Annual Report 2015 DTU Wind Energy

Transcription

1 Annual Report 2015 DTU Wind Energy

2 2 RESEARCH AND INNOVATION ACTIVITIES ANNUAL REPORT 2015 Annual Report 2015 ISBN: DTU Wind Energy Technical University of Denmark DTU Risø Campus Building 118 Frederiksborgvej Roskilde Website Editor Berit C. Larsen Editing Berit C. Larsen and Niels Gylling Mortensen Layout Charlotte Brunholt, GraphicCo. Photos Thorkild A. Christensen, Open House, Colourbox, Joachim Rode, Joakim Ladefoged etc. and several by colleagues at DTU Wind Energy Printed in Denmark by Front page photo: VESTAS, Joakim Ladefoged, DTU Vindenergi

3 ANNUAL REPORT 2015 TABLE OF CONTENTS 3 Table of contents Foreword by Head of Department 4 Highlights Research and innovation activities Floating wind turbine in waves and wind 10 Improved wind inflow models make for a robust design of tall wind turbines 13 Exploring the design of the Olsen Wings 14.3 m blade 16 How and why blade materials fail in fatigue 20 Improved adhesive joints for wind turbine blades 23 Innovative monopile design for large wind turbines installed at 50 m water depth 12 Detailed design of the Danish National Wind Tunnel 14 Wind turbine rotor noise from source to receiver 18 Trailing edges breaking bad 22 Metallurgical issues in wind turbines 24 The DTU Global Wind Atlas 26 A new procedure for calibrating ground-based lidars 30 Determining reserve power from offshore farms 32 New ESA validation standard antenna manufactured and designed by DTU 33 DTU Wind Energy launches its first Coursera course 35 WindScanner sees the wind 28 Preventing black-outs and securing operation of power systems 31 Lighter and manufacturing friendly boat design for TUCO Marine 33 Education 34 PhD projects 3rd year students 36 PhDs in Advisory Board and Educational Advisory Board 43 Organisation 42 Publications 45

4 4 FOREWORD ANNUAL REPORT 2015 Research and value creation a must DTU Wind Energy is specifically focusing on wind energy and combines research and value creation through education, innovation and research-based consultancy. Research is carried out together with partners in Denmark and internationally. The purpose of the Department of Wind Energy is to develop wind energy to meet essential societal challenges on climate, job creation and growth. The purpose is met by using all the instruments of a university department, i.e. by delivering excellent and relevant research, innovation, education and research-based consultancy to support the politically intended shift towards a zero carbon emitting economy. The department thus contributes to DTU s mission to develop and create value using the natural sciences and the technical sciences to benefit society with a special focus on the wind energy sector. The objective of our research is to push the limits of the technical sciences for the development of wind energy. The department s research collaboration is cross-disciplinary and also includes other departments as well as national and international research groups. The national and European competition for energy research funding is fierce, and focus is mostly on bringing technologies to the market. Strategic, medium to long research is not funded to the same extent as earlier. In order to accommodate this trend the department focuses on developing our interaction with industry, especially SME s, and continues to highlight the need for medium-to-long term research. To develop and achieve synergies in existing and new areas of research, three cross-cutting initiatives on Advanced Materials, Aeroacoustics and Systems Engineering were implemented in Furthermore, we decided to strengthen and emphasize this collaborative approach by organizing our activities in 5 cross-disciplinary programmes with a responsible programme manager. The programmes are Wind Turbine Technology, Offshore and Siting & Integration (all focusing on research and innovation). Additionally, there is a programme for Education and one for Research-based Consultancy and Test. The development and operation of research and test infrastructures are central elements in our research and the interaction with industry. In 2015 a new 850 kw research wind turbine was inaugurated at the DTU Risø Campus, and research testing commenced. Other significant activities include the wind scanner and the national wind tunnel further described in the following. While research is our core activity, research needs to be complemented by other activities in order to accelerate the value creation from new knowledge. Education is the basic activity, whereby a university brings knowledge to society and creates value. DTU Wind Energy offers a complete two-year master programme in wind energy and participates in the Erasmus Mundus European Wind Energy Master in cooperation with NTNU in Norway, University of Delft in the Netherlands and University of Oldenburg in Germany.

5 ANNUAL REPORT 2015 FOREWORD 5 The majority of students in the master programmes and the PhD-school are international. Furthermore, e-learning is a new and excellent opportunity for teaching, developing training courses and branding. The first MOOC (Massive Open Online Course) on wind energy was developed in 2015 and launched early in Of primary importance for our contribution to the value creation in the wind energy sector is collaboration with industry on innovation and technology development as well as interaction with industry on testing materials and components and turbine prototypes. We also offer measurements of wind conditions, turbines, wind farm performance and research-based consultancy to Danish and international authorities. The activities and projects are numerous, but in this annual report we have highlighted examples of how research combined with such activities address societal and industrial challenges and creates value. As the following pages testify, 2015 was a year with many new research results and activities. It is my hope that this annual report will be used as an introduction to a department with an exciting multi-faceted research programme and a similarly strong effort on value creation through education, innovation and research-based consultancy. Hopefully, it will inspire present and potential new partners to cooperate with DTU Wind Energy for the development of the wind energy sector. Peter Hauge Madsen February 2016

