Design small scale wind turbine for home electricity generation

Wind Turbine Design

Project

AE5 – Design Small Scale Wind Turbine

for Home Electricity Generation

March 2013

By

Maheemal K.B. (0923688)

Kalinga Ellawala (0628552)

Bhavdeep Pancholi (0906043)

Mishkath Harees (0806420)

Abstract Wind Turbines are one the oldest known method used to extract energy from the natural sources

(wind in this case). With the changing weather and wind speed, it is not possible to produce high

constant power from the wind turbine but a small scale wind turbine can be used to power small

appliances at home, e.g. fridge. This project looks into thetechnical and marketing aspects for an

innovative design of a small scale wind turbine designed for supplying home electricity. The report

includes content on design, enhancement, power management, manufacturing methods, cost

analysis & marketing issues; processes which are considered for creating new patent and putting into

development.

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Acknowledgement (BP)

We would like to express our gratitude to all those who gave us the possibility to complete this

design project. We would like to thank Brunel School of Design & Engineering and all the professors

involved in this module for giving us permission to commence this project in the first instance, to do

the necessary research work and to use departmental data and knowledge.

We also like to take this opportunity to thank our project supervisor Dr. A. Gatto whose help,

suggestions and encouragement helped us stretch our ideas further then our own imaginations.

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

Acknowledgement (BP) ........................................................................................................................... 1

1 Introduction (BP) ............................................................................................................................. 0

1.1 Aim .......................................................................................................................................... 0

1.2 Design Brief ............................................................................................................................. 0

2 Current Designs (KE) ........................................................................................................................ 1

2.1 Energy ball V200 ...................................................................................................................... 1

2.2 Honeywell WT6500 Wind Turbine .......................................................................................... 1

2.3 Hannevind 2.2 kW ................................................................................................................... 2

2.4 Windon 2 kW ........................................................................................................................... 2

2.5 Bergey Excel............................................................................................................................. 3

2.6 Southwest Windpower Skystream 3.7 .................................................................................... 3

2.7 Windsave WS500 ..................................................................................................................... 3

2.8 Renewable Devices – Swift ...................................................................................................... 4

3 The Wind (BP) .................................................................................................................................. 4

3.1 Geographical Analysis.............................................................................................................. 4

3.2 UK Historical Data .................................................................................................................... 6

4 The Wind & the Blades .................................................................................................................... 7

4.1 Wind power calculations ......................................................................................................... 7

4.2 The Blades ............................................................................................................................... 9

4.2.1 Number of Blades ............................................................................................................ 9

4.2.2 Aerofoil & Load ................................................................................................................ 9

4.2.3 Materials ........................................................................................................................ 12

4.2.4 Wind Speed ................................................................................................................... 12

4.2.5 Angle of Attack .............................................................................................................. 13

4.3 Power Extracted .................................................................................................................... 13

4.4 Acoustics & Insulation ........................................................................................................... 13

5 Generator (KE) ............................................................................................................................... 14

5.1 AC & DC Generator ................................................................................................................ 14

5.2 Induction Generator .............................................................................................................. 15

5.3 Generator types .................................................................................................................... 15

5.3.1 Synchronous Generator (SG) ......................................................................................... 15

5.3.2 Permanent magnet synchronous Generator (PMSG) ................................................... 15

5.3.3 Switched reluctance generator (SRG) ........................................................................... 16

5.4 Permanent magnet generators ............................................................................................. 16

5.4.1 The magnetic flux orientation (Radial Flux or Axial Flux) .............................................. 17

5.4.2 Longitudinal or Transversal (Figure 5.4.1) ..................................................................... 17

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5.4.3 Inner Rotor or Outer Rotor ............................................................................................ 18

5.5 Coil winding arrangements ................................................................................................... 18

5.5.1 Coil placement ............................................................................................................... 18

5.5.2 Coil winding distribution ............................................................................................... 19

5.5.3 Pole slot combinations .................................................................................................. 19

6 Advantages and Disadvantages of Wind Turbine Designs (MT).................................................... 19

6.1 Horizontal Axis Wind Turbines .............................................................................................. 19

6.1.1 Advantages of Horizontal Axis Wind Turbines .............................................................. 19

6.1.2 Disadvantages of Horizontal Axis Wind Turbines .......................................................... 20

6.2 Vertical Axis Wind Turbines ................................................................................................... 20

6.2.1 Advantages of Vertical Axis Wind Turbines ................................................................... 21

6.2.2 Environmental Benefits ................................................................................................. 21

6.3 Comparison between Vertical designs Vs. Horizontal designs ............................................. 21

6.4 Justification for design choice ............................................................................................... 22

7 Wind Turbine Power Management (MH) ...................................................................................... 22

8 Safety Systems for Wind Turbines (MH) ....................................................................................... 23

8.1 Vibration Sensors .................................................................................................................. 23

8.2 Turbine over-speed ............................................................................................................... 24

8.3 Thermal and other sensors.................................................................................................... 24

8.4 Anti-Icing Systems ................................................................................................................. 24

8.5 Material Failure ..................................................................................................................... 24

9 Manufacturing Methodology and Processes (MH) ....................................................................... 25

9.1 Design for Manufacture/Design for Assembly ...................................................................... 25

9.2 Material Selection ................................................................................................................. 26

9.3 Material Properties ............................................................................................................... 26

9.4 Cost and Availability .............................................................................................................. 27

9.5 Selection of manufacturing processes .................................................................................. 27

9.6 Metal and Metal Alloys ......................................................................................................... 28

9.7 Metal Casting Processes ........................................................................................................ 28

9.8 Sand Casting .......................................................................................................................... 30

9.9 Sands ..................................................................................................................................... 31

9.10 Types of Sand Moulds ........................................................................................................... 31

9.11 Patterns ................................................................................................................................. 31

9.12 Sand-Moulding Machines ...................................................................................................... 32

9.13 The Sand Casting Operation .................................................................................................. 32

9.14 Die Casting ............................................................................................................................. 33

9.15 Hot-Chamber Process ............................................................................................................ 33

9.16 Cold-Chamber Process .......................................................................................................... 33

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9.17 Process Capabilities and Machine Selection ......................................................................... 34

9.18 Forging of Metals ................................................................................................................... 34

9.19 Extrusion and Drawing of Metals .......................................................................................... 35

9.20 Forming and Shaping Plastics ................................................................................................ 35

9.21 Injection Moulding ................................................................................................................ 36

9.22 Process Capabilities ............................................................................................................... 37

9.23 Rotational Moulding .............................................................................................................. 37

10 Product Design Specification (MH/MT) ..................................................................................... 38

11 Design Conceptualisation .......................................................................................................... 41

11.1 Blade (BP) .............................................................................................................................. 41

11.1.1 Design 1 ......................................................................................................................... 42

11.1.2 Design 2 ......................................................................................................................... 42

11.1.3 Design 3 ......................................................................................................................... 42

11.1.4 Aerofoil Shape ............................................................................................................... 43

11.1.5 Materials ........................................................................................................................ 43

11.2 Generator (KE) ....................................................................................................................... 43

11.2.1 Design 1 ......................................................................................................................... 43

11.2.2 Design 2 ......................................................................................................................... 44

11.2.3 Design 3 ......................................................................................................................... 45

11.2.4 Design 4 ......................................................................................................................... 45

11.3 Preliminary Design of braking and mounting systems (MH) ................................................. 46

11.3.1 Braking Systems ............................................................................................................. 46

11.3.2 Braking System Design 1 ............................................................................................... 46



11.4 Mounting System (MH) ......................................................................................................... 47

11.4.1 Mounting System Method 1 .......................................................................................... 47

11.4.2 Mounting system 2 ........................................................................................................ 48

11.4.3 Mounting System 3 ....................................................................................................... 48

11.5 Popular Wind turbine arrangements for domestic use (MT) ................................................ 49

11.5.1 Introduction ................................................................................................................... 49

11.5.2 Series Regulators ........................................................................................................... 49

11.5.3 Shunt Regulators ........................................................................................................... 50

11.5.4 Two modes of operation ............................................................................................... 50

11.5.5 Pulse Width Modulation Regulators ............................................................................. 50

11.5.6 PWM regulator with a dump load ................................................................................. 51

11.5.7 Shorting the generator output? .................................................................................... 51

11.5.8 Wind compatible “Solar style” charge controllers? ...................................................... 51

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11.5.9 Maximum Power Point Tracking ................................................................................... 52

11.5.10 Hysteresis .................................................................................................................. 52

11.5.11 Lead-Acid Batteries .................................................................................................... 52

11.5.12 Dump Loads (as used in 'battery shunt' configuration) ............................................ 53

11.5.13 Braking Resistor (as used in 'turbine brake controller' configuration) ..................... 53

11.5.14 Grid Tie Inverters ....................................................................................................... 53

12 Preliminary Design & Analysis ................................................................................................... 54

12.1 The Blades, the Hub & the Cone (BP) .................................................................................... 54

12.2 Generator design selection (KE) ............................................................................................ 55

12.2.1 Design Selection ............................................................................................................ 55

12.2.2 Design improvements for the preliminary generator design ........................................ 56

13 Final Design (BP) ........................................................................................................................ 57

13.1 FEA Analysis (MT) .................................................................................................................. 59

13.2 Bill of Material (MT) .............................................................................................................. 62

13.3 Blades (BP) ............................................................................................................................. 63

13.4 Bearings (BP/MH) .................................................................................................................. 64

13.5 Final Generator Design (KE) .................................................................................................. 64

13.5.1 Rotor .............................................................................................................................. 64

13.5.2 Stator ............................................................................................................................. 65

13.5.3 Final assembly of the generator .................................................................................... 66

13.5.4 Power Calculations ........................................................................................................ 67

13.5.5 Power Curve .................................................................................................................. 69

13.5.6 Method .......................................................................................................................... 69

13.5.7 Generator circuit (stator to blade point) ....................................................................... 70

13.6 Power Management (MT) ..................................................................................................... 70

13.7 Maintenance (ALL) ................................................................................................................ 71

13.7.1 Generator ...................................................................................................................... 71

13.7.2 Tips for long lasting power management system ......................................................... 72

14 Manufacturing (MH) .................................................................................................................. 72

15 Business Model Evaluation of wind turbine (MH)..................................................................... 73

15.1 Material Costs........................................................................................................................ 73

15.2 Manufacturing Costs ............................................................................................................. 75

15.3 Marketing Costs ..................................................................................................................... 75

15.4 Premises Costs ....................................................................................................................... 76

15.5 Labour/staffing Costs ............................................................................................................ 76

15.6 Operational Costs .................................................................................................................. 77

15.7 Revenue ................................................................................................................................. 78

15.8 Profit Margins ........................................................................................................................ 78

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16 Conclusion (KE/MT) ................................................................................................................... 84

16.1 Design Specification .............................................................................................................. 84

17 Works Cited ............................................................................................................................... 85

18 Appendix-A (ALL) ....................................................................................................................... 87

18.1 Figures ................................................................................................................................... 87

18.2 Flow chart for varying conditions (MT) ................................................................................. 90

19 Appendix-B (MT)........................................................................................................................ 91

20 Appendix-C (ALL) ....................................................................................................................... 92

1 Introduction (BP)

With increasing awareness of global warming due to Carbon Dioxide produced from the burning

fuels, the use of natural energy source is coming into effect. Engineers are adapting the use of

natural sources (e.g. wind, solar, hydro) to generate electricity and provide power to the power

plants. The use of wind turbine is one of the oldest known methods of extracting the energy from

natural sources. Windmills were used in olden times to run the pump for pumping the water from

the well. Wind turbines are not well considered because they heavily depend on the wind blowing

along with the geographical disturbance however, a small scale wind turbine can be used to power

small home appliances reducing the cost of electricity and fuel burnt to produce equal amount of

electricity.

Wind turbine extracts energy from the wind to generate electricity. 40% of all the wind energy in

Europe blows over the UK, making it an ideal country for domestic turbines (known as 'microwind' or

'small-wind' turbines). A typical system in an exposed site could easily generate more power than

household lamps and other electrical appliances use. Just like any engineering design poses

challenges, household wind turbine also poses various challenges such as noise, aesthetics, buying

cost, maintenance cost, etc.

This report looks into the current designs of the small scale wind turbine along with the market

requirement followed by the design of an innovative wind turbine system. In the report areas such as

current designs, power generation, blade design power management and fail safe methods are

considered. The report also considers the development complications limiting the design

enhancement such as noise, aesthetics, material cost, maintenance, legal constraints and other

issues. These are the issue which affect the design, manufacturing and marketing of the product.

1.1 Aim The main aim of the project is to design a small wind turbine that can generate electricity for home

appliances. The thought of design directs us to look into the various aspects such as manufacturing,

noise, cost which leads us to our additional aim of analysing the system to overcome the usual

technical glitches.

1.2 Design Brief The project brief involves the design of a small scale wind turbine that can be easily mass produced

and fitted to every household in the UK to aid electricity consumption. The design should provide the

following;

1. Be able to generate a non-trivial electricity supply to the household when operating. Excess

electricity can be fed back into the national grid or charge secondary batteries.

2. The scale of the turbine should be within the limits of the UK building code and not dominate

the aesthetics of the average dwelling.

3. Designed to operate at suitable wind speeds typical to UK weather in urban environments.

4. Possess a fail-safe system as a consequence of an over-speed event.

5. Have a low acoustic footprint.

The above brief for this project can be simplified further to manage the project. Simplified brief

below shows that this project provides us with an opportunity to look into various sections which will

help us complete the task. The several tasks to be completed for this project are as follows:

• Evaluation of the working environment for the turbine in the UK – wind speeds, weather, etc.

• Calculation of the aerodynamic design and structural loads

• Selection of the materials & equipme

• Investigation of mass production methods

• Cost/Benefit analysis of the system

• Considerations for safety system during extreme events

• Noise reduction methods and its implementation into design

2 Current Designs (KE)

2.1 Energy ball V200

Energy ball V200 (SeeFigure 1) is a unique turbine design when compared to the traditional three

blade wind turbines. The design consists of six rotor blades that are asse

The turbine weights 90kg, turbine diameter of 1.98m and minimum start up wind speed of 3 m/s.

Due to the unique design and the venture effect, the generator harness wind more efficiently. The

electricity generated from V200

the electric socket (Plug-in product) of the property. The Inverter is connected to the property

electric breaker box. The energy harvest from V200 can be used to charge batteries and excess

unused energy automatically dumped in to the grid. The Energy ball categorised as a noise less, since

the turbine does not have any wing tips it does not generate the ‘’swishing’’ noise. The Energy ball’s

dimensions allow it to be installed in many countrie

vibration (noise less) and less shadows it ideally suited for residential or commercial rood top usage.

Figure 90 shows the power curve of the Energy ball V200 which shows the turbines operating

parameters (1).

2.2 Honeywell WT6500 Wind Turbine

Selection of the materials & equipment – battery, metal, coils, etc.

Investigation of mass production methods

Cost/Benefit analysis of the system – power generated and its cost effective use

y system during extreme events

reduction methods and its implementation into design

(KE)

Figure 1: Energy Ball V200

) is a unique turbine design when compared to the traditional three

blade wind turbines. The design consists of six rotor blades that are assembled as a sphere shape.



electricity generated from V200 Energy ball comes to direct use where it can be plugged in straight to

in product) of the property. The Inverter is connected to the property


nused energy automatically dumped in to the grid. The Energy ball categorised as a noise less, since


dimensions allow it to be installed in many countries urban areas. Also it features such as less


shows the power curve of the Energy ball V200 which shows the turbines operating

WT6500 Wind Turbine

Figure 2: Honeywell WT6500

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ted and its cost effective use

) is a unique turbine design when compared to the traditional three

mbled as a sphere shape.



ball comes to direct use where it can be plugged in straight to

in product) of the property. The Inverter is connected to the property


nused energy automatically dumped in to the grid. The Energy ball categorised as a noise less, since


s urban areas. Also it features such as less


shows the power curve of the Energy ball V200 which shows the turbines operating

The Honeywell Wind Turbine (see

weight of 110 kg and generates on average up to 1500 kWh per year depending on height and

location. The Honeywell Wind Turbine’s blad

and the unique multi - stage blade design enables the system to react quickly and efficiently to

change in wind a speed which ensures that the maximum wind energy is captured without the typical

noise and vibration associated with traditional wind turbines. The Wind Turbine has an increased

operating span over traditional turbines with a start

auto shut off at 38 mph (17.0 m/s).

2.3 Hannevind 2.2 kW

The Hannevind wind turbine (see

glass fiber. Since the diameter of the turbine is 3.5 meters it required to a

The tower can be high between 12 to 18 meters and it weight around 100 kg. The turbine operates at

minimum wind speed of 2.4 m/s and the maximum power is generates at the wind speed of 9 m/s. At

the rear end of the turbine there i

wind for capture as much wind energy as possible. The turbine can be connected to the electric grid,

work solo or be connected with some other kind of electric device

2.4 Windon 2 kW The Windon 2kW (SeeFigure 4) is a turbine which has three blades with a diameter of 3.2 meters.

Back on the turbine is a fin, which helps the turbine to steer up against the wind so that maximum

effect can be received. The tower can be 9 or 12 meters high, and the weight of the turbine is

approximately 40 kg. The minimum wind for the turbine to start generate electricity is 2.5 m/s. The

wind turbine is very quiet and demands very little service and maintenance.

turbine power curve (4).

The Honeywell Wind Turbine (seeFigure 2) is a gearless wind turbine, which the diameter of 1.8 m,


location. The Honeywell Wind Turbine’s blade tip power system (BTPS) is a perimeter power system

stage blade design enables the system to react quickly and efficiently to


nd vibration associated with traditional wind turbines. The Wind Turbine has an increased

operating span over traditional turbines with a start-up speed as low as 0.5 mph (0.2 m/s), with an

auto shut off at 38 mph (17.0 m/s). Figure 91shows the power curve for WT600 (2)

Hannevind 2.2 kW

Figure 3: Hannevind Wind Turbine

(seeFigure 3) equipped with typical classic look of three blades made of

glass fiber. Since the diameter of the turbine is 3.5 meters it required to acquire a building permit.



the rear end of the turbine there is a fin mounted which helps it to steer the turbine up towards the


work solo or be connected with some other kind of electric device (3).

) is a turbine which has three blades with a diameter of 3.2 meters.


The tower can be 9 or 12 meters high, and the weight of the turbine is


wind turbine is very quiet and demands very little service and maintenance.

Figure 4: Windon Wind Turbine

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) is a gearless wind turbine, which the diameter of 1.8 m,


e tip power system (BTPS) is a perimeter power system

stage blade design enables the system to react quickly and efficiently to


nd vibration associated with traditional wind turbines. The Wind Turbine has an increased

up speed as low as 0.5 mph (0.2 m/s), with an

(2).

) equipped with typical classic look of three blades made of

cquire a building permit.



s a fin mounted which helps it to steer the turbine up towards the


) is a turbine which has three blades with a diameter of 3.2 meters.


The tower can be 9 or 12 meters high, and the weight of the turbine is


wind turbine is very quiet and demands very little service and maintenance. Figure 92 shows the

2.5 Bergey Excel

The Bergey Excel (See Figure 5

operation in adverse weather conditions. When connec

the electricity for an average total electric home at moderate wind sites.

Start-up Wind speed at 7.5 mph and

battery charging. The Estimated Energy Production of

12.5mph (5).

2.6 Southwest Windpower Skystream 3.7The Skystream 3.7(See Figure 6) is designed for residential use which is the first fully integrated and

grid-tied wind energy system designed for that purposes.

inclusive wind generator with controls and inverter built in designed to provide quiet, clean

electricity in very low wind speeds. The Skystream 3.7 operates to downwind because it has no tail

rudder to keep it facing into the w

outputs and peak capacity of 2.6 kW. The Start

The interconnection can be either

and a brushless permanent magnet. The turbine generates total

estimated energy production of

2.7 Windsave WS500 The Windsave WS500 (See Figure

Windsave WS 1000 is 1.75 m in diameter and rated at 1000 W at 12 m/s. Both these ratings imply a

Figure 5: Bergey Excel

5) is designed for high reliability, low maintenance and automatic

operation in adverse weather conditions. When connected to the grid the turbine provide most of

the electricity for an average total electric home at moderate wind sites. Rated Capacity of

7.5 mph and rotor size of 6.7 m, Interconnection can be

Estimated Energy Production of 1500 KWh per month at a wind speed of

Southwest Windpower Skystream 3.7 ) is designed for residential use which is the first fully integrated and

tied wind energy system designed for that purposes. This ‘plug and play



rudder to keep it facing into the wind. The turbine has a Rated Capacity of

outputs and peak capacity of 2.6 kW. The Start-up wind speed of 8mph and the r

can be either utility connected or battery charging. It has a gear less

brushless permanent magnet. The turbine generates total voltage output of

estimated energy production of 400 kWh per month at wind speed of 5.4 m/s (6)

Figure 6: Skystream 3.7

Figure 7) is 1.25 m in diameter and rated at 500 W at 12 m/s and the


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) is designed for high reliability, low maintenance and automatic

ted to the grid the turbine provide most of

Rated Capacity of 10kw,

Interconnection can be Utility connected or

1500 KWh per month at a wind speed of

) is designed for residential use which is the first fully integrated and

and play’ turbine is an all-



Rated Capacity of 1.9 kW continuous

8mph and the rotor size of 3.72m.

utility connected or battery charging. It has a gear less alternator

voltage output of 240 VAC and

(6).

