wind turbine report final

I

Engineering Design and Sustainability

Design and Manufacture of Wind Turbine Blades

Group A

Richard Sims 3200692 James Goddings 3131147 Mihail Kirov 272818 Daniel Dormer 2929611 Jamie Haslam 3222582 Josh Wilkinson 3129340 Adrian Elliot 3036931 Complied: 27th April 2015

Submission Date: 15th May 2015

(EEC_5_977_1415)

Marker: Dr. N. Zlatov

Abstract This report describes the procedure undertaken to design, develop, manufacture and test three

blades for a wind turbine. The product design specification is initially presented, identifying the key

design objects. This is then followed by a succinct review of design theory and calculations utilised to

validate the design. A cost for the system is presented, allowing commercial viability to be

determined. Subsequently, the manufacturing process is described along with an evaluation of the

test rig. The test methodology and results are then presented, followed by a critical analysis of the

data collected.

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Table of Contents Abstract ................................................................................................................................................... 0

1. Aim ...................................................................................................................................................... 3

2 Introduction ......................................................................................................................................... 3

3. Project Plan ......................................................................................................................................... 3

4. Project Design Specification ................................................................................................................ 4

5. Design .................................................................................................................................................. 4

5.1 Test Rig Evaluation ........................................................................................................................ 4

5.1.0. Wind Speed Evaluation ......................................................................................................... 4

5.1.1 Generator Considerations ...................................................................................................... 5

5.2. Theory and Design Calculations ................................................................................................... 5

5.2.0. Aerofoil Design ...................................................................................................................... 6

5.2.1. Betz’s Law .............................................................................................................................. 6

5.2.2. Aerofoil profile ...................................................................................................................... 7

5.3.1. Blue-Foam ............................................................................................................................. 9

5.3.2. MDF ....................................................................................................................................... 9

5.3.3. Fibre Glass ............................................................................................................................. 9

5.3.4. Aluminium ........................................................................................................................... 10

5.3.5. Design Scoring ..................................................................................................................... 10

5.4. Design Model ............................................................................................................................. 11

5.5. Costing ....................................................................................................................................... 11

6. Execution ........................................................................................................................................... 12

6.1 Part Manufacture ........................................................................................................................ 12

6.2 Part Assembly ............................................................................................................................. 13

6.3 Inspection of Parts ...................................................................................................................... 13

7. Electrical System Optimisation ......................................................................................................... 13

8. Wind Turbine Testing ........................................................................................................................ 15

9. Discussion .......................................................................................................................................... 15

10. Conclusion ....................................................................................................................................... 16

References ............................................................................................................................................ 17

APPENDIX A – Project Planning ............................................................................................................... 1

APPENDIX B – Wind Speed Distribution From Centre Of Hub ................................................................ 1

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APPENDIX C – Shimano DH-3N71 Generator Data ................................................................................. 2

APPENDIX D – NACA/NASA 4412 Aerofoil Data ...................................................................................... 4

APPENDIX E – Calculated Data ................................................................................................................ 5

Appendix F: Forces, Bending Moments and Deflection .......................................................................... 1

Appendix G: Cost breakdown ................................................................................................................. 1

APPENDIX H – Inspection Reports .......................................................................................................... 1

APPENDIX I – Electrical Optimalisation ................................................................................................... 2

APPENDIX J– Wind Turbine Testing ........................................................................................................ 4

3

1. Aim The aim of this report is to detail the process undertaken to design, develop, manufacture and test

three blades for a wind turbine. The purpose of the design is to extract maximum electrical power

out of the rig by optimising the turbine blade design. Particular emphasis is placed upon the

sustainability aspects throughout the whole of the project.

2 Introduction Wind turbine blades are shaped to generate the maximum power from the wind at the minimum

cost. Primarily the design is driven by the aerodynamic requirements, but this objective should be

met by well satisfying mechanical strength criteria and economical aspects. In particular, the blade

tends to be thicker than the aerodynamic optimum close to the root, where the stresses due to

bending are greatest.

The blade design process starts with a “best guess” compromise between aerodynamic and

structural efficiency. The choice of materials and manufacturing process will also have an influence

on how thin (hence aerodynamically ideal) the blade can be built. The chosen aerodynamic shape

gives rise to loads generated by lift, which are fed into the structure of the blade. Varying wind

speeds and directions give rise to uneven loading on the blades thus inducing additional forces to

the structure.

A detailed description of designing, planning, manufacturing and testing of a set of three wind

turbine blades is provided in the main body of this report.

3. Project Plan Project planning is a complicated process and its implementation goes through many iterations. As

pointed out by Newton (2009) project plans are fundamental to the way projects are managed as

they determine the cost, timescales and risk levels (Newton, 2009).

Appropriate planning enables cost, time, resources and progress to be established efficiently and

corrective actions to be undertaken, if deemed necessary.

A Master Plan having three milestones was prepared and agreed by all part-time students as a mean

of controlling and monitoring the progress of this project. A Work Breakdown Structure (WBS) was

used to prepare the project plan and define scope, objectives and deliverables for each work

element in the project. This can be found in Appendix A.

