In the picture on turbine issues

The Irish Wind Energy Association has confirmed that as of March 2013, 1763MW of wind energy is being generated in Ireland, sufficient to power 1.14 million homes.  Indeed in 2012 alone, the capacity was boosted by 124.59MW. To meet its binding EU 2020 targets this commitment will certainly increase. 

As much as 25% of the total cost of producing electricity from a wind turbine can be attributed to maintenance, and the lion’s share of turbine failures is caused by poor electrical connections and components. Electrical steering and rotor blade faults are also cited. So efficient and reliable methods to monitor and assure predictable turbine performance are vital to the economics of this source of renewable energy.

Predictive maintenance

The safe operation of a wind turbine is of paramount importance and its braking mechanism and gearbox are two of the most critical components as they control rotation speed. The load on the blade tips increases with speed and if left unchecked the blade will ultimately fracture from the rotor, propelled by an enormous amount of kinetic energy and momentum. This can be life threatening.  

The predictive maintenance of these components and the entire electrical system that powers them is the perfect application for thermal imaging.  An abnormal heat profile is a sure sign of a fault such as a worn bearing or a bad connection.  The technology also pinpoints the location of the problem so swift remedial action can be taken.

The wide choice of camera models available provides the means for wind turbine maintenance crews to perform non-contact, non-destructive testing at close range or over a considerable distance with a high resolution model. Cameras are designed to be as compact and lightweight as possible and easy to use. Both are important qualities when the operator has to climb many metres to conduct the inspection.

Another important factor is the lens. A wide angle lens allows larger pieces of equipment to be imaged in one go and also at close range. Various software features speed up the inspection process. FLIR Systems’ Panorama intelligent image stitching, for example, allows the instant creation composite image that is fully radiometric.

Complementing the portable thermal imaging cameras are fixed mounted models that are designed to keep the thermal efficiency of installations in constant check. Models are available that are both GigE Vision and GeniCam compatible, a feature that cuts down integration time significantly.

Non-destructive testing

Electro-mechanical infrared inspection falls into the category of passive thermography which can be applied to every component that produces heat during operation. As well as the driveline it’s suitable for monitoring the health of critical electrical components such as a high voltage transformer or a cooling fan in the nacelle.  

But what about components that don’t produce any heat - such as a rotor blade – can thermal imaging help here?  The answer is yes and the proven method is active or pulse thermography.

This technology is mainly employed to see defects on a qualitative basis.  As the structure doesn’t produce heat itself an external heat source is applied enabling the thermal imaging camera to obtain a radiometric reading.

In the field of wind energy pulse thermography is commonly used to detect areas of delamination on GRP rotor blades.  A correctly laminated composite material structure will have relatively uniform thermal characteristics.  Once a disbond or delamination has occurred, the thermal pattern within the composite will be altered and detected by the camera. 

Thermal imaging has proved its ability to reduce the time and effort involved in scanning large scale objects and allows the detection of defects instantaneously, on site, without having to disassemble the blade.