) is 1.25 m in diameter and rated at 500 W at 12 m/s and the


coefficient of performance (power

which would be an extremely good performance for a micro wind turbine, which, at that size, might

have been more expected to have maximum coefficient of performance between 0.11 and 0.19

2.8 Renewable Devices The Swift turbine (SeeFigure 8) has a blade diameter of 1.8 meters and start in wind speed at 4 m/s.

The turbine rated output power of 2200W and output voltage of 120V. The design en

Renewable Devices claim that it is the world’s first truly silent wind turbine. The Swift has some very

advanced aerodynamics that make the rotor more efficient, whilst reducing the noise emissions

significantly, a problem which has meant that s

circular rim around the outside of the blades restricts the radial flow of air at the tip of each blade

that creates a ripping noise with conventional turbines. Renewable Devices has also developed an

electronic control system that safeguards the turbine in high winds and ensures efficient power

extraction under normal operating conditions

3 The Wind (BP)

3.1 Geographical AnalysisWind turbine generates electricity by extracting energy from the wind. Earth’s circulation system,

driven by its magnetic poles and the temperature gradient (across its latitude), sets the wind

direction and its speed. It gets affected by the landscape, the geometry and the speed it’s flowing

across or around. Flowing with unique characteristics, the wind carries energy of th

be used to generate lift or drag force

show how the wind gets affected by the general landscape aided by the data of UK Mean Wind

Speed.

coefficient of performance (power produced by turbine divided by power in the wind) of about 0.38,


have been more expected to have maximum coefficient of performance between 0.11 and 0.19

Figure 7: Windsave

Renewable Devices – Swift ) has a blade diameter of 1.8 meters and start in wind speed at 4 m/s.

The turbine rated output power of 2200W and output voltage of 120V. The design en



significantly, a problem which has meant that similar sized turbines cannot be building mounted. A



ctronic control system that safeguards the turbine in high winds and ensures efficient power

extraction under normal operating conditions (8).

Figure 8: Swift

Geographical Analysis Wind turbine generates electricity by extracting energy from the wind. Earth’s circulation system,

poles and the temperature gradient (across its latitude), sets the wind


across or around. Flowing with unique characteristics, the wind carries energy of th

force as a result of a pressure difference. The following paragraph will


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produced by turbine divided by power in the wind) of about 0.38,


have been more expected to have maximum coefficient of performance between 0.11 and 0.19 (7).

) has a blade diameter of 1.8 meters and start in wind speed at 4 m/s.

The turbine rated output power of 2200W and output voltage of 120V. The design engineers of



imilar sized turbines cannot be building mounted. A



ctronic control system that safeguards the turbine in high winds and ensures efficient power

Wind turbine generates electricity by extracting energy from the wind. Earth’s circulation system,

poles and the temperature gradient (across its latitude), sets the wind


across or around. Flowing with unique characteristics, the wind carries energy of the form which can

as a result of a pressure difference. The following paragraph will


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Figure 9: Microscale modelling around Wellington (9)

Wind flowing over various landscapes can get affected by its geometrical appearance. Figure 9shows

a classic example of how the wind gets affected by the landscape. It shows graphical presentation of

the CFD simulation carried for a micro scale model over the Wellington area.The wind cannot be

seen in real life but can be visualised as stream of particles flowing in a line (either straight or random

chaotic line). Figure 10&Figure 11shows animated behaviour of the wind flow over the mountain and

the cliff.

Figure 10: Wind Flow near the Cliff (10)

Figure 11: Wind Flow over the Hill (10)

The purpose of this analysis is to show that the undisturbed flow of air is mostly uniform.However

when it flows around or across a geometry or a landscape, it creates turbulence. This turbulent

air/wind includes random movement of the air particles which leads to loss of energy the wind

contains. Therefore wind turbine needs to be placed on a landscape that places rotor and blades in

average wind flow but with little of turbulence created by the surroundings.

Artificial or natural surroundings can potentially create turbulence. Artificial surroundings include the

houses and buildings. Figure 12&Figure 13 shows CFD Analysis carried out by S J Watson at

Loughborough University. Figure 12displays filled vector plot of a house in isolated area and how

wind (flowing from left to right) creates wake resulting in no or low velocity with a change in

direction. Figure 13displays a filled vector plot of a house in urban area which shows wind flow (left

to right). In urban area there is only small amount of wind flowing below the roof tops and because

of this, minimum turbulence is created before and aft of house.

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Figure 12: CFD Analysis of Wind Flow - Isolated Area (11)

Figure 13: CFD Analysis of Wind Flow - Urban area (11)

The wind analysis of different landscape and geometrical obstacles suggest that the wind turbine

needs to be placed in open area where landscape does not create wake. If the turbine is to be placed

on top of a house roof, it needs to be place on the upwind side of the roof as downwind side has high

turbulence close to the roof. If the wind turbine is to be placed near the cliff top or on mountain, it

needs to be high above the ground as the turbulence is high near to the terrain. However at very high

level from ground, wind speed is not high therefore a balance must be found by collecting data over

certain period of time at different height scales.

3.2 UK Historical Data Weather changes with time bringing in new seasons with different climate conditions. The Met office

provides us with some average data on Mean Wind Speed measured at various regions in UK. This

data will help us identify the wind speed limit we are expected to incorporate while designing small

scale wind turbine for home electricity.

e Figure 14: Mean Wind Speed 1971-2000 Spring (12)

Figure 15: Mean Wind Speed 1971-2000 Summer (12)

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Figure 16: Mean Wind Speed 1971-2000 Autumn (12)

Figure 17: Mean Wind Speed 1971-2000 Winter (12)

The data above clearly shows that the mean wind speed varies between 6-25 m/s at various regions

in UK. Climate conditions also play important role in wind speeds as seen from the figures above. In

summer, the wind speed measured in most urban areas is below 10 m/s and towards the Scotland

side it picks up to 25 m/s. however in winter, the urban areas experience wind speed of 10-15 m/s

and areas in Scotland and North Wales experience wind speed greater than 25 m/s. some part in

changing wind speed. Therefore if the small wind turbine is to be designed for UK households, then it

should be able to work at speeds low as 3-6 m/s and should also be able to sustain high wind speeds

of around 25 m/s.

4 The Wind &the Blades

4.1 Wind power calculations Kinetic Energy of a mass in motion is given by

� = 12��

Equation 1: Kinetic Energy

But the power is the rate of change of energy:

� = �

Equation 2: Power

If the kinetic energy of the wind is considered to have constant velocity then the power of the wind

can be calculated by

� = �� , where

� �� = ��

��

Therefore,

� = 12��

Equation 3: Wind Power (13)

Whereρ is the Density, A is the Sweap Area and v is the Velocity of the wind.

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Figure 18: Wind Turbine Sweap Area (13)

The above calculation only helps us to find out the wind power with specific wind velocity. The wind

turbine however does not extract all the power from the wind. Some of the energy is used to

overcome the profile drag (14) created by the blade geometry and the leftover energy is allowed to

pass through as extracting all the energy from the wind would mean accumulation of static pressure

particles aft of wind turbine blades. Imagine an ‘Axial Stream Tube’ around a wind turbine as shown

in Figure 19; if the energy is extracted between stage 2 and 3, the pressure accumulation would

divert the incoming flow around the blade rather than passing through the blades. By extracting the

power, the turbine reduces the wind kinetic energy. Therefore the air moves more slowly

downstream of turbine compare to the upstream. This accumulates wind behind the turbine sweap

area (downstream) as its moving slowly after the energy extraction. As a result the approaching

(upstream) wind diverts around the turbine blades to avoid slow moving air. For these very reason

‘there is an optimum amount of power to extract from a given disc diameter’ (15). ‘The ideal is to

reduce the wind speed by about two thirds downwind of the turbine, though even then the wind just

before the turbine will have lost about a third of its speed. This allows a theoretical maximum of 59%

of the wind’s power to be captured (this is called Betz’s limit)’ (15).

Figure 19: Axial Stream Tube around a Wind Turbine (16)

So by taking the Betz’s limit in consideration, the power available from the wind is given by the

formula below where η is the Betz’s limit (generally given by ��ratio).

� = 12��

Equation 4: Power Available

Even after applying the Betz’s limit, the wind contains energy enough to drive the blades &generator

and produce electricity. However, it depends on the blade design and its efficiency across the span to

determine how much energy is extracted. While talking efficiency, we are faced by various design

&mechanical limitations, therefore design of the blades will be considered even further in the next

section as the blades play keep role in extracting the energy from the wind.

9 | P a g e

4.2 The Blades Starting from design needs, considering manufacturing & materials’ limit and finishing with the

power efficiency, the wind turbine blades are shaped to generate the maximum power from the

wind

The design engineers have to consider the following while designing the turbine blade:

• Number of Blades

• Aerofoil & Load

• Materials

• Rotational Speed

• Wind speed

• Pitch Control

4.2.1 Number of Blades Betz’s limit places significant restriction on the power that can be extracted by the blades. The

limitation means more blades there are, the less power each can extract. However this allows us to

reduce the blade length (span) and chord. ‘The other factor influencing the number of blades is

aesthetics: it is generally accepted that three-bladed turbines are less visually disturbing than one or

two-bladed designs’ (15). Also the number of blades adds to the weight which creates moment about

the centre (mast or pillar). This moment is counter acted by the moment generated by the weight of

the tail fin. Therefore increasing the number of blades would also require increasing the weight of

the tail fin by changing the geometry or the distance its acting at from the centre or by using a denser

material for the tail fin. Blades generate lift and this lift providesacceleration for the angular rotation.

Hence the reason blades need to be manufactured precisely and increasing the number of blades

would increase the cost of manufacturing.

4.2.2 Aerofoil & Load The turbine blades extract energy from the wind by using wind energy to generate the lift force. It

uses same concept as the aeroplane wing in order to generate the lift force.

� = 12��

Equation 5: Finite Wing Lift Equation

The equation above shows the finite wing lift equation which uses the finite wing CL value to work

out the lift. If we look at the cross section of the wind turbine blade at particular point, we would see

an airfoil shape. Air flowing over an airfoil shape generates lift due to the pressure difference. The

best lift/drag characteristics are obtained by an airfoil that has thickness approximately 10-15% of its

chord length (15). The lift can be increased by increasing the angle of attack but it also increases drag

and potential of flow separation (Figure 21). For a particular airfoil shape coefficient of lift to angle of

attack graph (Figure 22) is used to best describe the relation between lift and the angle of attack.

Figure 20: Lift and Drag Vectors (15)

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Figure 21: Aerofoil Shape & the Angle of Attack (15)

Figure 22: Typical CL Graph (14)

The figure above shows the graph for Infinite and Finite Wing Coefficient of lift where infinite wing

curve is mostly based on experimental and computation analysis and finite wing lift can be worked

using the following formula:

�� = ��1 + ��.� !�"#$%

Equation 6: Finite Wing CL Gradient (14)

Where CLα is the finite wing coefficient of lift curve gradient worked using infinite wing coefficient of

lift curve gradient (Clα), aspect ratio (AR) and the span efficiency factor (e). Using this equation the

coefficient of the lift and the lift itself can be worked out for a blade design however, the drag affects

needs to be considered. The drag force on wind turbine blade is used to rotate the blades for VAWT

but for HAWT it adds to the loss of energy from the wind and also adds to the structural load applied

to the blade and the whole system. Drag force acting on the blade is given by the following equation:

& =12�'��

Equation 7: Finite Wing Drag Force

Where CD is:

�' = �� + ��()�*

Equation 8: Finite Wing Drag Coefficient(14)

The above equation uses finite wing coefficient of lift value along with the aspect ration, span

efficiency factor and airfoil profile drag (skin friction drag + pressure drag) to calculate the Finite

11 | P a g e

Wing Drag. With the method of calculating the lift and drag for wind turbine blade, the design of the

blade can be altered to maximize its efficiency.

To improve the blade efficiency, the blade thick needs to be reduced relative to its width and this has

effect on the aerofoil shape and the loading of the material. Also the apparent wind, wind blowing at

an angle (Figure 23), ‘rotates the angles of the lift and drag to reduce the effect of lift force pulling

the blade round and increase the effect of drag slowing it down. It also means that the lift force

contributes to the thrust on the rotor’ (15). Hence the reason the blade needs to be turned further at

the tips than at the roots, approximately around 10-20°.

Figure 23: Apparent Wind Angle (15)

As mentioned earlier, the best lift/drag characteristics are obtained by an aerofoil that has thickness

approximately 10-15% of its chord length. However the due to structural requirements, the blade

needs to support the lift, drag and gravitational forces acting on it, the aerofoil needs to be thicker

than the aerodynamic optimum. The blade needs to be even thicker towards the root (where the

blade attaches to the hub) where the bending forces are greatest. Because the apparent wind is

moving slowly near to the roots (Figure 24), the need of aerodynamic efficiency is low. In which case

some designers use a “flatback” section (Figure 25) closer to the roots as it gives high structural

strength at the root attachment area but the attention needs to made as the section cannot get too

thick for its chord length or the air flow will separate.

Figure 24: Apparent Wind across the Blade(15)

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Figure 25: Flatback Section (15)

4.2.3 Materials To maintain optimum solidity and high aerodynamic efficiency, thickness of the blade is

compromised. This makes it difficult to build the strong blades as thin material can flutter and

fracture eventually. To build a strong blade, material such as Pre-Preg carbon can be used which is

stiffer and stronger then glass fibre but drives the cost of material high. For a small scale wind

turbine blade material; aluminium alloy, iron, wood or strong plastic are more suitable due to its low

cost of manufacturing compared to carbon fibre (blade aerofoil shape does affect the manufacturing

cost).

4.2.4 Wind Speed The wind speed is also taken into consideration when design the turbine blade. The wind speed sets

the Reynolds Number given by:

*) = �+,-

Equation 9: Reynolds Number for flow around Turbine Blade

where u is the wind speed velocity, c is the blade chord length and µ is the dynamic viscosity of the

fluid (air in this case). If the Reynolds number is high the stall coefficient of lift value for a particular

airfoil shape is also higher (Figure 27), therefore more leverage in the angle of attack. High Reynolds

number also reduces the drag for given angle of attack (Figure 26).

Figure 26: NACA 0010 Cd Graph

Figure 27: NACA 0010 Cl Graph

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4.2.5 Angle of Attack The blade pitch is controlled to attain correct angle of attack for maximizing the lift; however the

same feature can be used for safety purposes. During adverse weather condition, the blades’ angle

of attack can be reduced to zero so that it generates no lift. The process is known as “featuring” as

the blades allow wind to simply pass through without extracting energy from it (except the energy

required to overcome the drag affects while passing over the blade).

4.3 Power Extracted

Earlier we looked into the power available from the wind however, it is important to calculate how

much available power is extracted by the turbine blade design to review its efficiency.

Once the lift and Drag force is calculated for a given airfoil (blade cross section), experimental or

computational analysis can be carried out to measure the angular velocity. Alternatively, lift and drag

force can be used along with the measure RMP to work out the angular velocity and other forces

acting on the blade.

With the calculated values the power extracted by the wind turbine blade can be worked out using

the following equation: � = ./ Equation 10: Power Extracted

Where ω is the angular velocity and T is the torque given by:

. = 0 × 2 Equation 11: Torque

F = force, r= radius from the centre point to where the force is acting

Therefore the efficiency of the wind turbine can be determined by dividing the Power extracted (PR)

by the Power Available (P):

�3 = �%�

Equation 12: Coefficient of Performance(17)

The efficiency of the turbine gives us good idea on how where the turbine needs to be altered to

improve the coefficient of performance but with the improvement comes’ the cost of manufacturing

and maintenance. The wind turbine also ends up losing some efficiency to overcome the frictional

affects and some energy is lost as heat and noise.

4.4 Acoustics & Insulation Although the energy lost in noise, heat, etc. is minor compare to the energy lost due to blade

inefficiency but reducing the other losses would still improve turbines efficiency. The few major

losses that are involved in most wind turbine designs are:

• Frictional affects on rotating centre

• Gear frictional losses

• Drag force on the blades

All the losses stated above either result into noise or heat transfer. As the small wind turbine can be

placed on house roof top or building roof top, the constant noise from the rotating turbine blades

would upset the house or building inhabitants.

The noise from the mechanical rotating parts can be reduced by lubricating the parts however

maintenance of these parts is expensive and difficult if the wind turbine is mounted on roof top or

high mast. Blade rotating through air also produces noise which

the turbine blades in a cylindrical diffuser built with high acoustic material e.g.

parts and blades are not the only source of noise but the electrical generator also emits noise when

wire is turning in the magnetic flux area or when high voltage current is passing through the coils.

This situation not only emits noise but also transfers heat to the surroundings reducing the overall

efficiency of the turbine. To summarise, properly insulating the wire

the turbine and lubricating the mechanical system regularly keeps the turbine efficiency high but the

maintenance cost increases.

5 Generator (KE) Torque is transferred from the rotor through a connectin

electricity. The shaft is either directly connected or is connected t

linked to the generator. Gearbox is placed to increase the rotational speed if the rotor is not turning

fast enough for the generator to produce high frequency electricity.

incorporate changing gear system managed by the controlled feedback system

the gear depending on the rotor speed to keep the generator speed constant.

placed at the top of the tower or at the base (connect by the gears) for HAWT and at the base for

VAWT. An electrical generator

torque transferred by the rotor is used to rotate

5.1 AC & DC GeneratorAn electrical generator is a device, which converts mechanica

generator produces direct current. In a DC generator an e.m.f is induced whenever magnetic flux is

cut by a conductorFigure 28: DC Generator

rotating in a uniform magnetic field provided by permanent magnets or

the coil are connected to two slip rings R

brushes are pressed against the slip rings. The current is

cuts the magnetic flux between two magnets according to Fleming’s right hand rule. However the

current is alternating as coil is turning (cutti

rings (insulted from each other),

reasons we have direct current.

slip rings that are always in contact with the brushes. Therefore when

alternates (as it cuts the flux in

brushes also alternates. Hence the reasons we have alternating current.

Figure 28: DC Generator (18)



high mast. Blade rotating through air also produces noise which can only be reduced by containing

the turbine blades in a cylindrical diffuser built with high acoustic material e.g. foam. The mechanical


in the magnetic flux area or when high voltage current is passing through the coils.


efficiency of the turbine. To summarise, properly insulating the wires, placing the acoustics around


Torque is transferred from the rotor through a connecting shaft to the genera

electricity. The shaft is either directly connected or is connected through the gearbox which then is


to produce high frequency electricity. Some wind turbine

incorporate changing gear system managed by the controlled feedback system, i.e. it would change

the gear depending on the rotor speed to keep the generator speed constant.


An electrical generator is used to convert mechanical energy into electrical energy.

is used to rotate acoil of wire or a magnet to generate electricity.

AC & DC Generator An electrical generator is a device, which converts mechanical energy into electrical energy.


: DC Generator (Figure 28). Figure below shows a copper conductor loop

rotating in a uniform magnetic field provided by permanent magnets or electromagnets.

the coil are connected to two slip rings R1 and R2 which are insulated from each other. Two collecting

brushes are pressed against the slip rings. The current is induced in the coil ABCD when it rotates and

between two magnets according to Fleming’s right hand rule. However the

current is alternating as coil is turning (cutting the flux in two directions), but because of the split slip

(insulted from each other), the current passed to the brushes is always direct

For the AC generator, the coil is connected to the individual circular

slip rings that are always in contact with the brushes. Therefore when the current in the coil

alternates (as it cuts the flux in two direction due to its circular motion), the current passed to the

brushes also alternates. Hence the reasons we have alternating current.

