En ökad energianvändning, tillsammans med utbyggnaden av vindkraft, förväntas leda till ökade avfallsmängder från uttjänta vindturbinblad och krav på en hållbar hantering över hela värdekedjan. Komplexiteten i materialen som används i vindturbinbladen försvårar återvinningen, vilket leder till att majoriteten av bladen hamnar på deponi med både miljöföroreningar och resursförluster som resultat. Studien syftar till att undersöka möjligheterna och utmaningarna med återanvändning av vindturbinblad till olika tillämpningsområden genom att utvärdera befintlig forskning samt genomförda och potentiella projekt, med fokus på miljömässiga, tekniska och ekonomiska aspekter. Data samlades in genom både kvantitativa och kvalitativa metoder, vilket omfattar litteraturstudier och semistrukturerade intervjuer med relevanta aktörer inom vindkrafts- och återvinningsindustrin. Metoden innefattar även en SWOT-analys och en fallstudie som undersöker återanvändning av vindturbinblad i Umeå kommun, inklusive en undersökning av kommunens marknadsbehov samt vilka möjligheter och utmaningar potentiella aktörer ser kring återanvändningsprocessen. De sammanlagda resultaten från litteraturstudie, intervjuer och SWOT-analys visar på flera tekniska, ekonomiska och miljömässiga möjligheter med återanvändning av vindturbinblad, inklusive möjligheten att potentiellt minska både materialkostnader och växthusgasutsläpp jämfört med alternativen förbränning eller deponering. Flertalet utmaningar identifierades, inklusive utmaningar kring nedmontering, transport, testning av materialets styrka samt brist på information kring materialets innehåll. Även ekonomiska och logistiska hinder kring ansvar hos tillverkare och verksamhetsutövare samt bristen på samarbete för att skapa en effektiv värdekedja konstaterades. Resultatet lyfter betydelsen av samarbete mellan aktörer, tillverkare och avfallshanterare som avgörande för att skapa effektiva lösningar och möjliggöra återanvändning av vindturbinblad. Fallstudien av Umeå kommuns marknadsbehov visar att återanvändning av vindturbinblad skulle kunna täcka en betydande del av kommunens behov för lekplatser, gångbroar och stadsmöbler och samtidigt bidra till en besparing av koldioxidutsläpp. Trots ekonomiska, tekniska och logistiska utmaningar kring nedmontering, bearbetning och transport, ser potentiella aktörer skapande av hållbara affärsmodeller och teknisk kapacitet som positiva möjligheter. Studien bidrar till ökad förståelse och kunskap kring möjligheter och utmaningar med återanvändning av vindturbinblad, vilket är avgörande för att effektivisera processen för nuvarande och framtida aktörer inom branschen. Det är särskilt relevant utifrån de förväntade avfallsmängderna i framtiden och behovet av en effektiv värdekedja. / An increased use of energy, coupled with the expansion of wind power, is expected to lead to increased amounts of waste from end-of-life wind turbine blades and demands for sustainable management across the entire value chain. The complexity of the materials used in wind turbine blades makes recycling difficult, which leads to the majority of blades ending up in landfills with both environmental pollution and resource losses as a result. The study aims to investigate the opportunities and challenges of repurposing wind turbine blades for various application areas by evaluating existing research as well as completed and potential projects, with a focus on environmental, technical and economic aspects. Data was collected through both quantitative and qualitative methods, including literature studies and semi-structured interviews with relevant stakeholders in the wind power and recycling industry. The method also includes a SWOT analysis and a case study that investigates repurposing of wind turbine blades in the municipality of Umeå, including an investigation of the municipality's market needs as well as what opportunities and challenges potential stakeholders see in the repurposing process. The combined results from literature studies, interviews and SWOT analysis shows several technical, economic and environmental opportunities with repurposing of wind turbine blades, including the possibility of potentially reducing both material costs and greenhouse gas emissions compared to the alternatives of incineration or landfilling. Several challenges were identified, including challenges around disassembly, transport, testing the material's strength and lack of information about the material's content. Financial and logistical obstacles regarding the responsibility of manufacturers and operators as well as the lack of cooperation to create an efficient value chain were also found. The result highlights the importance of cooperation between stakeholders, manufacturers and waste handlers as crucial to creating effective solutions and enabling the reuse of wind turbine blades. The case study of Umeå municipality's market needs shows that reuse of wind turbine blades could cover a significant part of the municipality's needs for playgrounds, pedestrian bridges and urban furniture and at the same time contribute to saving carbon dioxide emissions. Despite financial, technical and logistical challenges surrounding dismantling, processing and transport, potential stakeholders see the creation of sustainable business models and technical capabilities as positive opportunities. The study contributes to increased understanding and knowledge about opportunities and challenges with the reuse of wind turbine blades, which is crucial for streamlining the process for current and future stakeholders in the industry. It is particularly relevant based on the expected amounts of waste in the future and the need for an efficient value chain.

