A Two-Bladed HAWT Final Design Report

Prepared By: Team Good Wind Hunting

Shadae Boakye

Andrew Fountain

Marshall Gordon

Joe Moss

Prepared for: Ed Oor

Chief Executive Officer of Oor, Dean, and Airy

Roger De Roo

ENGR 100 Engineering Professor

Mary Jane Northrop

ENGR 100 Tech Comm Professor

Date Submitted: April 21, 2015

1 

 

Executive Summary

Presently, people living in rural Guatemala are using kerosene lamps to heat and light their homes.

Kerosene is bad for the environment and is proven to have hazardous health effects [1]. Because

Guatemala has many off-grid communities without electricity they have no light to light their homes

at night. After sunset, children are not able to study or do homework because of the lack of light. This

hinders their education and a lack of education increases the number of people living at or below the

poverty line [2]. Guatemala does, however, have high and consistent wind speeds [3]. Due to this,

wind energy is a logical option for generating power.

Our product, the Two-Bladed HAWT (Figure 1), makes studying and performing household activities

after dark possible. Oor, Dean, and Airy has tasked us with developing a wind turbine prototype

capable of generating 3W of power in 5 m/s winds. The Good Wind Hunting engineers built our

prototype turbine from scratch using materials that were cost-effective and durable. First we came up

with several different designs and then decided on some objectives. These included cost, easiness to

assemble, durability, and safety. After filling out the decision matrix, we decided that the Two-Bladed

HAWT best met our objectives. We then started constructing by using materials that were sturdy and

cheap so as not to compromise two of our objectives-durability and cost. After making a few

mechanical and electrical modifications to our prototype, we should be ready to mass produce the

turbine and deploy it to Guatemala.

The innovative aspect of our design is the fact that it only has two blades as opposed to the popular

three-bladed HAWT. See Figure 2 for a view of the blade using one piece. Using two blades, especially

a blade that can be constructed from one piece of PVC pipe reduces the number of parts used and

simplifies the design. The Two-Bladed Hawt is also lighter and creates greater blade stability[4]. In

addition, the power output difference between small-scale two-bladed and three-bladed HAWTS is

negligible.

The Two-Bladed HAWT generates enough power to light the LED lights in the box and read the

message.The prototype generated an average of 0.0167 Watts in an average of 2.84 meters per

second wind speed with less than .2% efficiency. This report explains the design of the Two-Bladed

HAWT in greater detail, details the budget and safety analyses and illustrates parts of the prototype

design. Finally, this report also discusses some future improvements that can be made to the turbine

to increase efficiency and power output before deployment to Guatemala.

 

 

Table of Contents

Introduction.................................................................................................................... 1

Design Criteria............................................................................................................... 1

Produce Consistent Power…...………………………………………………………. 2

Low Cost……………………………………………………………….……………….. 2

Durable…………………………………………………………………….……………. 2

Easy to Assemble……………………………………………………………..……….. 2

Safe…..…………………………………………………………………………………. 2

Prototype Design........................................................................................................... 2

Support Post……...…...………….…………………………………………....……… 3

Blades……………………………………………………………………………….….. 3

Shaft……………………………………………..……………………………………… 4

Transmission…….…………………...………………………………………………... 5

Yaw System……………………………………………………………...…………….. 5

Electrical System………………………………………………………………..…….. 6

Performance Analysis................................................................................................... 6

Safety and Technical Requirements……...…...…………………………….………. 6

Power Output and Efficiency…………………..………………………………….….. 7

Tip Speed Ratio……..…………………………………………………………….…… 7

Electrical Analysis……………………………………………………………………… 7

Budget............................................................................................................................ 9

Initial Budget……...…...………….…………………………………………....………. 9

Final Budget………………………………………………………………..……….….. 9

Creativity and Appropriateness................................................................................. 10

Innovations in Design……………………………..…….……………………...……. 10

Appropriateness………………….……………………………………………….….. 10

Economy of Design..……………………………….………………………………… 11

Technical Recommendations..................................................................................... 11