(18)

Figure 29: AC Generator

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can only be reduced by containing

foam. The mechanical


in the magnetic flux area or when high voltage current is passing through the coils.


s, placing the acoustics around


g shaft to the generator which generates

gearbox which then is


Some wind turbine would also

, i.e. it would change

the gear depending on the rotor speed to keep the generator speed constant.Generators can be


convert mechanical energy into electrical energy. The

re or a magnet to generate electricity.

l energy into electrical energy. DC


Figure below shows a copper conductor loop

electromagnets. Two ends of

which are insulated from each other. Two collecting

in the coil ABCD when it rotates and

between two magnets according to Fleming’s right hand rule. However the

ecause of the split slip

lways direct. Hence the

For the AC generator, the coil is connected to the individual circular

the current in the coil

two direction due to its circular motion), the current passed to the

: AC Generator (19)

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5.2 InductionGenerator Electricity can also be generated by rotating magnet and fix stator with coils to induce current in.

Induction generator uses principle from induction motor where the wind turbine rotor blades are

connected to the magnet that rotates between a stator with coils wounded around the stator. When

the magnet rotates it creates flux in the stator which cuts the coils and generates voltage (Figure 30).

The magnet then turns to change the magnetic field and the flux direction which sets the scenario for

changing flux between fixed coils resulting in alternative current produced.

Figure 30: Induction Generator (20)

5.3 Generator types

5.3.1 Synchronous Generator (SG) The synchronous machine uses separately excited windings in the rotor in order to excite the

magnetic field in the rotor. Separate excited windings give the possibility to change the output

voltage by adjusting the excitation of the magnetic field of the rotor. Since the stator windings do not

have to carry the power to excite the rotor magnetic field, a reduction in mass of the active

materials, over the IM (induction motor), is possible. Another advantage over the IM is that smaller

power handling equipment, like converters, can be used to control the SG (21).

Figure 31: Synchronous Generator

5.3.2 Permanent magnet synchronous Generator (PMSG) When the separate excitation of the synchronous generator is done by permanent magnets (PM’s)

instead of windings, the machine is called a permanent magnet synchronous generator. No power is

lost to excite the rotor magnetic field through windings and efficiency will increase compared to the

SG. Also a weight reduction can be made over the SG. Since the rotor construction of the PMSG is

smaller than the rotor construction of a SG made with excitation windings .The cost reduction of a

PMSG over a SG will not be proportional with the reduction in mass, since PM material is much more

expensive than copper and steel used in SG rotor constructions. However the total costs for a PMSG

are lower than for a SG(21).

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Figure 32: PMSG

5.3.3 Switched reluctance generator (SRG) In a switched reluctance machine only the stator windings are excited and produce a magnetic field.

The rotor is constructed in such a manner that by moving it, the rotor causes a change of stored

magnetic energy in the machine. By sequentially exciting the stator coils the torque can be produced

or electricity can be generated. The benefits of the SRG lie in a simple and low cost and rigid

construction. However as with an IM the SRG draws its excitation magnetic field from the power

source, therefore larger converters are needed to operate a SRM. For equal efficiencies the SRG

construction appears to be more compact and slightly lighter than the IM construction(21).

Figure 33: SRG

5.4 Permanent magnet generators Small scale wind power requires a cost effective and mechanically simple generator in order to be

reliable energy source. The use of direct driven generators instead of geared machines reduces the

number of drive components, which offers the opportunity to reduce the number of drive

components. Also it offers the opportunity to reduce the costs and increase system reliability and

efficiency. For such applications, characterized by low speed is particularly situated, since it can be

design with a large pole number and high torque density. The most efficient type of generators

matching the above criteria is the permanent magnet generators. So the group have decided to

consider permanent magnet generators for the design(21).

The permanent magnet synchronous generators are constructed in different ways. Two design

characteristics of a construction type are:

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• The orientation of the magnetic flux within the machine.

• The type of rotor construction with permanent magnets.

5.4.1 The magnetic flux orientation (Radial Flux or Axial Flux) Air gap orientation can be identified in two different ways. The radial flux design magnetic field is

given a radial direction by mounting the stator around the rotor. Figure 34 shows the cross sectional

view in radial direction and in axial direction. The axial flux design (See Figure 35) is constructed by

placing stator and rotor in a way that the air gap is perpendicular to the rotational axis, where the

magnetic flux crosses the air gap is in axial direction. The axial design used in situations where the

machines axial dimension is more limited than the radial dimensions(21).

Figure 34: Cross Sectional View in radial direction and in axial direction

Figure 35: Cross Sectional view in radial direction and in axial direction

5.4.2 Longitudinal or Transversal (Figure 5.4.1)

Figure 36: Transversal Flux PMSG

Transversal flux machines are manufactured by mounting the plane of flux path perpendicular to the

direction of rotor motion. The transversal flux machines can used in applications where required high

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torque density requirements. The transversal flux machines can independently adjust the current

loading and the magnetic loading. The main disadvantage of transverse PMSG is that high leakage

flux results in poor power factor; this can be avoided by reducing the number of poles where in turn

reduces torque density. Another drawback in rotating transverse PMSG is the mechanical

construction is weak due to large number of parts(21).

5.4.3 Inner Rotor or Outer Rotor The common rotor topology is acquired by mounting the PM’s on the rotor surface. This is called a

surface mounted permanent magnet rotor construction. This construction requires to shape the

magnets in a circular arrangement. There are two types of rotor magnetic inner rotor and outer

rotor. The outer rotor machines are constructed by placing the rotor surrounds the stator. The

magnets are mounted on the inner circumference of the rotor. In the outer rotor machine the rotor

has higher radius compared with the stator and it can be equipped with higher number of poles for

the same pole pitch. Another advantage is that the magnets are well supported despite the

centrifugal force also a better cooling of magnets is provided. Figure 37 shows an inner rotor PMSG

and an outer rotor PMSG(21).

Figure 37: Inner rotor PMSG (left) and an outer rotor PMSG (right) (ref3)

5.5 Coil winding arrangements Winding arrangement determines the way the coils are arranged. Coil can either have an air gap or

they can be placed in slots around the teeth in the stator. Density of coil taps is a choice between

higher amounts of coils placed densely in one place or lower number of taps placed around the

device. When and design with number of slots is considered, the choice or number of poles and coils

is a choice(21).

5.5.1 Coil placement

Figure 38: Slotless Design

Slotless design is where the coil is placed in the air gap. This air gap increases the distance between

stator and the rotor increasing the reluctance causing increase in PM (Permanent Magnet) leading to

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a reduction in flux density. More magnetic material or copper winding are needed to compensate

this. A slotless design has less steel and therefore less hysteresis and Eddy current losses. The power

density of a slotless design is three times lower than in a slotted design(21).

5.5.2 Coil winding distribution In a slotted stator, the stator windings can be placed as concentrated coils around the teeth or the

windings can be distributed in the slots. Concentrated coil constructions have the advantage of a

higher winding factor; this increases the amplitude of the induced output voltage. Less copper is

required due to shorter end windings. They are also easier to manufacture through modern

automated techniques. The disadvantage of concentrated coil windings is the increase of harmonic

components in the air gap flux. This causes an increase of losses in the rotor magnets and back iron

due to Eddy currents(21).

5.5.3 Pole slot combinations The number of stator slots (Ns) and the number of magnet poles (Nm) that can be used in an electrical

machine design are countless. For a 3 phase machine using concentrated coils, the number of

combinations (Ns and Nm) is still large. Therefore the choice of slot pole arrangements has to be

made by considering different slot pole combinations. The combination of 3 coils around 3 teeth with

2 magnet poles creates the lowest Eddy current losses in the magnets and rotor back iron; however

this combination has a poor winding factor. Low rotor Eddy currents cause less temperature rise in

the magnets, which will enhance efficiency and decrease the risk of demagnetizing the magnets(21).

6 Advantages and Disadvantages of Wind Turbine Designs

(MT)

As mentioned earlier, a wind turbine extracts the wind power to generate electricity. The blades

extract energy from the moving wind which spins a shaft, which connects to a generator that

supplies an electric current. Today there are two basic types of wind turbines available in the market.

Most commonly used in wind energy systems are the traditional farm styled, horizontal-axis

turbines.Vertical turbine is relatively new design that’s gaining market share rapidly. They both have

their advantages and disadvantages.

6.1 Horizontal Axis Wind Turbines

Figure 39: HAWT

6.1.1 Advantages of Horizontal Axis Wind Turbines

• Variable blade pitch, which gives the turbine blades the optimum angle of attack. Allowing

the angle of attack to be remotely adjusted gives greater control, so the turbine collects the

maximum amount of wind energy for the time of day and season.

20 | P a g e

• The tall towers allow access to stronger wind in sites with wind shear. In some wind shear

sites, every ten meters up, the wind speed can increase by 20% and the power output by

34%.

• High efficiency, since the blades always moves perpendicularly to the wind, receiving power

through the whole rotation. In contrast, all vertical axis wind turbines, and most proposed

airborne wind turbine designs, involve various types of reciprocating actions, requiring

aerofoil surfaces to backtrack against the wind for part of the cycle. Backtracking against the

wind leads to inherently lower efficiency.

6.1.2 Disadvantages of Horizontal Axis Wind Turbines • Taller masts and blades are more difficult to transport and install. Transportation and

installation can now cost 20% of equipment costs.

• Stronger tower construction is required to support the heavy blades, gearbox, and generator.

• Reflections from tall HAWTs may affect side lobes of radar installations creating signal

clutter, although filtering can suppress it.

• Mast height can make them obtrusively visible across large areas, disrupting the appearance

of the landscape and sometimes creating local opposition.

• Downwind variants suffer from fatigue and structural failure caused by turbulence when a

blade passes through the tower’s wind shadow (for this reason, the majority of HAWTs use

an upwind design, with the rotor facing the wind in front of the tower).

• They require an additional yaw control mechanism to turn the blades toward the wind. (22)

6.2 Vertical Axis Wind Turbines

Figure 40: VAWT

An increasing number of progressive organizations are adopting Omni-directional VAWTs because of

their aerodynamic performance advantages with characteristically turbulent and moderate winds in

densely populated urban settings. VAWTs operate quietly, deliver clean electricity directly to the

owner, and can feed excess electricity into the local power grid, which can further reduce the

owner’s energy consumption costs. The use of VAWTs to produce distributed energy also reduces

both the need for unpopular transmission lines and emissions from fossil-fuel-fired generators that

contribute to climate change, and it provides points for LEED certification (Leadership in Energy and

Environmental Design).

Wind flow within urban and suburban environments is turbulent and veering. Increased turbulence

levels yield greater fluctuations in wind speed and direction. Unlike a traditional horizontal axis wind

21 | P a g e

turbine (HAWT), a VAWT rotates around the shaft vertically. VAWTs provide good performance in

urban and suburban environments due to their inherent design characteristics.

6.2.1 Advantages of Vertical Axis Wind Turbines • Ability to effectively capture turbulent winds which are typical in urban settings, especially in

built-up areas.

• No need for a yaw mechanism to face the blade rotor into veering wind directions; VAWTs

therefore have higher efficiency and no orientation parts to maintain.

• Operation at lower rotational speeds, thereby reducing or eliminating turbine vibration and

noise.

• Durability and reliability working in multi-directional wind.

• Easier and less expensive repair and maintenance with generator on rooftops.

• Lower noise and vibration. (23)

6.2.2 Environmental Benefits Noise & Vibration: Although urban settings are inherently noisier than rural areas, an additional noise

can affect a small minority of people. A popular concern with the use of large-scale wind turbines for

power generation is noise. The majority of large HAWT noise is generated from the gearbox and the

aerodynamic noise of the blades. With small-scale VAWT’s, however, a gearbox is not required, and

VAWT blade speeds are much lower than small HAWTs, so noise is also much lower. In a 2007 test by

McMaster University, a small VAWT was tested for noise generation, which revealed that the overall

noise level of the turbine remains below 50 decibel (dB) for all normal operating conditions (the

turbine rarely operated at a wind speed beyond 15 m/s). When this range is converted to the dBA

scale, based upon the average human hearing capability, the level drops to 20 dBA. This is because

the majority of the turbine noise is produced in the infrasound range (frequencies below human

perception), which is quieter than a whisper. Ultimately, the test determined that the noise level

produced by the small VAWT is insignificant and poses no threat to the comfort of nearby persons or

wildlife (24).

6.3 Comparison between Vertical designs Vs. Horizontal designs • A VAWT can receive winds from any direction, this is important in locations where winds Are

turbulent, gusty and constantly changing directions. There is no ‘down-time’ as the rotor

does not have to yaw to face the wind, in addition there are no gyroscopic effects preventing

yaw. The more obstacles (e.g. trees and buildings) in your environment the more turbulent

the wind is likely to be.

• Aerodynamic noise is primarily generated by the fast moving tips of the blades through the

air. A VAWTs tips are much closer to the axis of rotation and therefore moving more slowly

through the air.

• A VAWT for the same swept area has a smaller plan area than a HAWT, making it more space

efficient, an important consideration when siting close or onto buildings

• Loads are more evenly distributed with a VAWT than a HAWT which results in lower vibration

making VAWTs a better option for roof mounts.

VAWTs HAWTs

Effective in laminar winds (1) Yes Yes

Effective in turbid urban winds (2) Yes No

Effective in low mountings Yes Sometimes

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Ground mounting Yes No

Rooftop mounting Yes Sometimes

Table 1: VAWT vs. HAWT

1) Laminar: fluid air flow which occurs in "sheets" parallel to each other.

2) Turbid: flow that changes directions quickly and often and has turbulences. (25)

6.4 Justification for design choice Wind turbine we are designing would be a horizontal axis wind turbine. Even though the vertical axis

wind turbines are efficient they are complex and cost of manufacturing is higher. Also since

horizontal axis wind turbines been around for a long time, finding necessary component from

suppliers is easy and also performance information is readily available.

7 Wind Turbine Power Management (MH) Once the energy from the wind has been harvested through the turbine blades and transmitted

through a generator to produce electricity, a power management system needs to be put in place in

order to ensure its intended purpose is served. This management system would have slight variations

depending on the scale of the wind turbine. However, the intended final aim is to provide adequate

electricity to a household power grid. Figure 41 provides an example of a typical management system

that can be used for a wind turbine.

Figure 41: Wind Turbine Electricity Power Management (26)

Once the electricity generation process has been completed, it is then sent down through wires to a

transformer unit which increases the voltage up to a few 1000 kV depending on the scale of the wind

turbine. The transformer is needed for either on-shore or off-shore wind turbines where the

electricity generated needs to travel a large distance.

Depending on the type of generator used within the turbine, it will produce either AC or DC power.

An inverter is used in order to convert from DC to AC for domestic use. The electricity can now be

connected directly to the national grid network, stored in batteries for future use or connected to a

household mains grid. When connecting to a household main’s grid, another transformer would be

used to reduce the voltage to 120/240 V AC.

A small scale wind turbine to be used for domestic purposes will contain slight variations to be more

suited for the purpose. Figure 42

turbine.

Due to various design and build limitations in small scale wind

needs to be put in place to provide safe power that can be used in a home system. Typically, they do

not have variable pitch rotor blades and due to this, the rotor speed would constantly change

according the change in wind speed. This does not present a favourable situation for the power

management system because the output voltage and frequency provided by the generator is

proportional to the speed of the rotor while the current produced is proportional to the torque on

the rotor shaft.

Once the electricity is generated, it is sent through a rectifier in order to convert the AC current

produced through the generator. This is done because AC constantly changes direction while DC

maintains a single direction, thus making

sent to a Voltage Regulator unit which is used to maintain the voltage at a constant level

independent of the variability presented to the system. This regulator system can also ensure that

the voltage supplied is at the correct frequency and phase.

The system is then taken over by a DC control unit which works in a similar method to an Engine

Control Unit (ECU) in a vehicle. Now that we have a constant voltage supply which is regulated, we

can distribute the electricity using various methods. The electricity could be stored within batteries

for future use. If it is required to be used within a household grid, an inverter would be used to

convert DC to AC which can then be distributed. Another opti

excess electricity back to the national grid which could help recuperate some of the costs of the

system. Such systems however would need to be agreed to by the supplier and considerations would

need to be made if it would be better to store excess electricity within batteries or to sell back to the

grid, where once sold, if the wind turbine does not produce enough electricity, cost of purchasing the

same amount would be higher.

8 Safety Systems for Wind Turbines

A typical wind turbine is designed to operate for a lifespan of around 20 years. Within this period, it

is expected for it to be operated under various weather conditions which can often be unfavourable.

A wind turbine has a design operating condition whi

stopped in order to prevent damage. Therefore various safety systems are put in place to prevent

damage to the turbine or people who are within the vicinity of the turbine.

8.1 Vibration Sensors During adverse weather conditions, vibration of the turbine can be dangerous for the turbine itself

and the parts contained within it. These can range from a very basic mechanical sensor which works

wind turbine to be used for domestic purposes will contain slight variations to be more

42shows a typical system which might be used for a household wind

Figure 42: Small Scale Wind Power (27)

Due to various design and build limitations in small scale wind turbines, a few additional systems



nd speed. This does not present a favourable situation for the power





maintains a single direction, thus making it easier to regulate. Once this current is converted, it is



oltage supplied is at the correct frequency and phase.



stribute the electricity using various methods. The electricity could be stored within batteries


convert DC to AC which can then be distributed. Another option available for home owners is to sell



would be better to store excess electricity within batteries or to sell back to the


Safety Systems for Wind Turbines (MH)



A wind turbine has a design operating condition which once exceeded, would require it to be


damage to the turbine or people who are within the vicinity of the turbine.

conditions, vibration of the turbine can be dangerous for the turbine itself


23 | P a g e

wind turbine to be used for domestic purposes will contain slight variations to be more

a typical system which might be used for a household wind

turbines, a few additional systems



nd speed. This does not present a favourable situation for the power





it easier to regulate. Once this current is converted, it is





stribute the electricity using various methods. The electricity could be stored within batteries


on available for home owners is to sell



would be better to store excess electricity within batteries or to sell back to the




ch once exceeded, would require it to be


conditions, vibration of the turbine can be dangerous for the turbine itself


24 | P a g e

by having a ball resting on a ring where the ball is connected to a switch through a chain. If vibrations

reach an excessive limit (which can bet set at a required amount), the ball will fall out of the ring

which would enable to switch to turn off the turbine. Advanced electronic sensors which are

connected to the electronic control system of the turbine could also be employed to monitor

vibration levels.

8.2 Turbine over-speed Since the turbine blades would rotate faster with increasing wind speed, it has a safe limit of

operation. This limit is set to ensure there would be no blade failure and also protects the

components within the nacelle such as generators and gearboxes from overheating and eventual

failure. Modern wind turbines are equipped with variable pitch controlled blades where the optimum

pitch is constantly selected in order to gain the maximum power output. In an event of high wind

speeds, the pitch control would turn the rotor blades 90 degrees (aerodynamic braking). This creates

an aerodynamic effect which gently brings the turbine to a stop within a few rotations. The major

advantage of this system is that it does not present major stress factors on the system and once the

high wind speeds are over, the pitch control will take over once again to make the rotor turn.

A mechanical braking system is kept in place as a backup to the aerodynamic braking system when

required. This system is similar to the disc brake system used within cars where a disc rotates with

the shaft and a brake pad is activated in case it is necessary to stop. This system can also be used as a

parking brake when maintenance is needed.

8.3 Thermal and other sensors The nacelle of the turbine houses some of the most important components of a turbine. These

include the Shaft, Gearbox, Generator, etc. Advanced sensors which monitor the temperature and

pressure among many other parameters constantly feed information into the electronic control

system of the turbine which would detect any abnormalities and determine if a system shut down is

necessary. Overheating can present numerous problems to a turbine because this can lead to fire,

additional stress placed on components and bearings, etc.

8.4 Anti-Icing Systems A wind turbine’s blades are constantly exposed to the environment which requires it to withstand

large variations in temperature. A significant problem in wind turbine operation is having ice build-up

within the blades. While building up of ice can present a danger of the ice falling once the turbine is

operational, it also presents challenges to its efficiency due to ice formation changing the shape of

the aerofoil shape of the blades. Blade design is a carefully researched area and this change in shape

due to ice can reduce its operating efficiency while presenting dangers to people below. Many

modern turbine blades have systems to deal with such situations. Parent and Ilinca (28)conduct a

thorough review of the current systems that exist for anti-icing and de-icing systems. These include a

special coating to prevent the formation of ice and a super-hyperbolic coating which does not allow

water to remain on the surface. Other systems include inducing heat in order to prevent the ice

build-up.

8.5 Material Failure Material selection is extremely important in the design of a wind turbine due to its operating

conditions. Testing of this material is also important in order to determine the effects that are

present during high levels of loading. A recent report by Elforsk (29)provides a thorough guidance of

damage prevention to many parts inside the nacelle (primary/secondary shafts, rotor hub, bolts,

gearboxes, bearings etc.). Many failures are attributed to fatigue or corrosion and recommendations

are made regarding various testing methods that can be employed (Eddy Current, Magnetic Particle,

25 | P a g e

Sonic, Termographic etc.). Therefore the timely testing and observation to such damage could

prevent incidents such as a blade failure, gearbox failure etc.