Made available in DSpace on 2014-12-17T14:07:12Z (GMT). No. of bitstreams: 1 MaxdavidOC_DISSERT.pdf: 4786704 bytes, checksum: 3c7952fbe7ed29e1b8d03e70a62dab6c (MD5) Previous issue date: 2013-12-30 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The research and development of wind turbine blades are essential to keep pace with worldwide growth in the renewable energy sector. Although currently blades are typically produced using glass fiber reinforced composite materials, the tendency for larger size blades, particularly for offshore applications, has increased the interest on carbon fiber reinforced composites because of the potential for increased stiffness and weight reduction. In this study a model of blade designed for large generators (5 MW) was studied on a small scale. A numerical simulation was performed to determine the aerodynamic loading using a Computational Fluid Dynamics (CFD) software. Two blades were then designed and manufactured using epoxy matrix composites: one reinforced with glass fibers and the other with carbon fibers. For the structural calculations, maximum stress failure criterion was adopted. The blades were manufactured by Vacuum Assisted Resin Transfer Molding (VARTM), typical for this type of component. A weight comparison of the two blades was performed and the weight of the carbon fiber blade was approximately 45% of the weight of the fiberglass reinforced blade. Static bending tests were carried out on the blades for various percentages of the design load and deflections measurements were compared with the values obtained from finite element simulations. A good agreement was observed between the measured and calculated deflections. In summary, the results of this study confirm that the low density combined with high mechanical properties of carbon fibers are particularly attractive for the production of large size wind turbine blades / A pesquisa e desenvolvimento de p?s de aerogeradores s?o fundamentais para acompanhar o crescimento no setor de energias renov?veis em todo mundo. Apesar das p?s atualmente serem produzidas tipicamente com materiais comp?sitos refor?ados com fibras de vidro, a tend?ncia de aumento no tamanho das p?s, especialmente no setor offshore, cresce tamb?m o interesse por materiais comp?sitos refor?ados com fibras de carbono, devido ?s suas propriedades, como elevado m?dulo de elasticidade combinado com baixa densidade. Nesse trabalho um modelo de p? desenvolvido para geradores de grande porte (5 MW) foi estudado em escala reduzida. Foram realizados estudos num?ricos empregando t?cnicas de Computational Fluid Dynamics (CFD) para determinar o carregamento aerodin?mico na p?. Foram projetadas e fabricadas duas p?s com materiais comp?sitos de matriz ep?xi, sendo uma p? com refor?o de fibras de vidro e outra com fibras de carbono. Para os c?lculos estruturais, foi adotado o crit?rio de falha por tens?o m?xima. As p?s foram fabricadas pelo processo de Vacuum Assisted Resin Transfer Molding (VARTM), t?pico para este tipo de componente. Uma compara??o do peso das duas p?s foi realizada, e a p? de fibra de carbono apresentou 45% do peso da p? de fibra de vidro. Ensaios est?ticos de flex?o foram realizados nas p?s para v?rios percentuais do carregamento de projeto e as deflex?es medidas foram comparadas com os valores obtidos nas simula??es num?ricas por elementos finitos. Uma boa concord?ncia foi observada entre os valores de deflex?o medidos e calculados. Em resumo, os resultados obtidos neste trabalho confirmam que a baixa densidade combinada com elevadas propriedades mec?nicas das fibras de carbono s?o atrativas para a produ??o de p?s de aerogeradores de grande porte

Asymmetric bending is explored as a means of inducing bend-twist coupling in an isotropic, fixed-wing airfoil. An analytical model describing the bend-twist coupling behavior of a constant-section airfoil undergoing steady wind loading is derived from Euler-Bernoulli beam theory, and evaluated over a range of structural and material stiffness. Finite element analysis is carried out in the ANSYS Parametric Design Language environment for an asymmetric, two-dimensional beam. Three-dimensional finite element analysis is carried out for two candidate blade models created in Pro/Engineer based on the NACA 64618 airfoil. Deformation results for the two- and three-dimensional finite element models are compared with analytical solutions. Results of this investigation highlight the dependency between the cross-sectional properties of a spar support and its tendency to exhibit twist-coupling under transverse loading.

