Kun Shan University

Undergraduate school of Mechanical Engineering

Final Project

A New Venturi Type - Bladeless Wind Turbine Design Coupled to a Permanent Magnet Generator For Small

Scale Electricity Generation

Undergraduate Students: Rodyn Gilharry 吉洛庭

Carlos Campos Saravia 甘伯斯

Advisor: Song-Hao Wang 王 松 浩

June, 2014

Table of Contents

 

Abstract ..........................................................................................................................................1 

1. Introduction ...............................................................................................................................2 

1.1 Permanent Magnet Direct Drive Generator ............................................................................5 

1.2 Negative Effects of Wind Turbines ..........................................................................................7 

1.2.1 Visual Impact ........................................................................................................................7 

1.2.2 Infrasound and Noise ............................................................................................................8 

1.2.3 Impact on Wildlife especially birds .......................................................................................9  

1.2.4 Shadow Flicker and Blade Glint ...........................................................................................10 

1.2.5 Electromagnetic Radiation and Interference ......................................................................10 

1.3 Advantages of Venturi ‐ Type Design .....................................................................................11 

2. Theory ......................................................................................................................................12 

2.1 Wind Power ...........................................................................................................................12 

2.2 The Venturi Tube ...................................................................................................................13 

2.3 The Permanent Magnet Generator .......................................................................................15 

3. Ansys Settings ..........................................................................................................................16 

4. Design Procedure .....................................................................................................................18 

4.1 Wind Cone Selection...............................................................................................................18 

4.2 DESIGN 1 ................................................................................................................................23 

4.2.1 Addition of a Venturi Tube ..................................................................................................24 

4.2.2 Increasing the Working Area ..............................................................................................28 

4.2.3 Final DESIGN 1 .....................................................................................................................31 

4.3 DESIGN 2 ................................................................................................................................34 

5. Permanent Magnet Generator Design .....................................................................................37 

6. Conclusion ................................................................................................................................39 

References ...................................................................................................................................40 

Appendix  A ..................................................................................................................................44 

Appendix  B ..................................................................................................................................46 

Appendix  C ..................................................................................................................................47 

Appendix  D ..................................................................................................................................48 

Appendix  E ..................................................................................................................................50 

Appendix  F ..................................................................................................................................51 

Appendix  G ..................................................................................................................................52 

Appendix  H ..................................................................................................................................53 

Appendix  H1 ................................................................................................................................54 

Appendix  H2 ................................................................................................................................55 

Appendix  H3 ................................................................................................................................56 

Appendix  H4 ................................................................................................................................57 

Appendix  H5 ................................................................................................................................58 

 

 

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Abstract:

This Paper presents a design of a bladeless wind turbine that uses the Venturi Tube/Bernoulli's principle to amplify the ambient wind speed so that it may drive a permanent magnet generator. Thus producing energy in areas where harvesting wind power would have not been profitable before. This design incorporates a direct drive method so that the total number of moving parts are reduced, eliminating the need for a gear box and making the maintenance of the wind turbine much easier. The magnet generator used is a coreless one, reducing magnetic drag (cogging torque) thereby increasing the energy output. This design also address many of the environmental concerns presented by conventional wind turbines such as the production of noise and the threat to birds and wildlife.

 

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1. Introduction:

Today most of the electricity produced in the world is obtain from the burning of fossil

fuels (see figure 1). This source of energy is not only non-renewable and rapidly depleting but

also causes numerous environmental concerns that in the long run cause more problems than

benefits. Now, because global warming is no longer a warning but an occurrence and its

disastrous effects are being felt globally, most countries are investing more heavily in green

energy. Green energy is obtained from renewable sources and even though they are described as

'Green' that does not necessarily mean that they have no environmental impact. Nuclear energy

produces radioactive waste that takes thousands if not millions of years to decompose. They have

to be stored in a secure facility in boxes that are tested to be 'indestructible', all of this leads to a

lot of spending in the R&D departments. Hydro power is also another great source of energy but

is accompanied by numerous environmental effects. Large Valleys and fields need to be flooded,

completely eliminating the ecosystems in those areas, and also with water shortages and longer

droughts occurring each year, water might soon become too valuable for it to be used as a source

of green energy. The best other renewable energy source to be exploited is Wind Energy. Wind

energy is a very clean energy that poses little environmental risks as can be seen in Table 1.

