Paper ID #28525

Power Generation through Small Scale Wind Turbine

Prof. Bala Maheswaran, Northeastern University

Bala Maheswaran received his M.S. and Ph.D. in experimental solid state Physics, and MSEE in Electri-cal Engineering from Northeastern University. He is currently a senior faculty at Northeastern University.He has contributed and authored about seventy publications consisting of original research and educationrelated papers, and conference proceedings. He has over twenty-five years of experience in teaching atNortheastern University. He is the Chair of the Engineering Physics Division, ASEE, Chair-elect andexecutive board member, ASEE NE Section; the co-chair of TASME Conference (Technological Ad-vances in Science, Medicine and Engineering, Toronto, Canada), Academic Member and the Unit Head,Electrical Engineering, ATINER (Athens Institute for Education and Research, Athens, Greece).

Ms. Alya Abd Aziz, Northeastern University

2nd year Bioengineering student at Northeastern University.

Mr. Evan Alexander,Ms. Laura Brigandi, Northeastern University

Laura Brigandi is currently pursing her B.S. in bioengineering with a minor in mathematics at Northeast-ern University. She plans to concentrate in biomedical devices. In July, she will begin her first co-opworking at Cam Med Inc., as a biomedical engineer, helping with their development of medicine dispens-ing pumps.

Cole Branagan,

College of Engineering Northeastern University

c©American Society for Engineering Education, 2020

Power Generation through Small Scale Wind Turbine

Alya Abd Aziz, Evan Alexander, Cole Branagan, Laura Brigandi, and Bala Maheswaran

College of Engineering

Northeastern University

Abstract

As the world and technological advancements move forward, people continue to look to new forms

of energy.1-2 Fossil fuels are finite and will eventually become depleted, so renewable energy, such

as wind energy, is becoming more common. Large scale wind turbines are an efficient way to

harness energy for consumption by the general population. For the individual, finding a way to

scale down the common wind turbine to a smaller, portable, design would be helpful to many

people. This work explores the usefulness of a portable wind turbine that could be attached to a

bike, as bikes are used often and everywhere. Furthermore, bikes can reach enough velocities to

produce wind flow, which is beneficial for any wind-powered device. Being able to successfully,

and efficiently capture wind power in such a small turbine efficiently could prove incredibly useful

to the world's power. This not only provides scientists and researchers with more valuable

information about alternative energy, but it is also capable of educating3-4 the everyday person

about the basics of engineering as well as the importance of renewable resources. In addition, this

work educates students on various skills such as research, persistence, design, construction, and

technical writing.

Introduction

An innovative teaching approach was developed for the newly designed eight credit hour

cornerstone course for the first-year engineering students. This method was very effective and

well-suited to educate students. Rather than just studying for exams to gain good grades, this skill-

and knowledge-integrated approaches help highly motivated students to interact with other

students and faculties from various institutions and take further strides towards real world

situations.

This paper shares a sample project illustrating a new teaching approach via innovation. One of the

objectives of the Experiential Engineering Education and this paper is to reform engineering

education by moving away from the boundaries of traditional classroom-based approaches to

project- concept- and team-based, and skill- and knowledge-integrated approaches using real

world situations. This new teaching approach can improve the effectiveness of engineering

education.

Fossil fuels such as coal, petroleum, and natural gas have been the major sources of energy in the

world since the late eighteen century.5 However, with the depletion of nonrenewable resources,

renewable energy sources have been more sought after because they are cleaner forms of energy

and are reusable. The most common forms of renewable energy include solar, wind, hydroelectric,

and biomass. The use of renewable energy has increased significantly and is continuing to grow

due to its high demand and productivity. This project focuses on the use of wind power and how

it can further be innovated for more widespread applications.

Wind power is quickly being developed in regions all over the world. In 2018, the Global Wind

Energy Council reported that 46.8GW worth of wind power was installed onshore, 16% of the

installations being made in the US.6 Wind power was initially utilized by ships with sails, and then

further developed into windmills used by the Persians as early as 500-900 A.D. The first

electricity-producing windmill was created in 1888 by Charles F. Brush in the U.S. Later, during

the 1973 oil crisis, the U.S. looked further into renewable sources of energy which led to the

booming of the wind power industry. Currently, the cost of operating a wind farm is cheaper than

operating a coal plant.7 There are three main types of wind power: utility-scale wind turbines,

commercially distributed wind turbines, and offshore wind turbines. Wind turbines are generally

designed either around a vertical axis or horizontal axis, depending on which works best in its

specific environment.