6 6 HIGHLIGHTS ANNUAL REPORT 2015 JANUARY JANUARY European Wind Energy Students visit Østerild Inaugural lecture by Wen Zhong Shen In January fifteen students from the European Wind Energy Master (EWEM) visited the national test centre at Østerild as part of the Multiple Day Excursion (MDE) organized by the EWEM student association Aeolus Senior researcher Wen Zhong Shen appointed professor in Computational Aero-acoustics and Wind Energy held his inaugural lecture as professor 30 January 2015 titled: Wind turbine noise and what to do about it. FEBRUARY MARCH DTU Wind Energy at EWEA Offshore Conference Test Centre at Østerild is a tourist attraction In March, the EWEA Offshore Conference took place at the Bella Centre in Copenhagen. DTU Wind Energy participated with a stand and outside exhibition. Outside people could see the wind racer car and wind scanners as well as talk with staff. Since the national test centre opened in 2012 the area has become an authentic tourist magnet. The beautiful stretch of countryside to the north of the Limfjord now features huge wind turbines the tallest is Vestas 8 Megawatt giant, measuring 222 metres from ground level to blade tip in its highest position. MARCH APRIL Inaugural lecture by Morten H. Hansen Winner of the PhD Annual Award in renewable energy The theme was Innovation and cost saving and DNV-GL announced Nikola Vasiljevic from DTU Wind Energy as winner of the award for his PhD thesis: A time-space synchronization of coherent Doppler scanning lidars for 3D Measurements of wind fields, during the EWEA Conference. With the award comes a 5000 euro cash prize. Senior researcher Morten Hartvig Hansen was appointed professor in Aero-servo-elasticity and Dynamics of Wind Turbines at DTU Wind Energy and held his inaugural lecture as professor 10 April 2015 with the title: Aero-servo-elasticity and Dynamics of Wind Turbines

7 ANNUAL REPORT 2015 HIGHLIGHTS 7 APRIL APRIL DTU Wind Energy participated in the Dutch state visit and they accompanied the business delegation Deputy Head of Department, Peter Hjuler, participated in a reception with the Dutch businesses hosted at The Danish Society of Engineers facilities in Copenhagen. The Danish crown prince couple visited Samsø together with the Dutch royal couple where Kenneth Thomsen participated and accompanied the business delegation when the Department of Wind Energy held a short presentation for the delegation. New research wind turbine erected at DTU Risø Campus The new V52 wind turbine was erected at DTU Risø Campus at the end of April and many people were involved in the work. APRIL APRIL Forskningens Døgn at DTU Lyngby Campus Forskningens Døgn in Roskilde DTU Wind Energy participated in Forskningens Døgn at DTU Lyngby Campus where PhD students and researchers introduced high school pupils to scanner lidars, meteorology and the wind car racer. For the first time, DTU Wind Energy participated in Forskningens Døgn in the city of Roskilde. Students and researchers talked with the citizens passing by about the power of the wind and climate. JUNE Open House event at DTU Risø Campus After more than 20 years without building new wind turbines at Risø, a new turbine was erected. More than 80 people participated in the open house event that took place 17 June, where Anders Bjarklev, president of DTU and Peter Hauge, Head of Department inaugurated the new research wind turbine.

8 8 HIGHLIGHTS ANNUAL REPORT 2015 JULY AUGUST DTU Wind Turbine Racer wins the race The Aeolus Race event for wind turbine and mechanically driven took place in August at Den Helder, In Holland. It was a super event for the DTU team, the wind was weak and it s usually a disadvantage for the cars from DTU, but the final points count showed the mechanically driven car got a surprising first place in front of strong competitors. International Conference on Composite Materials In July 2015, Copenhagen hosted more than 1800 researchers and scientists in the field of composite materials where the 20th International Conference on Composite Materials (ICCM20) took place under the title: Sustainable Composite Solutions to Global Challenges. SEPTEMBER Wind Energy Denmark Annual Event in Herning In September colleagues from DTU Wind Energy participated in Wind Energy Denmark s Annual Event with presentations of their works. During one session, Innovation Manager, Kenneth Thomsen presented the new sector development report. The project highlighted the challenges and barriers of the research collaboration with small and medium sized enterprises. OCTOBER OCTOBER EAWE awards to DTU researchers This year both awards from the European Academy of Wind Energy (EAWE) went to DTU researchers at the annual EAWE PhD Seminar in Stuttgart. The Scientific Award went to Professor Jens Nørkær Sørensen (DTU Wind Energy) for his many contributions to wind energy research. The Excellent Young Wind Doctor Award went to Emmanuel Branlard (DTU Wind Energy) for his thesis on rotor aerodynamics. DANSIS Graduate award to Floating wind turbine project The annual DANSIS graduate award winner was announced in October 2015 and this year Anders Mandrup Hansen and Robert Laugesen, former MSc students at DTU Wind Energy, won the award. The award committee, headed by chairman of DANSIS Assoc. Prof. Knud Erik Meyer, selected the project by Anders and Robert among 6 nominated projects of very high quality within the field of applied industrial fluid dynamics.

9 ANNUAL REPORT 2015 HIGHLIGHTS 9 Launch of Global Wind Atlas A global wind atlas for improving global wind power utilization was launched in October. DTU Wind Energy played a key role in developing the wind atlas, a free tool for world energy planners. The global wind atlas is a tremendous asset for all nations looking to explore the possibilities for wind energy. NOVEMBER NOVEMBER Ministerial visit to DTU Wind Energy In November, the Danish Minister for Energy, Utilities and Climate, Lars Christian Lilleholt, visited DTU Risø, among other things to learn more about how to store energy, and to discuss perspectives of Danish wind energy research. At DTU Wind Energy, Peter Hauge Madsen, Head of Department, showed the minister some of the research areas which have helped Denmark become a leader in the field of wind energy research. EWEA Paris During this year s EWEA Conference, DTU Wind Energy invited stakeholders, partners and others to listen to presentations about WindScanner.eu and the Global Wind Atlas DECEMBER DECEMBER Jens Nørkær Sørensen In December Jens Nørkær Sørensen defended his doctor thesis: General Momentum Theory for Horizontal Axis Wind Turbines. The research of the aerodynamics of rotors has contributed significantly to the successful development of the modern wind turbine. Vivid public meeting in Østerild 8 December a vivid debate unfolded at the public meeting about lights at the national test centre at Østerild. Julia Kirch Kirkegaard and Niels- Erik Clausen represented DTU Wind Energy at the meeting. The aim of the public meeting was to inform the local community about the preliminary findings from the research project CORAL which aims to understand how and whether the obstruction lights installed on the two 250-metre high light masts at the test centre affect the local community.

