Design and Implementation of Horizontal Axis Wind Turbine Supervisor

Design and Implementation of Horizontal Axis Wind Turbine Supervisor: Co- Supervisor: Engr. Muhammad Asif Engr. Rashid Jamil Satti Assistant Professor Lecturer Submitted By Imran Khan UET-2K14-EE-008 Muneeb Nasir UET-2K14-EE-019 Abdullah UET-2K14-EE-051 DEPARTMENT OF ELECTRICAL ENGINEERING SWEDISH COLLEGE OF ENGINEERING & TECHNOLOGY WAH CANTT Session 2014-2018 Design and Implementation of Horizontal Axis Wind Turbine Supervisor: Co- Supervisor: Engr. Muhammad Asif Engr. Rashid Jamil Satti Assistant Professor Lecturer Submitted By Imran Khan UET-2K14-EE-008 Muneeb Nasir UET-2K14-EE-019 Abdullah UET-2K14-EE-051 A Project Report submitted in partial fulfillment of the requirements for the award of Bachelor’s Degree in Electrical Engineering.

DEPARTMENT OF ELECTRICAL ENGINEERING SWEDISH COLLEGE OF ENGINEERING ; TECHNOLOGY Affiliated with UNIVERSITY OF ENGINEERING AND TECHNOLOGY TAXILA. CERTIFICATE OF APPROVAL Title of Project: Design and Implementation of Horizontal Axis Wind Turbine. Name of Students Registration No. Imran Khan UET-2K14-EE-008 Muneeb Nasir UET-2K14-EE-019 Abdullah UET-2K14-EE-051 Accepted by the Department of Electrical Engineering, Swedish College of Engineering ; Technology, Wah Cantt in partial fulfillment of the requirement for the BSc. Degree in Electrical Engineering. _______________________ _______________________ Supervisor Co-Supervisor Engr.

Muhammad Asif Engr. Rashid Jamil Satti Assistant Professor Lecturer _______________________ _______________________ Engr. Waqas Mehmood Engr. Muhammad Asif FYP Coordinator FYP Coordinator _______________________ Engr. Prof. Dr.

Umar Farooq Head of Department DECLARATION I declare that we are registered students of Swedish College of Engineering and Technology. Our project “Design and Implementation of Horizontal Axis Wind Turbine” is our own made project. I also declare that no harmful material is used in our project and no material contained in our thesis has been used before or submitted to our department and it is solely our own work. __________________ __________________ Imran Khan Muneeb Nasir UET-2K14-EE-008 UET-2K14-EE-019 __________________ Abdullah UET-2K14-EE-051 DEDICATION Every challenging work needs self or group efforts as well as guidance of elders especially those who were very close to our heart.

Our humble efforts we dedicated to our sweet and loving parents, whose affection, love, encouragement and prays of day and night make us able to get such success and honor. Along with all my hardworking and respected teachers. ACKNOWLEDGEMENT At the very beginning, we would like to express our deepest gratitude to almighty Allah for giving us the strength and the composure to complete our BSc Electrical Engineering and prepare this report within the scheduled time. We are grateful to our supervisor, Engr. Muhammad Asif and Co-Supervisor, Engr.

Rashid Jameel Satti, faculty of Electrical Department. They allowed us to encroach upon their precious time freely right from the very beginning of this project work till the completion of our Thesis. Their guidance, encouragement and suggestions provided us necessary insight into the project problem and paved the way for the meaningful ending the work in a short duration. We have no hesitation to say that, without their constant support and valuable advice from time-to-time, we would probably fail to complete the work in an appropriate manner.

ABSTRACT The exploitation of small horizontal axis wind turbines provides a clean, prospective and viable option for energy supply. Although great progress has been achieved in the wind energy sector, there is still potential space to reduce the cost and improve the performance of small wind turbines. An enhanced understanding of how small wind turbines interact with the wind turns out to be essential. It is very essential to make use of the non- conventional sources of energy like wind energy, solar energy, tidal energy, etc. Wind is considered to be one of the most promising resources in the renewable energy portfolio. Wind energy is used to generate electrical power by rotating the rotor shaft by the conversion of kinetic energy of wind into rotational energy of the shaft.

The objective of this work is to design and implement a horizontal axis wind turbine for domestic use and which can be available for public at low cost. Polyvinyl chloride, which is easily available, has been utilized to fabricate the blades. In the design process, basic aero foil section is considered with various forces acting on the blades are calculated theoretically and the design is optimized to get the optimum power output. A PMDC motor is used to get maximum output at production. Key Words: Renewable sources, Horizontal Axis Wind Turbine, wind Energy, hub, blade, fabrication and DC motor.

Table of Contents Certificate of Approval……………………………………………………………………… iii Declaration………………………………………………………………………………….. iv Dedication……………………………………………………………………………………. v Acknowledgement………………………………………………………………………….. vi Abstract……………………………………………………………………..……………….. vii Table of Contents…………………………………………………………………………… viii List of Figure…………………………………………………………………………………. ix List of Table………………………………………………………………………………… x Chapter No.1 Introduction 1.1 Historical development of wind turbines……..…………………….……………………

01 1.2 Current status of wind energy…..………………………………………………….…….. 03 1.3 Classification of wind energy …………………………………………………………….. 05 1.3.1 Vertical axis vs. horizontal axis wind turbines …………………………………………05 1.3.2 Large scale vs.

small scale wind turbines ………………………………………………09 Chapter No.2 Literature Review 2.1 Terminology…………………………………………………………………………….10 2.2 Betz’s Law ………………………………………………………………………………11 2.3 Applications of Small scale Wind Turbines ……………………………………………12 2.4 Blade Element Momentum Theory …………………………………………………….13 2.5 Types of blades …………………………………………………………………………15 2.6 CFD performance of blades …………………………………………………………….18 2.7 Design and testing of HAWT ……………………………………………………………19 2.8 Aerodynamics analysis of small HAWT ………………………………………………..20 Chapter No.3 Project Description ………………………………………………………………………….21 Chapter No.4 Hardware Description 4.1 Blades …………………………………………………………………………………25 4.2 Rotor Hub and Blades Attachment ……………………………………………………28 4.3 Nacelle …………………………………………………………………………………29 4.4 Bearings ……………………………………………………………………………….30 4.5 Shaft ……………………………………………………………………………………31 4.6 Sprockets ………………………………………………………………………………32 4.7 Yaw control ……………………………………………………………………………33 4.8 Generator ………………………………………………………………………………34 4.9 Tower and Base ………………………………………………………………………..35 Chapter No.5 Experimental results ………………………………………………………………………36 Chapter No.6 Conclusion ………………………………………………………………………………..39 Future Work ………………………………………………………………………………40 References ………………………………………………………………………………..50. LIST OF FIGURES Figure 1.1 (a) Western windmill USA Figure 1.2 (b) Persian Windmill 10th Centaury Figure 1.3. Total installed wind power capacity (MW) and world wind power market growth rate (%) 1996-2012 Figure 1.4 (a) Savonius Turbine Figure 1.5 (b) Curved blades Darrieus Turbine and (c) straight blades Darrieus Turbine Figure 1.5. Siemens Horizontal Axis Wind Turbine (model: SWT-2.3-82 VS) Figure 1.6. Typical configuration of a modern large scale HAWT Figure 2.1 The stream-tube representing wind flow through the actuator disc Fig. 2.2 Geometric and aerodynamic parameters of a generic blade strip.

Image reproduced from Figure 2.3 Flow Chart showing iterative scheme for the numerical model based on BEM theory. Figure 2.4 Single blade wind turbine. Figure 2.5 Two blades wind turbine. Figure 2.6 Three blades wind turbine. Figure 2.7 Blade binding moment response on different wind velocity.

Figure 3.1 A small scale wind turbine generating 400W. Figure 3.2 Wind turbine Aerodynamic lift. Figure 3.3 Windmill used for pumping water in American West since 18th century. Figure 3.4 The first advertisement by Halladay in 1800. Figure 3.5 First off shore wind turbines in North Sea of America. Figure 4.1 Blade design on Solid work software.

Figure 4.2 Blade designing process (Group members) Figure 4.3 Original blades (PVC) designed by group members. Figure 4.4 Polished three blades after manufacturing. Figure 4.5 Blades fixed in hub or Rotor Figure 4.6 Nacelle internal design on Solid work software. Figure 4.7 UCP-204 bearing Figure 4.8 Shaft used in HAWT Figure 4.9 Bearings holding the shaft Figure 4.10 Shows a detail view of chain mechanism Figure 4.11 shows the Yaw control of HAWT Figure 4.12 PMDC motor used for generation Figure 4.13 Tower and base view made of steel and iron Figure 5.2 shows the wind speed vs power output graph.

Figure 5.3 shows the output graph of voltage vs current. LIST OF TABLES Table 1.1 shows the cumulative wind power capacity from 2008-2012 Table 1.2 shows the difference between the vertical and horizontal axis wind turbine. Table 4.1 shows the values of motor. Table 5.1 shows the detail about different voltage and current on different wind speed.

