Unmanned inspectors have cost and efficiency benefits
Unmanned inspectors have cost and efficiency benefits
03 Dec 2015
FEATURE: Offshore Wind Journal
A recent Navigant Research report concludes there is significant potential for using unmanned aerial vehicles (UAVs) – commonly known as drones – to carry out inspection and maintenance work at offshore windfarms. So what are the actual and potential uses for offshore wind turbine inspection and maintenance?
According to Jesse Broehl, senior research analyst at Navigant Research and author of UAVs for Offshore Wind Turbine Blade Inspections, the ‘value proposition’ for UAVs is greater for offshore wind applications than it is for onshore applications. This is because conventional ground-based, optical inspections are more difficult to accomplish in the offshore environment.
Although inspection can be conducted from a vessel, he highlights the fact that the movement of a ship often tends to disrupt image integrity if using binoculars and field scopes. Although image stabilisation can provide a solution in some cases, he also points out this is “not a full solution”. He also sees rope and platform access inspections at sea as “costly and risky”.
“Currently, blade inspections are conducted with optical scopes from the base of a wind turbine’s foundation or around the transition piece platform that couples the tower to the oceangoing foundation. Typically, the scopes will have digital single-lens reflex (DSLR) cameras to save images. This vertical view upwards, however, results in some limited viewing angles so that some parts of the blade are not easily visible with optical scopes,” says Mr Broehl.
“Coupled with that, optical scopes are set up on one turbine’s foundation in order to view a nearby wind turbine’s blades as a way to improve the viewing angle. This can suffice, but it demonstrates the additional challenge of adequately viewing all blade surface angles in the offshore environment.”
Mr Broehl says there are also ongoing concerns relating to the time involved in getting scopes and technicians on the turbine platforms to carry out this work. Moreover, the report reveals that hourly labour in the offshore environment is “risky and very costly” and argues that even the transportation and transfer of technicians from a vessel to a turbine foundation platform is “risky in good weather and unadvisable in poor weather”.
To help mitigate these risks and limitations, the Navigant report attempts to alert the offshore wind energy sector to the idea that UAVs piloted from the safety of a vessel can help to accelerate the inspection process, simultaneously reducing the time that technicians need to be exposed to the offshore environment and the high cost associated with that work.
“In the not too distant future, UAVs will be piloted from centralised service platforms, so even a vessel is not necessary,” he claims. “Already, some offshore windfarms that are over 70km from shore in the Baltic Sea employ fixed service platforms to house wind turbine technicians who operate in weekly shifts,” Mr Broehl notes. “UAVs can become part of that centralised service solution, conducting regular inspections from the safety of a central service platform,” he adds.
One company that has already built up a great deal of experience in the use of UAVs offshore is Scotland-based Cyberhawk, which, over the last three years, has been inspecting offshore meteorological masts at many offshore windfarms in the UK. Philip Buchan, commercial director at Cyberhawk, explained that 2015 has been the company’s busiest year in the renewables sector after it launched a commercial-scale inspection solution for wind turbines, including blades, nacelle, tower and transition piece. This solution, known as iHawk, converts raw images from UAVs into what the company describes as “powerful and useable asset management information”.
The significant increase in renewable projects has seen Cyberhawk operate in six different countries throughout Europe, completing projects for clients including RWE, SSE, Siemens, Vestas, Forewind, EDPR, Repsol and Dong Energy. According to Mr Buchan, when coupled with new field techniques, iHawk wind software enables the company to accurately detect defects on a blade and provide an idea of their size.
“Utilising a multi-rotor ROAV (remotely operated aerial vehicle) platform, specially adapted for industrial inspection in harsh environments, a two-person team is deployed for each project – one specially trained ROAV pilot controlling the ROAV’s position in the air, and one experienced inspection engineer controlling the camera and conducting the inspection,” he explained. “The system allows Cyberhawk to operate off the back of vessels or from the wind turbine transition piece using its fully certified team members,” he said.
For Mr Buchan, the benefits of using ROAVs for data capture in the renewables sector are significant. Along with considerable cost savings, he claims that safety is significantly improved by minimising the need to work at height, and inspection speed is “three to four times faster” than rope access, with results delivered in the form of a systematic visual record for the whole blade or turbine.
“The vast improvements in efficiency offered by ROAVs are illustrated by a recent project that we undertook for a major OEM. One Cyberhawk field team completed more than 30 wind turbine inspections in less than two weeks, with an average downtime of only two to three hours per turbine, which significantly maximised the client’s turbine production time,” he told OSJ.
Switzerland-based Visual Working also believes there are a number of advantages of using UAVs for turbine inspection and maintenance offshore. Following an innovative operating procedure, said Paolo Brianzoni, ceo at Visual Working, can provide “remarkable results” and the ability to inspect more than 10 turbines per day. This results in a significant reduction in inspection time – and hence downtime – compared to previous inspection methods. “The images we are able to capture are taken from the best perspective, and their quality is extremely high. Everything in complete safety,” says Mr Brianzoni.
Despite the obvious potential benefits of this new way of employing UAV technology, Mr Brianzoni admits operating in the offshore environment still presents the company’s staff with challenges. One challenge is the fact that the UAV used needs to be able to withstand extreme conditions, such as cold weather, fog, high winds and waves. Even so, Mr Brianzoni says Visual Working has successfully operated its drones offshore with wind gusts up to 20 m/s and 5m waves. In some conditions, living offshore itself can become a challenge. Extensive investment is needed to keep operators and equipment updated, and UAV maintenance is also often required.
Although there are challenges to overcome, Mr Brianzoni is confident that, in the very near future, this innovative inspection method will become widely adopted by windfarm operators, such is its effectiveness.