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Health Monitoring of Offshore Wind Farms

Final Report Summary - HEMOW (Health Monitoring of Offshore Wind Farms)

Offshore wind farm health monitoring and maintenance are major challenges for the renewable energy generation due to large scale, high cost and extreme environments. The development of faults in the tower or blades can cause serious secondary damage to the whole wind turbine system if prompt repair action is not taken and can lead to catastrophic failure. Although numerous techniques are being developed worldwide to monitor changes in specific parts of a turbines structure, the wide variety of materials and techniques involved means that the skills and expertise are disparate and disconnected. For this new interdisciplinary area, this project brings well-recognized scientific institutions and researchers with complementary research experience and skills together, in the context of a collaborative scheme of research exchanges and networking.
The proposed project is endorsed by 5 institutions, 2 EU partners and research groups in China and India, agreeing for a common exchange program built around the work packages to develop methods, models, systems and ICT tools for health monitoring and maintenance of offshore wind farms. The partners of this project include: Newcastle University, UK (UNEW), West Pomeranian University of Technology, Poland (ZUT); Nanjing University of Aeronautics and Astronautics, China (NUAA), Zhejiang University, China (ZU) and Indian Institute of Technology Madras, India (IITM). The members of the project consortium provide complementary knowledge and strengths, as they have all carried out leading research in the area of non-destructive evaluation, structural health monitoring, communications and networks, information management, etc. The complementary capabilities have been drawn out in accordance with a joint research vision, commonly shared by the partners at the moment of writing the proposal.
The project has been successful. The achievement is beyond expectation although the implemented secondment is less than planned secondment. The main aims are to strengthen research partnerships through staff exchanges and networking activities between Partners. In addition to achieving scientific results in a particular area, the HEMOW project is above all expected to create additional benefits for the participants in terms of transfer of knowledge and to generate a basis for sustainable cooperation. The activities within the proposed project are divided into 6 Work Packages. All Work Packages are related and complementary. The proposed project helps to increase the transfer of knowledge between Partners as well as allow to build the basis for long-term cooperation. The major achievements can be summarized as follows:
(1) During the 4-year International Research Staff Exchange Scheme, Completed visits Xmonths (% of the original plan) due to lack of overhead fund associated with the allowance;
(2) The project website www.hemow.eu has been established;
(3) Two international workshops have been successfully organized as planned, in Newcastle University by Professor Gui Yun Tian and Nanjing University of Aeronautics and Astronautics (NUAA), China by Professor Shengfang Yuan and Professor Gui Yun Tian.
(4) More than 100 papers have been published in peer reviewed journals and international conferences; More than 10 patents have been applied. Several research awards, keynotes and invited talks have produced in the consortium
(5) More than 10 million Euro relevant projects within the research consortium have been successfully granted during the project. The successful grants includes: NUAA won the National Basic Research Program of China (also called 973 Program): Key Mechanical Issues and Design of Large Scale Wind Turbine (33 million RMB); The National Science Fund for Distinguished Young Scholars: Smart structure and health monitoring of engineering structures (2.8 million RMB); The international cooperation of national science and technology projects: Research on multi-channel ultrasonic phased array laser 3D imaging NDT system (2.18 million RMB). UNEW won two FP7 IRSES projects: CONHEALTH for healthcare and EDWTGT for Evaluation and Development of Wind Turbine Generator Technologies (1.2 million Euros); EPSRC funded Novel Sensing Networks for Intelligent Monitoring (Newton, 1.4 million pounds); EPSRC funded A systematic study of Physical LAyer Network coding: from information-theoretic understanding to practical DSP algorithm design (P.L.A.N). H2020 Innovative Training Networks (ITN-ETN) proposal NDTonAIR is in the review process.
(6) A sustainable network has been established. It has been demonstrated not only by the further research grant above, but also increasing the transfer of knowledge between partners and extension of research partners. For example, UNEW has installed an eddy current pulsed thermography system (ECPT) in NUAA for advanced NDT & E. Similar systems have been transferred to several other universities in China e.g. University of Electronic Science and Technology of China (UESTC), Hebei Technology University etc.
(7) 13 Chinese invention patents have been applied, 2 Chinese invention patents have been authorized and 1 PCT patent has been applied.
(8) More than 30 RAs, PhD students and Master students have been successful trained in the project.
(9) UNEW has built significant research link with MIT, USA. Professor Kenichi Soga , FRS, Cambridge university, UK has invited Professor Tian for Cambridge Conference on Wireless Sensor Network for Civil Engineering and Infrastructure Monitoring. Several knowledge transfers to China are in discussion.

