1

2

3

Executive Summary

Objective:

Wind turbine designs are always striving for improved performance and ways to maximize the

number of benefits. Our team was tasked with developing a rotation system that would maximize

electrical yield in any wind conditions to improve the design of horizontal axis wind turbines.

This solution had to meet a series of stringent requirements that were verified by inspection,

demonstration, or analysis. These requirements included topics such as structure, performance,

energy yield, interaction, and control. Furthermore, our team had to address the problem with

wind turbines causing avian fatalities. With these elements in mind, an effective design proposal

for rotating wind turbines was formed by our team that would improve performance, decrease

expenses, meet all requirements, and reduce avian fatalities.

Solution:

Our team analyzed 4 possible solutions to rotate a wind turbine: an upwind yaw drive with

motor, a fan (resembling a helicopter tail), a rudder tail (similar to a weathervane), and a

downwind design. After researching and analyzing multiple possibilities using our criteria for

Pahl and Beitz analysis, our team selected the downwind turbine design as our solution. A

downwind turbine is similar to a typical upwind turbine. An upwind turbine functions by having

a motor rotate the blades and nacelle atop a ball bearing yaw drive to place it in to oncoming

wind. A downwind turbine differs from this design by having the blades and rotor face

downwind. By relocating the side of the tower that the wind hits the blades, rotation is achieved

from drag on the turbine’s blades. This is similar to how a windsock rotates in the wind. The

implications of this change in design are advantageous when compared to the upwind design.

The first implication is that there is no need of a motor, and its associated sensors and computers,

to power the yaw drive rotation. This results in less noise, weight, components, and expenses to

achieve the same result. This means that our design’s only component is a ball-bearing yaw

drive, or a low friction surface, for rotation. The second implication is that under unique

geographic and atmospheric conditions, a downwind turbine design is superior to other

proposals. Due to the angle of incidence with the wind, a downwind turbine’s blades achieve

better energy yield on a hill or mountainside compared to an upwind design. In addition, if

atmospheric conditions are stormy with high and erratic wind speeds, a downwind design

maintains performance and its structural integrity better than other designs. To reduce the

number of avian fatalities, a flashing light system that irritates specific types of birds will be

implemented in our mechanism’s design.

Conclusion:

A downwind turbine design exceeds all of our requirements by weighing less, being more cost-

effective, requiring fewer parts, and achieving the same rotation results (or better) than other

turbine rotation possibilities. It is for these reasons why our team selected a downwind design as

our solution and for the implementation in future wind turbines.

4

Table of Contents Executive Summary .................................................................................................................................... 3

Introduction ................................................................................................................................................. 5

Background ................................................................................................................................................. 6

Final Problem Solution ............................................................................................................................... 8

Appendices ................................................................................................................................................. 13

Appendix A: Alternative Solutions ...................................................................................................... 14

Appendix B: Pahl and Beitz Evaluation Matrix ................................................................................ 21

Appendix C: Explanation of Evaluation Criteria .............................................................................. 22

Appendix D: Requirements and Verifications ................................................................................... 23

Appendix E: Final Project Solution Team Plan ................................................................................. 27

Appendix F: Research Paper 1 ............................................................................................................ 28

Appendix G: Research Paper 2............................................................................................................ 55

References .................................................................................................................................................. 77

5

Introduction

Purpose:

In recent history, there has been a significant increase in the search for alternative sources of

energy. Wind energy is one of the cleanest sources of energy today, however it is not the most

efficient. One of the major problems with wind energy is that the wind turbines do not always

face the wind, and therefore do not always produce energy. Our engineering team was asked to

design a horizontal axis wind turbine that will solve this very problem. In thinking about our

problem, our team came up with several solutions that were critically analyzed and evaluated,

which led us to a final design for a new horizontal axis wind turbine.

Task:

Our team was asked to design a mechanism that would rotate a

horizontal axis wind turbine to face the wind based on current wind

conditions. In addition, we were told that a mechanism that could

minimize avian fatalities would be favorable. Before we designed

solutions to our problem, we had to generate a list of requirements,

and we also had to research specifics about wind turbines, what

repels and attracts birds, and what materials would be best to use to

support the weight of a turbine and rotate it (see Appendix for list

of requirements). The research that was done by each member of

our team was put into two research papers, with the second research

paper including answers to questions about possible solutions that

were designed by pairs in the team. It was decided by our team that

the solution that would win would be chosen using a uniform

grading criteria.

Solution:

Our team evaluated the 4 best solutions that we came up with using the Paul & Beitz criteria, which

can be found in the Appendix. After having a team discussion about all 4 solutions and filling out

the matrices, the final solution that was picked was a solution involving a downwind turbine. Once

wind hits the turbine, the force of the wind hitting the blades will create drag, and this drag will

force the blades to want to rotate to the farthest position away from the wind. This means that the

nacelle will rotate, and the blades will be facing downwind, therefore the turbine will be considered

a downwind turbine. There will not be a need for several extra parts; this solution is extremely cost

efficient. It also does not require a power source, which is another huge advantage. The only part

that will be needed is a low friction ball bearing and a breaking system.

Conclusion:

The downwind turbine will be an excellent way to keep the turbine facing the wind at all times.

There is no need for a power source, and there is no need for expensive extra parts, such as a motor.

This solution is cheap and simple, and easy to integrate into the future wind turbines. This solution

is solving an issue that is not only present in our nation, but one that is present worldwide. This

report will go through the steps that were taken in order to reach this solution, and how certain

crucial decisions were made.

Figure 1: An example of a Horizontal Axis Wind Turbine (HAWT)

6

Background

Background Introduction:

Wind power has been a valuable resource for centuries, and in recent years this resource has

become even more useful as a source for electrical power. It has many advantages over

traditional fossil fuel power sources, releasing no greenhouse gasses during energy production

and having very low impact on the local environment while doing so. Companies are constantly

looking for new ways to improve efficiency in their products, and one area that could be focused

in horizontal axis wind turbines is the mechanism used for yaw axis rotation. Improvements in

this area would result in less energy and material used with more energy produced.

Brief history of wind power:

Wind power has been used since antiquity as an alternative to water mills for the grinding of

grain, being built in places with small or slow moving bodies of water. The earliest examples

found are vertical axis wind turbines, built in ancient

Persia. These designs made their way through the

western world and eventually developed into the

horizontal axis turbine in the early middle ages. In the

more southern lands of Europe these windmills were

often built of solid stone, with the blades facing in

one direction, with no ability or need to rotate, as the

winds in those areas were consistent in their patterns

(Hill, 1994). In more northern areas however,

especially England and the Low Countries that would

become Belgium and the Netherlands, these

windmills were built of wood. Eventually these mills developed an early form of yaw axis

rotation, namely having oxen or strong horses drive a shaft through a series of gears to rotate the

upper portion of the windmill so that the blades caught more wind(Hill, 1994).

These windmills continued to develop and complete more tasks

that just grinding grain. In the Netherlands they were used to

pump sea water out of the ground. They were brought across the

Atlantic to the New World. There they were used to draw water

from underground reservoirs in the under developed the North

American West during the 19th century (Hill, 1994).

Wind turbines as we know them developed during the start of the

20th century, though due to the infancy of environmental concern

of fossil fuels, they did not become widespread nor largely

developed until the 1970s (Hill, 1994). With the spurring of

investment by private companies and public subsidies wind

power finally began to become widespread in the 1990s.

Figure 2, Iberian windmills, late medieval

Figure 3, Danish windmill, early 19th century

7

Yaw Axis rotation in Horizontal axis

Turbines:

Currently the vast majority of wind

turbine rotate the top of the tower holding

the gear box, blades, and turbine itself by

using a series of electrical motors

connected to a central gear ring (Figure 3).

Due to the immense size of nacelle, often

weighing several tons, huge amounts of

torque and therefor very powerful motors

are needed in order to turn the nacelle into

the wind and keep it there (Hau, 2006).

The motors receive signals to turn from sensors located on top of the nacelle. These sensors,

usually an electric weather vane which direction the wind is coming from and an anemometer

which measures the strength of the wind. Together these signals are sent to a small computer or

chip that reads them and sends the appropriate signals to the motors (Hau, 2006).

Concluding Remarks:

While current designs are adequate for the job of turning wind turbines, improvements can be

made and should be sought out. Anything that can reduce material used, energy consumed or

increase energy produced is something to be sought after. Doing so helps to fulfil the twin goal

of wind turbines, to be economically friendly and provide energy.

Figure 4, Electric motor yaw drive with four motors

8

Final Problem Solution

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any wind conditions.

Solution Description:

Our team’s solution is a downwind turbine rotation mechanism. A downwind turbine rotates on a

low friction ball bearing yaw drive similar to a motorized upwind turbine. The difference

between the two is that there are no motors, sensors or computers that power and control the

rotation of a downwind turbine. Instead, downwind turbine designs take advantage of drag from

the wind to rotate into the ideal position automatically without the need of any additional energy

or components. The principles behind how a downwind turbine rotates are the same as the

principles that cause a wind sock or weathervane is always position themselves furthest

downwind from the direction of the wind. Downwind turbines offer many benefits over the

traditional upwind turbine designs such as enhanced performance on a hill and improved control

during stormy weather or a blackout. These benefits make downwind turbines more suitable for

harvesting wind energy than upwind turbines under unique geographic and atmospheric

conditions.

How Solution Meets Evaluation Criteria:

Wind turbine designs strive for improved electrical yield, reliability, efficiency, and low

maintenance. With this in mind, many different types of wind turbines, all with varying features,

benefits, and disadvantages, have been produced. This section will discuss the various

advantages and disadvantages of downwind turbines and their prospects for future wind energy

generation.

A downwind turbine differs from an upwind turbine by its location of rotor and blades. A

downwind turbine has its blades positioned downwind of the tower. See figure 5 for a

visualization of the difference in structure between a downwind and upwind turbine.

9

Figure 5: The location of the blades and rotor define what type of horizontal axis wind turbine it

is ("Downwind Rotor," n.d.).

There are many differences between the upwind and downwind turbine designs. Each design’s

components, especially the rotation mechanism, are altered to adapt to the differences in

aerodynamic and physical performance associated with each type of turbine. In other words,

each type of turbine has different components because they function differently from one

another. Because the mechanism used to vary the position of the horizontal axis wind turbine

design and the overall turbine design are so interconnected, the range of material in the

discussion of benefits and disadvantages will be extended to include the overall turbine, not just

the rotation mechanism. To clarify, the upwind turbine will be associated with the motorized

active rotation method and computerized control system and the downwind turbine associated

with the free rotation method and no computer control system. These differences will be

discussed in accordance with the criteria of our team’s Pahl and Beitz matrices on the basis that

the same factors that are ideal for the rotation mechanism are similarly ideal for the overall

turbine design.

Control:

The control criterion deals with the turbine’s ability to sense the surrounding wind conditions

and respond accordingly using the rotation mechanism. For an upwind turbine, this mechanism

would be a motor attached to the yaw drive and controlled by a computer system. The computer

system would analyze the atmospheric conditions and use the motor to position the wind turbine

into the direction of oncoming wind (Manwell et al., 2002). Figure 6 shows the layout of an

upwind turbine. It is important to note that the difference between an upwind turbine and

downwind turbine is the lack of a motor driving the rotation.

10

Figure 6: The yaw drive motor used on an upwind turbine (noted as number 7 in the image)

("Wind Energy: Product and Solutions," n.d.).

Unlike an upwind turbine, a downwind turbine does not require any additional motors, computer

systems, components or energy to rotate since downwind is the natural position that the turbine

would be drawn towards (Manwell et al., 2002). This is based off of the principle that the rotors

and blades would create drag in the wind and rotate to the position furthest downwind as

possible. Because the downwind turbine capitalizes on this property, it is able to rotate more

efficiently than the upwind turbine and its rotation mechanism can function even in the case of

power failure (Matsunobu et al., 2009). The actual rotation mechanism would be similar to the

upwind rotation mechanism in the above image, except it would lack the motors and control

systems.

Performance:

The performance criterion deals with the mechanism’s ability to operate in as wide a range of

wind conditions and capture as much energy from the wind as possible. Under certain

circumstances, a free yaw control (free rotation) turbine with the rotors placed downwind is

advantageous over an upwind, active yaw control turbine. Besides the energy and control

benefits mentioned above, the downwind turbine also maintains stability through very high

winds. This is due in part to the turbine being able to adjust freely to large gusts and irregular

wind patterns. An upwind turbine must try to adapt to the same conditions using sensors and

motors, which would be more difficult given the circumstances (Manwell et al., 2002). In

addition, a downwind turbine would function better on a hill or mountain. Since the blades of a

wind turbine must be angled away from the tower to prevent them from striking it in the event of

high winds, a downwind turbine is better angled for wind flowing uphill ("Downwind Rotor,"

n.d.).

11

Figure 7 (left image): Demonstrates how wind blowing up strikes the blades at a greater

incidental angle, providing more energy (downwind rotor on left, upwind on right). The yellow

arrow is the ideal angle that wind would strike the blades of that turbine design and the grey

arrow is the actual angle of the wind. Notice how the downwind turbine (left) has the wind strike

the blades at an angle closer to the ideal angle ("Downwind Rotor," n.d.).

Figure 8 (right image): Wind vector model showing how the downwind turbine is better suited

for wind traveling uphill than an upwind turbine. The wind is nearly perpendicular to the blades

of the downwind turbine, providing a larger energy yield compared to the upwind turbine, where

the wind is nearly parallel (“Downwind Rotor,” n.d.).

However, these benefits are only found on a downwind turbine positioned uphill or in a

mountainous location. On level ground or at sea, the turbines would produce nearly identical

amounts of energy. It is also important to note that these effects to not work similarly downhill

for an upwind turbine. Wind does not travel downhill very well since it loses the majority of its

energy and will have increased turbulence after going over a hill or mountain. Both of these

effects result in scenarios less than ideal for harnessing wind energy (Matsunobu et al., 2009).

Structure:

The structure criterion concerns the materials used in the rotation mechanism and their impact on

the performance of the overall turbine. The materials would ideally be durable, light, and

recyclable. The downwind turbine excels in this area because it requires far fewer materials than

the upwind turbine since its yaw rotation is free, not actively controlled (Manwell et al., 2002).

However, by using a downwind system, problems arise that come at a cost to the overall turbine.

The center housing of the gearbox and generator atop of the tower that attaches to the rotor and

blades is called the nacelle. The nacelle is upwind of the rotor and blades in a downwind turbine

design and this creates turbulence or wake known as tower shadow (Manwell et al., 2002).

Tower shadow can cause unequal loads along the rotor and blades leading to fatigue damage and

increased noise. This is one of the reasons why downwind turbines have been less popular than

their upwind counterparts. However, with the significant increase in both turbine size and

capacity, and improved aerodynamics of the nacelle, tower shadow is being reduced. As a

turbine’s size increases, its blades extend far beyond the nacelle and accordingly receive less

tower shadow. As a result, downwind turbines are becoming a more popular solution for

harnessing wind energy (Matsunobu et al., 2009).

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Energy:

This criterion concerns the ability of the mechanism to aid the turbine in maximum energy yield.

Both mechanisms of the upwind and downwind turbine designs rotate the rotor and blades into

the optimal angle for generating electricity. The only difference is that the upwind design

requires electricity to operate the sensors, computers and motors while the downwind system

does not require any electricity. In general though, both designs produce a similar electrical yield

(Manwell et al., 2002).

Interaction:

This criterion involves the relationship of the mechanism with various populations. Ideally, the

mechanism should be quiet and have as small an impact as possible on people and nearby

wildlife. Both mechanisms have slight drawbacks but overall have a negligible influence on the

environment. The upwind turbine would have to reduce the noise made by its motors when

rotating the rotor and blades. The downwind turbine would produce increased noise from the

effects of tower shadow on the turbine’s blades (Manwell et al., 2002).

Cost:

This criterion relates to the overall economic viability of the mechanism. The downwind turbine

again has an advantage over the upwind turbine because of the lack of sensors, motors,

computers, and batteries or capacitors to run those systems and still resulting with on par, if not

better, electrical output (Manwell et al., 2002). However, it is important to note that the effects of

tower shadow could lead to increased fatigue and a possible increase in the long term cost of the

turbine if maintenance work is required more frequently. Similarly, the larger number of

components on the upwind turbine could result in more parts to fail and more maintenance work

(Matsunobu et al., 2009).

