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    ENG1050Design of Materials ReportName: Chong Jie Mee Student ID: 24731706Demonstrator: Mr. Vahdat Vahedi Lab session: Thursday 11am-1pm

    Abstract

    The objective report is to design a suitable material and geometry for wind turbine tower and blades. A

    limits of constraints are set for the design of material. The tower and blades must be resistant to UV,

    function temperature must be between -40oC to 40oC in a marine environment. In order to find the

    optimum shape and dimensions, an excel spreadsheet is established to aid in this process. A few possible

    dimensions is inputted to compare the effects on design stress, elastic modulus and cross-section area. The

    material index based on stiffness-limited applications and strength-limited applications are worked out by

    deriving equation 1, equation 2 and equation 3 stated under Task 1. Top 3 materials are chosen

    respectively for tower and blades using CES EduPack. Eco-Audit process is carry out to determine the

    energy use for each material from manufacture to end of life. The optimum shape and dimensions

    obtained is hollow circle section with outer diameter 4.5m and inner diameter 3.5m. The top 3 materials

    for tower are silicon carbide, alumina and silicon nitride. While the top 3 materials for blades are cast Al-

    alloys, age-hardening wrought Al-alloys and non-age-hardening wrought Al-alloys. After analyzing the

    suitability of top 3 materials for both tower and blades, silicon carbide and cast Al-alloys are chosen as thebest materials for both tower and blades respectively. The minimum weight of the tower calculated by

    multiplying the density of material, cross section area selected for best geometry and height of tower is 1,

    558, 184kg and the construction cost calculated by multiplying the weight and price is RM71, 209, 008.80.

    Introduction

    In the past few years, people are becoming more concern about environmental issues such as

    increase in greenhouse gases, air pollution and global warming. The major contributor to these issues is

    the usage of fossil fuels. To solve this problem, renewable energy resources such as wind energy are being

    explored to replace fossil fuels. Therefore, the importance of offshore wind farms as a source of renewable

    energy has drastically increased.

    The growing importance of wind energy drives the wind industry to develop larger, lighter, and

    cheaper wind turbine towers and blades. The design is always a matter of constant tradeoff between

    demands of lower cost, better energy productivity, increased lifetime, reliability and durability. In order to

    acquire an optimum design of wind turbine, we have to take into considerations of the shape and

    parameters of turbine tower, the durability of material and also the cost of material. The process of

    manufacturing and building the wind turbine and its effect to environment is also taken into consideration.

    CES EduPack is used to choose the best material for tower and blades according to certain

    requirement and constraints. The function, constraints, objectives and free variables are determined beforechoosing the optimum material and shape.

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    ENG1050Design of Materials ReportName: Chong Jie Mee Student ID: 24731706Demonstrator: Mr. Vahdat Vahedi Lab session: Thursday 11am-1pm

    DESIGN FACTORS OFFSHORE WIND TURBINE TOWER

    FUNCTION To support the turbine generatorCONSTRAINTS Function temperature :-40oC to 40oC in a marine environment

    Resistant to UV Resistant to corrosion Must not fracture in brittle manner Must not buckle Deflection at top < 5cm Fixed tower height : 80m Longest Edge of Cross Section Area < 5m

    FREE VARIABLES The material used Diameter of turbine tower (within 5m) Geometry of tower Cross-section area of tower

    OBJECTIVE To design a low density, cost and strong turbine towerTable 1: Design factors of offshore wind turbine tower

    DESIGN FACTORS OFFSHORE WIND TURBINE BLADE

    FUNCTION To carry their own weight To take loads exerted on them by the wind

    CONSTRAINTS Function temperature :-40oC to 40oC in a marine environment Must be stiff, strong and light Resistant to UV Resistant to corrosion Minimum fracture toughness : 15MPa1/2 Fatigue strength criterion of 100MPa at 107cycles Fixed width and length of blades

    FREE VARIABLES The material usedOBJECTIVE To design a low density, cost and stiff turbine blade

    Table 2: Design factors of offshore wind turbine blade

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    ENG1050Design of Materials ReportName: Chong Jie Mee Student ID: 24731706Demonstrator: Mr. Vahdat Vahedi Lab session: Thursday 11am-1pm

    Task 1

    The wind turbine tower has the function of supporting the turbine generator. It will also be

    exposed to UV and corrosive nature of marine environment. Therefore it is important to choose a suitable

    geometry and material that can overcome these problems.

