Combining drones and CMS to transform wind turbine maintenance

Tens of thousands of new wind turbines are being installed around the world each year, as the sector continues to grow at an unprecedented rate. The average and maximum size of blades has increased significantly, with the industry witnessing the widespread deployment of machines between 7MW and 15MW onshore, and as large as 25MW offshore. 

Chinese manufacturer Mingyang, for example, recently unveiled plans for a massive 50MW floating wind turbine. 

Larger blades tend to translate into higher energy yields and increased revenue potential. Nevertheless, they come with higher operational risks, especially when it comes to blade maintenance, catastrophic failures, repair costs, and those associated with turbine – or entire fleet – downtime.  

When blade damage turns into full blade failure costs increase dramatically. Typical repair costs range between $30,000 and $100,000 for onshore and offshore turbines respectively, while blade replacement costs can reach approximately $500,000 for onshore turbines and over $1 million offshore. 

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Blade failures can also result in substantial indirect costs beyond the immediate repair or replacement expenses, including the financial impacts that come as a result of business interruption and long-term reputational damage for asset owners and operators. 

Given the multifaceted value of these assets and the significant cost of unplanned downtime, it is not surprising that wind sector owners and operators are increasingly focused on preventative maintenance strategies. Proactive condition monitoring has become essential, since early intervention is substantially more effective and cost-efficient than reactive repairs or replacements. 

Use of drones  

Inspections using drone technology are one of the most common and widely used blade condition monitoring methods. These are usually conducted once a year, and advances in drone technology have made these inspections very efficient at identifying slow-developing defects that are clearly visible on the external surface of blades. 

Drones have delivered a solid return on investment, especially due to their relatively low cost, and have helped identify damage that might otherwise remain undetected during ground-based inspections. There are, however, certain limitations that must be acknowledged. 

For example, drones are unable to assess all areas of a blade’s exterior and are therefore restricted to detecting a limited number of external failure modes. More importantly, they cannot identify internal defects such as subsurface cracking, structural degradation, or issues within the pitch-bearing. As a result, owners and operators that depend solely on drones will routinely not detect the full spectrum of potential risks and damage.

Drones are also unable to capture changes in blade behaviour over time – an important indicator of potential and emerging issues. These behavioural changes can result from environmental degradation, manufacturing defects, extreme weather exposure, or material fatigue associated with blade age. 

Over the medium- to long-term, these factors can cause increased mechanical stress on components such as the rotor and drivetrain, reduced turbine performance, and, in the worst-case scenario, can lead to blade loss and turbine collapse.

Despite the limitations of drone technology, they do have an inherent value and purpose. Instead of replacing drones, the industry should view them as one of the parts of a broader blade condition monitoring strategy, complemented by a number of systems capable of addressing what visual inspections cannot. 

Making the most of blade CMS  

Blade health assessments can be much more comprehensive if drone inspections are combined with blade condition monitoring systems (blade CMS). This combined approach increases inspection accuracy and provides managers with an all-encompassing and holistic understanding of a blade’s condition.

CMS technologies operating on the inside of the blade – such as vibration and displacement sensors – provide an ideal complement to the strengths of drone-based inspections. 

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Vibration-based CMS identifies anomalies in blade behaviour, including mass imbalance and distinguishes between causes such as ice accumulation and physical damage. One of the main advantages of vibration monitoring is the technology’s capacity to identify the source of an issue with a high degree of precision. With this information, operators are able to implement targeted interventions, reducing downtime, repair time, and associated costs. 

Additionally, displacement-based CMS supports early detection of structural degradation by measuring the smallest internal movements between the hub and blade.

These minute movements are usually imperceptible during visual inspections but can be a sign of serious underlying issues.

In many cases displacement sensors can identify risks up to a year before they turn into a problematic blade issue and enable up-tower repairs instead of full blade replacement saving 90% of the overall cost.

Joining forces 

The wind sector still hasn’t developed a single solution that is able to detect the full spectrum of blade failure modes.

This is not surprising, especially given the broad diversity of contributing factors, from turbine models to manufacturing defects and operational age to environmental conditions. The variety of geographies and climates in which turbines operate further compounds this challenge. 

When blade CMS technologies and drones are used together to monitor blade health, they can provide highly comprehensive and robust tracking of external and internal blade conditions.

Deployed in tandem, the two technologies enable near real-time, end-to-end blade monitoring. This integrated approach offers operators, owners, and asset managers the confidence and clarity needed to protect long-term asset value, reduce risk, and safeguard performance.

ABOUT THE AUTHOR

Alexis Grenon is Chief Executive Officer of ONYX Insight and a seasoned leader in the global energy and technology sectors. Before joining ONYX, he spent nearly two decades at Schneider Electric, most recently serving as CEO of its Digital Grid division and as a member of the Board.