Thermoelectrics versus thermophotovoltaics: Two approaches to convert heat fluxes into electricity
Roland Schmechel, Nanostrukturtechnik /UDE & CENIDE, Duisburg, GermanyIrene Ambo Okanimba Tedah, Nanostrukturtechnik /UDE & CENIDE, Duisburg, GermanyFranziska Maculewicz, Nanostrukturtechnik /UDE & CENIDE, Duisburg, GermanyDietrich E. Wolf, Theoretical Physics / UDE & CENIDE, Duisburg, Germany
Direct conversion of heat fluxes into electricity is usually done by thermoelectric generators (TEGs). For hot-side temperatures above 1000 K, thermal radiation becomes strong and a direct conversion of thermal radiation into electricity, named thermophotovoltaics (TPV), would also be an option. This poster compares both methods with respect to efficiency and extractable power density. The physical limits are estimated under simplified but realistic boundary conditions. For TPV the radiative detailed balance limit under black body radiation, which was calculated for different hot-side temperatures from 310 K to 3000 K for an optimized band gap of the applied material was used. The TEG efficiency and power density was calculated under thermal matching conditions with a thermal contact conductance of K=250W/m^2K and an average device ZT=1. The results are compared with experimental data for TPV and TEGs from literature. It is shown, that TPV has always the potential for the higher efficiency, but the extractable power density remains low, especially below 1000K. Above 1000K, the heat radiation power density starts to reach and even exceeds the power density of TEGs. But at such high radiation power densities, heating of the TPV cell will occur which will lower its efficiency. Therefore, cell cooling becomes an important issue.