Conclusion:

There are many advantages and disadvantages of the downwind turbine rotation mechanism

compared to the traditional upwind turbine rotation mechanism. The downwind design has many

benefits over the upwind design due to the lack of expensive components, ability to function

more efficiently uphill, and the ability to remain more stable under extreme winds or in the case

of a power failure. Some noted disadvantages are the effects of tower shadow and its long term

impact on reliability and an increase in noise. However, with the creation of larger turbines, the

effects of tower shadow are minimized to a point that the downwind turbine design becomes

favorable over the upwind turbine design (Matsunobu et al., 2009).

13

Appendices

14

Appendix A: Alternative Solutions

Alternative Solution I: Yaw Drive Mechanism

Our Mechanism utilizes a series of sensors to determine current wind speed and direction. The

information received will be processed and will send signals to the motor. The nacelle will then

be attached to a ball and bearings, which will enable it to rotate. The motor will turn a series of

gears that will turn the nacelle. As you can see in figure 9, the yaw system will be placed in

between the tower and the nacelle. The gears, or yaw drive, will be attached to the ball and

bearings, which will then turn the nacelle to face the wind. According to our Pahl & Beitz

criteria, the most important categories are Control and Performance, and Structure. Our design

satisfies the control category very well, because using a motor and yaw drive will be a very

effective way to turn a turbine, as similar systems are used to turn the turrets on tanks and ships.

Since the mechanism will be within the tower, it will be able to operate regardless of the wind

conditions. The materials that will be used in the mechanism are going to be very strong and

durable, so our mechanism satisfies the structure category very well. Energy is the next most

important category, and while our mechanism may require more energy to operate than other

solutions, the energy is not a very significant category in our Paul & Bitz criteria, so the energy

required to operate the motor is of little importance. The last two criteria are Interactions and

Cost. Since our mechanism is almost entirely inside the turbine, it will have no new effects on

any populations. While this does not solve the issue of avian deaths, it will not contribute to any

more deaths. Building this mechanism might be more costly than other possible solutions, but

since there is no budget for our project, the cost has very little significance.

Figure 9

15

Alternative Solution II: Fan Mechanism

The prevalent issue with wind technology is that wind turbines are unable to effectively adapt to

their environment. Wind is unpredictable, and in order for turbines to operate efficiently they

must be able to adapt to their surrounding environment. In other words, “go with the flow”. The

device that is about to be described will vary the position of a wind turbine and optimally align it

so it can operate at its maximum potential. The device is called The Fan Mechanism and it can

be integrated into almost all horizontal axis wind turbines. The mechanism utilizes multiple

sensors and meteorological data to position itself in a direction that will allow the turbine to

produce the most energy.

The Fan Mechanism can visually be compared to the tail of a helicopter, and it happens to

operate in a similar way. The tail of a helicopter has a rotor (fan) at the end that stabilizes the

helicopter and changes its direction. The mechanism will enable the upper portion of the wind

turbine to rotate 360 degrees about the vertical axis. For a visual representation of the

mechanism, please refer to figure ten and elven below.

Figure 10

Figure 11

16

The upper portion of the wind turbine will rotate on a low friction surface when given rotational

energy from the fan at the end of the tail. All of this enables the mechanism to operate while

requiring minimal energy. Figure twelve provides a visual representation of the low friction part

of the mechanism.

Figure 12

The tail of the mechanism will extend a certain distance from the structure out into the air

(Figure 13). Attached at the end of this structure will be the fan (Figure 14). The fan, when

given a signal, will turn on and rotate the turbine blades and generator to an optimal energy

producing position. When the turbine is optimally aligned, the fan will shut off and a braking

system will lock it in place.

Figure 13

Figure 14

17

An additional feature of the mechanism is that it can operate without the use of electrical energy

when necessary. Having the mechanism operate like a fantail can do this. The fantail came

about in 1870 and it is a device that automatically rotated windmills directly into the wind.

When the Fan Mechanism needs to conserve energy, it can operate like a fantail (Figure 15).

(Lytham Windmill Museum).

Figure 15

The Fan Mechanism effectively meets the entire criterion in the Pahl and Beitz. Below, we will

describe how each criterion was met.

Control was given the highest weighting factor of 0.30. Because of such a high weighting factor,

it was the focal point of our solution. The Fan Mechanism will be able to align itself into an

optimal energy producing position at a moment’s notice. Sensors, attached to the mechanism,

will signal the fan to rotate with a certain frequency. The frequency of the fans rotation will

determine the speed at which the upper portion of the turbine rotates. The sensors then signal the

fan to stop rotating and a braking system to go into effect when the turbine is optimally aligned.

The turbine can potentially be aligned within a few centimeters of its optimal position.

Performance was given the second highest weighting of 0.20. It was also given careful

consideration when we produced our design. The Fan Mechanism will be able to perform in all

conditions. It is durable to extreme weather and is able to operate in low wind speeds as well.

The mechanism has the ability to operate like a fantail, which enables it to operate without

requiring electrical energy.

Structure, also given a weight of 0.20. The device is relatively simple and few parts are needed

for its construction. The device consists of only three main parts to be exact. These parts are the

rotational hub, tail, and fan. The device is also not excessively large and can be transported with

ease

Energy was given a weight of 0.15. It requires minimal energy to operate, due to the low friction

surface it sits on as well as having the fan extended from the structure. The mechanism can also

operate without electrical energy, as stated before, by acting like a fantail.

Interaction was given a weight of 0.10. The device makes almost no noise, due to the low

friction surface and quiet fan blade. It will also not negatively interact with the environment and

nearby populations. It will also prevent bird collisions due the light system on the tail of the

http://www.lythamwindmill.co.uk/The-Mill-and-Its-Workings.html

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mechanism

Cost was given the smallest weight of 0.05. Materials for construction are relatively inexpensive

and long lasting. Few parts (three) are required for construction. The highest costing material

will be the low friction surface it sits on which in return will help the turbine produce more

energy and thus increase its cost effectiveness.

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Alternative Solution III: Sail Mechanism

Our mechanism enables the wind turbine to rotate with the help of a sail/tail vane and a

frictionless surface. The frictionless horizontal surface enables the turbine to rotate efficiently.

Included with the mechanism is a locking system. This will lock the turbine into the ideal

horizontal position to harvest wind and make sure that it does not continuously keep spinning.

The locking device that was created is shown in figure 17.

In regards to the Pahl and Beitz criteria, the solution’s structure will be durable with no moving

parts. The only possible worry is if the tail vane gives out to any strong winds. The solution’s

control will be dependent on the tail vane and locking system. The tail vane rotates the wind

turbine and changes the position it is facing, while the locking device locks the turbine into

position. The solution’s performance will be similar to general wind turbines already; none of the

main energy-harvesting aspects will be affected. Therefore the energy obtained by the turbine

will be quite similar to already existing turbines. The solution’s energy efficiency will be great.

The wind turbine is rotated through the use of wind; therefore no energy is technically needed for

the wind turbine to work, but minimal energy will be used for the locking device, which will

include a wind sensor, wiring, and pressure sensor pads. The solution’s interaction with the

public should be very minimal. The addition of a tail vane shouldn’t disrupt or bother any close

neighborhoods or visitors. The solution’s cost should be cheaper than traditional motors. The

frictionless surface could be expensive, but even if it is expensive, our turbine would cost just

about the same as already existing mechanisms.

Figure 16

20

Figure 17

21

Appendix B: Pahl and Beitz Evaluation Matrix

DESIGN CANDIDATE

ONE DESIGN CANDIDATE

TWO DESIGN CANDIDATE

THREE DESIGN CANDIDATE

FOUR

Criteria

Weighting Factor

(W)

Numerical Value (NV1)

Weighted Value

(W*NV1)

Numerical Value (NV2)

Weighted Value

(W*NV2)

Numerical Value (NV3)

Weighted Value

(W*NV3)

Numerical Value (NV4)

Weighted Value

(W*NV3)

Structure 0.20 1.83 0.366 2.00 0.400 1.67 0.3340 1.42 0.2840

Energy 0.15 1.50 0.225 2.00 0.300 1.00 0.1500 1.83 0.2745

Control 0.30 1.50 0.450 1.00 0.300 1.67 0.5010 1.67 0.5010

Performance 0.20 1.00 0.200 1.67 0.334 1.33 0.2660 1.33 0.2660

Interaction 0.10 1.50 0.150 1.33 0.133 1.33 0.1330 1.50 0.1500

Cost 0.05 1.00 0.050 2.00 0.100 1.17 0.0585 1.50 0.0750

Total 1.00 1.441 1.567 1.4425 1.5505

22

Appendix C: Explanation of Evaluation Criteria

Control:

Control was given a weighting factor of 0.30 because it is the most important characteristic of

the mechanism. It addresses the core aspects of the problem statement and has the largest impact

on energy output of the turbine.

Performance:

Performance was given a weighting factor of 0.20 because the mechanism must perform

optimally in order to enable the wind turbine to operate in all wind conditions.

Structure:

Structure was given a weighting factor of 0.20. This is because the materials used as well as their

durability, weight, etc, are critical to the operation of the mechanism

Energy:

Energy was given a weighting factor of 0.15. While it is an important criteria for the project, the

energy required to operate the mechanism is not of high importance. As long as it operates

effectively, the CEO will be satisfied.

Interaction:

Interaction was given a weighting factor of 0.10. This is because the way in which the

mechanism impacts populations and the environment is not of utmost importance to the CEO. It

is, however, a criteria that will be considered when designing the mechanism.

Cost:

The cost of the mechanism was given the lowest weighting factor of 0.05 because designing a

mechanism that is cost efficient is not in our problem statement, however a cost efficient design

would be favorable.

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Appendix D: Requirements and Verifications

Definition:

An electrical energy company shall be the user.

[HAWT 1.1] The mechanism shall be able to rotate the turbine.

A downwind turbine operates on the principle of drag to rotate the device downwind

automatically and at the optimal angle. This rotation method has been proven to work on large

scale turbines and consumes no energy. This requirement is verified by inspection.

[HAWT 1.2] The mechanism shall use minimum energy while maximizing energy output.

The mechanism will require no external energy, and will automatically turn towards the wind,

thereby maximizing energy output. This requirement will be verified by analysis using a diagram

that demonstrates energy flow to exemplify no energy utilization and motion of the mechanism.

[HAWT 1.3] The design will have minimal impact on local populations.

Our design will not use any motors or other mechanical means to turn the turbine, resulting in

significantly less noise pollution caused by the motors of an upwind turbine design. The

requirement is verified by inspection.

[STRUC 2.1] The mechanism shall operate reliably within the temperature range of -30ºC (-

22ºF) to 55ºC (131ºF). {HAWT 1.1}

According to Protecting Wind Turbines in Extreme Temperatures (2013), modern wind turbines

need to operate within a temperature range of -30ºC (-22ºF) to 55ºC (131ºF). Wind turbines

today are designed to operate within this temperature range. The battery and motor system of

traditional turbines are most vulnerable with regards to change in temperature and usually need

to operate between 0 degrees and 10 degrees Celsius. Because the mechanism our team is

designing does not include a battery and motor system, it can operate over a wider range of

temperatures than traditional turbines. Therefore, this requirement for our mechanism is verified.

This is verified by analysis (Protecting Wind Turbines in Extreme Temperatures, 2013).

[STRUC 2.2] The mechanism shall be able to withstand a relative humidity of at least 95%.

{HAWT 1.1}

According to Wind Energy Explained: Theory, Design and Application, conventional wind

turbines can withstand a relative humidity of at least 95%. Our design differs from a

conventional wind turbine by the lack of a motor and the location of the blades. There are no

new parts introduced. Thus, the materials used are not affected and the ability to withstand at

least 95% humidity shall be the same. This is verified by analysis.

24

[STRUC 2.3] The materials for construction shall cost less than $30000. {HAWT 1.1}

According to the American Wind Energy Association, the average cost is around 30,000 (FAQs

for Small Wind Systems, 2013). Since the downwind turbine is essentially an existing wind

turbine with the fan positioned at the opposite end of the mechanism with no additional parts, the

cost must be less than $30,000 if put under the same constraints. FAQs for small wind systems.

(2013, January 1). FAQs for small wind systems. Retrieved May 7, 2014, from

https://www.awea.org/Issues/Content.aspx?ItemNumber=4638&navItemNumber=727Thus,

without a motor and computer system, the new design must cost less, verified by analysis.

[STRUC 2.4] The weight of the transport truck and mechanism shall not exceed 80,000 lbs. This

is the legal combined weight limit of an 18 wheeler and its cargo in the United States. {HAWT

1.1}

This requirement will be met because our design does not plan on increasing the weight of any

one part but rather decreasing the weight of wind turbines today by removing the yaw drive

motors. Because certain components are being removed, the overall weight of the mechanism

will certainly decrease. According to the US department of transportation, a weight limit for a

transport truck is 80,000 pounds. Our mechanism is expected to weigh less than a nacelle which

currently weigh about 100,000 pounds (Benini & Toffolo, 2002). This weight is mainly due to

the yaw drive mechanism which contributes to approximately more than 20% of the nacelles

weight. Because this component is removed the nacelle the weight will fall below 80,000

pounds and therefore this requirement is verified. This requirement is verified by inspection

("Commercial Vehicle Size and Weight Program," n.d.).

[STRUC 2.5] The materials for construction shall be able to last at least 20 years, while able to

support at least 100 Tons, as the combined weight of the nacelle and the blades of the tower will

add up to a minimum of 92 tons. {HAWT 1.1}

According to Wind Energy Explained: Theory, Design and Application, the metal alloys and

materials used in rotation mechanisms are designed to last at least 20 years. Most turbines

created today are designed with nearly a 30 year lifespan and in the case of a downwind turbine,

the rotation mechanism is rarely the first major component to fail. In addition, newer wind

turbines are being created that are ever larger and heavier. The size of the ball bearing yaw drive

required is documented and can be modified to handle any weight requirement (Manwell,

McGowan, & Rogers, 2002).

[STRUC 2.6] The mechanism should be designed with recycled materials. {HAWT 1.1}

There are current models of wind turbines that are designed and built with recycled materials.

Therefore, our design will utilize the same methods and produce a structure using biodegradable

materials. Downwind turbines do not require any additional components than a traditional

upwind design and thus, will be constructed with recycled materials as it has been done before

with upwind designs. Current journal articles, specifically one written by Schleisner goes into

detail about turbine recycling as well as what materials are required to produce a turbine. By

inspecting and analyzing current wind turbine designs discussed in this journal article, our group

25

is confident that this requirement is verified. This requirement is verified by analysis and

inspection (Schleisner, 2000).

[STRUC 2.7] The design shall withstand all wind conditions. {HAWT 1.1}

Discovered through technical research, the downwind design is able to function in much higher

speeds compared to other means of horizontal axis rotation. The only hard limit on the wind

conditions is the condition of the blades, gearbox and the turbine of the structure. This is verified

through inspection.

[CTRL 2.1] The mechanism shall rotate the wind turbine based on the current wind conditions.

{HAWT 1.1}

The mechanism that our group is designing is a downwind turbine. A downwind turbine does not

require a motor or sensors to change its position. The rotors and blades are positioned in a certain

way that creates a force that automatically turns the turbine. Essentially, the turbine moves by the

power of the wind. It moves in a position that is furthest downwind so it can produce the most

amount of energy. The turbine repositions itself based on the current wind conditions by using

the power of the wind and drag forces. Typical wind turbines are designed to be upwind. If one

were to compare an upwind turbine to a ball in a valley, it requires a lot of energy to move the

ball. With regard to a downwind turbine, imagine a ball on top of a hill, minimal energy is

required to move the ball. Both balls are in equilibrium. However, the ball on top of the hill, the

downwind case, is much easier to move. This idea applies to wind turbines as well. Therefore,

this requirement for our mechanism is verified by inspection via the solid edge model as well as

analysis through research (Matsunobu et al., 2009).

[CTRL 2.2] The mechanism shall detect various wind conditions (direction, speed). {HAWT

1.1}

According to Wind Energy Explained: Theory, Design and Application, a downwind turbine is

faster at responding to changes in the wind than any motorized system. This is due to the fact

that any change in direction of the wind results in a change in force and results in an

instantaneous response by the system, all without the use of computers, sensors, or motors

(Manwell, McGowan, & Rogers, 2002). This requirement is verified by inspection.

[PERF 2.1] The mechanism shall be designed to require little maintenance. {HAWT 1.1}

Our design is built to require little maintenance because we are not adding any parts that are not

in wind turbine designs today. If anything, our design would require less maintenance because

we are removing the yaw drive motors from the turbine. The requirement is verified by

inspection.