CHAPTER NO.1 INTRODUCTION Wind energy, like most earthly energy resources, comes from solar power. Solar radiation causes the regions of unequal heating over land masses and oceans. This creates regions of high and low pressures and this causes the flow of air called wind. There has been an enormous increase in the global demand for energy in recent years as a result of industrial development and population growth.

Supply of energy is, therefore, far less than the actual demand. Adequate availability of inexpensive energy is the most important demand of today. Economic growth and industrialization both are dependent on the availability of energy. But today the problem is that world energy sources are fast depleting and these fast depleting energy resources have put the world in a grip of energy crisis. This is the time to take steps to conserve the conventional sources and also find the alternative sources of energy such as solar energy, wind energy, tidal energy, geothermal energy etc.

to generate the power. Wind energy is one of the prominent renewable energy sources on earth. Wind power utilization for electricity production has a huge resource and proven itself to be capable of producing a substantial share of the electricity consumption. The fuel of this electricity production is wind and it is the most important constraint for turbine design, as it creates loads the turbine has to withstand. Therefore, accurate knowledge about the wind is needed for planning, design and operation of wind turbines. This paper provides the process of fabricating the blades of a wind turbine with a desired output suitable for domestic purposes.

1.1 Historical Development of Wind Turbines Wind energy is one of the most abundant renewable energy resource on the earth and has been targeted for centuries. It’s predicted that human beings have been using wind energy in their daily work for about 4,000 years. As early as 1,700 B.C., King Hammurabi of Babylon used wind powered scoops to irrigate the plains of Mesopotamia. Wind was also used to grind grain and that’s the reason why we still speak of “windmills”, even though they are now hardly used for grinding grains 1. The American mills are still in existence and several of them are installed with a nearly unchanged design in Australia, Argentina and the USA.

American windmills (Western windmills) Figure 1.1 (a). A wind farm utilizing the American windmills for water pumping. Before European countries, horizontal-axis windmills were designed by Ebul?z (1153) from Artuk Turks and used in the region of Diyarbak?r in 1200’s. However, Northwest Europe, particularly France, Germany, Great Britain, Iberia and the Low Countries are considered to be the first region that developed the most effective type of windmill, one in which the shaft carrying the sails was oriented horizontally rather than vertically as in the Persian mill. In a relatively short time, tens of thousands of what it is called horizontal-axis European windmills were in use for nearly all mechanical task, including water pumping, grinding grain, sawing wood and powering tools.

The familiar cruciform pattern of their sails prevailed for almost 800 years, from the twelfth to the twentieth century 2. Figure 1.1 Western windmill USA 1. Figure 1.2 Persian Windmill 10th Century 1. The first written evidence of such windmills dates back to the 13th century 3.

There were some other types of horizontal axis windmills which existed in different parts of the world (mainly in the Occident) during different periods of time: Post windmill (1100s), Wipmolen Dutch (1400s), Dutch smock mill (1500s), Paltrock mill (1600s) and Gallery smock mill (1700s). Brief description about these windmills can be found in Ref. 4. However, none of the historical horizontal axis wind turbines gained as much popularity as the American farm windmill (sometimes also called Western mill).

These windmills were developed in the mid-19th century mainly to provide drinking water to people and cattle in North America. 1.2 Current Status of Wind Energy The fourth edition of the Global Wind Energy Outlook released on Nov 14, 2012 at Beijing by Greenpeace International and the Global Wind Energy Council states that wind power currently shares about 3.5% of global electricity demand and it is expected that the share could reach up to 12% by 2020 5. Figure 1.3 shows global cumulative installed wind power capacity over last 17 years 6. At the end of year 2012, the world-wide total wind power capacity was 282 gigawatts (GW), showing a growth of about 18.7 % (44 GW) over the preceding year.

It is important to note that although the year 2012 created a new record in total installed wind power capacity, the wind market has cooled down in relative terms. If we look at the annual growth rate, it had continued to increase since the year 2004, peaking at 32.1 % in year 2009. However, since then the growth has decreased substantially 7. Figure 1.3.

Total installed wind powerResearch Design303.3 Location of the Study303.4 Target Population313.5 Sample Size313.5.1 Sampling Procedure323.6 Research Instruments323.6.1 Questionnaire323.7 Pilot Study343.7.1 Instrument Validity343.7.3 Instrument Reliability343.8 Data Collection Procedure343.9 Data Analysis Techniques353.10 Ethical Considerations35CHAPTER FOUR37DATA ANALYSIS, PRESENTATION AND INTERPRETATION374.1 Introduction374.2 Response Rate374.3 General Information on Respondents384.3.1 Gender384.4.2 Parents Level of Education Statements424.5. Influence of Parental Income on Student Dropout Rate424.5.1 Parents /Guardians Occupation444.5.2 Parents /Guardians Occupation Statements464.6 Influence of Family Size on Student Dropout Rate474.6.1 Number of Family Members494.6.2 Family Size Statements494.7 Dropout Rate From Kenyan Public Universities50CHAPTER FIVE53SUMMARY OF THE STUDY, CONCLUSIONS AND RECOMMENDATIONS565.1 Introduction565.2 Summary of the Study Findings565.3. Conclusions of the Study595.4 Recommendations.595.5 Recommendations for Further Research60REFERENCES61APPENDICES66APPENDIX 1: LETTER OF INTRODUCTION66APPENDIX 2: QUESTIONNAIRE67 LIST OF TABLES Table 3.1 Sampling Frame28 TOC h u z Table 4.1 Response Rate38Table 4.2 Gender38Table 4.3 Age39Table 4.4 Working Experience39Table 4.5 Marital Status40Table 4.6 Parents/Guardian Level of Education41Table 4.7 A crossectional table showing the relationship between parent education and drop-out from university41Table 4.8 A crossectional table showing the relationship between parent education and drop-out from university42Table 4.9 A crossectional table showing the relationship betwe capacity (MW) and world wind power market growth rate (%) 1996-2012 9 Figure 1.3 presents cumulative wind power capacity from year 2008 to 2012 in top 10 countries and the same variable worldwide 12,14. The data indicates that even though the global wind power capacity exhibited the low growth rate (18.7 %) in year 2012, it increased over 133.5% during the last five years. It is also very interesting to note that 73.7% of the total power capacity (282,430 MW) in 2012 was contributed by 5 countries i.e. China, USA, Germany, Spain and India.

China’s wind power capacity continued to grow at the rate of over 21% in 2012. The United States has also gained the momentum and displayed the annual growth rate of 27.9 % in 2012, which is the highest growth rate in last three consecutive years. The installed wind power capacity in USA has reached up to 60,007 megawatts by the end of year 2012. In 2012, the electricity produced from wind power in the United States totaled to about 140 terawatt-hours, which is around 3.5 % of net electricity generation by all the energy sources 11. According to a report by the U.S. Department of Energy’s Wind and Water Power Program published in May 2011, the federal government allows owners of the qualified renewable energy facilities to receive tax credits of 2.2 cents for each kilowatt-hour (kWh) of electricity generated by the facility over a ten year period 10.

Several incentives have been provided to promote the deployment of small scale wind power generation. The owners of small wind turbines (100 kW or less) are eligible to receive tax credits worth 30% of the value of the facility 13. In addition, DOE offers loan guarantees to help the wind power firms to deploy innovative, clean energy technologies that reduce, avoid or sequester carbon dioxide and other emissions. 1.3 Classification of Wind Turbines There are broadly two ways to classify the wind turbines: (i) on the basis of the orientation of axis of rotation (vertical or horizontal) and (ii) on the basis of energy generating capacity (micro, small, medium, or large). 1.3.1 Vertical Axis vs. Horizontal Axis Wind Turbines There are essentially two kinds of wind turbines, when they are categorized on the basis of their orientation of the axis of rotation: Vertical Axis Wind Turbines (VAWTs) and Horizontal Axis Wind Turbines (HAWTs).

As the name suggests, the rotor of VAWTs rotates perpendicular to the ground while that of HAWTs spins parallel to the ground. It was explained in the previous section that most of the early wind turbines were vertical axis because they were relatively simple to construct (especially for the milling purpose) and they also didn’t require any mechanism to orient themselves in the direction of wind. In spite of these attributes, none of the old designs of VAWTs survived for long time. Savonius turbines are drag-type while Darrieus turbines are lift-type. More details about these designs will be discussed in the next section.

In principle, Savonius rotors normally have two cups or half drums attached to a central shaft in opposing directions, as shown in Fig. 1.4(a). Figure 1.4 (a) Savonius Turbine 17 The Darrieus-type VAWTs consists of two or more blades which are attached to a vertical central shaft. These blades can be curved (as shown in Fig.

