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� Widely available � Demanding manufacturing processes Composite blades � Lightweight � Strong � High repeatability � Good fatigue characteristics � Low material availability � Possibility for complex airfoil shape Wooden blades � Lightweight � Abundant supply � Cheap � Strong � Flexible � Non-uniform when hand-carved � Simple airfoil shape required Quantitative engineering characteristics of the materials are listed in table 6.2. The data is based on [10, p. 221] and it should only be used for the purpose of this comparison, as many assumptions and simplifications are made to represent each property by a <strong>sin</strong>gle ROTOR value. The values will vary depending on factors such as manufacturing processes, material purity, reinforcement material and environmental conditions. Parameter Material Aluminium (AlMg5) Density � g/cm 3 Modulus of elas. E GPa Ultimate strength � MPa Spec. breaking strength �/� MPa/(g/cm 3 ) Spec. modulus of elasticity E/� GPa/(g/cm 3 ) Fatigue strength (10 7 ) 2.7 70 236 87 26 20 Steel (St. 52) 7.85 210 520 66 27 60 CFRP a 1.4 44 550 393 31 100 GFRP a 1.7 15 420 247 9 35 Wood b 0.38 8 65 171 21 20 a) Epoxy matrix with 40 vol.% b) Properties for Sitka Spruce (Picea sitchensis) Table 6.2: Strength and stiffness parameters of materials available for rotor blades ��A MPa 45
ROTOR Table 6.3 provides a material cost comparison based on approximate prices per tonne, given in [58]. The prices are derived relatively to the price of steel in 2005, set to $100/tonne. The actual values are out of date and they are unlikely to represent the prices in development countries. However the prices are considered valid for a relative comparison of the price differences. 46 Material Steel Aluminium CFRP GFRP Wood Relative material cost ($/tonne) Relative volume cost ($/m 3 ) Table 6.3: Material cost comparison 100 400 20000 1000 200 785 1080 28000 1700 76 In addition to material cost, it is necessary to take into account manufacturing costs. As a general rule it can be stated that manufacturing processes which require little or no auto- matic machining are most advantageous. For the present project the price of manufacturing is not scrutinised further, as the majority of it will be carried out by volunteers. When taking into consideration the available data, the material selection is neither straightforward nor unambiguous and the right choice of blade material will, to a great extent, depend on the conditions at the specific destination where the wind turbine is to be built. For the current wind turbine design wood is chosen as blade material, primarily due to its generally high availability in developing countries, its low price and its low require- ments for production facilities. The choice in material is further sustained by the fact that wood in its nature is designed for resisting wind loads in bending, which is confirmed by the overall excellent material properties in terms of strength and stiffness. Other material options may prove superior in certain cases, e.g. where high quality wood is expensive or difficult to find. The blade attachment method described in section 6.2.4 enables blades of other materials to be attached in future designs without impacting the overall design con- cept. An in-depth description of the engineering properties of the chosen blade material may be found in appendix E. 6.2.2 Airfoil and geometry The cross-section of the wooden blades has the shape of an airfoil, which optimises the aerodynamic performance. A number of terms are used to characterise airfoils, as shown on figure 6.5. The geometric parameters have great influence on the aerodynamic performance of the airfoil. Not shown on figure 6.5 is the span of the airfoil, which is perpen- dicular to the shown cross-section.
Page 1 and 2: WIND TURBINE DESIGN
Page 3 and 4: ABSTRACT At the request of the Engi
Page 5 and 6: CONTENTS 1 Introduction ...........
Page 7 and 8: E Structural analysis of blades ...
