1.
How Often Does a Wind Turbine Need Maintenance?
2.
Understanding Wind Turbine Maintenance Costs
3.
How Drones Improve Wind Turbine Inspection and Maintenance
3.1.
Visual Inspection
3.2.
Protective Coating Measurements
3.3.
Thermal Scans
3.4.
Lighting Protection System Testing
4.
Conclusion
Modern-day Don Quixote would’ve had his hands full with 107 thousand wind turbines, scattered around Europe alone. An additional 90 thousand wind turbines could be at his mercy if the sequel brought him into the present-day United States.
Fiction aside, wind farms are now a critical element of global energy grids, helping sustainable transition. As the operational footprint grows, so does the need for timely wind turbine inspection and maintenance.
Wind turbine failures lead to expensive repairs and replacements, environmental harm, downtimes, power outages, and subsequent financial impacts. That’s why owners are required to conduct regular inspections of all wind turbine components — from blade tips to foundation — to ensure structural integrity.
With wind turbine inspection drones, you can perform inspection faster than any rust and dust overthrow the wind giants.
Statutory inspections and maintenance are a legal requirement for wind farm owners to receive and renew operating permits. There are international and local standards describing criteria, procedural steps, and measurement ranges for different types of wind turbine tests.
International codes include IEC 61400-12, IEC 61400-23, ISO 18436-2, and ISO 10816. Codes also vary from country to country: BSH standard for Germany, BS EN 50308:2004 in the UK.
On average, codes specify routine inspections every six months, and comprehensive checks every 1-2 years. There can also be different inspection intervals for each turbine component:
| Component | Inspection frequency | Standards |
| Rotor blades | Every 2-4 years | AWEA, TÜV SÜD |
| Rotor hubs | Minimum every year | AWEA |
| Nacelle and gearbox | Every year | BSEE |
| Rotor blade | Every 2-4 years | AWEA, TÜV SÜD |
| Rotor hubs | Minimum every year | AWEA |
| Generator | Twice per year | AWEA |
| Anchor bolts | Once a year for the first 5 years and then every 5 years | AWEA |
| Grout and concrete structures | Yearly on 100% of the turbines for the first 5 years, yearly for 50% of the turbines after 5 years | AWEA |
| System joints and terminations | Every 5 years | AWEA |
| Pressure vessel | Every 10 years | TÜV SÜD |
| Lighting protection system | Visual inspection every 1-2 years, a complete inspection every 2-4 years. | IEC 62305 |
| Safety equipment | Every 6 months for lifting equipment, and 1 year for ladders, locking devices, and safety rails | BS EN 50308 |
In areas prone to frequent thunderstorms, excessive heat, and increased humidity, wind turbines need more frequent inspections: Monthly visual and twice-yearly detailed checks.
Wind turbine maintenance is a necessity, but it has a steep price tag of 18.9% of the wind farm’s lifetime CAPEX costs. Still, skipping routine inspections isn’t an option. Poorly maintained wind turbines lead to equipment failures. Failures result in hefty spending on component replacements, incident investigations, or regulatory fines.
According to research conducted in Denmark, structural repairs of a failed wind blade can cost $30,000, while replacements average $200,000. The most expensive issue is gearbox malfunctions, which cost €230,000 ($253,000) on average.
The repair costs exacerbate as wind farms grow larger and turbines — more complex. Last year, Siemens saw an increase in wind turbine failures in their Gamesa division where some wind turbines reach 222 m rotor diameter. The company found that the severity of quality issues was underestimated and “swept under the carpet”. Now, Siemens has to do a thorough investigation, which is expected to cost almost $1 billion.
In the worst-case scenarios, wind turbine malfunctions lead to blackouts and downtimes. For instance, technical issues on the UK offshore wind farm led to an almost 1-hour blackout, affecting 1 million residents and disrupting the rail network. The wind farm operator faced a £4.5m fine ($5.7m) for failing to remain connected during a lightning strike on Friday’s busiest hour.
You can cut costs by locating defects at an early stage. Preventative maintenance for one wind turbine is €10,000 ($11,000) on average per year. Out of an estimated 10 wind turbine failures per year, 80% are minor and cost less than €1,000/$1,100 to repair. Early issue detection saves costs in the long run.
To optimize wind turbine maintenance costs even further, farm operators are also investing in inspection drones. Drone inspection of wind turbines eliminates the need for rope access. It also requires smaller teams (one or two operators). And these benefits are just the tip of the iceberg.
The best wind turbine inspection drones are well-equipped to access and test all components thoroughly, swiftly, and with no risk to the turbine structures. Copters have maneuverability and strong obstacle awareness to secure access to even hard-to-reach wind turbine components.
With full flight stabilization and improved navigation, drones can resist strong wind gusts – between 12-16 m/s — and maintain stability to perform close-to-structure work. Enterprise drone models, boasting long battery time, autonomous flight modes, and long transmission ranges, streamline your offshore wind turbine maintenance. Aside from being your eyes from afar, drones can also carry extra payloads to perform inspection tasks.