1.5(b)). Irrespective of the curvature, the blades always have airfoil profile which creates aerodynamic lift, when they are exposed to the incident wind. This phenomenon creates moment along the axis and causes the central shaft to rotate, which ultimately runs the generator to produce electricity. The curved-blade Darrieus VAWTs ( as shown in fig.

1.5 (c)) have lower bending stress in the blades as compared to straight-blade Darrieus VAWTs and therefore former is more commercially successful 19. However, on the small-scale power production, the straight-bladed Darrieus VAWTs are more popular because of their simple blade design 21. The straight-bladed Darrieus VAWTs sometimes may have variable pitch angle. It has been found that constant pitch straight-bladed Darrieus VAWTs don’t have self-start ability 15. Figure 1.5 (b) Curved blades Darrieus Turbine and (c) straight blades Darrieus Turbine 17.

Figure 1.5. Siemens HorizoResearch Design303.3 Location of the Study303.4 Target Population313.5 Sample Size313.5.1 Sampling Procedure323.6 Research Instruments323.6.1 Questionnaire323.7 Pilot Study343.7.1 Instrument Validity343.7.3 Instrument Reliability343.8 Data Collection Procedure343.9 Data Analysis Techniques353.10 Ethical Considerations35CHAPTER FOUR37DATA ANALYSIS, PRESENTATION AND INTERPRETATION374.1 Introduction374.2 Response Rate374.3 General Information on Respondents384.3.1 Gender384.4.2 Parents Level of Education Statements424.5. Influence of Parental Income on Student Dropout Rate424.5.1 Parents /Guardians Occupation444.5.2 Parents /Guardians Occupation Statements464.6 Influence of Family Size on Student Dropout Rate474.6.1 Number of Family Members494.6.2 Family Size Statements494.7 Dropout Rate From Kenyan Public Universities50CHAPTER FIVE53SUMMARY OF THE STUDY, CONCLUSIONS AND RECOMMENDATIONS565.1 Introduction565.2 Summary of the Study Findings565.3. Conclusions of the Study595.4 Recommendations.595.5 Recommendations for Further Research60REFERENCES61APPENDICES66APPENDIX 1: LETTER OF INTRODUCTION66APPENDIX 2: QUESTIONNAIRE67 LIST OF TABLES Table 3.1 Sampling Frame28 TOC h u z Table 4.1 Response Rate38Table 4.2 Gender38Table 4.3 Age39Table 4.4 Working Experience39Table 4.5 Marital Status40Table 4.6 Parents/Guardian Level of Education41Table 4.7 A crossectional table showing the relationship between parent education and drop-out from university41Table 4.8 A crossectional table showing the relationship between parent education and drop-out from university42Table 4.9 A crossectional table showing the relationship betwental Axis Wind Turbine (model: SWT-2.3-82 VS) 17. As explained in the previous section, the rotor shaft of a HAWT is positioned in horizontal direction i.e. parallel to the ground.

The electric generator that is connected to the turbine rotor via the primary and secondary shafts is stored inside a nacelle box at the top of the tower. HAWTs are lift-type wind turbines and are very sensitive to changes in blade profile, design, and surface roughness. Another limitation with HAWTs is that they can’t catch the wind from all direction. They need a special mechanism to turn the rotor so that it always faces the wind 22. This was probably one of the main reasons why none of the historical HAWTs were so successful.

In fact, the American windmill was the first HAWT which had a fully automatically controlled yaw system. Yaw system of a HWAT is basically a component which is responsible for the orientation of the wind turbine rotor towards the wind. In small size HAWTs, the yaw system comprises of a simple roller bearing connected between the tower and the nacelle. A tail with a fin at the end is mounted on the back of nacelle which produces corrective moment to turn the wind turbine rotor into the wind. This type of yaw system is called ‘passive yaw system’. The large scale (megawatt) HAWTs however needs an active yaw mechanism.

The active yaw systems are normally equipped with a wind sensor which senses the direction of wind, and a servo motor which produces required torque to rotate the nacelle of the wind turbine against the stationary tower. This study is primarily focused on HAWT, so more details about this kind of turbines will be given in later sections/chapters. A HAWT, in general, consists of a rotor, a gear box, a generator, and a yaw system. The rotor of a HAWT includes two to three blades connected together with a hub.

The hub is attached to a main shaft (sometimes also called primary shaft or low speed shaft), which passes through bearings and connects to a gear-train. The gear train amplifies the rotational speed and provides higher rpm to a secondary shaft (sometimes also called high speed shaft). The secondary shaft drives a generator which produces electricity. The gear-box, the primary and secondary shafts, and the generator are contained inside a nacelle box. The nacelle box also contains a yaw system to orient the rotor, and a heat exchanger to cool down the generator.

Figure 1.6 demonstrates all the major components of a large scale modern HAWT 23. Figure 1.6. Typical configuration of a modern large scale HAWT 23. Table 1.2 shows the difference between the vertical and horizontal axis wind turbine. 1.3.2 Large Scale vs. Small Scale Wind Turbines The definition of “small” and “large” scale windmill has remained vague in the literature of wind energy.

Small wind turbine was initially defined on the basis of its capability to produce electrical power sufficient enough to cover individual household electricity demands 25. But the problem lies in the fact that the consumption of electricity by a household itself is very debatable because it varies with time and place. For example, an average American family needs a 10 kW turbine to cover their full consumption, while a European household requires a 4 kW turbine, which further reduces to a 1 kW turbine for an average Chinese household 24. Lacking any credible unanimous definition, the range for the rated power capacity of small scale wind turbines vary from few watts to few hundred kilowatts. Chapter No.2 Literature Review 2.1 Terminology • Leading edge: It’s the point at the front of an airfoil, which has the maximum curvature.

• Trailing Edge: It’s the point at the rear of an airfoil, which has the maximum curvature. • Chord Line: It’s the straight line that connects the leading edge and trailing edge of an airfoil • Chord Length (c): It’s the length of the chord line. • Suction Surface: It is the upper surface of an airfoil and is generally associated with higher velocity and lower static pressure than the pressure surface. • Pressure Surface: It is the lower surface of an airfoil and is generally associated with lower velocity and higher static pressure than the suction surface. • Mean Camber Line: It is the locus of a set of points that lie midway between the upper and lower surfaces. • Maximum Thickness: It’s the maximum thickness of an airfoil when measured perpendicular to the camber line.

Apart from the nomenclature of the airfoil, we shall also use few terms that are often used to indicate and characterize the performance of a wind turbine, particularly a HAWT. • Power coefficient: It is defined as the amount of mechanical power produced by a wind turbine against the total available wind power. Sometimes, it’s also called coefficient of performance and mathematically it is calculated using following expression 4. • Tip Speed Ratio: Tip speed ratio is the most commonly and conveniently used scaling parameter, which integrates the principle aerodynamic effect of the wind speed, rotor size and rotor’s angular speed with the power coefficient of the wind turbine rotor. It evaluates the tangential speed of the turbine’s blade with respect to the free wind speed and is given as 4.

• Overall Efficiency: Power and torque coefficients characterize the performance of wind turbine rotor only. The third parameter, overall efficiency is defined as the net electric power produced against the total available wind power. • Cut-in Speed: The cut-in speed of a wind turbine is defined as the minimum wind speed at which the wind turbine starts on its own and generates some usable power. • Rated Speed: The rated speed of a wind turbine is defined as the minimum wind speed at which the wind turbine generates its indicated rated power.

• Cut-out Speed: The cut-out speed of a wind turbine is the maximum wind speed up to which the wind turbine should operate. This is required as a safety feature to protect the wind turbine from being damaged at the high wind speed. 2.2 Bitz’s Law Betz’ law defines the maximum power that can be extracted from the wind by a wind turbine in an open flow. This law can be derived using principles of conservatiResearch Design303.3 Location of the Study303.4 Target Population313.5 Sample Size313.5.1 Sampling Procedure323.6 Research Instruments323.6.1 Questionnaire323.7 Pilot Study343.7.1 Instrument Validity343.7.3 Instrument Reliability343.8 Data Collection Procedure343.9 Data Analysis Techniques353.10 Ethical Considerations35CHAPTER FOUR37DATA ANALYSIS, PRESENTATION AND INTERPRETATION374.1 Introduction374.2 Response Rate374.3 General Information on Respondents384.3.1 Gender384.4.2 Parents Level of Education Statements424.5. Influence of Parental Income on Student Dropout Rate424.5.1 Parents /Guardians Occupation444.5.2 Parents /Guardians Occupation Statements464.6 Influence of Family Size on Student Dropout Rate474.6.1 Number of Family Members494.6.2 Family Size Statements494.7 Dropout Rate From Kenyan Public Universities50CHAPTER FIVE53SUMMARY OF THE STUDY, CONCLUSIONS AND RECOMMENDATIONS565.1 Introduction565.2 Summary of the Study Findings565.3. Conclusions of the Study595.4 Recommendations.595.5 Recommendations for Further Research60REFERENCES61APPENDICES66APPENDIX 1: LETTER OF INTRODUCTION66APPENDIX 2: QUESTIONNAIRE67 LIST OF TABLES Table 3.1 Sampling Frame28 TOC h u z Table 4.1 Response Rate38Table 4.2 Gender38Table 4.3 Age39Table 4.4 Working Experience39Table 4.5 Marital Status40Table 4.6 Parents/Guardian Level of Education41Table 4.7 A crossectional table showing the relationship between parent education and drop-out from university41Table 4.8 A crossectional table showing the relationship between parent education and drop-out from university42Table 4.9 A crossectional table showing the relationship betweon of mass and momentum of the airflow flowing through an idealized “actuator disc” that emulates the wind turbine. Let’s consider a stream-tube of air stream flowing through the actuator disc as shown in Figure 1.10.