Most wind turbines today, for example, utility turbines and offshore turbines, are far from where

civilization, and generate energy for the general population. For the general population to take

initiative, a small-scale wind turbine was created to be attached to a bicycle handle. The user can

generate energy while riding their bike by harnessing the wind flow generated by the forward

motion. The generated power can be utilized by adding a USB port to the circuit to charge a phone,

portable charger, a bike light, and more. The idea behind this approach is that the user does not

have to rely on wind, but instead create their own airflow by riding the bicycle. The product’s aim

was to make a product that was aesthetically pleasing, environmentally friendly, safe for the rider,

small and portable, energy efficient, and durable. However, for the initial prototype constraints

such as time and budget came into play.

Method

After reaching the decision to make a wind turbine, initial research was started, along with a

brainstorming process. First, the common design of a wind turbine was researched to understand

all the general parts required. The main components of horizontal wind turbines include the

blades/rotor, a drive train (usually including a gearbox and generator), and a tower.8 To start the

project, rough sketches and SolidWorks models to get an idea of some initial designs were created.

Goals of safety, efficiency, and aesthetics were kept in mind throughout the design process. Some

initial designs involved biomimicry—a design process inspired by elements found in nature—to

model fan blades after the fins of whales. However, due constraints—time and cost—it became

too complicated to implement concepts of biomimicry [Appendix 5].

Theories and Design Concerns

A horizontal axis turbine was chosen due to its stability and durability. The radius for the blades

were decided to be wide enough to produce enough torque to keep the turbine spinning. Lowering

the radius decreases the amount of energy produced. It was determined that the blades should be

5 centimeters to be wide enough to produce enough torque to keep the turbine spinning. This

design allowed for the turbine to be small enough to fit on a bike without disrupting the rider.

The number of blades used, and the blade shape was decided based on maximizing efficiency. In

a perfect world, maximizing efficiency means that the wind turbine will harvest 100 percent of

possible energy. However, through research, it was found that according to Betz limit, the

maximum possible energy a wind turbine could harvest is about 59 percent.9 At high speeds drag

becomes another important consideration. Conventional airfoils were consulted to determine the

optimal cross-sectional shape to work with for this product. The airfoil provides the most favorable

lift to drag ratio. Stability at high radial speed was of the utmost importance, making a teardrop-

shaped airfoil for the blades helped with both those measures.10 A three-blade fan was decided to

be the most efficient design as increasing the number of blades reduces efficiency, and two blades

would not provide the imbalance to spin the turbine.11 Through research a 4:1 gear ratio was

decided for best efficiency. Design sketches were assembled from decided turbine elements.

Plans for the fan and motor apparatus were made to maximized electricity generation. The motor

from a SparkFun kit was utilized for the first prototype to generate electricity. The motor house

was developed to house the gears and hold the motor in place. A shaft with a notch was developed

to connect the blades to the gears inside the motor house. The shaft fit directly into the center hub

of the blades, and at the other end, the gears fit into a notch. A central circular frame was developed

to hold the shaft in place. It was equipped with a ball bearing in the middle to lower friction caused

by the rotation of the shaft. Another function of the central circular frame was to hold the motor

house in place. A funnel that would attach around the blades to funnel the air was developed,

however, due to 3D printing time constraints, the part was eliminated from the final design.

A final design concern for this project was the actual attachment of the turbine to a bike. The

solution to this problem, given the budget constraint, was to fit the design to be held by a bike

mount for a cell phone. The turbine design was adapted to have an attached cylinder and

rectangular prism to house the circuitry and allow for easy attachment to the bike mount. The

rectangular prism base was designed as an open concept in order to allow modification to the

circuitry during the testing process.

Initial Design

SolidWorks was utilized to develop each piece individually and assembled to make the turbine

[Figure 1-2]. With the pieces fit in SolidWorks, they were 3D printed and assembled.