Gantt charts were developed from the WBS. As defined by Larson & Gray (2011) “The Gantt chart is

a visual flow diagram of the sequence, interrelationships, and dependencies of all the activities that

must be accomplished to complete the project” (Larson & Gray, 2011). Gantt charts provide the

project schedule by identifying dependencies, sequencing, and timing of activities, which the WBS is

not designed to do.

The Gantt charts for this project as well as the network diagram used for the Critical Path analysis

can be found in Appendix A.

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4. Project Design Specification Key Parameters for Blade design.

Number of Blades: Three to suit test rig.

Design Speed: 400 rpm to utilise maximum rated output of dynamo/generator.

Materials: Constructed from sustainable materials.

Method of construction: Simple, Low Cost, Repeatable, CAD / CAM precision, Low Starting

Inertia.

Set Dimensions: 510mm x 150mm x min 25 (mm)

5. Design

5.1 Test Rig Evaluation Before the turbine blade design could begin it was important to analyse the supplied test rig to

calculate the initial parameters. These include the

optimum operating speed of the generator, the

expected oncoming wind speed at the blades and the

dimensions of the hub to mount the blades to.

5.1.0. Wind Speed Evaluation

To calculate the wind speed expected at the turbine

blades, an investigation of the airflow profile and

distribution was carried out so the design of the blades

could be optimised to these conditions. An anemometer

was used to take measurements of the wind speed at

different distances from the centre of the hub as can be

seen in figure 1. The different positions at which

measurements were taken are represented by the black

dots. Tabulated results are shown in appendix B.

Figure 2 - Wind Speed Trend

The results from figure 2 above show that there is a near linear relationship between the wind speed

and the distance from the turbine centre. It was established that wind speed is inversely

proportional to the distance from the centre of its projection, a result which was expected. The

design of the blades needs to incorporate this variation in wind speed over the blade length.

Trend Line equation y = -22.925x + 11.544

0.00

5.00

10.00

15.00

0 0.1 0.2 0.3 0.4 0.5 0.6Win

d s

pe

ed

(m

/s)

Distance from turbine centre (m)

Wind speed vs distance from turbine centre

Figure 1- Wind Speed Measurements

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5.1.1 Generator Considerations

The driven generator which is used to produce electrical power was a key consideration in the

design process. Electrical generators are designed to deliver a specific output under intended

conditions.

The generator used for this investigation is a Shimano DH-3N71 dynamo hub designed for powering

bicycle lights. As per the datasheet in appendix C, it is an Induction AC generator specified to provide

3W at 6V, when built on a wheel measuring 700mm in diameter, of a bicycle travelling at 15km/h.

Tests performed by Andreas Oehler (Oehler, A., 2012) shown in figure 3 on various bicycle dynamo

hubs, including the successor to the DH-3N71, the DH-3N80, which contains the same generator

components with improved bearings and a lighter axle. These readings were made while attached to

a 24Ω resistor intended to simulate 2 lights in series. The voltage remained unregulated, allowing

the power output of the DH-3N80 to climb to 12.5W at 50km/h.

50km/h is a high speed for a bicycle, so it

would be an acceptable assumption that

this would be approaching the upper

design limit of the hub. This applies from

a mechanical standpoint, with regards to

bearing limitations, and an electrical one,

as AC generators become increasingly less

efficient as they exceed their designed

rotational velocity and internal resistance

and hysteresis increase dissipating energy

as heat. This upper limit is seen as a

practical starting point of design of the

turbine blades, and translates to

rotational velocity according to the

following calculations:

𝑣𝑏𝑖𝑐𝑦𝑐𝑙𝑒 = 50 [𝑘𝑚

ℎ] = 833.3 [

𝑚

𝑚𝑖𝑛] = 13.9 [

𝑚

𝑠]

Equation 2.3.i

𝑑𝑤ℎ𝑒𝑒𝑙 = 700[𝑚𝑚] = 0.7[𝑚]

Equation 2.3.ii

𝑣𝑏𝑖𝑐𝑦𝑐𝑙𝑒

𝜋𝑑𝑤ℎ𝑒𝑒𝑙=

833.3

𝜋 × 0.7= 379[𝑟𝑝𝑚] ≈ 400[𝑟𝑝𝑚]

Equation 2.3.iii

From this research the optimal operating speed of the generator was found to be 400rpm in which

the turbine blades will be designed around.

5.2. Theory and Design Calculations The fan is intended to simulate the presence of wind by producing a constant flow of air. However it

is not a true representation of how the wind turbine would perform in reality and therefore the

results will be an approximation. True wind would approach the turbine with uniform velocity

distribution across the swept area (ignoring ground effects). As per the wind speed evaluation the

fan on the test rig delivers a non-uniform, locally concentrated velocity distribution.

Figure 3 - Power Generated Versus Speed of Bicycle for Various

Bicycle Hub Generators (Oehler, 2012)

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It is therefore apparent that the optimum aerofoil design for achieving the maximum power in the

functional assessment of this project may not be a true representation of a real-world wind turbine

aerofoil. However, the development process is still very similar process to that of a real turbine.

5.2.0. Aerofoil Design

A combination and adaptation of approaches suggested by Hugh Piggott in Windpower Workshop –

Building Your Own Wind Turbine, and Barney Townsend in his Lecture Notes Aerofoil Selection and

Wind Turbine Design (see Appendix D) were used for the Aerofoil design.