10 10 RESEARCH AND INNOVATION ACTIVITIES ANNUAL REPORT 2015 Floating wind turbine in waves and wind Test of a 10 MW floating wind turbine for extreme weather conditions in a laboratory facility. The floating wind turbine in the wave basin of DHI. Offshore wind energy expands heavily these years. For depths above 60 m, where bottom fixed solutions become infeasible, floating wind turbine technology offers an attractive solution. Today, only a handful of full-scale floating wind turbines exist and research into their dynamics in waves and wind is needed. DTU Wind energy is involved in several international projects on floating wind turbines. One of them is INNWIND.EU on innovative wind turbine technology for MW wind turbines. As part of this research, a 1:60 scaled model of the DTU 10 MW reference wind turbine on a tension leg platform (TLP) was tested in January Special wind conditions and a new rotor In floating wind turbine tests at scale 1:60, the wind speeds become very low. Down to about 1 m/s, says Robert Mikkelsen, senior researcher at DTU Wind Energy. Therefore a re-design of the rotor is necessary, in order to achieve the correct thrust force on the model. Also, a new rotor was designed and built in carbon fibre. Besides that a

11 ANNUAL REPORT 2015 RESEARCH AND INNOVATION ACTIVITIES 11 Close-up of the floater in water. Rotating turbine in front of the 4 m x 4 m wind generator. special nacelle was developed, which allowed control of the rotational speed and the blade pitch angle. The wind generator was constructed from six existing fans of DHI. Each of them was built into a new plywood box which turns the flow and produces a wind field over an area of 4 m x 4 m. This is enough to cover the rotor which is 3 m in diameter. Top-class master students The main work was carried out by Anders Mandrup Hansen and Robert Laugesen, two MSc students. During 2012 they got experience with windwave testing of floating wind turbines, as part of their bachelor project in scale 1:200. Anders and Robert did a great job, says Henrik Bredmose, associate professor. They built a wind generator, designed the floater, executed all the tests and processed all the test results. After the project, the students were awarded the DANSIS Graduate award for the best MSc project in 2015 on industrial fluid mechanics. Dynamics in wind and waves The purpose of the experiments was to investigate the dynamics of the TLP floating wind turbine in wind and waves simultaneously. Several coupling effects exist, and although many of them are included in aero-elastic models for computation of the motion, the physical tests provide new insight and offer validation of the numerical models. One of the effects we looked at is aerodynamic damping, where the operating rotor leads to a damping of the wave-induced tower top motion, explains Henrik Bredmose. In this way, the presence of the wind helps to reduce the dynamic loads. The tests confirmed this phenomena and tests in misaligned wind-wave conditions were further conducted to quantify to what extent the damping is reduced when the wind and wave directions are different. Industry collaboration and new tests Several industrial partners were involved in the tests. Research engineer, Nicolai F. Heilskov from DHI Denmark was co-supervisor and will validate a CFD model for floater motion against the measurements. Also DNV GL, partner in INNWIND.EU will make use of the test data. The experiments of DTU are impressive and provide important results for floating wind turbine dynamics in simultaneous wind and waves, says Andreas Manjock, Principal Engineer at Section Offshore Loads, DNV GL Energy. For the certification of floating wind projects we need reliable simulation tools taking the complex interaction of wind and wave loading into account. We will use the test results for validation of our in-house calculation tools. This is something we look forward to do in collaboration with DTU. At DTU, Robert Mikkelsen and Henrik Bredmose are planning a new set of tests. Together with University of Stuttgart and CENER from Spain we will investigate details of real-time pitch control of the blades and the motion response of the newly designed INNWIND.EU floater says Henrik Bredmose. We also look forward to quantified results on the loads and dynamics for this new setup. Surge response in eight sea states. The plot shows exceedance probability of movement in wave direction.

12 12 RESEARCH AND INNOVATION ACTIVITIES ANNUAL REPORT 2015 Innovative monopile design for large wind turbines installed at 50 m water depth A large diameter monopile (XL monopile) has been conceptually designed to support the DTU 10 MW wind turbine as installed at a water depth of 50 m. BY NJOMO WILFRIED WANDJI, ANAND NATARAJAN, NIKOLAY DIMITROV, THOMAS BUHL Present offshore turbines installed on monopiles are limited to water depths of less than 35 m. Moving to deeper waters is conventionally thought to require jackets or other substructures, but herein the monopile solution is assessed to be feasible at 50 m water depth for 10 MW wind turbine capacities. The design of this large diameter monopile at 50 m water depth was carried out by jointly designing the wind turbine tower and monopile considering manufacturing constraints and understanding soil plastification or the inability of the soil to support dynamic loading beyond a certain deflection of the pile. An appropriate design scheme for the XL monopile was developed from Comparison of the XL monopile at 50m water depth (right) with a traditional monopile at 26 m water depth (left). TOWER A Water depth = 26 m OD = 8.0 m WT = 120 mm Emb. depth = 30 m 8.0 / 100 mm 40 m 8.0 / 120 mm 30 m TOWER B Water depth = 50 m OD = 9.5 m WT = 110 mm Emb. depth = 30 m 10.0 / 120 mm 30 m 9.5 / 110 mm 30 m these assessments, which satisfies the criteria to avoid excitation of its natural frequencies by the rotor or by waves and to distribute the bending stiffness effectively along the entire support structure. Small changes (perturbations) to the design configuration such as on the length of the monopile below the soil, the fixity of the end point below the soil, variations in bending and axial soil stiffness have been carried out to understand their influence on the monopile load bearing capacity. This design was presented at the EWEA Conference 2015 in Pamplona, following which Qvartz consultancy QVARTZ Ryesgade 3A, 2200 Copenhagen) expressed great interest in the presented results of the XL monopile as a potential winning offshore foundation technology in a 2020 to 2025 perspective. Further studies are being made now to investigate if proper consideration of soil resistance to yaw loads can aid in the structural design of the monopile in addition to the influence of soil skin friction.

