CAREER: Enhanced Power Generation in a Nanoscale-Gap Thermophotovoltaic Device due to Radiative Heat Transfer Exceeding the Blackbody Limit

马修·弗朗索瓦，犹他大学美国每年消耗的能源中约有58%转化为热能。通过热光伏发电机直接将热能转换为电能，可以在燃烧室、光伏电池和个人电脑等各种系统中对大量废热进行回收利用。传统的热光伏系统受到黑体光谱的限制。通过将热源和电池通过纳米大小的间隙分离，将热量转化为电能，由于能量通过倏逝波传输，辐射传热比黑体预测高出几个数量级。因此，通过倏逝波隧穿增强能量传递可以导致热光伏发电的显着增加。这项研究将通过实验证明，与传统的热光伏系统相比，纳米级间隙热光伏（nano-TPV）装置的发电量可以提高20到30倍。这将通过测量辐射热通量和纳米tpv电功率输出和转换效率来完成，该设备涉及由小至20nm的间隙分隔的平面。纳米级的间隙将通过弹簧状的间隔来保持。在表面之间施加静电力，结合垫片弹簧常数的知识，可以精确控制和测量间隙厚度。这项研究将首次提供由纳米尺寸间隙分隔的平面之间良好控制的辐射通量测量。这将允许验证d-2和d-3近场热辐射制度，其中d是间隙厚度，分别预测光学厚和薄材料支持共振表面波。该研究将提供第一个在纳米尺寸间隙下的定量实验纳米- tpv性能分析。光谱效应将通过测试各种材料来考虑，例如在近红外波段支持表面等离子体极化的氧化铟锡。纳米tpv性能将被系统地量化为间隙厚度和散热器和电池温度的函数，并将与基于耦合近场热辐射、电荷和热传输模型的预测进行比较。晶格和自由载流子吸收、热化和电子-空穴对的非辐射复合对电池内散热的影响也将进行详细的分析。该项目将通过测量以亚波长间隙间隔的表面之间的通量来增强近场热辐射的基础知识，并通过实验分析纳米tpv性能来增强基于倏逝波的能量转换。这项研究是朝着建立微型废热回收装置迈出的重要一步，该装置可用于个人电脑和从人体收集热量的系统。该项目还将通过让高中生、本科生和研究生参与这些活动来促进培训和学习。近场热辐射的基础知识及其在发电中的应用将通过犹他大学为本科生和研究生开设的一门新的选修课来传播，课程内容将免费向公众开放。K-12外展将通过犹他州科学奥林匹克竞赛进行。参加本次活动的高中学生将获得部门奖学金和研究奖学金。直接的热能到电能的转换将通过一个交互式的、便携的演示套件的概念来促进，该演示套件将在犹他州科学奥林匹克竞赛和高中中展示。这些活动将有助于工程学院招收高质量的理工科学生。

CBET 1253577Mathieu Francoeur, University of Utah Approximately 58% of the energy consumed annually in the US is lost to heat. Direct thermal-to-electrical energy conversion via thermophotovoltaic power generators can contribute significantly to recycling this large amount of waste heat in various systems such as combustion chambers, photovoltaic cells and personal computers. Conventional thermophotovoltaic systems are limited by the blackbody spectrum. By separating the heat source and the cells converting heat into electricity by a nanosize gap, radiation heat transfer exceeds the blackbody predictions by a few orders of magnitude due to energy transport by evanescent waves. Enhanced energy transfer by evanescent wave tunneling can thus lead to a significant increase of thermophotovoltaic power generation. This research will demonstrate experimentally that power generation in a nanoscale-gap thermophotovoltaic (nano-TPV) device can be enhanced by a factor of 20 to 30 compared to conventional thermophotovoltaic systems. This will be accomplished by measuring radiative heat flux and nano-TPV electrical power output and conversion efficiency in a device involving planar surfaces separated by a gap as small as 20 nm. The nanosize gap will be maintained via spring-like spacers. The application of an electrostatic force between the surfaces combined with the knowledge of the spring constant of the spacers will allow precise control and measurement of the gap thickness. This research will provide for the first time well-controlled radiative flux measurements between planar surfaces separated by a nanosize gap. This will allow the verification of the d-2 and d-3 near-field thermal radiation regimes, where d is the gap thickness, predicted respectively for optically thick and thin materials supporting resonant surface waves. The research will provide the first quantitative experimental nano-TPV performance analysis at nanosize gaps. The spectral effects will be considered by testing various materials for the radiator, such as indium tin oxide supporting surface plasmon-polaritons in the near infrared band. Nano-TPV performances will be systematically quantified as a function of the gap thickness and the temperatures of the radiator and the cells, and will be compared against predictions based on a coupled near-field thermal radiation, charge and heat transport model. The impacts of heat dissipation within the cells due to lattice and free carrier absorption, thermalization and non-radiative recombination of electron-hole pairs will also be analyzed in great detail.This project will enhance fundamental knowledge in near-field thermal radiation by measuring fluxes between surfaces spaced by sub-wavelength gaps and in evanescent wave-based energy conversion by experimentally analyzing nano-TPV performances. The research is an important step toward the establishment of miniature waste heat recovery devices that could be used in personal computers and systems harvesting heat from the human body. The project will also promote training and learning through the involvement of high school, undergraduate and graduate students in the activities. Fundamentals of near-field thermal radiation and its application to power generation will be disseminated via the development of a new elective course at the University of Utah dedicated to both undergraduate and graduate students, where the class content will be made freely available to the general public. K-12 outreach will be performed via the Utah Science Olympiad. Departmental scholarships and research fellowships will be offered to high school students participating in this event. Direct thermal-to-electrical energy conversion will be promoted via the conception of an interactive, portable demo-kit that will be presented at the Utah Science Olympiad and in high schools. These activities will assist the efforts of the College of Engineering in recruiting high quality students in science and engineering programs.