Design Deficiencies..……...…...………………….…….……………………...…… 11

Possible Improvements…………………..………………………………………….. 11

Production-Level Turbines………….…….…………….…………………………… 11

 

 

The Carbon Footprint…………...………...……………….………………………… 12

Conclusion................................................................................................................... 12

Works Cited.................................................................................................................. 13

List of Appendices........................................................................................................13

Appendix A……..……………..……………………...…………….………...………. 14

Appendix B…….…………………………………….…………………………….….. 15

Introduction

 

 

In 2010 over 18 percent of people in Guatemala were without power. With a population of 15.47

million this means that 2.78 million people were without power [5]. This issue is attributed to the lack

of an electrical grid in the rural areas of Guatemala; and lack of power is not just a problem for

Guatemala. Other rural South America countries, such as Nicaragua and Honduras, have an even

higher percentage of their population without power [5]. Since these rural populations do not have

access to an electrical grid, there is an opportunity to provide them with electricity and benefit

economically.

In Guatemala the average daily wind speed varies from 3.1 m/s to 8.9 m/s depending on the season

[3]. These relatively high and consistent wind speeds make wind energy a sensible solution the

problem of a lack of an electrical grid in rural South America. This, along with Oor, Dean, and Airy’s

excess of stepper motors point to the production of an off-grid wind turbine as the best solution.

Wind turbines would not only provide electricity to rural off-grid communities, but would also allow

Oor, Dean, and Airy to make a profit through the sale of these wind turbines.

The people living in rural Guatemala and similar places resort to kerosene lamps for light at night. This

is not a reliable source of light and does not provide enough light for people to be productive at night.

This makes the people of rural off-grid areas the main target audience for the off-grid wind turbines.

Our engineering team, Good Wind Hunting, was tasked by Ed Oor, CEO of Oor, Dean, and Airy, to

design and build a prototype wind turbine for implementation in rural communities. To address this,

our team designed and built a two-bladed horizontal axis wind turbine (HAWT). This report includes a

description of the prototype design, an analysis of the prototype’s performance, the budget, and

technical recommendations for future designs.

Design Criteria

There were multiple requirements set by Ed Oor that the design had to meet. These requirements

were that the turbine must:

● Generate at least 3W in 5 m/s winds

● Have the highest non-rotating part be no taller than 2.30m

● Have a collection areas of less than 0.72 m2 In addition to these, there were safety requirements. These were that the turbine:

● Withstand 150 N sideways force

● Have no loose parts

● Have no sharp weight bearing edges

● Not crush a paper towel roll when rotating.

With these in mind, our team decided on our own design criteria to best achieve these goals. These

were that the turbine be able produce consistent power, low cost, durable, easy to assemble, and

safe. Each criterion is described in further detail below.

Produce Consistent Power

 

 

Since the main goal of the wind turbine to provide enough power to provide people with light this was

the most important design criteria. Wind speeds in Guatemala are above 3.1 m/s on average [3],

which means that there is a consistent wind source. Given this consistent wind, our wind turbine

design should be able to produce power consistently.

Low Cost The goal of any company is to maximize profits. One way to do this is to keep costs to a minimum.

Oor, Dean, and Airy are looking to profit through the sale of these wind turbines. So, keeping the cost

low would maximize these profits. The low cost would also benefit the consumer in rural communities

because the wind turbines could be sold for less initially, and parts replaced for less later on. Kerosene

is estimated to cost about 1.2-1.6$ in rural Africa. Assuming the cost of Kerosene is similar in other

rural areas, a $100 wind turbine would pay back the cost after only three years of use powering a

single small $40 lamp [6]. Due to these considerations, we set our goal budget at $100.

Durable Rural communities are most likely unable to have replacement turbine parts. As a result, durability

was one of our main design criteria. A durable wind turbine is less likely to need repair, which means

there will not be any extra costs after the initial investment.

Easy to Assemble A turbine that is easy to assemble helps Oor, Dean, and Airy and the rural consumers. It helps Oor,

Dean, and Airy because it minimizes the time needed to install and teach the locals about repairing

the turbine. The consumers are aided by the easy to assemble design because a simple design means

that it is also easy to repair.