13 ANNUAL REPORT 2015 RESEARCH AND INNOVATION ACTIVITIES 13 Improved wind inflow models make for a robust design of tall wind turbines The research project named Demonstration of a Basis for Tall Wind Turbine Design showcased improved wind inflow models that are applicable in the design phase of large wind turbines. BY ANAND NATARAJAN, NIKOLAY DIMITROV, JACOB BERG, GUNNER LARSEN, JAKOB MANN, MARK KELLY This research demonstrated the impact of wind inflow in the range between 100 m and 200 m height above ground on wind turbine design loads through measurement of atmospheric characteristics at different wind sites in Europe and North America. Using the measurements as a validation tool, a detailed assessment of turbulence models and partial safety factors using reliability-based procedures were made which jointly incorporate the new models to be used in the design phase of large wind turbines. PROJECT TITLE: DEMONSTRATION OF A BASIS FOR TALL WIND TURBINE DESIGN YEAR START-END: PARTNERS: AAU, DONG ENERGY, SIEMENS WIND POWER, VESTAS WIND SYSTEMS, SU- ZLON, DNV-GL, MITA TEKNIK FUNDING: EUDP FUNDED PROJECT. The results from the project were presented at the committee meetings focused on the development of the next version of the IEC design standard. Consequently large multi megawatt turbines being designed today can benefit from the results of the project by considering the developed wind inflow models in conjunction with required design load cases in the standard. Using a more appropriate inflow model is an important factor for reducing the uncertainty in design load calculations which in terms results in improved reliability or reduced material costs. The project was completed in 2015 and based on to its findings; DNV-GL initiated a Joint Industrial Project (JIP, Reference [1]) which enables wind turbine manufacturers and wind farm owners to utilize the project-recommended wind conditions and methods to compute the design loads envelope of commercial wind turbines. During the JIP, DNV-GL and participating industries will analyse further wind measurements from more sites to validate and explore the impact of the proposed models by DTU on the design of commercial wind turbines. Return period contours for the joint probability distribution of wind speed and turbulence. Dashed lines represent measurements, and solid lines represent model estimates.

14 14 RESEARCH AND INNOVATION ACTIVITIES ANNUAL REPORT 2015 In this house there are a fan driving the flow and a cooling surface keeping the temperature below 30 C. In this house are the test section, the anechoic chamber, the control room and the workshops Entrance Figure 1 Illustration of the wind tunnel. The tunnel is made of concrete and is of the closed-loop type, where the flow is re-circulated indicated by the arrows. Detailed design of the Danish National Wind Tunnel The design of the Danish National Wind Tunnel was finalized in 2015 and in 2016 the tunnel will be constructed. The tunnel is dedicated wind energy and measurements of aerodynamic performance and aerodynamic noise will be carried out. FACTS ABOUT THE WIND TUNNEL TITLE: THE DANISH NATIONAL WIND TUNNEL FUNDING: DKK 40 MILLION GRANT FROM THE MINISTRY OF HIGHER EDUCATION AND SCIENCE, DKK 4 MILLION GRANT FROM REGION SJÆLLAND DTU S OWN CONTRIBUTION OF DKK 30 MILLION. PERSONS AND INSTITUTIONS INVOLVED IN THE AIRLINE DESIGN DTU RESPONSIBLE: CHRISTIAN BAK (DTU WIND ENERGY) AND ALLAN MURPHY (DTU CAMPUS SERVICE) OVERALL PROJECT MANAGEMENT AND BUILDING DESIGN: ALECTIA A/S, DENMARK AERODYNAMIC DESIGN OF THE TUNNEL: FLUID THINKING AB, SWEDEN ACOUSTIC DESIGN OF THE TUNNEL: CREO DYNAMICS AB, SWEDEN BY CHRISTIAN BAK One important objective at DTU Wind Energy is to carry out research to contribute to the reduction of the cost of energy for wind turbines. One way is to increase the energy production and therefore reliable and high aerodynamic performance is very important. DTU and wind turbine manufacturers have for many years carried out experiments e.g. in wind tunnels to validate new designs and simulation tools. However, since the size of wind turbines is increasing and the requirements for flow quality and noise emission are increasing, DTU suggested the establishment of the Danish National Wind Tunnel that can match these requirements. In the process of designing the wind tunnel many decisions have to be taken since such a design is not an off-the-