The stream-tube has upstream wind speed equal to µ1 and cross-sectional area equal to A1. The actuator disc extracts the kinetic energy of the wind and thus causes it to slow down to speed µ2. Since air flowing within the stream-tube does not get compressed (assuming incompressible flow), the cross-sectional area A2 of the stream-tube must expand to area in order to accommodate the slower moving air. Also, due to the static pressure drop (þ+-þ-) across the actuator disc, the downstream wind continues to expand till the point where static pressure of the flow returns to atmospheric level þ? and equilibrium is achieved.

The far downstream flow has cross-sectional area A3 and wind speed equal to µ3. Figure 2.1 The stream-tube representing wind flow through the actuator disc 8. 2.3 Applications of Small scale Wind Turbines The recent advancements in the field of microelectronics have not only miniaturized the wireless devices but have also decreased their power requirement by an order of magnitude. Wireless sensors nodes, for example, now need power less than 1 MW 23. Such nodes are used in variety of applications such as gas and chemical sensors, temperature, pressure and humidity monitoring, motion detector, structural health monitoring, and explosives detection 15.

The over-expanding usage of wireless devices however has brought challenges in terms of finding a suitable power source, especially for the remote applications. In majority of such cases, currently lithium cell batteries are used, which presents maintenance challenge because these batteries need to be regularly monitored and replaced. One of the most convenient methods of supplying the required power to the miniature electronic devices is by harvesting the wind energy. The conventional large scale wind turbines (LSWTs) are efficient and the modern mega-watt wind turbines have power coefficient up to 40%-45% 24. However, they need high wind speed to operate; typical rated wind speed is around 12 m/s-14 m/s. Further, their installations are limited to areas far from the city or township due to some practical concerns related to safety hazards and noise emission.

In comparison, small scale wind turbines (SSWTs) can operate at low wind speed, generate minimal noise and there are no known safety hazards. In spite of several advantages, very few small-scale wind turbine models have been developed. Table 1.3 shows some of the currently available small to mid-scale wind turbines 25. It is interesting to note that most of these wind turbines are in mid-scale range. The rated wind speed is typically above 10 m/s. None of the wind turbines except micro-wind turbine can operate efficiently at the wind speed condition below 5 m/s.

The micro-wind turbine which operates in range of 2 m/s-7 m/s has optimal power coefficient of 18% which is quite low. ?F500 is the only SSWT which has good overall efficiency value of 25%, but its rated wind speed is 12 m/s. The current status of the SSWTs essentially emphasizes the lack of suitable SSWT models that can operate near ground level at wind speeds of the order of few meters per second. 2.4 Blade Element Momentum Theory The steady state aerodynamics of wind turbines is commonly analyzed by using momentum and blade element theory.

Momentum theory refers to a control volume analysis of the forces acting on the blade based on the conservation of linear and angular momentum. Blade element theory refers to an analysis of forces at a blade section, as a function of blade geometry. According to the blade element theory, the forces on the blades of a wind turbine are expressed as a function of lift and drag coefficients and the angle of attack (AoA) 11. The results of these approaches can be combined into what is known as strip theory or BEM theory. The BEM theory is based on the subdivision of the rotor disk into concentric rings of radial width dr and mean radius r. Each ring intersects the rotor blades forming blade elements or strips.

The flow data and the aerodynamic forces acting on each strip are determined by solving two equations, obtained by combining linear and angular momentum conservation and classic lift and drag theory. One equation results from equating the ring axial thrust determined with the one-dimensional (1D) conservation of the linear momentum to the axial thrust computed with the lift and drag forces acting on the blade strips intersected by the ring. The other equation results from equating the ring torque determined with the 1D conservation of the angular momentum to the torque produced by the lift and drag forces acting on the intersected strips. The main geometric and aerodynamic parameters of a generic strip are depicted in Fig.

2.1, in which the section lift and drag forces are denoted by dFL and dFD respectively. Denoting by dT the thrust acting on a ring, the local thrust coefficient is CT = dT/ (0.5?U2dA) (1) Where dA = 2?rdr is the area of the ring, and ? and U are the freestream density and velocity respectively. The local thrust coefficient computed using the conservation of linear momentum is: CT = 4a (1?a) (2) Where a is the axial induction factor. The local thrust coefficient computed using lift and drag theory is: CT =?r (1?a) 2 (3) sin2? (CL cos? +CD sin?) (4) Where ?r = (Nbc)/ (2?r) is the local solidity, Nb is the number of blades, c is the airfoil chord length, and CL and CD are the lift and drag coefficients respectively. The symbol ? denotes the angle of the relative wind velocity vector Urel on the rotor plane. Its expression is ? = arc tan (1?a)/ ((1+a?) ?r), where a? is the circumferential induction factor and ?r = ?r/U is the local speed ratio, where ? is the angular speed of the rotor.

Urel is expressed as Urel =U (1?a)/sin?. Equating Eqs. 2.1 And 2.2 yields one equation in the two unknowns a and a?, since CL and CD are ultimately also functions of the induction factors. In fact, these force coefficients can be obtained with panel or CFD codes (see Sect. 2.2 for details) or experimental data as functions of the Reynolds number (Re), which depends on Urel and the relative AoA ?, the angle between the airfoil chord and Urel.

As shown in Fig. 2.1, ? = ? ??p, where ?p is the section pitch angle. This parameter depends only on geometric features, and its expression is ?p = ?p, 0+?T, where ?p, 0 is the pitch angle of the blade and ?T is the section twist angle. Denoting by dQ the torque acting on a rotor ring, the local torque coefficient is CQ = dQ/ (0.5?U2rdA).

The local torque coefficient computed using the conservation of angular momentum is: CQ = 4a? (1?a) ?r (5) The local torque coefficient computed using lift and drag theory is: CQ =?r (1?a) 2 (6) sin2? (CL sin? ?CD cos?) (7) Equating Eqs. 2.3 And 2.4 yields another equation in the two unknowns a and a?. The nonlinear system resulting by equating the two expressions of CT and CQ for each strip need to be solved with an iterative routine based for instance on Newton’s method or the method of successive substitution. The two-dimensional (2D) CL and CD data are stored in tables as functions of Re and ?, and such data are computed in a pre-processing step. Once the flow state of each strip is known, the elemental power dP can be computed. The non-dimensional local power coefficient CP = dP/ (0.5?U3dA) can be expressed as follows: CP = ?r (1?a) 2?r (8) sin2? (CL sin? ?CD cos?) (9) Fig.

2.2 Geometric and aerodynamic parameters of a generic blade strip. Image reproduced from 13. 2.5 Types of Blades There are essentially five blade parameters which influence the power coefficient of a wind turbine. These parameters are: (1) airfoil, (2) twist angle, (3) chord length, (4) tapering angle, and number of blades. Each of these parameters needs to be optimized to achieve the best possible power coefficient.

The complete design procedure is divided into two parts, as shown in Figure 2.3. Part I is used to optimize the blade parameters. Once, the turbine blades are optimized, Part II of the model checks the consistency of turbine’s performance in the entire range of operating wind speed. A wind turbine may perform very efficiently at its design point but its power coefficient may drop sharply when wind speed is increased.

The numerical model was next applied to design a SSWT which is intended to produce 1W output power at very low wind speed in the range of 7-10 mph (approx. 3.1-4.5 m/s). We will explain the formulation and working of the model using the design procedure of this wind turbine. Figure 2.3 Flow Chart showing iterative scheme for the numerical model based on BEM theory 9. Wind turbine blades are used to extract the kinetic energy of wind and convert to mechanical energy.

These blades are made up of fiber glass-reinforced polyester or wood-epoxy. Wind turbines have one or two or three or multiple blades based up on the construction. Most of the HAWT have three blades. These are connected to rotor hub.

Multiple blade concept is used in earlier days for pumping water and grinding etc. • Single Blade Turbine: It reduces the cost and weight of turbine. These are rarely used due to tower shadow effects, need counter weight on the other side of the blade and less stability. Figure 2.4 Single blade wind turbine 9 • Two Blades Turbine: It requires more complex design due to sustain of wind shocks. It is also less stable.

