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

犹他州大学Mathieu Francoeur，CBET 1253577，美国每年大约58%的能源消耗在热量上。通过热光伏发电机直接将热能转换为电能，可以在燃烧室、光伏电池和个人计算机等各种系统中回收大量废热。传统的热光伏系统受到黑体光谱的限制。通过一个纳米尺寸的缝隙将热源和将热能转化为电能的电池分开，辐射热传输超过了黑体预测的几个数量级，这是由于消逝波的能量传输。因此，通过瞬逝波隧穿增强能量传递可以显著增加热光伏发电。这项研究将在实验上证明，与传统的热光伏系统相比，纳米级间隙热光伏(Nano-TPV)器件的发电能力可以提高20到30倍。这将通过测量辐射热流和纳米TPV的电能输出和转换效率来实现，该设备包括由20 nm的间隙隔开的平面。纳米尺寸的间隙将通过弹簧状的间隔物保持。在表面之间施加静电力，结合知道垫片的弹簧常量，将允许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的间隙分隔的平面之间的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是缝隙厚度，分别针对支持共振表面波的光学厚和薄材料预测。这项研究将首次提供在纳米尺寸间隙下的定量实验纳米TPV性能分析。将通过测试辐射器的各种材料来考虑光谱效应，例如在近红外波段支撑表面等离子激元的氧化铟锡材料。纳米TPV的性能将被系统地量化为间隙厚度以及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。该项目还将详细分析晶格和自由载流子吸收以及电子-空穴对的热化和非辐射复合对电池内热量散失的影响。该项目将通过测量由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的性能来增强基于逝去波的能量转换的基础知识。这项研究是朝着建立微型废热回收设备迈出的重要一步，这种设备可以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，课程内容将免费提供给公众。K-12外展将通过犹他州科学奥林匹克竞赛进行。学院奖学金和研究奖学金将提供给参加本次活动的高中生。通过将在犹他州科学奥林匹克竞赛和高中展示的交互式便携式演示套件的概念，将促进直接热能到电能的转换。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.