Genel
Measuring Rotor Blades with Lasers
By Torsten Wohlert, Deutsche Windtechnik Service, Germany
Deutsche Windtechnik has been measuring wind turbine rotor blades using a laser-based blade angle procedure since 2015. The company has discovered serious shortcomings on some of the 273 Vestas turbines examined to date. Where the relative blade angle deviations were 0.5 of a degree or more, the service technicians corrected the settings. This makes the wind turbines run more quietly, ensures less strain on the material and reduces wear.
Deutsche Windtechnik is to carry out measurements on all the wind turbines it maintains as part of a full maintenance contract that includes large components. This year the service provider will be checking the Vestas, NEG Micon and Siemens wind turbines. Similar examination of offshore wind turbines will follow. Badly adjusted rotor blades can easily lead to undesired vibration of the blades and drive-train, which eventually has an impact on the tower and foundations. This is why Deutsche Windtechnik was the first manufacturer-independent service provider to purchase a laser-based rotor blade measuring device at the beginning of 2014.
Tests and Evaluation Procedure
After extensive tests, which took nine months in all, and adjustments made in collaboration with the manufacturer, Deutsche Windtechnik began using the procedure on the turbines it maintains in March 2015. The company started with the Vestas type V90/V80 wind turbines, because they are particularly susceptible to rotor blade and tower vibration due to their long rotor blades of up to 125 metres. To verify the new measurement method, Deutsche Windtechnik compared the measurements using the new blade angle procedure with the results of the blade template method that it has been using to increase yield since 2007. Various aspects of both methods are compared in Table 1.
Higher Yields with the Blade Template Method
The blade template method involves the service technicians fixing templates to the rotor blades and then turning them to the mechanical limit stop. They then measure the actual deviation to this value and adjust where necessary. Here it is important to always ensure correct calibration of the wind turbine’s pitch sensors regardless of the base settings of the blades. This method is especially used to influence the performance curve of the wind turbine in a controlled manner and to increase the yield, because with the template the blades are optimised to a specific value. Using this approach also allows the aerodynamic imbalance to be reduced, resulting in less blade and tower vibration, and thus protecting the system components. Deutsche Windtechnik has used the blade template method for measuring Nordtank, NEG Micon and Vestas turbines since the company was founded in November 2007. However, the time needed and the downtimes for this measurement method are four times
hose for the laser-based procedure. A further disadvantage is the number of personnel needed: while a person can carry out the laser-based blade measurement procedure on their own, the blade template procedure requires three people.
Less Wear with the Blade Angle Method
The laser-based blade angle method is not so much about the yield; this procedure is aimed more at reducing wear and increasing the availability of the wind turbine. To take the measurements, the Deutsche Windtechnik service technicians direct two laser points at the blades and the tower while the turbine is in operation (Figure 1). They create an individual profile for each rotor blade (Figure 2) and determine the relative deviation of the blade angle by means of profile comparison. Because the service team measures the difference between the three rotor blade angles both at the blade root and at the blade tip, in addition to the relative deviations the method can calculate the twist as the difference between the blade root and the blade tip data. The twist should balance different angles of attack along the length of the rotor blade. If the twist of a blade deviates too much it can be an indication of poor production quality or that the surface has been altered as a result of repair work.
Corrective Action
For the correction of the blade angle, Deutsche Windtechnik factors in the result from the blade root, because this is where most of the measurements are generated. With hub heights of up to 125 metres and rated capacities of up to 2MW, Deutsche Windtechnik recommends correction where there is a blade angle deviation of half a degree or more. For this class of turbine, the company considers that urgent action is needed if the deviation is 1 degree or more. In the case of larger turbines with larger rated capacities, adjustment is in fact needed when the deviations are smaller. The evaluation is quick and straightforward and can be done directly on site. One person can take the measurements within an hour while the turbine is still in operation, thus minimising any downtime. The subsequent adjustment of wind turbines with either pitch or active stall control also takes only a few hours. More time is required for stall-controlled turbines because the pitching of the blades requires greater mechanical effort (see Table 1). As with the blade template procedure, the correct adjustment of the rotor blades reduces the aerodynamic imbalance, thus minimising blade and tower vibration (Figure 3). Because the loads travel from the rotor blades over the drive-train, mainframe and tower down to the foundation, a proper adjustment will protect all the mechanical components. This ensures less wear and high availability.