[PERF 2.2] The mechanism shall not disrupt the wind turbine’s performance. {HAWT 1.1}

The final designed mechanism functions because of the wind. There are no extra parts other than

the ball-bearings yaw drive needed to allow the turbine to rotate since the rotation force is

26

supplied by drag. Because there are no new parts that could possibly disrupt the wind turbine’s

performance, this requirement is satisfied by inspection.

[PERF 2.3] The design will last at least 20 years under normal operating conditions. {HAWT

1.1}

The downwind design compared to other methods of yaw axis rotation have many fewer moving

parts, principally being the steel bearings that the nacelle sits upon. While these have been

known to fail on larger wind turbines, since the downwind design is smaller and lighter, the

bearings are relatively easy to replace compared to other parts used in yaw rotation in other

designs. Thus, the requirement is satisfied by inspection.

[ENER 2.1] The mechanism shall utilize internal energy from the wind turbine {HAWT 1.2}.

To verify this requirement through analysis, a diagram of the energy flow in the wind turbine

system will demonstrate the use of wind against the blades to turn the turbine. Wind is used,

rather than electrical motors, to horizontally turn the wind turbine. No internal energy is

required.

[ENER 2.2] The mechanism shall maximize energy output of the wind turbine. {HAWT 1.2}

Since the mechanism will not require any additional energy to operate, it will not be taking away

any energy that the wind turbine produces, which helps maximize energy output. The motor in

current wind turbines can use up to 10% of the total output of an upwind turbine (Miller, 2012).

In a 1.5 Mw turbine, 10% of 1.5 Mw would be saved using our device. Since there would be no

other way to reduce the energy needed to rotate the nacelle, this requirement is verified by

inspection and analysis.

[INT 2.1] The mechanism shall generate less than 85 dB of noise while turning the turbine and

avoid creating sound that is less than 20 Hz in frequency. {HAWT 1.3}

Since the mechanism will not require a motor, and will in fact be taking a motor out of the

current wind turbine design, no motor-generated noise will be created. Since the current wind

turbine designs do not exceed this decibel range already, and we will be removing the motor, we

expect the noise level to be within the acceptable range. This requirement is verified by

inspection as well as analysis from research (Mo̸ller & Pedersen, 2011).

[INT 2.2] The mechanism should be designed to minimize avian fatalities {HAWT 1.3}

Avian forms that are commonly known for being killed by wind turbines have been researched.

These types of birds can normally be irritated by bright flashing lights, such as the type of

airplanes. Therefore, a similar type of light system will be installed on the turbine and will fend

away these birds, satisfying this requirement by inspection.

27

Appendix E: Final Project Solution Team Plan

28

Appendix F: Research Paper 1

To: Professor Neuberger, WTSN 104, Section 57

From: Adam Suda

Date: 2/11/14

Re: Research Paper #1

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any wind conditions.

Introduction:

It is a fact of the world that resources are limited and nowhere is this more apparent than for

fossil fuels. In the face of this looming threat, coupled with the growing implications of climate

change brought about by their use, many countries are turning towards alternate means of

producing energy. One such method which is gaining strides is the use of large scale wind

powered turbines to produce electricity to support human populations. This paper will attempt to

cover the problems that can arise in the use of wind turbines, such as structural failure, damage

to the structure (which may lead to casualties of either those who work on the wind turbine

structure or to civilians who may happen to be passing nearby). In addition to these mechanical

failures, this paper will examine some other problems faced by wind turbines which may lead to

damages, such as lightning strikes and ice accumulation.

Structural Damage:

Damages accrued to the structure of the wind turbine occur over time and in many cases are

difficult to avoid. One mean by which turbines are often damaged is when a large scale storm

hits, which results in large amounts of stress on the blades and tower. In some cases the stress

from high speed winds can cause the brakes on the turbine to fail, resulting in the blades

travelling at speeds unsafe for operation. When the blades rotate past certain speeds breakage

and damage can occur, potentially leading to the surrounding areas being subject to blade

fragments (Chia Chen Ciang & Jung-Ryul Lee, 2008, p.7). These blade fragments will be

traveling at very high speeds and can result in deaths and damages to surrounding houses, cars,

or other objects.

The only surefire method unfortunately to prevent these damages to the blades is to either

perform preventive maintenance often so as to catch small damages before they turn into large

problems, or to introduce and maintain an internal sensor network that would tell the company in

charge of the wind turbine when damages would occur, and where they occurred, leading to

fewer maintenance visits, but a higher starting cost due to sensors, and a constant small drain of

electricity to run the sensors.

Another major source of accidents is where the superstructure of the wind turbine, or tower,

outright collapses due to damages. This often results in the death of any person working on the

29

turbine. This damage can be caused by many things, such as fractures of steel and composite

materials from cold stress, or lightning strikes or storms causing damage to the structure, and

high gusts of wind (Rideout, Copes & Bos, 2010, p.3). Fortunately, when a wind turbine outright

collapses, the damage to the surrounding area is mostly localized, compared to when blades fail,

resulting in potentially fewer casualties. All of these factors working together can result in

severe damage to the structure, gearbox, or turbine.

To prevent this from occurring, the turbine must be kept monitored so as to determine any

damages before they might result in large scale setbacks, and the structures themselves made

remote to a limited degree from roads, housing, and other places where the collapse would result

in deaths. However due to the nature of wind turbines requiring very few large objects around

them to steer the wind in on direction or another, maintenance can be very difficult, with the

turbines often being remote to a large degree from residential areas. In addition to this there is

also the matter of the structure being very tall, making repairs difficult and hazardous to workers.

Ice Damage and Ice Flinging:

Especially in colder climates or higher altitudes turbines tend to collect ice along the length of

their blades. The effect of this ice is twofold. Firstly it decreases productivity, by weighing down

the blades, decreasing aerodynamic efficiency. This loss of productivity can be as large as 30 %

in some instances (Dalili, Edrisy & Carriveau, 2009). Secondly, in order to restore productivity

the turbines in some instances need to be shut down entirely so that the blades can be cleaned of

ice. In addition to this, in higher quantities ice adds significantly to the stress load of the blades,

resulting in more accidents, and more maintenance to be required on the turbines. Large chunks

of ice have been known to break off blades as they rotate, resulting in them being ‘flung’, with

some cases the fragments flying up to 100m from the turbines. The inefficiencies and dangers are

a major problem with the growth of the use of wind turbines in colder climates.

However, investigations are currently being made into multipurpose coatings for the turbine

blades which may help reduce the rate of ice accumulation, and therefore the number of stops

made for maintenance of the turbines and to clean the blades, resulting in higher productivity for

these turbines. Another method to pursue in regards to simple human safety is to ensure that the

wind turbines are positioned so that if ice flinging does occur the thrown shards will not damage

any individuals or roadways (Morgan, Bossanyi & Seifert, 2). This can be accomplished by

placing wind turbines a safe distance away from trafficked areas and posting signage to warn of

the possibility of ice flinging should any individual enter the area.

Lightning Strikes and their Effects on Wind Turbines:

The large size of wind turbine’s, their metal structure, and their relative isolation often make

them prime targets for lightning strikes, which can have disastrous results. These can result in

structural damages, damages to internal electronic equipment, and even the turbine. These are all

dangerous and expensive things to deal with in wind turbines, with replacement taking huge

amounts of effort and material.

To properly safeguard against lightning it is recommended to use a conductive material on the

30

blades to reduce to the number of strikes (Chia Chen Ciang & Jung-Ryul Lee, 2008, p.4). In

addition to a blade coating, electronic materials within the turbine need to be properly shielded

and checked often to ensure that damage does not grow over time and that preventive

maintenance can stop any major destruction.

Conclusion:

While many of the articles were mainly tangent to the problem of properly designing a method

for properly implementing a horizontal wind turbine that would rotate for greatest wind

efficiency, these articles were key in showing many of the safety issues that currently prey upon

wind turbines and hold back the industry from growing to fruition. In particular, investigation

should be made into blade coatings that will increase aerodynamic efficiency. In order to design

a turbine that will work anywhere and not be in danger of destructive failure safety must be key

in design. Failure to do so could result in lawsuits from property damage or even injury to

individuals, which should be avoided as these could result in not only loss of revenue, but also a

poorer attitude towards wind turbines which could lead to community action to get turbines

removed or a loss of government grants.

Recommendations:

Any wind turbine built has very key criteria that makes placement of wind farms rather limiting.

It cannot be built too close to any homes or major roadways, because of safety concerns and

potential damages that might be occur against bystanders. Large objects in general such as hills

or rocky outcrops should be avoided as they ‘steer’ the wind and may result in lower velocities

or inconsistent velocities. In addition to this, colder climates should be avoided due to dangers of

ice accumulation and flinging. Maintenance, while costly, should be done regularly to ensure that

the structure is sound and not in need of repairs or replacement of parts. An alternative to

frequent preventive maintenance is to implement a system of sensors on the wind turbine that

would monitor the integrity of the structure and report back to the company in charge of the

turbines so that maintenance can be acted as needed. However this would result in higher build

costs and a constant low drain to electricity. Brakes and blades in particular seem to be prone to

damage and should be checked the most frequently.

31

To: Professor Neuberger

From: Brandon Okraszewski

Date: 2-09-14

Re: Research Paper #1

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any windy conditions.

Introduction:

With the steady decline of availability of fossil fuels, necessity for renewable resources is

increasing. A forever increasing population calls for a greater demand of energy, therefore bringing

forth greater consumption and an increase in price of fuel. Wind turbines are “the most developed

renewable technology” (Wilkinson et al., p. 1), capable of converting energy from high-speed

winds to electrical energy. As such, wind turbines can act as a suitable replacement for, or in

conjunction with, nonrenewable resources to provide cheaper energy. This paper analyzes

maintenance of wind turbines to provide optimal energy output with minimal cost of reparations

over the course of a lifecycle of the turbines. Determining adequate methods of maintenance and

degradation detection will allow for cost efficiency in the solution of the problem statement.

Cost:

An increase in cost of operation and maintenance lowers profitability of wind farms; income

becomes less than operation and maintenance fees, driving financial supporters away from

investments in wind turbines. Under the equation for cost of energy accepted by the wind energy

research community and Department of energy in the Low Speed Wind Turbine program,

determining factors of the overall cost are initial capital cost, fixed charge rate, replacement cost,

annual energy production and operations and maintenance costs (Walford, p. 5).

Operations and maintenance account for approximately ten to twenty percent of the total cost of

energy; operations refer to the on-site personnel, turbine monitoring and emergency response.

Maintenance becomes further divided into scheduled maintenance, in which standard inspection

and reparations occur, and unscheduled maintenance, in which malfunctions occur that require

attention.

Options suggested by Walford (p. 11) to reduce cost of operations and maintenance include

identification of critical components, determination of causes of failure, development for logistic

plans, improved personnel training, and improved maintainability. The proposed solution to the

problem statement must take into account the different aspects of the cost of energy, specifically

within the operations and maintenance cost while qualifying potential methods to reduce such

costs.

32

Degradation Detection:

Operations, maintenance and replacement costs are dependent upon the reliability of detection of

deterioration. As a result, methods of deterioration detection are of the utmost importance. Systems

of detection must have a high rate of success and determine necessity of repair at an early time

such that rate of production of energy is not impaired.

In determining the optimal maintenance system, cost, time and ability to measure potential to

deteriorate must be taken into account. Once case proved online condition-monitoring system to

be the optimal method of maintenance in test of different models over one-hundred-thousand

simulations in Matlab (Besnard, 2010).

Through the FMEA, or failure modes and effects analysis, manufacturers are granted the ability to

predict turbine failure rates. Using a condition monitoring rig, different components of the wind

turbine are tested to identify the failure rates of each part. Thus parts of new and old designs are

compared to identify the best component to use in future designs (Wilkinson, 2006).

Conclusion:

These articles provide understanding of the components of maintenance, specifically cost and

maintenance systems. As a result, findings from the articles will provide guidelines to follow

during the design phase to produce a cost efficient machine with little need for maintenance. The

proposed solution may avoid components with high failure rates and thus lower cost of operations

and maintenance. In response, the cost of energy will be lowered and attract more financial

investors. This, in turn, will allow for greater funding of development in wind turbine and increased

production of wind farms. The articles further provided information of the different aspects of the

costs of turbines; solutions to the problem statement must not cost a significant amount such that

the cost of replacing and repairing a turbine will increase to outweigh the income of wind farms.

Recommendations:

Based on reading these articles, I would make the following recommendations for our project:

Failure rates of the individual components of wind turbines must be researched to identify parts

that should be used in the final design of our horizontal axis turbine. Following this research, the

parts should be considered in the design to create a turbine with little need for maintenance.

Geography should be taken into account, as parts may function differently under different

environmental conditions. On shore turbines in relation to off shore turbines will degrade quicker

and will require maintenance more often.

Further research must be conducted on income of wind farms to analyze an acceptable price of

production, resources and maintenance. This income may be used to determine profitability when

compared with the cost involved with wind turbines.

The team must always consider lifetime, potential to deteriorate due to time or location,

replacement cost, operations cost and maintenance cost in mind while producing the turbine.

33

Condition over time is relative to cost of energy and energy output, and must be kept satisfactory

by manufacturer’s standards to allow wind turbines to act as an adequate substitute for

nonrenewable resources that are depleting at a rapid rate.

34

To: Professor Neuberger, WTSN 104, Section 57

From: Brian Parsons

Date: 2/12/14

Re: Research Paper #1

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any wind conditions.

Introduction:

In light of new evidence of climate change, and the resulting stricter environmental regulations,

alternative energy sources are receiving an enormous amount of attention. Scientists, companies,

and countries have invested billions of dollars into the research of new alternative energy

technologies and modifications to optimize both the efficiency and yield from current designs.

Energy derived from wind turbines is among the most promising energy producing technology to

result from this international effort. Sustainable energy scientists have predicted that by 2030,

20% of U.S. energy needs will be met by wind technology (Grujicic, Arakere & Pandurangan,

2010). This paper will discuss the various problems encountered with the traditional horizontal-

axis wind turbine design and provide possible modifications in an attempt to improve reliability,

lifespan, efficiency, and electrical yield. In addition, all of the suggested modifications will be

analyzed on their cost-benefit relationship as any realistic wind turbine design must be

economically viable for it to be considered a success.

Problems Limiting Performance and Lifespan of Wind Turbines:

Wind turbines are typically designed with at least a 20 year fatigue lifespan in mind (Grujicic et

al., 2010). However, some climates create adverse conditions that can result in many problems

for the long term integrity and performance of the turbine. Arctic, desert or tropical climates with

ever-changing wind and thermal conditions can deteriorate the lifespan of the average wind-

turbine and pose many challenges to engineers. One problem that affects all wind turbines is

their operational wind speed range at which they can function. For example, if the wind speed is

too low, the turbine shuts down because it cannot spin the generator. Similarly, if the wind speed

is too high, the turbine shuts down to prevent damage to the critical components of the turbine.

In addition, other phenomenon that pose a risk to all wind turbines are wind shear and the wind

shadowing effect. Wind shear is when there are different wind speeds at different points on the

turbine’s blades. Typically, wind-speed is lower near the ground level portion of the turbine’s

blades compared to the wind-speed at the top. Over time, this creates a bending moment in the

blade shaft and can produce severe jolts and vibrations within the turbine frame (Phresher, 2010).

The wind shadowing effect is much less detrimental to the lifespan of the turbine, but instead

affects large groups of wind turbines in the same area. As more wind turbines are crowded atop

the same mountain or in the same valley, each additional turbine steals energy from the wind to

spin its blades. As a result, there is reduced wind energy for any turbines positioned behind these

turbines. This poses a challenge for the placing of wind turbines as they become an increasingly

popular tool to produce clean energy (Phresher, 2010).

35

Besides general problems, there are many climate-specific problems that wind turbines must

endure. In frigid polar climates, ice buildup along the turbine blades is a frequent problem

(Dalili, Edrisy & Carriveau, 2009). In warmer tropical climates, the accumulation of bugs on the

exterior of the blades can reduce yield by up to 55%. In arid desert environments with an

abundance of loose sand, the blades can be sand-blasted away, changing their profile and

reducing aerodynamic efficiency (Dalili et al., 2009). Of all of these problems previously

discussed, it is ice accumulation that poses the largest problem, especially since there has been

increased interest in the creation of more wind turbines in very cold environments. The reason

for this is that air at -30 ◦C is 26.7% denser than air at 35 ◦C, and since power produced is

proportional to air density, the power output increases in colder temperatures (Dalili et al., 2009).

