Checking out the turbines

The role has traditionally been accomplished from the ground using simple visual inspections or by more complicated and risky techniques such as using a cherry picker, service platform, hydraulic crane or rope descent.

The quick and efficient scanning of land, building sites and large machinery by UAS (Unmanned Aerial Systems) presents not only a far safer method of inspection but a more effective view of operations, offering a new perspective from which issues and faults can be detected.

Thermography (otherwise known as thermal imaging) uses infrared-sensitive cameras to inspect buildings, electrical equipment and rotating machinery to find faults associated with heat loss or gain. Infrared cameras have developed significantly over recent years: modern thermal imaging cameras are now so small they can fit in the palm of a hand. These smaller and significantly lighter infrared cameras are ideal for integration with UAVs.

UAV IR cameras for the oil, gas and utility industries are already in service, providing exceptional results in areas previously considered impossible to survey.
The first foray for drones into the renewables market was not with wind turbines, but with photovoltaic solar panels. A need for inspection is becoming increasingly essential as the use of solar energy is expanding both domestically and commercially. Solar panels are highly sensitive pieces of equipment that require periodic maintenance in order to replace or repair damaged panels, in order to improve efficiency.

Pairing aerial capabilities with thermal imaging techniques allows the inspection of PV systems in remote areas, meaning rooftops and large buildings can easily be assessed. Employing infrared technology and high definition imagery makes it possible to find damaged cells, survey large solar farms and monitor the overall effectiveness of energy production.

As the wind energy industry matures, a growing number of wind turbines are operating out of warranty and must be serviced more frequently to maintain productivity and avoid downtime. Preventative maintenance by inspecting blades before a blade failure actually occurs costs 25% less than reactive maintenance, while predictive maintenance costs 47% less. This is driving a brisk business in wind turbine blade inspections.

Optimum distance

Commercial-grade UAVs handled by professional operators provide closer, higher-resolution imagery than ground-based alternatives and are also significantly quicker. UAVs are able to fly at an optimum distance from the structure, usually from 3 to 10m, and can circle around it to cover the whole surface area. This data can then be used in conjunction with photogrammetry software and used to build a three-dimensional model of the blade, delivering a level of accuracy and detail that is hard to achieve with manual methods. When and if repairs are needed, the team knows the exact location on the turbine. Because it is GPS enabled, it also points to the repair’s exact location.

Inspection of wind turbines using drones combines visual and infrared techniques. While inspection of the main tower is primarily a visual job, thermography can play a useful supportive role in examining nacelles and the turbine blades themselves. Nacelles house the mechanics of the turbine, including the gearbox, generator, brake, controller and yaw mechanism. Thermography can be used to identify areas of the blade which are delaminating, as they can detect variances in the heat of the blade structure.

Naturally, companies who can provide a combination of both visual and infrared inspections have a competitive advantage. iRed is one such company and it reports a growing number of people from the wind turbine inspection business booking onto its thermographic training courses.