Experimental characterization and modeling of a nanofiber-based selective emitter for thermophotovoltaic energy conversion: The effect of optical properties

Abstract

The effect of nanofiber based filter morphology on bacteria deactivation during water filtration AIP Conf. Proc. 1526, 316 (2013); 10.1063/1.4802626Microwave Hall mobility and electrical properties of electrospun polymer nanofibers Aluminum oxide nanofibers doped with erbium oxide have been synthesized by calcining polymer fibers made by the electrospinning technique using a mixture of aluminum acetate, erbium acetate and polyvinylpyrrolidone dissolved in ethanol. The resulting ceramic fibers are used to fabricate a free-standing selective emitter. The general equation of radiation transfer coupled with experimentally measured optical properties is used to model the net radiation obtained from these structures. It has been found that the index of refraction and the extinction coefficient are direct functions of the erbia doping level in the fibers. The fibers radiated in a selective manner at ϳ1.53 m with an efficiency of about 90%. For a fiber film on a substrate, the effect of film thickness, extinction coefficient and substrate emissivity on the overall emitter emissivity is also investigated in this study. Results show that the emissivity of the film increases as the thickness of the film increases up to a maximum value, after which increasing the film thickness had no effect on emissivity. Furthermore, it has been found that the substrate emissivity increases the amount of off-band radiation. This effect can be mitigated by controlling the film thickness.

Modeling of emission properties from a spatially distributed selective emitter

“…The extinction coefficient has large values in the active wavelength range of erbium oxide and a small value outside this range. 5. 4 and data for quartz, we set e =45 cm −1 ͑erbia doped nanofibers͒ or e =17 cm −1 ͑pure erbium oxide͒, e =1 cm −1 , q =2 cm −1 , and q =1 cm −1 .…”

“…5 Equation ͑2͒ may be further simplified to the conservative case where the loss in the source function due to scattering is accounted for, however the gain due to in-scattering is neglected. The contribution to radiation intensity from "in-scattering" is due to radiation scattering from all directions into the original direction of radiation propagation and calculated by summing up all of the fractions of light scattered from all directions ͓hence the solid angle integration in Eq.…”

“…Those solutions will be derived based upon calculated expressions for and . 5. In particular, the expressions will describe the configurations shown in Fig.…”

“…5 Note that q and e are assumed to be constant over the spatial coordinate s. Defining ␤ q = q + q and ␤ e = e + e as the extinction coefficients of the nonemitting and the emitting layers, respectively, we find that The subscript q denotes quartz and e denotes erbia-doped media, since these were the constituents of the selective emitter fabricated in the companion work.…”