9 Manufacturing Methodology and Processes (MH)

9.1 Design for Manufacture/Design for Assembly Modern product development states that a product should not only be ‘simply designed’. It should

also consider the path the product would take through its manufacturing, assembly, disassembly and

finally through servicing of the product. In their book, Kalpakjian and Schmid (30) mention that

design and manufacturing must be intimately interrelated. They argue that we should not view these

two as separate identities but two that must go hand in hand. When any design process is

undertaken, it is vitally important to do so for each part and component which would also reap its

benefits economically. This would also allow the company to standardise its manufacturing process

so that productivity can be improved. Employing Lean Six Sigma (discussed in a later section) is

another popular and effective method of achieving maximum productivity for a process. Although

initial costs may be incurred to implement six sigma methods and techniques, many companies large

and small, have achieved significant increases in productivity and efficiency along with long term cost

savings. This concept is known as Design for Manufacture (DFM).

Kalpakjian and Schmid (30)further highlight that DFM is a comprehensive approach to the production

of goods, and it integrates many design features which should take into consideration the materials,

manufacturing methods and processes among many others. This requires that the designer have a

fundamental understanding of such processes and specifically for DFM, about various machining

processes and equipment. If a designer wants to have a successful product, he/she should also

understand the effects of machining too. These include surface finish, accuracy of each machining

process, processing time etc.

An extension from DFM is DFA (Design for Assembly), which constitutes the next step after the

manufacture of individual components. When considering cost of operating a business, the efficiency

of the assembly process is critical to overall costs associated for the product. If DFA methods are

applied to a product design, then it would consider the ease, speed and cost of assembling the parts

together. The ease of assembly would be considered at a design stage because the easier it is to

assembly, the quicker it would be which would save precious time of the employees. If would

contribute to the bottom line of the business enabling to produce more units within a given period of

time. DFM and DFA can be combined as a methodology named DFMA (Design for Manufacturing

and Assembly).

DFMA can now benefit from advanced computer software that would help the designer from the

very beginning of the process. Modern designers use Computer Aided Design (CAD) software which

can now aid them to use DFMA effectively. Greenlee defines the cost split for DFMA as 70% for

design decisions (Cost of materials, processing, and assembly), 20% for production decisions (process

planning and tooling selection) and the remaining 10% other costs. Greenlee also gives a

comprehensive 10-step guideline for DFMA which summarises the whole process. They are given

below:

1. Reduce the number of parts

2. Develop a modular design

3. Use of standard components

4. Design parts to be multi-functional

5. Design parts for multi-use

6. Design for ease of fabrication

7. Avoid separate fasteners

26 | P a g e

8. Minimize assembly directions

9. Maximize compliance

10. Minimize handling

9.2 Material Selection An integral process after the design of a product has been conceptualised is material selection.

Material Engineering has many varieties of materials for a designer to choose from. The decision for

this is taken based on many specifications, which for the Turbine, can be found in the Product

Development Specification (PDS). Types of material can be classified as follows (30):

1. Ferrous Metals

2. Non-Ferrous Metals

3. Plastics

4. Ceramics, Glass Ceramics, Glasses, Graphite, Diamond etc

5. Composites

6. Nano-Materials, alloys etc.

For the turbine design, various materials were considered and many factors were taken into

consideration when choosing such materials. For example, at a conceptual stage, the material for

turbine blades was chosen as aluminium for their lightweightness and cost. However, applying DFMA

methodologies, it was decided to use high strength plastics due to ease of manufacturing and also a

lower cost per part. Since plastic also is a non-conductive material, it is even more suited for its

function as a blade for the given turbine design as the generator design warrants electric wires to be

running through the blades. This is an added benefit from a product safety point of view. This

highlights the importance of considering such factors in the design selection.

9.3 Material Properties Once the type of material is selected, its properties need to be analysed and the designers should

consider if it’s fit for purpose. Along with the type of material, its properties would be a decisive

factor in the manufacturing process. Various material types can have different properties. For

example, within metal alloys, there are several hundreds, if not more, variations that can be created

in order to gain the ideal type of material the designer is seeking. This flexibility gives a designer the

freedom which does not restrict the outcome that is expected.

Materials can be classified into types of properties, which are:

1. Mechanical Properties: These are properties such as strength, toughness, ductility etc. These

properties need to be chosen carefully according to the physical environment in which the

end product will be operating. Since the turbine will be operating outdoors all year round, it

should be expected to last through many harsh weather and other environmental conditions.

2. Physical Properties: Density, Thermal Expansion, conductivity, melting point, electrical

properties etc. These properties should be chosen to match the operating conditions relating

to the product as well as the environment. For example, since the electrical wires need to

travel through the turbine blades, plastic is an ideal choice due to conductivity of the

material. Also, the magnets used in the generator are selected as such because of its

electrical properties and its intended function to produce electricity which would be the

primary outcome of the turbine.

3. Chemical Properties: These properties can be corrosion resistance, flammability, oxidation

etc. This is also highly important since the turbine will be continuously exposed, factors

which affect its chemical properties would need to be strong.

4. Manufacturing Properties: These would help identify the best manufacturing methods for

any given property. They would determine if a certain material can be cast, machined,

welded, formed etc. This decision would ultimately form the criteria by which the product

would need to be manufactured and also its end service life. These factors would also

directly affect the cost of manufacture and labour skills required to carry out the various

tasks.

9.4 Cost and AvailabilityOnce the material selection has taken place, the next step to take into consideration is the cost and

availability of those materials. For any given material, the cost and availability are related to each

other. For example, if a material is not wide

higher. Conversely, a very widely available material will be relatively cheaper to

and Schmid (30) mention that the economic aspect of a material is as

consideration of the properties and characteristics of that material.

Another method of costs for manufacturing to increase is if DFM or DFMA is not followed properly.

For example, if the raw or processed materials required by t

shape or size, then adjustments would be required. For example, when designing the mounting

system for the turbine, if the diameter of the mast is not of a standard size, then further work would

be required at the manufacturing stage which would require a higher diameter mast to be bought

and then material taken off. This extra process will add further cost to the product.

9.5 Selection of manufacturing processesOnce the primary design of the turbine is completed, t

would begin for each component. This is a vast area since there are a number of components which

would require different manufacturing processes. It is also very likely that a certain component could

be manufactured various methods, at which point a decision would have to be made to determine

the type of manufacturing that would closely resemble the needs of the product.

Typical manufacturing processes can be broadly categorized into 5 types:

Source: Kalpakjian and Schmid(30)

Kalpakjian and Schmid also provides a rough guideline on the selection of a manufacturing process;

mentioning that it depends not only on the shape to be produced but also on many other factors

1. Casting

2. Forming and Shaping

3. Machining

4. Joining

5. Finishing



ility Once the material selection has taken place, the next step to take into consideration is the cost and


other. For example, if a material is not widely available, it would inevitably drive the cost factor

higher. Conversely, a very widely available material will be relatively cheaper to

mention that the economic aspect of a material is as important as technological

consideration of the properties and characteristics of that material.


For example, if the raw or processed materials required by the design are not available in the desired



manufacturing stage which would require a higher diameter mast to be bought


Selection of manufacturing processes Once the primary design of the turbine is completed, the selection of the manufacturing process



d various methods, at which point a decision would have to be made to determine


Typical manufacturing processes can be broadly categorized into 5 types:

(30)



•Expendable Mould

•Permanent Mould

•Rolling, Forging, Extrution, Drawing

•Sheet Forming, Powder Metallurgy and moulding

•Turning, Boring, Drilling, Milling, Planing, Shaping

•Broaching, Gringing, Ultrasonic Machining

•Welding, Brazing, Soldering

•Diffusion Bonding, Adhesive Bonding and mechanical Joining

•Honing, Lapping, Polishing, Burnishing, Deburring

•Surface Treating, Coating and Plating

27 | P a g e



Once the material selection has taken place, the next step to take into consideration is the cost and


ly available, it would inevitably drive the cost factor

higher. Conversely, a very widely available material will be relatively cheaper to source. Kalpakjian

important as technological


he design are not available in the desired



manufacturing stage which would require a higher diameter mast to be bought


he selection of the manufacturing process



d various methods, at which point a decision would have to be made to determine




Sheet Forming, Powder Metallurgy and moulding

Turning, Boring, Drilling, Milling, Planing, Shaping

Diffusion Bonding, Adhesive Bonding and mechanical Joining

Honing, Lapping, Polishing, Burnishing, Deburring

28 | P a g e

that relate to the topics discussed above. For example, certain materials which are brittle and/or

hard cannot be shaped easily but casting is a more relevant method.

Within the next few sections, common manufacturing techniques will be discussed and

recommendations can be made for manufacturing techniques relative to the turbine. The types of

materials will be broadly categorized into metals and plastics. Firstly, a brief discussion on their

various properties which make it suitable for each process will be discussed, followed with methods

in which they could be manufactured.

9.6 Metal and Metal Alloys Metals have good bonding properties, this key feature distinguishing them from non-metallic

materials. The metals have free electrons, which are free to move from one atom to the other and

they determine certain material properties, such as electrical conductivity.

The mechanical, physical and chemical properties of the metals and alloys are influenced by their

microstructure, composition, processing and treatment methods used in obtaining the final product.

Relevant basic properties, such as ductility, strength, hardness, toughness etc., and others, such as

resistance to wear and corrosion, are dependent on the elements that are alloyed and on heat-

treatment processes applied to the material. Cold-working operations are available for non-heat-

treatable alloys, such as rolling, forging and extrusion. (30)

Different material manufacturing processes are analysed in the next section in order to determine

the best approach to be applied for the materials used in the wind turbine.

9.7 Metal Casting Processes A basic casting process consists of the following: pouring the molten metal into a mould pattern,

cooling it and removing it from the mould. Certain aspects are important to be considered, such as

the flow of the molten metal, the solidification and cooling method and the influence of the type of

mould material. A few factors influence the aspects of casting mentioned above: the flow is

determined by the mould design and flow characteristics, the solidification and cooling are affected

by metallurgical and thermal properties, while the type of mould influences the rate of cooling and

the number of defects. (30)

Various casting processes have been developed over time for different types of applications and their

advantages and limitations can be found in Table 2.

Process Advantages Limitations

Sand Almost any metal cats; no limit to size,

shape or weight; low tooling cost.

Some finishing required; somewhat coarse

finish; wide tolerances.

Shell mould Good dimensonal accuracy and surface

finish; high production rate.

Part size limited; expensive pattern and

equipment required.

Expendable

pattern

Most metals cast with no limit to size;

complex shapes.

Patterns have low strength and can be costly

for low quantities.

Plaster mould Intricate shapes; good dimensional

accuracy and finish; low porosity.

Limited to nonferrous metals; limited size

and volume of production; mould making

time relatively long.

Ceramic mould Intricate shapes; close tolerancesparts;

Limited size.

29 | P a g e

good surface finish.

Investment Intricate shapes; excellent surface finish

and accuracy; almost any metal cast.

Part size limited; expensive patterns, moulds

and labour.

Permanent

mould

Good surface finish and dimensonal

accuracy; low porosity; high production

rate.

High mould cost; limited shape and

intricacy; not suitable for high melting point

metals.

Die Excellent dimensional accuracy and

surface finish; high production rate.

Die cost is high; part size limited; usually

limited to nonferrous metals; long lead time.

Centrifugal Large cylindrical parts with good quality;

high production rate. Equipment is expensive; part shape limited.

Table 2: Summary of Casting Processes, their Advantages and Limitations (30)

The casting industry is impacted by two major trends. The first is continuing mechanisation and

automation of the casting process, leading to changes in the use of equipment and labour. The

second trend is the increasing demand for high quality casting with low dimensional tolerances and

no defects. SeeTable 3 for general characteristics of the casting processes.

Process Sand Shell Expendable

mould

pattern

Plaster

mould

Investment Permanent

mould

Die Centrifugal

Typical

Materials Cast

All All All Nonferrous

(Al, Mg, Zn,

Cu)

All (high

melting

point)

All Nonferrous

(Al, Mg, Zn,

Cu)

All

Minimum

Weight (kg)

0.05 0.05 0.05 0.05 0.005 0.5 <0.05 -

Maximum

Weight (kg)

No limit 100+ No limit 50+ 100+ 300 50 5000+

Typical Surface

Finish (m-6

, Ra)

5-25 1-3 5-20 1-2 1-3 2-3 1-2 2-10

Porosity* 4 4 4 3 3 2-3 1-2 2-10

Shape

Complexity*

1-2 2-3 1 1-2 1 3-4 3-4 3-4

Dimensional

Accuracy*

3 2 2 2 1 1 1 3

Minimum

Section

3 2 2 1 1 2 0.5 2

30 | P a g e

Thickness (mm)

Maximum

Section

Thickness (mm)

No limit - No limit - 75 50 12 100

Table 3: General Characteristics of Casting Processes. *Relative rating: 1 best - 5 worst. (30)

The surface finish of the products depends on the material used in making the mould, as

well as on the manufacturing route selected. Surface roughness figures can be observed in

Figure 43.

Figure 43: Surface Roughness in Casting and other Metalworking Processes (:272)

9.8 Sand Casting Sand casting is a traditional method of casting metals and it consists of:

• Placing a pattern with the desired casting shape in sand to make an imprint

• Incorporating a gating system

• Filling the resulting cavity with molten metal

• Allowing the metal to cool until it solidifies

• Breaking away the sand mould and removing the casting (30).

Figure 44: Figure of sand-casting operations (30)

31 | P a g e

Figure 45: of a sand mould (30)

9.9 Sands Silica sand (SiO2) is used by most sand casting operations. Sand is cost effective and is suitable as a

mould material due to its resistance to high temperatures. There are two general types of sand:

naturally bonded (bank sand) and synthetic(lake sand). The last one is preferred as it can be

controlled more accurately (30).

9.10 Types of Sand Moulds Based on the types of sand contained and on the methods used to produce them, there are three

basic types of sand moulds: green-sand, cold-box and no-bake moulds.The green moulding sand is

the most commonly used sand mould. It is a mixture of sand, clay and water and the term “green”

refers to its moist state when the metal is poured onto it. This is the most cost-efficient sand mould

method (30).

9.11 Patterns Patterns are employed to mould the sand into the shape of the desired casting. They can be made of

different materials and their selection is made based on the shape and size of the casting, the

dimensional accuracy, the number of finished products and the moulding process. SeeTable 4 for

characteristics of pattern materials.

The strength and durability of the pattern material should be selected according to the number of

castings desired. The pattern may be made out of more materials to reduce wear in critical regions

and they are designed to suit the application and economic requirements. There are a few types of

patterns, such as the one-piece, split and match-plate patterns (30).

Rating*

Characteristics Wood Aluminium Steel Plastic Cast Iron

Machinability 1 2 2 2 2

Wear Resistance 4 2 1 3 1

32 | P a g e

Strength 3 2 1 2 2

Weight** 1 2 4 2 4

Repairability 1 4 2 3 2

Resistance to

Corrosion***

1 1 4 1 4

Resistance to

Swelling***

4 1 1 1 1

Table 4: Characteristics of Pattern Materials. *relative rating: 1 excellent, 2 good, 3 fair, 4 poor. **as a factor in operator

fatigue. ***by water (30).

9.12 Sand-Moulding Machines The first sand moulds consisted of compacting the sand around the pattern by hand hammering, but

a more modern approach is applied to most sand casting operations nowadays: the sand mixture is

compacted by moulding machines (see Figure 46). They offer great advantages over the traditional

method, such as reducing labour and creating high quality casting by improving the application and

distribution of forces, manipulating the mould in a controlled manner and increasing production

rate.(30)

Figure 46: Designs of squeeze heads for mould making: (a) conventional flat head; (b) profile head, (c) equalising squeeze

pistons; (d) flexible diagram (30)

9.13 The Sand Casting Operation The melting of the raw materials starts the manufacturing process. Then the metal is poured in the

sand mould and it is followed by the casting cooling which provides slow uniform cooling. The cast is

then removed from the sand moulds and it is cleaned. If desired, heat treatment can be applied

33 | P a g e

e.g.stress relieving, annealing etc. In addition, the wear resistance of the metal can be enhanced at

the surface by laser hardening.

9.14 Die Casting The die-casting process was developed in the early 1900's. The molten metal is forced into the die

cavity at pressures ranging from 0.7MPa to 700MPa. The weight of most castings ranges from less

than 90g to about 25kg. There are two basic types of die-casting machines: hot-chamber and cold-

chamber (30).

9.15 Hot-Chamber Process In the hot-chamber process, a piston traps a volume of molten metal and forces it into a die cavity

through a gooseneck and a nozzle. Pressures range up to 35MPa, with an average of 15MPa. The

metal is help under pressure until it solidifies in the die. See a schematic diagram of the hot-chamber

process inFigure 47 (30).

Figure 47: Schematic illustration of the hot-chamber die-casting process (30)

9.16 Cold-Chamber Process In the cold-chamber process, molten metal is poured into a cold injection cylinder (shot chamber);

hence the shot chamber is not heated. The metal is forced into the die cavity at pressures usually

ranging from 20 to 70MPa, although they can be as high as 150MPa. See figure 5 for a schematic

diagram of the process (30).

Figure 48: Schematic illustration of the cold-chamber die-casting process (30)

34 | P a g e

High-melting-point alloys of aluminium, magnesium and copper are normally cast using this method.

Molten-metal temperatures start at about 600 degrees Celsius for aluminium and some magnesium

alloys and increase considerably for copper and iron based alloys (30).

9.17 Process Capabilities and Machine Selection Dies have a tendency to part unless clamped due to high pressure involved in the casting process.

Die-casting machines are rated according to the clamping force that can be exerted to keep dies

closed, but also according to other factors, such as die size, piston stroke, shot pressure and cost

(30).

Die-casting has the capability for time-effective production of high strength and quality parts with

complex shapes. It also produces good dimensional accuracy and surface details, so that parts

require little or no subsequent machining or finishing operations (30).

Additionally, due to the fact that molten metal chills rapidly at the die walls, the casting has a fine-

grained, hard skin with higher strength. With good surface finish and dimensional accuracy, die-

casting can produce surfaces that are normally machined.

Equipment is costly, particularly the dies, but labour costs are generally low as the process is semi- or

fully automated. Die-casting is economical for large production runs. The properties and typical

applications of common die casting alloys are given in Figure 49 (30).

Figure 49: Properties and Typical Applications of Common Die Casting Alloys (30).

9.18 Forging of Metals Forging is a process in which the work piece is shaped by compressive forces applied through various

dies and tools. Simple forging can be performed using a heavy hand hammer and an anvil, but more

modern techniques require a set of dies and a press or a forging hammer (30).Forged parts have

good strength and toughness as the metal flow and grain structure can be controlled; they can be

used for highly stressed and critical applications (30).Forging may be done at room temperature (cold

forging) or at more elevated temperatures (warm or hot forging). Cold forging requires greater forces

because of the higher strength of the material, but it produces parts with good surface finish and

dimensional accuracy. Hot forging requires lower forces, but the quality of the products is not as

good (30).

35 | P a g e

A component that can be forged successfully may also be manufactured economically by other

methods, such as casting. However, each process has its own advantages and limitations with regard

to strength, toughness, dimensional accuracy, surface finish and defects (30).

The open die forging uses simple, inexpensive dies, but it is limited to simple shapes and a low

production rate. The closed die forging has good dimensional accuracy and reproducibility, but

machining is often necessary for the finished product (30).

Forging was considered as an alternative manufacturing route to casting, but due to its limitations or

high cost, metal casting is the preferred manufacturing technique employed for the wind turbine

components.

9.19 Extrusion and Drawing of Metals In the extrusion process, a billet (generally round) is forced through a die. Almost any solid

or hollow constant cross-section may be produced by extrusion, creating semi-finished

parts(30).

In the basic extrusion process, called direct or forward extrusion, a round billet is placed in a

chamber and forced through a die opening by a hydraulically driven ram or pressing stem.

The die opening might be round or it may have various shapes. In indirect extrusion (reverse,

inverted or backward extrusion), the die moves toward the billet.

In hydrostatic extrusion, the billet is smaller in diameter than the chamber, which is filled

with a fluid and the pressure is transmitted to the billet by a ram. Unlike in direct extrusion,

there is no friction to overcome along with the container walls. Another type of extrusion is

lateral or side extrusion(30).