Renewable energy production with wind turbines has been rising in the last 30 years and it is a crucial technology, which is necessary for the energy transition. As sustainable as the energy production of wind turbines is, the waste management of the blade material is not. Most of the blades end up on a landfill or get incinerated. There are different types of recycling methods, but the most commonly used is to shred the fibers into little pieces and reusing them for filler material in the concrete industry. This approach does not actually split up the blade material into its components but it is more of a downcycling. In this thesis, a new type of pyrolysis will be looked into, which splits up the blade material into its components namely glass fibers and plastic using molten salt. This process would make the glass fiber industry more sustainable by introducing a recycled glass fiber with minimal loss in quality. In a first step, the blade material will be examined more closely with a thermogravimetric analysis to find out what kind of plastic it is and what temperature would be necessary to pyrolyze it. This information will be used to conduct an experiment in a molten salt solution and determine the necessary reaction time and temperature. This data will be used to compare the costs of this method with shredding the material and the conventional pyrolysis. From the thermogravimetric analysis, it was possible to determine that the type of plastic used in this turbine was made out of epoxy. The maximum degredation of this material occurred at 380 ◦C. Not many experiments could be conducted in order to find the optimal conditions for the pyrolysis process due to difficulties with the furnace. Nevertheless, one sample was successfully pyrolyzed at a temperature of 400 ◦C with a residence time of 15 minutes. With the current market conditions in the recycled glass fibers industry, this product would be too expensive and the demand would be too little. However, the market is expected to grow in the next couple years due to rising interests in circular economy and governments introducing regulations. Nevertheless, it is necessary to increase the efficiency of the molten salt pyrolysis in order to be applicable to a bigger scale. More experiments should be conducted with cheaper molten salt in order to sink the costs of the process.

Airplane wings, turbine blades and other structures subjected to air or water flows, can undergo motions depending on their flexibility. As such, the performance of these systems depends strongly on their geometry and material properties. Of particular importance is the contribution of different nonlinear aspects. These aspects can be of two types: aerodynamic and structural. Examples of aerodynamic aspects include but are not lomited to flow separation and wake effects. Examples of structural aspects include but not limited to large deformations (geometric nonlinearities), concentrated masses or elements (inertial nonlinearities) and freeplay. In some systems, and depending on the parameters, the nonlinearities can cause multiple solutions. Determining the effects of nonlinearities of an aeroelastic system on its response is crucial. In this dissertation, different aeroelastic configurations where nonlinear aspects may have significant effects on their performance are considered. These configurations include: the effects of the wake on the flutter speed of a wing placed under different angles of attack, the impacts of the wing rotation as well as the aerodynamic and structural nonlinearities on the flutter speed of a rotating blade, and the effects of the recently proposed nonlinear energy sink on the flutter and ensuing limit cycle oscillations of airfoils and wings. For the modeling and analysis of these systems, we use models with different levels of fidelity as required to achieve the stated goals. We also use nonlinear dynamic analysis tools such as the normal form to determine specific effects of nonlinearities on the type of instability. / Ph. D.

In recent years, machine learning applications have gained great attention in the wind power industry. Among these, artificial neural networks have been utilized to predict the fatigue loads of wind turbine components such as rotor blades. However, the limited number of contributions and differences in the used databases give rise to several questions which this study has aimed to answer. Therefore, in this study, 5-min SCADA data from the Lillgrund wind farm has been used to train two feed-forward neural networks to predict the fatigue loads at the blade root in flapwise and edgewise directions in the shape of damage equivalent loads.The contribution of different features to the model’s performance is evaluated. In the absence of met mast measurements, mesoscale NEWA data are utilized to present the free flow condition. Also, the effect of wake condition on the model’s accuracy is examined. Besides, the generalization ability of the model trained on data points from one or multiple turbines on other turbines within the farm is investigated. The results show that the best accuracy was achieved for a model with 34 features, 5 hidden layers with 100 neurons in each hidden layer for the flapwise direction. For the edgewise direction, the best model has 54 features, 6 hidden layers, and 125 neurons in each hidden layer.For a model trained and tested on the same turbine, mean absolute percentage errors (MAPE) of 0.78% and 9.31% are achieved for the flapwise and edgewise directions, respectively. The seen difference is argued to be a result of not having enough data points throughout the range of edgewise moments. The use of NEWA data has been shown to improve the model’s accuracy by 10% for MAPE values, relatively. Training the model under different wake conditions did not improve the model showing that the wake effects are captured through the input features to some extent. Generalization of the model trained on data points from one turbine resulted in poor results in the flapwise direction. It was shown that using data points from multiple turbines can improve the model’s accuracy to predict loading on other turbines.

