Thermophotovoltaics : shaping the flow of thermal radiation

Abstract

This thesis explores the modeling, design, and optimization of photonic crystals as spectral control components for high-performance thermophotovoltaic (TPV) power conversion. In particular, we focus on the use of one-dimensional and two dimensional photonic crystals as optical filters and selective thermal emitters for thermophotovoltaic and micro-thermophotovoltaic (micro-TPV)) applications. In addition, we explore fundamental limitations of photonic crystal thermal emitters and provide new insights into the limiting power transfer mechanisms that are relevant for TPV, micro-TPV, lighting and sensor applications. Ideal thermodynamic models that capture dominant power transfer mechanism for TPV and micro-TPV case, are developed and used for the design, optimization and system performance estimation of TPV systems with photonic-crystals. Furthermore, we propose for the first time two new classes of narrow-band thermal emitters that use the resonant cavity effect. The first type of narrow-band thermal emitters rely on vertical-cavity to enhance the thermal emission of highly reflective materials (e.g metals). This class of emitters was named the vertical cavity enhanced resonant thermal emitter (VERTE).

(cont.) The second type of resonant thermal emitters rely on guided resonances in a two-dimensional photonic crystal slab to enhance the emittance of a high-dielectric low-absorption material (e.g. silicon). Both types of resonant thermal emission sources are quasi-monochromatic, and partially-coherent thermal sources that hold great promise for applications ranging from highly-efficient TPV systems to near-IR and IR sensors. Finally, experimentally measured spectral characteristics of fabricated one-dimensional and two-dimensional photonic-crystals show excellent correlation with simulation results. It was shown that a TPV system comprising of the proposed front-side filter and selective thermal emitter exhibits a three-fold enhancement in efficiency over the conventional TPV systems.