Safe Safety was important to consider because the wind turbine would not be worth implementing if it was

unsafe. The locals would likely not accept an unsafe turbine and the harm caused by an unsafe turbine

would outweigh its benefits. For this reason, safety was kept in mind throughout design and

implementation. A safe wind turbine would provide a significant benefit to the users over kerosene,

which has significant health risks, and can also cause fire and explosions if mishandled [7].

Prototype Design

We took the design criteria into consideration and decided a two-bladed HAWT would best meet

these criteria. The design consisted of four major components: the support post, blades, shaft,

transmission, yaw system, and electrical system. The first four components are labeled below in

Figure 1, a final picture of our prototype. They, along with the electrical system, will be discussed in

more detail below.

 

 

Figure 1: Final prototype design with component labels

Support Post Durability and ease of assembly were two of our design criteria. Based on these two criteria we chose

to use a two meter long 3”x3” timber post and latch it to a fixed railing with hose ties as our support

mechanism. This was chosen because it is was under the 2.30 m maximum height requirement and it

is very simple and easy to implement because it eliminates the need for a base. Also, the wind turbine

is likely to last longer if it is attached to something permanent, such as a railing. Even in cases where a

permanent structure is not available, digging a hole and pouring in concrete would securely support

the post and turbine. This was by far the heaviest component of the wind turbine weighing in at 5.0 kg

while all other components it supported were 2.1 kg. This high weight is ideal because it keeps the

center of gravity low and resists tipping better.

Blades The blades were made out of PVC pipe measuring 4” in diameter, the largest available at a local

hardware store. One of the reasons we chose the two-bladed HAWT design was the possibility of

making the two blades using one piece of PVC, increasing the durability of the wind turbine compared

to two blades made of separate pieces and connected by a hub. The initial blades had a length of .47

m, maximum chord length of 6 cm, had no hub, and were made of one solid piece of PVC. This is

pictured below in Figure 2.

Figure 2: Initial blades made from one piece with 6 cm chord length and no hub

This blade design is what we initially envisioned working, however, in lab testing using three box fans

showed that this blade design produced no rotation. We concluded our angle of attack must not be

 

 

steep enough. However, the PVC pipe available in hardware stores did not allow us to increase the

angle of attack any more. So, we decided to cut two separate blades from the PVC pipe and build a

hub for them. This modification led to an increased chord length of 10 cm and a steeper angle of

attack, which in lab testing showed worked. The modified blades are pictured below in Figure 3.

Figure 2: Final blades made from two pieces with 10 cm chord length and hub

Ideally, in production the two blades with steeper angles of attack and larger chord lengths could be

made out of one solid piece using injection molding or much larger PVC. However, due to the

limitations of this project these were not options.

Shaft Steel was chosen as the material for the shaft because of its durability. Originally a solid 0.5” steel rod

was purchased and cut to a length of 0.4 m and implemented for testing. The shaft was held down by

two 0.5” pillow block bearings. Two bearing were used instead of the one because of the increased

stability and longevity they provide compared to just one bearing. During in lab testing the turbine

failed to rotate with this shaft in use. As a result, a hollow 0.5” steel rod was substituted in. This rod

was cut to 0.4 m and weighed 75 g, which was considerably less than the original rods 245 g weight.

With this new shaft the turbine was able to rotate during in lab testing. The final shaft and bearings

are depicted below in Figure 4.

Figure 4: Final hollow steel shaft with two pillow block bearings

 

 

Transmission For the transmission we decided on a 9:4 gear ratio. because our design provides a large amount of

torque. The blades and the drive gear were attached to the shaft by 0.5” hubs. The drive gear had 36

teeth and the driven gear had 16 teeth, which is a 9:4 gear ratio. The hubs and gears were kept in

place with set screws. A picture of the two gears and their connection is below in FIgure 5.

Figure 5: Transmission with 36 tooth drive gear and 16 tooth driven gear

This aspect of our design worked well and we believe would work well in the final product.