The aim of the current dissertation is the development of finite element models capable of predicting the damping and the damped structural dynamic response of laminated composite blades and beams. The present thesis is divided into two main parts, of which the first one studies the material coupling effect on the static and modal characteristics of composite structures. New damping coupling terms are formulated and incorporated into a linear beam finite element to better capture the composite material and structural coupling effects. The second part describes the theoretical framework for predicting the nonlinear damping and damped vibration of laminated composite structures due to large in-plane tensile and compressive forces. A nonlinear beam finite element for composite strips is developed capable of capturing the effects of geometric nonlinearity on the damping of composite laminates. The damping mechanics consider a strain based Kelvin viscoelastic model and Green-Lagrange nonlinear strain expressions, which introduce geometric nonlinearity into the formulation. Incorporation of first-order shear deformation theory into the equations of motion provides the linear and new nonlinear cross-section stiffness and damping terms. Within each element, the stain field is approximated by linear interpolation shape functions. An incremental-iterative methodology is formulated into the finite element solver, based on the Newton-Raphson technique in order to obtain the system solution at each iteration, till the final convergence is achieved. For the sake of completeness, a series of experimental measurements were carried out for the composite strip, subject to tensile and buckling loads. Correlations with theoretical predictions gave credence to the ability of the nonlinear finite element to predict damping of composite structures undergoing large displacements and rotations in the nonlinear regime. The finite element was further extended to include the nonlinear analysis of large-scale hollow composite structures. New first- and second-order stiffness and damping terms were developed and incorporated into an updated nonlinear beam finite element, capable of capturing the effect of rotational stresses on the static and modal characteristics of composite beams and blades. / Σκοπός της παρούσας διδακτορικής διατριβής με τίτλο: "Ανάπτυξη Μη-Γραμμικού Προτύπου Πεπερασμένου Στοιχείου με Απόσβεση για τη Στατική και Δυναμική Ανάλυση Πτερυγίων Ανεμογεννητριών" είναι η ανάπτυξη προτύπων πεπερασμένων στοιχείων με απόσβεση ικανών να προβλέπουν τη στατική και δυναμική απόκριση δοκών και πτερυγίων από σύνθετα υλικά. Η εργασία επικεντρώνεται σε δύο κύριες κατευθύνσεις, που αφορούν τόσο την εισαγωγή νέων όρων στο μητρώο απόσβεσης ενός πεπερασμένου στοιχείου δοκού, όσο και την ανάπτυξη ενός μη-γραμμικού κώδικα πεπερασμένου στοιχείου για τη μελέτη της μη-γραμμικής συμπεριφοράς δοκών και πτερυγίων από σύνθετα υλικά που υπόκεινται σε μεγάλες μετατοπίσεις και περιστροφές. Στο πρώτο μέρος της διατριβής μελετάται η επίδραση της σύζευξης, λόγω της ανισοτροπίας του σύνθετου υλικού, τόσο στη στατική απόκριση όσο και στα μορφικά χαρακτηριστικά κατασκευών από σύνθετα υλικά, διαφόρων διατομών και γεωμετριών. Διατυπώνονται νέοι όροι απόσβεσης που εκφράζουν την εν λόγω σύζευξη και οι οποίοι καθιστούν το γραμμικό πεπερασμένο στοιχείο δοκού πιο πλήρες