While there is a litany of problems facing wind turbines, there are many possible modifications

to counteract and even eliminate their threat to the turbine’s performance and lifespan.

Blade Coatings:

A special surface coating spread over the exterior surface of a wind turbine blade can solve many

of the problems described above. Such a coating would be applied like a second layer of paint

and could be custom tailored to address problems unique to the specific environment that the

wind turbine will be placed in (Dalili et al., 2009). For a frigid polar environment, the coating

could be colored black and have specific hydrophobic and low-friction properties to decrease ice

accumulation. This is achieved by creating a surface that would warm in sunlight and would not

be ideal for ice to stick to. These properties would aid efficiency and extend life expectancy in

warmer environments too (Dalili et al., 2009). These coatings also provide slick, non-wetting,

and impact resistant properties that would provide a defense against insect accumulation and

sand abrasion. Besides resisting the accumulation of debris on the blade and creating a more

durable surface, the blade coatings universally provide a decrease in the air drag coefficient of

any turbine, resulting in increased efficiency (Dalili et al., 2009).

Blade coating technology stems from the aerospace industry and the use of coatings on the

surface of airplane wings. The benefit-disadvantage ratio of using a passive method like blade

coatings to counteract these problems is far higher compared to active systems that require

electrical and computational resources. Existing possible active systems are electrical resistance

heating or a pneumatic system to repel water (Dalili et al., 2009). Both of these systems attempt

to tackle the problems associated with ice accumulation. The electrical resistance heating method

requires electrical energy to be run through coils along the turbine’s blade which heat the

exterior and melt any ice. This method has been shown to significantly reduce ice buildup, but it

poses multiple new maintenance problems (Dalili et al., 2009). Most notable of these is when

one of the heating elements malfunctions and ice accumulation occurs on only one of the blades.

This creates a major disruption in the balance of the blades and can result in the turbine being

forced to stop, or even its failure if the problem goes unnoticed for too long. The pneumatic

system uses pressurized air pumped through holes on the surface of the turbine blade to repel

water and expel frozen particles. While typically effective, both of these methods pose an

increased maintenance burden, require electrical energy, and are more costly than passive

methods like blade coatings (Dalili et al., 2009). Blade coatings help turbines deal with complex

environmental issues and help to improve durability and decrease down-time. However, this

36

technology does not aid the turbine in reducing wind-shear effects or help to extend the range of

wind speeds that the turbines can function in; that is where wind optimization technology can

play a crucial role.

Wind Optimization:

Turbine manufacturers are creating multiple methods to optimize turbine performance in a

variety of wind and environmental conditions. Increased attention towards individual blade

control, atmospheric sensing, and improved electromechanical systems have been made in an

attempt to increase durability and electrical yield. One such method involves the use of

individual blade control where monitoring devices attached to each blade observe the wind

speed, load, and many other variables on the blade at that specific moment. Based on this data,

the pitch of that individual blade is adjusted to provide increased efficiency and more electricity

(Phresher, 2010). One of the benefits of this system is the effect it has on reducing wind shear.

When the wind near the ground is traveling at a lower speed than wind at the top of the turbine,

the turbine could counter this by adjusting the angle of the turbine blade as it is ready to go near

the ground and readjust the angle as the blade approaches the top of its spin cycle. By doing this,

the turbine ensures a constant load over the entire system, reducing unequal forces that result in

deterioration of the frame and gears. This process requires constant analysis of wind conditions

and would increase the maintenance load, but it could potentially improve the lifespan of the

turbine by not exposing the frame and gears to the long-term effects of wind shear. Another

benefit from individual blade control would be the extended range of wind speeds that the

turbine could function in. This is possible since the pitch of the blades can be adjusted, giving the

turbine the ability to either increase or decrease the power that the wind provides the generator.

If there is little wind, the turbine blades could be angled to provide maximum rotational energy.

Likewise, if there are very high winds, the turbine blades can be angled to provide less rotational

energy so as to still provide maximum electricity, but not have to initiate a shutdown to prevent

damage to the gears and generator (Phresher, 2010). These benefits can also be used to address

the problems associated with the wind shadowing effect, like lower wind speeds behind a wind

turbine, because some of the wind energy has been used to generate power. Since turbines can

function in lower wind speeds and adjust to abrupt gusts of wind better through constant

monitoring, the effects of wind shadowing are reduced and more power can be obtained, even

with a decrease in wind speed behind a turbine (Phresher, 2010).

In addition to individual blade control, modifying the electromechanical system can improve the

turbines ability to handle shocks and also provide an uninterruptible power supply. Such

modifications include using a linear rotary system for transferring rotational energy from the

turbine’s blades to the generator and the introduction of high-capacity capacitors instead of

batteries. Capacitors have an advantage over batteries as they respond better in colder

environments, hold a charge indefinitely, and do not need to be replaced or have chemicals

exchanged (Phresher, 2010). These modifications can extend the lifespan by multiple years and

improve the performance of wind turbines, especially as larger diameter wind turbines are being

created that are more prone to issues such as wind shear and the wind shadowing effect.

However, compared to blade coatings, these improvements all require costly hardware upgrades.

Engineers must carefully consider whether a system truly requires these upgrades and if it is

economically sound to implement them.

37

Conclusion:

These articles give great insight into many of the universal and climate-specific problems

plaguing wind turbines around the world and offer a variety of possible solutions. Solutions such

as blade coating, individual blade control, and a modified electromechanical system all address

the heart of the problem statement: to maximize electrical output in any wind conditions.

Extending this problem statement to include any environmental conditions and their associated

problems, such as ice accumulation, will make our team’s project more sustainable than

previously defined. In addition, the inclusion of long term reliability and power production along

with the improved short term electrical yield requirement is also considered as each modification

could affect the maintenance load on the turbine. It is essential to include these risks as some

solutions, such as electrical resistance heating, could result in not only a higher initial cost, but

also increased downtime if multiple repairs must be routinely made to the turbine. Should select

modifications be made to the turbine design, with regards to the climate that the turbine will be

located in, there is a strong possibility of not only an increase in short term electrical yield, but in

a long term improvement in reliability and efficiency as well.

Recommendations:

These articles provide many great ideas from which to address our problem statement. First, our

team should hone in on the ideal location that would have the least environmental and social

impact, while still remaining close to necessary electrical grids and within access of construction

crews. This can be determined by the reports made by my teammates whom were tasked with

researching this ideal location and climate. Next, a careful analysis of the above solutions must

be made to produce a turbine that not only provides the most electricity with the largest range of

operational wind speeds, as stated in the problem statement, but that is also reliable, safe,

durable, and cost-efficient. Some of the modifications may not be required nor pose a large

enough improvement to warrant the risk of a heavier maintenance load. As was done during the

reverse engineering project, evaluations of all of the possible solutions should be completed

systematically, in order to determine which most benefit our design. Finally, our team should

step back and analyze our resulting design from an economic, engineering, and environmental

standpoint to determine if the design could be further improved and ensure that all of its

components would stand-up to real world applications.

38

To: Professor Neuberger, WTSN 104, Section 57

From: Evan Kearney

Re: Research Paper #1

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any wind conditions.

Introduction:

Wind power has been a part of society for thousands of years. From sailboats to windmills it has

made its mark on everyday life. As years pass, the potential of wind power continues to rise.

Wind turbines are being used in the present day to harvest energy from the wind. Engineers and

scientists have been continuously working to find the optimal design for the wind turbine. There

have been many theories and designs that have already been tried that have proved to be either

inefficient or were not the optimal design for a wind turbine. Wind power systems have the

potential to solve many of the world’s current problems because it is an efficient and quite

reliable natural source of energy. This is why the search for the optimal design of a wind turbine

is so important. The understanding of the previously attempted designs and theories of wind

turbines could provide a deeper understanding of the problem statement and make it easier for us

to develop our mechanism to maximize electrical output in any wind conditions.

Blades:

One of the most important parts of wind turbines are their blades. The blades are the part of the

mechanism that utilizes the natural wind and uses it to rotate the shaft of the generator converting

mechanical energy into electricity. The blades are the part of the wind turbine that can determine

exactly how much power the turbine can potentially produce. There are multiple factors that

need to be taken account of when analyzing the blades of a wind turbine, such as the blade

number, blade materials, and blade shape. In addition, with these physical characteristics, it is

also important that the cost of the blades remain low to keep the cost of construction reasonable.

In order to truly carry out the problem statement, it is important to understand the history of the

blades of wind turbines and, more specifically, what variations on these designs have been tried

before. It is helpful to learn from either the success or failure of these previous modifications.

The most important piece of information to know before talking about the blades of wind

turbines, is that there is a maximum amount of energy a turbine can extract from the wind.

Anything with an airfoil, defined as the shape of a wing, blade, or sail, can at most be about 60

percent efficient. Horizontal-Axis wind turbines operate around 35 to 40 percent efficiency.

(Benini & Toffolo, 2002) It is also important to know that if a site has very strong gusts of wind

it may not necessarily be the ideal site for wind turbines. “Strong gusts provide extremely high

levels of power, but it is not economically viable to build machines to be able to make the most

of the power peaks as their capacity would be wasted most of the time.” (Gurit, 2014, p.2)

Therefore the most ideal site is one with relatively steady winds. Therefore, the ideal design in

turn must be a turbine that is able to harvest the most from the lighter winds and still be able to

withstand stronger gusts of wind.

39

The number of blades was one of the first variables optimized when it came to wind turbines. In

1887, in Ohio, Professor Charles F. Brush built a 12 kW wind turbine to charge batteries in the

cellar of his mansion. His turbine had 144 rotor blades. A few years later, scientists and

engineers in Denmark discovered that fast rotating wind turbines with fewer rotor blades were

more efficient in generating electricity. Fewer rotor blades work better for multiple reasons. One

reason is because it decreases the amount of air disturbance for the following blade. In addition,

the fewer number of rotor blades allow the turbine to be built at a more reasonable height which

increases stability. Earlier it was mentioned that there is a maximum amount of energy that can

be harvested from wind. Because of this, the less blades there are, the more power each can

extract from the wind. On a side note, having a turbine with fewer blades would decrease the

costs of constructing the wind turbine. (Gurit, 2014, p.1)

An additional design factor that comes into question when talking about efficiency of wind

turbines is the shape of the blades. Wind-turbines have similar characteristics to airplane wings.

The specific design allows the blades to support the lift, drag and gravitational forces acting on it

from the wind. Another very important factor of the shape of the blades is the thickness of the

blades. The thickness is generally 10 – 15 % of its chord length and it tends to be thicker where

the end of the blade meets the mast where the bending forces are greatest. (Gurit, 2014, p.5)

Although it is more efficient to have thinner blades, cost comes into play when deciding which

thickness to use. It will cost more to make thinner blades because of the cost of reinforcement

inside, therefore there is a dilemma in the design process to find the optimal thickness of the

blades.

The material of the blades is a significant part in the design of any wind turbine. The material

must be made to certain specifications of the following characteristics: stiffness, density, and

longtime fatigue. The stiffness of the material must be able to support aerodynamic performance,

the density of the material has to be able to reduce the gravitational force, and the material has to

be dependent and reliable over a long period of time. Many different materials are used for

specific parts of the turbine. For example, carbon is used in blades and leading edges because it

has a very specific and ideal stiffness to it, while thermoplastic liquid resins are used for inner

spars of the blades in order to help extend the life span of the wind turbines. (Golfman, 2012,

p.56)

Vertical-Axis Wind Turbines:

When thinking of ways to improve the horizontal-axis wind turbines, a good question to ask is

why vertical-axis wind turbines are not the favored way to harvest wind power. Vertical-Axis

wind turbines are more aesthetically pleasing, and can be put anywhere because of their ability to

create energy by utilizing wind in any direction. It could be beneficial to find the weak points of

the vertical-axis wind turbines, so we know what parts of our horizontal-axis wind turbine design

to try to improve on.

Referring back to earlier in this paper, it was mentioned that wind turbines can only extract a

maximum amount of energy from wind. One of the biggest problems with vertical-axis wind

turbines is that it is less efficient than the horizontal-axis wind turbines. Up to ten percent less

40

efficiency. One of the main reasons this is the case is because the vertical-axis wind turbines are

constructed near ground-level. Unfortunately, there’s less power in ground-level wind. The ten

percent difference doesn’t sound like much, until other factors such as maintenance and lower

energy production are put in the mix. It is clear that vertical-axis wind turbines are second best

when it comes to generating electricity. (Hau, 2000, p. 46)

One factor that is unique with vertical-axis wind turbines is that it can take wind from any over

time. This special factor can actually lead to problems with the structure. Vertical-Axis wind

turbines work almost like an egg beater, with two vertically oriented curved blades spinning

around a vertical shaft. With this spinning comes centrifugal force. Inertia creates this apparent

force that draws a rotating body away from the center of rotation. This could lead to the

deformation of the blades and would require maintenance. The design of the wind turbine makes

it impossible to overcome these problems with centrifugal forces. That is not the only

maintenance related problem that the vertical-axis wind turbines encounter. Vertical-Axis wind

turbines are generally placed low to the ground. Many ground-level objects surrounding it such

as buildings, trees, etc. create turbulence. This turbulence can change directions of the wind and

speed the wind up and down. This makes vertical-axis wind turbines more prone to wear and

tear. To try and avoid this, engineers and manufacturers try to make the structures stronger by

adding more materials. Along with the new materials, more labor will be needed in the

construction of the vertical-axis wind, making the turbines very costly and significantly heavier.

(Hau, 2000, p. 48)

Conclusion:

The articles discussed are effective towards the project because they provided information about

what we need to focus on improving with our turbine design. We know what we can and cannot

affect when it comes to the design of the horizontal-wind turbine, and we know results from

previous designs that have failed and results from previous designs that have proved to be

efficient. I think these articles help make it clear the modifications we should try and take into

consideration when creating our mechanism. One possible modification could be changing the

shape of the blades. Many of the faulty concepts of the vertical-axis wind turbines should be

taken into consideration when creating our mechanism as points to improve on. These articles

have also made it clear that cost is a very important factor when it comes to modifying or adding

components to a wind turbine.

Recommendations:

Based off of these articles, I would make the following recommendations for our project:

I believe we should attempt to improve our horizontal-axis wind turbines in the specific areas

where the vertical-axis wind turbines tended to fail: maintenance and energy production. When it

comes to structure, vertical-axis wind turbine’s worth goes down because of its consistent

breakdowns. The demands for regular maintenance on these turbines add to the overall cost of

vertical-axis wind turbines as well. Therefore I believe our mechanism should be very secure and

sturdy so that no extra costs will be needed for maintenance purposes. As for energy production

purposes, I believe we should follow the theories and design of Benini’s article. This is the

reason why after reading of the optimization article of horizontal-axis wind turbines, I believe we

41

shouldn’t focus too much about the design of our horizontal-axis wind turbine as a whole as well

as the materials for the wind turbines. I believe if we feel we should be modifying any part of the

design, we should modify the blades shape or length, mainly because there seems like there

could possibly be room for improvement. The article about optimization, although it is hard to

understand because of my lack of expertise in the study field of wind power, seemed to have

very accurate and precise calculations and analyses. It is a very recently published article,

therefore it has very present-time optimal designs for wind turbines. The article about wind

turbines blade materials had incredible amounts of data to back up its recommendations towards

which materials to use, therefore I believe any ideas of modifying the material of the blades

should be left alone as well. By ruling out specific possibilities of design modifications, it will

allow us to find our optimal design quicker. It will keep us from wasting time trying to think of

ideas to modify almost optimal characteristics of wind turbines.

42

To: Professor Neuberger, WTSN 104, Section 57

From: Lucy Lin

Date: 2/12/14

RE: Research Paper #1

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any wind conditions.

Introduction:

For centuries, humankind has sought after safe and efficient methods to generate electricity.

Finally, an environmentally friendly solution was discovered. The revolutionary wind turbine

emerged as a powerhouse in the market for renewable energy. There are two main forms of wind

turbine, ones with a vertical axis and ones with a horizontal axis. Vertical axis wind turbine

designs incorporate a rotational axis that is perpendicular to the ground and is independent of

wind direction. Horizontal axis designs however, have their rotational axis parallel to the ground

and are capable of generating more electricity from the same given amount of wind. For this

reason, horizontal axis designs are preferred. When considering the optimal design for a

horizontal axis wind turbine that will be efficient and independent of the wind direction,

environmental concerns must be taken into account such as source of noise, aesthetic impact on

nearby landscapes and negative impact on avian population.

