Portable Solar Tracker
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GROUP 1 Portable Solar Tracker Senior Design II Tri Bui, Tuyen Bui, Christopher Davis, Stephen Holman Summer 2010 Table of Contents 1 Introduction 1.1 Executive Summary 1 1.2 Motivation 2 1.3 Goals 2 1.4 Specifications 3 1.5 Budget Projection 3 1.6 Milestone Chart 4 1.6.1 May Milestones 4 1.6.2 June Milestones 5 1.6.3 July Milestones 6 2 Background and Research 8 2.1 Previous Works 8 2.2 Solar Panels 11 2.2.1 Solar Radiation 11 2.2.1.a Effects of Sun Light on Exposed Surfaces 12 2.2.2 Photovoltaic Cells 12 2.2.2.a Crystalline Silicon 15 2.2.2.b Monocrystalline Silicon 15 2.2.2.c Polycrystalline Silicon 16 2.2.2.d Thin Film Silicon 16 2.2.2.e CZTS 17 2.2.2.f Organic Solar Cells 17 2.2.2.g Solar Panel Summary 17 2.2.2.h Temperature 18 2.3 Batteries 19 2.3.1 Nickel-Cadmium 20 2.3.2 Sealed Lead 23 2.3.3 Lithium-ion 26 2.3.4 Nickel-Metal Hydride 27 2.3.5 Battery Monitoring and Management 28 2.4 Outputs 34 2.4.1 DC/AC Inverter 34 2.4.2 12V Car Charger Outlet 36 2.4.3 USB Charger 36 2.5 Microcontrollers 38 2.6 Motors 42 2.6.1 Servo Motors 42 2.6.1.a Continuous Rotation 43 2.6.1.b Fixed Rotation 44 2.6.2 DC Motors 45 2.6.2.a Brushed and Brushless Motors 46 2.6.3 DC Motor Controllers 47 2.7 Gyroscopes 48 2.8 Compass 51 ii 2.9 Photoresistors 53 2.10 LCD Module 55 2.11 Optics 58 2.11.1 Mirrors 58 2.11.2 Lenses 64 2.11.2.a Fresnel Lenses 66 2.11.3 Mirrors and Lenses 67 2.12 Mechanical Systems 68 2.12.1 Solar Panel Structure 68 2.12.2 Cooling System 68 2.12.3 Frame 70 2.12.3.a Pole Axis 70 2.12.3.b Horizontal Axis 71 2.12.3.c Mirror Frame 71 2.12.3.d Parabolic Mirror Frame 72 2.12.3.e Parabolic Lens Frame 72 3 Design 73 3.1 Selection of Components 73 3.1.1 Rationale for Component Selection 73 3.1.1.a Solar Panel 74 3.1.1.b Battery 75 3.1.1.c LCD Module 75 3.1.1.d Motor 76 3.1.1.e Gyroscope 76 3.1.1.f Compass 77 3.1.1.g Optics Configuration 77 3.1.2 Alternative Component Selection 79 3.1.2.a Alternative Solar Panel 80 3.1.2.b Alternative Battery 80 3.1.2.c Alternative Motor 82 3.1.2.d Alternative Gyroscope 82 3.1.2.e Alternative Compass 82 3.1.2.f Alternative Optics Configuration 83 3.2 Overall Design 83 3.2.1 Programming Design 85 3.2.1.a Pseudo Code 88 3.2.2 Methods of Tracking 90 3.2.2.a Predetermine Position 90 3.2.2.b Differentiating Photoresistors 91 3.2.2.c Differentiating Phototransistors 93 3.2.2.d Infrared Camera 95 3.2.3 Photoresistor Circuit 96 3.2.4 Full Circuit Design 99 4 Prototype and Testing 101 4.1 Preparation 101 4.2 Breadboard Construction 102 iii 4.2.1 Interfacing Components 103 4.2.2 Placement of Components 107 4.2.3 Sizes 108 4.3 Implementation Strategies 108 4.4 Safety with the Device 109 4.5 Testing 111 4.5.1 Efficiency Testing 112 4.5.2 Autonomous Testing 112 4.5.3 Photoresistors Experiment 112 4.5.4 Optical Optimization 113 4.5.5 Energy Storage Testing 115 4.5.6 Cooling System Testing 116 4.5.7 Water Resistance Test 117 4.5.8 Wind/Structural Integrity Test 117 4.6 Troubleshooting Procedures 118 4.6.1 Circuit Board Troubleshooting 118 4.7 Vendors 119 4.7.1 Pricing 119 5 Design Summary 120 6 Project Summary 122 7 Updated Design Summary 123 Appendix A: Works Cited 124 Appendix B: Permission 127 iv 1 Introduction The synopsis, goals, specifications, and initial planning will be introduced in this section. 1.1 Executive Summary Harnessing the energy of the sun has been an ongoing human endeavor from the dawn of agriculture to the modern age of silicon fabrication. In recent years there has been a great deal of interest involving the breakdown and storage of solar energy to provide power and heat to any given structure or device. This interest has manifested itself into new technologies and methods of approach that are constantly being developed to solve the problem of a world dependent on non-renewable energy sources that are gradually being depleted. The problem with photovoltaic solar panels and collectors that have been developed in the past is their efficiency, with ten-percent being generally accepted as a “good” efficiency. Looking at that figure it would seem like there is a lot of room for improvement. This project is an attempt to join the throngs of engineers and scientists in the development and progression