remaining lifetime prediction of a blade is increasing. The “expected” 20-30 year lifetime stated by the manufacturers is in many cases not realistic as this claim is not validated through sufficient test campaigns. Failure mode drivers have kept changing historically, with torsional loads being one of the new main drivers for the current commercially available blades, changing the currently occurring failure modes compared to what was occurring a decade ago. Therefore, the approach both in the design phase and in the decision-making regarding the operation and maintenance strategies is a dynamic process which has no guidelines set in stone over the years.
CORTIR - (Cost and Risk Tool for Interim and preventive Repair)
The project aims to cope with the various challenges of the appropriate operation and maintenance strategies. A Cost and Reliability Tool (CAR Tool) will be developed. The vision of this project is to make the decision-making process regarding operation and maintenance decisions easier and to support the entire value chain on how to minimize risk, operation and maintenance cost.
CORTIR Phase II - Cost, Risk and Transition zone Innovative Reinforcement
The main deliverables are a new retrofit solution designed for high forces in the Root-Transition Zones (RTZ) of blades, a new innovative state-of the art operation and maintenance strategy and lastly further developments of the Cost and Risk Tool (CAR Tool).