15 ANNUAL REPORT 2015 RESEARCH AND INNOVATION ACTIVITIES 15 shelf item. The size was decided in cooperation with the stakeholders in Denmark. Taking the cost of testing into account it was decided to aim at a test section with a maximum flow speed of 105 m/s (378 km/h) through a cross sectional area 3 m wide and 2 m high and with very low turbulence intensity that is smaller than 0.1%. The consultancy company Alectia and engineers from Sweden with experience in wind tunnel design, acoustic designs and noise predictions, made a basic tunnel design matching our requirements. It was decided to position the 65 m long and 27 m wide tunnel at DTU Risø Campus south of building 313. During 2015 almost all components were put to tender and all the challenges in the construction of the wind tunnel were solved. In this process also laboratory tests were carried out of the acoustic absorption and aerodynamic performance of guide vanes that are wing sections that turns the flow in the corners. Below an illustration of the wind tunnel is shown, Figure 1. Also, in 2015 the test section and the area around the test section were designed, where the workflow, safety, measurement techniques and procedures were considered. Here wing sections, model rotors and other components exposed to wind will be tested. Below a sketch of the planned test section and the anechoic chamber is shown, Figure 2. The wind tunnel will be constructed in 2016 and will be finalized by the end of the year. DESIGN OF THE TEST SECTION AND ANECHOIC CHAMBER DTU WIND ENERGY: ANDREAS FISCHER, ROBERT MIKKELSEN, ANDERS S. OLSEN, MAC GAUNAA, WITOLD SKRZYPINSKI, THANASIS BARLAS DTU CIVIL ENGINEERING: HOLGER KOSS FORCE TECHNOLOGY: SØREN V. LARSEN Walls, floor and ceiling to avoid reflections and absorb noise Contraction accelerating the flow FLOW FLOW The test section where models are mounted Figure 2 Sketch of the planned test section and the anechoic chamber. In the test section the flow can reach 378 km/h.

16 16 RESEARCH AND INNOVATION ACTIVITIES ANNUAL REPORT 2015 Exploring the design of the Olsen Wings 14.3 m blade A wind turbine blade optimization software, HAWTOPT2, developed in-house at DTU Wind Energy was used in a cooperation project with Olsen Wings to explore the design of the 14.3 m blade. The study showed an increase in energy production of approximately 10% without increasing the mass and the extreme loads relative to a Vestas V27. Figure 1 Prediction of the structural performance of a 14.3 m blade. BY CHRISTIAN BAK, FREDERIK ZAHLE, PETER BERRING Trailing edge part Spar cap For more than two decades DTU Wind Energy has developed the methodologies for aeroelastic design of wind turbine blades. With these methodologies the energy production can be maximized while constraining the blade mass and loads on the blades and the entire wind turbine. Such methodologies are important because we need to maximize the energy production while the cost of the construction needs to be limited in order to minimize the cost of energy. In cooperation with Vestas Wind Systems an updated methodology was developed based on the simulation tool OpenMDAO. Based on this tool a general tool, FUSED-Wind, for wind turbine analysis and optimization was developed. Also another tool, HAWTOPT2, dedicated optimization and design of horizontal axis wind turbine blades was developed. Shear webs Figure 2. Detailed design of a section of the 14.3 m blade.

17 ANNUAL REPORT 2015 RESEARCH AND INNOVATION ACTIVITIES 17 Using the HAWTOPT2 tool the design of the Olsen Wings blade with a length of 14.3m mounted on a 30 m-diameter rotor was explored. For this blade an important requirement was that it should be able to replace blades on 27 m-diameter rotors. Thus, even though the 14.3 m blades will sweep an area 23.5 per cent greater than the older generation blades they will replace, the loads that the turbines were originally designed for should not be exceeded. TITLE: EXPLORATION OF THE DESIGN OF A 14.3 M BLADE PARTNER: OLSEN WINGS A blade with this performance is seen below, Figure 1, where the deflection at maximum load is predicted and visualized with blue colour as small displacements and red as big displacements. The predicted aerodynamic performance for a rotor with these blades shows that the annual energy production will increase with around 10% depending on the control scheme for the wind turbine and the mass and the extreme loads did not increase relative to the Vestas V27 blade. Also, details of the structural lay-up of the blade were explored, where the internal part of the blade such as the placement of the shear webs, the thickness of the spar cap and the trailing edge part of the blade section were investigated to ensure sufficient resistance to e.g. buckling. Based on the exploration of the blade design Olsen Wings manufactured the blade, which is now named OLW 1430 and can be seen below, Figure 3. The work made by DTU Wind Energy is of great value to Olsen Wings and as Head of Development Søren Olsen stated: The exploration studies carried out by DTU Wind Energy with their newest tools made a big difference and made it possible for us to design and manufacture a very modern and highly competitive blade. Figure 4 The manufactured OLW 1430 blade tested in an outdoor test facility using a crane to pull the blade Figure 3 The manufactured OLW 1430 blade in the workshop.

18 18 RESEARCH AND INNOVATION ACTIVITIES ANNUAL REPORT 2015 Wind Turbine The noise received by a neighbour to a turbine is the result of a chain of complex physical mechanisms comprising the noise generation, propagation and perception. By a multidisciplinary research, DTU is now able to model this chain and contribute to minimize the noise impact from wind turbines.