Important factors in extrusion are die design, extrusion ratio, billet temperature, lubrication

and extrusion speed. Depending on the ductility of the material, extrusion may be carried

out at room temperature (cold extrusion) or at an elevated temperature (hot extrusion). The

cold extrusion combines extrusion with forging operations and it is capable of economically

producing discrete parts in various shapes with good mechanical properties and dimensional

tolerances(30). Commonly used materials are aluminium, copper, steel, magnesium and

lead. Other metals and alloys can also be extruded, having different levels of difficulty.

Drawing is a process through which the cross-section of a solid rod, tube or wire is reduced

or changed in shape by pulling it through a die(30). Although the cross-section of most

drawn products is round, other shapes can also be drawn(30).

9.20 Forming and Shaping Plastics The processing of plastics involves operations similar to those used to form and shape

metals. Plastics can be moulded, cast, machined etc. at relatively low temperatures; hence,

unlike metals, they are easy to handle and require less energy to process. The properties of

plastic components are greatly influenced by the manufacturing process and a thorough

control of its conditions is vital for good part quality(30).

Basic processes and their characteristics can be seen in Table 5.

Process Characteristics

Extrusion Long, uniform, solid or hollow complex cross-

sections; high production rates; low tooling

costs; high tolerances.

36 | P a g e

Injection moulding Complex shapes of various sizes, eliminating

assembly; high production rates; costly tooling;

good dimensional accuracy.

Structural foam moulding Large parts with high stiffness-to-weight ratio;

less expensive tooling than in injection moulding;

low production rates.

Blow moulding Hollow thin-walled parts of various sizes; high

production rates and low cost for making

containers.

Rotational moulding Large hollow shapes of relatively simple shape;

low tooling cost; low production rates.

Thermoforming Shallow or relatively deep cavities; low tooling

costs; medium production rates.

Compression moulding Parts similar to impression-die forging; relatively

inexpensive tooling; medium production rates.

Transfer moulding More complex parts than compression moulding

and higher production rates; some scrap loss;

medium tolling cost.

Casting Simple or intricate shapes made with flexible

moulds; low production rates.

Table 5: Characteristics of Forming and Shaping Processes for Plastics

9.21 Injection Moulding Injection moulding is essentially the same process as hot-chamber die-casting (see Figure 50).

Just as in extrusion, the barrel (cylinder) is heated to promote melting. However, with

injection-moulding machines, a far greater portion of the heat transferred to the polymer is

due to frictional heating. The pellets or granules are fed into the heated cylinder and the

melt is forced into a split-die chamber, either by a hydraulic plunger or by the rotating screw

system of an extruder.

Newer systems hare reciprocating screw type (see Figure 50). As the pressure builds up at the

mould entrance, the rotating screw begins to move backwards under pressure to a

predetermined distance; this movement controls the amount of material to be injected. The

screw then stops rotating and is pushed forward hydraulically, forcing the molten plastic into

the mould cavity. Injection-moulding pressures usually range from 70MPa to 200MPa(30).

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Figure 50: Injection moulding with (a) plunger, (b) reciprocating rotating screw (30)

9.22 Process Capabilities Injection moulding is a high rate production process and allows good dimensional control.

Typical cycle times range from 5 to 60 seconds. The moulds are generally made out of steel,

beryllium-copper or aluminium and they have multiple cavities, so that more than one part

can be made in one cycle. Mould design and the control of material flow in the die cavities

are important factors to be considered for the quality of the product(30).

9.23 Rotational Moulding Most thermoplastics and some thermosets can be formed into large hollow parts by

rotational moulding. The thin walled metal mould is made of two pieces (split female mould)

and is designed to be rotated about two perpendicular axes (see figure 9). A premeasured

quantity of powdered plastic material is placed inside the warm mould. The powder is

obtained from a polymerisation process. The mould is then heated, while rotating about the

two axes.

This action tumbles the powder against the mould, where heating fuses the powder without

melting it. In some parts, a chemical cross-linking agent is added to the powder.

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Figure 51: The rotational moulding (rotomoulding or rotocasting) process (30)

Rotational moulding can produce parts with complex with complex hollow shapes and with a

wall thickness starting from 0.4 mm. Cycle times are longer than in other moulding

processes, but equipment costs are low. Quality control considerations usually involve

accurate weight of the powder placed in the mould, thorough rotation of the mould and

temperature-time relationship during the oven cycle(30).

10 Product Design Specification (MH/MT)

1. Dates of P.D.S Production and Adoption

1.1. This Product Design Specification was created on 31/01/2013

1.2. This Product Design Specification was adopted by all members of the Group on 31/01/13

2. Introduction

2.1. This design specification is for the proposed concept design of a small scale wind turbine to

be powered by wind

2.2. The wind turbine named above will henceforth be known as ‘The Turbine’ or ‘The Product’

2.3. The aim of this design specification is to provide detailed analysis of the requirements

3. Duty Description

3.1. Harness wind energy through a horizontal wind turbine to produce electricity in order to

provide constant power to a typical domestic refrigerator

3.2. The power generated will be stored within a battery bank containing two power outlets;

one to power the refrigerator and the other to power an appliance of the user’s choice

3.3. Further excess power will be sold back to the national grid based on a feed in tariff

4. Design Criteria

4.1. General Design Criteria

4.1.1. The turbine is intended to be a mass produced item where assumptions are to be made

in relation to pricing, marketing and other design factors.

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4.1.2. The turbine is to be designed to operate within a range of wind speeds between 5 and

20 m/s and appropriate safety systems to ensure shutdown in the event of excessive

wind speeds as per section 4.5

4.1.3. The design of the turbine should comply with the ‘Betz limit’ which limits the power

extracted from the wind at 59.25%

4.2. Legal Constraints/Building Regulations

4.2.1. The requirements set out below are to be met at all times in order for the turbine to be

installed without requiring further planning permission

4.2.2. It is recommended however that the local council of the area in which the turbine is to

be installed, be contacted in case separate regulations exist

4.2.3. Such development rights are applicable for building mounted wind turbines applicable

to detached houses or other detached buildings within the boundaries of a house or

block of flats.

4.2.4. In addition to the criteria set out in 4.2.2 a block of flats should not contain commercial

premises

4.2.5. The installation of the wind turbine must comply with criteria set out in the Micro

generation Certification Scheme Planning Standards (or equivalent)

4.2.6. The installation cannot be carried out on protected land i.e. national parks, heritage

sites, protected and/or land with restricted access for legal reasons

4.2.7. Only the first turbine installation is exempt from planning permission. Any further

installations would be subject to permission from the local council as applicable by

their requirements.

4.2.8. The turbine in an installed condition is not allowed to protrude more than 3 meters

above the highest part of the roof (excluding the chimney) or exceed an overall height

(including building and turbine) of 15 meters, whichever is lesser

4.2.9. The distance between the ground level and lowest part of the wind turbine blade must

not be less than 5 meters

4.2.10. No part of the turbine is allowed to be within 5 meters of any boundary

4.2.11. The swept area of the turbine blades must be no more than 3.8 square meters

4.2.12. In Conservation Areas, an installation is not permitted if the building mounted wind

turbine would be on a wall or roof slope which fronts a highway

4.2.13. The materials used within the blades must be non-reflective

4.2.14. The turbine is to be removed as soon as it is reasonably practicable when no longer

needed for micro generation

4.2.15. The turbine is to be sited (or mounted), so far as practicable, to minimise its effect on

the external appearance of the building

4.3. Power Requirements

4.3.1. As set out in Section 3, in order to fulfil its primary duty of providing power to a

domestic refrigerator, a minimum production of 0.5 kW/h is expected although it is

aimed to be able to produce between 1-1.5 kW/h in order to satisfy secondary duty as

set out in 3.2

4.4. Power Management

4.4.1. A system needs to be in place in order to manage the power that is generated by the

turbine, including regulators and converters

4.4.2. The power management system is also required to provide, at least, a simple interface

for the end user where information about the current system can be gained

4.4.3. A power consumption and production log is beneficial to have for maintenance and

analysis purposes

4.5. Safety Systems

4.5.1. In the event of a wind over speed event, a mechanical brake system is to be applied to

stop the turbine from rotating and thereby posing a safety risk

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4.5.2. Safety systems are to be built into the power management system where the current is

to be regulated before delivered to the household

4.6. Building Mounting

4.6.1. It is required that the turbine is designed to be mounted on a typical UK household

4.6.2. The mounting system is to be designed to be able to withstand forces produced by the

turbine and nature

4.6.3. The design of the mounting system should permit ease of access to the turbine and its

components during maintenance and capability to remove the turbine if necessary

5. Material Selection

5.1. The selection of materials for the construction of any part of the turbine should be done

with the aim of achieving the requirements set out in sections 3 and 4 i.e. the material

selected must be fit for function and purpose

5.2. In order to meet the cost requirement set out in 4.1.1 the cost of each selection needs to be

carefully reviewed and if a selection of materials (which meets the criteria) is available, then

the cheapest material should be used unless any other valid reasons exist.

5.3. As highlighted in 4.1.2 prices for materials should be based on bulk purchase prices, as this

would reduce the overall manufacturing cost of the turbine.

5.4. The materials selected should also be considered for their recycling and disposable

properties at the end of the turbine life

6. Production

6.1. If the design of the wind turbine requires customised parts, then it should be investigated if

such parts are cheaper to be manufactured in-house or from a specialist manufacturer

6.2. Packaging of the turbine should be designed to minimise shipping costs and space and

wherever possible, consist of sustainable and recyclable materials

7. Selection of Conceptual Design

7.1. All members of the group are to be involved in an equal manner regarding the selection of

conceptual designs

7.2. All members are to be given specific areas of responsibility in the design of the turbine and

it is expected for them to carry out a thorough research into such areas and inform the

other members of their findings

7.3. The selection of the final conceptual designs are to be made as a group where input from

the areas researched in 7.2 is required

8. Maintenance

8.1. The design of the turbine should, as practicable as possible, not include user serviceable

parts due to safety reasons

8.2. Routine service maintenance is to be carried out by a certified technician at six (6) month

intervals and a thorough safety and electrical check carried out every twelve (12) month

period

8.3. If any part(s) that are contained within the turbine is judged to have a limited life either

through hours of operation or limited life cycles, they are to be made clear in the product

service schedule and made clear to the end user

9. Financial

9.1. The production costs of the turbine must not exceed £250 (GBP)

9.2. The turbine is to be presented to the market at a profit of 15% above all costs incurred per

unit

9.3. The final cost at which the turbine is sold at should take into account all manufacturing,

labour, shipping and other such costs

9.4. The cost of the turbine is to be determined once a final value of the components is made

and it is then to be scaled to a production cost per unit for 20,000 units

10. Target Markets

10.1. The intended target market for this product is domestic home users where the

power requirement is for a medium sized refrigerator (or similar appliance)

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10.2. In addition, as stated in 3.2, extra flexibility is given to the user regarding power

consumption through additional power sockets made available through battery banks

10.3. The product is to be marketed as a ‘relatively’ inexpensive wind turbine where the

cost of purchase and installation would reflect as such

11. Operational Safety

11.1. It should be noted at all times during the design stage that the safety should be of

paramount importance at all times. Any aspect of the design should not post any safety risks

either to the consumer or cause damage to any surroundings.

11.2. The turbine should be designed that wherever possible, Foreign Object Damage

(FOD) should be prevented or minimized

11.3. Adequate protection needs to be given to any systems within the turbine containing

moving parts

11.4. Any systems that contain electrical elements are also required to be given proper

insulation and sealing properties

11.5. The turbine is to be accompanied with a thorough manual which provides clear

instructions to the user about its operation and safety features

11.6. The safety systems described in section 4.5 is to be tested as part of section 12 and

the results made available to the end user

12. Quality Assurance

12.1. In order to be compliant with various safety standards, the turbine is to be put

through a thorough testing process before it is launched into the market

12.2. Testing is to be carried out for the following conditions:

12.2.1. Expected range of operating wind speeds

12.2.2. Safety systems at wind over speed event

12.2.3. Expected temperatures throughout the year

12.2.4. High rain or snow events

12.3. Maintenance to be carried out at intervals specified in section 8

13. Engineering Drawings

13.1. Complete engineering drawings are to be done for the design of the turbine and its

components

13.2. Any such drawings are to be kept securely at all times

14. Intellectual Property (IP)

14.1. The design of the turbine should take into account any existing patents, copyright or

design protection(s) and should not at any time infringe such protection(s)

14.2. If any part of the turbine design requires design or copyright protection, applications

for such should be carried out

15. Revisions

15.1. Revisions to the Product Design Specification should be clearly marked at the top of

the document and the table provided below where the changes made are to be

documented

11 Design Conceptualisation

11.1 Blade (BP) A blade can be designed to have various shapes but as described in section 4.2.2, the lift and the drag

force need to be accounted for. The lift and the drag force depend on their coefficient value which

eventual depends on the aspect ratio (for finite blade structure) therefore changing the aspect ratio

would change the lift and drag force which will help us determine the advantages and disadvantages

of different blade structures.

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11.1.1 Design 1 Trapezoidal Planform Area design would allow us to account for the apparent wind (see section 4.2).

With length (h) being the span area, smaller chord length can be placed towards the tip of the blade

to reduce the chances of stall near to the root section. It also angles the blades from the root section

to increase lift due to the apparent wind as mentioned earlier. However, the aerodynamic centre for

this shape shifts towards the root chord which reduces the linear velocity (acting at the aerodynamic

centre due to the lift force) as its proportional to the force and the radius.It also lowers the aspect

ratio (compared to the rectangular planform with same root chordlength) which eventually increases

the induced drag and the requirement for the angle of attack. The other problem this design imposes

is the changing chord length, which changes the thickness of the aerofoil shape (see section 11.1.4).

This does not allow us to work out the volume of the blade structure accurately during the design

stage in order to estimate the mass accurately.

Planform Area� = 456789�

Volume: = A × t, where A is the planform area and t is the thickness

X axis Centroid =̅ = 9� �4567845678

11.1.2 Design 2 Rectangular Planform Area can also be used to design the wind turbine blade. This design has high

aspect ratio relative to the Trapezoidal Planform design (with same root chord length). Increase in

aspect ratio reduces the downwash but this design does not account for the apparent wind. However

the simplicity of this design (constant aerofoil shape) allows us to measure the volume more

accurately than any other planform shape, which means we can calculate the mass of the blade

accurately at design stage. Although caution must be paid while working out the volume as it’s not a

rectangular box but an aerofoil shape with rectangular planform area. This design has high aspect

ratio and therefore high coefficient of lift and low induced drag however; it has relatively high profile

drag.

Planform Area � = ? × @

Volume: = A × t, where A is the planform area and t is the thickness

X axis Centroid = 5�

11.1.3 Design 3 Triangular Planform areahas minimum span area but low aspect ratio as the trapezoidal planform

design and therefore poses the same problem of downwash. However it has relatively low profile

drag and low volume compared to the other two designs therefore the mass of the blade would be

low too.

a b

h

a

b

Planform Area � = 5×7�

Volume: = A 1 t, where A is the planform area and t is the thickness

X axis Centroid = 7�

11.1.4 Aerofoil Shape Various aerofoil profiles are available

Aeronautics (NACA). The agency

aerofoil shapes depending on the chord length

number give for each specific shape which depends on the chord length. M is the maximum chamber

divided by 100, P is the position of the maximum camber divide by 10 and DD is the thickness divided

by 100. NACA 2412 has maximum

shape and 12%.

For various chord lengths, wind turbine blades can be designed using various NACA profiles to

determine blades thickness and maximum chamber. The tail section can be altered for

maximize the lift but the design alterations can only be carried out after testing an aerofoil shape.

Experimental or computational analysis can be carried to improve the aerofoil shape and its

operational angle of attack.

11.1.5 Materials The wind turbine blade can be made out of range of materials available but the choice of material for

individual design heavily depends on the design aspects e.g. Lift the aerofoil shape generates, Length

of the blade, Tip velocity, etc. For large wind turbine b

light therefore carbon fibre reinforcement on a strong plastic is widely used. For a small scale wind

turbine blades, aluminium is more commonly used as they are more resistive to corrosion then iron.

High strength plastic can also be used for blades but the manufacturing cost could be high as the

blade surfaces would require smoothening.

wind turbine and, if reinforced with enough thickness to sustain stru

high angular velocity due to low mass.

11.2 Generator (KE)

11.2.1 Design 1

b a

, where A is the planform area and t is the thickness

Various aerofoil profiles are available for selection from the National Advisory Committee for

agency has various aerofoil profiles that can be used to

depending on the chord length. The profile shape depends on the NACA MPDD



NACA 2412 has maximum chamber line of 2% with 4% of maximum thickn


determine blades thickness and maximum chamber. The tail section can be altered for



nd turbine blade can be made out of range of materials available but the choice of material for


of the blade, Tip velocity, etc. For large wind turbine blades, material chosen needs to be strong but



ngth plastic can also be used for blades but the manufacturing cost could be high as the

smoothening. However plastic are really light weight for small scale

wind turbine and, if reinforced with enough thickness to sustain structural damage, they can produce

high angular velocity due to low mass.

Figure 52: Design 1

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National Advisory Committee for

profiles that can be used to generate different

ape depends on the NACA MPDD



chamber line of 2% with 4% of maximum thickness of an aerofoil


determine blades thickness and maximum chamber. The tail section can be altered for any profile to



nd turbine blade can be made out of range of materials available but the choice of material for


lades, material chosen needs to be strong but



ngth plastic can also be used for blades but the manufacturing cost could be high as the

However plastic are really light weight for small scale

ctural damage, they can produce

Description: Figure 52 illustrates the first preliminary for the generator the wind turbine. The

permanent magnet generator is mounted to a central shaft which runs through the bearing and

housing.

Materials: Rotor is made out of Magnetite

Advantages: No gear box required due to direct drive mechanism.

Disadvantages: Average cost of a 0.5 kW generator start from £100 which will increase the cost of

the product.

11.2.2 Design 2

Description:Figure 53 shows the second generator design for the wind turbine. This concept was

extracted from the permanent magnet generator theory. In this design, magnets are mounted on the

blade tip where the fluxes are distributed and the blades represent the rotor. A non

conducting circular section holds a number of circular bobbin wound armature copper coils

positioned circumferentially around the circular ring which acts as the stator of the ge

power is generated when the blade tip magnet pass through the copper coil banks mounted onto the

outer ring.

Materials: For the rotor, Neodymium magnet was chosen due to its high performances. The copper

wires were chosen for the stator due

Advantages: Since blade tip has the highest speed, the electricity generate from the generator is

much higher when comparing to the axial fixed generator. Also the mechanical resistance is much

lower (Blades are connected to a bearing n

the turbine to operate at a lower wind speed. This design reduces the noise, vibration and the size of

the wind turbine.

Disadvantages: The blade tip mounted magnets will add extra weight to the bl

increases the cut in wind velocity.

illustrates the first preliminary for the generator the wind turbine. The


Magnetite or Neodymium and stator is made using copper.

No gear box required due to direct drive mechanism.

Average cost of a 0.5 kW generator start from £100 which will increase the cost of

Figure 53: Design 2

shows the second generator design for the wind turbine. This concept was


luxes are distributed and the blades represent the rotor. A non


positioned circumferentially around the circular ring which acts as the stator of the ge


For the rotor, Neodymium magnet was chosen due to its high performances. The copper

wires were chosen for the stator due to less resistance.

Since blade tip has the highest speed, the electricity generate from the generator is


lower (Blades are connected to a bearing not to a yaw shaft) so the losses are low which will enable


The blade tip mounted magnets will add extra weight to the bl

the cut in wind velocity.

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illustrates the first preliminary for the generator the wind turbine. The


Neodymium and stator is made using copper.

Average cost of a 0.5 kW generator start from £100 which will increase the cost of

shows the second generator design for the wind turbine. This concept was


luxes are distributed and the blades represent the rotor. A non-magnetic, Non-


positioned circumferentially around the circular ring which acts as the stator of the generator. The


For the rotor, Neodymium magnet was chosen due to its high performances. The copper

Since blade tip has the highest speed, the electricity generate from the generator is


ot to a yaw shaft) so the losses are low which will enable


The blade tip mounted magnets will add extra weight to the blade tip which

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11.2.3 Design 3

Figure 54: Design 3

Description: Figure 54 illustrates the third generator design for the wind turbine. It also uses the

blade tip power generation system. However in this design the magnets are mounted on the outer

ring (Rotor) and the coils are wounded at the tip of the blade.

Materials: For the rotor, Neodymium magnet was chosen due to its high performances and copper


Advantages: The magnets are fixed in a N-S arrangement to create higher and uniform magnetic flux

between the two magnets, this effect create higher electricity from the turbine.

Disadvantages: Since the blade tip are equipped with coils the aerodynamic efficiency of the system

decreases. Total number of 8 magnets is used in this system which increase the total cost of the

system.

