Project context and objectives

Wind energy is an increasingly important contributor of power within the renewable energy sector. In recent years, there have been an increasing number of reports of defective blades contributing towards turbine failure. At present, regular inspections are conducted on turbine blades to ensure structural integrity and prevent degradation due to fatigue or impact. These programmes of routine inspections prevent breakdown or catastrophic failure but at significant cost. Within the larger blade designs, there exists a complex composite structure of glass fibre reinforced plastic (GFRP) together with other materials. Since the area requiring inspection is large and the material (composite) is complex, existing inspection methods are costly, unreliable and labour intensive. The objective of the WinTur project is to focus on the development of a structural health monitoring system (SHM) for the purposes of incipient defect detection on wind turbine blades. Application of an early warning system will extend the blade life-expectancy, lower maintenance costs and optimise the efficiency of energy delivery to meet industry and community demands.

The WinTur project is a collaboration between the following research organisations and SMEs from 6 different EU countries: TWI LIMITED, OPTEL sp.Z o.o.,SMART MATERIAL GmbH, CEDRAT Technologies, MIYAMA COMPOSITES Ltd,ENCOCAM Limited, SOLENT COMPOSITE SYSTEMS Ltd, SCOTTISH&SOUTHERN ENERGY, CERETETH, KAUNAS UNIVERSITY OF TECHNOLOGY.

The objective is to design a structural health monitoring system that integrates two technologies – a novel application employing Acoustic Emission and Long Range Ultrasonics – into one dual-action sensor. The advantage of this system is that AE passively detects the onset of composite deterioration whilst LRU actively interrogates the structure. System management reports the status of the blade to the user for high-level decision making.

Work performed to date and main results

The main results of the complete WinTur SHM system were:

1. Successful development of a dual-purpose sensor array using AE and LRU to successfully detect defects with good sensitivity. The final trials proved that the WinTur developed technology is able to detect
   • Growing defects up to a distance of 3.8m
   • Blade intrusive-damage down to a thickness of 2mm
   • Impact damage up to a distance of 800mm
2. Signal processing analysis tools – cross correlation techniques and averaging – for defect detection and localisation
3. Wireless communications for data transfer up to speeds of 2Mbits per second in 20 seconds maintaining 100% signal integrity.
4. Two energy harvesting systems
   • Amplified Piezoceramic Actuators able to charge the harvester to 5.6V for a 150Hz vibrations of 150mV amplitude with a storage time of 13s.
   • MFCs able to generate 0.5mWs per deformation cycle at 0.5Hz - able to power the transmission of 8 datagrams to a receiver node over a distance of 150m
5. A GUI provding signal visualisation, a visual status indicator, easy-to-use navigation tools, tabulated display of critical information and a reporting facility
   

Final results and potential impacts

The WinTur project has been very successful and achieved all of its objectives. The field trials carried out on the wind turbine blade confirmed that the SHM development is an effective and reliable inspection device. It is a unique system that can perform quick and simple inspection of composite components.

The benefits of fitting an SHM system (such as WinTur) are acknowledged by the industry. The system is suitable for application on both onshore and offshore wind turbines. There is almost unanimous recognition throughout the industry sector that offshore wind turbines are ideally suited to SHM. A monitoring system such as that developed by the WinTur consortium can contribute significantly by providing autonomous blade inspection.