    4 types of uniform cross section of pillars (Figure 1) are taken into consideration in choosing the

    most efficient geometry. The most efficient geometry should have the minimum E, y and cross sectional

    area A to reduce cost and weight. The 4 types of uniform cross section are solid circle section, hollow

    circle section, solid square section and hollow square section. Different possible dimensions are used to

    compare the effect on cross sectional area A, minimum required modulus E and minimum design stress .

    The optimized shape and dimensions with the highest geometry performance index is chosen.

    The minimum required modulus E and minimum design stress are obtained by rearranging

    equation 1 and 2. The failure load F which is the wind load and height of tower L is fixed. The equation

    for I and ymis as stated in Figure 1 and the max deflection is fixed at 0.05m.

    y =

    E =

    Geometry performance index=

    Failure load F 1x106N

    Height of tower L 80m

    Figure 1: Four different cross-section shapes for Tower design selection

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    ENG1050Design of Materials ReportName: Chong Jie Mee Student ID: 24731706Demonstrator: Mr. Vahdat Vahedi Lab session: Thursday 11am-1pm

    An Excel spreadsheet is established to aid in choosing the most efficient geometry. The change in

    cross sectional area A, minimum required modulus E and minimum design stress is observed by

    inputting different possible dimensions (T, D, d, t). Safety factor of 2 is used to find design stress.

    Types of

    GeometryIndex

    Failure

    Load

    Tower

    heightDeflection

    D/T

    (m)

    d/t

    (m)

    Ym

    (m)

    Cross-sectional

    Area (m^2)

    Solid

    Circle

    Section

    1 1.00E+06 80 0.05 5 0 2.5 19.63495408

    2 1.00E+06 80 0.05 4.5 0 2.25 15.90431281

    3 1.00E+06 80 0.05 4 0 2 12.56637061

    Hollow

    Circle

    Section

    4 1.00E+06 80 0.05 5 4 2.5 7.068583471

    5 1.00E+06 80 0.05 4.5 3.5 2.25 6.283185307

    6 1.00E+06 80 0.05 4 3 2 5.497787144

    Solid

    Square

    Section

    7 1.00E+06 80 0.05 5 0 2.5 19.63495408

    8 1.00E+06 80 0.05 4.5 0 2.25 15.90431281

    9 1.00E+06 80 0.05 4 0 2 12.56637061

    Hollow 10 1.00E+06 80 0.05 5 4 2.5 7.068583471

    Square

    Section

    11 1.00E+06 80 0.05 4.5 3.5 2.25 6.283185307

    12 1.00E+06 80 0.05 4 3 2 5.497787144

    Types of

    GeometryIndex

    Second

    Moment

    of Area, I

    Design stress,

    (MPa)

    Elastic

    modulus,

    E(GPa)

    Geometry

    Performance

    Index

    Solid

    Circle

    Section

    1 30.67961576 1.30E+01 111.2573691 7.39E+01

    2 20.1288959 1.79E+01 169.5737983 1.91E+02

    3 12.56637061 2.55E+01 271.6244362 5.50E+02

    Hollow

    Circle

    Section

    4 18.11324514 2.21E+01 188.4440533 5.89E+02

    5 12.76272016 2.82E+01 267.4455987 1.20E+03

    6 8.590292412 3.73E+01 397.3477467 2.69E+03

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    ENG1050Design of Materials ReportName: Chong Jie Mee Student ID: 24731706Demonstrator: Mr. Vahdat Vahedi Lab session: Thursday 11am-1pm