Yaw System In order to ensure the maximum power is being drawn from the wind the turbine blades must be

facing perpendicular to the direction of the winds velocity. To address this problem we implemented a

simple yaw system. There are two parts to the system: a lazy susan and a fin. The lazy susan rests on

top of the support post and below the top rotating platform. The lazy susan is shown below in Figure

6. The lazy susan must support 2.1 kg, and even though we tried to center the mass over the top of

the lazy susan there was still some instability. This could be addressed by using higher quality wood

for the top platform and making the fin lighter.

Figure 6: Lazy Susan mounted on post

 

 

The fin was made out of plywood and mounted using L-brackets and two nuts and bolts. Although this

secured the fin, it added a significant amount of weight far away from the lazy susan, which hindered

the lazy susan’s effectiveness. In production the fin’s weight should be minimized, but adhere to the

same design as our prototype. The fin is depicted in Figure 7 below.

Figure 7: Fin attached with L-brackets and bolts

Electrical System Our group chose to utilize one of the spare stepper motors provided by ODA to generate the

electricity in our prototype. The stepper motor was wired in two phases and attached to an external

resistance. Initially, 5 Ohms of resistance was used, however, this caused the turbine to have trouble

spinning and produced extremely low voltages, so the resistance was increased to 20 Ohms.

Performance Analysis

This section outlines the prototype’s performance on our safety, technical, and power requirements.

This section also details the reasons behind any problems or failures to meet objectives.

Safety and Technical Requirements After a small modification that required the blades to be cut down in length, our prototype passed all

safety and design specifications. Our prototype met all of the required tests:

● Technical requirements: that the turbine be no taller than 2.3 meters and have a wind

collection area of no more than 0.72 meters squared. Our prototype was within these limits.

● Blowdown test: can withstand a sideways force of 135 N applied at the top without shaking or

falling down. Our prototype was lashed with metal hose ties to the railing to ensure it would

pass.

● High winds test: has no loose parts that could come off. Everything on the prototype was well

secured.

● Passerby test: the turbine could not damage a paper towel roll stuck into unguarded moving

parts. Our prototype caused no such damage.

● Rooftop integrity test: has no sharp, weight-bearing parts. Our prototype was designed

without a free-standing base, so only the wooden timber touched the rooftop.

 

 

Power Output and Efficiency

Unfortunately, our wind turbine’s end-to-end efficiency was well below our target goal, meaning that

our design was unable to meet our objective of consistent power. The goal of generating 3 Watts in

five meter per second winds means that the prototype should have had a 5.6% end-to-end efficiency.

This was calculated by dividing the 3 Watts by the theoretical power output of the wind, see appendix

B for the full formula. The wind turbine only generated an average of 0.0167Watts in an average of

2.84 meters per second wind speed, making the end-to-end efficiency only 0.164%. This result

includes all data values at which there was a registered frequency on the voltmeter, see appendix a

for more details. This power was obtained by using the formula V2/R with an average voltage of 0.57

Volts and a resistance of 20 Ohms. Additionally, the efficiency of the wind turbine was extremely

variable and unpredictable. Even with the time delayed adjust for, the wind turbine was unable to

produce consistent power outputs and instead would produce a multitude of different outputs at the

same wind speed, as seen in figure 8.

Figure 8: This graph shows wind speed versus power after adjusting for the time delay.

Tip Speed Ratio The tip speed ratio we obtained shows that our frequency is close to our goal where it should be. We

obtained a number of 6.7 which is within the ideal range of 6 to 8 that most sources indicate is ideal

[8]. The tip speed ratio was obtained by determining the average frequency, dividing this number by

two to account for the stepper motor being wired in two phases, and then multiplying by the inverse

of the gear ratio. This tip speed ratio indicates that the low voltage may come from problems with the

electrical system.

