近场热光伏和热辐射电池系统中熵的应用

Application of Entropy in Near-field Thermophotovoltaic and Thermoradiative Systems

近场辐射换热能够极大地提高热光伏和热辐射电池系统的输出电功率,因此研究近场热光伏和热辐射电池系统的转换效率具有重要意义。本文通过计算近场效应影响下的辐射热流和熵流,给出了近场热光伏和热辐射电池系统的最大理论转换效率,并与实际转换效率对比。结果发现在近场热光伏和热辐射电池系统中,纳米线、纳米孔两种微结构和双曲线材料相比平板和电介质,不仅有更强的辐射热流,而且有更高的理论效率。但是在实际过程中,由于近场热光伏和热辐射电池系统中光谱辐射热流的峰值频率小于电池能带间隙所对应的频率,所以其实际效率低于最大理论效率。本工作为近场热光伏和热辐射电池系统的转换效率提供了一个理论极限。

Near-field radiative heat transfer can improve the output power of thermophotovoltaic(TPV)and thermoradiative(TR)systems significantly.Therefore,it is crucial to study the energy conversion efficiencies of near-field TPV and TR systems.In this work,we evaluate the maximum theoretical efficiencies of near-field TPV and TR systems by analyzing the radiative heat fluxes and entropy fluxes.It is found that,in near-field TPV,TR cells paired with nanowire,nanohole arrays or hyperbolic metamaterial can achieve higher heat fluxes and maximum theoretical efficiencies compared to that of the bulk and dielectric reference.However,the actual efficiency is lower than the maximum theoretical efficiency because the peak frequency of spectral radiation heat flux in near-field TPV and TR systems are lower than the corresponding frequency of energy band gap.This work establish a theoretical limit for improving the ECE of near-field TPV and TR systems.