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CONCEPTUALISATION From table 4.2 and figure 4.16 it is evident that the HAWT and the Savonius wind turbine are the front-runner candidates when taking into consideration the relative evaluation criteria. With a rating of 26 points the Savonius wind turbine is the quantitatively most suitable concept, but it must be emphasised that the applied evaluation methods are mere tools and not automatic decision mechanisms without uncertainties. In the next section the two best candidates are therefore subjected to a technical assessment that explores further aspects of the concepts than those used in the evaluation. 4.4 Technical assessment The HAWT design is already widely used in developing countries and is a proven, reliable and efficient concept for electrical production in the 1500 W size. The Savonius rotor on the other hand has a less effective, but very simple and reliable design that can be built from very basic components such as oil barrels. It is also commonly used in rural areas, although usually in the power range of 200-500 W, which is less than needed for the present project. If it is possible to scale the Savonius concept to the needed size it may prove to be the most suitable candidate due to its simplicity. Assuming a power coefficient Cp of 0.15 and an overall efficiency �tot of 45% for mechanical components, generator and any possible transmission, it is possible to calculate the required swept rotor area of a Savonius rotor required to produce 1500 W power output at wind speed V of 12 m/s (cf. table 2.1). The density � used in (4.1) is 1.225 kg/m 3 in accordance with appendix A.2. In comparison a lift-based HAWT with a Cp of 0.35 requires a swept area of only 9 m 2 (57% less than the Savonius) under the same conditions. This is equivalent to a blade length of approximately 1.7 m. P Asav 1 Cp 2 � V3 21 m �tot 2 � � A 200-litre oil barrel sliced in half and welded in an S-shape has a swept area (cross- sectional area) of 0.9 m 2 , which means that at least 23 oil barrels are needed to provide the necessary swept rotor area. A similar sized structure is reached when u<strong>sin</strong>g e.g. bend sheet metal instead of oil barrels. This makes the Savonius wind turbine very impractical and difficult to handle. Moreover it may actually produce less energy annually compared to a HAWT, as it is placed by the ground where the wind speeds are lower due to surface drag. Although the Savonius wind turbine satisfies both the demands of the requirement specifi- cation and the evaluation criteria to a great extend, it must be considered unsuitable for the present purpose. This is primarily due to the required size of the structure and its po- tentially low annual energy production. The HAWT concept is therefore adopted as the (4.1) 31
CONCEPTUALISATION most suitable solution for the present purpose. The lift-based version is chosen due its superior performance and its applicability for production of electricity. 32 4.5 Principal solution The principal solution is a horizontal-axis wind turbine containing the subsystems shown on figure 4.17. R o t o r Hub Figure 4.17: Major components of the principal solution The following paragraphs contain a brief description of each subsystem. It also identifies the associated focal points, limitations and exclusions of the development phases that follow the present conceptual phase. These are in accordance with the prioritisations of EWB and the available project resources. Control Drive train Generator Yaw system T o w e r Foundation Nacelle Electrical system
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: CONCEPTUALISATION 30 ID Requirement
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 and 52: ROTOR 44 Figure 6.4: Blade design s
Page 53 and 54: ROTOR Table 6.3 provides a material
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
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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
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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
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YAW AND FURLING 82 8.3 Summary The
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TOWER Concrete tower 84 Figure 9.1:
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TOWER 86 Figure 9.4: Turbulent air
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TOWER Figure 9.7 shows the tower ba
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TOWER models [41, p. 111]. Under ce
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ALTERNATIVE BLADE DESIGN 92 10.1 Ai
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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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