It saves the cost and weight of other rotor or blade. Figure 2.5 Two blades wind turbine 9 • Three Blades Turbine: Modern wind turbine uses three blades concept. Because this structure have high strength to withstand heavy wind storms. Less effect due to tower shadow. Produces higher output.

Figure 2.6 Three blades wind turbine 9. 2.6 CFD Performance of Blades A detailed review on the wind turbine aerodynamics regarding blade design and aerodynamic performance analysis using the BEM and CFD based approaches was firstly conducted. The wake induction corrections and stall corrections of the BEM method were examined through a case study of the NREL/NASA Phase VI wind turbine. A hybrid stall correction model was proposed to analyses wind turbine power performance.

The proposed model shows improvement in power prediction for the validation case, compared with the existing stall correction models. The effects of the key rotor parameters of a small wind turbine as well as the blade chord and twist angle distributions on power performance were investigated through two typical wind turbines, i.e. a fixed-pitch variable-speed (FPVS) wind turbine and a fixed-pitch fixed-speed (FPFS) wind turbine. An engineering blade design and analysis code was developed in MATLAB to accommodate aerodynamic design and analysis of the blades. The linearization for radial profiles of blade chord and twist angle for the FPFS wind turbine blade design was discussed. Results show that, the proposed linearization approach leads to reduced manufacturing cost and higher annual energy production (AEP), with minimal effects on the low wind speed performance.

The CFD predicted lift and drag coefficients of the airfoil S809 were compared with wind tunnel test data and the 3D CFD modelling method of the NREL/NASA Phase VI wind turbine were validated against measurements. Airfoil aerodynamic characterization and wind turbine power performance as well as 3D flow details were studied. The detailed flow characteristics from the CFD modelling are quantitatively comparable to the measurements, such as blade surface pressure distribution and integrated forces and moments. The verified CFD modelling methods and wind tunnel testing were employed in aerodynamic characterization of the airfoil DU93-W-210. 3D CFD modelling was applied for power performance analysis of the BEM-designed FPVS and FPFS wind turbines. The CFD results and BEM results are generally agreeable.

The flow moves in the chord-wise direction at low wind speeds and the span-wise flow occurs at high wind speeds for all the wind turbines investigated. It is confirmed that the CFD approach is able to provide a more detailed qualitative and quantitative analysis for wind turbine airfoils and rotors. With more advanced turbulence model and more powerful computing capability, it is prospective to improve the BEM method considering 3D flow effects. To investigate the 3D flows around a wind turbine blade, the incompressible Reynolds-Averaged-Navier-Stokes (RANS) CFD method has been increasingly employed in the engineering and research community, particularly recently with the rapid development of computer capacity. It is expected that the RANS based CFD approach will be in practical use in the wind energy sector in the near future 10.

This section reviews the key elements in the RANS CFD method, the current status and difficulties in this approach for wind turbine aerodynamic analysis. Regarding to wind turbine rotor performance prediction using the 3D CFD method, the current status and challenges are reviewed below. Major efforts will focus on the generation of an adequate mesh, and turbulence ; transition model. To model a wind turbine rotor using the CFD method, an exact 3D geometry of the wind turbine rotor is needed in a digitized format, usually in a “computer aided design” (CAD) format. A small wind turbine blade is generally twisted and tapered. The sectional airfoil of the blade is a shape often with a small rounded leading edge, and a sharp trailing edge or thin blunt trailing edge.

A sufficient resolution of the boundary layer mesh is needed to solve the boundary layer around the blade surfaces. A full 3D wind turbine rotor which uses the S809 airfoil were accomplished in Langtry’s research, the Research Design303.3 Location of the Study303.4 Target Population313.5 Sample Size313.5.1 Sampling Procedure323.6 Research Instruments323.6.1 Questionnaire323.7 Pilot Study343.7.1 Instrument Validity343.7.3 Instrument Reliability343.8 Data Collection Procedure343.9 Data Analysis Techniques353.10 Ethical Considerations35CHAPTER FOUR37DATA ANALYSIS, PRESENTATION AND INTERPRETATION374.1 Introduction374.2 Response Rate374.3 General Information on Respondents384.3.1 Gender384.4.2 Parents Level of Education Statements424.5. Influence of Parental Income on Student Dropout Rate424.5.1 Parents /Guardians Occupation444.5.2 Parents /Guardians Occupation Statements464.6 Influence of Family Size on Student Dropout Rate474.6.1 Number of Family Members494.6.2 Family Size Statements494.7 Dropout Rate From Kenyan Public Universities50CHAPTER FIVE53SUMMARY OF THE STUDY, CONCLUSIONS AND RECOMMENDATIONS565.1 Introduction565.2 Summary of the Study Findings565.3. Conclusions of the Study595.4 Recommendations.595.5 Recommendations for Further Research60REFERENCES61APPENDICES66APPENDIX 1: LETTER OF INTRODUCTION66APPENDIX 2: QUESTIONNAIRE67 LIST OF TABLES Table 3.1 Sampling Frame28 TOC h u z Table 4.1 Response Rate38Table 4.2 Gender38Table 4.3 Age39Table 4.4 Working Experience39Table 4.5 Marital Status40Table 4.6 Parents/Guardian Level of Education41Table 4.7 A crossectional table showing the relationship between parent education and drop-out from university41Table 4.8 A crossectional table showing the relationship between parent education and drop-out from university42Table 4.9 A crossectional table showing the relationship betwetransition model was reported to be compatible with modern CFD techniques such as unstructured grids and massively parallel execution, and the transition model was claimed to be well suited to predict wind turbine rotor aerodynamics 18. In summary, the transition model can improve the results based on 2D airfoil aerodynamic data; transition modelling in 3D under stall conditions is a complex problem and remains a hot research topic at present. As demonstrated by many researchers, all RANS models lack the ability to model stall at high wind speeds 14. Another suggested way is DES.

But the DES method is much stricter and sensitive on mesh resolution and is highly computational expensive. The representative work of this approach used in wind turbine rotor aerodynamics is presented by Li in 2012 11. Within the limitation of time and resource in this project, it is not realistic to use the DES method. However, it is possible to provide an insight with detailed information using the 3D RANS-CFD method, i.e.

pressure distribution, torque, moments and force coefficients along the span-wise direction, and therefore providing a more comprehensive understanding of the stall phenomenon. This chapter reviewed the BEM based approach and the CFD based approach for wind turbine blade design and aerodynamic performance analysis, including its advantages, limitations, applications and current status. BEM provides an efficient way of blade design and aerodynamic performance analysis. However, the stall correction models and the wake correction models are still being researched. The 3D CFD approach has been proposed by researchers aiming to obtain a detailed 3D flow but has not achieved the required maturity to become an engineering tool in wind turbine blade design 14. Modelling wind turbine in a 3D frame is a great challenge.

The first blade shape is optimal twist and tapered (OPT); this blade is designed using blade element momentum (BEM) theory. The second is un-tapered and optimal twist (UOT), this blade has the same twist distribution as the (OPT) but with a constant chord. The third is tapered un-twisted (TUT), this blade has the same chord variations as the OPT blade. The fourth is un-tapered un-twisted (UUT). The effect of nacelle, shaft and tower existence on the performance of the four designs has been investigated also in the present work.

All simulations are performed by using shear stress transport (SST) k-? turbulence model. The power coefficient of OPT blade reach to 0.317 at TSR = 5. Meanwhile, the maximum power coefficient (C p =0.3348 at TSR=4) has been recorded in the UOT blade. The TUT and UUT blade recorded a lower power coefficient, this is due to their always operations in stall and turbulence conditions.

The performance of a model wind turbine is simulated with three different CFD methods: actuator disk, actuator line and a fully resolved rotor. The simulations are compared with each other and with measurements from a wind tunnel experiment. The actuator disk is the least accurate and most cost-efficient, and the fully resolved rotor is the most accurate and least cost-efficient. The actuator line method is believed to lie in between the two ends of the scale.

The fully resolved rotor produces superior wake velocity results compared to the actuator models. On average it also produces better results for the force predictions, although the actuator line method had a slightly better match for the design tip speed. Forces for Lift and drag on the blade has an important role in the wind turbine performance. The main purpose of this work is to perform CFD analysis of a blade and airfoil of wind turbine using k-? SST model. In this present study NACA 634 -221 airfoil profile is taken for the modeling and then analysis of the blade. The lift and drag forces are calculated for the blade at different AOA (angle of attack).

For present work the blade length is taken 38.98 meter, which is a redesigned blade for VESTAS V82-1.65MW horizontal axis wind turbine blade. 2.7 Design and Testing of HAWT Utility-scale wind turbines require active control systems to operate at variable rotational speeds. As turbines become larger and more flexible, advanced control algorithms become necessary to meet multiple objectives such as speed regulation, blade load mitigation, and mode stabilization. At the same time, they must maximize energy capture. The National Renewable Energy Laboratory has developed control design and testing capabilities to meet these growing challenges.