Electrical Analysis A likely cause for the low power output may have been the electrical circuitry. Earlier tests indicate

that the stepper motor should have been able to produce around five to ten watts at rotation speeds

above 100 hertz. However, even when this frequency was reached the actual voltage achieved was

 

 

never even close to reaching the expected value as shown in figure 9. This discrepancy indicates a

problem with either the stepper motor or the voltmeter, or a huge inefficiency in the electrical wiring.

Figure 9: This graph shows frequency vs. voltage and reveals odd discrepancies in the data.

From the average wind speed, we calculate that a 5.6% end to end efficiency should be possible with

an average voltage of 3.3 volts when using a 20 Ohms resistor. The data from lab 3 indicates that such

a voltage should be obtained at an electrical frequency of 52 Hertz with no resistance, see figure 10.

Even with the electrical resistance at 20 Ohms, the average electrical frequency of 111 Hertz should

have been able to produce more power than the turbine did. A turbine rotation speed of 12 Hertz or

110 rotations per minute should be able to generate close to the desired efficiency of 5.6%. Our

prototype was able to exceed this rotation rate and obtain a rotation rate of 14 Hertz, indicating that

a problem with the stepper motor may be the cause of the low power output.

Figure 10: This graph shows frequency vs voltage for an unloaded stepper motor.

 

 

Budget

This section details the constraints our team set on our own budget and how these constraints were

met. The section includes both an initial budget created when first designing our prototype and the

final budget that we ended up utilizing to construct the prototype.

Initial Budget One of the goals for this project was to have a construction cost of less than $100, in order to ensure

that our wind turbine was available to as many people as possible, particularly those in areas without

an established electrical grid. The initial budget estimated the cost at $62.81 (table 1), well within the

goal set earlier. One of the reasons for this low cost was the simplicity of the design and the relatively

few parts used, as well as the use of cheap yet durable parts, such as PVC pipe and wood. The full

initial budget can be seen below.

Table 1: Initial Budget 

Item  Cost/ Item $ 

Quantity  Total Cost $ 

4in Lazy Susan    4.48  1    4.48 

4in steel hose ties    1.39  3    4.17 

2.5ft Steel rod shaft 5/8ths inch     5.77  1    5.77 

1 meter long by 0.12 meter diameter PVC pipe  16.67  1  16.67 

3”x3” Large timber rod, at least 1.5 meter long    3.97  1    3.97 

Gear set  15.00  1  15.00 

1 inch phillips head screws    4.37  1    4.37 

Total (including 6% tax)      62.81 

Finalized Budget Several changes were made to the budget as design and construction progressed. Most notably, we

were able to utilize spare parts found in the lab, thus avoiding an additional cost. These included the

shaft to drive the stepper motor (a ½ inch hollow rod), bearings, wiring, and resistors. Additionally,

the expenses on the PVC pipe were reduced by selling unused portions of pipe to other groups. The

gears used cost more than estimated, partly due to the fact that the gears needed to fit the stepper

motor and shaft were very small and oddly sized, requiring them to be special ordered to ensure a

correct fit. The final budget can be seen in the chart below, with changes in cost highlighted.

 

 

Table 2: Final Budget 

Item Cost/ Item ($)  Quantity  Total Cost ($) 

4in Lazy Susan  4.48  1  4.48 

4in steel hose ties  1.39  3  4.17 

2.5ft Steel rod shaft 1/2 inch bore  5.77  1  5.77 

0.12 meter diameter PVC pipe  6.67  1  6.67 

3”x3” Large timber rod (1.5m long)  3.97  1  3.97 

Gear set and hubs  22.45  1  22.45 

½ inch Bearings*  5.00  2  10.00 

Plywood*  10.00  1  10.00 

Wiring and Resistors*  1.00  1  1.00 

Total Expenditure      47.51 

Total* (including 6% tax)      68.71 

The items marked with a * are those that were found in the lab and had no cost for the prototype.

Total expenditure is what Good Wind Hunting spent to produce the prototype, and the total below

that is what the wind turbine would cost if all parts had to be purchased.

Creativity and Appropriateness

Innovations in Design The design of the 2-bladed HAWT was innovative in several ways.