    Solid

    Square

    Section

    7 52.08333333 7.68E+00 65.536 2.56E+01

    8 34.171875 1.05E+01 99.88721232 6.62E+01

    9 21.33333333 1.50E+01 160 1.91E+02

    Hollow

    Square

    Section

    10 30.75 1.30E+01 111.00271 2.04E+02

    11 21.66666667 1.66E+01 157.5384615 4.17E+02

    12 14.58333333 2.19E+01 234.0571429 9.34E+02

    Maximum= 2.69E+03

    Table 3: Possible geometry and dimension and effect on area, elastic modulus and design stress

    From the excel sheet above, the 6th

    geometry has the highest geometry performance index whichis 2.24E+04. However, it has a relatively highly high Youngs modulus which is 397GPa which only a

    few materials can achieve that value. Thus the 5thgeometry with the second highest geometry

    performance index is chosen. Therefore the optimized shape and dimensions obtained is hollow circle

    section with outer diameter 4.5m and inner diameter 3.5m.

    In strength-limited applications, deflection is allowable as long as the component does not fail and

    strength is the active design constraint. While in stiffness-limited applications, elastic deflection is the

    active design constraint. To work out the material performance index (MI), the equation below is

    necessary.

    F = ----- (Equation 1)

    = ----- (Equation 2)

    m = *A*L----- (Equation 3)

    Where F = Failure Load,

    I = Second Moment of Area, y = yield strength,

    ym= Distance between neutral axis of the beam and its outer most surface

    L = Height of tower, m = Mass of Material

    = Density of Material, A = Cross-section Area

    = Deflection, E = Elastic Modulus

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    ENG1050Design of Materials ReportName: Chong Jie Mee Student ID: 24731706Demonstrator: Mr. Vahdat Vahedi Lab session: Thursday 11am-1pm

    In order to work out the material performance index (MI) based on strength-limited application,

    Equation 1 and Equation 3 is needed. The uniform cross-section area is assumed to be a solid square.

    Safety factor S is applied. = S*y where is the design stress.

    Workings to find material index:

    Sub I =and ym =

    into the equation (1)

    F =

    F = ----- (1)

    Sub A = T2 into the equation (3)

    M = * T2*L

    T = ----- (2)

    Sub (2) into (1)

    F =

    6FL

    =

    MI =

    Design guidelines:

    Log (MI) = Log

    Log (MI) = LogLog

    Log= Log+ Log (MI)Compared to y = mx + c

    Slope, m =

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    ENG1050Design of Materials ReportName: Chong Jie Mee Student ID: 24731706Demonstrator: Mr. Vahdat Vahedi Lab session: Thursday 11am-1pm

    By using CES EduPack, the top 5 materials with the highest performance index is chosen with

    certain constraints. The constraints considered include functional temperature of -40oC to 40

    oC, high

    durability towards salt water and excellent durability towards marine environment and UV radiation.

    Minimum elastic modulus and design stress obtained in task 1 from the best geometry is also set as limits.

    Yield strength is plotted against density*price as cost and weight of material is considered. The material

    with highest performance index is silicon carbide, followed by alumina, silicon nitride, boron carbide and

    tungsten carbides.

    Figure 2: CES EduPack material selection results

    Among the 5 selected materials, silicon carbide is the best option. This is because silicon carbide

    has lower density*price value and yet has a similar yield strength to the other four materials.

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    ENG1050Design of Materials ReportName: Chong Jie Mee Student ID: 24731706Demonstrator: Mr. Vahdat Vahedi Lab session: Thursday 11am-1pm

    Task 2

    The most important material criteria of turbine blades is to be stiff, strong and light. This is

    because turbine blades have to carry their own weight on the same time take loads exerted on them by the

    wind. It is also better if the material requires less maintenance as maintenance process of turbines is hard.

    Thus, a more expensive material with longer lifespan can be chosen if it cuts down on maintenance.