στην επίλυση προβλημάτων όπου η σύζευξη υλικού επηρεάζει τη συμπεριφορά της κατασκευής. Στο δεύτερο και πλέον σημαντικό μέρος της παρούσας διατριβής αρχικά περιγράφεται το θεωρητικό υπόβαθρο για την πρόβλεψη της μη-γραμμικής δυναμικής απόσβεσης λεπτών δοκών κατασκευασμένα από σύνθετα υλικά οι οποίες υπόκεινται σε μεγάλα συν-επίπεδα εφελκυστικά φορτία ή φορτία λυγισμού. Αναπτύσσεται νέο πεπερασμένο στοιχείο ικανό να περιγράψει την επίδραση της γεωμετρικής μη-γραμμικότητας στην απόσβεση και τη δυσκαμψία της δοκού. Εφαλτήριο για την ανάπτυξη αυτής της μεθοδολογίας ήταν η ανάγκη της πρόβλεψης της δυναμικής απόσβεσης σε κατασκευές από σύνθετα υλικά με πιο πολύπλοκη και εύκαμπτη γεωμετρία, όπως αυτή των πτερυγίων ανεμογεννητριών. Η ανάπτυξη του μη-γραμμικού πεπερασμένου στοιχείου ξεκινά από το επίπεδο της στρώσης του υλικού, όπου διατυπώνονται οι καταστατικές εξισώσεις θεωρώντας το ιξωδοελαστικό πρότυπο του Kelvin για το υλικό της κατασκευής. Στη συνέχεια εισάγονται οι Green-Lagrange εξισώσεις συμβιβαστού οι οποίες εκφράζουν τη γεωμετρική μη-γραμμικότητα καθώς και οι εξισώσεις κίνησης. Σε επίπεδο διατομής, οι κινηματικές υποθέσεις βασίζονται στις παραδοχές της διατμητικής θεωρίας δοκού πρώτης τάξης. Η πρόβλεψη της μη-γραμμικής απόκρισης μιας κατασκευής από σύνθετα υλικά επιτυγχάνεται μέσω της προσομοίωσης της με έναν επαρκή αριθμό πεπερασμένων στοιχείων. Στο εσωτερικό κάθε στοιχείου οι παραμορφώσεις προσεγγίζονται από γραμμικές συναρτήσεις μορφής, οι οποίες οδηγούν στη μητρωική μορφή των μη-γραμμικών εξισώσεων του συστήματος. Λόγω του γεγονότος ότι οι εξισώσεις αυτές εξαρτώνται από τη λύση, δεν μπορούν να λυθούν απευθείας κάτι που καθιστά αναγκαία τη χρήση μιας σταδιακής-επαναληπτικής τεχνικής. Στην παρούσα διατριβή εισάγεται στο λύτη του μη-γραμμικού κώδικα η Newton-Raphson τεχνική. Το επόμενο βήμα αφορά τη σύνθεση των ολικών δομικών μητρών του συστήματος και την εφαρμογή των συνοριακών συνθηκών. Σε κάθε επανάληψη λαμβάνει χώρα η επίλυση των γραμμικοποιημένων εξισώσεων και ο υπολογισμός των πραγματικών και εφαπτομενικών μη-γραμμικών μητρώων δυσκαμψίας και απόσβεσης της κατασκευής, τα οποία τελικώς επιλύονται με τη μέθοδο της αριθμητικής ολοκλήρωσης κατά Gauss. Το πεπερασμένο στοιχείο δοκού εξελίχθηκε περαιτέρω ώστε να συμπεριλάβει τη μη-γραμμική ανάλυση μεγάλων λεπτότοιχων κατασκευών από σύνθετα υλικά, όπως αυτά των πτερυγίων ελικοπτέρων και ανεμογεννητριών. Η εισαγωγή της πλήρους έκφρασης της αξονικής μη-γραμμικής Green-Lagrange παραμόρφωσης στη διατύπωση των κινηματικών υποθέσεων οδηγεί στην πλήρη έκφραση των πραγματικών και εφαπτομενικών δομικών μητρών της κατασκευής. Οι νέοι μη-γραμμικοί όροι δυσκαμψίας και απόσβεσης πρώτης και δεύτερης τάξης μπορούν να περιγράψουν την επίδραση των εσωτερικών εφελκυστικών τάσεων στα μορφικά χαρακτηριστικά δοκών και πτερυγίων. Το μη-γραμμικό πεπερασμένο στοιχείο είναι ικανό να χαρακτηρίσει τη στατική συμπεριφορά και την αποσβενυμένη ταλάντωση δοκών από σύνθετα υλικά. Η επαλήθευση του μη-γραμμικού κώδικα πραγματοποιήθηκε μέσω μιας σειράς πειραματικών μετρήσεων που αφορούσαν τη μέτρηση της φυσικής συχνότητας και της μορφικής απόσβεσης σε λεπτές δοκούς από σύνθετα υλικά τόσο σε εφελκυσμό όσο και σε συνθήκες λυγισμού. Τα πειραματικά αποτελέσματα έρχονται σε πολύ καλή συμφωνία με τις θεωρητικές προβλέψεις του κώδικα κάτι που εξασφαλίζει την αξιοπιστία του μη-γραμμικού πεπερασμένου στοιχείου.