19 ANNUAL REPORT 2015 RESEARCH AND INNOVATION ACTIVITIES 19 Rotor Noise from source to receiver PROJECT: INTERNAL PROJECT AT DTU WIND ENERGY CROSS CUTTING ACTIVITY NOISE INTERNAL DTU FUNDING: DKK 2.3 MILLION PERIOD: 2015 BY H AA MADSEN, W Z SHEN, T K MIKKELSEN, F BERTAGNOLIO, A FISCHER, W J ZHU, F RASMUSSEN New wind turbine projects are often met with scepticism from the public due to wind turbine noise, even though they have a positive attitude towards wind energy. DTU works towards a better understanding of wind turbine noise. The aim is to improve the knowledge and modelling in order to decrease the annoyance from wind turbine noise and eliminate its impact on the acceptance of wind energy in the society. Wind turbine noise might be perceived in the neighbourhood of a wind turbine or wind farm as having its origin from the rotating blades of a turbine. It starts within the flow very close to the blade surface called the boundary layer. When the flow passes the trailing edge of the blade, noise is emitted in the surrounding air. Only a fraction of the noise propagates directly to the receiver. The noise propagating in any other direction to the receiver might hit the ground and be reflected, or it can even under certain weather conditions be refracted by layers in the atmosphere some hundred meters above us. Part of this refracted sound can then also finally propagate to the receiver. Our research has provided simulation models for the rotor noise sources, for the propagation and for the atmospheric flow in which the sound propagates. We can predict the noise at the receiver taking into account the most important parameters such as landscape and weather conditions. In the parallel experimental work we use microphones at different positions within the chain from the blades to receiver to provide experimental data by which we can check how well our models perform. Our next goal is to demonstrate the tools on real life locations, and how the noise and it s annoyance can be reduced. WIND & TURBULENCE GEOMETRICAL SPREADING & ATMOSPHERIC ABSORPTION TERRAIN TEMPERATURE GRADIENT & HUMIDITY The illustration shows the noise generated by the wind turbine blades propagating towards a neighbourhood, experiencing a complex interaction with the terrain and atmosphere which makes the modelling of the perceived noise challenging.

20 20 RESEARCH AND INNOVATION ACTIVITIES ANNUAL REPORT 2015 How and why blade materials fail in fatigue Innovative research work in manufacturing processes and damage mechanisms of composite materials have provided ground-breaking knowledge of mechanisms leading to fatigue failures in wind turbine blades. BY POVL BRØNDSTED AND LARS P. MIKKELSEN One of the major properties limiting the life-time of wind turbine blades is the fatigue properties of the materials and of the individual substructures such as main spar, web, shell, leading and trailing edges. Fatigue damage initiates from microstructural defects, (cracks and voids) already emerged during the manufacturing. Blades are made from glass fibre reinforced plastic, where dry architecture glass fibre matts (fabrics) are stacked and packed into moulds giving the shape of the blade where after a very low viscous liquid polymer resin (e.g. epoxy) is infused in the glass package. Our research has demonstrated how stresses are built up throughout the hardening (curing) of the resin. As the resin hardens it will contract (shrink), however, the glass fibre cannot contract Figure 2. Butterfly shaped fatigue test specimen tested with infrared camera with indication of scanned region. and therefore the structure will not allow for this contraction. Hence, stresses build up in the resin result in cracks in the fibre structure. Thereafter, when the blade structure in use is loaded these cracks will slowly grow, initiating more cracks in the glass fibres leading to larger damage end-of-life. The models and the postulated damage progress, Fig. 1, were experimentally demonstrated and validated through fatigue tests in the DTU Wind test laboratory, Fig 2, and by subsequent studies of the crack patterns using advanced microscopy and X-ray tomography, Fig. 3. This has led to deeper studies of the basic constituents. The curing progresses are addressed with a focus on the resin performance and chemistry, and the individual fibres are addressed with a focus on surface treatment and stiff-

21 ANNUAL REPORT 2015 RESEARCH AND INNOVATION ACTIVITIES 21 PARTNERS: LM WINDPOWER, WIND TURBINE BLADE MANUFACTURER SIEMENS WIND POWER, WIND TURBINE MANUFACTURER OWENS CORNING, GLASS FIBER MANUFACTURER REICHHOLD, RESIN MANUFACTURER Figure 1. Postulated fatigue damage mechanism responsible for the experimental observed stiffness drop during mechanical fatigue test. (a) Initial stiffness drop related to transverse cracking of the backing bundles. (b) Transverse cracks are spreading into the load carrying fibres. (c) Near the end-of-life were the remaining undamaged fibres are reaching the overall static strength. ness. The compatibility between fibre and glass is optimized, and the glass mats and the solidified composites are addressed with a focus on architecture. The recent 3-5 years of research demonstrate these aspects and this realization and the understanding of the mechanism have been carried out in a close collaboration with industry. It has been brought into application and is used in industrial applications to optimize the materials, the composite architecture, and the manufacturing parameters. Figure 3. (a) Scout (15x15x4.5mm 3 ) and zoom (2.5x2.5x2.5mm 3 ) scan using 3D X-ray computerized tomography. (b) Observed fibre failure supporting the fatigue damage evolution postulate shown in figure 1. The advanced experimental facilities available in the DTU Wind Energy laboratories have made these sensational demonstrations possible. Especially the recent establishment of modern advanced test machines and CT scanning as part of the Villum Centre for Advanced Structural and Material Testing in the DTU Wind Energy test laboratory is acknowledged.

