A smarter way to inspect wind farms

Melbourne based company, Braendler Engineering, is a leading designer and manufacturer of asset inspection systems that are used around the world in the energy, printing, food and packaging industries.

The company has now turned its attention to the development of an innovative system for the inspection of wind farm turbine blades.

Braendler managing director, Dr David Braendler, says that each of these giant turbines, which are about 80 metres off the ground, is valued at around $4 million so timely maintenance is critical for such a valuable asset.

"Each turbine has a 25 year life span and manual inspections involving ropes and cranes are generally programmed every two years, but a lot can happen in that time. The main issue is damage to the blades including through lightning strikes, as well as dust pitting which creates dimples on the surface of the blade and can grow quickly into a significant defect," he said.

"Manual inspection is costly, requires significant time and effort, has inherent safety issues, and is prone to human error. Also, manually captured images are not easy to utilise, and the end result is that the condition of the blades is difficult to monitor and therefore allocation of maintenance funding can be ineffective.

"To address these issues we have designed and produced the Aether Blade Inspection Service which consists of data capture, data storage and processing, and data analysis and reporting.

"The system is designed to rapidly capture and categorise defects across the entire blade surface. In turn, the Aether software that Braendler has developed allows assessment of blade condition and enables appropriate maintenance to be scheduled to maximise the lifetime of the asset."

High powered scopes

Using high powered scopes which are mounted on a mobile rig on the ground, the Aether system captures images of comparable quality to ropes and crane based inspections.Braendler explains that Aether Data Capture (ADC) captures high definition digital images of the blades using computer controlled imaging platforms specifically designed for this application.

"Using high powered scopes which are mounted on a mobile rig on the ground, the Aether system captures images of comparable quality to ropes and crane based inspections," he said.

"The Aether Storage and Processing Platform (ASP) is dedicated infrastructure used to store the terabytes of data captured by the ADC, and to process the data.

"Aether Data Analysis (ADA) software provides a means to interact with the blade data to assess and review blade condition, plan maintenance and monitor maintenance spend. This software is the interface that enables information to be provided to various stakeholders, including wind farm owners, site managers and OEMs.

"The Aether system offers an integrated service that features high definition capture, offline review of defects, defect classification, comparison with historical data, and 100 percent coverage of each blade."

Technical components of the system include a Swarovski ATM 80 HD scope, a Gigabit Ethernet 29 mega-pixel vision camera, and a high speed machine vision lens. A ruggedised embedded computer is configured to provide precise automated control of the position of the camera, and to focus the lens to capture images of the wind turbine blades.

While Swarovski Optik provided the scope and the interface between the scope, camera lens and the camera, Braendler provided the technology to enable high speed capture of images, and the mechanism to control the pan, tilt and focus of the system, as well as the backend software to stitch the images together.

Braendler points out that data capture by itself is not meaningful. "A way is needed to stitch the photos together so that they can be analysed for blade defects. This is achieved by the back-end software that we developed to enable the photos to be merged and create an image of the whole blade," he said.

the ATM 80 HD scope offers pinpoint detail with maximum peripheral focus, and that the fluoride containing HD lenses provide contrast-rich images with razor-sharp outlines."These full blade images can then be analysed off-site, any defects can be identified and repaired, and a follow-up inspection can be done to ensure the repairs were effectively carried out."

Hannes Nothdurfter, optik manager at Swarovski International (Australia), says the ATM 80 HD scope offers pinpoint detail with maximum peripheral focus, and that the fluoride containing HD lenses provide contrast-rich images with razor-sharp outlines.

"State-of-the-art electronically assisted processes enable the assembly of precision optics using the latest sensor technology to ensure consistent reproduction quality," he said.

Wind farms growth

According to www.thewindpower.net, wind farms worldwide produce 249GW of capacity, while in Australia the capacity is 2.2GW and growing. The World Wind Energy Association forecasts that by 2020, worldwide capacity will be 1,500GW.

According to www.thewindpower.net, wind farms worldwide produce 249GW of capacity, while in Australia the capacity is 2.2GW and growing. The World Wind Energy Association forecasts that by 2020, worldwide capacity will be 1,500GW.

Currently, the Aether system is being utilised at the jointly owned TruEnergy and Acciona Energy wind farm at Cathedral Rocks near Port Lincoln in SA, at Hydro Tasmania's wind farm at Studland Bay, and is planned to be used in the near future at TruEnergy's Waterloo wind farm near Claire in SA.

TruEnergy wind farm operations manager, Jason Watson, advises that the Aether system presents a number of benefits including the ability to track defects over time and establish the overall condition of the blade.

"Being ground based, it reduces the time and cost of actually performing the inspections, compared with using cranes, which cost a lot," he said.

"Blade defects will progress with time, as water in particular can penetrate the fibreglass structure of the blade. As they progress they become more and more expensive.

"Ultimately, the blade may have to be replaced if the defect is severe enough, which costs around $0.5 million in parts, cranes and labour.

"The Aether system has huge potential in the industry. Blades are the most difficult aspect of the wind turbine to manage because of their size and access difficulties.

"What Aether offers is much more than just an inspection tool as it allows the image of the blade to be compared over time, and compared with other blades.

"With this system, we expect to get a much greater understanding of what is developing, including when and why defects occur on the blades so that repairs can be targeted in relation to the most cost effective opportunities."