Several algorithms that seek to maximize power production in below rated wind speeds have been evaluated through simulation and field testing. The importance of precise, prior knowledge of the tip speed ratio at which maximum power coefficient is attained has been documented, and an adaptive control algorithm has been developed. Linear, state-space models that incorporate sufficient detail of wind turbine dynamics have been designed to mitigate blade loads, reduce tower motion, minimize blade pitch actuator demand, and maintain speed regulation. Because coherent turbulence can be generated in atmospheric boundary layers where large wind turbine will operate, the vortex/wind turbine interaction has been quantified and a blade load mitigation control scheme implemented in simulation. All these activities improve the viability of multi megawatt wind turbine deployment and increase turbine reliability.

The highly nonlinear wind turbine dynamics must be linearized about an operating point to allow for state-space representations. Tools have been developed that provide linear wind turbine models with as many as 18 degrees of freedom 6. The ability to use state-space based control design to regulate rotor speed in above-rated wind speeds and to enhance damping in low-damped flexible modes of the wind turbine was investigated by Wright 5. Incrementally increasing the modeled states from 1 to 7 identified modes that tend to become unstable in closed-loop control, such as the drivetrain torsion mode.

This mode was stabilized by creating an additional control loop that commanded slight variations in generator torque to accommodate drive-train torsion flexibility. In addition to stabilizing the mode, the demand on the blade pitch actuators was reduced. Tower top and blade deflection were reduced when damping was added to these modes through pole placement in the state-space controller as shown in Figure 3. Finally, disturbance accommodating control (DAC) methods were used to reject wind disturbances that are modeled as steps (uniform over the rotor disk) or sinusoids (spatial variation resulting from vertical shear). Wind turbines on towers nearly 100 m high operate in atmospheric boundary layers with different turbulence generation mechanisms than those that occur closer to the ground.

This coherent turbulence contains vorticity that is not predicted with current wind turbine simulation models and that adversely affects wind turbine blade fatigue life. A simple, Rankine, vortex model was used as input to a wind turbine simulation to quantify the vortex/rotor interaction 7. The vortex characteristics (size, orientation, circulation strength) that contribute to high cyclic blade loads, which reduce blade fatigue life, were identified (Figure 2.7). A disturbance model that incorporates the gross vertical shear property of the vortex impinging on the wind turbine rotor was used in a DAC design to demonstrate the potential for advanced control to address this problem. Blade pitch control was used to mitigate the blade loads induced by the vortex by 9% as compared to a standard proportional-integral controller. However, an idealized model that incorporated highly detailed vortex inputs indicates that up to 30% load mitigation is possible if the disturbance model incorporates sufficient vortex detail.

Figure 2.7 Blade binding moment response on different wind velocity. As wind turbines become larger and more flexible, advanced control becomes essential to achieve stable operation in turbulent, above-rated wind speeds. Blade pitch angle control is used to shed excess torque by regulating rotor speed to produce rated power. In addition to rotor speed regulation, load mitigation and vibration attenuation become important objectives. 2.8 Aerodynamics Analysis of Small HAWT Horizontal-axis wind turbines use different types of aerodynamic control to achieve peak power and optimum performance control.

Nearly all turbines use an induction or synchronous generator interconnected with the utility grid. These generators maintain a constant rotor speed during normal operation, so aerodynamic control is needed only to limit and optimize power output. Variable speed control has been considered as a means of improving the aerodynamic efficiency of the rotor and reducing dynamic loads. This type of control results in the rotor speed changing to maintain a constant ratio between blade tip speed and wind speed (tip speed ratio). Medium and large-scale HAWT rotors usually contain a mechanism for adjusting blade pitch, which is the angle between the blade chord line and the plane of rotation. This pitch-change mechanism, which may control the angle of the entire blade (full-span pitch control) or only that of an outboard section (partial span pitch control), provides a means of controlling starting torque, peak power, and stopping torque.

Peak power is controlled by adjusting blade pitch angle to progressively lower angles of attack to control increasing wind loading. Pitch control offers the advantage of more positive power control, decreasing thrust loads as blades pitch toward feather in high winds and low parked rotor loads while the turbine is not operating in extreme winds. One disadvantage of pitch control is the lack of peak power control during turbulent wind conditions. Some HAWTs have fixed-pitch stall-controlled blades, avoiding the cost and maintenance of pitch-change mechanisms by relying on aerodynamic stall to limit peak power.

Passive power regulation is achieved by allowing the airfoils to stall. As wind speed increases stall progresses outboard along the span of the blade causing decreased lift and increased drag. One disadvantage of stall-controlled rotors is that they must withstand steadily increasing thrust loads with increasing wind speed because drag loads continue to increase as the blade stalls. Another disadvantage is the difficulty of predicting aerodynamic loads in deep stall. In addition to partial-span and full-span pitch control, several types of aerodynamic brakes have been used for stall-controlled rotors.

A simplified form of aerodynamic control mechanism is a tip brake or tip vane, in which a short outboard section of each blade is turned at right angles to the direction of motion, stopping the rotor by aerodynamic drag or at least limiting its speed. Patchable tips and pivoting tip vane have been used with reasonable success. Yaw drive mechanism is also required so that the nacelle can turn to keep the rotor shaft properly aligned with the wind. An active yaw drive (one which turns the nacelle to a specified azimuth) contains one or two motors (electric or hydraulic), each of which drives a pinion gear against a bull gear and an automatic yaw control system with its wind direction sensor mounted on the nacelle. A passive yaw drive permits wind forces to orient the nacelle.

The majority of the chapter details the classical analytical approach for the analysis of horizontal axis wind turbines and the performance prediction of these machines. The analysis of the aerodynamic behavior of wind turbines can be started without any specific turbine design just by considering the energy extraction process. A simple model, known as actuator disc model, can be used to calculate the power output of an ideal turbine rotor and the wind thrust on the rotor. Additionally more advanced methods including momentum theory, blade element theory and finally blade element momentum (BEM) theory are introduced. BEM theory is used to determine the optimum blade shape and also to predict the performance parameters of the rotor for ideal, steady operating conditions.

Blade element momentum theory combines two methods to analyze the aerodynamic performance of a wind turbine. These are momentum theory and blade-element theory which are used to outline the governing equations for the aerodynamic design and power prediction of a HAWT rotor. Chapter No.3 Project Description A horizontal-axis wind turbine (HAWT) is a wind turbine in which the axis of the rotor’s rotation is parallel to the wind stream and the ground. All grid-connected commercial wind turbines today are built with a propeller-type rotor on a horizontal axis (i.e. a horizontal main shaft).

Most horizontal axis turbines built today are two- or three-bladed, although some have fewer or more blades. The purpose of the rotor is to convert the linear motion of the wind into rotational energy that can be used to drive a generator. The same basic principle is used in a modern water turbine, where the flow of water is parallel to the rotational axis of the turbine blades. The wind passes over both surfaces of the airfoil shaped blade but passes more rapidly over the longer (upper) side of the airfoil, thus creating a lower-pressure area above the airfoil. The pressure differential between top and bottom surfaces results in aerodynamic lift.

In an aircraft wing, this force causes the airfoil to rise, lifting the aircraft off the ground. Since the blades of a wind turbine are constrained to move in a plane with the hub as its center, the lift force causes rotation about the hub. In addition to the lift force, a drag force perpendicular to the lift force impedes rotor rotation. A prime objective in wind turbine design is for the blade to have a relatively high lift-to-drag ratio. This ratio can be varied along the length of the blade to optimize the turbine’s energy output at various wind speeds.

HAWTs can be subdivided into upwind wind turbines and downwind wind turbines. Compare with vertical-axis wind turbine. Figure 3.1 A small scale wind turbine generating 400W 11 Horizontal-axis wind turbines (HAWT) have the main rotor shaft and electrical generator at the top of a tower, and may be pointed into or out of the wind. Small turbines are pointed by a simple wind vane, while large turbines generally use a wind sensor coupled with a servo motor. Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive an electrical generator.

A small wind turbine is a wind turbine used for microgeneration as opposed to large commercial wind turbines, such as those found in wind farms with greater individual power output. The Canadian Wind Energy Association (CanWEA) defines “small wind” as ranging from less than 1000 Watt (1 kW) turbines up to 300 kW turbines. The smaller turbines may be as small as a 50 Watt auxiliary power generator for a boat, caravan, or miniature refrigeration unit. The IEC-61400-2:2006 Standard defines small wind turbines as wind turbines with a rotor swept area smaller than 200 m2, generating at a voltage below 1000 Vac Or 1500 Vdc. Figure 3.2 Wind turbine Aerodynamic lift. HAWTs are characterized as either high- or low-solidity devices, in which solidity refers to the percentage of the swept area containing solid material.