Source of Noise

Many concerns have arisen regarding the noise of wind turbines on nearby towns. The main

source of the commotion is the aerodynamic noise coming from the blades of the wind turbine

generator interacting with the wind. Those who live near wind farms often find it difficult to

sleep as they describe “swishing” and “thumping” sounds which generally causes more

annoyance than other types of sounds. The sound created by wind turbines has a low frequency

that induces harmful health effects such as headaches and nausea. When a questionnaire survey

was conducted, 20% of people responded that wind farms, even at the lowest noise level, causes

disturbed sleep at least once a month (Hanning, 2010). Although the most simple solution to

prevent the disturbance of noise would be to place wind farms further from residential dwellings

and into rural areas, that is not the most logical solution once the demand for renewable energy

using wind increases. Research has shown that a possible way to reduce the noise of wind

turbines includes changing the design of the trailing edge of the airfoil by adding serrated strips

of various sizes close to the top since most of the noises occur in that area (Inventus Holdings,

2013). This method helps reduce the sound without either compensating its efficiency or adding

to the total cost.

Aesthetic Impact on Landscapes

With wind turbines becoming increasingly popular, many are concerned with the aesthetic

effects such structures have on the landscape. Since there are less turbulent winds at higher

43

heights, the towers of these turbines are often visible from residential communities and cannot be

easily masked as other aerial features such as cell phone towers. In many cases, these wind

turbines are usually found on a desert or mountainside, which causes the implication that it is

“ruining” the scenic landscape. These negative associations with the aesthetics of wind turbines

could be mitigated once opponents consider the alternative to using wind turbines, which are

both unappealing and environmentally harming. Such alternatives may include extracting more

oil or building more power plants. Additionally, wind turbines will slowly integrate themselves

into the scenery and become familiar constructions very much the same way that bridges and

skyscrapers have become staple images of the modern world.

Impact on Bird Population

As wind turbines become increasingly abundant in large fields, the danger that it poses to the

avian population soars as well. There have been various bird collisions with the turbines that

results in death for the animals, especially certain species such as bald eagles, raptors and

waterfowls. Raptor interactions with wind farms occur in high numbers because they migrate at

night where there are less lights (DeLucas, p. 2). The location of these structures may interfere

with migrating routes which have the potential to stress the birds out and will result in death

elsewhere or impact their health. Habitat loss is also a potential problem as these birds lose their

homes or are forced to abandon them.

A specific type of bird, the bald eagle, is closely impacted due to the location of an expected

construction site in the western United States. To protect bald eagles from wind farms, the U.S.

Fish and Wildlife Services implemented the Eagle Conservation Plan Guidance, which offers

legal protection for bald eagles (Division of Migratory Birds Management, pg. 3). To prevent

further mortality of bald eagles especially due to these wind structures, there are certain numbers

of eagle mortalities that are permitted each year in certain areas.

Although there are a number of deaths each year caused by wind turbines, studies have shown

that these are, in fact, not common occurrences. These studies, especially the one done by De

Lucas and his team, have concluded that wind turbines are not any more dangerous to birds as

other manmade structures such as power lines and highways for birds have demonstrated the

ability to be able to sense the presence of wind turbines (DeLucas, pg. 9).

It is inevitable that some avian will occur from these wind farms, but actions are being taken to

keep these numbers at a minimum. Such measures include looking closely at the location of

these farms and avoiding nesting areas and areas with large populations. Along with choosing a

key location, setting up lights at night will also minimize avian causalities. Radars can also be

used to detect approaching birds and allow the turbine to decrease its speed (American Bird

Conservancy, 2012).

Conclusions

These articles have increased my understanding on the environmental concerns associated with

wind turbines. In order to construct a successful horizontal axis wind turbine that will act

independent to the direction of the wind, the ethics of constructing it is an important aspect to

44

consider. These include the main three environmental concerns present: sound pollution,

aesthetic impact and collisions with the avian population. These articles help list the main

problems with these three concerns along with providing possible solutions that have been

implemented to address them. While trying to solve the issue of sound pollution, many scientists

have experimented with attaching different materials to the blades of the turbine along with

adding serrated strips in order to reduce the noise. The aesthetic features of wind turbines have

been a long controversial topic for many people as there are mixed opinions towards them. While

there are certainly individuals who regard the wind turbines as a form of art, there are also many

others who believe that it is disruptive to the typical landscape. However, although this concerns

still hold, there are very little things that can be done to address this issue. Wind turbines need to

be in an open space in order to receive the most wind. Possible solutions include using the

“lesser of two evils” technique by providing opponents with the arguments that without using

wind technology, alternative forms of attaining energy would be hurting the environment even

more. Finally, there is concern with the effect that wind farms have on avian population. Though

there are deaths present, experiments have shown that these numbers do not amount to any more

than other man-made structures. There are various ways to insure fewer casualties and such can

be done by changing the environment to avoid flight paths and lighting up the wind turbines at

night. All the articles provide possible solution methods and will allow the team to build a

horizontal axis wind turbine that is environmentally friendly and also addresses the concerns that

most people have.

Recommendations:

Based on the previous research and past experimentations, I highly recommend the following in

order to build a successful wind turbine that will satisfy the three primary concerns of the public:

One of the primary goals of the new horizontal axis wind turbine is to make sure the new design

causes the least disturbance to the population. Our potential wind turbines will include serrated

strips of varying sizes to attach on the trailing edge of the blades in order to minimize the sound

produced. These strips would create vortices that would cancel each other out, which would

eliminate the amount of sound produced (Inventus Holdings, 2013). Originally, the strips were of

the same size but after various experiments, it was discovered that serrated strips of varying sizes

work better without sacrificing the productivity of the structure (Inventus Holdings, 2013). We

would also feature a different straight trailing edge instead of one at an angle. Our wind turbine

would be located in areas where there are no residential communities. It would most likely be on

land that has been used before for prior construction so that it would not give off the notion that

human actions for technology are harming the environment. Additionally, steps will be taken to

eliminate avian casualties by installing bright lights that will appear only at night and will be

visible to the birds. Areas of flight paths or heavily populated avian nesting spots are to be

avoided. I recommend that our team look more into the serrated strips and whether adding in

other materials such as rubber along with the strips will produce even less sound that just the

strips itself.

45

To: Professor Neuberger, WTSN 104, Section 57

From: Maxwell Brown

Date: February 12, 2014

Re: Research Paper #1

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any wind conditions.

Introduction:

The world is currently dependent on non-renewable resources for energy. These resources are

harmful to the environment and studies have reconfirmed this. Non-renewable resources are

being depleted rapidly and a new, cleaner resource must be utilized. Researchers have looked

into multiple types of renewable resources determined wind energy to be one of the most

promising. It is abundant and easily harnessed and if further developed, it can become even

more effective. Wind turbines are either classified as horizontal axis or vertical axis. Each has

its pros and cons but a functioning combination of the two would be most desirable. This paper

attempts to determine the optimal locations for these newly developed turbines whether they are

onshore or offshore as well as if they would be more effective as stand-alone systems or grouped

into wind farms. This paper also discusses how the turbines should be designed to be site

specific. This is more expensive than mass-producing turbines but the potential increase in

electricity output could be worth the extra cost.

Grid-Connected vs. Stand-Alone Energy Systems:

Wind turbines can be placed in wind farms or as a stand-alone system. Both forms of placement

are effective and can be placed either onshore or offshore (Han, Mol, Lu, & Zhang, 2009, p. 1).

A wind farm is a group of wind turbines placed in the same location with the purpose of

developing a large amount of electricity. Wind farms are connected to the power grid, which is

connected to a distribution plant that distributes the electricity to the local area. If there is a

surplus of electricity the extra power simply returns back to the power grid. This process

essentially turns the power grid into a battery. The extra energy is stored and can be used when

needed. In order for the power grid to produce an effective amount of electricity, large amounts

of wind energy must be harvested. This requires a large amount of land to host the turbines

(Kaundinya, Balachandra, & Ravindranath, 2009, p. 1-2).

Stand-alone wind turbines can simply be described as turbine that stands alone. A stand-alone

wind turbine is not connected to the power grid and is effective in remote locations. Because

they are effective in remote locations, they solely concentrate on serving the energy needs of one

group of people, which is simpler than serving the needs of the millions of people connected to a

power grid. Stand-alone turbines take up significantly less area than wind farms and cost

substantially less to operate. A downside to a stand-alone wind turbine is that surplus energy

cannot be incorporated back into the grid and must either be wasteed or stored in batteries, which

46

can be both expensive and inefficient (Kaundinya, Balachandra, & Ravindranath, 2009, p. 1-3).

A recent study conducted by Kaundinya and his coauthors determined that there has been both

success and failure with grid-connected systems and stand-alone systems. The development of

either system is location dependent and thus one approach is not entirely better than the other.

The location of the wind turbine must be taken into consideration before selecting which method

would be most effective.

Onshore Wind Energy:

Wind energy began to be harvested onshore centuries ago in order to pump water and grind

wheat. Today it has evolved and is now used to generate electricity. China is a country that has

an abundant amount of onshore wind power available and the country has certainly taken

advantage of it. A journal article written by Han and his coauthors examines a specific region in

China, Mongolia, and its development of onshore wind turbines. Mongolia is considered to be an

ideal location for the development of wind technology because of its high altitude, open terrain,

and monsoon like windy climate.

The development of onshore wind power in Mongolia began in the 1970’s. The first turbines

created were stand-alone turbines and two decades later the first gird connected wind farm was

developed. Since then, wind technology development increased rapidly and by 2007, Mongolia

had 1,856 wind turbines. Although there has been a great increase in the development of

onshore wind turbines, the wind farms in Mongolia are not all that profitable. Reasons for this

are that it is expensive to transport the wind turbines to the build site. Roads, railways, and water

are required to get the turbine parts from where they are manufactured to the site where it is

being constructed. Also, it is not economical or even feasible to transport the electricity from a

remote location (where the turbines are located) to the power grid. Thus, when developing a

turbine an ideal location is not only determined by high wind speeds and climate. It is also

heavily determined by the convenience of reaching the location and its proximity to the power

grid (Han, Mol, Lu, & Zhang, 2009, p. 1-3).

Aside from the construction of the turbine, the transportation of its parts, and the distribution of

the electricity it generates, it is important to consider how it effects the environment it is placed

in and the population of the people and animals that live there. Wind energy is relatively clean

however; the construction of the turbine is usually not an environmentally friendly process so

this must be considered when picking a location. Wind farms must be placed in locations that

avoid the paths of migrating birds and must not negatively impact the local species that live

there. Lastly, developers must deal with the people who live near the turbines. Some people

find them aesthetically unpleasing and claim that they make noise. This article makes it clear

that developers must take multiple variables into consideration when developing onshore wind

turbines (Han, Mol, Lu, & Zhang, 2009, p. 9).

Offshore Wind Energy:

A new trend in wind technology development is offshore wind turbines. Offshore wind turbines

are placed in the water not to far off the coast of the location it is powering. A recent study

47

written by Dvorak and his coauthors look at the potential of offshore turbines in California.

There are many more limitations and variables when designing an offshore turbine. The turbines

are more expensive to build and are currently restricted to shallow waters. Once the turbines are

up and running, it is substantially more expensive to transport the electricity from the turbine

under water to a location onshore where it can be utilized. Lastly, maintenance costs are more

expensive due to the turbines constant interaction with the sea. Simply put, offshore wind

turbines are more expensive. However, the question is whether or not the increased price tag on

the turbines is worth the extra energy they generate. Offshore turbines on average produce more

electricity than onshore ones. This is due to the faster moving air moving over the water.

Dvorak states, “Unlike most of California’s land based wind farms which peak at night, the

offshore wind near Cape Mendocino are consistently fast throughout the day and night through

all seasons.” (Dvorak, Archer, & Jacobson, 2010). Based on the previous statement, offshore

winds are more predictable. Predictability is one of the main issues with wind energy and the

fact that there is consistency over water makes offshore wind energy very desirable. Another

advantage to offshore wind turbines is that the transportation of the parts is not restricted to the

small amount of room available on rail and truck and large parts can be moved on ships (Dvorak,

Archer, & Jacobson, 2010).

There are four types of offshore wind turbines that are being developed: gravity, monopole,

multi-leg, and floating. Gravity turbines can be placed in the shallowest of waters, monopole can

be placed slightly deeper, and multi leg can be placed in deep waters. Floating turbines are still

in development but soon they will permit turbines to be placed in the deepest of waters. The type

of turbine developed will have to depend on the depth of the water. All previous types are

effective when placed in the proper location (Dvorak, Archer, & Jacobson, 2010).

Some people find the offshore turbines ascetically unpleasing and that they ruin the view of the

ocean and their concerns must be taken into consideration. Also, there is potential harm to sea

life when these turbines are developed as well as birds that might cross the turbines path.

Offshore wind turbines have a huge potential to be effective if more research is done and more

technology is developed.

Site Specific Development:

Fuglsang and his coauthor present a method for site-specific design of wind turbines. The

purpose of this study was to use an algorithm to optimize a turbine for a specific location. The

idea is that if turbines are designed to be location specific, they will operate more efficiently.

They produced an algorithm to insert certain features of a specific site and it would in return

produce characteristics of a specific turbine that could reduce the costs of producing energy

(Fuglsang & Thomsen, 2001).

The study also determined that when both onshore and offshore wind turbines are optimized for

a specific location, “…offshore wind farms showed a potential increase in energy production of

28% for the offshore wind farm, but also significant increases in most fatigue loads and in cost

energy” (Fuglsang & Thomsen, 2001). Offshore farms produced more energy but the energy

produced cost more. This finding is also significant because it makes clear the potential of

48

offshore wind turbines, which can be further increased if research is done to reduce initial costs.

Conclusion:

Based off the articles I have read I conclude that they provide my team with the necessary

information to select an appropriate location for the turbine we are developing. The location we

select will allow it to operate at maximum efficiency and minimal cost. One article in particular

provided information about an algorithm that can be used to determine the characteristics for a

turbine based on the specific site that its going to be developed in. Overall, it became clear that

offshore wind technology has more potential to produce large amounts of electricity compared to

onshore turbines. By scouting out effective areas offshore, such as off the coast of California

and locations on the east coast, the turbine we are developing can operate most efficiently. The

articles also give insight to what locations don’t work for the development of wind technology

and that there are a variety of factors that must be taken into account when selecting a location

including the environment, population, proximity to the power grid, and proximity to rail or

highways to transport the turbines parts for construction.

Recommendations:

Based on reading these articles, I would make the following recommendations for our project:

Locations where the company wants to develop our groups newly developed turbine must be

scouted and researched. This must be done in order to find a site that would enable our turbine

to operate most efficiently and at a minimal cost. The sites where these turbines are going to be

placed must meet a certain criteria. The turbine must be in a location that does not negatively

affect wildlife or human population. The turbine must somehow be connected to the power grid

to allow for the effective usage of energy. The location must have high wind speeds and an ideal

wind turbine climate. Lastly, locations must have some proximity to rail or highway if it is

onshore. If offshore, it must be easily accessible by boat. Based on the research I have done, I

would recommend our group to look for an offshore location for our newly developed turbine.

Offshore wind turbines have been proven to produce more energy, on average, than onshore

turbines. I believe the turbine we develop will operate at its maximum potential in an offshore

location. Another benefit of offshore turbines is that they are far enough from the public and

therefore don’t interfere as much as onshore turbines. They also don’t take up landmass. The

team also now knows what locations to avoid when selecting a site for our turbine. This ensures

that our team’s hard work does not go to waste and that our turbine is placed in a location that it

can be most effective. Overall, I would recommend that the team pursue a location that is

offshore and meets the above criteria.

49

To: Professor Fellows, WTSN 104, Section 57

From: Stephen Valvo

Date: 2/12/14

Re: Research Paper #1

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any wind conditions.

Introduction:

Wind energy has recently become a quickly growing field, and wind turbines have been

increasing in efficiency every year. However, horizontal axis wind turbines do not always face in

the direction of the wind. In addition, the big blades of the turbines often result in several avian

casualties each year, and many people do not support these wind turbines near populated areas

because they are not aesthetically appealing. There are many approaches that can be taken to

improve these wind turbines. One of the areas that can be improved upon is the materials of the

wind turbine. This paper will discuss the current materials that horizontal axis wind turbines are

using, and the alternatives that can increase the durability, reliability, and decrease the cost of the

turbines. The logistics of transporting these materials will also be discussed in this paper.