As initially designed, the fan head was fit onto the end of a shaft [Figure 2A, H]. The shaft ran

through a bearing and the larger gear [Figure 2G, H, I]. Another bearing was placed to limit the

friction that the shaft experiences while rotating [Figure 2D]. The large gear contacted the smaller

one, which was connected to the motor [Figure 2E, I]. Both the gears were contained within a

housing of two pieces. The first is a wall high enough to surround the gears to prevent gear

Figure 1: Complete Assembly of First Final

Design

Figure 2: Exploded View of Assembly

movement disruption. The second is a plate to align the motor to the gears and fix its position

[Figure 2C, F]. The fan was made by creating a cylindrical center with a cone on top and then

extruding a sketch of the teardrop-shaped airfoil from the center. The airfoil has an angle of attack

of 45°, a design detail determined from research. An angle of attack of 45° makes the fan suitable

to operate in lower wind speeds because it will allow more surface area for the blade to interact

with the wind. However, because the airfoil design was too short and small to make use of this

concept, the turbine will hypothetically not work at low speeds. A better design would have the

blades designed at a higher angle of attack to increase the threshold speed to start spinning the

turbine. All the parts in Figure 2 were 3D printed, except for the bearings and motor, which were

both purchased.

The assembly picture in Figure 2 was altered due to low voltage output of the SparkFun motor. A

redesign of the motor house was made to account for a new motor of a larger radius with a higher

voltage output. Due to time constraints and support issues with the 3D printer, the fan blades

needed to be printed separately and attached to a centerpiece after printing. Additional photos of

the design can be found in Appendix 3.

Design Issues

While assembling the components, issues were faced. For example, the parts were printed to strict

dimensions. This means that components such as the bearings and the motor fit very tightly into

their proper spaces. Furthermore, the small gear was also touching the housing, causing friction

and resistance—too much resistance for the fan to overcome. The pieces were sanded down to

create space between components. Another unexpected outcome was that the new motor created

too much resistance for the fan to spin. The motor house was redesigned to incorporate a better

motor [Figure 3]. Resistance was created by faulty ball bearings, friction between gears, and the

generator further slowing the rotation of the fan. Due to time constraints, additional 3D parts could

not be printed to correct that issue. The final design was created by utilizing already printed parts

to fix issues slowing the rotation of the fan. Additional photos of the first design can be found in

Appendix 6.

Figure 3: First Design Pieced Together

Figure 4: SolidWorks Model of Current

Design

Final Design

With about a week until the deadline, the final design allowed the turbine to overcome resistance

from the motor-generator. For testing and least resistance, the 3D printed, and assembled fan was

attached directly to the generator to prevent energy loss from the gears [Figure 4]. To support the

turbine generator, the unused 3D parts were utilized, as opposed to new 3D printed parts, due to

cost and time constraints. For the turbine and base, the designs were sturdy and worked well, so

they were kept the same. Slits were cut into cardboard and folded it around the two motor houses

to enclose the generator. To make the product more durable and aesthetically pleasing, red duct

tape was added around the cardboard. Future design modification would have included a 3D

printed casing for the motor housing. Figure 5 shows the complete design.

Additional testing was performed with a vertical turbine ordered from Amazon, not requiring

major modification to the final design [Figure 6]. The vertical turbine came with a higher voltage,

lower resistance motor that was used in the final design.

Data was collected from the vertical turbine tests using the same methods and circuitry. The design

allowed the vertical and horizontal turbines to easily attach and detach, allowing ease of data

collection. The vertical and horizontal turbine voltage generated results were compared. To attach

the vertical turbine, the phone mount was rotated around the bike handle, so that the turbine spun

around the vertical axis.

Testing with Bike

To test the fan, the SparkFun RedBoard and breadboard were connected to a laptop and the turbine

motor. Difficulties arose during data collection, due to the connections of the SparkFun

components and the laptop for data collection. In order to collect data of the turbine spinning

during a bike ride, the laptop needed to be open for collection. From the setup and constraints of

the testing, there was not a feasible way to hold the laptop open and ride the bike around. The

laptop was placed into a backpack to collect data while the testing took place. However, the

capabilities of the laptop only allowed data collection for 30 seconds after the laptop was shut.

This meant that the Serial Monitor could not collect data for more than 30 seconds [Figure 7].

Figure 5: Complete Final Design

Figure 6: Alternative Vertical

Turbine with Motor (Ref. 3)

Another constraint with testing again arose from the connections of the turbine to the SparkFun

components. Due to short wires connecting the turbine, the SparkFun RedBoard and breadboard

need to be held during testing [Figure 7].

