High above one of Iberdrola’s wind farms, one may spot a small object hovering around the turbines. With its six slim arms and rotors, the Arachnocopter is a mere fly against the vast expanse of machinery it’s tasked to observe. But the Arachnocopter, and other unmanned aerial vehicles (UAVs) in its class, are poised to take a central role in turbine Operations and Maintenance (O&M).
Using unmanned machines for inspection isn’t a new practice in the energy sector. Drones were being put to work for aerial imaging at oil and gas refineries as early as 2011. In 2012, General Electric sent a small robot fitted with a high definition camera up a 300ft turbine pole.
Fast forward a decade, and leaps in drone technology have given rise to machines capable of far more than their early prototypes. These advancements are making UAVs an even more appealing alternative to traditional inspections as more wind farms break ground around the world.
Faster Inspections, Better Diagnostics
Maintaining a wind farm is costly, in both manpower and money. Inspections, which are an annual or bi-annual requirement, can take weeks. A single turbine can take over twenty hours to finish – the foundations of an offshore wind turbine, up to six each. O&M represents 30 to 40 percent of the total costs of a wind farm over its service life.
With more wind farms and turbines rising from the sea, this is a burden that’s not getting any lighter for operators. Drones can cut inspection time drastically. A two-week job for technicians can be done in two days, saving operators losses through downtime.
Drones don’t just do the job faster – they also provide data beyond what the naked eye can see. Inspection drones are fitted with cameras that can use thermography, an imaging technique that uses infrared to track how heat flows through an object. Stressed components generate more heat, allowing drones to pick up faults in the system before it fails.
Future vessels will be even more intelligent, streamlining operations. High altitude winds can be brutal. Out on the sea, wind direction can shift without warning, making it difficult to control and manoeuvre drones. But some drone fleets can already course correct. AI-enabled vehicles can make minute adjustments mid-air based on real-time data from their sensors, sooner than a pilot on the ground can from visual feedback alone.
Improving Safety for Blade Inspections
With repairs and inspections done hundreds of metres in the air, on machines that are being buffeted by strong winds, it’s not hard to see why wind technician is one of the seven most dangerous jobs in the energy sector.
Aside from the immediate risks of hanging from turbines, wind technicians also risk long-term damage to their bodies. Manual inspection fosters a considerable physical burden – technicians have to scamper up and down ladders while carrying a load of equipment, placing repetitive stress on their joints. Only about a quarter of wind turbines are equipped with assistance systems. The heat makes the climb even more dangerous – up against a pole, there’s no shelter from the sun.
Drones make inspections miles safer for technicians. “It is far safer than a wind tech hanging off a rope at high altitude while in high winds and for extended periods of time, often day after day,” says Ben Marchionna, Head of Global Operations at SkySpecs.
Improving Safety for Underwater Inspections
Aside from the blades, offshore wind turbines also require close maintenance of their foundations. Unlike onshore turbines, the bottom half of these machines endure punishment from salt water and the unceasing drag force of currents, making them more susceptible to damage.
While technicians don’t have to dangle hundreds of metres in the air, underwater inspections are equally hazardous. Divers have to swim through narrow and confined spaces, where getting crushed or injured is an all too real possibility. Visibility is also an issue near the seabed, where currents can stir silt and make navigating even more challenging.
Soon, technicians may not have to take the risk. Robotics companies have developed drones that have both aerial and underwater capabilities. Like their airborne cousins, underwater drones can collect a treasure of data without endangering lives. “You can also equip the underwater drones with different types of sensors, so that they provide data that complements each other,” says Maurits Huisman, a business development manager at TNO, a scientific research organisation from the Netherlands.
Smaller Margin of Error
As extensively trained and highly skilled as wind technicians are, they’re still fallible to human error. The demanding nature of the job, especially physically, further exacerbates chances they’ll make mistakes or miss a crucial fault while conducting inspections.
These mistakes can have significant repercussions. Around 40 percent of turbine failures can be attributed to human factors. And when the machinery is as massive as turbines and its components, failing to spot problems early can lead to catastrophic failure. Even small cracks can compromise the structural integrity of one of the blades, disrupting the delicate load balance of the entire machine. There are several cases of a turbine snapping or fires starting because of overstressed parts.
Drone inspections provide visibility into faults that technicians can miss. Video footage can be reviewed extensively by engineers on the ground. Data is automatically presented in digital form, which makes it easy to store and analyse whenever needed. Drones can also surface wear and tear patterns that operators can use to decide how often they should conduct preventive maintenance.
The Future of Drones Beyond Inspections
At present, the drones buzzing around wind farms are limited to inspections. The machines still lack the dexterity and load bearing capacity needed for conducting maintenance and repairs.
But that may soon change in the future. Some companies are already researching whether drones can be relied on for doing more complex tasks. “In [the] future, transport drones will have to be able to handle loads of several hundred kilograms and enable the direct transport of maintenance personnel,” says Sebastian Cain, mechanic and UAV pilot from the DLR Institute of Flight Systems.
At the University of Bristol, researchers are working on a project that involves an autonomous robot and a drone working in tandem for inspections and repair. Critical supplies can be delivered to offshore sites through drones, eliminating the risk of rough seas on supply vessels like ships and helicopters. At one wind farm in the North Sea, a search and rescue trial for drones saw UAVs combing the sea for targets and dropping life buoys.
Situated miles from shore, buffeted by high speed winds and monstrous waves, work at offshore wind farms is inherently hazardous. Drones help mitigate risk during inspections by doing the heavy lifting. Its potential for improving safety for other tasks such as repair and maintenance can only grow as drones become smarter and more complex.