High-solidity HAWTs include the multi bladed types that cover the total area swept by the blades with solid material in order to maximize the total amount of wind coming into contact with the blades. An example of the high-solidity HAWT is the multi bladed turbine used for pumping water on farms, often seen in the landscapes of the American West. Low-solidity HAWTs most often use two or three long bResearch Design303.3 Location of the Study303.4 Target Population313.5 Sample Size313.5.1 Sampling Procedure323.6 Research Instruments323.6.1 Questionnaire323.7 Pilot Study343.7.1 Instrument Validity343.7.3 Instrument Reliability343.8 Data Collection Procedure343.9 Data Analysis Techniques353.10 Ethical Considerations35CHAPTER FOUR37DATA ANALYSIS, PRESENTATION AND INTERPRETATION374.1 Introduction374.2 Response Rate374.3 General Information on Respondents384.3.1 Gender384.4.2 Parents Level of Education Statements424.5. Influence of Parental Income on Student Dropout Rate424.5.1 Parents /Guardians Occupation444.5.2 Parents /Guardians Occupation Statements464.6 Influence of Family Size on Student Dropout Rate474.6.1 Number of Family Members494.6.2 Family Size Statements494.7 Dropout Rate From Kenyan Public Universities50CHAPTER FIVE53SUMMARY OF THE STUDY, CONCLUSIONS AND RECOMMENDATIONS565.1 Introduction565.2 Summary of the Study Findings565.3. Conclusions of the Study595.4 Recommendations.595.5 Recommendations for Further Research60REFERENCES61APPENDICES66APPENDIX 1: LETTER OF INTRODUCTION66APPENDIX 2: QUESTIONNAIRE67 LIST OF TABLES Table 3.1 Sampling Frame28 TOC h u z Table 4.1 Response Rate38Table 4.2 Gender38Table 4.3 Age39Table 4.4 Working Experience39Table 4.5 Marital Status40Table 4.6 Parents/Guardian Level of Education41Table 4.7 A crossectional table showing the relationship between parent education and drop-out from university41Table 4.8 A crossectional table showing the relationship between parent education and drop-out from university42Table 4.9 A crossectional table showing the relationship betwelades and resemble aircraft propellers in appearance. Low-solidity HAWTs have a low proportion of material within the swept area, which is compensated by a faster rotation speed used to fill up the swept area. Low-solidity HAWTs are the most commonly used commercial wind turbines as well as the type most often represented through media sources.

Those HAWTs offer the greatest efficiency in electricity generation and, therefore, are among the most cost-efficient designs used. Figure 3.3 Windmill used for pumping water in American West since 18th century 14. Figure 3.5 First off shore wind turbines in North Sea of America. A major concern of wind turbine siting relates to negative environmental impacts associated with noise, visual disturbance, and impacts on wildlife.

Two kinds of noise associated with turbines are mechanical noise, which is produced by its equipment such as its gearbox, and aerodynamic noise, which is produced from the movement of air over the blades. Mechanical noise may be dampened by altering mechanical components of turbines. Aerodynamic noise, often described as a “swishing” sound, is a factor of types of blades and speed of rotation. Wind turbine noise in decibels, however, has been found to be no louder than that experienced by traveling in a moving car and is often comparable to nighttime rural background noise. Other concerns involve flicker zones, where light may be reflected off the spinning blades, and pockets of electromagnetic interference that affect television and radio signals within close proximity to turbines.

Chapter No.4 Hardware Description The analysis is carried out on Horizontal Axis Wind Turbine (HAWT) meant for domestic purposes. Components of this turbine are mentioned below. 4.1 Blades The first part of our project is the blades of wind turbine. The blades are made up of Poly Vinyl Chloride (PVC). Six inches diameter PVC pipe is used to fabricate the appropriate wing-shaped curvature.

A jig saw is used to cut the PVC pipe. The final blade dimensions are shown in Figure 1. The leading edge is rounded and the trailing edge is tapered for each blade so that the shape would approach that of an airplane wing. We designed 3 blades of length 1.85 meters twisted at an angle of 150o.We used PVC pipe ( B type) for the designing of blades, because it has a resistive property to different chemical reactions, which increases its life time and the second thing is that it is durable. Figure 4.1 Blade design on Solid work software.

Figure 4.2 Blade designing process (Group members) Figure 4.3 Original blades (PVC) designed by group members. Figure 4.4 Polished three blades after manufacturing. These polished and clean blades were sprayed and then used for project Horizontal axis wind turbine. They were looking good after polishing. 4.2 Rotor Hub and Blades Attachment We made a hub from wood of about 1 feet in diameter for blades. The hub is light in weight and have the ability to hold the weight of blades attached with it.

It is important that the blades must be attached with the rotor or hub in specified angel 1200 otherwise the blades will not rotates on any wind speed which may cause imbalance in rotation and it can tear apart the blades from the hub. To ensure the blade symmetry, the tip-to-tip spacing is measured precisely before drilling the final attachment holes through the blade. Figure 4.5 Blades fixed in hub or Rotor 4.3 Nacelle The Nacelle is consist of two bearings, one shaft, one generator two sprockets and chain. The length of nacelle is 2 feet ( 24inches), its width is 1feet (12inches) and height is also 1 feet (12inch)We made nacelle from low weight steel sheets having a thickness of 0.5inch. Inside it we used aluminum frame for making supports for Barings.

We used steel road of 2 feet having a diameter of 20mm for making a shaft. Two bearings (UCP-204 20mm) are used which provides support to the shaft and also make it to move freely (decreases friction).Two sprockets are used one is connected with the shaft. Its diameter is 8inch and is known as driver sprocket. The second one is connected with the generator shaft of diameter 2inch and is known as driven sprocket. A 250W PMDC motor is used as a generator of model MY1025. Figure 4.6 Nacelle internal design on Solid work software.

4.4 Bearings UCP-204 20mm is used to hold the shaft. UCP204-20MM has a combination of a cast iron pillow block housing with an anti-rotation device with self-alignment and a set screw locking chrome steel insert bearing with a slinger seal design. This specific unit is a standard duty pillow block bearing with a wide inner ring and two set screws and a cast iron unit with the standard base to center height with a grease fitting. UCP200 Series Pillow Block Bearing is equipped with two specifically designed set screws that are positioned in the inner ring of the ball bearing to lock and attach to the shaft. Figure 4.7 UCP-204 bearing 4.5 Shaft We used steel road of 2 feet having a diameter of 20mm for making a shaft. The shaft was polished and clean from any kind of rust and then used in project.

Support for the shaft was provided by two bearings that we used (UCP-204). Shaft helps to connect the rotor to the generator. Main Shaft is made to pass through the tower using journal bearings for ensuring smooth rotation. They support the main shaft to rotate freely when blades rotate. Main Shaft is connected to the hub at one end and to the gear box at another end.

Figure 4.8 Shaft used in HAWT Figure 4.9 Bearings holding the shaf 4.6 Sprockets Two sprockets are used one is connected with the shaft. Its diameter is 8inch and is known as driver sprocket. The second one is connected with the generator shaft of diameter 2inch and is known as driven sprocket. The sprockets connect the shaft and generator with the help of chain. Due to less losses we used chain mechanism for our project.

Figure 4.10 Shows a detail view of chain mechanism. 4.7 Yaw Control Main Shaft is made to pass through the tower using journal bearings for ensuring smooth rotation. They support the main shaft to rotate freely when blades rotate. Main Shaft is connected to the hub at one end and to the gear box at another end.

