Wind turbine inspection

Eloise McMinn Mitchell, Flyability 

Safer and faster inspections of some of the biggest wind turbines in America

Wind energy is one of the original forms of power generation, seen early in windmills and agriculture. Now, wind turbines are helping to power the planet. In 2022, 7.33% of global energy was generated by wind. However, wind turbines are incredibly complex to build, transport, and inspect.

Production worldwide is moving incredibly quickly, but a single blade for a land-based turbine can be over 170ft (52m). The largest wind turbine in the world, the Goldwind GWH252-16 MW, has a turbine rotor diameter of 827ft (252m) and its hub stands at 479ft (146m). The large size of turbine blades makes them incredibly difficult to mount, and the process of inspection and maintenance is also complex.

Inspectors have been trying to find safe ways to inspect turbines before and after they go into operation. These inspections can be used to ensure the lightning protection built into the turbines is correctly configured, as well as ensure there are no cracks or degradation inside the turbine. There can be a risk of grease or missing bolts inside the blades that can be dangerous if it builds up, or, in a lightning strike, if it ignites.

The Elios 3 is being used by a specialised robotics and drone inspection company, Pathfinder Optics, to enable safer and faster inspections of some of the biggest wind turbines in America.

Developing drone inspections for the renewable energy industry

Wind turbines are helping to power the planet – in 2022, 7.33% of global energy was generated by wind.

The client uses a fleet of various robotics and drones to conduct inspections across multiple industries, this includes wind turbine inspections. Using the lidar capabilities of the drone, in addition to the visual feed, its inspections are much safer and faster.

How drones can be used for wind turbine inspections

Initially, a rotary drone without an exoskeleton-like cage for inspections at wind turbines was used, but the protective structure of the Elios 3 drone’s cage helped with movement inside the small spaces of turbine blades, while the lidar and visual data provided key data needed for inspections.

Right: The small area from where there is access to the separate wind turbine blades.

The drone flies inside the wind turbine blades.

For a recent project, where four turbines were inspected at site, it was necessary to climb up to the hub of the wind turbine – the space between all three blades – and conduct inspections inside each blade. Before climbing up, each turbine was turned off and all blades were stationary.

The first challenge was access. It meant climbing up a ladder to get to the hub while carrying the drone. At some sites, it is possible to winch the drone up simultaneous to the climb using cables.

Once inside the hub, which is an extremely small space, there is access hatches to each of the turbines. Each blade can be flown within one battery life as the drone is navigated 220ft down the structure before returning. Once all blades have been inspected, the drone and the pilot can return to the ground. With this method, four turbines in one day can be inspected, faster than traditional methods, where one turbine a day can be the maximum operational speed.

Drone benefits for wind turbine inspections

The visual and lidar surveys conducted are critical for monitoring the status of wind turbines. The hub holds technical infrastructure and a condition monitoring system (CMS) to manage the wind turbine, including how the blades are pitched and how they turn. However, this CMS cannot monitor the blades themselves as these are made of fibreglass. If the blade is for some reason damaged, the CMS cannot determine why or how. This is when inspectors will have to respond to a fault.

A single blade being destroyed or significantly damaged can cost over $1m to replace. This huge cost can be averted if inspections provide information prior to a problematic event. An example of a problem like this could be lightning. Turbines typically have a lightning protection system in place that includes metallic conductors placed along the edges of the blade and connected to the hub.

However, if these are not correctly configured, the blade can explode in a lightning strike, or catch fire. If there is a build-up of grease in part of the blade when this happens, the explosion can become even more serious.

Using the drone can help identify manufacturing defects, potential hazards or be used for emergency response should the worst happen and report these back to the wind turbine owner or manager. It can then take quick action to conduct maintenance or organise a planned replacement, which is significantly cheaper than a replacement of $1m or more.

Wind turbines also have to be inspected every year or twice a year, depending on the local regulations. This used to require a person to have to step out and walk inside the blades or crawl inside them. This was a huge fall risk and presented a major problem for turbine owners.

Bringing modern drone technology to renewable energy

Efficiency and safety has been huge benefits. It is a challenge for anyone to inspect wind turbines, as there can be a fear factor as well as a major fall risk. The drone ensures the inspector can remain safely in the hub and be harnessed down without having to crawl into the turbine blades.

The client has since completed projects all along the West Coast of the USA. Using the drone is not only safer for inspections, but helps the wind turbine owners save costs and avoid lightning damage. 

Eloise McMinn Mitchell, Flyability

www.flyability.com

@fly_ability

All images courtesy of Flyability.