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University of Nevada, Reno Electromagnetic Energy Harvesting in Pursuit of Heat Radiation

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University of Nevada, Reno Electromagnetic Energy Harvesting in Pursuit of Heat Radiation University of Nevada, Reno Electromagnetic Energy Harvesting In Pursuit of Heat Radiation A dissertation submitted in partial fulfillment of the Requirements for the degree of Doctor of Philosophy in Electrical Engineering By Richard A. Bean Dr. Banmali S. Rawat, Ph. D., Dissertation Advisor May, 2019 Copyright by Richard A. Bean 2019 All Rights Reserved THE GRADUATE SCHOOL We recommend that the dissertation Prepared under our supervision by Richard A. Bean entitled Electromagnetic Energy Harvesting in Pursuit of Heat Radiation be accepted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Banmali S. Rawat, Ph. D., Advisor Bruno S. Bauer, Ph. D., Committee Member Yantao Shen, Ph. D., Committee Member Jihwan Yoon, Ph. D., Committee Member David M. Leitner, Ph. D., Graduate School Representative David W. Zeh, Ph. D., Dean, Graduate School May, 2019 i Abstract This dissertation explores the potential harvesting of electrical energy from heat radiation. Heat is an abundant form of energy that occurs naturally. It is spontaneously emitted from the matter in a material surface, and its random photonic emissions aggregate. It is transferred from material surfaces to other material surfaces in the form of heat radiation. This heat radiation transfers through free space in the form of plane waves. These plane waves are electromagnetic in character and are fully described by Maxwell’s equations. Electromagnetic (EM) plane waves are routinely utilized in communication, radar, and optical systems. This dissertation posits that heat radiation can be captured by antennas, conducted by coax cables, and then converted to hybrid TE-TM waves inside microstrip printed circuit boards. These EM waves can be subsequently rectified using electronic devices known as Schottky diodes. The resultant direct current (DC) can be stored and used to power electronic devices and electrical machinery. This dissertation analyzes the theoretical foundations of heat radiation. Using Planck’s Law, the likely power magnitudes from material surfaces are predicted. Passive antennas, geometrical relationships, and bandwidth aggregation can concentrate these power magnitudes. Using these passive gains, effective rectification can be achieved. Complementing this mathematical and logical analysis, physical measurements of power were made for multiple antennas types, for different temperatures, and for different ii distances from the material surfaces. Multiple power meters and measurement applications were used. To confirm the feasibility of harvesting electrical energy from heat radiation multiple rectifier and rectenna designs and circuits were designed, fabricated, and tested. Prevailing views of energy aggregation were adopted and then compared with the actual performance in the electronic circuits. Finally, the applied research in this dissertation has successfully generated DC electricity by harvesting ambient radiation using electrical engineering technology and techniques. Because photons of heat radiation are indistinguishable from the photons from other sources in the microwave frequency range, this dissertation logically examines the potential sources removing the increasingly improbable sources such that heat radiation remains a likely source. Further, the harvesting technology was tested in an anechoic chamber where the manmade radiation sources from outside the chamber were greatly reduced by metallic shielding and signal absorbing materials. iii Acknowledgements Every endeavor is the product of numerous contributors. These contributions include ideas, coursework, discussions, encouragement, and frameworks for analysis. I wish to acknowledge the assistance I have received and to express my gratitude for the help. I gratefully acknowledge the continued support and guidance of my advisor, Dr. Banmali S. Rawat. His weekly participation in my progress has provided a forum for discussions, and his feedback has guided my investigations. He provided the coursework foundations in electromagnetic waves, microwaves, and optical communications. These foundations and support were instrumental in harvesting the noise energy that is often treated as a detriment to electrical engineering. I also acknowledge Dr. Indira Chatterjee whose courses in distributed systems and antennas theory figured prominently in my dissertation research. My original exposure to rectennas was through her courses. Dr. Miles Greiner’s course in radiative heat transfer provided my first recognition that heat radiation might produce enough power to be harvested. Dr. David Leitner’s course in Quantum Mechanics reinforced the role of spontaneous emissions and reaffirmed the recognition that heat photons were the same as plane waves in the radio frequency through visible light wave-lengths. Finally, I would like to recognize the support of my wife and family who have been partners in my dissertation research. iv TABLE OF CONTENTS Abstract ................................................................................................................................. i Acknowledgements ............................................................................................................. iii Table of Contents ................................................................................................................ iv Table of Tables ..................................................................................................................... x Table of Figures ................................................................................................................... xi 1 Introduction ................................................................................................................ 1 1.1 A Conceptual Design for A Simple Electrical Generator ...................................... 2 1.2 Heat: An Abundant Energy Source ...................................................................... 4 1.3 Why Use Heat Radiation? .................................................................................... 5 1.4 Research in Support of This Conceptual Design .................................................. 6 1.5 Antennas as Electromagnetic Energy Harvesters ................................................ 9 1.6 Rectification.......................................................................................................... 9 1.7 The Need for Engineering Gain .......................................................................... 10 1.8 Heat Radiation in Theory.................................................................................... 11 1.9 Stefan-Boltzmann Equation ............................................................................... 13 1.10 Storage of Heat Energy ................................................................................... 16 v 1.11 Planck’s Law: Frequency Spectrum of Thermal Radiation ............................ 18 1.12 “kbTB” Noise Equation .................................................................................... 26 1.13 Disparate Power Predictions .......................................................................... 27 1.14 Early Power Measurements ........................................................................... 29 1.15 Conclusions from Heat Theory, Literature, and Early Measurements ........... 31 2 Engineering Gains Useful to Harvesting Heat Radiation .......................................... 33 2.1 Conservation of energy and Engineering Gains ................................................. 33 2.2 Antennas ............................................................................................................ 34 2.3 Emitting Area ...................................................................................................... 39 2.4 Heat Geometries ................................................................................................ 39 2.5 Predictive Equations for Power .......................................................................... 43 2.6 Reflections .......................................................................................................... 45 2.7 Impedance Matching ......................................................................................... 47 2.8 Bandwidth Aggregation ...................................................................................... 49 2.9 Potential Gains from Convolution ...................................................................... 51 2.10 Other Gain Techniques ................................................................................... 55 2.11 Predictive Engineering .................................................................................... 56 2.11.1 Radiance Predictions ................................................................................... 58 vi 2.11.2 FRIIS Predictions .......................................................................................... 59 2.11.3 Heat View Predictions ................................................................................. 60 2.11.4 Summary of Radiometry, FRIIS, and Heat View Approaches ..................... 61 2.11.5 Measurement and Known Factor Approach............................................... 62 2.11.6 Summary of Predictive Engineering ............................................................ 66 3 Power Measurements of Heat Radiation ................................................................. 68 3.1 Measurement Chronology ................................................................................
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