The Need for Early Measurement
Because great attention is paid to lightweight construction with modern designs, and with an ever-increasing size of wind turbines, it is all the more important to operate a turbine with the correct mechanical settings in order to reduce undesired loads. So that no components fail in the first place, Deutsche Windtechnik recommends control measurements as early as possible using the laser-based procedure, and ideally soon after commissioning. In most cases it is sufficient to measure each turbine just once. If, however, any adjustable components – such as pitch cylinders – are replaced during the operating period, subsequent measurements may be necessary.
Deviations on 117 Turbines
While measuring 2MW Vestas V90/V80 turbines since 2015, Deutsche Windtechnik has discovered massive problems with some of them. Of the 273 turbines measured, 68 exhibited blade angle deviations of half a degree or more. Another 49 turbines were, found to have deviations of 1 degree and more. Deutsche Windtechnik sees urgent need for action in such cases.
Long Rotor Blades Are Particularly Susceptible
Because Vestas turbines have very long rotor blades and hub heights of up to 125 metres, they are particularly susceptible to strong vibrations in the tower and the rotor blades. Because they are generally smaller, fewer problems are expected with the Siemens turbines measured since the beginning of 2016. Offshore turbines, on the other hand, are subjected to much harsher conditions, which also increases wear. They are to be measured using a similar procedure at a future date.
Even if they do not have a full maintenance contract, operators can order this service from Deutsche Windtechnik. The company offers laser-based blade angle measurement for around € 500 per wind turbine throughout Europe.
Extended Maintenance Concepts
To further reduce wear, Deutsche Windtechnik also ensures that the vibration absorber in the tower is ideally adjusted. To this end the company has expanded the scope of its annual and semi-annual maintenance. This holistic approach further reduces the ageing of the components.
Torsten Wohlert has been at Deutsche Windtechnik Service GmbH & Co. KG in Ostenfeld since 2007. After establishing the service concept for Vestas turbines he headed the E l e c t r i c a l Components and Technical Support departments. The 44-yearold has been head of the Engineering Department at Deutsche Windtechnik Service GmbH since 2012.
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Doğuhan Enerji, which provides turnkey services in road, platform, and foundation construction, electrical and cabling works, substation installation, control building construction, and overhead line construction for wind energy projects, also strengthens the European renewable energy sector with Helios Energy, its Romania-based subsidiary established in early 2022.
Operating a consistently with precision and dedication across all project scales, ranging from 1 MW to over 100 MW, Doğuhan Enerji has grown by successfully delivering some of the market’s largest and most significant projects. With 28 years of industry presence and participation in over 200 projects, the company has completed the construction of more than 1,500 turbines, contributing to a total capacity exceeding 2,500 MW. Beyond its core expertise in wind energy projects, Doğuhan Enerji has been providing solutions for solar power plant projects globally for the past three years. Through its European subsidiary, Helios Energy, the company has undertaken the construction and installation of the 155 MW Ratești Project, the largest solar power plant in Eastern Europe, completing it within a record-breaking period of just eight months.
Helios Energy, which has achieved one of the fastest growth rates in the sector by reaching a 600 MW project portfolio within just three years, provides end-to-end turnkey solutions for solar energy projects, covering every stage from construction and foundation works to mechanical and electrical installations, as well as substation construction, SCADA integration, and commissioning processes. In addition to its operations in Romania, Helios Energy is also active in Germany, Hungary, and Italy. Globally, the company has already secured agreements for 210 MW of wind and solar power plant projects to be delivered by 2025.