Further major scientific results and impact can be outlined by different partners below.
UNEW: Newcastle has designed and developed eddy current pulsed thermograph systems for reinforced composite wind turbine blades and gear inspection; Magnetic sensors, novel RFID sensors and networks have developed for corrosion monitoring under insulation e.g. rebar corrosion monitoring in wind towers, generator fault diagnosis; Key issues of wireless sensor networks including sampling rates, data management – compression, fusion, mining and security have been addressed. Magnetic Barkhausen noise system and its stress characterization have been applied for early warning of gear fatigue and residual stress. It has contribution to all the WPs, WPs 1, 2, 4 and 6 in particular. In addition to research results, high quality joint papers have been published. Several keynotes and invited talks have been provided. The coordinator has also been involved in the Supergen Wind Hub in the UK. More research partners have been developed.
ZUT: ZUT has been actively involved with NUAA and IITM staff exchanges. The major scientific contributions include EM imaging and pattern recognition for quantitative NDE for all the WPs for steel components and composite elements of the offshore wind turbine structure. They have major contribution to WPs 2 and 4. ZUT has developed and implemented multisource electromagnetic nondestructive inspection setup (including Barkhausen noise, AC magnetization, magnetic flux leakage and eddy current methods) for examination of fatigue damage of steel components of the offshore wind turbine structure. The multisource data fusion algorithm was developed in order to increase the reliability of damage stage assessment in steel elements. Using pulsed terahertz inspection technique, we performed experiments with static and fatigue load of various types of composite materials. Algorithms for automatic defects detection and identification using pulsed terahertz inspection have been developed. Using the active thermography method, the research on the several methods including numerical analysis and experimental studies e.g. using eddy current pulsed thermography installed in NUAA from Newcastle for background removal were tested. Further research was directed to the identification of the detected defects. Some algorithms were used to obtain syntactical images, that provide more information than the raw signal from thermovision camera (thermogram). These algorithms were strongly associated with thermal tomography. The multisource composite inspection setup using X-ray, active thermography and terahertz techniques was also introduced and the data fusion procedures implemented.
NUAA: NUAA has undertaken research on the following main aspects.
NUAA has proposed three ultrasonic wave based structural imaging methods for damage and impact monitoring of large scale complex composite wind turbine blades, including a near-field 2D multiple signal classification imaging method, a phase synthesis based time reversal focusing imaging method and a damage index merging based multi-damage quantitative delay-sum imaging method. For real engineering applications of wind turbine blade SHM based on ultrasonic wave, a series of piezoelectric transducer layer and a series of miniaturized digital impact monitors have been developed. For on-line continuous SHM of wind turbine blades by using wireless sensor networks, an 8-radio integrated sink node and the time synchronization mechanism are proposed and developed to fulfil a high data communication rate to transfer a large amount of monitoring data. Wireless sensor nodes with self-healing ability based on reconfigurable hardware are also proposed and developed to improve the reliability of the wireless sensor networks.
NUAA have built Barkhausen noise stress testing equipment for material property and stress testing of gears. According to material of test specimen the equipment can choose the appropriate excitation signal, and choose the appropriate passband for a digital filter by which we can intercept signal to reflect the material stress or microstructure information best. Then, the study eddy current distribution characteritics of pulsed eddy current infrared thermal imaging technology has been used for fatigue testing of gears, which includes the calculation of induction heating model simulation, experimental research on ferromagnetic material and thermal analysis of image sequence processing. Besides, the excellent performance of the surface acoustic wave device makes it extremely suitable for integrated wireless passive sensing and radio-frequency identification, NUAA have applied the technology to the wireless temperature, strain measurement of wind turbine blades especially multiple blades in measurement simultaneously. To improve the resolution and sensitivity of damage detection, a new type fiber-ultra sonic sensor is designed to receive the signal of the near-surface damage in a composite wind turbine blade.
Incorporating controlled elitism and dynamic distance crowding strategies, a modified NSGA-II algorithm based on a fast and genetic non-dominated sorting algorithm is developed with the aim of obtaining a novel multi-objective optimization design algorithm for wind turbine blades. As an example, a high-performance 1.5 MW wind turbine blade, taking maximum annual energy production and minimum blade mass as the optimization objectives, was designed. A 1/16-scale model of this blade was tested in a 12 m × 16 m wind tunnel and the experimental results validated the high performance. Moreover, both the computational fluid dynamics (CFD) method and a free-vortex method (FVM) were applied to calculating the aerodynamic performance, which was consistent with the experimental data. For completeness, the CFD and FVM were used to analyse the wake structure, and good and consistent results were obtained between them.
Based on the above research, high quality papers have been published in peer reviewed journals and important international conferences. 13 Chinese invention patents have been applied, 2 Chinese invention patents have been authorized and 1 PCT patent has been applied.
ZU: Zhejiang university team has designed and developed an IGBT dynamic switching performance test platform for large-scaled wind power generation systems. It has identified the junction temperature extraction for high power IGBT modules, and enhanced the operation reliability of wind power systems. The work has also extended the proposed research to other renewable energy components and systems such as pitch system reliability and solar panel monitoring. They have major contribution to WP3, which is complementary to other WPs.
IITM: IITM has excellent interactions with the ZUT team, but less active on outing staff exchange due to lack of overhead for the funding scheme and UK visa issue. The project has led to several key collaborative conference publications at mutual national conferences and a number of high-impact journal publications are forthcoming. Moreover the project duration has also witnessed overlapping high-impact publications and innovative technologies developed in novel areas of guided. Ultrasonics from parallel but allied IIT Madras research efforts.