Current Wind Turbines:

Horizontal Axis wind turbines have 3 main parts: the nacelle, the rotor, and the tower. Each of

these parts can be broken down into several other components, for example the blades are a

component of the rotor. Since there are different parts of a wind turbine, the parts are sometimes

made in different sized so they can output a certain amount of MW (Mega Watts). These wind

turbines all have their specific requirements for each of their respective parts, both in size and

material. Changing the materials that wind turbines are made out of is one way to increase

efficiency and overall electrical output.

A typical wind turbine today contains about 89.1% steel, 5.8% fiberglass, 1.6% copper, 1.3%

concrete, 1.1% adhesives, 0.8% aluminum, and 0.4% core materials, such as foam, plastic, and

wood (U.S. 7). However, with new technology these percentages will likely change, and new

materials will be integrated into wind turbines.

The Tower:

There are some basic requirements that the tower of the wind turbines must meet. First and

foremost, the towers must be strong and must be able to hold the weight of the blades and the

nacelle. The nacelle accounts for about 25-40% of the weight of the turbine, and the nacelle

accounts for most of the energy conversion (U.S. 10). So, it is very important for the tower to be

able to support the nacelle, which is very heavy. In addition, the towers must be able to forces

from the wind, so therefore they must be stiff and strong (Hogg, 3). Most of the turbines today

are on-shore, so it does not really matter if they are light or not, however if a turbine could be

50

made from lighter materials it would reduce the cost of production and the cost of transportation,

especially when transporting the turbines off-shore. Currently, the towers are made of mostly

steel. However, steel is very heavy, and also can result in issues with respect to corrosion.

However, steel is used because it is very strong and cheap to produce. One material that can be

used as an alternative to steel in the towers of wind turbines is concrete. (Hogg, 6) If a hybrid

steel is used (Steel & concrete), the cost of production will still be cheap, the tower will still be

strong, however corrosion will be less of an issue, thus resulting in a longer lasting wind turbine.

Using concrete in conjunction with steel does not solve the weight issue, however. To solve this

issue, carbon fiber could be introduced to the towers, because carbon fiber is strong, yet light in

weight and cheap to produce. (Hogg, 6).

Rotors:

The most important part of the rotor is the blades. The blades must be aerodynamic so they can

generate enough torque to run the generators. While the blade design is very important, the

materials that are used in the blades are also very important. The blades of the wind turbine must

be stiff enough so they do not hit the towers when the wind is strong, but they must also be light

so they can rotate in lower wind speeds (Hogg, 10). The material that is used for the blades of the

wind turbines must be light, but also stiff. As stated by Professor Hogg, “Reducing the weight of

the blades also will directly reduce the loads on the tower and foundations” (13). So, materials

that have a high stiffness and low density will be the best choices, and based on these

requirements composites should be used.

Transportation of Parts:

While it is important to consider the materials that are selected for wind turbines, the

transportation of the parts from the manufacturing plants to the location of the turbines must also

be considered. One of the major logistical issues with the transportation of wind turbines is the

short-term availability of equipment large enough to transport such large parts, and the lack of

experienced personnel to transport, construct, and operate this equipment (U.S. 13). The

components of wind turbines are so difficult to transport because they are so large and heavy, so

they require special handling. Therefore, the cost of transportation is very expensive, which is a

huge obstacle. This cost can be even larger if wind turbines are being erected off-shore, because

the components of the turbines not only have to cross land, but they have to cross large bodies of

water, where weight becomes a major issue. There are two solutions that are possible to solve

this huge obstacle of transportation. First, the parts of the wind turbines can be made from lighter

materials, as discussed earlier. Second, the parts of the turbines can be manufactured in sections.

This way the parts will not require such special equipment to transport them, and they will be

easier for cranes to handle when erecting the wind turbines.

A New Goal:

One of the goals stated in the U.S. Department of the Interior U.S. Geological Survey report is

for 20% of the energy supplied in the U.S. to be supplied from wind energy. This is a goal that

our team can meet, and even surpass with a newly designed turbine. However, some there are

some basic requirements that are necessary to meet this goal, and there are areas of wind turbines

51

that can be improved upon to help reach the goal. The average life span of a wind turbine is 20 to

30 years (U.S. 11). If new materials are implemented in wind turbines, and maintenance utilities

are improved, the life span of wind turbines can be increased.

52

To: Professor Neuberger, WTSN 104, Section 57

From: Ryan Yetter

Date: 2/19/14

Re: Research Paper #1

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any wind conditions.

Introduction:

For many years, scientist and engineers have attempted to create a new and improved wind

turbine that would be able to maximize electrical output in a multitude of varying wind

conditions. A large variety of wind turbines have been developed over the years in order to

combat this problem of being able to adjust efficiently to varying wind speeds and directions. A

key to making wind turbines efficient is their geographical placement, and how the placement of

wind turbines is key to their output and efficiency. Many wind farm locations are based on years

of meteorological data to find key efficient cost effective locations. Many failures in these

designs are their inability to be cost effective or are dangerous to both people nearby and

wildlife. In addition, another major problem of wind turbines is the noise caused by the fan

blade, and how this causes disturbances to those living nearby the wind turbines farms. Our goal

is to produce an efficient, cheap, reliable and safe wind turbine that can maximize its electrical

output.

Wind Power Meteorology:

Wind Power Meteorology is a term that refers to meteorology and how it influences wind

turbines, as well as how wind turbines influence meteorology. The use of Wind Power

Meteorology is also important in the prediction of power output and efficiency of wind turbines

based on the weather. These short term power output predictions in addition to the use of

meteorological data in order to find efficient locations for wind turbines, furthermore making the

wind turbines cost efficient.

The use of Wind Power Meteorology is key in figuring out the wind climatology of a specific

location. In order to do this meteorologists need to input specific key information about the

region. These include; the position and dimensions for sheltering obstacles, roughness of the

terrain, as well as height contour lines for mountainous terrain (Petersen, Mortense, Landberg,

Hojstrup & Frank p. 9). With these inputs meteorologists can receive the wind climatology of

specific regions, and use this information in order to determine efficient cost effective locations

for wind turbines. The wind climatological description and classification of a particular location

is not simple to determine, however. Many different types of wind statistics are considered for a

description of wind climates and vary with local or regional progressions. However accurate

these wind climatology models are, they are only good for a short period of time, this is because

variability is a basic feature due to the fact that climate and the weather changes from year to

year and also between consecutive decades. In some studies it has been shown that an analysis of

53

the expected power output for a 45-m high wind turbine over a 22-year period is such that the

variation, between the years, in power corresponds to an average standard deviation of 13%

(Peterson, p.12). Even with these accurate statics on wind turbines and the correlations between

efficiency and wind patterns we can still see the need for more efficient wind turbines in these

ever changing climates. Other limitations of Wind Turbine Meteorology are based upon the

mathematical equations used to find wind climatology are fairly new and are still being reworked

in order to get the most accurate data.

There are many takeaways from the research of Erik Peterson and his colleagues. The first is

combining the use of meteorology and wind turbines creates a way for determine efficient

locations for wind turbines. Also, meteorology and its uses to predict power outputs from wind

turbines can be useful in fulfilling supply and demand needs for consumers and the power they

need. However, we can also see how unpredictable the climate can be and how much it can vary

from year to year creating headaches for planning of wind turbine locations in the future. Our

team will attempt to use this knowledge in the future to help plan locations for new wind turbines

as well as being able to predict whether or not a wind turbine will be cost efficient.

Estimation of Wind Turbine Power Generation

New advancements in wind turbine technology and finding areas of rich wind resources are

aiding the growth of wind power. Even with these new advancements in the wind turbine

industries, when wind turbines are spread over large areas of land such as wind farms then there

is an inherent variation of wind power produced by any singular wind turbine. These variations

in the power generated are due to variations in wind speed and direction. Measured wind data is

seldom identical to that seen at the generator for a variety of reasons, including the expense of

obtaining and maintaining that data as well as topographical constraints (Li, Wunsch, O'Hair, &

Giesselmann, 2001).

In this study, the researches look at the Fort Davis wind farm and use the twelve turbines located

there as well as two meteorological towers. The first study was the influence of wind velocity on

turbine power generation. With this study they were able to find the proper performance curve

that ended up to closely resembling that of manufactures specifications. At wind speeds between

30 and 40 mph, the wind turbines output was at 500 KW on the optimal output curve which is

also level and is at its maximum value. The current generated is proportional to the generator

shaft torque, this is however limited by controlling the torque produced by the turbine blades.

This is accomplished by using ailerons at the tip of the blades to reduce the blade lift (Li, 2001).

Another influence on wind turbine power generation is wind direction; however, the researches

came to the conclusion that wind direction has a minimal effect on the power generated because

each turbine is designed to face into the wind while operating. The bigger concern for creating an

efficient wind turbine based on wind direction is varying wind directions, and how it becomes

hard for turbines to adjust to these changing wind conditions (Li, 2001).

Due to the patterns and data found at Fort Davis wind farm we can now use this information to

predict wind farm power outputs. This also helps wind farm networks in two ways. First, the

scheme can greatly reduce the size and complexity of the neural network of wind farms. Second,

the operation of a wind farm usually requires some of the wind turbines to be off-line. These new

54

schemes of a neural network for each turbine will not be influenced by the turbines that are off-

line. Third, this approach scales better for large wind farms making it more economically

feasible for future use (Li, 2001).

Conclusion

The conclusion I have made from these reports and how they affect our project is that they have

provided me with valuable information that has increased my understanding and knowledge, and

will also help my overall teams understanding of how to determine wind turbine locations based

on geography and meteorology. This will help form a solution that uses these methods in

forming our plan for a more efficient wind turbine. These articles also show potential

weaknesses in the designs and locations of wind turbines based on average wind speeds and

directions. Wind turbines have the potential to become very economically feasible as well and

efficient by using the methods described in these reports.

Recommendations

Based on the reports I have read, I would make the following recommendations for our project:

We should further look into the use of the provided wind farm power output projections as we

move forward as a way to understand if our wind turbine will be efficient, as well as cost

effective. We should also look into the location of the wind turbine because the location of the

wind turbine greatly affects the power output of the wind turbine and the efficiency. Finally, I

would recommend for our team to further look into research on the correlation between

geography and wind turbine efficiency.

55

Appendix G: Research Paper 2

To: Professor Neuberger, WTSN 104, Section 57

From: Adam Suda

Date: 4/11/14

Re: Research Paper #2

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any wind conditions.

Alternative Solution:

Our mechanism will feature a sensor that will determine the position of the wind, and will then

send electronic signals to a motor that will, through a series of gears, turn the nacelle of the wind

turbine to face the wind.

Question:

How powerful will the motor need to be to turn the nacelle?

Answer:

The motor, or motors needed to turn the nacelle and blade assembly will have varying size

depending on how large the turbine will be. One of the most common wind turbines in use

currently is the GE 1.5 megawatt model (GE, 2009). For this model the nacelle which houses the

gearbox and the turbine weighs approximately 56 tons, with the attached blade assembly

weighting 36 tons. Our motors will have to be able to turn this huge, near 92 ton mass (Givens,

2002). The easiest way to do this is have the upper assembly on a series of high load bearings so

as to reduce friction and to have our motors go through a gearbox to increase torque. While this

will decrease the speed at which the assembly will move it will result in lower energy needs and

smaller motors being used. Regarding how strong these motors will need to be, it will largely

depend on how many are installed. For an even load across the whole tower and on the gear

system four seems to be the industry standard, with the motors being inside the nacelle and

acting as pinions against a large gear that sits atop the tower. According to industry standards the

largest wind turbines demand torque approaching 200,000 newton-meters, before gearboxes are

even added to the equation (Rusca, 2010). This seems to vary largely depending on how large the

turbine is. Thus while it would preferably have a one-size-fits all evaluation for the power

needed to rotate the turbine, it would be more cost efficient to have different motors for different

sized turbines.

Question:

What system of gears will be needed for the system to operate?

56

Answer:

The most common system for yaw drives to operate is to have a circular gear with teeth facing

inwards. The yaw drives act as pinions and rotate the top of the tower, with the gear being bolted

and held in place to the tower. The nacelle itself rests on a series of high load bearings so that it

can rotate smoothly, with these bearings reducing friction and torque required to rotate. The

drive yaw also go through a series of gears that reduce the rate of rotation, but increase torque

produced so as to move the massive load above it. This will result in slow response but requires

less power, and fewer resources spent on motors and gears.

Question:

Which varieties of wind detection sensors would be optimal, and how many sensors are needed

to be able to respond properly to wind changes?

Answer:

The main variety of wind measurement instrument needed would be an electronic wind vane,

which responds to wind changes and sends an electronic signal or data to an onboard control

system(Schienitzki, Strobl, Gutierrez & Gräber, 2014). For our purposes this seems to be

adequate, but for the purposes of recording conditions at the wind turbines it would likely be

wise to have an anemometer which would record the speed of the wind to determine if the site

has consistent wind speeds, and if perhaps the wind turbine is not well placed. Likewise,

temperature, air pressure and humidity all play a role in how much energy is produced by a given

turbine, so sensors to record this data may be very worthwhile if evaluating the worth of a

particular site. Another worthwhile instrument would be a barometer to measure air pressure so

that in case of low pressure which could indicate an incoming storm the turbine could

automatically turn off to protect itself from high winds. However for our purposes of only

determining where the wind is coming from just a wind vane would be sufficient.

57

To: Professor Neuberger

From: Brandon Okraszewski

Date: March 12th, 2014

Re: Research Paper #2 – Edit for Final

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any wind conditions.

Alternative Solution:

The Fan Mechanism is a device that resembles a helicopters tail and it will be attached to the

upper portion of a wind turbine. The device will utilize a fan (rotor) at the end of the tail to vary

its position.

Question:

How does the tail rotor of a helicopter operate (Also on what axis)?

Answer:

In most helicopter designs, a single rotor mounted on top of the helicopter provides upward

thrust, with the force of wind pushing down on the ground to allow the vehicle to elevate.

Orientation of this rotor determines altitude and position; angled forward will allow for

propulsion whereas a level rotor will allow the helicopter to elevate. This main rotor, however,

produces torque, causing the copter to rotate uncontrollably with the rotation of the rotor.

One of the first documented solutions to this problem was by Wilheim von Achenbach in 1874.

The German inventor proposed a tail rotor to act against the rotation. The tail rotor generates a

sideways thrust that compensates for torque produced by the main rotor (Gordon p. 4). A rotor is

placed at the end of the tail perpendicular to the main rotor, allowing for the counteraction. The

rotor uses three to five percent of the main rotor power during normal flight, and up to twenty

percent during extreme conditions (Gordon p. 226).

As a negative consequence to the addition of a tail rotor, helicopters become a minor

inconvenience to civilians. While the main rotor generates lower frequencies, the tail rotor

generates higher, more discernible frequencies that are more noticeable to the human ear

(Gordon p. 315).

The proposed solution of a fan mechanism is used to produce, rather than act against, torque that

will allow wind turbines to rotate along a horizontal axis. Understanding the workings of a tail

rotor for a helicopter allows for understanding of energy and mechanical outputs of a tail rotor

built with the mechanism of a wind turbine.

Application:

58

Tail rotor follows same mechanics as helicopter tail rotors in which the rotor and tail are

positioned perpendicular to the main fan and tower. A motor in rotor will allow the wind turbine

to spin on command when wind patterns are detected by sensors mounted on the mechanism.

The rotor will then generate torque perpendicular to the fan to allow the turbine to shift position.

Cases in which energy is unavailable to power the motor of the rotor, wind that does not go to

the main fan directly will instead move through rotor, thereby moving the tower on a horizontal

axis without use of a motor.

Question:

What materials are currently used in helicopters tail rotor?

Answer:

Helicopter blades are typically made of composite materials to be light enough to allow the

thrust of the main rotor to elevate the vehicle, yet durable enough to withstand the forces of

rotation of the rotor. A study determined composite graphite/epoxy to have lowest weight, and

composite boron/epoxy to be most compact (Murugan p. 11); different compositions will yield

different configurations, each with varying benefits.