Data Collection Method and Circuitry

To collect data using Arduino, a simple circuit was incorporated that connected the generator to a

resistor and an analog pin, then back to ground. The analog pin reads data from the generator with

values from 0-1023, which is then converted to voltage by multiplying the data by 0.004882814.

The decimal represents the fraction 5

1023, which is a proportion of the voltage the motor can output

to the output of the analog pin. An LCD was hooked up to make initial testing easier [Appendix

4]. The LCD was coded to show the voltage produced at a given time [Figure 8]. This helped the

rider see the voltage produced during testing on the bike without opening the Serial Monitor.

Once the data was collected for 30 seconds, the data was transferred to MATLAB and plotted it

onto a graph to figure out the maximum, minimum, and average voltage produced. This also

allowed calculation of the respective powers. Code used for the MATLAB graphs and Arduino

can be found in Appendix 7 and 8 respectively.

Figure 7: Testing of Product

Figure 8: Data Collection Circuitry

Results and Discussion

The goal of the initial test was to use a multimeter to decide which generator would provide the

most amount of voltage and the least amount of rotational resistance. The test was performed by

simply placing the multimeter and the generator in a simple circuit and observing the range of

voltage produced by spinning the motor manually at a relatively constant speed. Generally, the

SparkFun motor only generated around 0.5V. The motor used generated around 2.5V, however,

the turbine would have to overcome a large force to start spinning.

Initial testing for proof of concept was done using a hairdryer and the SparkFun motor. These tests

proved that the design was feasible and gave an initial idea of what range of voltages could be

generated by the SparkFun motor [Appendix 1]. The multimeter and hairdryer test ultimately

proved that a different motor would need to be used to generate more than 0.5V. The Amazon

motor was utilized which generally produced an average of 2.5 V, and a maximum of 5.5 V.

When the design was tested with a bike, it was kept at a speed of 6 - 7 mph. At first, the LCD

showed that the turbine could produce 5V, which is enough voltage to charge a phone. However,

a 330-ohm resister was incorporated into the circuit for the Serial Monitor to print out consistent

data for 30 seconds. The Serial Monitor does not operate above 5V.

Through suggestion from other in the Cornerstone class, it was realized that a voltage regulator

may have helped the project. The voltage regulator would have allowed the generator to produce

values as high as 5V, without allowing the voltage to rise to high levels that would harm the

circuit.12 In the future more testing can be done biking at higher speeds to see how long the voltage

can stay around 5V. Additional comparison tests were performed on the vertical wind turbine.

Data for these tests can be found in Appendix 2. Comparatively, the horizontal axis turbine

produced more voltage than the vertical turbine [Figure 9/Table 1].

Figure 9: Graphical Data from Bike Table 1: Table Data from Bike test

test with team design blades

Conclusion Though the amount of energy generated by the turbine may seem small, it is capable of powering

a light, as well as occasionally reaching the 5 volts needed to charge a common smartphone. If

traveling at a higher speed, not using a resistor to slow the flow of energy, and using a better motor,

the data provides evidence that this product is capable of providing enough energy to charge a

smartphone, or power a portable charger, to name a few.

However, the current design for the product does not maximize practicality and is not ready for

any commercial use. Some current issues/implications with the design include the fact that the

blades are not completely centered on the motor which adds some slight resistance. Also, the base

does not perfectly fit into the mount which can provide issues for the rider. The design of the

product was also made specifically for a horizontal shaft wind turbine, so the vertical turbine is

tougher to use with the current design. Furthermore, the design is not as aesthetically pleasing as

it could be.

In the future, this product would be adapted so that it is more efficient. For example, although the

current design does fit into the bike mount rather well, it could certainly be better as bumps can

cause it to fall out. The base was designed with testing in mind and not for the actual usage of the

product. So, the base would be changed so that the clamps close better on each side. Furthermore,

the base would include an LED in the front that could turn on while the user was riding, as well as

having a USB port for multiple uses. Other future changes to the bike could include adapting it so

it functions as a kid’s toy that could be attached to the bike, with possible designs being a windmill,

plane, or helicopter that lights up when riding. In the future, the cost for the product would

ultimately go down, everything can be 3D printed except the motor, and the SolidWorks design

can be adapted so it’s more visually pleasing and efficient.

