Further tests and field trials are planned of an optical inspection technique that can detect sub-surface defects such as cracks, delamination and impact damage in wind turbine blades
Scientists involved in the Winspector project, which uses a non-destructive inspection technique known as laser shearography to inspect turbine blades, are pressing ahead with the next phase of a project they hope could enable them to commercialise the technology in the offshore wind energy industry.
Progress to date with the EU Horizon 2020-funded project suggests a robotised system incorporating laser shearography has great potential in the onshore and offshore wind energy sectors.
The scientists hope they will be able to commercialise the technique, integrating it into a remote-controlled robotic system that can be used to inspect blades without requiring time-consuming, expensive and potentially risky rope-access by windfarm technicians. In an onshore windfarm the system would be remotely controlled from the ground; on an offshore windfarm, the robotised system would be operated remotely by engineers on a vessel.
Laser shearography works by applying stress, in the form of a thermal pulse, to the part of a blade being inspected and recording the distribution of the strain on the tested area using a shearing image interferometer in a shearography camera. By analysing the derivatives of the strain distribution, discontinuities can be observed.
Shearography has long been recognised as a powerful inspection technique and is widely used in other industries, including aviation, the automotive sector and shipbuilding, but requires a stable platform and human intervention. The challenge the partners in the Winspector project have been addressing is how to integrate the technology into a robotised system rugged enough for use in the field, on a wind turbine, and ultimately for use offshore, without manual intervention by an operator. One of the biggest potential advantages of shearography is that it can ‘see’ beneath the surface of a structure inspected. The partners in the project say it can inspect a blade to a depth of up to 50 mm.
In an earlier phase of the project, the two main subsystems in Winspector, the shearography system and the robot platform, were developed and successfully tested separately and then in an integrated system. In 2019, tests were carried out on a turbine by The Welding Institute (TWI), London Southbank University, WRS Cathodic Protection Systems, IKnowHow and wind turbine manufacturer Siemens Gamesa Renewable Energy. TWI and the project partners are planning a further series of field trials in association with EDF Energy, to demonstrate the potential of the technology on larger turbines and blades.
TWI research scientist Jianxin Gao told OWJ that following the latest phase of the project, which saw field trials successfully undertaken at the Centre for Renewable Energy Sources (CRES) in Greece on an onshore wind turbine, new funding has been secured for a further series of demonstrations in association with EDF. “We haven’t conducted any tests offshore yet,” he explains, “but in the next phase of the project we plan to test new hardware and software as we work towards commercialisation.
“In 2019, we completed two successful field trials at CRES,” TWI’s research scientist told OWJ. “The trials demonstrated that our overall approach of using shearography with a robotic system for blade inspection definitely works. The next phase of trials is a further step in the direction of demonstrating the technology and, ultimately, commercialising it.”
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