Helicopters with main rotors that rotate on a fixed axis tend to vibrate, thereby decreasing control

capabilities. Depending on materials used to construct the blades, the rotor can become deformed

and lose aerodynamic capabilities. Straub and King (1996) suggest the use of smart materials,

materials that change shape under the influence of electrical, thermal or magnetic stimulation, to

adapt to different conditions. Blades of the rotors that alternate shapes allow for less deformation

by changing in response to a change in environment.

Application:

In relation to the solution, determination of the proper materials will allow for a stronger, more

effective tail rotor. Ability to manipulate the blades of the tail rotor lowers the frequency of

deformation and thus lowers the necessity for maintenance. Since a tail rotor on a wind turbine

requires strength rather than low weight, material of the rotor should be a composite similar to

boron/epoxy. The tail rotor of a wind turbine will not need to be significantly aerodynamic; as a

result, a composite blade should be used rather than a smart material blade. Accommodations for

change in environment will be relatively unnecessary in the case of a wind turbine.

Question:

What type of braking system would be most effective?

Answer:

Frictional braking uses frictional surfaces to slow and stop an object. The first brake lining using

frictional braking was introduced by Henry Ford in 1897 (Blau p. 9). Initially, cast iron on steel

and woven fibers of asbestos with brass wires were used as brakes in railroad cars and early

59

automobiles respectively. Over time, carbon fibers were suggested and are now used in

automotive brakes. This form of braking is occasionally unreliable, requiring replacement and

maintenance as the friction material is worn down by continuous use.

In electromagnets, a piece of metal is placed inside a coil of conductive wire. Applying a current

to this system and closing the circuit will cause the metal to become magnetized with poles

corresponding to the flow of the applied current. The Magnetorheological suspension (MRS)

braking system utilizes an electromagnet placed between two MRS disks (Bica 2003).

Essentially, once a current is applied, the electromagnet attracts the two disks, locking the system

and preventing motion. Using this form of braking poses difficulty in that a power source is

constantly required during times when the fan is locked in place.

Determination of which braking system to use will allow for a reliable rotation system. Between

frictional braking and electromagnetic braking, the latter is more effective in that it requires less

maintenance and prevents stronger movement than frictional braking. As a result, the fan tail

mechanism must use electromagnetic braking as the most effective system to prevent movement

after the mechanism is in an optimal position.

Application:

Braking system must be applied to the frictionless rotating piece to allow the mechanism to

orient the fan directly in the path of oncoming wind. Without the brake, the fan will continue to

rotate uncontrolled. Using a ball bearing [Figure 3], the turbine will rotate with little friction,

creating the problem of relatively continuous rotation. With the use of an electromagnetic brake,

a battery must be stored within the mechanism to allow for braking when lacking power.

60

To: Professor Neuberger, WTSN 104, Section 57

From: Brian Parsons

Date: 3/30/14

Re: Research Paper #2 – Edited

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any wind conditions.

Alternative Solution:

Our team’s solution is a downwind turbine rotation mechanism. Downwind turbines offer many

benefits over the traditional upwind turbine designs. These benefits make downwind turbines

more suitable for harvesting wind energy than upwind turbines under unique geographic and

atmospheric conditions. Downwind turbine designs take advantage of drag from the wind to

rotate into the ideal position automatically without the any need of any additional energy or

components.

Question:

How would the energy generated be affected by having a turbine on a frictionless rotation system

compared to other rotation systems?

Answer:

This is a complicated question as there are many factors to consider. If compared to the most

common alternative system, the upwind motorized active yaw drive rotation mechanism, the

energy yield is nearly identical on flat geography. This is due to the energy being spent to

operate the sensors, computers, and motors being offset by the energy lost to tower shadow in the

downwind turbine design. But if the geographical location is changed to an uphill or

mountainous location, the downwind turbine design quickly becomes favorable over the upwind

turbine design. This is due to the angle of incidence the wind has with the blades of the turbine in

a mountainous location (Manwell et al., 2002).

Application:

Our team is designing a mechanism to rotate a horizontal axis wind turbine. If all of the same

results (or more) of a traditional upwind motorized active yaw drive rotation mechanism can be

achieved by using a downwind free yaw drive rotation mechanism that requires less components

than alternative designs, it is obviously to our team’s benefit. Not only will energy output be

either on par or increased with a downwind design, but stability in destructive weather is

improved.

Question:

61

What sort of turbulence problems does a downwind turbine face compared to an upwind turbine?

Answer:

By locating the blades and rotor downwind instead of upwind, the turbine is subjected to wake

from the turbulence of wind flowing around the nacelle, known as tower shadow. Tower shadow

can result in uneven wind loads on the blades, creating fatigue over time. The effects of tower

shadow can be minimized by utilizing larger diameter blades and by making the nacelle more

aerodynamic and less obstructive to wind flow (Matsunobu et al., 2009). However, both upwind

and downwind turbines face wind shadow, characterized by fast and erratic gusts of wind to

different points on the turbine. This can also cause fatigue over time. Downwind turbines are

better equipped to deal with wind shadow than upwind designs because the free yaw drive

rotation system allows the turbine to simply rotate with oncoming gusts of wind and cushion

their blow than try to adapt after the fact using an array of sensors, computers, and motors

(Manwell et al., 2002).

Application

Our team’s design would have to take into account the associated atmospheric advantages and

disadvantages of using a downwind turbine system compared to an upwind turbine system.

Should a downwind turbine design be selected, our team’s design should make every effort to

minimize tower shadow and capitalize on the benefits of increased stability and less components.

Question:

How does the reliability of a downwind turbine compare to that of an upwind turbine?

Answer:

There are advantages and disadvantages of using a downwind system with regards to reliability.

The advantage of using such a system is it lacks the possible maintenance required for

components that an upwind system would have such as sensors, motors, computers, and

batteries. In addition, a downwind system manages wind shadow more effectively than an

upwind design. Wind shadow would result in strong, erratic wind gusts that could lead to fatigue

of the rotor and blades over a long time period (Manwell et al., 2002). However, the

disadvantage of a downwind system would be the long term effects of tower shadow. Similar to

wind shadow, tower shadow can also lead to fatigue of the rotors and blades, resulting in more

maintenance. However, with improved designs, tower shadow can be reduced for downwind

turbines (Matsunobu et al., 2009).

Application:

Our team’s design must take into account the overall reliability of using a downwind system

compared to an upwind system. The upwind system requires more components that could lead to

maintenance issues while the downwind system has the unique problem of turbine wake. Our

team must weigh both of these reliability factors when determining a solution.

62

To: Professor Neuberger, WTSN104, Section 57

From: Evan Kearney

Date: 3/12/14

Re: Research Paper #2 - Part 1

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any wind conditions.

Alternative Solutions:

Create a wind turbine that rotates with the help of a sail/tail vane and a frictionless surface.

Question:

What type of materials should be used for the design components?

Answer:

The design components being focused on in this question are the locking device “pegs”, the

“low-friction/frictionless” surface, and the tail vane. For the locking device pegs, a material that

is a strong and resistant metal is desired. For the low-friction/frictionless surface, a material that

is strong enough to support the top of the wind turbine, but smooth enough to rotate the top

easily is desired. For the tail vane, a material that is durable with a long lifetime is desired.

For the locking device pegs, the material that may be best suited for the design is

titanium/titanium alloys. The locking device pegs need to be strong. They need to be able to stop

the top of the wind turbine from rotating without causing any damage to the pegs themselves or

causing any stress to the structure as a whole. Titanium is a transition metal with low density and

high strength. It can be alloyed with other metals such as iron to produce strong light-weight

alloys for many applications. Pure titanium has an ultimate tensile strength of about 434 MPa,

and alloys can reach a tensile strength of over 1400 MPa. This strong metal is guaranteed to

efficiently perform its intended job for the locking device. (“Titanium (Ti),” 2014)

For the low-friction/frictionless surface, the materials that may be best suited for the design are

mechanically strong hydrogels with ultra-low frictional coefficients. The materials for this part

of the design must be very strong. Studies have previously shown that “the presence of

polyelectrolyte brushes on a hydrogel surface can effectively reduce sliding friction coefficients

to a value around 10-4.”(Kaneko, Tada, Kurokawa, Gong, & Osada, 2005) The problem with that

technique is that the conventional hydrogels are not strong enough to be used in any type of

strength bearing situation. Therefore very strong hydrogels are needed for this task. A new gel

that contains 60-90 percent water shows fracture strengths as high as 9 MPa and a frictional

coefficient as low as 10-5. With some rearranging in the mechanism, this “DN” Gel may be the

answer for the low-friction/frictionless surface. (Kaneko et al., 2005)

63

For the tail vane, the material that may be best suited for the design is glass-fiber-reinforced

plastic, or GFRP. There are multiple reasons why GFRP is a preferred material to use. One

reason GFRP would be an excellent material, is because it has a very high strength to weight

ratio. The tail vane would be lightweight, but be strong enough to rotate the wind turbine.

Another reason is because it has great resistance to the environment. It will not be affected by

acid rain, salts, or most chemicals. The final reason it is a great material to use is its low

maintenance. GFRP can potentially show no signs of wear even after 30 years. (Oehlers, 2004)

Application:

The main focus of our problem statement is to develop a mechanism that will optimize the

energy output of the wind turbine. One of the main aspects we have to focus on is a design that

will be able to harvest energy, without having to spend any energy. Wind turbine mechanisms in

the present run on an electric-powered motor yaw drive. It is important to try and think of as

many ways as possible to develop a mechanism that runs free of electricity. One of the most

important parts of these developing mechanisms is the materials. The designs need to make sure

that the wind turbine is sturdy, reliable, efficient, and low maintenance, and the materials used

need to ensure that the design meets these criteria.

Question:

How will the locking device work?

Answer:

The locking device is incorporated into the mechanism design in order to make sure that the

wind turbine top doesn’t keep spinning around in circles due to the frictionless surface. It is also

created to lock the turbine into place at the best angle possible in order to allow it to harvest the

most energy. The locking device consists of a sturdy band wrapped around the turbine that has a

number of titanium pegs along the top. These pegs can jump up and fall down through the use of

pistons. In addition a titanium extrusion is included on the shaft of the wind turbine. This

extrusion should be perpendicular to all the metal pegs as it spins over them.

The locking device works along with a wind direction sensor, a program which monitors which

pegs jump up and which stay down, and a pressure sensor. As a group, these four devices are

used to lock the wind turbine in the optimal location given the present wind conditions. The wind

sensor senses wind direction and sends the information to the program. The program then

calculates which angle the wind turbine needs to be with respect to the ground in order to be in

the best position for energy harvesting. With this information the program will activate the piston

to push up the specific titanium peg that will put the turbine in the best position. As soon as the

turbine extrusion hits the protruded peg, a pressure sensor will go off and the adjacent peg will

pop up completely locking the turbine extrusion into place. This will not allow the turbine to

rotate anymore. When the wind changes direction, the sensor will send the information to the

program, and both pegs will drop allowing the turbine to rotate into its new position.

64

Application:

Because our mechanism is not running on electrical power, we need an addition in order to help

maintain the wind turbines position. The locking device that has been developed could be a great

option to help with this problem. With an expert programmer, wirer, and sufficient

meteorological devices, the locking device presented could be a real possibility. The position of

the wind turbine is the most important part of energy-harvesting. If the wind turbine is not in a

good position, the energy gathered will not even come close to its potential. Therefore a locking

device is definitely the most important aspect of our mechanism.

Question:

How would the mechanism sense wind direction?

Answer:

The mechanism would sense wind direction through the use of an already created device. The

WindSonic™ Sensor is a wind vane that measures wind direction only. It can be attached to

many surfaces using a sensor mounting kit. Therefore it can easily be mounted near or on top of

the wind turbine, in an area where the wind will not be redirected leading to false readings. The

wind sensor works with four ultrasonic transducers arranged as two pairs at right angles to each

other. Each pair is used to measure the component of the wind in the direction between the

transducers: the North-South component and the East-West component. In order to find the wind

angle the components are combined. The wind angle is equivalent to the arctangent of the East-

West component divided by the North-South component. (Gill Instruments, 2011)

Application:

In order for the designed locking device to work, a wind sensor is necessary. We do not have the

expertise in the field of meteorology in order to create the device; therefore we have to use a

previously created device. The sensor determines wind direction through the use of simple

trigonometry. As mentioned earlier, the position of the wind turbine is the most important part of

energy-harvesting, and this sole device is the powerhouse of identifying the wind turbines

optimal position.

65

To: Professor Neuberger, WTSN 104, Section 57

From: Lucy Lin

Date: 3/12/14

Re: Research Paper #2 – Part 1

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any wind conditions.

Alternative Solution:

Our team’s solution is a downwind turbine rotation mechanism. Downwind turbines offer many

benefits over the traditional upwind turbine designs. These benefits make downwind turbines

more suitable for harvesting wind energy than upwind turbines under unique geographic and

atmospheric conditions. Downwind turbine designs take advantage of drag from the wind to

rotate into the ideal position automatically without the any need of any additional energy or

components.

Question:

Why are most wind turbines facing the wind?

Answer:

In the past, downwind turbines were not viewed as a feasible alternative due to the presence of

tower shadow. Tower shadow refers to the turbulence created from the blades being located

behind the nacelle instead of in front of it. Having the turbine blades behind the nacelle may

eventually result in fatigue in the blades over time (Obeyanji, Faust, Santos & German, 2009).

Due to the large amount of maintenance and cost associated with the problem of tower shadow,

up wind turbine designs were preferred. Now with new technology, engineers have found ways

to increase the diameter in blades, diminishing the presence of tower shadow and conserving the

energy that was once lost due to it. This can be especially beneficial in mountainous regions such

as Japan because down wind turbines are more efficient when placed on top of a hill due to the

direction that the wind is travelling in ("Downwind Rotor," n.d.). Since the primary problem that

was associated with down wind turbines is now addressed, this mechanism is now becoming a

viable and favorable alternative to up wind turbine designs.

Application:

Our team is looking at down wind turbines as part of our alternative solution. In order to make an

efficient turbine design, we must look into additional ways to eliminate, if not highly diminish

the presence of tower shadow. We will find the optimized length for the diameter of the blade in

order to minimize the presence of tower shadow, along with creating a more aerodynamic

nacelle (Tong, 2010). By implementing both features, down wind turbines will yield a greater

energy output than up wind designs if placed in a specific location. Down wind turbines are more

66

effective when placed on a hill or a mountainous region due to the wind striking the blade in a

perpendicular manner, as opposed to in a parallel manner in an up wind turbine design, thus

increasing the energy yield (Matsunobu et al., 2009). Even on flat ground, down wind turbines

generate almost the same amount of energy as up wind turbines which means that it is as good, if

not better than up wind turbine designs in terms of generating energy.

Question:

How does wind behave at the height of the turbine? Is wind gusty or random?

Answer:

At higher altitudes, wind conditions are more consistent and easier to predict. In addition, the

speed of the wind also increases as the height increases (Obeyanji, Faust, Santos & German,

2009). This is an important concept to note as it explains why most wind turbines are built at

higher heights. According to the velocity-cubed law, when all other parameters are the same,

doubling the velocity in turns creates three times the amount of power (Obeyanji, Faust, Santos

& German, 2009). This means that with a greater amount of wind speed, the available power

generated is significantly increased. Also, wind flowing uphill is beneficial to down wind turbine

designs due to the direction in which the wind is striking the blades as mentioned earlier

(Matsunobu et al., 2009). Although wind conditions, are for the most part, predictable at higher

altitudes, in the case of very high winds or irregular wind patterns, the application of using a

down wind turbine design will allow the load of the wind to be transferred from the blades to the

tower (Obeyanji, Faust, Santos & German, 2009). This decreases the reliance on the structure,

making it safer but may also cause fatigue to the blades over time.

Application:

Our team’s design must address the fatigue that a downwind turbine causes the blades of the

wind turbine. Even though this is a vital problem to address, it is also important to keep note that

one of the benefits of having a down wind turbine design is that it relieves the stress from the

tower by directing it to the blades (Obeyanji, Faust, Santos & German, 2009). Thus, in each

design, at least one component of the turbine is receiving the pressure generated by the wind in a

negative manner. In addition, although wind speeds are faster at greater height which results in

more power, one must also note that having a structure at such heights comes with a change in

temperature, an increased possibility of liabilities, a rise in costs and higher exposure to

turbulence (Obeyanji, Faust, Santos & German, 2009). Thus, it is important that our team will to

make the right adjustments to make sure that an increase in power output would not sacrifice the

overall efficiency of the turbine.

Question:

Would the turbine be naturally inclined to turn if the yaw drive was frictionless?