Firstly a blade length of 510mm from the blade mounting bracket to the tip of the blade was decided

upon as a suitable; this was selected based on the wind speed distribution from the test rig fan (see

Section 5.1), allowing full use of the available wind, and coincided with being the maximum

permissible blade length. This resulted in making the overall length from the hub centre to the blade

tip 580mm,

Using Ragheb, M, (2014) Formulae a tip speed ratio was calculated based on the optimum generator

speed of 400rpm and a maximum wind speed of 10m/s (see Section 2.3.1) as follows:

𝑇𝑖𝑝 𝑆𝑝𝑒𝑒𝑑 𝑅𝑎𝑡𝑖𝑜 (𝜆) =𝜔𝑏𝑙𝑎𝑑𝑒 × 𝑟𝑏𝑙𝑎𝑑𝑒

𝑣𝑤𝑖𝑛𝑑

Equation 2.3.iv

𝑊ℎ𝑒𝑟𝑒: 𝜔 = 𝐴𝑛𝑔𝑢𝑙𝑎𝑟 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 (𝑟𝑎𝑑𝑠/𝑠𝑒𝑐) 𝑟 = 𝑅𝑎𝑑𝑖𝑢𝑠 𝑜𝑓 𝑏𝑙𝑎𝑑𝑒 (𝑚𝑒𝑡𝑒𝑟𝑠) 𝑣 = 𝑊𝑖𝑛𝑑 𝑠𝑝𝑒𝑒𝑑 (𝑚/𝑠𝑒𝑐)

Convert rpm to angular velocity = 𝜔 =𝑟𝑝𝑚×2𝜋

60

Equation 2.3.v

∴ 𝜆 =𝑟𝑝𝑚 × 2𝜋𝑟

60 × 𝑣

Equation 2.3.vi

𝜆 =400[𝑟𝑝𝑚] × 2𝜋 × 0.58[𝑚]

60 [𝑠

𝑚𝑖𝑛] × 10 [

𝑚

𝑠]

= 2.43 Equation 2.3.vii

This wind tip speed ratio is lower that the “optimal wind tip speed ratio is reported as 7” as reported

by Ragheb, M, (2014). Increasing this ratio would speed up the generator and thus it will run above

its optimal speed.

5.2.1. Betz’s Law

Betz’s Law states that the ratio of the

velocities of the wind incident on the turbine

and the wind behind the turbine is the

determining factor of how much energy can

be extracted from the wind, leading to a

maximum efficiency of any wind turbine of

59.3% at a velocity ratio of 1/3 downstream

to upstream (see Figure 4).

Figure 4 - Graph Illustrating Betz’s Limit.

(www.wind-power-program.com, 2015)

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As a turbine extracts energy from the wind, it slows the wind and accelerates the turbine blades; this

creates a pressure drop immediately downstream of the turbine in accordance with Bernoulli’s

principle. The energy extracted causes the blades to spin faster, however this increases effective

area of the turbine blades as a function of time, thus increasing the drag force as a function of time

see Equation 2.3.ix. An increased pressure zone in front of the turbine is created, however the

airflow is not contained, and therefore the pressure can dissipate laterally away from the blade.

𝑑𝐹𝐷

𝑑𝑡=

1

2𝜌𝑢2𝐶𝐷

𝑑𝐴

𝑑𝑡

Equation 2.3.ix

If the effective area of the turbine blades as a function of time increases beyond a certain point, the

braking effect on the wind from the drag of the blades becomes so great that the airflow deviates

around the turbine, bypassing the blades and creating an energy sapping vortex behind the turbine

as the air rushes to fill the decreased pressure area

immediately behind it. This slows the turbine,

resulting in a maximum rotational velocity that any

turbine can achieve dependent on the number of

blades and the incident drag effective surface area.

Figure 5 shows a chart of theoretically derived,

optimal power coefficients that turbines of differing

blade numbers can produce. This indicates that a 3

blade turbine would be most efficient at a tip speed

ratio of 6-8.

5.2.2. Aerofoil profile

A suitable Aerofoil profile was selected based on research and studying the NACA/NASA aerofoil

data available on Airfoil Tools website (http://airfoiltools.com/ ). A 4412 profile was decided upon

given its favourable Coefficient of Lift to Coefficient of Drag relationship, exhibited over relatively

wide range of Angle of Attack (see Appendix D).

The blade was divided into sections or stations along its length and the following calculations

performed for each station separated by 35mm giving 13 stations:

Firstly the wind velocity generated by the fan at each station perpendicular to the plane of the

turbine was calculated using testing data from the Test Rig Evaluation:

𝑣𝑟 𝑠𝑡𝑎𝑡𝑖𝑜𝑛 = −22.9𝑟𝑠𝑡𝑎𝑡𝑖𝑜𝑛 + 11.5

Equation 2.3.x

Then the wind velocity induced by the blades rotating at 400rpm in the plane of turbine was

calculated:

𝑣𝜃 𝑠𝑡𝑎𝑡𝑖𝑜𝑛 = 2𝜋𝑟 ×400𝑟𝑝𝑚

60 [𝑠

𝑚𝑖𝑛]

Equation 2.3.xi

Figure 5 - Graph of Tip Speed Ratio against Rotor Power

Coefficient Produced, (Predescu et Al. 2009)

http://airfoiltools.com/

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Then the resultant vector wind velocity and angle were

calculated using trigonometry, see Figure 6.