Low gauge steel sheet is used for yaw mechanism. Yaw is attached with the nacelle with the help of iron light rods. Figure 4.11 shows the Yaw control of HAWT 4.8 Generator A 250W PMDC motor is used as a generator of model MY1025. Due to brush less feature, this motor is very good for generating power at low level. The table 4.1 shows the specification of motor. Features Values Voltage 24V Diameter 10.5cm Gear diameter 2.55cm Rated speed 2750 RPM Rated current 14A Output 250W Model MY1025 Number of wires Two wires ( Red and Black) Table 4.1 shows the values of motor. Figure 4.12 PMDC motor used for generation 4.9 Tower The tower provides support to the nacelle and it make the nacelle above the ground at a certain height. Or it is the supporting structure of nacelle. The tower is made from high steel and iron alloy. Its height is 7meter (22.96 feet) and the diameter is 4inches. At one end of tower a 2X2 feet steel base is welded in order to provide support to the tower. At the other end a holding piece is attached with is to be fit in the bearing attached to the lower end of nacelle for easy assembling and disassembling and for free motion with the wind direction. Figure 4.13 Tower and base view made of steel and iron Chapter No.5 Experimental Results Initial testing is done in the terrace of our university. Winds speeds vary day by day. Readings are taken by connecting the output of the dynamo with a multimeter with a purpose of measuring voltage. We took the readings on two consecutive days. The first day the average wind speed was found to be 0.98 m/s measured using initial testing is done in the terrace of our college campus. Winds speeds vary day by day. Readings are taken by connecting the output of the dynamo with a multimeter with a purpose of measuring voltage. We took the readings on two consecutive days. The first day the average wind speed was found to be 0.98 m/s measured using anemometer. On second day the wind speed was 1.5 m/s at university ground and 2.8 m/s at university car parking area. On third day the wind speed was 3.5 m/s at road near to university and on fourth day due rain and heavy wind it was 8 m/s at civil building as shown in Table 5.1. Wind speed Output current Output voltage Output Power m/s A V W 0.98 m/s 0.2A 3V 0.6W 1.5 m/s 1A 5V 6W 2.8 m/s 3A 10V 30W 3.5 m/s 4A 12V 48W 8 m/s 7A 15V 90W Table 5.1 shows the detail about different voltage and current on different wind speed. A voltmeter is connected in parallel and an ammeter is connected in series to measure voltage and current obtained from the wind turbine. Readings with smaller magnitude starting from zero in the voltmeter did not provide us a constant output. Hence we started noting the readings which withstands for a prolonged period of time. Figure 5.1 shows the output of generator. Figure 5.2 shows the wind speed vs power output graph. Hence it shows that when the wind the speed increases the RPM of generator will also increases, which will gives enough output power to charge a DC battery. The rated RPM of generator is 2750 at which the generator produces 250W easily if the wind speed is high. The output graph of voltage vs current is similar. As the voltage increases the current rating also increases as shown in figure 5.3. Figure 5.3 shows the output graph of voltage vs current. A voltmeter is connected in parallel and an ammeter is connected in series to measure voltage and current obtained from the wind turbine. Readings with smaller magnitude starting from zero in the voltmeter did not provide us a constant output. Hence we started noting the readings which withstands for a prolonged period of time. From the figure 5.3, it is observed that as the voltage increases current increases. Hence there exists proportionality between the current and voltage. Chapter No.6 Conclusion HAWT is a renewable source of energy. Wind energy can be utilize to produce Electrical energy by mean of HAWT. Now a days HAWT is used in many countries to make electrical energy without any fuel cost. Wind is free of cost so we can use it as much as we want to produce free electricity. Despite existing inefficiencies in the mechanics and measurement of small wind turbine systems, this project illustrates how sites with viable wind resources (average wind speed > 10 mph) can be economically feasible in urban environments. The proposed system prevents potential small wind turbine customers from over-predicting their local wind resource, thus saving time and labor. The wind energy is a rapidly expanding field. Extensive research activities are being conducted across the globe in this area, with the goal of improving the efficiency of wind turbines. Several configurations of wind turbines have been proposed and the modern megawatt horizontal axis wind turbines are at this juncture very efficient with the power coefficient up to 45 % to 50 %. In spite of all the efforts, as reported in chapter 1, the overall contribution of wind power in the global total electricity generation is still a small fraction. One of the main reasons for the low success rate of wind turbines is the high rated wind speed. The low wind speed small scale wind turbines (HAWTs) are generally ignored because of their poor performance that does not allow justifying their installation and operational cost. The aim of this thesis was to develop the wind energy harvesters that can operate near the ground level where wind speed is very low (< 5 m/s). Although the general momentum theory predicts the rotor performance, it fails to give any information about the rotor geometry. This deficiency requires the next discussion which is blade element theory. In the blade element theory, the equations required to find the torque and thrust force on the roResearch Design303.3 Location of the Study303.4 Target Population313.5 Sample Size313.5.1 Sampling Procedure323.6 Research Instruments323.6.1 Questionnaire323.7 Pilot Study343.7.1 Instrument Validity343.7.3 Instrument Reliability343.8 Data Collection Procedure343.9 Data Analysis Techniques353.10 Ethical Considerations35CHAPTER FOUR37DATA ANALYSIS, PRESENTATION AND INTERPRETATION374.1 Introduction374.2 Response Rate374.3 General Information on Respondents384.3.1 Gender384.4.2 Parents Level of Education Statements424.5. Influence of Parental Income on Student Dropout Rate424.5.1 Parents /Guardians Occupation444.5.2 Parents /Guardians Occupation Statements464.6 Influence of Family Size on Student Dropout Rate474.6.1 Number of Family Members494.6.2 Family Size Statements494.7 Dropout Rate From Kenyan Public Universities50CHAPTER FIVE53SUMMARY OF THE STUDY, CONCLUSIONS AND RECOMMENDATIONS565.1 Introduction565.2 Summary of the Study Findings565.3. Conclusions of the Study595.4 Recommendations.595.5 Recommendations for Further Research60REFERENCES61APPENDICES66APPENDIX 1: LETTER OF INTRODUCTION66APPENDIX 2: QUESTIONNAIRE67 LIST OF TABLES Table 3.1 Sampling Frame28 TOC h u z Table 4.1 Response Rate38Table 4.2 Gender38Table 4.3 Age39Table 4.4 Working Experience39Table 4.5 Marital Status40Table 4.6 Parents/Guardian Level of Education41Table 4.7 A crossectional table showing the relationship between parent education and drop-out from university41Table 4.8 A crossectional table showing the relationship between parent education and drop-out from university42Table 4.9 A crossectional table showing the relationship betwetor were found in terms of blade geometry parameters. The results of this theory provide to make relations between the rotor performance and rotor geometry. The ultimate goal was to relate the results of general momentum theory and blade element theory in order to get the enough equations for HAWT blade design. This was achieved in the discussion of blade element-momentum theory (BEM). After the equations resulted from this theory were obtained, a tip correction method was applied to the theory. In this study, linearized tip correction method was used to take the effect of number of blades into account. This method uses Prandtl’s tip correction factor which is related to the reduction of the circulation around a rotor blade. Blade design was performed beginning with the optimization of blade geometry aerodynamically. Aerodynamic optimization for a wind turbine means to design a blade geometry which gives the maximum power output. For the optimization, it was graphically shown that the effect of airfoil characteristics (glide ratio) and the tip-loss effect were negligible on rotor performance. So the unique relationship was found between the relative wind angle and local tip-speed ratio for the determination of optimum condition for each blade element. For a chosen blade profile and a tip-speed ratio, the setting angle and chord-length variation along the blade length were then calculated together with the power coefficients. The calculations shows that power coefficient increases with increasing design lift coefficient and decreasing drag coefficient of blade profile. This means that the development in profile data is needed for better optimization. Designed blade has a non-linear twist and taper and more importantly even though it had high power coefficient, it was highly loaded. Therefore, in this study, the blade geometry was simplified and performance of modified blade was examined. At first, the strongly non-linear taper was replaced with a linear taper. Among the modified blades whose surfaces are equal to the designed blade’s ones, the one which has the highest power output was chosen. Then the large blade twist was replaced with a linear blade setting angle distribution. Under these conditions, it was seen that the new modified blade reduced power output approximately 10% of the power output of the designed blade. This means that in order to extract the same amount of power with the designed blade, the blade span must be expanded approximately 5%. Structural design of HAWT blades is as important as their aerodynamic design. The dynamic structural loads which a rotor will experience play the major role in determining the lifetime of the rotor. Obviously, aerodynamic loads are a major source of loading and must be well understood before the structural response can be accurately determined and also the blade geometry parameters are required for dynamic load analysis of wind turbine rotors. So such a study on the dynamic load analysis of HAWT blades might also use the outputs. Future Work On the methodology front, future improvements of the developed design framework include that we can work on design of blades and CDF performance of blades to improve the output and working of turbine at low wind speed in any area. Implementation of hydraulic break system to stop the rotor when it is stormy weather or heavy rain fall. Another planned extension of the current design system encompasses the integration of a module for the tower structural analysis and design. This will allow one to extend the design search by including turbine rated power and rotor diameter as design variables. Also we can implement other theories like BEM. HAWT’s currently does not have any mechanical or electrical breaking mechanism that can restrict its operation at very high wind speeds. Before deploying the wind turbine in a real environment, it must be equipped with a safety feature which can protect it when wind speed it very high. Lastly, the voltage output from the wind turbine is dependent on the wind speed. Also, there exists an optimal external load where power output by the wind turbine is highest at a given wind speed. In order to charge an electronic device using this wind turbine, it needs to produce constant voltage. Also, the wind turbine should operate most of the time at its optimal load where power output is maximum. Therefore, an electronic circuit is needed that will track the maximum power point at every wind speed and produce constant voltage output required to charge sensor nodes. References 1 Gasch R, Twele J. Wind power plants – fundamentals, design, construction and operation: Springer, 2012. 2 WIND AND WATER POWER PROGRAM. U.S. Department of Energy: Energy Efficiency and Renewable energy; 2011. 3 P. Brondsted. Introduction. In P. Brondsted and R. P. L. Nijssen, editors, Advances in wind turbine blade design and materials, volume 47 of Energy. Woodhead Publishing Limited, 2013. 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