11.2.4 Design 4

Figure 55: Design 4

Description: Figure 55shows the schematics of the fourth conceptual design of the generator.

Turbine consists of two rotating rotor sections. Where the Inner blades tip consists of wounded

copper coils.

Materials: For the rotor, Neodymium magnet was chosen due to its high performances and copper


Advantages: The two counter rotating blade systems increases the frequency of flux-coil interaction

generates more electricity.

Disadvantages: Mechanically complicated to build due to the two counter rotating blade system.

Additional materials required to build outer rotating system, which increase the cost of the product.

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11.3 Preliminary Design of braking and mounting systems (MH)

11.3.1 Braking Systems

Having a well-defined and functional safety system is critical to any modern wind turbine

design. Common safety systems found in wind turbines have been reviewed and

considerations have been made for the initial concept.

A disc brake system was chosen as the primary method of stopping the wind turbine

primarily due to cost considerations. Aerodynamic braking is proven to efficiently stop a

turbine from rotating during high wind situations but they are expensive to implement, as

many systems will be required to operate it. Due to the current generator design requiring

coils to be installed at the blade tip, which would require cables to run within them, also

increases the complexity of having a pitch control mechanism within the rotor hub.

Three initial designs were formed for the braking system of the turbine.

11.3.2 Braking System Design 1 The 1st preliminary design of the wind turbine system contains the rotor hub seated on a set of

bearings which will contain an attached brake disc. This disc will be similar to that found on go carts

due to their small size as well as reduced weight compared to much larger car braking systems. The

surface area acting on the disc will be chosen to sufficiently provide braking at high wind speeds. A

hydraulic or electric actuator system will be mounted within the nacelle of the turbine in order to

provide the actuation force needed for the brake pads. An anemometer placed within the turbine

would measure the current wind speeds and activate the braking system.

Figure 56: Design 1

11.3.3 Braking System Design 2 The 2nd brake systems design incorporates the brake disc into the centre shaft which travels through

the turbine. This would require the shaft to be rotating at the same speed as the hub, which the disc

would be attached to. Due to the bearing system being installing within the hub, it was decided that

the rotor would not rotate along with the hub, but rather act as a ‘backbone’ to the turbine which

provides support to all systems.

Disc

Hub

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Figure 57: Design 2

11.3.4 Braking System Design 3 The 3rd brake system design is to incorporate aerodynamic braking. This would include a variable

pitch control system for the blades which requires a set of motors to be placed within the hub

system. When the detected wind speed exceeds a specified cut-off value, aerodynamic braking will

be activated which would bring the turbine to a gradual stop.

11.4 Mounting System (MH) The wind turbine is to be designed for the use of domestic UK homes and therefore the mounting

system should take into consideration current UK building regulations and legal requirements as well

as extracting maximum energy from the wind speeds predicted within such heights.

The limitations of the mounting system are highlighted in the PDS under section 4, which highlights

all the design considerations. A majority of the power management system for the turbine would not

necessarily be required to be placed within the nacelle and this lends to a reduction in weight and

space taken up by the nacelle. Although initially, a lattice steel structure could be considered the best

method to mount the turbine, costs could be reduced by either fixing the turbine within a steel pole

onto the chimney or a concrete base.

Examples of mounting systems that could be used are shown below from current small scale wind

turbines.

11.4.1 Mounting System Method 1 Mounting system method 1 includes a side mounted turbine on the wall of the building. This is

shown in FIGURE. Since roofs in domestic houses are at a given angle, if the house is a detached

dwelling, this system would be ideal as work would not need to be carried out on the roof itself.

Figure 58: Design 1

Disc Hub

Shaft

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11.4.2 Mounting system 2 Mounting system method 2 would require the turbine to be installed on the roof and includes a

hydraulic ram in order to adjust the tower height when necessary for maintenance and safety.

Figure 59: Design 2

11.4.3 Mounting System 3 Mounting system method 3 would be similar to the system highlighted in method 2, but without the

hydraulic ram. In order to maintain a low product cost, and taking into account height limitations

given in the PDS, this system is the chosen system as the final design.

Figure 60: Design 3

base

Mast

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11.5 Popular Wind turbine arrangements for domestic use (MT)

Figure 61: Typical Wind Turbine arrangements (31)

11.5.1 Introduction A charge controller or charge regulator limits the current being delivered by the power source to the

battery. To be useful, "12 volt" wind generators need to be capable of delivering 16 to 20 volts in

moderate winds (at say 250-400rpm). Most 12v batteries need around 14 to 14.5 volts to get fully

charged.

Wind turbines need to be protected from 'over speed' which could occur if a load was suddenly

removed or switched 'off'. Over speed protection is normally achieved by maintaining a constant

electrical load on the turbine as well as providing voltage regulation the charge controller also

ensures that this electrical loading is present at all times. The electrical load is either provided by

charging the battery, or if the battery is fully charged then the excess power is normally diverted to a

dump load/braking resistor (which could be used for air, water or under floor heating)in this

situation, the excess power would be sold to the national grid under Feed-In-Tariff.

11.5.2 Series Regulators Many charge controllers are designed to disconnect (or open circuit) the solar panel when the

battery becomes charged and re-connect the solar panel when the battery needs recharging. While

this is acceptable for solar panels, these series regulators are unsuitable as wind and water turbine

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charge controllers as they would cause the turbine to over speed and damage would result from

excessive centrifugal force or excessive vibration.

11.5.3 ShuntRegulators Have the following characteristics…

• The wind generator is not regulated or controlled and continuously delivers the available

power to the regulator and battery.

• The regulator constantly monitors the battery voltage and switches between two states

determined by the battery voltage.

• If the battery voltage falls below a "low" set limit the controller disconnects the dump

load and allows the battery to charge.

• If the voltage rises above a "high" set limit the controller turns on a dump load and isolates

the battery from further charging.

In normal operation the wind controller will cycle between these two binary operating states

(Charging and Charged), thus achieving the battery voltage regulation between the controllers low

and high voltage set points* (*Note: see hysteresis below) (32).

11.5.4 Two modes of operation There are two possible ways in which the simple shunt regulator can be incorporated into a wind

generation system; a "dump load controller" (sometimes called a "simple battery shunt" or "shunt

mode")anda "turbine brake controller" (sometimes called "back EMF braking" or "diversion mode").

The difference is that in “Diversion Mode” the regulator only diverts the instantaneous generated

power to the dump load and only when the battery is charged. Note: Stored battery power is never

dumped by a regulator in Diversion Mode (this is prevented by the presence of a blocking diode).In

“Shunt Mode” the regulator operates as a simple battery shunt and has to dump the generators full

rated power capacity each time it turns on (whatever the prevailing conditions) consequently the

dumping of battery power is a feature of this mode of operation.

In the "shunt mode" configuration, and in windy conditions, once the battery is fully charged the

rotor speed will not change significantly when the controller switches between the Charging and the

Dumping states. In the “turbine brake controller" configuration, once the battery is fully charged

(and the controller has entered into the “charged/dumping” state) the rotor speed will be

determined by the braking resistor impedance. If the braking resistor is low impedance, then the

rotor will be observed to slow down. As the controller switches back into the “charging” state then

the rotor will speed up again.

Some shunt regulators are designed to operate in one mode only, some can be configured in

either of the two modes during installation, some can be dynamically switched during operation.

Shunt regulators can’t operate in both modes at the same time.

11.5.5 Pulse Width Modulation Regulators • PWM charge controller regulates the power being sent to the battery.The PWM regulator is

a proportional controller which is capable of varying the charge duty cycle between 0 and

100%. The controller constantly checks the state of the battery to determine how fast to

send pulses, and how long (wide) the pulses will be. In a fully charged battery with no load, it

may just "tick" every few seconds and send a short pulse to the battery. In a discharged

battery, the pulses would be very long and almost continuous, or the controller may go into

"full on" mode. The controller checks the state of charge on the battery between pulses and

adjusts itself each time.

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• A PWM dump load controller regulates the 'excess' power which needs to be dumped. This is

an alternative way in which a PWM regulator can be configured. Instead of regulating the

power being sent to the battery (see above) it regulates the excess power that needs to be

dumped into a braking resistor. With a discharged battery, pulses would never be sent to the

braking resistor. When the battery is fully charged and excess power is still being generated

then the PWM dump load controller sends pulses or may go into "full on" mode if the

generated power is high.

With the development of PWM charge controllers came a new and improved way of charging

batteries using bulk, absorption, float and equalization charges. These are a great improvement over

shunt charge controllers as they are able to keep the battery voltage much more stable.

11.5.6 PWM regulator with a dump load Wind turbine system normally require PWM regulator with a dump load to maintain the load on

thegenerator/turbine and to dissipate energy when the battery becomes charged). Such regulators

allow the wind turbine to deliver all of the available power to the regulator and battery. Examples of

PWM shunt regulators which support an external dump load include the Xantrex C40 and

Morningstar Tristar-45 family of regulators.

11.5.7 Shorting the generator output? The output from a DC generator should never be ‘shorted’ while it is rotating since the commutator

and brushes will quickly burn out. Some small machines with more internal resistance and

servomotors may survive limited abuse but shorting the DC generator output as a means of

continuous regulation should be avoided.

AC wind generators have lots of kinetic energy stored within the rotating components and shorting

the generator output induces very large currents flowing within the coils. This may cause excessive

heat build-up and premature failure of the windings (particularly if the alternator windings are

potted within resin, as air cooling is severely constrained).

Shorting the windings of an AC generator should only be considered as a maintenance function. If the

turbine/generator does not stop within 10-15 seconds then the braking effect is insufficient to

overcome the wind strength. If the generator is allowed to continue to rotate with the generator

output shorted then permanent damage could occur. Shorting the AC generator output as a means

of continuous regulation should be avoided.

11.5.8 Wind compatible “Solar style” charge controllers? There are an increasing number of “solar style” charge controllers which utilize the shunt/diversion

mode architecture without a dump load. When the battery becomes charged the “solar style” charge

controller applies a short to the power source, which works perfectly well with solar panels, but care

needs to be taken when considering their use for wind generator applications. These “solar style”

charge controllers include the JUTE CMP24 family (20A, 30A and 45A), Hybrid controller CQ1210 and

Seca’sSolarix; Alpha, Gamma, Sigma and Omega family (with the ATONIC® chip architecture).

Modern wind turbines can be designed to take advantage of “solar style” charge controllers (they are

cheaper than conventional PWM controllers which require a dump load). However they need to be

designed from first principals for use with “solar style” charge controllers. Two wind turbine systems

that are compatible with “solar style” charge controllers (which do not have a dump load) include the

Wren Micro-turbine which is compatible with the Samrey 30A Shunt Charge Controller (a rebadge

SecaSolarix Omega) and the Macro-Wind small wind turbines (MW-200 and MW-400) which are

compatible with the solar style charge controller supplied by Macro-Wind. Additional protection has

52 | P a g e

been embedded within the wind turbine manufactured by Macro-Wind to ensure compatibility with

a solar style charge controller which has no provision for a dump load.

You should not assume that a new solar style charge controller which has no provision for a dump

load will be compatible with your existing wind generator. You need to check for compatibility with

your generator and the solar style charge controller suppliers. Apart from the damage referred to

above caused by the application of frequent shorts to the generator output there will be the

additional problem that the turbine would be beset with frequent stops. If the winds are light then

frequent stops means that you will lose the ability to generate power in low winds.

11.5.9 Maximum Power Point Tracking MPPT charge controllers can be used in conjunction with uniform solar arrays consisting of multiple,

identical solar panels. The MPPT controller is designed to maximise the quantity of power obtained

by performing a periodic sweep of the solar power curve to determine the ideal voltage at which the

maximum power can be extracted. The timing of the sweep has been optimized to take account of

solar events like "passing clouds" (typically the sweep occurs every 7 minutes).

The power output from fixed pitch wind generators have significant short term fluctuations, as the

speed is constantly changing with the variable wind conditions. MPPT systems are not fast enough to

keep up with the changing condition of the turbine. Consequently the MPPT sweep algorithm will

produce erroneous data with each gust of wind. Hence MPPT controllers are not generally used for

fixed pitch wind turbine generators.

The power output from variable pitch wind generators and from water turbines can remain constant

over the longer term. This makes them more suitable for use with MPPT power controllers.

11.5.10 Hysteresis Hysteresis is an integral characteristic with shunt regulators (but not with PWM regulators).The

regulator is either 'off' or 'on', with nothing in between. The regulator is a system; its input is the

battery voltage, and its output is the 'Charging' or 'Charged/Dumping' binary state. If we wish to

maintain a battery voltage of 12.5v, then the regulator may be designed to turn the dump load 'on'

when the battery voltage rises above the 12.6v set limit, and turn it 'off' when the battery voltage

falls below the 12.4v set limit. The controllers "low and high voltage set points" and a "lock out" time

constant within the controller define the characteristic hysteresis properties of the controller.

Domestic central heating thermostats also exhibit hysteresis. Further information on hysteresis can

be found on Wikipedia.

11.5.11 Lead-Acid Batteries Lead-acid batteries fall into two categories. 1. Shallow cycle - these are the type used to start your

car. They are designed to deliver a large amount of current over a short period of time. This type is

unsuitable for a home power battery bank. They cannot withstand being deeply discharged, to do so

shorten their life. 2. Deep cycle - Designed to be discharged by as much as 80% of their capacity, this

is the type of choice for home power systems. The life of deep cycle batteries will be extended if the

discharge cycle is limited to 50% of the battery capacity and if they are fully recharged after each

cycle (this avoids positive plate sulphating). The quickest way to ruin lead-acid batteries is to

discharge them deeply and leave them standing "dead" for an extended period of time. When they

discharge, there is a chemical change in the positive plates of the battery. Batteries that are deeply

discharged, and then charged partially on a regular basis can fail in less than one year.

Second hand batteries from computer UPS and GSM base-station installations frequently come onto

the market. These batteries are normally removed from service when the battery backup time (i.e.

53 | P a g e

the battery capacity) has fallen below acceptable operational limits. Batteries always have a

manufacturer’s date code on them (for warranty purposes), make sure you know what it is before

you purchase. Second hand traction batteries (milk float, fork lift and submarine) are ideal but

difficult to value. However the price will never fall below the scrap value for lead. Storage batteries

need adequate ventilation(33).

State of Charge (approx.) 12 Volt Battery Volts per Cell

100% 12.7 2.12

90% 12.5 2.08

80% 12.42 2.07

70% 12.32 2.05

60% 12.2 2.03

50% 12.06 2.01

40% 11.9 1.98

30% 11.75 1.96

20% 11.58 1.93

10% 11.31 1.89

0% 10.5 1.75 Table 6: State of Charge

11.5.12 Dump Loads (as used in 'battery shunt' configuration) Typically 0.5 to 2.0 ohms (for example: a 12volt 200watt dump load would consume 16.6amps and

have a resistance of0.72ohms).

The dump load should be dimensioned to dissipate the generators maximum output power. You can

use a "car ceramic heater" or a regular 12/24/48v immersion heater. If you need a higher capacity

dump load you can use a cheap DC-AC inverter to generate 240volts and a domestic oil filled

radiator.

Car headlight bulbs may be used for experimentation, but are not suitable as a permanent fixture

since they will burn out during high winds and without the dump load the controller will either "boil"

the battery or fail to load the generator which will then over speed (depending upon the controller

design and failure mode). Incandescent bulbs also have low impedance when cold and induce very

high switching currents. Dump loads can be controlled by MOSFET's or by relays.

11.5.13 Braking Resistor (as used in 'turbine brake controller' configuration) Typically 1 to 5 ohms

To determine your optimum braking resistor value you may need to experiment with different power

resistors during various wind conditions. A very low impedance braking resistor would cause the

turbine to slow instantaneously to a low speed, which could place unnecessary stresses on the

turbine. The benefit of the “turbine brake controller" configuration, which slows the rotor down, is

less wear and tear on the rotating components while the battery remains in its fully charged state. A

Rheostat is useful in determining the ideal brake resistor value when configured in the "turbine brake

controller" configuration. The braking resistor should be dimensioned to dissipate the generators

maximum output power.

11.5.14 Grid Tie Inverters A grid-tie inverter or a (GTI) is an electrical device that allows turbine or solar panels to complement

their grid power with renewable power. It works by regulating the amount of voltage and current

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that is received from the turbine or solar panel and converting this into alternating current. The main

difference between a standard electrical inverter and a grid-tie inverter is that the latter also ensures

that the power supplied will be in phase with the grid power.This allows individuals with surplus

power (wind, solar, etc.) to sell the power back to the utility. This is sometimes called "spinning the

meter backwards" as that is what literally happens.

On the AC side, these inverters must supply electricity in sinusoidal form, synchronized to the grid

frequency, and limit feed in voltage to no higher than the grid voltage including disconnecting from

the grid if the grid voltage is turned off. A major advantage of Grid Tie Inverters is that the

requirement for batteries is eliminated.

Grid-tie inverters have a maximum permitted input voltage. As wind speeds increase, this limit may

be exceeded. In these circumstances the grid-tie inverter will automatically disconnect the turbine

from delivering power to the mains. At this point the rotor is no longer loaded and it will rapidly

increase to a dangerous speed. High voltages are still being applied to the input of the "off-line" Grid-

tie inverter, which will destroy it. Then the rotor may also be destroyed by high speed vibration and

centripetal forces. An additional problem is mains failure as this will also remove the loading on the

rotor, with the same consequences. A frequency switch can be used to apply a diversion load and

brake to slow the turbine down to a safe speed, during either of these two conditions.

Grid-tie inverters also have a minimum input voltage which needs to be maintained if you wish to

remain connected to the grid. Falling outside of this min-max window will result in the GTI

disconnecting from the grid. To reach the minimum voltage you need to improve your ability to

capture the wind by changing the tower height, rotor size, number of blades, blade design, etc. (34)

12 Preliminary Design & Analysis

12.1 The Blades, the Hub & the Cone (BP)

Figure 62: Preliminary Blade Design

Design Features:

• NACA 0010 Airfoil Shape

• Ultra High Molecular Weight Polethylene

• Bolted by two M8 to the hub

• 6° angle of attack considering infinite wing Cl graph

• High aspect ratio as the span to chord length ratio is high

• Low induced drag as aspect ratio is high however; high profile drag

The initial design of the blades included trapezoid mount with thin section going into the hub bolted

together using M8 bolts. The design is not practical as it requires bolts to attach the blade with the

hub. This would induce high stress concentration on the plastic blade around the bolt area which

could result in a crack or a fracture. Plastic is also likely to deform if a constant force is applied which

55 | P a g e

means the bolt holes are likely to elongate making blades vibrate more and deform further resulting

in a catastrophic failure. The hub is made of aluminium and does not have any significant effect

compare to the blades. The cone is also plastic and bolted with the aluminium hub however; cone

has no major force acting on it and therefore the bolt hole elongations is not significant for the cone.

Figure 63: Preliminary Hub Design

Figure 64: Preliminary Cone Design

12.2 Generator design selection (KE)

Figure 65: Conceptual Design 3

12.2.1 Design Selection From the analysis of the conceptual designs, Design 3 was selected for the preliminary design. The

unique Blade tip generator system reduces the losses due to the axial rotating components. The cost

of the product is lower due to the use of separate stator and rotor. Due to high Blade tip speed high

energy generate from the tip.

Design 1 _ Use of conventional axial generator need to have a gear box in order to operate in low

wind speeds. The axial driven generators have higher losses due to friction, which reduce generator

efficiency and high noise pollution. So the conceptual design 1 wasn’t chosen for the preliminary

design.

Design 2_The design is based on wind tip generator concept. However, the magnets are mounted on

the blade tips which add extra weight. The cut in wind speed of the system is much higher in order to

generate power. Also cost of the magnets is higher and mounting it on a rotating component will

reduce the life cycle. Conceptual design 2 wasn’t selected for the final design.

Design 4_The conceptual design 4 has a two counter rotating blade system, where the sy

exceed the size limitation set by governing body’s (This was discussed in the beginning of the report).

Also the cost of the manufacturing will increase due to mechanical complexity.

12.2.2 Design improvements for the preliminary generator design

Figure

Figure 66 shows the CAD drawing of the preliminary design. The magnets were mounted

pole arrangement, where it creates constant axial magnetic flux distribution between two magnets.

This arrangement increases the electricity generation form the rotating coils (stator

blade tip). After the CAD analysis it was identified due to the outer ring which support magnets

reduces the blade tip aerodynamic efficiency. To solve this issue

the magnets were mounted on the inner surface of the ring in series arrangement. This modification

increases the blade aerodynamic efficiency and high wind energy is captured to generate electricity.