First and most obvious, the design used only 2 blades instead of the typical 3 blades found on a

HAWT. This was done in order to reduce parts used; the 2 blades can be constructed from one piece

of PVC pipe, which then avoids the use of a central hub to attach the blades to, further simplifying the

design.

Additionally, the design implemented a yaw mechanism by means of a fin attached to the rear of the

turbine and a lazy susan between the turbine and the support post, allowing the turbine to move into

the wind no matter what direction it is blowing. The design also used a gear system in order to

generate the highest torque possible on the stepper motor, which in turn would produce the most

power possible.

Appropriateness This design is quite appropriate for its intended users (those in areas without an established electrical

grid). It is a very simple design and has very few parts, thus reducing the need for maintenance and

training on its use. The 2-bladed HAWT is easy to assemble with only hand tools, and can be put

 

 

together in approximately a half hour. It is very safe, having passed all safety tests before testing and

deployment. The design is also easy to assemble from parts that would be available in remote areas,

as any malleable plastic can be used (not necessarily PVC pipe), as long as it can be formed into the

blade shape required. Wood and metal (for the shaft) is most likely readily available in these areas;

therefore, the only parts that would be difficult to find would be the bearings and the gears. This

makes the design easy to repair in the event that a part should break or get lost.

Economy of Design

As mentioned above, the 2-bladed HAWT is quite simple in its design, thus allowing for easy assembly

and repair. It would require little to no training to operate and maintain this device, thus ensuring its

usefulness and reliability to those who need it.

Technical Recommendations

Design Deficiencies

The design of a 2-bladed HAWT has some deficiencies that are worthy of discussion. Most notably, the

prototype designed by Good Wind Hunting suffered from a rather high starting torque, as well as

vibration of the device when it was spinning. This could cause damage over time due to the loosening

of screws and bolts, as well as wear on the shaft and bearings. The yaw mechanism was also not as

responsive to changes in wind direction as it could have been. Additionally, the design requires a

support post to lash it on to, it cannot stand by itself.

Possible Improvements

These deficiencies could be improved in several ways. The issue of the high starting torque could be

resolved by using an electrical system with more resistance, which would decrease the starting

torque. The issue of vibration of the device could be resolved by having more uniform blades, instead

of the 2 distinctly different blades that were used. These 2 blades were made thinner by sanding

them, and each was sanded individually, resulting in the blades having slightly different shapes and

causing an uneven rotation of the shaft. The yaw mechanism could be improved by purchasing a

better lazy susan with less friction, and balancing the weight more evenly on the support post instead

of having most of the weight of the device in front of the post. Also, a stronger, freestanding base

could be constructed to eliminate the issue of having to have a post to lash the device on to. The most

important improvement would be to improve the wiring and ensure that the stepper motor is

performing reliably in order to see more consistent results.

Production-Level Turbines

At this point, the design of a 2-bladed HAWT is too electrically inefficient to warrant scaling up the

design to a production-level product. It is not producing the voltages required by ODA and by Good

Wind Hunting’s project objectives. Further testing in a wider variety of wind speeds and detailed

analysis of the electrical system are required before scaling up the design can be considered. This is to

ensure that the best, most efficient product possible can be produced.

 

 

Possible modifications include changing resistance and using a dynamo instead of a stepper motor.

The electrical frequency of the prototype shows that a change in the scale of the electrical equipment

is more appropriate than any physical scaling up of the size of the prototype design.

The Carbon Footprint While the design has very few parts, and thus a very small carbon footprint, further changes can be

made to reduce the carbon footprint even more. Among these changes are the use of more

eco-friendly materials instead of the plastic PVC pipe, as well as decreasing the size of the platform

the turbine is mounted on in order to reduce the amount of wood used in the design. Overall, the

carbon footprint of the device is almost as small as possible as of now, so not much would have to be

done to reduce to as small as possible.

Conclusion

In conclusion, the Two-Bladed HAWT completed the task of generating enough power to light up the

LED lights and read the message in the box. The message read “I was raised to be charming, not

sincere”. In addition to reading the message we were also able to complete most of our objectives.