Page 9 and 10: INTRODUCTION members. Today EWB-DK
Page 11 and 12: INTRODUCTION Figure 1.2: Left pictu
Page 13 and 14: INTRODUCTION 6
Page 15 and 16: PROBLEM STATEMENT reconfigured with
Page 17 and 18: PROBLEM STATEMENT 10
Page 19 and 20: METHODOLOGY Figure 3.1: Flow chart
Page 21 and 22: METHODOLOGY 14 3.1 Calculation meth
Page 23 and 24: CONCEPTUALISATION the kinetic wind
Page 25 and 26: CONCEPTUALISATION Figure 4.3: (a) D
Page 27 and 28: CONCEPTUALISATION issues due to tur
Page 29 and 30: CONCEPTUALISATION 22 Figure 4.8: Ty
Page 31 and 32: CONCEPTUALISATION � Darrieus 24 F
Page 33 and 34: CONCEPTUALISATION 26 Figure 4.13: G
Page 35 and 36: CONCEPTUALISATION Figure 4.14: Powe
Page 37 and 38: CONCEPTUALISATION 30 ID Requirement
Page 39 and 40: CONCEPTUALISATION most suitable sol
Page 41 and 42: CONCEPTUALISATION The embodiment de
Page 43 and 44: DESIGN PRESENTATION The main dimens
Page 45 and 46: DESIGN PRESENTATION The design prop
Page 47 and 48: DESIGN PRESENTATION The background
Page 49 and 50: ROTOR 42 6.1 Number of blades Moder
Page 51: ROTOR 44 Figure 6.4: Blade design s
Page 55 and 56: ROTOR Figure 6.7 displays the lift
Page 57 and 58: ROTOR Figure 6.9: Rotor power outpu
Page 59 and 60: ROTOR 6.2.3 Manufacturing During th
Page 61 and 62: ROTOR 54 The three sides of the tem
Page 63 and 64: ROTOR When the carving process is f
Page 65 and 66: ROTOR 58 Figure 6.17: Blade attachm
Page 67 and 68: ROTOR 60 Figure 6.19: Rotor power o
Page 69 and 70: ROTOR 62 Figure 6.22: Efficiency
Page 71 and 72: ROTOR sidering the output from the
Page 73 and 74: ROTOR 66
Page 75 and 76: GENERATOR AND ELECTRICAL SYSTEM 68
Page 77 and 78: GENERATOR AND ELECTRICAL SYSTEM The
Page 79 and 80: GENERATOR AND ELECTRICAL SYSTEM Fig
Page 81 and 82: GENERATOR AND ELECTRICAL SYSTEM 74
Page 83 and 84: YAW AND FURLING For an upwind wind
Page 85 and 86: YAW AND FURLING (16), which are bol
Page 87 and 88: YAW AND FURLING 80 8.2 Furling syst
Page 89 and 90: YAW AND FURLING 82 8.3 Summary The
Page 91 and 92: TOWER Concrete tower 84 Figure 9.1:
Page 93 and 94: TOWER 86 Figure 9.4: Turbulent air
Page 95 and 96: TOWER Figure 9.7 shows the tower ba
Page 97 and 98: TOWER models [41, p. 111]. Under ce
Page 99 and 100: ALTERNATIVE BLADE DESIGN 92 10.1 Ai
Page 101 and 102: ALTERNATIVE BLADE DESIGN 94 10.3 Su
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DESIGN EVALUATION 96 6 W Low-cost m
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DESIGN EVALUATION Weaknesses 1) The
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FURTHER DEVELOPMENT � Foundation
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FURTHER DEVELOPMENT 102
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CONCLUSION proposal is highly flexi
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NOMENCLATURE Abbreviation Descripti
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NOMENCLATURE Lgs Distance between u
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NOMENCLATURE 110
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BIBLIOGRAPHY [14] Magenn Power Inc.
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BIBLIOGRAPHY [53] H. J. Larsen, H.
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LIST OF ATTACHMENTSBASIS FOR CALCUL
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LIST OF ATTACHMENTSROTOR THEORY Thi
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LIST OF ATTACHMENTSROTOR THEORY 134
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LIST OF ATTACHMENTSROTOR THEORY Cho
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LIST OF ATTACHMENTSROTOR THEORY 138
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LIST OF ATTACHMENTSROTOR DESIGN TOO
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LIST OF ATTACHMENTSROTOR DESIGN TOO
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LIST OF ATTACHMENTSAIRFOIL With the
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LIST OF ATTACHMENTSAIRFOIL Complete
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LIST OF ATTACHMENTSSTRUCTURAL ANALY
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LIST OF ATTACHMENTSBLADE ATTACHMENT
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LIST OF ATTACHMENTSSTRUCTURAL VERIF
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LIST OF ATTACHMENTSTOWER ANALYSIS T
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LIST OF ATTACHMENTSFURLING AND YAW
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LIST OF ATTACHMENTSALTERNATIVE AIRF
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LIST OF ATTACHMENTSCOMPLIANCE WITH
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