    In order to work out the material performance index (MI) based on stiffness-limited application,

    Equation 2 and Equation 3 is needed.

    Workings to find material index:

    Sub I =into the equation (2)

    =

    = ----- (1)

    Sub A = T2 into the equation (3)

    M = * T2*L

    T2=----- (2)

    Sub (2) into (1)

    =

    ( )

    =

    =

    MI =

    Design guidelines:

    Log (MI) = Log

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    ENG1050Design of Materials ReportName: Chong Jie Mee Student ID: 24731706Demonstrator: Mr. Vahdat Vahedi Lab session: Thursday 11am-1pm

    Log (MI) = Log2LogLog= Log+ Log (MI)

    Compared to y = mx + c

    Slope, m = 2

    By using CES EduPack, the top 5 materials with the highest performance index is chosen with

    certain constraints. The constraints considered include functional temperature of -40oC to 40

    oC and

    excellent durability towards marine environment and UV radiation. Elastic modulus is plotted against

    density times price as cost and weight of material is considered. The material with highest performance

    index is cast Al-alloys, followed by age-hardening wrought Al-alloys, non-age-hardening wrought Al-

    alloys, aluminum/silicon carbide composite and brass.

    Figure 3: CES EduPack material selection results

    After the top 5 materials is chosen, the next design consideration is against fatigue. The blades

    should be able to go throught an estimated 1 billion loading cycles through their lifetime. A minimum

    fracture toughness of 15MPam1/2and a fatigue strength criterion of 100MPa at 107 is applied. The top 3

    materials chosen with fracture toughness and fatigue strength limits are cast Al-alloys, age-hardening

    wrought Al-alloys and non-age-hardening wrought Al-alloys.

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    ENG1050Design of Materials ReportName: Chong Jie Mee Student ID: 24731706Demonstrator: Mr. Vahdat Vahedi Lab session: Thursday 11am-1pm

    Figure 4: CES EduPack material selection results

    Among the three materials, the best option is cast Al-alloys. This is because the top threematerials have almost the same density*price but yet cast Al-alloys have the highest Youngs modulus.

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    ENG1050Design of Materials ReportName: Chong Jie Mee Student ID: 24731706Demonstrator: Mr. Vahdat Vahedi Lab session: Thursday 11am-1pm

    Corrosion Protection for both Tower and Blade

    The offshore wind turbine is exposed to marine and corrosive environment. It is possible that the

    wind turbine will corrode and affect its performance. Thus the type of corrosion, the cause of the corrosion

    and its protection measurement must be identified to protect the wind turbine.

    Design

    Object

    Possible Corrosion

    Type

    Responsible Environmental

    Condition

    Corrosion Protection

    Measurement

    Tower

    Uniform corrosion

    Presence of sea water uniformly

    distributed around the lower

    part of tower

    Apply coating on material

    surface

    Crevice corrosionPresence of crevice in tower

    that stores stagnant water

    Use cathodic protection Use higher resistant

    material

    Microbiologically

    Influenced Corrosion

    (MIC)

    Interaction between

    construction materials and

    microbial activity

    Regular mechanicalcleaning

    Chemical treatmentwith biocides to control

    population of bacteria

    Erosion corrosion High flow rate of wave Use cathodic protection

    Blade

    Fretting corrosion

    Constant rubbing contact

    between two moving metal

    surfaces

    Apply lubricationbetween contact

    surfaces

    Erosion corrosion High wind speedUse cathodic protection to

    minimize erosion corrosion

    Galvanic corrosion Presence of moisture in air Apply coating on materialsurfaces

    Corrosion fatigue

    Development of crack under

    simultaneous action of

    corrosion and cyclic stress due

    to wind load

    Use coating or inhibitors to

    delay the initiation of corrosion

    cracks

    Table 3: Possible type corrosion and protection measurement

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    Task 3 Eco-Audits of Tower and Blade

    Table 4: Energy use and CO2 footprint for silicon carbide tower

    Phase Energy (J) Energy (%) CO2 (kg) CO2 (%)