Fig. 1. Comparison of Energy Sources and Their Usage in Terawatts, 1965-2005 [3]

 

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Table 1

Comparison of habitat impacts of wind energy to other energy sources [3].

The world's energy demands are ever increasing (see figure 2), and so the demand for

more reliable and efficient wind turbine systems are also increasing. The clean energy trend that

started mainly in the United States and Europe is now spreading to countries all over the world

with millions of watts of clean energy being supplied to large cities (see figure 3).

Fig. 2. World Energy Demand Growth [3]

 

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Fig. 3. Top Ten Wind Power Generating Countries by December, 2011 [2]

One of the main advantages of wind power generation systems in their adaptability, they

can be built in for industrial purposes and many large turbines can be built together side by side

forming large wind mill fields, or they can be made as smaller individual units for domestic use.

This way towns, villages, farms, factories or any person in a remote location can install their own

domestic wind mill and harvest wind power. Individual power units or domestic power units

might be one way in which energy is generated in the future removing the numerous problems

associated with a centralized power station and eliminating miles of power cables that are

currently criss-crossing large cities and towns. Most of the recent designs of small scale wind

turbines incorporate the uses of a Permanent Magnet generator.

 

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1.1 Permanent Magnet- Direct Drive Generator

About 1.6 billion people lack access to electricity and many of these are in rural areas so

there is a large potential market for isolated small wind turbines, these wind turbines are usually

less than 5KW and are located in remote areas which are not connected to the main power grid

system [30] [17]. Permanent magnet generators are suitable for small scale wind turbines

because they have a high efficiency, they are categorized into two types because of the direction

of the magnetic flux, the radial type and the axial type (see figure 4).

Fig. 4. The direction of the magnetic flux from the rotor of axial and radial types [22].

Permanent Magnet generators are usually more efficient because of the fact that field

excitation losses are eliminated resulting in major rotor loss reduction, thus high power density is

obtained. Also PM generators have small magnetic thickness which results in smaller dimensions.

For the sake of mechanical simplicity most designs incorporate a direct couple or direct drive

system thereby eliminating the need for gears or complex mechanical parts, eliminating gearbox

failures prolongs the life of the wind turbine and also saves on cost and weight [14] [16] [22] .

Figure 5 shows the general setup of an axial flux permanent magnet generator.

Fig. 5. General arrangement for an Axial Flux Permanent Magnet Generator [17]

 

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However, PM generators also have some disadvantages, they do not posses field

excitation control and therefore voltage regulation can be a problem. Using external voltage

control such as large capacitor banks or choosing the turns on the stator windings properly to

produce the anticipated required nominal voltage can be used to correct the problem. Also since

the permanent magnet fields cannot be turned off, there exists the risk of excessive currents in

the case of an internal fault. This could also be corrected by the incorporation of a turbine

governor or dynamic breaking [19]. The Comparison of a PM generator to a conventional wound

rotor type is shown below in Table 2.

Table 2.

Comparison of Wound Rotors and PM Generators

Another Disadvantage of PM generator is Demagnetization. The magnets can become

partially demagnetized by over current or excessive temperature or a combination of both [30].

 

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1.2 Negative Effects of Wind Turbines

Even though wind turbines are not thought to pose any major environmental hazards,

there has been extensive studies done on the allegation of Noise Pollution and other assessments

on the effects of large wind turbines on people and their surrounding area. Studies have

concluded that the main negative effects can be listed as follows:

(1) Visual Impact

(2) Infrasound and Noise

(3) Impact on Wildlife especially birds

(4) Shadow Flicker and Blade Glint

(5) Electromagnetic Radiation and Interference

1.2.1 Visual Impact

Although the idea of wind energy is generally well received in public, there is still a

tendency for people not to want a wind farm located close to where they live or other residential

areas. Papers written by Saidur [3] indicate that the visual impact varies according to the wind

energy technology such as colour or contrast, size, distance from residencies, shadow flickering

and the times when the turbines are operational. Recently more and more larger wind turbines

are being built so that they reduce their carbon footprint, this adds to the visual impact since the

towers become more visible from a further distance. The increase of wind turbine size over the

years is represented in Figure 6 with 20MW towers predicted to be built in the near future.