Striving for 20% Growth
Building a project portfolio that surpasses 2,500 MW, Doğuhan Enerji continues to leave its mark wherever the wind blows, actively participating in project developments across almost every region of Türkiye. To further expand its operational capacity, the company has been investing in machinery and equipment and plans to continue these investments throughout 2025. With the initiatives launched in the last quarter of 2024, Doğuhan Enerji aims to grow its operations in Türkiye and international markets by 20% in 2025.
The global Wind Power Market size was valued at USD 95.16 billion in 2023 and is projected to grow from USD 106.42 billion in 2024 to USD 254.27 billion by 2031, exhibiting a CAGR of 13.25% during the forecast period. Growing adoption of offshore wind farms and surge in wind energy projects are augmenting market growth.
The growing adoption of offshore wind farms is a significant trend in the wind power market. Offshore wind farms are being increasingly developed due to their numerous advantages over onshore counterparts. They benefit from stronger and more consistent wind speeds prevalent over the ocean, leading to higher energy yields and improved efficiency.
Additionally, offshore wind farms reduce land use conflicts, as they are situated away from populated and agricultural areas. Government incentives and advancements in technology are key factors fueling this trend. Many countries are offering subsidies, tax incentives, and supportive policies to promote the development of offshore wind projects.
Technological advancements, such as the development of larger and more efficient turbines designed to withstand harsh marine environments, are making offshore wind farms more viable and cost-effective. This trend contributes to lowering carbon emissions and reducing reliance on fossil fuels, thereby playing a crucial role in meeting the increasing global demand for renewable energy sources.
Wind Power Market Trends
The integration of wind power with energy storage systems is an emerging trend that addresses its intermittency, which represents a significant limitation of wind energy. By pairing wind turbines with advanced storage solutions, such as lithium-ion batteries or pumped hydro storage, the energy generated during peak wind periods is stored and used during times of low wind activity or high demand. This trend is gaining significant traction due to advancements in energy storage technologies, which are enhancing efficiency and cost-effectiveness. The combination of wind power and storage systems enhances the reliability and stability of the electricity supply, making wind energy a more viable and consistent source of renewable energy.
Additionally, integrated storage systems help mitigates the impact of sudden fluctuations in wind power generation on the grid, thereby reducing the need for backup fossil fuel-based power plants. This trend is supported by government policies and incentives aimed at promoting the adoption of renewable energy and energy storage technologies.
Wind Power Market Regional Analysis
Based on region, the global market is classified into North America, Europe, Asia-Pacific, MEA, and Latin America. Asia-Pacific wind power market accounted for a significant share of 36.25% and was valued at USD 34.50 billion in 2023, reflecting the region’s significant commitment to renewable energy development. The rapid expansion of wind power in Asia-Pacific is reinforced by the growing energy needs of its populous nations, particularly China and India, which are making substantial investments in both onshore and offshore wind projects. China has emerged as major country in wind power capacity due to its aggressive renewable energy targets, extensive government support through subsidies, and favorable policies.
Moreover, India’s national wind-solar hybrid policy and other initiatives are bolstering wind energy deployment. The region’s abundant wind resources, coupled with technological advancements and decreasing costs of wind power generation, are propelling domestic market growth. Additionally, the increasing environmental awareness and the urgent need to reduce greenhouse gas emissions are prompting countries across Asia- Pacific to adopt wind energy as a key component of their energy strategies.
North America is set to grow at a robust CAGR of 13.35% in the forthcoming years, largely attributable to several factors such as ongoing technological advancements, supportive regulatory frameworks, and increasing investments in renewable energy. The incentives are prompting utilities and independent power producers to invest in new wind projects. Additionally, advancements in wind turbine technology, including the production of larger and more efficient turbines, are reducing the cost of wind energy, thereby enhancing its competitiveness compared to traditional energy sources.
For instance, in 2023, according to US Department of Energy, Wind energy in the United States contributed to the reduction of 336 million metric tons of carbon dioxide emissions annually, which is equivalent to the emissions generated by 73 million cars.
Canada is further supporting this growth with its favorable wind resources and supportive provincial policies aimed at expanding renewable energy capacity. The commitment to sustainability and reducing carbon emissions is leading to the widespread adoption of wind energy in North America.
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