The number of wind turbines used globally has grown exponentially over the last few years and with it so has the need for efficient and safer inspection methods. Ray Faulkner from iRed, an industry-leading thermographic consultancy and training centre, explains how Unmanned Aerial Vehicles (UAVs/Drones) are establishing a strong case for involvement.

Renewable energy has now overtaken coal as the world’s biggest source of power-generating capacity. Clean energy costs are tumbling, with the potential for industry growth rapidly expanding. Britain has been at the forefront of developing this technology; however it’s in danger of falling behind.

The rest of the world is catching on. China, for example, is working towards becoming a green energy superpower, with huge investments in solar energy. India is making strides in their development of wind power and Ireland has recently voted to become the first country to remove all dependence on fossil fuels.

The UK has been the fastest growing green economy in Europe. Despite being a world leader in offshore wind - helped by having the second largest tidal range in the world - the UK has the potential to supply a far greater share of the country’s energy

Keeping the wind blowing in the right direction

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needs. According to Renewable UK, there are currently over 7000 wind turbines operating within Britain, with nearly 6000 of these being onshore installations.

Using drones for inspection

The quick and efficient scanning of land, building sites and large machinery by UAS (Unmanned Aerial Systems) present not only a far safer method of inspection but a more effective view of operations, offering a new perspective from which issues and faults can be detected. New ‘Gas Find’

UAV IR cameras for the oil, gas and utility industries are already in service, providing exceptional results in areas previously considered impossible to survey.

Inspection using drones combines visual or infrared techniques, looking for visual characteristics and thermal signatures. Thermography (otherwise known as thermal imaging) uses infrared-sensitive cameras to

inspect buildings, electrical equipment and rotating machinery to find faults associated with heat loss or gain. Infrared cameras have developed significantly over recent years: modern thermal imaging cameras are now so small they can fit in the palm of your hand. These smaller and significantly lighter infrared cameras are ideal for integration with aerial platforms.

Solar panels

The first foray for drones, into the renewables market, was not with wind turbines, but with photovoltaic solar panels. A need for inspection is becoming increasingly essential as the use of solar energy is expanding both domestically and commercially. Solar panels are highly sensitive pieces of equipment that require periodic maintenance in order to replace or repair damaged panels, in order to improve efficiency.

Pairing aerial capabilities with thermal imaging techniques allows the inspection of PV systems in remote areas, meaning rooftops and large buildings can easily be assessed. Employing infrared technology and high definition imagery makes it possible to find damaged cells, survey large solar farms and monitor the overall effectiveness of energy production.

Wind energy

Wind turbines promise to be an enormous market for drone inspection. As the industry matures, a growing number of wind turbines are operating out of warranty and must be serviced more frequently to maintain productivity and avoid downtime. Preventative maintenance by inspecting blades before a blade failure actually occurs costs 25% less than reactive maintenance, while predictive maintenance costs 47% less.

This is driving a brisk business in wind turbine blade inspections, a role that has traditionally been accomplished from the ground using simple visual inspections to more complicated and risky techniques such as using a cherry picker, service platform, hydraulic crane or rope descent. These methods involve heavy equipment or climbing, which is not only time consuming, but costly and very dangerous.

Commercial-grade UAVs handled by professional operators are proving to be a more effective inspection method than any alternatives. Not only can they provide closer, higher-resolution imagery than

ground-based alternatives, they are also significantly quicker.

UAVs are able to fly at an optimum distance from the structure, usually from 3 to 10m, and can circle around it to cover the whole surface area. This data can then be used in conjunction with photogrammetry software and used to build a three-dimensional model of the blade, delivering a level of accuracy and detail that is hard to achieve with manual methods. When and if repairs are needed, the team knows the exact location on the turbine. Because it is GPS enabled, it also points to the repair’s exact location.

Software systems are emerging to automate the task of inspecting wind turbine blades using UAVs. WindSpect, powered by AirFusion, is the first software based, intelligent image recognition technology for the wind power industry. WindSpect automatically recognises over 40 types of wind turbine blade damage and records their positions on the blade. The data is then organised by blade and tower, sorted for severity of damage and a full report is automatically output in industry standard data formats for use in ERP, CMMS and SCADA compliant systems.