 

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Fig. 6. Growth in size of commercial wind turbines [11]

1.2.2 Infrasound and Noise

The most critical environmental impact of wind turbines is noise pollution. Noise is

defined as unwanted sound and sound is characterized by its sound pressure level (loudness) and

its frequency (pitch) which are measured in decibels (dB) and Hertz (Hz), respectively. The

normal human hearing range is from 20Hz - 20,000Hz and anything below 20Hz is referred to as

infrasound [3] [29] [31]. Wind turbines generate sound through mechanical and aerodynamic

means.

The aerodynamic noise is present in all frequencies from infrasound to the audible range,

producing the characteristic 'swishing' sound. Mechanical noise is produced from the motor or

gearbox, but if the turbine is working correctly this noise is reduced to a minimum and should

not be an issue. The main concern with wind turbine noise pollution is its impact on human

health, various studies have been carried out and showed that the health problems associated

with infrasound are [31]:

(a) Effects include annoyance, nuisance and dissatisfaction.

(b) Interference with activities such as sleep, speech and learning

(c) Physiological effects such as anxiety, tinnitus or hearing loss.

 

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The relations between wind turbine and its health effects on the general populous is shown in

figure 7.

Fig. 7. Model of the possible relationships between sound exposure, annoyance, sleep

disturbance and psychological distress [6]

1.2.3 Impact on Wildlife especially birds

Wind energy is one of the sources of energy that is most compatible with wildlife and

people around the globe, however there are some reports of bird fatalities by researchers. The

wildlife impacts can be separated into two categories, direct and indirect impact. Direct impact is

when there are bird fatalities due to collisions with wild turbines while the indirect impact are

avoidance, habitat destruction and displacement. Table 3 shows the bird fatality rate in the

United States in 2011.

 

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Table 3

Regional and overall bird fatality rates in the United States [3]

1.2.4 Shadow Flicker and Blade Glint

Shadow Flicker occurs when the wind turbine blades rotate in sunny conditions, casting

moving shadows on the ground that results in alternating changes in light intensity that appear to

flick ON and OFF. Blade glint occurs when the surface of the blade reflects the sun's light [29]

[31]. Close to 3% of people with epilepsy are photosensitive and sunlight at flash frequencies

greater than 3Hz has the potential to provoke photosensitive seizures.

1.2.5 Electromagnetic Radiation and Interference

Electromagnetic radiation is a wave of electric and magnetic energy that are

perpendicular to each other and are moving together. Electromagnetic interference from wind

turbines can affect radio communication signals, broadcast radio and television, mobile phones

and radar. Transmission signals from radio or television can get distorted when passing through

moving wind turbine blades. This effect was more present in the first generation of wind turbines

when the blades where made of metal. Today however, most if not all wind turbine blades are

made completely of synthetic material and so this problem is not as pronounced.

 

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1.3 Advantages of Venturi - Type Design

There are many reason why the venturi - type design (if functional) would be a much

better wind turbine design than conventional designs. The first is that it does not need high wind

velocity. Since the purpose of the design is to accelerate slow moving air then these type of wind

turbines would be able to be placed in areas where wind energy was not considered before due to

slow wind speeds. The second major advantage over the conventional design is that, due to the

bladeless nature of this wind turbine, the noise pollution factor would be basically eliminated, as

well as the shadow flickering and blade glint. The design allows for the total containment of the

turbine rotor which would lead to less aerodynamic noise and also, if noise is still present, to the

addition of noise insulating materials. The third advantage is the elimination if the wildlife

environmental hazard as well. Since there won't be any blades exposed to the environment, bird

fatalities can be reduced drastically. The fourth major advantage is its mobility and life

endurance. Since this design incorporates a housing that contains the rotor and electric generator,

shielding them from the elements, the life of the unit is expected to be prolonged and the unit

very mobile. Making this design type perfect for domestic applications, by placing it on their

roof tops or it can also be scaled up, making large venturi cones out of concrete to withstand high

wind velocities generated inside. There are also many other minor advantages such as low

manufacturing cost, low maintenance etc. but the main advantages for which this design was

created are stated above.