After using resources in the lab and making a few modifications, we were able to complete the project

under budget and pass the safety test. Even though we did not generate the required number of

Watts, there are certain improvements and future steps that can be implemented before deployment

of the turbine to Guatemala. The most important improvement would be in the electrical system.

Further testing of the resistance in the system, the electrical circuitry, and the stepper motor itself

should allow us to find and correct the source of the low power output in our prototype.

Other improvements include getting the material required to use a single piece of PVC for the blade,

getting bearings with less friction, and increasing the sturdiness of the turbine above the Lazy Susan.

After some further testing on the electrical system and executing these recommendations, we should

be ready to deploy the turbine to Guatemala and other rural areas. The Guatemalan people will no

longer need to be exposed to the harmful effects of kerosene and can continue their activities past

sunset. This will lead to children getting a better education and the improved lives of future

generations.

Works Cited

 

 

[1] Jacob L. Heller, MD. Kerosene poisoning. (2014). [Online]. Available:

http://www.nlm.nih.gov/medlineplus/ency/article/002807.htm

[2] Educational Testing Service. Poverty and Education:Finding the Way Forward. (2013). [Online].

Available: https://www.ets.org/s/research/pdf/poverty_and_education_report.pdf

[3] Cedar Lake Ventures. Average Weather for Guatemala City. (n.d.). [Online]. Available:

https://weatherspark.com/averages/32497/Guatemala-City

[4] Gaia-Wind Limited. Why small wind turbines with two blades are better than three. (2013).

[Online]. Available:

http://www.gaia-wind.com/133-11kw-turbine/why-two-blades-are-better-than-three/

[5] The World Bank. Access to electricity (% of population). (2015). [Online]. Available:

http://data.worldbank.org/indicator/EG.ELC.ACCS.ZS?order=wbapi_data_value_2010

wbapi_data_value wbapi_data_value-first&sort=desc

[6] Tracy, Jennifer and Arne Jacobsen. The True Cost of Kerosene in Rural Africa. (2012). Available:

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0

CB8QFjAA&url=http%3A%2F%2Fglobal-off-grid-lighting-association.org%2Fwp-content%2Fupload

s%2F2013%2F09%2Fkerosene_pricing_Lighting_Africa_Report.pdf&ei=ma01VcG3MdCKaNaigMgI

&usg=AFQjCNHM0EygIx9wYp3MKQrP526HfAYwIg&sig2=VBTSM617om44bkrhlsMypA&bvm=bv.9

1071109,d.d2s

[7] Alison Gauthier. Kerosene: A Review of Household uses and their hazards in low- and middle-

income countries. (2013). [Online]. Available:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3664014/

[8] Ragheb. Optimal Tip Speed Ratio. (2014). Available:

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CCYQFjAB&url=htt

p%3A%2F%2Fmragheb.com%2FNPRE%2520475%2520Wind%2520Power%2520Systems%2FOpti

mal%2520Rotor%2520Tip%2520Speed%2520Ratio.pdf&ei=rK41VbShOZbdaqLVgYgO&usg=AFQjC

NGKCt1Ewmb-62ZTpwwtngEDu_Z1vQ&sig2=FKWaRq2k1PQqkrSXjWt6LQ&bvm=bv.91071109,d.d

2s

List of Appendices Appendix A: Anemometer and voltmeter data

Appendix B: Equations

Appendix A: Anemometer and voltmeter data

 

 

Please refer to the attached excel sheet marked “Appendix A.” This sheet includes wind speed (m/s),

voltage (V), and frequency (Hz) in the last three columns respectively. The data also includes a delay

between the wind speed and the electrical readings, so all graphs and calculations reflect this fact.

 

 

Appendix B: Equations This appendix shows some of the more complex equations used to obtain data in the performance

analysis section.

Theoretical Wind Power = ½ * density of air* area* wind speed ^3

Tip Speed Ratio = turbine blade speed / wind speed

Turbine blade speed = Motor frequency / number of phases * inverse of the gear ratio * radius