Refractory All-Ceramic Thermal Emitter for High-Temperature Near-Field Thermophotovoltaics

Fangqi Chen,Xiaojie Liu,Yi Zheng,Jon Goldsby,Yanpei Tian

doi:10.3390/en15051830

Abstract

Thermophotovoltaics is a promising technology for heat recovery and has garnered tremendous attention in the last decades. This work theoretically evaluates the performance of a thermophotovoltaic system equipped with refractory all-ceramic selective thermal emitters made of boron carbide, silicon carbide and beryllium oxide for a high working temperature of 2000 ∘C, which corresponds to the external quantum efficiency of a SiC/Si tandem cell. The influence of thickness and filling ratio on the emissivity of thermal emitters over the wavelength ranging from 0.2 μm to 2.5 μm is studied. The corresponding spectral heat flux and output power are analyzed as well. For a specific configuration, the parameters for the thermophotovoltaic system are obtained, including short circuit current, open circuit voltage, fill factor, total heat flux, output power and conversion efficiency. The proposed all-ceramic thermal emitter ensures the robustness in the high-temperature working condition due to its thermal stability. The tuning of emissivity is achieved and analyzed based on distinct emitter nanostructures, and the further influence on the thermophotovoltaic system performance is deeply explored. This work sheds light on research of high-temperature thermal management and power generation.

Highlights

Nowadays, abundant waste heat is released into the environment by increasing anthropogenic activities without a deliberate plan, leaving climate issues like urban heat islands and global warming more severe
The emission spectrum should match the bandgap of the TPV cell, and the lowenergy photons need to be eliminated as far as possible to avoid thermal leakage, which has a negative effect on the conversion efficiency of the system [2]
To evaluate the conversion efficiency of a TPV cell more precisely, a parameter called quantum efficiency is defined as the ratio of the collected carriers to the incident photons, and it indicates the amount of current generated for a given incident photon wavelength

Summary

Introduction

Abundant waste heat is released into the environment by increasing anthropogenic activities without a deliberate plan, leaving climate issues like urban heat islands and global warming more severe. A selective thermal emitter transmits electromagnetic energy by tuning heat from sources into an emission spectrum according to the bandgap of the cell [5]. The emission spectrum should match the bandgap of the TPV cell, and the lowenergy photons need to be eliminated as far as possible to avoid thermal leakage, which has a negative effect on the conversion efficiency of the system [2]. There are several factors that can have an effect on the short circuit current, including the PV cell area, the spectrum and intensity of the incident light, the absorption and reflection of the cell. While metallic emitters using tungsten or tantalum have the capacity to work at high temperature, they require special packaging such as maintenance of an inert or vacuum atmosphere, which is impractical in most TPV systems In this regard, ceramics exhibit a good stability in oxidizing atmosphere. The spectral and total heat fluxes, output power and conversion efficiency are exhibited

Theoretical Fundamentals for Analyzing Near-Field TPVs

Results and Discussion

Conclusions