    Material 5.9e+12 99.7 5.25e+05 99.8

    Manufacture 0 0.0 0 0.0

    Transport 4.05e+07 0.0 2.87 0.0

    Use 0 0.0 0 0.0

    Disposal 1.6e+10 0.3 1.12e+03 0.2

    Total (for first life) 5.92e+12 100 5.26e+05 100

    End of life potential -5.66e+12 -5.08e+05

    Table 5: Energy use and CO2 footprint for alumina tower

    Phase Energy (J) Energy (%) CO2 (kg) CO2 (%)

    Material 4.16e+12 99.6 2.25e+05 99.5

    Manufacture 0 0.0 0 0.0

    Transport 4.05e+07 0.0 2.87 0.0

    Use 0 0.0 0 0.0

    Disposal 1.6e+10 0.4 1.12e+03 0.5

    Total (for first life) 4.18e+12 100 2.26e+05 100

    End of life potential -3.92e+12 -2.08e+05

    Table 6: Energy use and CO2 footprint for silicon nitride tower

    Phase Energy (J) Energy (%) CO2 (kg) CO2 (%)

    Material 9.75e+12 99.8 3.9e+05 99.7

    Manufacture 0 0.0 0 0.0

    Transport 4.05e+07 0.0 2.87 0.0

    http://c/Users/jmcho8/Downloads/silicon%20nitride.doc%23MaterialPhasehttp://c/Users/jmcho8/Downloads/silicon%20nitride.doc%23MaterialPhasehttp://c/Users/jmcho8/Downloads/silicon%20nitride.doc%23MaterialPhase
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    Use 0 0.0 0 0.0

    Disposal 1.6e+10 0.2 1.12e+03 0.3

    Total (for first life) 9.76e+12 100 3.91e+05 100

    End of life potential -9.51e+12 -3.73e+05

    Table 7: Comparison of energy use for top 3 tower materials

    Top 3 tower materialsTotal energy use (For material, manufacturing,

    transportation and use phases)

    Silicon carbide 5.90E+12

    Alumina 4.16E+12

    Silicon nitride 9.74E+12

    Figure 5: Energy use comparison of top 3 tower materials

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    ENG1050Design of Materials ReportName: Chong Jie Mee Student ID: 24731706Demonstrator: Mr. Vahdat Vahedi Lab session: Thursday 11am-1pm

    Table 8: Energy use and CO2 footprint for cast Al-alloys blades

    Phase Energy (J) Energy (%) CO2 (kg) CO2 (%)

    Material 7.03e+12 94.5 4.23e+05 93.2

    Manufacture 4.05e+11 5.5 3.04e+04 6.7

    Transport 1.77e+07 0.0 1.26 0.0

    Use 0 0.0 0 0.0

    Disposal 7e+09 0.1 490 0.1

    Total (for first life) 7.44e+12 100 4.54e+05 100

    End of life potential -6.92e+12 -4.16e+05

    Table 9: Energy use and CO2 footprint for age-hardening wrought Al-alloys blades

    Phase Energy (J) Energy (%) CO2 (kg) CO2 (%)

    Material 7.29e+12 95.0 4.48e+05 94.0

    Manufacture 3.76e+11 4.9 2.81e+04 5.9

    Transport 1.77e+07 0.0 1.26 0.0

    Use 0 0.0 0 0.0

    Disposal 7e+09 0.1 490 0.1

    Total (for first life) 7.67e+12 100 4.76e+05 100

    End of life potential -7.18e+12 -4.4e+05

    Table 10: Energy use and CO2 footprint for non-age-hardening wrought Al-alloys blades

    Phase Energy (J) Energy (%) CO2 (kg) CO2 (%)

    Material 7.36e+12 95.5 4.6e+05 94.6

    Manufacture 3.4e+11 4.4 2.55e+04 5.3

    Transport 1.77e+07 0.0 1.26 0.0

    Use 0 0.0 0 0.0

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    Disposal 7e+09 0.1 490 0.1