Another important benefit of using drones is that it keeps everyone on the ground for the entire process, allowing a team of skilled technicians to direct and guide the operator in real time.

Visual or thermal?

Both visual and thermal analysis play a useful role in the inspection of wind turbines. Blade damage and gearbox failure are the two factors responsible for the greatest amount of energy loss, with poor maintenance and lightning strikes being the most frequent causes. While inspection of the main tower is primarily a visual job, thermography can play a useful supportive role in examining nacelles and the turbine blades themselves. Nacelles house the mechanics of the turbine, including the gearbox, generator, brake, controller and yaw mechanism.

Nacelles

Visual inspections are carried out to ensure that there is no damage and no debris has built up around the moving parts. If there were debris in the nacelle, this in the worst case could ignite. If the yaw mechanism is damaged then the turbine may not be able

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to turn its blades against the wind, which could result in greater damage. Although visual inspection is most significant, aerial thermography on wind turbines is also useful for quickly discovering excessive heat being generated from the nacelles.

Blades

Exposed to whatever the weather throws at them, rotating at 10 to 22 rotations per minute and designed to endure more than 120,000 operating hours, the blades are some of the hardest working parts of a wind turbine. Made of glass fibre reinforced composite and weighing around 12 tonnes each, there is a need to ensure they are structurally safe.

Thermographic cameras can be used to identify areas of the blade which are delaminating, as they can detect variances in the heat of the blade structure. Inspection of the blades can be carried out using drones, or a telescopic mast and a zoom camera which can examine the blade in detail.

Training and consultancy

Naturally, companies who can provide a combination of both visual and infrared inspections have a competitive advantage. It is still not common for those carrying out visual inspections to have any thermography qualifications - however, at iRed we have seen a growing number of people book from the wind turbine inspection business onto our thermographic training courses to distinguish themselves from their competition. Many such companies also offer inspection of other renewable energy assets, including solar, where thermal inspection using drones also plays a major part.

Founded in 2002, iRed is at the forefront of industry, providing specialist thermographic and remote sensing services, consultancy,

training and equipment across the UK and worldwide. The team holds ‘Permissions for Commercial Operations’ from the Civil Aviation Authority (ID. 2082) allowing them to utilise drones to provide new, innovative inspection techniques.

iRed is the first in the UK to launch a Specialist Infrared Payload Course for Drone Operators. Over two days, the course is designed to provide theoretical and practical knowledge for professional users intending to view or capture aerial thermal images. The first specialist payload course will take place this month at the company’s purpose-built training facility in Emsworth, near Portsmouth.

The APS (Aerial Payload Specialist) Infrared Course enables delegates to utilise aerial IR equipment to view or collect thermal data to an industry standard. This is achieved by familiarising attendees with established and proven techniques used in the planning and execution of commercial aerial surveys. Delegates are issued with the APS Infrared

certificate upon completion of a ground-school multiple-choice exam and a practical flight assessment.

The first day is classroom-based, with topics including suitable airframe types, IR camera selection, pertinent air laws, human factors, environmental conditions, workflow and customer deliverables. On the second day, the practical session is run from the company’s Bosham base, where delegates have the opportunity to plan, rig, test and execute an aerial thermographic survey.

www.ired.co.uk

Further Information

For further information please contact Tim Mammatt, Business Development Manager, iRed, tim@ired.co.uk or Jack Bloomfield, Marketing Manager, iRed, jack.bloomfield@ired.co.uk

iRed: Unit 6, The Old Flour Mill, Queen Street, Emsworth, Hampshire PO10 7BTTel: 0124 3370296

About iRed

Founded in 2002, iRed is an industry-leading team of accredited thermographers based in the UK, providing expert thermal imaging training and services worldwide. This passionate team has worked with a variety of clients within domestic, commercial, industrial and scientific industries, developing decades of experience and expertise. Using the latest imaging technology and techniques, iRed delivers a wide range of services including condition monitoring, thermographic inspections, reliability engineering support, mould & damp detection, electro-mechanical surveys, continuity of insulation, specialist investigations and BREEAM surveys.

The nacelle area of a wind turbine, prior to installation

DJI Inspire mounted with the Zenmuse XT

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