Figure 80 shows the magnetic flux arrangement of the mag

Figure 67

The design is based on wind tip generator concept. However, the magnets are mounted on


power. Also cost of the magnets is higher and mounting it on a rotating component will

reduce the life cycle. Conceptual design 2 wasn’t selected for the final design.

The conceptual design 4 has a two counter rotating blade system, where the sy


Also the cost of the manufacturing will increase due to mechanical complexity.

Design improvements for the preliminary generator design

igure 66: Preliminary CAD Design for the generator

shows the CAD drawing of the preliminary design. The magnets were mounted


angement increases the electricity generation form the rotating coils (stator


reduces the blade tip aerodynamic efficiency. To solve this issue outer ring thickness was reduce and



shows the magnetic flux arrangement of the magnet’s in preliminary design.

67: Magnetic Flux Arrangement in Conceptual Design 3

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The design is based on wind tip generator concept. However, the magnets are mounted on


power. Also cost of the magnets is higher and mounting it on a rotating component will

The conceptual design 4 has a two counter rotating blade system, where the system will


shows the CAD drawing of the preliminary design. The magnets were mounted N-S or S-N


angement increases the electricity generation form the rotating coils (stator-mounted on the


outer ring thickness was reduce and



net’s in preliminary design.

57 | P a g e

13 Final Design (BP)

The final design shows fully assembled wind turbine with bearings and magnets presented as blocks

of steel (cream colour). The slice view of the turbine is used to show display the bearing positions. 3D

Exploded view shows the position each component is attach to.

Figure 68: Front View of the Wind Turbine

Figure 69: Side View of the Wind Turbine

Figure 70: 3D View of the Wind Turbine

Figure 71: Slice View of the Wind Turbine

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Figure 72: 3D Slice View of the Wind Turbine

Figure 73: Exploded View of the Wind Turbine

59 | P a g e

Figure 74: 3D Exploded View of the Wind Turbine

13.1 FEA Analysis (MT) FEA Analysis was carried out for different load condition the wind turbine would experience. The first

FEA was carried out for the forces the wind turbine would encounter on a worst case scenario (60

m/s wing, highest recorded wind speed for UK) to make sure the turbine would be able to survive.

Figure 75: Equivalent Stress

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Figure 76: Total Deformation

As you can see from the above figure, you can notice some deformation in the blades. But safety

factors are well above breaking point proving that the wind turbine would survive a worst case

scenario. If the deformations are plastic (unlikely) the blades would need replacing.

Figure 77: Equivalent Stress

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Another analysis was carried out for more likely high wind situation of 25m/s wind. This level of wind

speed is not an everyday occurrence but it is a likely situation the wind turbine would encounter.

Deformations in blades are slightly above 1mm, well within the elastic limit for Ultra-high-molecular-

weight polyethylene proving the wind turbine is capable of withstanding this level of strong wind

without any problem.

Figure 78: Total Deformation

Further FEA analysing was carried out to find out at what speeds, plastic deformations would occur in

the wings. The results revealed the winds higher than 25 meters per second wind would cause

plastics deformation in blades. To prevent that anemometer will detect the wind speeds above 23

m/s and apply the brakes stopping any damage to the wings/system

When FMEA was carried out on the system, the break mechanism was flag as a system of high risk.

This is due to fails in brake system would be recognised only in the annual maintenance. This is not as

the there are many ways the break system can fail and if the turbine is faced with a high wind

situation after the beaks had failed, that would cause plastic deformation in blades requiring costly

replacements.This was unacceptable and the solution had to be easy on the customer, preferably a

solution that automated requiring no involvement from the residents or maintenance.

The implemented solution is an innovative automated monthly check system. The circuit run through

the utility meter (the model specified in the price list capable of running small programs) is system

that would supply power to the breaks once a month and compare the power generated against the

wind speed registered by the anemometer. When the fail safe check in operation, for any wind speed

above zero, the power generated also should be zero as the check system is powering the breaks. If

the turbine is generating power, that means the beak system has failed and indication would be

displayed of this in the utility meter.As this system is run monthly, chance of damaging situation

occurring is very low.

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13.2 Bill of Material (MT)

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13.3 Blades (BP)

The final design specification:

• NACA 0010 Profile

• Chord length 0.1m

• Each blade with 0.3m span

• Ultra High Molecular Weight Polyethylene material used to manufacture

• 10° angle of attack for Finite blade

• Section cut at the tip for stator

For 6m/s wind speed, 0.3m blade span and 0.05m hub radius, Power available is:

� = A1627D 1 0.5 1 46�8 1 1.225 1 4( 1 0.35�8 = 30.17H

For the given chord length, thickness (t) of the NACA 0010 airfoil shape is 10% therefore the

thickness of the airfoil is 0.01m.

The Planform area is given by: � = , 1 @ = 0.1 1 0.3 = 0.03��

The volume of the blade worked out using the SolidWork tool is 0.204 × 10-3m3

Therefore the Aspect Ratio is: �* = 7IJ = K.�I

K.K� = 3

Mass: � 1 : = 931 1 0.204 1 10N� = 0.189PQ

Reynolds number of the fluid flowing over the airfoil shape: *) = RSTU = �.��1�1K.�

�.VW�1�KXY = 37065

At calculated Re value, the coefficient of lift value curve gradient is approximately 0.1/α

Therefore the Finite Blade CLgradient is given by: ��Z = K.��64 Y[.\1].^]._Y1`1\8

= 0.0598

The finite wing CL is 0.0598 1 10 = 0.598

The Lift: � = 0.5 1 1.225 1 0.598 1 6� 1 0.03 = 0.396a

CD can be worked out using airfoil Cd Value (0.12): �' = 0.12 + b cIK.V�1"1�d = 0.16

Drag Force: & = 0.5 1 1.225 1 0.03 1 0.16 1 46�8 = 0.106a

Torque: . = 0 1 2 = 0.396 1 0.15 = 0.0594a�

Power extracted for 0.5 rps: � = . 1 / = 0.0594 1 42 1 ( 1 0.58 = 0.187H

The Power extraction calculations do show low value because of the estimation made for the rps.

This is because we need experimental or computational analysis to work out the rotational speed.

13.4 Bearings (BP/MH)

Two roller bearings are installed; one holding the hub and the other one holding the upper frame.

The bearings are lubricated to reduce the noise of blade

The bearings need to lubricate in order increase longevity. For the bearing in the hub with blades,

this needs to be lubricated daily. This would be done via a small pump and an oil reservoir. Time

control unit would be a circuit based on a 5

period of time to lubricate the bearing. Power will be drawn from the battery to run this circuit.The

large bearing inside the mast for yaw movement is not rapidly moving and no used long periods o

time. This bearing is lubricated manually ones a year.

13.5 Final Generator DesignThe final generator consists of rotor section and stator section, the specifications and description

follows.

13.5.1 Rotor

(BP/MH)


The bearings are lubricated to reduce the noise of blade rotation.



control unit would be a circuit based on a 555 time control IC that would operate ones a day for small


large bearing inside the mast for yaw movement is not rapidly moving and no used long periods o

time. This bearing is lubricated manually ones a year.

Design (KE) consists of rotor section and stator section, the specifications and description

Figure 79: Final Generator Design

64 | P a g e




55 time control IC that would operate ones a day for small


large bearing inside the mast for yaw movement is not rapidly moving and no used long periods of

consists of rotor section and stator section, the specifications and description

Figure 79 shows the final generator design; the outer ring is defined as the rotor.

• 16 magnets (see Table 7

made out from plastic material to reduce the flux absorption from the magnets. 16 magnets

were chosen in order to gener

cost of the total generator.

• Neodymium magnets were chosen for the rotor, the magnets are made out from Iron and

Boron which is class as the strongest magnets. It creates strong magnetic fluxes,

influence the total electricity generation higher. Most of the renewable appliance used

neodymium magnets.

• Two magnets were place in series in order to create higher flux density around the magnets.

Error! Reference source not found.

• N42 gradeneodymium magnets were chosen due to its optimal balance of magnets strength

and durability for the price.

Shape Magnetic Face: Thickness: Grade: Plating: Performance (Gauss): Vertical Pull (Kg): Slide Resistance (Kg): Max Temp (degrees C): Fixing:

Figure

13.5.2 Stator

Error! Reference source not found.

shows the final generator design; the outer ring is defined as the rotor.

7) are mounted on the stationary ring (355mm inner diameter ring)


were chosen in order to generate more electricity from the generator, also considering the

cost of the total generator.

Neodymium magnets were chosen for the rotor, the magnets are made out from Iron and

Boron which is class as the strongest magnets. It creates strong magnetic fluxes,


Two magnets were place in series in order to create higher flux density around the magnets.

Error! Reference source not found., shows the flux arrangement between two magnets.

N42 gradeneodymium magnets were chosen due to its optimal balance of magnets strength

and durability for the price.

Rectangle 46 x 30mm 10mm N42 Ni-Cu-Ni ( Nickel ) 2700 30 6 80 Araldite/Loctite

Table 7: Magnet specification (35)

Figure 80: Magnetic Flux Arrangement in Final Design

Figure 81: Front View of the Stator

Error! Reference source not found., shows the front view of the stator.

65 | P a g e

shows the final generator design; the outer ring is defined as the rotor.

(355mm inner diameter ring)


ate more electricity from the generator, also considering the

Neodymium magnets were chosen for the rotor, the magnets are made out from Iron and

Boron which is class as the strongest magnets. It creates strong magnetic fluxes, which will


Two magnets were place in series in order to create higher flux density around the magnets.

, shows the flux arrangement between two magnets.

N42 gradeneodymium magnets were chosen due to its optimal balance of magnets strength

66 | P a g e

• It was decided to use removable stator parts to be fitted to the tip of the blade, which will

gives user to replace the stator section and replace with the new part in case of damage to

the stator. In total 6 stators each was fitted to each blade tip and it was connected via screws

to the blades.

• Stator main plate was made out from the plastic material, which has zero permeability and

zero conductivity. These properties enhance the electricity generation form the coils and

reduce loses.

• Since the copper wires were used in stator, due to its excellent electricity conductivity, its

metal properties and low cost.

• Copper wires were winded (10 rotations) in slots on the main stator blade, which increases

the higher winding factor and subsequently increases the electricity generation.

• The copper wire winding pattern was done in a way to satisfy Faraday low, Figure 82 shows

the diagram of the stator winding arrangement for flux direction from the magnet.

• Insulated copper was used to protect the copper from electricity discharge and other

damages. Also this layer of plastic was applied on the side top and bottom face of the stator

to increase the aerodynamic performances on the tip of the blade.

Figure 82: Copper winding vs Flux direction

13.5.3 Final assembly of the generator

Figure 83:Stator Connection to the Blade

Figure 84: Wire Connection from Stator

• Figure 83, shows the stator connection to the blade, where stator is connected by screws to

the blade. Also Error! Reference source not found. shows the wire connection to the main

blade.

67 | P a g e

• Figure 85, Shows the Magnets placement on the outer ring of the rotor.

Figure 85: Magnet arrangement on the ring

Figure 86 shows the stator and rotor intersection when blades rotating.

Figure 86: Cross Section of Stator & Rotator Flux Arrangement in Generator

13.5.4 Power Calculations In order to calculate system electricity generation system flux density distribution needs be studies,

e = ef( gtanN� g H × �2=44=� +H� + ��8� �j k − tanN� g H × �

24= + .8m44= + .8� +H� + ��n� �j .kk

Br(magnet flux density)=2700 Gauss

W (width of the magnet) = 30mm

L (Length of the magnet) = 46mm

T (Thickness magnet) = 10mm

X (distance from magnet) = 2cm (the value was chosen at the furthest point from the magnetic

surface, to get the minimum magnetic flux point at the stator)

N

S

68 | P a g e

Figure 87

Magnetic flux at x distance was calculated, e= 2700

( gtanN� g 30 × 10N� × 46 × 10N�242 × 10N�84442 × 10N�8� + 430 × 10N�8� + 446 × 10N�8�8� �j k

− tanN� g 30 × 10N� × 46 × 10N�242 × 10N� + 10 × 10N�8m442 × 10N� + 10 × 10N�8� + 430 × 10N�8� + 446 × 10N�8�n� �j .kk

B = 9574.12 Gauss = 9574.12 X 10-4T (Tesla)

Stator is wound with copper coils, the length on one wound is 1.3cm on one side and there are 10

rotations of coli going through on one slot. Also there are 7 coils wounds in one stator.

The total length cutting the magnetic flux is can be found from below equation, � = 10 × 7 × 1.3 × 10N� × 2= 1.82m

The area of flux enclosed per second (A) can be found using the below equation, � = 1.82 × V (blade tip linear velocity)

It was calculated that the angular velocity4/ = 3.142?/p8 of the turbine blades at the minimum

operating wind speed of 6 m/s. The relationship between angular velocity and linear velocity (V) can

be found from the below equation,

: = / × *42?qr+p = 3.14 × 2? pj × 350 × 10N� = 1.099� p⁄

emf charge per second4t8 can be found from equation (one stator), t = � = � × e = 1.82 × 1.099 × 9574.12 × 10Nu = 1.91: t = )�v � = :rw?Q)

In order to find the current flowing through the circuit resistance of copper wires need to be

calculated. The resistance was calculated by using below equation,

R= Resistance

L= Length of the wire

K=Resistivity of copper wire (Copper = 1.73 X 10-8)

A= Cross sectional area of wire (0.6 mm copper wire was used)

R = L × P� = 1.82 g 1.73 × 10NW

( × 40.6 × 10N�8�k = 0.0278z

The current flow in the circuit can be found from the below equation,

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I = t4�8* = 1.91

0.0278 = 68.70�

The power generated from one stator can be found from the below equation, � = :| �� = 1.91 1 68.7 = 131.217H

The system is equipped with 6 stators, to find the total power generate from the system the P1 need

to be multiplied by 6. � = 131.217 1 6 = 787.30H

13.5.5 Power Curve The power curve of the system evaluated to study the power output for different wind speeds.

However it was unable to find the relationship betweenwind speed and blade angular velocity. So

the power curve was plotted to different blade angular velocities.

13.5.6 Method Voltage or coil e.m.f generated due to the magnetic flux can be calculated by below equation, t = � = :�e t = )�v � = :rw?Q)

V=blade tip linear velocity

L=length of the wire (0.182m)

B=magnetic flux (9574.12 X 10-4T) t = � = : 1 9574.12 1 10Nu 1 1.82 = V 1 1.7424

Also the liner velocity and the angular velocity related by below equation, : = / 1 2 = / 1 350 1 10N�

r =Radius of the area covered by blades P = vI P= Power

v=Voltage

I= Current

Where,

I = �*

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Po

we

r O

utp

ut

(wa

tts)

//// ---- Blade Angular velocity (rad/s)

Power Curve

70 | P a g e

R=Resistance

By replacing I in equation,

P = v 1 �* = ��

* = 4: 1 1.74248�0.0278 = 4/ 1 350 1 10N� 1 1.74248�

0.0278 = 13.39/�

P = 13.39/�

13.5.7 Generator circuit (stator to blade point)

13.6 Power Management (MT) Customer has the option of choosing an arrangement that suits his lifestyle, but for this wind turbine,

below arrangement is provided as the standard setup. Out of the typical arangemenbts, we belive

this arrangement with combination with the wind turbine would most benificial for the cost.

Figure 88: Final Design Power Management System

71 | P a g e

1) Wind turbine tower would be the new innovative wind turbine design presented in this report.

2) Wind turbine control unit looks after charging the batteries. This prevents the batteries from

overcharging (providing power when the battery is full reduces the battery life) and undercharging

(draining the battery below 20% will irreversibly reduce the battery capacity). It charges the batteries

at the earliest opportunity, minimising battery cycling (charging and discharging rapidly).

The charge controller and voltage regulator provides the capability for maintaining the state of

charge for 12V or 24V storage batteries. The charge controller circuit performs as a fully automatic

voltage regulator. It has been designed for unattended site operation and is supplied in a

weatherproof plastic enclosure, suitable for mounting on a vertical pole or on a wall.

The charge controller constantly monitors the battery voltage and if required the batteries are

allowed to charge. As the float voltage is approached a load is applied to dissipate power. The charge

controller continues to monitor the battery voltage and if it subsequently drops below a threshold

then the load is disconnected and the charging action will resume.

3) Bator yank stores the energy generated from the wind turbine for the purpose of distribute it to

the loads when necessary. Standard batteries provided are two non-sealed deep cycle batteries of a

capacity of 75 Ampere Hour at 12 volts. Deep cycle batteries are very durable (needs replacing about

every six years) and can handle cycling of leads (charging and withdrawing rapidly). Non sealed

batteries are used as it allows the user to replenish the fluid inside themselves rather than replacing

the battery. Non sealed batteries last longer than sealed batteries but requires replenishing fluids

about every six months.

The two batteries supplied are able to power a typical refrigerator for two consecutive days.

Customer can have increased capacity batteries installed if they wish to do so.

4) The inverter converts the battery stored direct currant to alternating current of 230 volts which is

what the typical grid supply would be. Being a grid tie inverter this not only provide AC currant for

the refrigerator, it is also capable of exporting the excess electricity in to the national grid under the

Feed-In-Tariff. The customer would be paid 16 pence per kilowatt hour exported to the grid.

This specific model of inverter has two power outlets, so the customer can chose between exporting

the extra power and running a another appliance such as a washing machine when too much power

is generated from the wind turbine.

5) Utility meter provides the customer with important information about the system performance.

Utility monitor displays the amount of power generated, power exported and battery level.

Customer can use this information to manage the power accordingly if necessary.

13.7 Maintenance (ALL)

13.7.1 Generator Normally magnets maintain its magnetic properties, so replacement of magnets is very rare.

However the Neodymium magnets used in the generator is exposed to environment. The magnets

are made by using NdFeB is very reactive and it might cause corrosion. It also has a low curie

temperature so temperature is concern over the time (high sunlight, snow and rain). Also if there is a

crack on magnets the magnetic power losses. Yearly inspection would be a solution to check

magnets, since there is no such a formula to find magnetic life time.

72 | P a g e

Stator coils are subjected to vibration due to blade tip acceleration. Also the stator is exposed to the

temperature changes and high wind speeds. So the durability of stator might reduce. The inspection

of stator should be carried out annually.

13.7.2 Tips for long lasting power management system Corrosion increase resistance in delivering power causing power losses. It is advised that the

customer take precautions to avoid/minimise corrosion in the system. A method such as covering the

exposed metal with petroleum jelly is widely popular, effective and inexpensive.

The batteries used are flooded batteries, which needs refilling with deionised water every 6 months.

Batteries lose its ability hold power with cold temperatures. It is advised the batteries are stored in

room temperature.

Letting the battery be drained fully cause definite and irreversible loss of power storage capability.

Provided power regulating system is capable of detecting such events and disconnecting the system.

It is also capable of detecting overcharging events and disconnecting the charging supply from the

battery bank.

The table below highlights all the components that are suited for manufacturing using the

methods detailed above, and the justification for choosing them.

14 Manufacturing (MH)

Component Manufacturing Method Justification

Hub (Main body) Casting/ moulding Good dimensional accuracy

needed, intricate part details

Hub Centre Rod Extrusion or Drawing Relatively simply part but

strength required

Hub Cone Compression Moulding

Part is of a simple design,

therefore can be moulded at

a relatively high rate

Generator Housing Die Casting

Complex shape which

requires a very high

tolerance of finish in order to

house magnets in place

Generator Frame Support Sand Casting

Moderate shape, large

volumes required due to 3

parts per turbine

Brake Disc Sand Casting

Simple shape, moderate

dimensional accuracy is

sufficient

Blades Injection Moulded

Complex shape, hollow

structure, high production

rates at 6 parts per turbine,

high strength plastics to be

used

Mount: Mast Forging or extrusion/drawing Relatively simple shapes and

constant hollow sections in Tail: Shaft Forging or extrusion/drawing

73 | P a g e

centre

Mount: Base Forging

Due to varying dimensions

(non linear), forging is the

best method of manufacture

Tail: Vane Casting

Heavy weight due to

counterbalancing function

and therefore high accuracy

not required but casting

presents the easiest

production option

15 Business Model Evaluation of wind turbine (MH)

In order to create a viable business model to design and produce the wind turbine, it is first

necessary to understand the costs involved with each part of the system. The table below

gives a guide to the material costs for the turbine. It is important to note the following points

that form the basis of the business model in this section:

• The business model is developed for an initial production of 20,000 units

• Material costs are estimated using the volume given in the CAD software and then

the mass obtained through the density of the material of the component and CES

Edupack software to obtain price per kilogram.

