Renewable energy is expected to be one of the prime power sources as Japan is gearing up to achieve carbon neutrality by 2050. In fiscal 2019, renewable energy sources made up 18% of the total electricity supply in Japan, which was ranked No. 6 in the world in terms of renewable energy generation capacity. Playing a key role in this shift, wind power has kept a low profile thus far, primarily because of weather conditions and restrictions on locations in Japan. However, as wind power facilities evolve and the level of maintenance services increases, the number of installations has begun to accelerate, albeit gradually, having grown by approximately 50% over the past decade*1.
Wind turbines keep generating power day in and day out so long as there’s wind, and can be installed in a relatively small space. However, they have their own risks, such as deterioration due to wear and tear of constantly rotating blades, too much stress being imposed by violent winds during typhoons, and damage by lightning.
The Hitachi Group has an abundant track record in the supply of wind power facilities, having delivered a total of 860 systems, and ranks among the largest suppliers in Japan. Hitachi Power Solutions Co., Ltd., in particular, has constructed 461 wind power facilities since it entered the wind power business in 1996. As of this writing, it services by Long Term Service Agreement over 300 wind power facilities in Japan. In April 2022, Hitachi Power Solutions will take a giant step forward to commence advanced services that mitigate the risks of wind power facilities by combining AI and other digital technologies with cutting-edge drone technology.
Yukihiro Shirahama, a maintenance service engineer of wind power facilities at Hitachi Power Solutions, stresses the importance of keeping rotating blades in proper maintenance: "While power is being generated, the tip of the blades rotates at a speed of 300 km per hour, which makes it very vulnerable to damage. In fact, at various wind farms, there have been cases of dropped or broken wind turbine blades. We too have had such experiences at the facilities we service, in that we have encountered several instances of wind turbine blades being damaged by lightning strikes and typhoon winds.”
To address this shared concern, the Japan Wind Power Association (JWPA) in March 2021 established the "Wind Power Facilities - Rotating Blade Inspection and Repair Guidelines." A member of the working group for compiling the guidelines, Hitachi Power Solutions in fiscal 2021 set out to develop a brand new maintenance service geared specifically towards the guidelines in a bid to ensure greater safety and security at wind power facilities.
When going about designing advanced maintenance services, Hitachi Power Solutions paid particular attention to advancing its maintenance services by integrating inspection using digital technology with maintenance planning and repair work that utilizes a wealth of knowledge and technologies accumulated thus far. With SENSYN ROBOTICS, Inc., a provider of automatic, drone-based image capture, joining forces as a partner, the development project really took off.
Shirahama recalls how he accomplished this great engineering feat: "Using technology they suggested, we used drones to inspect blades on-site on a trial basis. Within a couple of hours of arriving at the site for the first time, we were able to fly a drone automatically for inspection*2. We had wind of 12 m/s at that point. Up until then, we had assumed for some reason that drones were not suitable for inspecting wind power facilities, which are typically located in windy areas. Contrary to our assumption, however, we became confident that there was a good chance of using drones for facility inspection. Then, the project went into full swing from early June 2021." Afterwards, while meeting with members of the development team five or six times, Shirahama repeated test demonstrations until they completed a blade inspection system.
One of the advantages of automatic, drone-based image capture is, first and foremost, shorter inspection time and higher work efficiency. In the past, service engineers had to use a telephoto lens camera to shoot parts that looked damaged, from the ground, and then check the images afterwards. The drawback of this method, however, is it takes a fair amount of human-power. Because every facility was visually inspected every six months, they had to inspect a total of some 1,800 blades a year. The drone-based blade inspection system not only shortened the time for inspection, but it also increased the overall efficiency of the inspection work itself.
Secondly, this innovative system helps to significantly increase inspection accuracy. When you use a telephoto lens camera, you have to contend with the natural environment: rain means reduced visibility, and you have to always remember to avoid backlight as it negatively affects image quality. When it was difficult to determine the extent of damage, the teams had to use cranes or ropes to perform a close-up, visual inspection, just as it is done with building wall maintenance. Automatic image capture using drones, on the other hand, allows the technician to capture images of the object from all angles and to take high-definition images head on and up close, with the result being that the extent of damage can be determined no matter where and when images are taken.
In the process of drawing up maintenance planning and repair work, the teams made every use of the knowledge and technological expertise that Hitachi Power Solutions has fostered over its many years in business. "The fact is that there are only a few companies in Japan who can offer a one-stop service that covers everything from inspection to maintenance planning and repair work.
Obviously, we are among the few. We not only use drones for automatic image capture but also use AI technology to determine the extent of any damage that might be discovered. Based on the findings, we come up with what we believe is the best maintenance plan - including what repair work needs to be performed and in what timeframe, which materials to choose for the repair work, and all this before we even start repair work." (Shirahama)
You may be wondering why maintenance planning is so important. Well, it's because the pace of damage progression can differ a fair bit as it depends on the timing and methods of repairs. The optimal maintenance plan can reduce the frequency and area of repair work. That is to say, owners of wind power facilities can minimize downtime, which in turn helps to sustain the amount of power produced, which is an added benefit to their business.
Also, previously, technicians would have to manually select photographs out of over 100 per unit in order to determine what state a wind turbine’s blades were in and the extent of damage. For this project, they also developed a data management system which sorts through and classifies the mounds of image data by wind farm or shooting angle. Applying digital data management to inspection, maintenance planning, and repair work under a unified system improves work efficiency. Furthermore, amassing data on past damage and repair history also helps to enhance the effectiveness of maintenance planning.
Meanwhile, repair work benefits greatly from the use of drones for the inspection of wind turbine blades. A self-taught, experienced repair engineer, Naoya Kanazawa, explains: "When we use drones for automatic image capture, needless to say, images are taken from the same position and angle every time. We suggested to SENSYN ROBOTICS, Inc., that we instead shoot images from five different angles. This is because it can sometimes be difficult to determine the extent of damage from images taken from the four traditional angles, along the X and Y axes, heads-on. Low accuracy in damage assessment can affect choices when it comes to repair work and repair techniques. Our goal for this project was to develop advanced services that cover everything from inspection to repair work, which should allow us to repair and maintain the blades in an optimal manner according to plan."
Because of the seamless “transitions” between inspection, maintenance planning, and repair work, this new service was named the "Blade Total Service."
Shirahama concludes with the roles and goals of their Blade Total Service, which underpins the safe and secure operation of wind power facilities: "For one thing, we are thinking of further tapping into the strengths of the 'OT (Operational Technology) x IT (Information Technology)' formula. For example, we are hoping to accumulate more specific knowledge such as the tendency for certain types of damage to turbine blades, as well as tendencies in repair history in order to further optimize our maintenance service. Also, this brand new maintenance service can be applied to not just our facilities, but to facilities from many different suppliers as well, which should allow us to extensively contribute to the expansion of the wind power business in Japan."
The development team hopes to apply our maintenance service to offshore wind farms which are expected to become a reality in the late 2020s, by leveraging knowledge gained from projects that the Hitachi Group has been previously involved with. "For us to expand the use of renewable energy, we must definitely ensure the safety and security of wind power facilities. However small the contribution of our Blade Total Service might seem, we believe that well-planned maintenance of wind power facilities is fundamental in helping Japan to achieve carbon neutrality.” (Shirahama)
Hitachi Power Solutions aims to realize a decarbonized society by supporting the enhanced safety and stable operation of wind power facilities through the provision of the Blade Total Service.
*1: Installed Capacity of Wind Power in Japan, New Energy and Industrial Technology Development Organization (NEDO)
*2: Trial flight on a simplified route for wind turbines, inspecting one blade from two angles