 

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2. Theory

2.1 Wind Power

The wind power Pw in an air stream with a density and a velocity through a cross　 　 -

area is:

A wind turbine will develop a power Pt, and Pt/Pw is the conversion efficiency, sometimes

referred to as the power coefficient, mathematically [26] [30]:

So the Larger the swept area the more wind power will be generated. In the Venturi-Type

design the swept area is not the same as in conventional designs, the area is not like that of a

circle but more of a donut, and also the angle through which the air does work is dependent on

the position of the inlet and outlet pipes as shown in figure 8 below. The swept area would then

be: A = (θ/360) π [(R1)2 - (R0)

2]

Fig. 8. Cross section area for working air in venturi - type wind turbine

R1 

R0 

 

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2.2 The Venturi tube

Two equations that were used most extensively throughout this project when coming up

with the design and troubleshooting errors was the Bernoulli's theorem and the equation of mass

conservation or continuity equation as it is sometimes referred to. Bernoulli's theorem is a

statement of conservation of energy for fluid flow and in the case of the venturi tube's internal

flow, this equation is not perfectly accurate as the flow is not completely incompressible but it's

an excellent approximation for the purpose of this design [27]. Mass flow simply explains that

the mass inflow must equal to the outflow and for so if a parameter is increased or decreased

then another parameter must decrease or increase to maintain the conservation of mass.

Therefore if the areas for a given mass flow with velocity V and Pressure P is decreased (i.e. the

flow is constricted), then for the same quantity of mass to pass through a given section in the

same period of time, the velocity of the flow must increase. This in turn reduces the pressure at

the point where velocity is increased.

For and incompressible fluid the Bernoulli's theorem is:

 

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where (P/γ) is the static pressure head; (V2/γ) is the velocity pressure head and z is the potential

energy head. If the potential energy head is zero then Bernoulli's equation is reduced to

A typical Venturi Tube has a converging cone on one end and a diverging cone on the other (see

figure 9) . The section where the cone is constricted the most is where the velocity is highest.

Fig.9. Venturi Tube [15]

 

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2.3 The Permanent Magnet generator

A PM generator consists of two rotor discs mounted on either side of a non-magnetic,

non conducting stator. the magnets are generally arranged in a N-S-N-S manner

circumferentially round each rotor plate with the North magnet on one plate facing the South

magnet on the other. Magnetic flux permeates the air space between the rotor disc and travelling

one pole pitch before coming back across the air gap. The flux density distribution is

approximately sinusoidal in both the radial and circumferential directions so that the flux density

profile can be described as a sinusoidal hill, described by the equation [14] :

where ĵn is the magnet equivalent current density given by:

and Brem is the magnet remanence, dm the magnet diameter, τ the pole pitch and un = (πn/ τ). This

flux density profile can now be used to derive the flux between the centre of the armature coil

and the radius ra as:

If it is assumed that the armature coil is concentrated at its mean axial position but that

the coil is divided into three segments a,b and c in the radial direction. Then the total flux linkage

and the coil emf are given by:

 

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3. ANSYS Settings

All simulations for the wind cones were done using ANSYS fluent. The geometries were

imported from Solidworks as (.IGS) files and a fine tetrahedron mesh was created from the

imported geometries using the mesh modeler. Inlet and Outlet selections were chosen and named

to make the setting of boundary conditions easier when using fluent. The setting for fluent are

shown in the flowing Figures

Fig. 10. ANSYS fluent General Settings Fig. 12. Boundary Conditions Settings

Fig. 11. Model Setting/Turbulence Settings Fig. 13. Solution Methods Settings

 

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Fig. 14. Solution Initialization Setting Fig.15. Run Calculation Settings

 

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4. Design Procedure

Many steps and simulations were carried out to arrive at the final design for the Venturi -

Type Wind Turbine. Every time a simulation was carried out and a flow phenomena was noted,

an alteration to the design was done in order to correct the problem or to make the design more

efficient. In the end the main desired characteristic that was pursued was high inlet speed in

order to make the turbine spin faster.