𝑢𝑠𝑡𝑎𝑡𝑖𝑜𝑛 = √𝑣𝑟 𝑠𝑡𝑎𝑡𝑖𝑜𝑛2 × 𝑣𝜃 𝑠𝑡𝑎𝑡𝑖𝑜𝑛

2

Equation 2.3.xii

𝛼𝑠𝑡𝑎𝑡𝑖𝑜𝑛 = 𝑡𝑎𝑛−1𝑣𝑟 𝑠𝑡𝑎𝑡𝑖𝑜𝑛

𝑣𝜃 𝑠𝑡𝑎𝑡𝑖𝑜𝑛

Equation 2.3.xiii

A method proposed was then used whereby a uniform

chord length for the aerofoil was adopted along its length,

and the Lift Force generated at each station calculated (see Equation 2.3.xviii). Due to the Plan

Viewed Surface Area being a contributory factor to the Lift Force generated by an Aerofoil, the

maximum chord length permitted by the brief of 150mm (0.15m) was used.

𝑅𝑒𝑦𝑛𝑜𝑙𝑑𝑠 𝑁𝑢𝑚𝑏𝑒𝑟 (𝑅𝑒) =𝜌𝑎𝑖𝑟𝑣𝑤𝑖𝑛𝑑𝑙𝑐ℎ𝑜𝑟𝑑

𝜇𝑎𝑖𝑟

Equation 2.3.xiv

𝑅𝑒 =1.2 [

𝑘𝑔

𝑚3] {@20°𝐶} × 10 [𝑚

𝑠] × 0.15[𝑚]

1.51 × 10−5 [𝑚2

𝑠] {@20°𝐶}

= 119205

Equation 2.3.xv

𝐴𝑝𝑝𝑒𝑛𝑑𝑖𝑥 𝐷: 𝐴𝑒𝑟𝑜𝑓𝑜𝑖𝑙 4412, 𝑅𝑒 = 100,000 𝑎𝑛𝑑 𝐴𝑂𝐴 = 5° → 𝐶𝐿 = 1.0, 𝐶𝐷 = 0.02

Equation 2.3.xvi

𝐿𝑖𝑓𝑡 𝐹𝑜𝑟𝑐𝑒 𝐹𝐿 𝑠𝑡𝑎𝑡𝑖𝑜𝑛 =1

2𝐶𝐿 𝜌𝑢𝑠𝑡𝑎𝑡𝑖𝑜𝑛

2 𝐴𝑠𝑡𝑎𝑡𝑖𝑜𝑛

Equation 2.3.xvii

𝐹𝐿 𝑠𝑡𝑎𝑡𝑖𝑜𝑛 =1

2× 1 × 1.2 [

𝑘𝑔

𝑚3] × 𝑢𝑠𝑡𝑎𝑡𝑖𝑜𝑛

2 [𝑚

𝑠] × (0.035 × 0.15)[𝑚2] Equation 2.3.xviii

To balance the lift forces along the blade, in order to equalise stresses along its length and maximise efficiency, a number of methods could have been implemented as follows:

Altering the angle of attack of each station relative to the resultant wind to change the

coefficient of lift, and therefore lift force.

Altering the blade profile at each station to change the coefficient of lift, and therefore lift

force.

Altering the chord length, and therefore surface area, to change the lift force.

The third of these methods was chosen; because the stations were all the same width it was only

necessary to adjust chord length at each station in order to effect a proportional change in lift force.

This was done by taking the lift force at each station, subtracting the lowest lift force value, and

dividing 150mm (0.15m) by this value to generate the new chord length, thereby balancing the lift

forces see Equation 2.3.xvii. Tables in Appendix E show the resulting data from these calculations at

each of the 13 stations.

𝑙𝑐ℎ𝑜𝑟𝑑 𝑎𝑑𝑗𝑢𝑠𝑡𝑒𝑑 𝑠𝑡𝑎𝑡𝑖𝑜𝑛 =𝐹𝐿 𝑚𝑖𝑛

𝐹𝐿 𝑠𝑡𝑎𝑡𝑖𝑜𝑛× 150𝑚𝑚

Equation 2.3.xix

It was realised that the two final smallest profile elements were not practical for construction so the

last three elements were to be identical in chord length as the additional lift would be minimal.

Figure 6 - Resultant vector wind on turbine blades

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5.3. Product Designs

There are a variety of ways to accomplish the task of constructing wind turbine blades and there are

numerous materials which can be used. The most readily obtainable materials are, Blue-Foam,

Aluminium, MDF (Medium Density Fibreboard) and Fibre Glass. The task to create 3 turbine blades

using sustainable materials which ideally are not too heavy or too light and can be designed and

assembled within a relatively short timeframe. Below are the materials and design concepts which

were chosen for the task with their characteristics and a brief description of their pros and cons.

5.3.1. Blue-Foam

Blue extruded polystyrene foam is light weight foam which is easily carved and shaped. It has a high

compressive strength due to its rigid cell makeup and high water resistivity.

The design for the hollow PVC wing would consist of shaping the solid blue foam block into a mould,

then vacuum forming a PVC outer shell around it.

Cons

Production of the foam is not fully sustainable as it is manufactured from crude oil.

