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Drones step up to renewables challenge

Unmanned aerial vehicle technology is constantly evolving to meet new challenges and provide new customized solutions for wind farm operators, writes Shelley Regan

Developments in unmanned aerial vehicle (UAV) technology for renewables inspection services and aerial survey work have been extensive over recent years, and the pace of progress remains unrelenting.

On- and offshore, the technology has transformed maintenance and repair regimes, adding greater commercial value and engineering accuracy and proving itself against so many long-established ways of working.

The UAV inspection method avoids the need for rope-access inspections and associated costly asset shutdowns, saving time and money as well as removing the risks of working at height.

The accessibility and capability of the mission-critical data gathered for asset integrity inspections has been a game-changer for the renewables industry. It is not just the savings in terms of time- and cost-efficiency that are decisive, but the numerous operational benefits that include improved monitoring and planning and the removal of risks to personnel.

Operational benefits such as these are invaluable against an industry background of fierce competition among renewables companies. Workscopes for fabric maintenance can be quantified much more quickly and accurately through close visual inspection (CVI), for example.

CVI inspections generate thousands of images and high-definition video. All of this provides data to inform engineering decisions in a fraction of the time that it would take a large rope access team to cover an area such as a full turbine.

In fact, a UAV inspection of a turbine will take, on average, about 75 per cent less time than it would take a rope access team to complete.

Additionally, the versatility of UAV inspections also includes the ability to carry out precise asset information modelling, optical gas imaging and hyperspectral investigations of structures.

Time and cost savings

Getting accurate assessments on the state of a particular asset quickly and in a relatively short period of time compares highly favourably to bringing in a rope access team to carry out an inspection that would involve a serious amount of safety equipment and take many hours or even days to complete.

A UAV can be launched in matter of minutes and can deliver real-time high definition footage to an inspection team safely located on the ground or in a supply vessel below.

The detail picked up by onboard cameras is minute: even the smallest hairline cracks and paint defects are made crystal clear. The level of detail coupled with the ability to review, slow down, and replay footage means that highly detailed inspections can be carried out to identify problem areas, common difficulties or regular maintenance requirements.

It also means that repairs can be precisely planned, based on the level of detail acquired; once again, this brings further savings in the form of vastly improved planning. Skilled UAV pilots acquire data that reduces time spent on a shutdown and even save an operational shutdown.

Supporting planning

The efficiency of planned turbine shutdowns can be further improved by using UAV inspection to precisely identify the condition and specification of parts that may need to be replaced.

Parts and components are all too often simply not available off the shelf and have to be specially manufactured. This is a huge benefit to operators to be able to order parts well in advance of their potential failure.

As well as being much quicker to carry out, UAV inspections can often extend production by generating information that feeds into decisions about operational continuity. Many operators are now inspecting their assets on an annual basis using UAVs as part of a planned inspection regime.

Elsewhere, other operators are tracking deterioration or already-identified issues on a month-by-month basis to push back the time between shutdowns, something they are now able to do thanks to accurate records of asset condition that can be quickly updated on an ongoing basis.

Offshore environments

Offshore, the technology can be effectively deployed to monitor the ravages of sea salt corrosion. Turbines in offshore windfarms are subjected to a mixture of salt and seawater that represents some of the most challenging and destructive site conditions for components and coatings.

Conditions are made even worse in coastal locations where the abrasive effect of salt and airborne particles, including sand, is heightened by the action of the rotor blades. At full speed the tips of the blades can exceed 50 metres per second. In addition, levels of ultraviolet (UV) radiation are significantly elevated on the coastline and at sea.

Bespoke UAVs are able to operate in high winds and cope with variable air pressure and high wave conditions, delivering the same high-quality inspection footage. Deploying UAVs in the offshore environment means that rope access crews are not required to be shipped to each turbine and then spend hours rigging up.

Instead, the two-man UAV inspection team can carry out a detailed condition inspection, for example, of a whole series of turbines from a boat within regulation distance.

On- and offshore, a further advantage of the technology can be seen in emergency situations where inspections can be carried out quickly and at short notice to get a quick but thorough overview of the true extent of a problem; again, images and detailed analysis can often mean that the need for an unplanned shutdown can be avoided.

Bringing objectivity

All of these advantages have secured UAV technology as a key player in helping renewables operators to design their asset management programmes.

Everything starts with agreeing objective measures of guidelines and condition ratings, which are based on detailed images that identify precisely what each rating represents for each component. In this way, all categories are agreed from the outset and objectively with regard to the true condition of coatings; detailed images allow for asset condition to be precisely graded.

This also ensures the repeatability of inspections in terms of consistent results: each inspection is to exactly the same criteria. In this way, true condition can be reliably tracked over a period, with interventions being planned based on objective data that allow for highly accurate projections.

Inspection relating to issues such as tip repairs, trailing and leading edge splitting, lightning damage, laminate damage, cracks and faults, shipping and construction related damage and end of warranty campaigns can all be dealt with most effectively by UAV technology.

Future-proofing the technology

The UAV landscape is ever-changing – and UAV companies and their technology need to be the same. Competition is constant and companies have to be on top of and ahead of the challenges facing the industry, not bringing up the rearguard. It really is about looking ahead to anticipate developments, rather than reacting to them: it is about future-proofing the technology.

A big part of this involves talking to clients ahead of them encountering particular scenarios, and developing bespoke platforms that meet their needs precisely by engineering solutions ‘from the bottom up’.

Investment is driving ever greater accuracy across the industry, and Light Detection and Ranging (LiDAR) survey work is a prime example. As with so many UAV applications, it is the scale and accuracy of LiDAR that differentiates it and raises it above conventional survey and inspection methods.

UAV surveys can cover hundreds of hectares in a single day and acquire thousands of high-definition geo-referenced aerial photographs. The principle of LiDAR is to measure distances via light in a pulsed laser form and record the time it takes from its generation and subsequent return to calculate distances. The images are then processed to provide highly detailed aerial mapping and topographic surveys.

Traditional ground- or boat-based surveys typically take ten times longer to carry out than a LiDAR survey – and worse still, they come without the added benefit of high-definition images of the site or installation. Advantages of LiDAR over traditional surveying methods include: dramatic cost savings; step improvement in safety; faster turnaround and improved site information to aid decision-making.

UAV technology is constantly evolving to meet new challenges and provide new customized solutions to wind farm operators. Highly accurate survey and inspection data removes uncertainty and error from maintenance and planning regimes. Coupled with huge operational benefits, it makes UAV solutions a highly compelling proposition in the competitive renewables industry.

Quite simply, technological innovation is a key part of continued commercial success for UAV companies and wind farm operators alike.

Shelley Regan is Commercial Development Manager at Texo Drone Survey & Inspection. Texo’s fleet of UAVs can operate under onerous weather conditions. The UAVs currently in operation can deal with wind speeds of up to 18 metres per second (40.2 mph), with the flexibility to carry a variety of custom payloads. Texo Drone Survey and Inspection Ltd operates under expanded permits, including EVLOS/BVLOS and a UAV increased weight class (outside the standard 0-7kg) for UAV platforms weighing 7-20 kg.