4.1 Wind Cone Selection

A wind cone can come in any shape or form, as long as the area is reduced the wind

speed should increase. However, in free stream air a lot of other factor come into play and the

geometry and shape of the cone can be very important. Some can lead to air stagnation, flow

separation or recirculation. For the Venturi - Type design, three cones were considered, a box

shape design (figure 16), a tetrahedron or triangular shape design (figure 17) and a cylindrical

cone shape design (figure 18). Details about the dimensions for the cones can be seen in

Appendix A.

Fig. 16. Square Cone Fig. 17. Tetrahedron Cone

 

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Fig. 18. Cylindrical Con

When their front face was set as the inlet with the boundary condition as inlet velocity at

4m/s, all of the designs basically showed the same result with air being accelerated to speed up to

400+ m/s (see figures 19-21).

Fig. 19. Velocity Vectors of Square Cone

 

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Fig. 20. Velocity Vectors of Tetrahedron Cone

Fig. 21. Velocity Vectors of Cylindrical Cone

So with the front faces selected as the inlet, all three cones showed almost the same

velocity acceleration, however when the cones where places in a Air Box in which just the front

of the box was selected as inlet, the cylindrical cone showed the most, if any, air circulation

through the cone (see figures 22-25). Therefore the cylindrical cone was selected for the design.

 

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fig. 22. Square Cone in Air Box

Fig. 23. Velocity Vectors Of Square Cone in Air Box

 

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Fig. 24. Tetrahedron Cone in Air Box

Fig. 25. Cylindrical cone in Air Box

It is believed that the reason why the cylindrical cone was much better at allowing the

flow of air is because, due to its circular nature the angles inside the cone are much smoother and

so wind does not hit the walls and rebound outside again but instead deflects the air in such a

manner that it leads it further inside the cone. While the other square and tetrahedron designs

have flat sides and steep angles that might deflect the air outside rather than further inside.

 

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4.2 DESIGN 1

After the choice of cone had been finalized, a design was made in which the cone was

connected to the hub which enclosed the rotor. A vertical outlet pipe was placed at 180°from the

inlet behind the hub to allow for the exit of the air, placing it in a vertical position allowed for a

greater amount of air to exit since after the curve of the hub, the air will already be travelling in

the Y -direction and so the momentum will allow the air to flow out. Figure 26 shows the general

shape of the design and for more dimensions and details see Appendix B. A simulation of air

flow inside the hub is shown in figure 27, with the inlet air velocity at 4 m/s.

Fig. 26. Initial Form of Design 1 Fig. 27. Velocity Vectors inside the Hub

From the simulation it can be seen that the design could be improved. Box 2 shows where

the flow separates and that all the mass does not exit, therefore the system has negative feedback.

This mass of air then flows back around to the inlet, and because more mass is being added to the

inlet then the velocity decreases. In box 1 we can see this decrease at the boundary where the

negative feedback flow meets the inlet flow, a slight change in colour illustrates this change in

velocity (see figure 28).

 

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Fig. 28. Negative feedback and Velocity reduction

4.2.1 Addition of a Venturi Tube

To get rid of the problem of negative feedback, a Venturi tube was added to the design to

suck out the remaining air, thereby elminating feedback and maintaining higher velocity at the

inlet. Two models where tested, one where the suction pipe of the Venturi tube was connected to

the outlet pipe (figure 29) and another where the suction pipe was connected directly to the Hub

beside the outlet pipe (figure 30). Simulations were done for the two models (figures 31-34) and

the results compared to select the best model. For more details and dimensions of the Venturi

tube see Appendix C.