of this discipline by constructing a maximally optimized solar energy capture and storage device that can sustain on its own power as well as power an external electronic device. The principal challenge of this project will be in the optimization of the device. An optical collector, that is yet to be precisely determined due to no tests having been conducted thus far, will be used to concentrate the most area of sunlight onto a smaller solar panel, so save the cost of a wide solar panel array. This optical collector will be mounted on a mechanical device that uses electronic sensors to follow the path of the sun and keep the photovoltaic panel perpendicular to the sun’s rays. This orientation of the panel has been shown to provide the highest possible level of output given the conditions of that specific day. Power must also be minimized within the system. All of the voltage requirements must be met for the components that make up the solar tracking device but current needs to be at its lowest possible but still functional level for all of it except the output to the external electronic device to be charged; this will be a challenging undertaking. Another important factor that will need to be examined is value versus cost, for instance if an expensive battery can be purchased to store a lot of energy and make the device a little more useful in that it charges faster, what is its value to the overall design in light of its cost? Questions like this will be closely studied; the more questioning and investigation that arises, the greater the success of the optimization of this device is likely to be. An optimization project would seem to be a perpetual project, and in a way it is. The project team has a multitude of aspects to work on and analyze, but the principal criteria for this device to be considered successful will be for it to automatically track the path of the sun, store the energy collected through photovoltaic cells to a battery that discharges to an external electronic device, monitor this stored energy and display the analyzed results in a user-friendly format on a digital screen. Other features such as a digital compass and a thermometer may be added to the device and their results will be 1 displayed on this same screen. Overall, the project will be very challenging, but any new breakthroughs or even understanding concerning this discipline will be considered a great achievement. 1.2 Motivation After hundreds of years of burning fossil fuels, a large “carbon footprint” has been left on the environment, and many government organizations, private organizations, even individuals are beginning to look toward clean, renewable sources of energy to liberate them from the tyranny of those traditional carbonaceous and non-renewable sources that have dominated in the past. With growing concerns for issues such as global warming and ozone layer depletion, there has never been more urgency for the development of these “green” technologies. It is the desire to be a part of this green, earth-shaping revolution that drives this project. The time for change is now; the human race can tarry no longer. There are several types of renewable energy sources that are currently being vigorously studied and implemented into a multitude of settings, these include wind, hydro-electric, and solar energy, among others. While the two former sources are mostly built on a large scale, while the latter, solar energy, is a source that can be practically built on the top of a building or in someone’s backyard. Solar energy is a field that is on the rise and will likely become integrated into more and more aspects of everyday life as the years progress. It is a safe bet that solar energy will remain a relevant field for at least the next 50 years and for career-seeking college graduates, that is an important detail to consider. Solar energy is of great interest to many groups and individuals around the globe but it is very important to sun-rich areas like Florida, with its reputation shining through in its nickname, “The Sunshine State”. Several politicians have come to Florida specifically to motivate people to want more solar energy collectors in their state, and the people that listen are generally very receptive.