    Total (for first life) 7.71e+12 100 4.86e+05 100

    End of life potential -7.25e+12 -4.52e+05

    Table 11: Comparison of energy use for top 3 blades materials

    Top 3 blades materialsTotal energy use (For material, manufacturing,

    transportation and use phases)

    Cast Al-alloys 7.43E+12

    Age-hardening wrought Al-alloys 7.66E+12

    Non-age-hardening wrought Al-alloys 7.70E+12

    Figure 6: Energy use comparison of top 3 blades materials

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    ENG1050Design of Materials ReportName: Chong Jie Mee Student ID: 24731706Demonstrator: Mr. Vahdat Vahedi Lab session: Thursday 11am-1pm

    Materials for

    blades

    100% virgin material

    energy use (J)

    100% recycled material

    energy use (J)Energy difference (J)

    Cast Al-alloys 7.03e+12 8.79e+11 6.15E+12

    Age-hardening

    wrought Al-alloys7.29e+12 1.23e+12 6.06E+12

    Non-age-hardening wrought

    Al-alloys

    7.36e+12 1.24e+12 6.12E+12

    Table 12: Material energy comparison between 100% virgin material and 100% recycled material for

    blades

    As the materials for tower are all technical ceramics which cannot be recycled, there is no

    comparison between 100% virgin and 100% recycled material. From the table above, it is obvious that

    production of 100% recycled materials use less energy than production of 100% virgin materials for

    turbine blades.

    Deficiency in Eco-Audit Process

    1. Legal requirements are not stated in the process2. Environmental related cost is excluded in the Eco-Audit process3. Choices such as transport type are limited for the Eco-Audit functions4. Database combination in a single analysis is not available

    Conclusion

    The best material to construct wind turbine tower will be silicon carbide. Although the totalenergy use from production to use of silicon carbide is more than alumina, its price is less than alumina

    and silicon nitride while its density is less than alumina. Moreover, it has a relatively high yield strength.

    Its yield strength and elastic modulus is higher than the minimum design stress and elastic modulus

    obtained from the optimum geometry. Therefore silicon carbide is more suitable than alumina and silicon

    nitride as material for turbine tower. Other than that, the best material for wind turbine blades will be cast

    Al-alloys. This is because the total energy use from production to use of cast Al-alloys is less than age-

    hardening wrought Al-alloys and non-age-hardening wrought Al-alloys. It has a similar price and density

    as the other two materials while having the highest elastic modulus among them. Thus, cast Al-alloys is

    the best choice among the three materials. Both of the selected tower and turbine materials are functional

    in temperature of -40oC to 40

    oC, high durability towards effect of marine environment and UV radiation.

    The tower material selected has excellent durability towards salt water.

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    References

    W.D. Callister, Materials Science and Engineering, an Introduction, 7th edition: Chapter 23. MaterialsSelection and Design Considerations; Chapter 24. Economic, Environmental, and Societal Issues in

    Materials Science and Engineering

    CES Edupack 2012

    Webcorr 2013,Different Types of Corrosion - Mechanisms, Recognition & Prevention.Retrieved October

    17, 2013, from http://www.corrosionclinic.com/different_types_of_corrosion.htm

    Materials Information Technology Challenges with Wind Turbine Technology,

    http://grantadesign.com/news/news/reports/wind.shtml.

    M.F. Ashby, Materials Selection in Mechanical Design, Vols I and II, Pergamon, Oxford, 1992.

    F. Karpat 2013, A Virtual Tool for Minimum Cost Design of a Wind Turbine Tower with RingStiffeners,Energies, vol. 6, pp. 3822-3840.

    http://www.corrosionclinic.com/different_types_of_corrosion.htmhttp://grantadesign.com/news/news/reports/wind.shtmlhttp://grantadesign.com/news/news/reports/wind.shtmlhttp://www.corrosionclinic.com/different_types_of_corrosion.htm