Tue, 28 July, 2020
TWI has been working as part of a consortium on the BladeSave Project, developing a condition monitoring system for wind turbine blades.
Bringing together expertise in structural health monitoring, fibre optic sensing technologies and management software, the project aimed to deliver a comprehensive system for the monitoring, repair and management of wind turbine blades.
TWI project leader Linghao Zhou explained more about the project:
Can you start by introducing yourself, your area of expertise, and how you ended up working at TWI?
I am a project leader in the Monitoring and Inspection Research Section. I have a PhD in machinery faults diagnosis using vibration analysis. My current work is focused on delivering EC funded projects by applying machinery condition monitoring and structural health monitoring techniques.
I joined TWI in early 2018. TWI attracts me as a world-renowned research and technology organisation, leading in material joining, engineering processes and non-destructive testing.
How did you come to be involved in the BladeSave Project?
BladeSave is a collaborative project funded under EC H2020 programme. It aims to deliver a reliable and cost-effective condition monitoring system (BladeSave system) built with fibre optic technology, providing multi-sensing capabilities including acoustic emission, vibration and strain.
I was first introduced into the project to provide support in conducting vibration resonance testing. The aim of the testing was to simulate ice build-up on leading edge of the wind turbine blade, and to detect the faulty condition using BladeSave system. I was subsequently involved in blade destructive testing later on.
Can you explain why it is so important to monitor wind turbine blades?
Wind energy is a clean and sustainable renewable energy source, which is expected to provide the largest contribution to EU’s 2020 renewable energy targets. However, the reliability of wind turbines is a pre-requisite to ensure the healthy growth of wind energy, and ascertaining the integrity of the wind turbine blades is the critical issue for reliability.
Wind turbine blades are susceptible to fatigue failure and adverse environmental effects. It is most desirable for wind turbine owners to be aware of the health conditions of the turbine blades at all times, in order to make cost-effective maintenance decisions. For instance, undiscovered early blade defects can continuously develop, leading to blade failure eventually and surprising downtimes. The cost could have been minimised had defects been monitored, so that maintenance actions could take place proactively.
How does the BladeSave project solve this problem, and how does it differ from other solutions?
The solution that BladeSave provides is a complete condition monitoring system designed to continuously monitor the condition of the wind turbine blades. The system utilises Fibre Bragg Grating (FBG) sensors to measure AE, vibration and strain during blade operations. The collected data is pre-processed in a local computing unit, which will then send the pre-processed results to the blade management software for final processing and reporting. The BladeSave system can operate 24/7 autonomously, so that the operational condition of the blades are always being monitored. What’s more, the incorporation of the AE technique has increased the system’s capability to detect early stage cracks formed on the blade.
The system makes use of fibre optics; can you explain how these work and what benefits they offer?
The fibre optic system is composed of interrogator and fibre optic sensors. The sensors are calibrated to reflect light of a certain spectrum. When the optical length of the interferometer in the sensors is affected by AE, vibration or strain, the reflection received in the interrogator will shift accordingly. The interrogator can then translate the changes into the physical measurements of interests.
The benefits are substantial. The sensors are immune to all electromagnetic effects. The system facilitates remote sensing, as the cables can be extended to kilometres without suffering much signal loss. The system also offers multiplexing using optical switches.
What’s next for the project, and when can we expect to see the completed system ready for commercial use?
The project is coming to its final stage of testing and reporting. We are looking forward to the fatigue testing hosted in TWI’s facility, to demonstrate the BladeSave system’s capability of monitoring early stage blade crack and its propagation with AE technology.
The vibration and strain monitoring functions are already available for commercial applications. Once the fatigue testing is finished, AE functionality will also be fully validated.