Although there were some slight issues in the final design, the product still clearly proves the

concept and solves the initial problem. This product shows that it is possible to scale down a wind

turbine to a size that does not affect how someone rides a bike while also providing energy and

being inexpensive. Although further testing is needed to find the best design to get the most energy,

this turbine further proves that small scale wind turbines, in general, are possible and can be useful

in the future with the growing demand for renewable energy.13 This is different form of energy

generation compare to bike dynamo which generate electric power from the bike’s kinetic energy.

Hopefully the result from this educational model proposed in this paper would serve as a milestone,

and help future innovators to use this concept and technology to produce a profitable “real-world”

system to generate energy. The skills learned from this project were invaluable, as research, design,

trial and error, as well as technical writing are all important experiences within engineering and

energy

References:

1. Clean Revolution, Robert F. Service, Science, Vol. 350, Issue 6264, 2015

2. Electricity without Carbon, Quirin Schiermeier, Jeff Tollefson, Tony Scully, Alexandra Witze &

Oliver Morton, Nature, Vol 454, 816–823 (2008)

3. The Science of Teaching Science, M. Mitchell Waldrop, Nature, Vol 523, 272-274 (2015)

4. Physical and Virtual Laboratories in Science and Engineering Education, Ton de Jong, Marcia C.

Linn, and Zacharias C. Zacharia, Science, Vol. 340, Issue 6130, 2013

5. Renewable Energy Sources - Energy Explained, Your Guide To Understanding Energy -

Energy Information Administration

(www.eia.gov/energyexplained/?page=renewable_home).

6. Global Wind Energy Council. Global Wind Report 2018. Brussels, 2018,

https://gwec.net/wp-content/uploads/2020/02/Annual-Wind-Report_digital_full-1.pdf.

7. Third Planet Windpower (www.thirdplanetwind.com/energy/history.aspx).

8. Wind Energy Basics (windeis.anl.gov/guide/basic)

9. “Catch the Breeze.” New Scientist, (www.newscientist.com/article/dn24250-catch-the-

breeze).

10. Flight, Principles of. “Airfoil Design (Part One).” Flight Literacy, 28 Nov. 2017,

(www.flightliteracy.com/airfoil-design-part-one).

11. “Why Don't Wind Turbines Have More than 3 Blades?” CurioCity - CurioCité | Why Don't

Wind Turbines Have More than 3, (explorecuriocite.org/Explorer/ArticleId/193/why-dont-

wind-turbines-have-more-than-3-blades-193.aspx).

12. “THE BEST PLAN.” Catalog, www.madelectrical.com/electricaltech/howitworks.shtml.

13. Effects of turbine technology and land use on wind power resource potential, Erkka Rinne,

Hannele Holttinen, and Simo Rissanen, Nature Energy volume 3, p494–500(2018)

APPENDIX

Appendix 1: Sparkfun motor graphical and table data

Appendix 2: Vertical turbine with Amazon motor graphical data from the Bike test run

Appendix 3: Additional SolidWorks Photos

Appendix 4: Data Collection Basic Setup Circuitry

Appendix 5: Initial Designs

Appendix 6: Initial Assembly of Parts

Appendix 7: MATLAB Code

Appendix 8: Arduino Code

#include <LiquidCrystal.h> //the Liquid Crystal library contains commands for printing

to the display

LiquidCrystal lcd(13, 12, 11, 10, 9, 8); // tell the RedBoard what pins are connected to the

display

unsigned long time;

float voltage = 0; //the voltage measured from the TMP36

void setup() {

Serial.begin(9600); //sets up baud rate

lcd.begin(16, 2); //tell the LCD library that it is using a display that is 16

characters wide and 2 characters high

}

void loop() {

//read voltage

voltage = analogRead(A0) * 0.004882814; //convert the analog reading, which varies

from 0 to 1023, back to a voltage value from 0-5 volts

Serial.print("Voltage= ");

Serial.println(voltage,DEC);

Serial.print("Time: ");

double time = millis()/1000.;

Serial.println(time);

delay(500);

lcd.clear(); //clear the LCD

lcd.setCursor(0,0); //set the cursor to the top left position

lcd.print("Voltage: ");

lcd.print(voltage);

lcd.setCursor(0,1);

lcd.print("Time: ");

lcd.print(time);

delay(500); //delay for 1 second between each reading (this makes the

display less noisy)