Popular drone payloads include thermal and RGB cameras, ultrasonic transducers, multispectral sensors, and a host of other options for collecting rich inspection data. For wind farm drone inspection, in particular, drones with payloads enable the following four scenarios.
Visual inspections help verify the integrity of all wind turbine components. They should be conducted both routinely and after severe thunderstorms, hurricanes, blizzards, and hails to determine the extent of damage.
Equipped with a high-resolution camera, industrial inspection drones can detect even minute surface-level defects, allowing for proactive maintenance. Or capture abnormal blade movement patterns or rotor sounds in a live video. With vibration cancellation and stabilization mechanisms, drones can take accurate shots even under strong wind gusts.
Effectively, wind turbine drone inspection helps locate the precise location, size, orientation, and depth of the following defect types:
German wind farm operator, Deutsche Windtechnik, recently launched a drone wind turbine blade inspection program at its offshore farm. The company estimates that 50% of offshore wind farms’ turbines could be inspected with drones each year, resulting in shorter downtime. Only 8% of drone-inspected turbines will require additional rope access inspections for result validation.
Drone wind turbine blade inspection supplies Deutsche Windtechnik with richer asset data. They have a complete picture of the rotor blade exterior and the ability to track damage proliferation over time using inspection software.
Wind turbines, specifically blades and towers, require protective coatings made of epoxy, acryl, polyurethane, zinc, aluminum, and paints. The coatings stave off corrosion, erosion, material degradation, and ice build-up. However, they gradually wear off due to strong wind gusts, heat, and humidity.
Early detection of protective coating thinning prevents material degradation. Inspection drones like Voliro T enable dry film thickness (DFT) measurement at heights with a purpose-built payload. Voliro’s DFT probe supports two measurement modes, magnetic induction and eddy current, making it suitable for both ferrous and non-ferrous metals. It provides a measurement range between 0-1.5 mm, allowing you to catch coating thinning at early stages and track its progression over time.
Using Voliro technology, a one-person crew inspected 10 towers per day. Using the DFT probe, the inspector confirmed the proper application of freshly applied coating. The inspection was done right after painting, resulting in lower downtime. Voliro T sends DFT inspection results and reports right to your device.
Temperature-related damage shows up a lot in wind turbines placed in hot deserts, especially assets without cooling systems. Wind farms in lightning-prone areas also suffer from high-voltage burns, blazes, and equipment malfunctions. Thermal scanning can detect hot spots early on, preventing costly degradation.
Some Inspection drones come with mountable thermal sensors or infrared cameras. They capture the precise thermal readings on your wind turbines and illustrate temperature differences in gradients. Some companies allow you to analyze and annotate thermal footage in complementary apps.
Drone-mounted thermal cameras are useful for:
Weather conditions, like heating sun, or precipitation, can mask potential issues during thermal inspections. So it might be necessary to perform a second control check in another season.
Offshore Renewable Energy Catapult recently deployed a thermographic drone to test wind turbine blades at its Blythe site. Featuring a 1,000W heat lamp and AI-assisted defect detection system, the UAV captured temperature changes in heard blades, revealing subsurface flaws and locating their position. Moreover, the drone managed to cruise close to the vertical-suspended blades in a fully autonomous mode.
Each wind turbine should feature a robust LPS system to intercept lightning currents and redirect them away from the electric equipment. But as with all mechanisms, LPS systems are susceptible to wear and tear over time.
Failure to inspect LPS may lead to lightning-induced damages, downtime, and costly repairs. Make it a rule to test your LPS before, during, and right after installation, after major repairs, and after environmental damage.
As per IEC 61400-24, you need visual LPS inspections at least once a year, and full LPS inspections — twice a year. Drones aid a lot with LPS inspection as they can help check:
Voliro T has a purpose-built LPS testing probe, featuring a Micro-Ohmmeter VG-BAT-150. The probe provides a 4-wire measurement of 0.30 A currents, for resistances <20 Ω. It boasts a high precision, with 0.001-1000 Ω measurement range at any turbine rotor orientation.
With Voliro’s technology, Skyspecs, a provider of energy equipment and solutions, tested 210 wind turbines across Germany and the USA, inspecting 8-18 turbines per day. Inspections are faster and safer, as the staff doesn’t need physical access to the hub and nacelle. Moreover, Voliro drone helped identify 3X-4X more defects, compared to conventional inspection methods.
Wind turbines have an average life span of20 years, however, it can be prolonged even more with routine inspections, preventative care, and timely repairs. Yet, it takes a lot of energy – and equipment – to inspect and maintain a single wind turbine.
We have the solution for you. Voliro T provides access to six different non-destructive testing tools within a single subscription. Purpose-built for performing work at height, our drone boasts six degrees of freedom maneuverability, allowing seamless access to different wind turbine components. Our subscription includes immediate replacements, minor drone repairs, hardware rotation, and sensor recertification.