Harmful to humans if the dust is inhaled a possible carcinogen.

Low tensile strength Pros

It is very light.

Easy to carve and shape.

High compressive strength

5.3.2. MDF

MDF or (Medium Density Fibreboard) is made from wood shavings mixed with wax and resin which

is then heated and compressed to create a dense, easy to shape and light wood substitute. The MDF

design would consist of either a solid block shaped by hand or a ribbed wing of 2.5 mm thick sections.

Cons

Loses rigidly if exposed to water.

If designed as a solid blade it would heavy, which can increase the initial inertia. Pros

Sustainable material, made from previously recycled wood shavings.

Not too light as to slow to a stop if an electrical resistance is applied.

Easy to work with, can be cut by laser.

5.3.3. Fibre Glass

Fibre reinforced plastic or fibre glass is a strong and light weight material made from a composite of

plastics, a woven glass fibre mat like weave which can be used for example to reinforce plastic

resins. The idea of using fibre glass would be in a typical wing shape, the method would be similar to

the blue foam method needing a solid base. However then it would need several layers of resin and

fibre glass. Due to timescales and the hazardous nature it was decided not to go any further in the

design.

Cons

Difficult to work with

Damages the environment as made from toxic resins

Harmful to health if inhaled and possible carcinogenic

Pros

Strong and lightweight

Water resistant

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5.3.4. Aluminium

Aluminium is a strong and low density light weight metal with excellent malleability and easy to machine. The Aluminium design would be a curved sheet design as a solid design would be heavy and very time consuming. Two curved sheet designs were looked at however one was better suited to a vertical wind turbine.

Cons

Energy hungry in its production

Relatively expensive compared to the other materials.

Time consuming to build with. Pros

Very strong and lightweight for a metal.

Rust resistant.

Easy to recycle.

5.3.5. Design Scoring

To find a viable choice of build and material, an implementation checklist was created. The material

and build attributes were scored between 1 and 10 to define the strengths and weaknesses of their

materials and design.

Materials Sustainability Workability Material

Weight

Machining Accuracy

Timescales Material

strength

Total

Aluminium 7 2 6 8 -9 9 23

MDF solid 7 8 6 5 -7 5 24

Fibreglass 5 2 7 2 -9 8 17

Vacuum

Formed PVC

5 7 5 6 -5 3 21

2.5mmm MDF Ribbed 7 8 6 9 -3 5 32

Table 1 - Results from the Implementation Checklist

The final result gave favour to the ribbed wing build, this led to two further options being available,

the first was to model the wing in CAD and import it to 123D Make, by Autodesk. This creates a

skeleton in a lattice style of the wing. The MDF could then be laser cut and joined together like a 3D

jigsaw and could then be wrapped in a light material. The 2nd option was to create the NACA profiles

of different sizes in CAD, then convert the file to manufacture them using the laser cutter from

2.5mm MDF. They would then be joined via a strong spine with a solid.

Due to time restrictions it was decided to use the latter rib with metal spine method. As little was

known of the Autodesk software and it would be advantageous to be able to alter the aerofoil

section angles to optimise the design.

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NoRequired

Resources

Cost

per blade

(£)

Total

Cost

(£)

for 3

blades

1 Materials 11.30 33.90

2 Labour 23.50 70.50

34.80£ 104.40£ Total

Table 2: Summary of materials and labour costs

y = 0.3255x0.2608 R² = 0.9999

0

0.1

0.2

0.3

0.4

0.5

0.6

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Dis

tan

ce f

rom

, Bla

de

Ro

ot

(m)

Deflection (mm)

Deflection along blade length

5.4. Design Model The process of 3D virtual prototyping

required the complex review of drag and lift

coefficients, mechanical loads based upon

permissible and realistic performance goals

set out in the PDS.

A final design of the blades was generated in

Autodesk Inventor. The virtual design was

then put through FEA to ensure that the

design is capable of withstanding the

expected loads, in addition to the mechanical

and aerodynamic loads.

Deflection calculations were

carried out to identify the

stiffness of the design as a result

of the stresses on the blade

surface this can be seen in figure

8 opposite. Full calculations are in

appendix F. The maximum

deflection seen is 6mm at the tip

of the blade this is acceptable

considering the materials used

and the minimal stress it

generates over the length of the

blade.

From both of these stress analysis methods it can be seen the initial design of the blade is suitable

for operation and can be progressed to manufacture.

5.5. Costing For the purpose of this project only direct costs for labour and material have been taken into

account. Overhead costs, marketing, transportation etc. were excluded from it. Table 1 provides a

summary of materials and labour costs for the project.

Notes:

1. Electrical parts not included

2. Workshop machinery and depreciation of assets not included

3. Overheads, marketing, transportation etc. cost not included

Table 2 - Summary of materials and labour cost

Figure 7 - Blade FEA

Figure 8 - Blade Deflection

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A detailed breakdown of materials and labour costs required for manufacturing a set of three wind

turbine blades can be found in Appendix G.

Cost, time, and budget estimates are the lifeline for control of the project’s progress; they serve as

the standard for comparison of actual and plan throughout the life of the project.

In summary, planning establishes the way projects are managed as they determine the cost,

timescales, required resources and risk levels. The WBS is used to decomposition the projects into

more manageable chunks of work and assign ownership for tasks. Gantt charts are usually the most

popular form of plan presentation. Alternatively box plans or network diagrams could be used. More

detailed plans are often perceived to be better plans.

