UAV technology rises to offshore renewables challenges

The accessibility and capability of the mission-critical data gathered for asset integrity inspections has been a ‘game changer’. 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.

The technology has proven 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.

Workscopes for fabric maintenance can be quantified much more quickly and accurately through advanced UAV deployed inspections for precision data acquisition. A UAV inspection of a turbine will take on average about 75% 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, as well as a number of other advanced inspection methodologies including: thermographic and internal investigations of structures.

A TIME- AND COST-SAVING TECHNOLOGY
On an offshore windfarm, a UAV can be launched in a matter of minutes and deliver real-time high-definition footage to an inspection team safely located on a supply vessel below. 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.

Skilled UAV pilots can acquire data that reduces time spent on a shutdown and even save an operational shutdown. They can also often extend production by generating information that feeds into decisions about operational continuity: images and detailed analysis can often mean that the need for an unplanned shutdown can be avoided.

A HUGE ADVANTAGE IN OFFSHORE ENVIRONMENTS
In harsh offshore environments where annual inspections are required, UAV inspections are deployed to log the ravages of sea salt corrosion; turbines here are subjected to a mixture of salt and seawater that represents the most challenging site conditions for asset condition. The abrasive effect of salt and airborne particles, including sand in coastal locations, is further exacerbated 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 inspection of a whole series of turbines from a boat within regulation distance. Inspecting for 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 ahead of the challenges facing the industry. Texo Drone Survey and Inspection Ltd has been investing in technology that allows for heavier payloads to enables its fleet of UAVs to operate under more 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 operates under expanded permits, including EVLOS/BVLOS and a UAV increased weight class (outside the standard 0 - 7kg) for UAV platforms weighing 7 - 20kg.

ACHIEVING EVER GREATER ACCURACY THROUGH UAV-DEPLOYED SURVEY-GRADE LIDAR
Traditional boat-based surveys typically take ten times longer to carry out than a LiDAR survey – 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 surveys can cover large areas 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.

In a standard LiDAR survey, accuracy of data is generally to around 40 mm; However, substantial investment and development of its LiDAR UAV fleet and associated survey software has led to Texo DSI Ltd achieving accuracy of 1 - 3mm with its survey grade UAV integrated LiDAR system, which is delivered via a custom-built UAV platform that measures over 1,000,000 points per second. This degree of precision means that surveys of assets can achieve pinpoint accuracy, which act as highly reliable baselines for future surveys. Combined with the ability to conduct long range (BVLOS), precision inspection of turbine and other renewable assets, via its HEF 32 UHS (Unmanned Helicopter System), allows Texo DSI Ltd to offer a unique UAV service to potential clients.

A CONSTANT TECHNOLOGICAL EVOLUTION
Advances in the technology and customised UAV platforms are bringing ever more operational benefits to offshore renewables operators, providing them with highly accurate data that removes subjectivity and errors from maintenance and planning. UAV technology is now, quite simply, central to inspection and maintenance regimes across the renewables industry.