22 22 RESEARCH AND INNOVATION ACTIVITIES ANNUAL REPORT 2015 Trailing edges breaking bad 3-D finite element model simulating four point ultimate test of 34 m long blade, Red contours indicate failure stress concentrations in trailing edge due to local buckling. BY M.A. EDER, P.U. HASELBACH, F. BELLONI Wind turbine rotor blades are amongst the most delicate components of wind turbines. Their shape and material inventory are optimised towards high aerodynamic and structural performances. During their expected lifetime of 20 to 25 years, rotor blades accumulate a vast number of load reversals which may lead to various forms of damage due to high structural utilisation. Jonathan A. Shmueli from DONG-Energy states: Failure of adhesive connections is common in blades representing a significant share of the total cost of a wind turbine. Especially the limited access to off-shore sites increases O&M costs due to blade repair and wind turbine downtime. Wind turbine rotor blade testing and structural analyses are two essential and inseparable parts of research aiming at increased reliability leading to lower cost of energy. Striving for increased durability, DTU Wind Energy pursues interdisciplinary research in order to scrutinise the root causes for blade failure. Full scale tests in conjunction with novel measurement approaches such as the stereo photogrammetry based Small Displacement Measurement System and Fibre Bragg optics, were used to isolate important effects such as prevailing fracture modes and unstable wave formation in the trailing edge. The combined use of nonlinear finite element based fracture analysis facilitates the understanding of the mechanisms behind the preceding effects. These findings are stirring the development of more damage tolerant materials and improved manufacturing techniques. Identification of critical load directions associated with different design features e.g., the airfoil camber on warping deformation and local buckling induced debonding increase the confidence of tomorrow s blade designs. The latter decreases manufacturing costs by more efficient material usage simultaneously decreasing cost of energy by enhancing service-life.

23 ANNUAL REPORT 2015 RESEARCH AND INNOVATION ACTIVITIES 23 Improved adhesive joints for wind turbine blades Wind turbine blades are made of adhesively bonded composites. Knowledge about the mechanical interaction between the adhesive and the composite is crucial for new designs of blades. Fracture mechanics test with adhesively bonded composites. The test gives fundamental knowledge of both initiation and propagation of cracks. Recorded data is evaluated and used for simulations of larger structures. BY ANDERS BIEL One critical part of wind turbine blades is the adhesive joint at the trailing edge. Cracks may start from the inside of the blade and propagate along the edge. In this project, loading conditions for the trailing edge is used as a case study. DTU Wind Energy has entered into cooperation with BASF. BASF is the leading chemical company and global partner in innovative as well as high-quality solutions for the wind energy industry. In the current project we focus on the mechanical behaviour of adhesives joints. DTU performs and evaluates experiments on materials supplied by BASF. The main targets of the project are to derive material models for different types of new adhesives and to demonstrate their performance on a subcomponent. Simulations with reliable material data are important when designing new blades. We enjoy partnering with DTU in the field of wind energy. It is not only the technical skills and experience of theworld s leading wind research department, but the right chemistry between people openness, trust, interdisciplinary and innovative thinking." "Via the cooperation, we target a holistic understanding for adhesive joints from chemistry to performance to design and application. The key aims include to test as well as simulate the reliability of adhesive joints on a realistic scale, to implement our advanced adhesive solutions and to provide a pathway for our customers to new designs, says Holger Ruckdaeschel, Advanced Materials & Systems Research, System Integration Group Wind Energy, BASF. PROJECT TITLE: SUB-COMPONENT ANALYSIS FOR ROTOR BLADES DURATION: COOPERATION BETWEEN BASF AND DTU FUNDED BY BASF

24 24 RESEARCH AND INNOVATION ACTIVITIES ANNUAL REPORT 2015 Metallurgical issues in wind turbines The metallurgical R&D encompasses studies of metal structures, properties and performance of metallic components in wind turbines. Focus areas are gears, bearings, cast iron components, bolts, towers and foundations. Two examples of the work are given below: White etching cracks cause bearing failure White Etching Cracks (WEC) are a critical but poorly understood failure mode caused by internal cracks found in large bearings. For example, Vestas Wind Systems regards WEC as the all-time single most expensive failure mode amongst their wind turbine components. Therefore, DTU Wind Energy has started research into this failure mechanism, using state-of-the-art characterization techniques. X-ray computed tomography enables 3D representations of WEC, revealing the morphology of the crack network and how it interacts with microscopic defects such as inclusions. A better understanding of the failure mechanism will lead to improved criteria for bearing design and materials selection, key issues for an increase in wind turbine reliability. Corrosion and fatigue cause bolt failures Bolts are important joining components of wind turbines. During service bolts are exposed to a great number of load cycles which may lead to catastrophic failure, such as collapse of the wind turbine. By investigating broken bolts from failed wind turbines, it has been found that galvanized bolts (i.e. bolts coated with Zn) are very vulnerable to fatigue crack initiation. We are currently investigating alternative corrosion protection systems which have better resistance to fatigue crack initiation, thereby reducing the risk of failures and increasing the lifetime of wind turbines. Fig.1. X-ray computed tomography image of a 600µm long WEC in a bearing. The WEC is shown in red, while inclusions are shown in blue BY DR. HILMAR KJARTANSSON DANIELSEN, DR. OLEG MISHIN Fig.2. Cross-section of a galvanized bolt taken from a wind turbine. Multiple cracks are observed in the Zink layer (bright), some of which penetrate into steel (gray), marked by arrows.