Fig. 29. Venturi Tube connected Fig. 30. Venturi Tube connected

to outlet pipe directly to hub

 

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The Venturi tube was designed in such a way that a small tube of diameter (D) empties

into a larger tube to diameter (2D) therefore doubling the area. Therefore by the law of

continuity the mass flow will be halved and to try to restore balance it will try to obtain air mass

from another source, thereby causing a suction.

Fig. 31. Simulation for Venturi tube connected to Outlet Pipe

Fig. 32. Close up section of the Hub: Inlet Vel ≈ 340 m/s

 

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Fig. 33. Simulation for Venturi Tube connected direct to Hub

Fig. 34. Close up section of Hub: Inlet Vel ≈ 360 m/s

 

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After analyzing the simulations it was noted that having the Venturi Tube directly onto

the Hub gave better results than when it is coupled onto the outlet pipe. For one the Inlet velocity

was slightly higher and also having the Venturi tube directly on the Hub produced a nice flow

field as depicted in Box 3, with a higher air velocity being more uniformly spread out across the

working area. This might be explained by the fact that the low pressure area in the venturi tube

causes a suction that accelerates air towards the outlet thus making a more uniform flow field.

Box 4 shows that more air is being removed from the hub since air is coming both out of the

outlet tube and suck out by the venturi, this slight improvement in mass flow might be

responsible for the slight increase in inlet wind speed since negative feedback is reduced.

 

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4.2.2 Increasing the Working Area.

For the maximum amount of energy to be transferred from the wind to the rotor, the

working area in which the wind turns the rotor must be increased. The further the distance the

wind pushes the blade the more torque will be generated and as a result more electricity

generated. To increase the working area, the outlet pipe was moved along the circumference of

the hub, increasing the angle from the inlet pipe to the outlet pipe. Two models were designed

and tested, one which had the outlet pipe in a vertical position at 270°from the inlet pipe (figure

35) and another which had it at 225°(figure 36). For more details and dimensions of the models

see Appendix D. Simulation were carried out on both models to determine which one had the

more beneficial characteristics (figures 37-38).

Fig. 35. Model with outlet pipe at 270° Fig. 36. Model with outlet pipe at 225°

 

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Fig. 37. Simulation of flow inside model Fig. 38. Simulation of flow inside model

with outlet pipe at 270° with outlet pipe at 225°

From the results it could be seen that the Model with the outlet pipe at 225°was the better

one since the inlet velocity was much higher, approximately 550 m/s (box 5) while the other was

at around 400m/s. Also the Velocity vector plots showed much more uniform high velocity fields

in the second model as shown in Box 6. This is most likely due to the fact that in the first model

with outlet pipe at 270°, the direction of the air flow had already changed dramatically so that

the direction of the outlet pipe and the direction of the flow air flow were perpendicular to each

other. However in the second model the direction of air was almost parallel to the direction of the

outlet pipe so the flow was easier. More air flowing out means less feedback and higher inlet

velocity. Combining the Venturi Pipe from the simulations before to the new design with the

position of the outlet pipe at 225°, we obtain a modified version of DESIGN 1. Below are figures

for the modified model along with a simulation for air flow through the model (figures 39-40).

For more accurate simulations a circle was cut out of the model to more accurately represent the

exposed area to the rotor fins where the air would flow. Simulations showed that after the

modifications only a small percentage of air circulated back to the inlet (box 7) For more details

and dimensions see Appendix E.

 

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Fig. 39. Modified Design 1 with Venturi tube and outlet at 225°

Fig. 40. Simulation of Air flow through Modified Design 1

 

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4.2.3 Final Design 1

The last modification done on DESIGN 1 was the addition of a third cone to the inlet. This

allowed two mass inflows to be joined in the same area of the inlet pipe and as a result increase

the velocity of the air dramatically. Figure 41 and 45 shows the final setup of the Venturi- type

wind turbine with the outlet pipe in the Y-direction. A simulation for the airflow through the

final design was done (figures 42-44) and for any additional details or dimensions see Appendix

F.

