A rapid development of Wireless Power Transfer technology has been observed during the last decades. After Wi-Fi has become widely accepted, researchers and scientists now attempt to remove the last cable also in the area of energy transfer for certain applications. A typical application of WPT is Space-Based Solar Power (SBSP) harvesting. The concept of collecting solar power in space for use on Earth, which is one of the most promising power generation options which contribute to meeting global energy demands in the 21st century, calls for collecting solar energy in space across the entire wavelength of the spectrum. But before that energy can be supplied at DC to the users on earth or on other artificial aircrafts, three major energy-conversion steps are needed, 1) solar to DC, 2) DC to microwave at the microwave generators of the spacecraft's radiation system, 3) Microwave to DC at the rectenna rectifiers on earth or on other artificial aircrafts.In the current proposed SBSP, the rectenna (rectifier + antenna) is only involved in the third step to convert microwave to DC. The idea of using nano/optical rectennas (nano antenna or nantenna + rectifier) to harvest solar energy has been suggested in 1972. In recent years, this concept is re-called by scientists and researchers due to the rapid nano technology development. It is claimed that the efficiency of this type of topology may be much larger, even up to 90% for a single wavelength. This is much higher than the maximum efficiency (44%) of photovoltaic cells in a laboratory.The main objective of this thesis is to investigate the antenna as component in the Rectenna, both in the microwave and optical frequency bands. Both rectennas in such a system, one converting sunlight into DC power, and one working at microwave frequencies, after transferring the microwave power from the power satellite to earth, can be considered as the core components for any SBSP.For the microwave part, the target is to offer antenna designs that are superior to existing solutions. Thereto, the antenna design effort is mainly focusing on reducing the area for a certain bandwidth and gain, or in other words, to achieve the highest aperture efficiencies for a required bandwidth.For the optical part, the target is to investigate the radiation efficiencies and the matching conditions to the rectifier circuit that can be realistically reached in the conversion from sunlight to DC. In contrast to the situation at microwave frequencies, here the choice of the metal used to fabricate the antenna will prove to be crucial, due to the strong dispersive properties of metals.FOREWORD II CONTENTS IV ABSTRACT VIII SAMENVATTING X LIST OF ACRONYMS XII LIST OF SYMBOLS XIV CHAPTER 1 INTRODUCTION 1 1.1. WIRELESS POWER TRANSFER BASED ON THE RECTENNA APPROACH 1 1.2. NANO/OPTICAL RECTENNA FOR SOLAR ENERGY HARVESTING 2 1.3. SATELLITE SOLAR POWER SYSTEM (SSPS) 3 1.4. OBJECTIVES AND CONTENTS OF THE THESIS 4 CHAPTER 2 DESIGN FRAMEWORK 7 2.1. INTRODUCTION 7 2.2. FULL-WAVE EM SOLVERS 7 2.3. THE CHOICE OF THE DESIGN TOOL 11 2.4. OPTIMIZATION: GA AND PSO- UNDERLYING CONCEPTS 11 2.5. OPTIMIZATION FRAMEWORK 15 CHAPTER 3 OPTIMAL DESIGN OF A HIGHLY COMPACT WIDEBAND ARRAY 17 3.1. INTRODUCTION 17 3.2. THE DESIGN PROCESS 18 3.3. OPTIMIZATION 20 3.4. RESULTS 22 3.5. CONCLUSION 25 CHAPTER 4 HIGH APERTURE EFFICIENCY WIDEBAND MICROSTRIP ARRAYS FOR WPT/WLAN 27 4.1. INTRODUCTION 27 4.2. WIDEBAND THREE ELEMENT ARRAY 29 4.3. APERTURE EFFICIENCY ENHANCEMENT BY MINIMIZING THE AREA 37 4.4. STUDY OF THE THICKNESS OF AIR LAYER ON THE PERFORMANCE OF THE PROPOSED ARRAY 40 4.5. PSO OPTIMIZATION FRAMEWORK 42 4.6. ANTENNA DIVERSITY VERSUS PSO CONVERGENCE SPEED 44 4.7. APERTURE EFFICIENCY ENHANCEMENT BY INCREASING BROADSIDE GAIN 46 4.8. CONCLUSION 47 CHAPTER 5 COMPARISON OF WEIGHTED SUM FITNESS FUNCTIONS FOR PSO OPTIMIZATION OF WIDEBAND MEDIUM-GAIN ANTENNAS 49 5.1. INTRODUCTION 49 5.2. TESTED FITNESS FUNCTIONS AND PSO OPTIMIZER 51 5.3. 3-ELEMENT PLANAR ARRAY 54 5.4. 4-ELEMENT LINEAR ARRAY 58 5.5. CONCLUSION 61 CHAPTER 6 SYSTEMATIC FULL-WAVE CHARACTERIZATION OF REALISTIC METALLIC NANO DIPOLE ANTENNAS 63 6.1. INTRODUCTION 63 6.2. CHOICE OF METAL 64 6.3. DIPOLE MODEL 65 6.4. SOLVERS AND EXCITATION 66 6.5. RESULTS 70 6.6. CONCLUSION 78 CHAPTER 7 UPPER BOUNDS FOR THE SOLAR ENERGY HARVESTING EFFICIENCY OF NANO-ANTENNAS 79 7.1. INTRODUCTION 79 7.2. FROM INCIDENT WAVE TO RECEIVED POWER 81 7.3. EFFICIENCIES IN VACUUM 84 7.4. EFFICIENCIES ON A SUBSTRATE LAYER 87 7.5. EXTRACTION OF THE EFFECT OF THE MATERIAL PROPERTIES 89 7.6. CONCLUSION 91 CHAPTER 8 OPTIMAL SOLAR ENERGY HARVESTING EFFICIENCY OF NANO-RECTENNA SYSTEMS 93 8.1. INTRODUCTION 93 8.2. RECTENNA MODEL FOR SOLAR ENERGY HARVESTING 95 8.3. RESULTS 98 8.4. MAXIMUM DELIVERED POWER PER DIPOLE 107 8.5. CONCLUSION 108 CHAPTER 9 GENERAL CONCLUSIONS 109 9.1. CONCLUSION 109 9.2. FURTHER RESEARCH 111 BIBLIOGRAPHY 113 LIST OF PUBLICATIONS 119nrpages: 120status: publishe
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