Nowadays, Wind Turbines (WT) are one of the most efficient ways to produce green and sustainable energy, contributing in a high percentage to all renewable electricity. However, due to the stress suffered by the blades and caused by wind gusts, there is a continuous need for inspection and maintenance. According to CWIF an average of 3,800 blade failure incidents annually are attributed to poor maintenance, with a cost varying between 90,000€ and 900,000€ each, involving many of the accidents human injury and fatalities. Blades reparations can be costly in downtime and expensive, and at the same time this fact reduces turbine’s operational efficiency. For these reasons, preventive planning through more frequent inspections is a necessity.
To achieve a thorough investigation for defect presence on a wind turbine blade, close inspection is required. Current inspections carried out in wind turbine blades, like visual examination or Non - Destructive Testing (NDT) inspections such as thermography, acoustic emission or ultrasound, require skilled personnel or “workshop environment”. This implies either trained staff tied with ropes on the blade or dismantling and transferring the blade in a workshop environment. While blade dismantling is scarcely used because it requires very long downtime, human inspection also involves a relatively high delay.
Approach to the market
A solution to this problem is to utilize specially designed platforms that can reach the blade and implement faster inspections on site. However, current systems are not very agile or cannot reach close enough to the blade in order to use a high quality non-destructive technique. Hence, they are mostly used to carry out mere visual inspections. There is not an integrated solution that offers a good inspection quality, human safe and efficient way of inspection.
To deal with the aforementioned challenge, our team has come together to propose WInspector, an innovative system consisting of an agile robotic platform able to climb up the wind turbine tower and deploy an advanced Digital Shearography (SD) kit that carries out the inspection of a blade at a depth of up to 50mm.
WInspector consists of a robotic deployment platform and an advanced NDT inspection system (Figure 1). The robotic platform climbs up vertically along the wind tower and carries the inspection system in a small movable platform. Its arm is capable to place the NDT equipment at the desired position, providing the required stability for the NDT inspection.
The NDT inspection of the composite Wind Turbine Blades is carried out by a shearography system. This technique allows the measurement and qualifying of complex geometries quickly and efficiently. An appropriate stress, a thermal pulse in this case, is applied on the inspected part of the blade, and at the same time the distribution of the strain on the tested area is recorded using a shearing image interferometer included in the digital shearography camera. By analysing the derivatives of the strain distribution, any discontinuities are observed.
Figure 1. Shearography Unit and robot platform
The project aims to further develop and commercialize the WInspector system which consists of an agile robotic platform and an advanced digital shearography kit. The robot platform will be able to climb up the wind turbine tower so that the shearography system can carry out inspection of a blade for potential subsurface defects. The whole system will be operated by engineers on the ground or a vessel for on-shore or off-shore wind farms.
Users of WInspector benefit through early detecting emerging defects unseen in a visual inspection performed by competing solutions, with a significantly lower downtime for the WTB, and free of the risks of humans working at height.
Scientific and technological objectives
The two main subsystems of WInspector, the shearography system and the robot platform, have already been developed and tested both separately as well as an integrated system (TRL6). The work that will be carried out will have as main objectives the optimization and testing of the shearography system and the robotic platform to improve detection accuracy at working conditions, making the shearography software more user friendly, estimating the target production cost per unit, obtaining the certification of the integrated system required for wind turbine inspection equipment, establishing a distribution network for the introduction of WInspector to the market carrying out several demonstrations in different places.