Fig. 41. Final DESIGN 1

 

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Fig. 42. Simulation of Final DESIGN 1

Fig. 43. Close up of Hub in Simulation of air flow: Velocity Vector

 

33  

Fig. 44. Pressure Contour for Final DESIGN 1

Fig. 45. Final DESIGN 1 with Pneumatic Turbine

 

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4.3 DESIGN 2

After DESIGN 1 was completed, it was tested by placing it in an air box to simulated

outside conditions. The simulation showed to air acceleration whatsoever and the results were

rather disappointing (figure 46). However this might be caused simply because of missing or

misplaced boundary conditions or a general miscalculation of the program. Nevertheless a

different design was created to try to get some results when simulated in an air box. The reason

as to why no air was flowing through the model was thought to be because of the pipes. Due to

the large number of pipes connecting to each other and their relatively small area, the flow might

have been choked. Therefore a design with no to little pipe length would be preferred. Using all

the information learnt from making DESIGN 1, DESIGN 2 was made (figure 47 and 49).

Fig. 46. Simulation of DESIGN 1 in an Air Box

 

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Fig. 47. DESIGN 2

The Main difference between DESIGN 1 and DESIGN 2 is that design 2 has the suction

pipe attached to the outlet pipe rather than direct to the hub, also the Venturi Tubes were

improved. This is because running more simulations it was found that for DESIGN 2 in free

stream air, having the suction pipe attached directly to the hub placed it at equal distance around

the hub from the inlet and so it caused the inlet air to split and race up the opposite direction of

rotation. However having it on the outlet pipe not only made the air flow in the correct direction

but also encouraged rotation. A simulation of DESIGN 2 in an air box is shown in figure 48

below, showing air velocity reached up to 60m/s in the hub at free stream. For more details about

DESIGN 2 or for dimensions, see Appendix G.

 

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Fig. 48. Simulation of DESIGN 2 in an Air Box

Fig. 49. DESIGN 2 with Pneumatic Turbine

 

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5. Permanent Magnet Generator Design

The permanent magnet generator design was based on designs from professor Wang

Song Hao. The design was adopted and incorporated into the wind Turbine design. The PM

generator is a single -sided coreless axial-flux generator, which is cost effective and easy to

produce. The coreless AFPM generator uses one steel rotor disc and one non-magnetic non-

conducting stator disc. The former carries the NdFeB permanent magnets, arranged

circumferentially around the rotor in a N-S-N-S arrangement, as shown in figure 50 (a). The

latter uses PEEK engineering plastic carrying coils to eliminate the cogging torque and to reduce

the iron loss. The pneumatic turbine (figure 51) is then integrated with the rotor disc of the

AFPM generator. However for use in a wind turbine, it would probably be more beneficial to

incorporate more than one layer of magnets and coils so that more energy can be produced.

Therefore Professor Wang's design can be expanded to become a much larger generator.

Fig. 50. Electric Power Generation Unit [34]

Fig. 51 Structure and Angle Pneumatic Turbine [34]

 

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The induced voltages for different RPMs and loads is shown in figure 52 below. Figure

53 shows the general makeup of the generator and its electrical circuit equivalent. For more

details about the PM generator see Appendix H-H5.

Fig. 52. Voltages generated at different RPMs [34]

Fig. 53. The general assembly of the Axial Flux Permanent Magnet Generator. [34]

 

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6. Conclusion

The aim behind this Project was to develope a new way in which to harvest wind energy.

One that produces less negative side effects than the conventional wind turbines and also one

that works on a different principle than most others. By designing a Venturi -Type Bladeless

Wind turbine generator, the problem or noise pollution and infra-sound generation is not only

eliminated but also wind energy is able to be harvested in areas never considered before and at

much lower altitudes. Now areas where wind speed is low can still benefit from wind energy

because this design uses Bernoulli's theorem and mass continuity to accelerate the air to usable

speeds. The simulations show that these designs are promising and can be functional. There may

still be some minor modifications that can be made to improve the design and make it more

efficient, tweaking the diameter ratios for the cones or extending the length. If more research is

done in this area, this design should be much more cheaper to manufacture and may even be used

as a domestic power source.

 

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References

[1] Ahmed, N.A., “A novel small scale efficient wind turbine for power generation”,

Renewable Energy 57 (2013) 79-85

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200

R90

R200

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270°

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