6. Execution

6.1 Part Manufacture Manufacturing initially began with cutting

the rib profiles on the universal laser

cutter. This involved arranging the

required profiles onto the supplied LSBU

.dwt template laid out in a way as to

minimise the wastage. With a 3mm sheet

of MDF placed in the machine the

populated template was sent to cutter for

manufacture. Once these profiles had

been cut they were gently pressed out by

hand.

Manufacture of the 3x blade bases began from 25mm MDF

cut to 150 x 75mm. The 150mm aerofoil shape was dawn on

the upper and lower edges, with the band saw these

markings were followed and an accurate smooth finish

gained using the linisher. The 5x 5mm holes drilled on the

pillar drill and the upper M6 hole drilled and tapped on the

mill.

3 lengths of M6 stainless steel studding cut to 260mm and 3

lengths of M3 stainless steel studding cut to 190mm, ends de-

burred.

To join the studs together an adaptor was manufactured on the

lathe 8mm in diameter and 15mm in length, drilled and tapped M3

one end and M6 the other.

Figure 7- Laser cut profiles

Figure 8 - Blade base

Figure 9 - M3 / M6 stud adaptor

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6.2 Part Assembly

The rib sections were attached to

the studding with a nut either side,

each rib was spaced at 35mm pitch

from the end of the studding. The

blade base was screwed on to give

a distance of 35mm to the first rib

and locked in place with an M6 nut.

The nuts tightened once the ribs

had been aligned parallel.

A jig was manufactured to assist twisting each rib section. The blade

base was mounted to a 90° angle plate, the jig was placed behind

each rib and the rib twisted to the required marking on the jig.

Once the ribs had been twisted on all three blades the aluminium

foil tape could be applied. Starting from the rear of the aerofoils the

tape was laid down the blade pressing the tape onto each rib

section. The final layer of tape was curled to shape over the leading

radius of the aerofoils before applying to give a smooth finish.

6.3 Inspection of Parts

To reduce the vibrations generated by the turbine the three blades required balancing. Once all

three blades had been manufactured, each blade was weighed. Weight was removed from the

heavier blades by drilling holes into the MDF blade bases; minor weight was added by applying small

pieces of aluminium foil tape until each blade weighed within 0.02g of each other.

After completion of each individual component, checks were carried out to ensure they were

manufactured as per the drawings, see appendix H for inspection reports. Inspection at such an early

stage ensured each part was correctly manufactured before adding it to the final part preventing

problems later down the build stage.4. Testing

7. Electrical System Optimisation The system was initially tested a 3W 6V lamp as the load placed on the system. This allowed basic

demonstration of the system. However, this limited the amount in which the load could be varied

therefore, the optimal load could not be found. It was also found from the preliminary testing that

the system provided power in excess of the lamps rated operating conditions, resulting in several

lamps being blown. This corresponds to the warnings from the dynamo datasheet (appendix C); this

hub dynamo does not have overvoltage protection inside the hub itself Technical Service

Information DH-3N71 (2006). The rotational shaft speed (RPM) controls the dynamo or alternator’s

output voltage (Holden ,2011) therefore suggesting that the system was rotating faster than the

dynamo was designed for.

Figure 11 - Blade Pitching

Figure 10 - Blade Twisting

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The load was changed from the lamp to a large variable resistor selected with appropriate power

handling capability. Changing the load yielded two significant advantages, firstly, it meant that the

system load could easily be varied to find optimum load. Secondly, as the load was purely resistive,

this simplified electrical calculations as Ohm’s law could be applied. The familiar Ohm’s law triangle

used for DC circuits can only be used at AC if the load is purely resistive (Collinson (No Date)).

A basic schematic of the electrical system can be seen below in figure 12.

With the blades set to an angle of attack of 28.5° the resistive load was varied to obtain the

maximum calculated power. As only voltage and current could be measured, power and resistance

were calculated using equations 7.i. & 7.ii.

Power was calculated by:

𝑃 = 𝑉 ∗ 𝐼

Equation 7.i. [Source: (Collinson (No Date))].

𝑊ℎ𝑒𝑟𝑒:

𝑃 = 𝑃𝑜𝑤𝑒𝑟 (𝑊𝑎𝑡𝑡𝑠)

𝑉 = 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 (𝑉𝑜𝑙𝑡𝑠)

𝐼 = 𝐶𝑢𝑟𝑟𝑒𝑛𝑡 (𝐴𝑚𝑝𝑠)

The general term for AC resistance is impedance and given the symbol Z (Collinson (No Date)). The

AC resistance was calculated using the following equation:

𝑍 = 𝑉/𝐼

Equation 7.ii. [Source: (Collinson (No Date))].

𝑊ℎ𝑒𝑟𝑒:

𝑍 = 𝐴𝐶 𝑟𝑒𝑠𝑖𝑠𝑡𝑎𝑛𝑐𝑒 (𝑂ℎ𝑚𝑠)

!!

R!Load!

V(s)!!From!Dynamo!

I!>!

Figure 12 - Schematic of Electrical System

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The results attained from the testing can be seen in table 3 below.