67

Answer:

The yaw drive currently is used to make sure that the rotor of the wind turbine is facing the

direction of the wind at all times, regardless of the current wind condition. If the drive were

frictionless, the turbine would be naturally inclined to turn due to the drag of the wind.

Additionally, if there were large gusts of wind, the frictionless drive will be more adept in

handing it because it would be capable of moving freely, adjusting itself to counteract the drag

created by the wind. In case of black outs, an up wind turbine design would be unable to

function. However, with downwind designs, the low friction yaw drive would cause the blades to

rotate automatically without the use of electricity. A frictionless yaw drive in down wind turbine

designs also addresses the problem of wind shadow. Wind shadow is when a random gust of

wind hits the blade of the turbines, shaking the structure (Obeyanji, Faust, Santos & German,

2009). An up wind design has sensors to adjust to the condition but with a downwind design, it

rolls with the gust of wind automatically. It wasn’t until recently that down wind turbines

became a real possibility due to the decrease in blade radius. When the radius of the blade was

smaller, wind shadow caused significant damage to the blades over time (Matsunobu et al.,

2009).

Application:

Our turbine design has to be able to rotate on a low friction yaw drive, which increases the

effectiveness of the structure. Now that we have the technology and the ability to create larger

turbines, the effects on tower shadow on large radius blades are reduced significantly. The

frictionless yaw drive will allow the turbine to function during black outs and harsh wind

conditions. The problem of wind shadow is reduced, and all of these benefits make having a

down wind turbine with a nearly frictionless yaw drive a viable possibility. For the design to

function better than its counterpart up wind structure, it needs to be placed on a hill or a

mountainous terrain. On flat land, however, although the two designs generate essentially the

same amount of energy, our design features no complex motor or computer system, lowering the

costs and maintenance. Our team will also address the current problems of wind shadow and

tower shadow by adding in a more aerodynamic nacelle and making the blade radius larger and

in a different shape.

68

To: Professor Neuberger

From: Maxwell Brown

Date: March 19th, 2014

Re: Research Paper #2 – Part 2

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any wind conditions.

Alternative Solution:

The Fan Mechanism is a device that resembles a helicopters tail and it will be attached to the

upper portion of a wind turbine. The device will utilize a fan (rotor) at the end of the tail to vary

its position.

Question:

What type of material or surface allows for rotation while requiring the smallest amount of

energy?

Answer:

In order for the mechanism to be useful, it must be able to effectively rotate the upper portion of

the turbine 360 degrees about the vertical axis. A mechanism that would require a tremendous

amount of energy to rotate would not be favorable in the final design. A favorable design would

require little to no energy to enable rotation. That is why a low friction surface is desired for the

mechanism. The lower the friction, the lower the amount of rotational energy required and thus,

a better design.

Magnetic bearings have been on the rise within the last 30 years. They have come down in cost

and have become more practical to be used in mechanical machinery. Traditionally, a magnetic

bearing would be used for high-speed mechanisms, however; this technology can be potentially

used for large rotational objects. Magnetic bearings operate with negligible friction and are very

reliable and predictable. They work by providing an electrical current to magnets that in return

suspend an object in the air and allow it to rotate freely. This technology could very well be

applied to the fan mechanism design however; the cost for technology like this would be so

excessive that the turbine would end up costing money to operate (Eaton, 2010).

A superconducting zero friction surface is obviously strongly desired for this design. However,

this technology does not cost effectively exist yet and if it did, it would most likely not be used

for wind turbines. Instead, every home would have their own turbine that would rotate

theoretically forever and produce an infinite amount of electrical energy. Unfortunately, this is

not the case and a zero friction surface cannot be used for this design.

69

Fortunately, there are effective low friction surfaces currently used today. The traditional

bearing is used across all industries and there certainly is a reason why. The purpose of a

bearing is to reduce the friction between two connecting piece and allows for rotation.

Traditional bearings are used for all different types of rotational machinery. From airplane

engines to wind turbines, ball bearings play a critical roll in rotation. They are lubricated and

require maintenance often to be effective. Most bearings for ordinary mechanical use utilize

high carbon and high chromium steel (Wang, 2000, pp. 159-173).

The one issue with traditional ball bearings is that they experience problems due to the vibration

created between the two connecting pieces. This vibration damages the ball bearing and requires

increased maintenance. These problems however are easily overcome with regular maintenance

and lubrication. Overall, traditional ball bearings are the most desirable low friction surface for

this design (Huang et al., 2007, pp. 193-207).

Application:

Our team is attempting to design a horizontal axis wind turbine that can effectively rotate itself

into an optimal energy producing position. In order to do this, the mechanism must allow the

upper portion of the wind turbine to rotate. The only way to do this is to have a low friction

surface connecting the mechanism to the turbine blades and gearbox. Without a low friction

surface, a tremendous amount of energy would be required to rotate the upper portion of the

wind turbine and this would be both inefficient and costly. We have determined that using a

traditional ball bearing, technology that has been effectively proven in the industry for decades,

would be most effective for our design. Sometime it is better to us technology that is known and

proven than go out on a limb and try something that may fail. Traditional ball bearings work

extremely well and when they receive regular maintenance, they can operate with negligible

friction, which is strongly desired for this design.

Question:

How will the Fan Mechanism be powered?

Answer:

In order for the Fan Mechanism to normally operate, energy is required to power the fan (rotor).

Energy is required for the majority of the time while this mechanism is in operation. There are

rare instances when the Fan Mechanism can reposition itself solely using the power of the wind

and act like a fantail. For most of the time however, energy will be required.

There are multitudes of ways in which the mechanism can be powered. These ways range from

having the wind turbine power the mechanism to having an external power source power to the

mechanism. After careful consideration, it was determined that it would be most effective for

the mechanism to be powered by the wind turbine.

A recent study conducted by De Broe and his coauthors investigated the implementation of peak

power trackers on small-scale wind turbines. Peak power trackers effectively convert wind

energy into electrical energy. By using a peak power tracker, wind energy can be used more

70

efficiently and more electricity can be generated. In this study, the electrical energy created goes

directly to a battery bank for later usage. That electrical energy is either used to spin the turbine

blades and generate more electricity, is grounded (in standalone turbines), or enters the power

grid (in grid integrated turbines). The results of the study confirmed that the power tracker

increased electrical energy output significantly (Broe, 1999, pp. 1630-1635).

Application:

Our team is attempting to design a mechanism that can rotate the upper portion of a wind turbine

into an optimal energy producing position. In order for the upper portion of the turbine to rotate,

electrical energy must be used to spin the fan that can in return rotate the upper portion of the

turbine. This team determined that it would be most effective to have the wind turbine supply

the energy necessary to spin the fan. Based on the journal article by De Broe and coauthors, a

peak power tracker, when integrated into a small-scale wind turbine can significantly increase

electrical power output. Our pair has decided to implement that same technology into our

design. By implementing a peak power tracker into the wind turbine, wind energy can then be

converted into electrical energy. That electrical energy can then be stored in a battery connected

to the main hub of the mechanism. The electrical energy in the battery can then be used to power

the fan. This is by far the best way to power the mechanism and rotate the upper portion of the

wind turbine into an optimal position.

Question:

What type of sensor technology should the Fan Mechanism use determine when it needs to

change direction?

Answer:

A recent journal article published by Makinwa and Huijsing introduces a smart wind sensor that

has many applications. The journal article begins with an explanation of traditional wind sensors

and how they are inconsistent and unreliable. Traditional wind sensors have thermopiles that

output small insignificant data. Thermopiles are devices that convert thermal energy into

electrical energy. Because the thermopile output is small, complex circuitry is required to make

use of the data. Because the signals outputted are small, they are vulnerable to outside

interference during transport. This results in inaccurate data and an inaccurate representation of

the winds velocity (Makinwa, 2002, pp. 15-20).

The journal article introduces a new type of sensor, a smart sensor that can better predict the

wind within a 4% accuracy. This sensor uses thermal sigma-delta modulation techniques, which

allow for the increase in accuracy. These techniques involve moving the position of the

thermopiles, adding four of them, as well as adding a central diode. By taking these measures,

the accuracy of the sensor increased. The smart sensor that was created and tested in this journal

article was proven to significantly increase the accuracy of the sensors. More accurate sensors

lead to better data and thus a better way to determine the winds true direction. These sensors are

the best way of predicting the winds speed and direction (Makinwa, 2002, pp. 15-20).

71

Application:

Our team is designing a wind turbine that can adapt to its environment. The only way in which

the wind turbine can adapt to its environment is if it can effectively sense it. Our Fan

Mechanism must be able to reposition the wind turbine into a position that is optimal for

producing energy. The smart sensors as described in the journal article published by Makinwa

and Huijsing will be perfect for the Fan Mechanism. This sensor is extremely advanced and can

accurately obtain wind speed and direction data. Once that data is received, the Fan Mechanism

will utilize it and adjust its position. A simple algorithm programed into the Fan Mechanism will

convert the wind speed and direction data into coordinates. Once those coordinates are

determined, the Fan Mechanisms computer will notify the fan and the braking system to go into

effect and it will reposition the turbine accurately.

72

To: Professor Nueburger, WTSN 104, Section 57

From: Stephen Valvo Partner Name: Adam Suda

Date: 3/12/2014

Re: Research Paper #2 – Part 1

Problem Statement:

Develop a mechanism that would vary the position of a horizontal axis wind turbine to maximize

electrical output in any wind conditions

Alternative Solution:

Our mechanism will feature a sensor that will determine the position of the wind, and will then

send electronic signals to a motor that will, through a series of gears, turn the nacelle of the wind

turbine to face the wind.

Question:

What materials must the mechanism be made out of, and which materials will make the motor

the strongest?

Answer:

The materials that our yaw system will be constructed from must be extremely durable.

However, the materials of two sections of the yaw system must be considered: the structure of

the system, and the gears. The yaw system will have to directly hold the weight of the nacelle

and the blades of the turbine, which account for a large amount of the weight of the turbine. One

of the materials that should be considered favorably for the construction of this mechanism is

steel. Steel is already used throughout a lot of the turbine because it is extremely strong, and is

also easy and cheap to produce (Hogg, 2010 p.6). Using steel could decrease some of the costs

for the mechanism, and would also ensure that the mechanism can hold the weight of the nacelle.

The materials of the gears that will rotate the nacelle must also be considered, because there are

different forces acting on the gears than the structure, as the gears are rotating and forces are

acting from gear to gear. Often times, steel is used in gears due to its strength and low cost of

production. The materials that are selected for the gears must satisfy two requirements:

fabrication requirements and performance requirements. The fabrication requirements include

machinability and response to heat, while performance requirements include how the gears

actually function. (Davis, 2005).

Application:

Based on the research of materials of a yaw system, it is evident that steel should be used for

both the gears of the yaw drive, and the structure of the mechanism as well. Not only will this

decrease the cost of producing the mechanism, but it will also give the mechanism the maximum

strength and durability. Certain types of steel are used in different situations. Since our

mechanism will be inside the turbine, corrosion will not be a major issue, therefore stainless steel

73

will not be used in our mechanism (stainless steel is often used in gears to prevent corrosion)

(Davis, 2005). Based on a table from Joseph Davis’ book Gear Materials, Properties, and

manufacture, the steel grade that should be used for the gears is grade 1045.

Question:

How will the sensor detect the current wind conditions and relay the information to the motor?

Answer:

There are several different types of sensors that are used to detect wind conditions. Some sensors

are small and can fit in a person’s pocket, and others are designed to be used on wind turbines.

Obtaining the correct wind sensor for this mechanism and turbine is essential, because if the

sensor cannot withstand large wind gusts or a large temperature range, it is possible that the

sensor will break when on top of a wind turbine. When the sensor gets information about the

current wind conditions, it outputs voltage, which carries the information about the conditions

("Met one instruments ," ). This voltage then goes into some central intelligence, which reads the

information. In order to make the motor turn, the central intelligence that processes this data will

send a signal to the motor that will then turn the yaw drive, which turns the nacelle into the wind.

Application:

Our sensor system will feature both a wind speed sensor and a wind direction sensor. Our wind

speed sensor will be based off of the Met One Model 010C Wind Speed Sensor. This sensor has

an operating range of up to 125mph, or 60m/s ("Met one instruments ," ). However, the material

and strength of the sensor will be modified to increase the operating range. We will also use a

wind direction sensor based off of the Met One Model 020C Wind Direction Sensor, which will

also be modified to increase the sensor’s operating range and strength. The sensor’s will then

relay information to a central intelligence system that will finally rotate the yaw drive to face the

nacelle into the wind.

Question:

How will the yaw drive use energy that is generated from the wind turbine?

Answer:

When the blades of a wind turbine are rotating, the blades power a generator, which is the source

of the electricity that is generated from the wind turbine. This generator outputs AC voltage,

which can then be sent out of the wind turbine and out to other power plants, energy companies,

or homes or other buildings ("How does a," 2013). The motor that will run the yaw drive will

require energy to run, more specifically electricity. While motors usually have external power

sources, we need ours to run on the electricity that is produced from the wind turbine to satisfy

our requirements. However, this will do more than simply reduce costs by eliminating the need

74

for an additional power source. Since we will be recycling energy, we will be designing a

mechanism that is more environmentally friendly.

Application:

Since the wind turbine will not need to be constantly rotated, the energy needed to rotate the

wind turbine will be very small, especially since our mechanism will allow the turbine to face the

wind at all time, so it will always be producing electricity. After the electricity is produced in the

generator in the nacelle, some of the electricity will go directly to the motor to power it. There

will be no energy conversion needed because the motor can run on AC electricity, and the

generator that is in the wind turbine generates AC electricity.

75

To: Professor Neuberger, WTSN 104, Section 57

From: Ryan Yetter

Date: 3/12/14

Re: Research Paper #2 - Part 1

Problem Statement:

Develop a mechanism that would vary the position of horizontal axis wind turbines to maximize

electrical output in any wind conditions.

Alternative Solutions:

Create a wind turbine that rotates with the help of a sail/tail vane and a frictionless surface.

Question:

How much force can the tail vane produce?

Answer:

In order for our design to work we need to make sure that a tail vane can produce enough force

on its own to rotate the wind turbine. Through are research we have found that the force

produced by wind is dependent on many factors. Many researches use complicated formulas to

determine wind forces on structures. One of the simpler formulas to determine the force of wind

on a structure is, the surface area being exposed multiplied by velocity of the wind squared and

then multiplying it by the drag coefficient of an object. This formula accounts for the wind

pressure on the front of the structure as well as suction caused by the drag produced from the

wind going around the structure. This formula will be helpful when determining how large the

tail vane should be to rotate the turbine along with what forces the tail vane should be made to

withstand.

Question:

How much force is needed to rotate a wind turbine?

Answer:

The horizontal rotation of a wind turbine requires a lot of torque in order to rotate, because of

this many traditional wind turbines use high powered motors to rotate the hub. Through our

research we have found that the average output of the motors used to rotate a wind turbine is

about 42000 Nm. This is a large amount of force required, however, we can overcome this large

force needed by using a tail boom as seen in figure 1. A combined use of the tail vane and the tail

boom we can expect to see that the wind turbine can be rotated without the use of motors.

76

Question:

How cost-efficient will this idea be?

Answer:

The use of a tail vane constructed of glass fiber reinforced plastic, this material that has a very

efficient strength to weight ration and is also relatively cheap, is a great combination to make the

tail vane cost efficient. If we use the data we gathered along with the formulas we can create a

rough estimate of how large the tail vane should be along with the force we can expect. With

these two properties but together we can come up with the cost of the tail vane and boom to be

around thirty thousand dollars, at a cost of 65 per square foot. When you also add in the two

thousand dollars for the WindSonic device which will detect wind speed and direction and we

also need to take into account that the locking mechanism worth six thousand dollarsb. This

brings us right up to our budget of thirty eight thousand dollars, however our system of the use of

a tail vane and locking system will be much more energy efficient than a traditional motor

because our system does not require nearly as much energy.

Application:

Our team is attempting to find the most efficient way to rotate a wind turbine to make it energy

efficient. Our design incorporates a frictionless surface, locking mechanism, a tail vane and a

wind direction/speed sensor. Our design incorporates resources that are already incorporated into

the wind turbine, wind. By using the wind the turbine needs to generate electricity we are

creating a self-sustaining reliable platform on which to make an efficient wind turbine. With the

use of our design I believe that our design that does not use traditional motors to rotate the

turbine is both energy efficient and will allow for the maximum energy output.

77

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