25 ANNUAL REPORT 2015 RESEARCH AND INNOVATION ACTIVITIES 25 National Test Centre at Østerild,

26 26 THE DTU GLOBAL WIND ATLAS ANNUAL REPORT 2015 The DTU Global Wind Atlas In October 2015, the DTU Global Wind Atlas was launched. A new high resolution view on wind resources over the world is now available for free. BY JAKE BADGER Up until the launch of the Global Wind Atlas, policy makers and energy planners tackling the challenges of climate change, and seeking approaches for climate change mitigation, had no global wind resource dataset appropriate for their pressing needs. Coarse resolution datasets have had the serious shortcoming that the wind energy resource is underestimated because effects of small scale terrain features are missing. The Global Wind Atlas captures these effects, and resolves the windiest sites. Even in simple terrain estimates of wind resource may be increased by one fifth and for complex terrain the wind resource may be doubled. This project is built on a global methodology. It is the new and improved meteorological datasets and topographical datasets, in the 2.5 BILLION LOCATIONS, 3 HEIGHTS, 12 DIRECTION SECTORS OVER LAND AND 30 KM OFFSHORE CALCULATION EVERY 250M public domain, that made this project possible. The method employs largescale global meteorological datasets that are downscaled to high-resolution wind resource datasets. A new application of the flow models in our Wind Atlas Analysis and Application Program (WAsP) allows calculation of high-resolution resource maps covering extensive areas. For the purpose of downscaling high-resolution datasets, appropriate surface elevation and roughness lengths have been derived from global surface elevation and land cover datasets. The application of geospatial information systems (GIS) and web-based tools help significantly to bring the Global Wind Atlas datasets alive to end-users, the end-users can analyse spatial and temporal distributions of wind resources in areas of interest determined by the end-user. Either by specifying ad-hoc areas or by selection of areas following administrative boundaries. Furthermore, through the International Renewable Energy Agency (IRENA) Global Atlas for Renewable Energy the end-user is able to relate the wind resources to other factors, such as population centres, electrical transmission grids, terrain types, and protected land areas. During the launch of the Global Wind Atlas, the following citations were given: IRENA Director-General Adnan Z. Amin. The new Global Wind Atlas provides this needed data directly and for free, making it a ground-breaking tool to help jumpstart wind energy development worldwide. The release of the Global Wind Atlas demonstrates the support of the international community to expand global renewable energy to address global climate change, increase electricity access and stimulate economic development, said Danish Minister for Energy, Utilities and Climate, Lars Christian Lilleholt.

27 ANNUAL REPORT 2015 THE DTU GLOBAL WIND ATLAS 27 The Global Wind Atlas is not a substitute for individual country-based wind atlases or wind resource assessment conducted commercially for wind farm developers. For that a higher precision, a specific configuration for the region in question, and a more stringent validation phase is required. Currently the Global Wind Atlas data is the most appropriate global wind resource dataset available for the needs of policy makers, energy planners, the Integrated Assessment Modelling (IAM) community and for Strategic Environmental Assessment (SEA). FACTS ABOUT THE GLOBAL WIND ATLAS PROJECT DTU WIND ENERGY HAS DEVELOPED THE METHODOLOGY AND CARRIED OUT THE WORK IN THE FRAMEWORK OF THE CLEAN ENERGY MINISTERIAL MULTILATERAL WORKING GROUP ON SOLAR AND WIND TECHNOLOGIES SUPPORTED BY THE DANISH ENERGY AGENCY. THE DTU WIND ENERGY CONTRIBUTION HAS BEEN MADE STRONGER BY THIS INTERNA- TIONAL COLLABORATION, BECAUSE LEADING INTERNATIONAL INSTITUTIONS HAVE SHARED VALUABLE KNOWLEDGE AND LIAISED ON THE DATA SPECIFICATIONS, APPLICATIONS, AND DISSEMINATION OF THE DATA TO A LARGE AND BROAD RANGE OF END-USERS. NEW PROJECTS AND COLLABORATIONS HAVE BEEN TRIGGERED BY THIS NEW DATA SET, INCLUDING THE PROVISION OF WIND RESOURCE DATA FOR ENERGY MODELLERS AT THE EU JOINT RESEARCH CENTER PETTEN IN PARTNERSHIP WITH ECN (NETHERLANDS) AND DLR (GERMANY). FUNDING FROM EUDP 11-II, GLOBALT VIND ATLAS, Data about Global Wind Atlas PUBLIC LEARN ABOUT RESOURCE MAPPING POLICY MAKERS IS THERE RESOURCE IN MY COUNTRY OR REGION PLANERS HOW MUCH RESOURCE AND WHERE DEVELOPERS EMERGING MARKETS FIRST VIEW OF WIND CLIMATE MODELLERS INPUT DATA AND METHODOLOGY SERVERS

28 28 RESEARCH AND INNOVATION ACTIVITIES ANNUAL REPORT 2015 WindScanner sees the wind WindScanner.eu is a new unique European distributed, mobile research infrastructure. It is established to address the needs of the European wind energy community for measurements of the 3D wind fields surrounding todays huge wind turbines, wind farms, bridges, buildings, forests and mountains. Detailed measurements are essential to optimize wind turbine design and siting, and is an important driver for making wind energy cheaper and more reliable for the benefit of society. BY TORBEN MIKKELSEN, NIKOLA VASILJEVIC The WindScanner infrastructure builds upon recent advancements in remote sensing based wind-measuring technology to create measurement techniques. WindScanners enable the facility to scan and quantify wind flow and turbulence as wind fields in two and three dimensions from scans across various terrains. As well as being deployed onshore, the infrastructure can be operated offshore from stable and floating platforms or by doing measurement of near-coastal wind farms. The European WindScanner facility was included in the ESFRI Roadmap for research infrastructures of pan-european interest in 2010, recognizing the scientific merit and European added value. The European Commission has supported the preparation of the Research Infrastructure, which will be developed and implemented in the coming years. WindScanner can become for the wind industry, what X-Ray became for the medical sector. For the first time it s possible to unmask the complex and up to now basically invisible turbulent flows in and around wind farms. By joining forces, knowledge and lidar systems in a distributed research infrastructure we can literally switch on the light in the black box, which the resource wind in many aspects is still today. Says Dr. Stephan Barth, Managing Director, ForWind Center for Wind Energy Research, Germany. The Perdigão 2015 field experiment was part of the WindScanner.eu project pooled with other research project groups. The objective of the field experiment was to couple and increase the ex- Research technicians engaged with installation of small wind lidar telescopes (Lidic s) on the blades of a test turbine located at Tjæreborg Enge, Denmark