• Manufacturing costs are to be discussed separately which does not take into account

material costs used to make the component

• Costs for each standard parts are obtained at a retail price point, whereas in actual

production, the cost for the same item would be less as a higher volume will attract

a significant discount

15.1 Material Costs

Material Costs

System Sub-

System

Unit Cost

(£) Comments/Source

Turbine Blades

£2.22 6 Turbine blades

Hub

Hub (Body) £5.66

Centre £17.28

Cone £0.40

Generator

Housing £3.39

Frame

Support £1.78

Magnets £227.40 12 magnets costing £18.95 each

Coils £10.50 8m of coils

74 | P a g e

Wires £2.99 From blade tip to turbine: 10m,

http://www.maplin.co.uk/equipment-wire-16-0.2-6197

Brushes

Braking

System

Disc £22.68 http://www.kartpartsuk.com/product.php?id=1299

Calliper

Pads £7.95 http://tinyurl.com/cxc7dha

Power

Management

Battery x2 £160.00 £80 per battery. The design requires 2

(http://tinyurl.com/b9eex7g)

Grid Tie

Inverter £60.00 http://tinyurl.com/ahkmxke

Shunt

Regulator £45.00 http://tinyurl.com/b2wb276

Power

Output

Monitor

£45.00 http://tinyurl.com/acllfea

Wires £16.00

Mounting

System Mast £1.12

Carbon Steel prices obtained from CES Edupack at

£0.045 per kg

Base £4.14

Tail Shaft £0.57

Vane £13.46

Other Hub

Bearing £28.96

Mast

Bearing £42.36

Miscellaneous

£30 These costs include nuts, bolts and other items

Total Unit

Cost £748.86

Final Unit

Price £524.20

Price includes 30% reduction for bulk buying

components

As seen in the above table, the total unit cost for the material of the turbine is nearly £750. As

mentioned previously, this figure is calculated at retail cost value and also material prices per kg

obtained from CES Edupack.

For a production rate of 20,000 units, a wholesale price can be agreed with the manufacturers of the

components within the turbine. A 30% markup on price is generally accepted and if this is factored

into the cost model, it reduces to approximately £525.

Before we can determine the retail price for the turbine, we have to consider all other cost factors

involved within the business and also consider the current market conditions at which we need to

sell the turbine at. These costs can be broadly categorized into the following:

75 | P a g e

• Manufacturing: Machines, moulds, raw material, Packaging

• Marketing – Advertising and promoting costs for the turbine

• Premises – Rent and utilities to produce the product

• Labour – Wages and administrative costs

• Operational – I.T., Stationary, Security systems

15.2 Manufacturing Costs The manufacturing costs for the turbine include all costs that are associated with the making of the

product. Although the machines will take up the majority of the costs, there are various other costs

to consider too.

Typically, a new injection-moulding machine would cost in the region of £30,000. As highlighted in

the manufacturing process stages, an injection-moulding machine would also have other costs

associated such as moulds and pellets.

It is aimed to produce the blades and the hub through injection moulding. Although initially the cost

per mould might seem quite high, it is important to understand the price per piece, as production in

high volumes will significantly decrease this value. A rough guide to injection mould prices can be

found at:

Hub: Due to its complex shape with many features, the tooling cost will be fairly high. It is estimated

to be around £20,000. This would mean the cost per hub would only be £1.

Blades: Since the blades are a relatively simply part to produce in comparison, it is estimated to cost

around £10,000. This would mean the cost per hub would only be £0.50.

Pellets: Since the working material of the machine is pellets, it is important to choose them carefully.

Initial research suggests that a price of $1000-2000 per tonne is reasonable. For production

purposes, it can be estimated that 2 tonnes worth of material to be kept and used. This would cost

an estimated £2680 if higher estimates is to be used.

Other manufacturing cost will include cost of sand casting and moulds, forging machines, coolants

and other liquids. A conservative estimate for all such machinery would be £300,000.

This gives a total of nearly £400,000 for machinery costs. Material costs will also have to be

considered for all machining operations which are not plastics. A budget of £200,000 will be set for

this which would produce a final cost of £600,000.

15.3 Marketing Costs The marketing budget for any small business is not a topic that has a clear answer. This is because it

can vary a great deal with the type of product, its industry and also required return levels. Image

Works Creative mentions that it could be around 5-6% of initial revenue of the company for a

company that makes between £10-100 million a year. It should however be noted, as pointed out by

Paul that a start-up company would want to spend more as it would want to increase its presence in

the market.

In order to gain a significant presence in the marketplace, the following marketing streams should be

explored:

• Online Advertising: There are currently many forums and websites that offer information and

advice regarding renewable and alternative energy products that are in the market. They are

also reviewed according to their performances. An annual budget of £4,000 could bet spent

for such advertising which could increase depending on the success of the campaign.

• Social Media: Social media advertising has grown in recent years and this should be

capitalized upon. It is a good method of promoting the business although the results of such

76 | P a g e

promotions are not always clear. A nominal budget of £1,000 can be spent on developing a

campaign to promote the product

• Magazine: Many renewable energy magazines exist in the UK market and they are also

popular ‘sub’ topics of consumer advice magazines. A budget of £5,000 could be spent on

developing a printed ad campaign in this medium.

• Paper: Paper advertising has enormous potential as it has a very firm user base with a very

wide demographic. The same ad campaign used for magazines could be run in national or

local newspapers. Since newspaper ads are more costly, a £10,000 per year budget could be

set for this.

Therefore, initially a total budget of £20,000 per annum is to be set up for advertising and

marketing the product.

15.4 Premises Costs Premises costs are considered to be a combination of the rent and utilities for the premises in which

the manufacturing will be taking place.

If the business is considering manufacturing most of the components on site as well as assembly, a

10,000 sq. ft. site is considered sufficient. This is roughly equivalent to 930 square meters (300 x

300m). Initial research suggests that it would cost £50,000 per annum to rent this amount of space

within the outskirts of London.

Utility costs can vary by a large amount within such a warehouse space as it entirely depends on the

amount of equipment that would be installed within it. Since this cost model will assume that most

of the components will be manufactured in house, it can be expected to be higher than average.

Other factors that can also have an effect are the amount and level of insulation protecting the

premises and the energy efficiency of machines/lighting etc.

An initial research suggests utility costs at £1 per square foot per year. Since there are a lot of

machines used within the building, it would be wise to estimate this at around £1.25 per square foot,

which gives a total of £12,500 per year for utilities.

Therefore the total cost for premises would be £62,500 per annum.

15.5 Labour/staffing Costs Labour/staffing costs have been estimated based on average annual wages in the UK. The amount of

staff is an estimated number in order to produce an initial 20,000 units and more staff can be hired

based on the requirements of the business in the future.

Position Average Annual

Salary

Amount

of staff

needed

Annual

Cost for

position(s)

Source

Assembly line

worker

£15,000 4 £60,000 http://tinyurl.com/conleva

Skilled Labour £24,000 5 £120,000 http://tinyurl.com/az7lcel

Administrative

Assistant

£15,000 1 £15,000 http://tinyurl.com/ablfg3r

Security £15,000 1 £15,000 http://tinyurl.com/bbzmsrz

Supervisor £25,000 2 £50,000 http://tinyurl.com/akm5dmb

Employee Liability Insurance £5,000

77 | P a g e

Pension + other benefits £40,000

Total Annual cost £305,000

The table above shows an estimated cost for labour and staffing per annum. The job positions were

determined to fit the type of business requirements.

• Assembly line worker – Assembly line workers are required once the products are

manufactured, to assemble the components together as well as finish packaging

• Skilled Labour – Skilled labour is required to operate the casting and moulding machines as

well as producing parts which require any kind of work done to it

• Administrative Assistant – As with any office, an administrative assistant is required to carry

out all administrative duties and assist with paperwork and other employee enquiries

• Security – Since the business will be holding high value items, a security guard is needed at

the premises to protect it as well as its employees

• Supervisor – While the production is being carried out, 2 supervisors are needed, each at the

manufacturing and assembly sections, to ensure the quality of the product is upheld and the

production runs on schedule and budget.

15.6 Operational Costs Operational cost of the business can account for a sizeable proportion of costs, but are necessary to

run a successful business.

Type Subtype One-off costs

(installation,

etc)

Annual

Cost

Total Initial

Cost (One-

off +

Annual)

I.T. Computer

Systems

£25,000 £5,000 £30,000

Staff Training £2000 £1,000 £3,000

Maintenance

/Support

£5,000 £5,000

Security

Systems

CCTV

Cameras

£2000 £2,000 http://www.icctvsystems

.co.uk/Item/izeus16_hdi

psystem1

Initial

Installation

£400 £400

CCTV

Monitoring

£1,200 £1,200

Premises

Security

£2,000 £2,000

Stationary Initial Cost £500 £500

Total annual costs for year 1 £44,100

Cost Summary for turbine manufacture:

Type Cost

Manufacturing £600,000

Marketing £20,000

Premises £62,500

Labour/Staffing £305,000

78 | P a g e

Operational £44,100

Total Cost £1,031,000

15.7 Revenue Since the business would be classified as a start-up, the only expected income is from product sales.

The cost estimates were carried out for an annual production basis and an estimate of the annual

production for the turbine in the first year is set to be 20,000.

Given the market conditions and current demand for wind turbines, it is not realistic to sell 20,000

turbines within the first year. In order to be conservative, 10,000 units are to be estimated as an

initial sales target for the first year.

It is of paramount importance to price the turbine according to current demand and market

conditions. As a new entrant to the market and as specified in the PDS, this turbine is to be sold at a

lower cost than current similar models. During the initial literature review, it was highlighted that

similar turbines will cost upwards of £2,000, which is a substantial initial investment. Therefore it is

reasonable to be priced at £1,500, which is lower than the current average market price for similar

turbine models.

Therefore, Total Revenue = £1000 per unit x 10,000 units = £15,000,000

15.8 Profit Margins

The total annual cost for the turbine production is £1,031,000 and this is based on producing 20,000

units. This gives a unit cost for production of: £103100/20,000 = £51.55

The total cost per unit is calculated as a ‘per unit’ cost which is added to the turbine. This includes all

the costs detailed in previous sections, but in addition, includes the material costs per unit. Since we

have a material cost for producing the turbine of £524.20, we can add the production cost per unit in

order to work out the profit margin per unit sold.

Therefore total cost per unit: £524.20 + £51.55 = £575.75

Projected Profit per unit = Turbine selling price – total cost per unit = £1,500 - £575.75 = £924.25

Once the profit per unit is calculated, a total projected profit value could be found for the year:

Total Projected Profit = £924.25 x 10,000 units = £9,242,500

While these values included are purely projected values, they are based on conservative estimates. It

is also important to note that while the selling price of £1,500 is a low value in comparison to current

market products, in order to gain initial market share, could be sold at a discounted price of around

£1,000.

79 | P a g e

Failure Modes Effects Analysis

Process or Product Name:

AE5 Wind Turbine

Prepared by: Maheemal Pag

e:

of

Process Owner:

Maheemal/Mishkath/Bhavedeep/Kalinga

FMEA Date (Orig):

08/03/2013

Rev.

1

Key Proce

ss Step

or Input

Potential Failure Mode

Cause

SE

V

Outcomes

OC

C

Current Controls

DE

T

RP

N

Actions Recommend

ed Resp.

Actions Taken

SE

V

OC

C

DE

T

RP

N

What is the

Process Step

or Input?

In what ways can

the Process Step or

Input fail?

What is the cause for

the Variables?

How Severe is the

effect to the

customer?

What are the

Outcomes Resulting

From This?

How often does

cause or FM

occur?

What are the existing

controls and procedures that prevent either the

Cause or the Failure Mode?

How well can

you detect

the Cause or the Failure Mode?

What are the actions for

reducing the occurrence

of the cause, or improving detection?

Who is Responsibl

e for the recommended action?

Note the actions taken. Include dates of completi

on.

Centre Facture Total failure, Excessive Vibration

9

Improper maintenance

1

Routine Annual Check

1 9

No Further Action

Maintenance Crew

9 1 1 9

Centre Abrasion Noise, Low Power Output

7 Improper Maintenance

1 Routine Annual Check

1 7 No Further Action

Maintenance Crew

7 1 1 7

80 | P a g e

Cone Fracture Blades Becoming Lose

8 Improper Maintenance



Maintenance Crew

8 1 1 8

Cone Screws loosing due to vibration

Blades Becoming Lose

8

Vibration

1

Opposite Directionally Tapped Screws (3 Screws in each direction)

5 40

Annually Check Screws For Tightness

Maintenance Crew

8 1 5 40

Break Disk

Fracture Ineffective Breaks in a Over speed Event

9

Excessive Vibration

1


1 9

No Further Action

Maintenance Crew

9 1 1 9

Break Disk

Breaking at attachment point

Ineffective Breaks in a Over speed Event

9

Excessive Vibration, Misalignment of Callipers

1

Routine Annual Check 1 9

No Further Action

Maintenance Crew

9 1 1 9

Break Disk

Wear and tear


9

Long Term Use

1


1 9

No Further Action

Maintenance Crew

9 1 1 9

Break Disk

Power failure to Callipers


9

Power Supply System Failure

1

Routine Annual Check 9

81

Automated Fail Check (Explained in the Report, Run Monthly)

Customer

9 1 9 81

Break Disk

Vibration casing misalignment in callipers and pad


9

Excessive Vibration

1


3 27

No Further Action

Maintenance Crew

9 1 3 27

Blades Fracture Low Power Output 5

Excessive Vibration 1



Maintenance Crew

5 1 1 5

81 | P a g e

Blades Misbalancing

Excessive Noise, Fracture Blades and Other Components

9

Foreign Object Damage, Excessive Vibration 1

Routine Annual Check, Visual Checks by Customer in case of Excessive Noise

1 9

No Further Action

Maintenance Crew, Customer

9 1 1 9

Blades Deformation over time

High Heat, Long Lasting High Wind Situation

4

Low Power Output 1


No Further Action

Maintenance Crew

4 1 1 4

Blades Bird strike

7

Fracture Components, Excessive Noise

1

Visual Check By Customer

1 7

No Further Action

Customer

7 1 1 7

Frame Support

deformation over time

High Heat, Long Lasting High Wind Situation

8

Damage to Blades

1

Visual Check By Customer

1 8

No Further Action

Customer

8 1 1 8

Frame Support

fracture at joint,

Excessive Vibration

7

Misalignment Between Blades and Magnets Resulting in Low Power Output

1


1 7

No Further Action (as 2 Support Rods can effectively Hold the Frame Safely)

Maintenance Crew

7 1 1 7

Frame Support

vibration cracks

Excessive Vibration

7

Misalignment Between Blades and

3

Routine Annual Check 4

84

No Further Action

Maintenance Crew

7 3 4 84

82 | P a g e

Magnets Resulting in Low Power Output

Frame deformation due to vibration

Excessive Vibration

7

Misalignment Between Blades and Magnets Resulting in Low Power Output

3


2 42

No Further Action

Maintenance Crew

7 3 2 42

Base failure of screws,

Metal Fatigue

9

Total Failure

1

Replacement of Screws Every 10 Years

3 27

No Further Action

Maintenance Crew

9 1 3 27

Base fracture, Excessive Vibration 9

Total Failure 1



Maintenance Crew

9 1 1 9

Base joint between mast and base failing

Excessive Vibration

9

Total Failure

1


No Further Action

Maintenance Crew

9 1 1 9

Tail weld fracture

High Gust

5

Loss of Yaw Control, Low Power Output

1


1 5

No Further Action

Maintenance Crew

5 1 1 5

Tail bird strike

1

Insignificant Deformation

1


1 1

No Further Action

Maintenance Crew

1 1 1 1

83 | P a g e

Tail Support

weld fracture,

High Gust

1


1


1 1

No Further Action

Maintenance Crew

1 1 1 1

Hub fracture at joints,

Excessive Vibration 9

Total Failure 1



Maintenance Crew

9 1 1 9

Hub failure at joint between bearing and hub

Excessive Vibration

9

Total Failure

1


No Further Action

Maintenance Crew

9 1 1 9

Base Mount Bearing

fail at the joint,

Excessive Vibration

9

Total Failure

1


1 9

No Further Action

Maintenance Crew

9 1 1 9

Base Mount Bearing

bearing freeze up

Extreme Cold Temperature

4


1

No Action

1 4

No Further Action

4 1 1 4

Base Mount Bearing

pitting of the roller bearings

Extreme Cold Temperature

7

Noise, Wear and Tear

1


1 7

No Further Action

Maintenance Crew

7 1 1 7

Magnet

thunder strikes

6

Reduced Power Output


3 72

No Further Action

Maintenance Crew

6 4 3

72

Magnet

vibration wear off, ,

Vibration 2

Reduced Power Output


3 24

No Further Action

Maintenance Crew

2 4 3

24

16 Conclusion (KE/MT)

All the calculation show that this project would be a success and it will be more than cap

providing operating power to a refrigerator without needing support from the grid. The next stage of

the project would be to protect this design from being copied. We plan to do so by applying to a

patent UK and International. Our research shows th

the prototype, felid trials and manufacturing stages with confidence with the patent pending (As

international patents can take up to six years to process)

16.1 Design Specification

Rated Power

Applications

Solutions

Architecture

Blade Material

Blade type

Generator Type

Cut In Speed

Cut Out Speed

Cost

Weight

Overall Height

Span Diameter

Number of Blades

Inverter

Safety System

Tower Type

Tower Height

Tower foundation

Operating Temperature Range

Warranty

(KE/MT)

All the calculation show that this project would be a success and it will be more than cap



patent UK and International. Our research shows this has never been done before, so we can go to


international patents can take up to six years to process)

Design Specification

Figure 89

��. ��(rated at wind speed of 6m/s)

Rural Domestic, Small Holding, Agricultural, Commercial,

Telecoms, Public

Grid tied, Battery Charging, 12V

Up wind, 6 blade rotor, self-regulating

Ultra High Molecular Weight Polyethylene

Fully optimised aerofoil ensuring maximum yield & minimum

noise

Blade Tip permanent magnet generator

6 m/s

25 m/s

£1500.00

150kg

0.7 m

0.3m

6

Grid-tie inverters

Electrically actuated brakes, automated monthly brake checks

Free-standing

2m (from roof )

Root/ Pad

-20 °C - +50 °C

3 years

84 | P a g e

All the calculation show that this project would be a success and it will be more than capable of



is has never been done before, so we can go to


Rural Domestic, Small Holding, Agricultural, Commercial,

Fully optimised aerofoil ensuring maximum yield & minimum

Electrically actuated brakes, automated monthly brake checks

85 | P a g e

17 Works Cited 1. www.home-energy.com. [Online] [Cited: 06 02 2013.] http://home-energy.com/int/ebv200.htm.

2. Honeywell wind turbine is a breeze to run – and a light one at that. Gizgam. [Online] [Cited: 06 02

2013.] http://www.gizmag.com/earthtronics-honeywell-windgate-wind-turbine/11990/.

3. www.microstrain.ie. [Online] [Cited: 06 02 2013.] http://www.microstrain.ie/hannevind.html.

4. www.bettergeneration.co.uk. [Online] [Cited: 06 02 2013.]

http://www.bettergeneration.co.uk/wind-turbine-reviews/windsave-ws1000-wind-turbine.html.

5. www.bergey.com. [Online] [Cited: 06 02 2013.] http://bergey.com/products/wind-turbines/10kw-

bergey-excel.

6. www.windenergy.com. [Online] [Cited: 06 02 2013.]

http://windenergy.com/products/skystream/skystream-3.7.

7. better generation. [Online] [Cited: 04 02 2013.] http://www.bettergeneration.co.uk/wind-turbine-

reviews/honeywell-wt6500-wind-turbine.html.

8. www.renewabledevices.com. [Online] [Cited: 06 02 2013.] http://renewabledevices.com/rd-swift-

turbines/overview/.

9. Reid, Steve. Wind and Wind Energy. NIWA - Water & Atmosphere. [Online] 2005. [Cited: 20 01

2013.] http://www.niwa.co.nz/publications/wa/vol13-no4-december-2005/wind-and-wind-energy.

10. Is wind power right for you? Energy Matters. [Online] [Cited: 20 01 2013.]

http://www.energymatters.com.au/renewable-energy/wind-energy/wind-power-guide.php. ISO-

8859-1.

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18 Appendix-A (ALL)

18.1 Figures

(ALL)

Figure 90: Power curve for Energy ball V200

Figure 91: Power curve for WT6500

Figure 92: Windon Power Curve

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Figure 93: Power Curve for Bergey Excel

Figure 94: Power Curve for Skystream 3.7

Figure 95: Windsave Power Curve

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Figure 96: Swift Power Curve

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18.2 Flow chart for varying conditions (MT)

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19 Appendix-B (MT)

Technical Drawings

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20 Appendix-C (ALL)

Weekly Review Sheets