Selective emitters for thermophotovoltaic applications

Abstract

Applying thermophotovoltaic (TPV) technologies to existing energy generators allows us to increase energy output while utilizing present infrastructure by reclaiming the heat lost during the production process. In order to maximize the efficiency of these sources, the conversion efficiency of the TPV system needs to be optimized. Selective emitters are often used to tailor the spectrum of incident light on the diode, blocking any undesirable light that may lead to device heating or recombination. Over the years, many different technologies have been researched to create an ideal selective emitter. Plasmas and rare‐earth emitters provided highly selective spectra early on, but their fixed peaks required tailoring the diode's band gap to the emitter's characteristic wavelength. Recent advances in engineerable materials, such as photonic crystals and metamaterials, allow the opposite to take place; an appropriate selective emitter can be designed to match the TPV diode, allowing the diode structure to be optimized independently from the emitter.

Ultra-narrow-band near-infrared thermal exciton radiation in intrinsic one-dimensional semiconductors

“…Finally, we comment on the potential significance of our findings with respect to a specific optothermal application known as thermophotovoltaics 2 , 3 . If the thermal energy stored in a solid can be efficiently converted to monochromatic near-infrared light, it can be used as an input to a photovoltaic cell to generate electricity (Supplementary Fig.…”

“…3c ) is remarkable; this is difficult to achieve in the near-infrared-to-visible range even using previous metal or semiconductor nanophotonic thermal emitters 4 – 6 in contrast to the successful control of the thermal emission in the mid-infrared (~10 µm) wavelength region ( Q factor of over 100) using quantum wells and photonic crystals 31 , 32 . To our best knowledge, this peaked thermal exciton radiation has the narrowest FWHM among reported solid state thermal emitters operable in the near-infrared-to-visible range around 1500 K 3 – 7 . The structure-dependent exciton resonance energies allow the nanotubes to potentially serve as ultra-narrow-band thermal emitters at various wavelengths.…”

Practical emitters for thermophotovoltaics: a review

“…Detailed discussion of emitter types, mechanisms, and more examples of emitters can be found in reviews elsewhere, such as that by Pfiester and Vandervelde. 3…”

Cavity Absorber-Emitters for High-Temperature Solar Thermophotovoltaics

“…There is a significant body of literature on all of these techniques, but this thesis will not focus on the optimization or selection of one of them for a specific application. Table 1: Comparison of several typical methods of spectral control for TPV, reproduced from Pfiester et al [6] Many of the challenges associated with STPV devices arise due to the multi-component, systemic nature of the devices. Recently, there have been several papers that present selective-emitters and reflectors fabricated and incorporated into STPV systems, but these systems have not demonstrated high system conversion efficiencies.…”

“…In our modeling, the effect of a selective surface is simplified through the definition of this diffuse effective emittance term, defined as ̅ ≡ emit bb (17) This ratio of net emitter radiative heat flux (Eemit) to black-body emissive power flux (Ebb) can be modified to account for several forms of spectral shaping including selectivity on the emitter side (i.e. selective emitters), the front surface of the PV cell (i.e., optical filters), or the back side of the PV cell (i.e., back surface reflectors) [6] [19]. Eq.…”