Voltage (Volts) Current (Amps) Power (Watts) [Calculated]

AC Resistance (Ω) [Calculated]

24 0.23 5.5 104.35

22 0.26 5.7 84.6

21 0.29 5.9 72.4

18 0.3 5.4 60

15 0.34 5.1 44.12 Table 3- Results & Calculations from Electrical Optimisation

All results collected were tested with the initial calculated angle of attack at 28.5° and fixed position

relative to wind source. Appendix I contains images taken from the electrical calibration testing

8. Wind Turbine Testing Once the electrical system had been optimised, the angle of attack for the blades was optimised.

This was achieved by keeping the load constant and varying the angle of attack of the blades. During

testing, the distance between the fan and wind source was kept constant. The results collated from

the wind turbine testing can be seen in table 4 below. During the testing of the 40° angle of attack,

the stress in the system caused one of the M3 bolts in the hub to shear and fail. This was fixed and

re-tested, the image of the failure can be seen in appendix J.

Angle Of Attack

(Degrees)

Speed unloaded

Speed with load

Current Voltage

Unloaded Voltage Loaded

Power Watts

(Loaded) [Calculated]

20 162 112 0.200 17.5 14.0 2.8

28.5 300 168 0.290 37.0 21.0 6.09

35 360 215 0.370 39.0 27.5 10.175

40 415 300 0.412 44.0 31.7 13.06 Table 4 - Results from Wind Turbine testing

9. Discussion When designing the wind turbine blades, it was important to consider the environmental impacts of

the project both locally and globally, and seek sustainable solutions in accordance with the UK

Government’s Sustainable Development Strategy (Guidance on Sustainability, 2015). Design

decisions were supported by a life cycle assessment which assessed the full range of environmental

effects involved in the design and manufacture of the turbine blades with particular attention to the

product life cycle of the materials used. Design was therefore focused on using renewable materials

such as the recyclable aluminium foil. According to Earth911, "it takes 95 percent less energy to

make aluminium from recycled aluminium, versus using virgin material from bauxite ore (Keen For

Green, 2015).

The turbine blades were also designed carefully to be efficient and produce the most power with the

given power input.

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10. Conclusion The report has shown the process undertaken to design, manufacture and test the three wind

turbine blades. It has been shown that the design is capable of producing 13.06 Watts enough

power not only to light the lamp but to blow it.

It was also found during the testing that both the electrical load and system setup could be

calibrated in order to achieve optimal performance. It was found that an angle of attack of 40°

creating maximum power when connected to a purely resistive load of 72.4Ω.

During the testing it was found that the rig in which the turbine blades were connected to had

significant design flaws in that, it was unable to handle the stress forces created by the rotational

speeds achieved by this design.

In conclusion, it was demonstrated in the report and testing that the design was capable of

exceeding the design requirements set out in the product design specification and that the aims set

out at the beginning have been achieved.

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References

Collinson, (No Date) Ohm’s law for AC Circuit. [ONLINE] Available at:

http://www.zen22142.zen.co.uk/Theory/ohmac.htm (Accessed: 03 May 2015)

Guidance on Sustainability, Engineering Council, 2015. [ONLINE] Available

at:http://www.engc.org.uk/engcdocuments/internet/Website/Guidance%20on%20Sustainability.pdf. [Accessed 10.05.

2015].

Holden, H (2011) The Dynamo & Alternator Emulator . Available from:

http://www.worldphaco.net/uploads/EMULATOR.pdf [Accessed: 04 May 2015]

Keen For Green, Can You Recycle Tin Foil? 2015, [ONLINE] Available at:

http://www.keenforgreen.com/recycle/is_tin_aluminum_foil_recyclable. [Accessed 10 May 2015].

Larson, E.W. & Gray, C.F. (2011). Project Management - The Managerial Process. 5th ed. New York: McGraw- Hill.

Newton, R. (2009). The practice and theory of project management – creating value through change. 1st ed. New York:

Palgrave McMillan.

Piggott, H., 1995, Windpower Workshop – Building Your Own Wind Turbine, Centre for Alternative Energy Publications,

Edition 2004

Ragheb, M., 2014, Optimal Rotor Tip Speed Ratio, 3/11/2014,

Availaible from: www.mragheb.com (accessed on 10/04/15)

Technical Service Information DH-3N71 (2006). Available from:

http://bike.shimano.com/media/techdocs/content/cycle/SI/HubDynamo/DH-3N71/2ZR0B-DH-3N71-

EN_v1_m56577569830600105.pdf [Accessed: 03 May 2015]

http://www.zen22142.zen.co.uk/Theory/ohmac.htm

http://www.engc.org.uk/engcdocuments/internet/Website/Guidance%20on%20Sustainability.pdf

http://www.worldphaco.net/uploads/EMULATOR.pdf

http://www.keenforgreen.com/recycle/is_tin_aluminum_foil_recyclable

http://bike.shimano.com/media/techdocs/content/cycle/SI/HubDynamo/DH-3N71/2ZR0B-DH-3N71-EN_v1_m56577569830600105.pdf

http://bike.shimano.com/media/techdocs/content/cycle/SI/HubDynamo/DH-3N71/2ZR0B-DH-3N71-EN_v1_m56577569830600105.pdf

APPENDIX A – Project Planning

Work Breakdown Structure

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Wind Turbine Project – Gantt Chart

Network Diagram – Critical Path Analysis

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APPENDIX B – Wind Speed Distribution From Centre Of Hub

Distance from centre of hub (m)

0 0.1 0.2 0.3 0.4 0.5

Win

d S

pee

d m

/s

8.5 8.4 5.5 2.5 0.6 0

8.5 11 10 7 4 2

8.5 11 10 8 4 1.5

8.5 10 7.5 5 3 2

8.5 8 6.5 3.5 0.5 0

8.5 6 3 1.5 0.2 0

8.5 9 5 2 0.3 0

8.5 10 9 8 6 4

Average 11.00 9.18 7.06 4.69 2.33 1.19

Wind Speed Measurement Points

100mm Pitch From Hub Centre

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APPENDIX C – Shimano DH-3N71 Generator Data

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APPENDIX D – NACA/NASA 4412 Aerofoil Data

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APPENDIX E – Calculated Data

Calculated data from Equations 2.3.ix-2.3.xvi deriving the chord lengths needed to

balance the lift force generate along the turbine blade at 400rpm.

Station 𝒓 𝒗𝒓 𝒗𝜽 𝜶 𝒖 𝒍𝒄𝒉𝒐𝒓𝒅 = 𝟏𝟓𝟎𝐦𝐦

𝑭𝑳 𝒍𝒄𝒉𝒐𝒓𝒅 adjusted

[m] [m/s] [m/s] ° [N] [mm]

1 0.12 9.79 5.03 62.83 11.01 0.38 150.00

2 0.155 8.99 6.49 54.16 11.09 0.39 147.78

3 0.19 8.19 7.96 45.81 11.42 0.41 139.39

4 0.225 7.39 9.42 38.08 11.97 0.45 126.77

5 0.26 6.58 10.89 31.15 12.73 0.51 112.23

6 0.295 5.78 12.36 25.07 13.64 0.59 97.66

7 0.33 4.98 13.82 19.81 14.69 0.68 84.20

8 0.365 4.18 15.29 15.28 15.85 0.79 72.35

9 0.4 3.37 16.76 11.39 17.09 0.92 62.22

10 0.435 2.57 18.22 8.03 18.40 1.07 53.67

11 0.47 1.77 19.69 5.14 19.77 1.23 46.52

12 0.505 0.97 21.15 2.62 21.18 1.41 40.53

13 0.540 0.16 22.62 0.42 22.62 1.61 38.22

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Station Chord Lengths and Rib Angles For 4412 Aerofoil Profile Final Blade Design at

400rpm.

Station Number

Chord

Length

[mm]

Length of Blade [mm]

Angle of

Twist

[mm]

1 147 40 0.00

2 150 75 12

3 147 110 20

4 140 145 27

5 130 180 33.5

6 116 215 39

7 103 250 43.5

8 91 285 47.5

9 80 320 51

10 70 355 54

11 61 390 56

12 47 425 58.5

13 47 460 60

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Appendix F: Forces, Bending Moments and Deflection Detailed Calculation of the Velocity Pressure, Forces and Resultant Bending moments and Deflections for the Wind turbine Blades

C-1

Appendix G: Cost breakdown

Detailed breakdown of materials and labour costs required for manufacturing a set of three wind turbine blades

No Materials Quantity

per blade

Materials

cost

(£)

per blade

Total

Quantity

for 3 blades

Total

Materials

cost

(£)

for 3 blades

Assembly

time

(minutes)

per blade

Total

Assembly time

(minutes)

for 3 blades

Labour

cost

(£)

per hour

Labour

cost

(£)

per blade

Total

Labour cost

(£)

for 3 blades

1 M3 threaded rod 0.3 mtrs 0.70 1 mtr 2.10 5 min 15 min 10.00£ 0.83 2.50

2 M6 threaded rod 0.3 mtrs 0.90 1 mtr 2.70 5 min 15 min 10.00£ 0.83 2.50

3 M3 hexagonal nuts 12 0.64 36 1.92 5 min 15 min 10.00£ 0.83 2.50

4 M6 hexagonal nuts 13 0.79 39 2.37 5 min 15 min 10.00£ 0.83 2.50

5 Alluminium bar Ø8 1 3.60 3 10.80 40 min 120 min 10.00£ 6.67 20.00

6 MDF base Ø15 1 0.42 3 1.26 40 min 120 min 10.00£ 6.67 20.00

7 Alluminium foil tape 3 mtrs 1.35 9 mtrs 4.05 20 min 60 min 10.00£ 3.33 10.00

8 Blade ribs 12 2.90 36 8.70 20 min 60 min 10.00£ 3.33 10.00

9 Ballancing N/A 0 N/A 0 10 min 30 min 10.00£ 0.17 0.50

11.30£ 33.90£ 2.5 hours 7.5 hours 23.50£ 70.50£

Notes:

Total

1. Electrical parts not included

2. Workshop machinery and depreciation of assets not included

3. Overheads, marketing, transportation etc. cost not included

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APPENDIX H – Inspection Reports

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APPENDIX I – Electrical Optimalisation

Image of Preliminary testing with 3W 6V lamp fitted.

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Image of test setup with power resisters

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APPENDIX J– Wind Turbine Testing

Image of sheared M3 bolt on hub.

wind turbine report final

Documents