Solar thermophotovoltaics: reshaping the solar spectrum

Abstract

Abstract:Recently, there has been increasing interest in utilizing solar thermophotovoltaics (STPV) to convert sunlight into electricity, given their potential to exceed the Shockley-Queisser limit. Encouragingly, there have also been several recent demonstrations of improved systemlevel efficiency as high as 6.2%. In this work, we review prior work in the field, with particular emphasis on the role of several key principles in their experimental operation, performance, and reliability. In particular, for the problem of designing selective solar absorbers, we consider the trade-off between solar absorption and thermal losses, particularly radiative and convective mechanisms. For the selective thermal emitters, we consider the tradeoff between emission at critical wavelengths and parasitic losses. Then for the thermophotovoltaic (TPV) diodes, we consider the trade-off between increasing the potential short-circuit current, and maintaining a reasonable opencircuit voltage. This treatment parallels the historic development of the field, but also connects early insights with recent developments in adjacent fields. With these various components connecting in multiple ways, a system-level end-to-end modeling approach is necessary for a comprehensive understanding and appropriate improvement of STPV systems. This approach will ultimately allow researchers to design STPV systems capable of exceeding recently demonstrated efficiency values.

Nanophotonic engineering of far-field thermal emitters

“…4(a)]. 26 Assuming highly idealized components-ideal geometry, TE engineered to be monochromatic TE, only radiative recombination in the PV cell, full solar concentration, etc.-the efficiency of a TPV system could be as high as 85% 101 . In more realistic geometries, many factors affect the efficiency of a solar TPV device, including the absorber/emitter spectral responses and the ratio of their areas, parasitic thermal loss, nonidealities in the PV cell, among others.…”

“…In particular, the temperature of the intermediate absorber/emitter is an important parameter in determining the efficiency of solar TPV devices 101 . TE engineering, therefore, plays a key role on both ends of solar TPV systems-the solar absorbers and the selective emitters 26 . The ideal solar absorber should capture the vast majority of the solar spectrum-in the ultraviolet, visible, and near infrared-but should suppress TE in the mid infrared, such that energy loss to the sky is minimized.…”

Fundamental limits of hot carrier injection from metal in nanoplasmonics

“…where ph a is the fraction of the carriers generated via phonon/defect scattering and according to (22) for the propagating SPP With transport to the surface out of the way, we consider the extraction efficiency of all the quasi-ballistic carriers arriving at the surface, i.e. transmission coefficient over the barrier Φ .…”

“…The stage at which the absorbed energy can be captured with the least effort is obviously just after the energy has been transferred to the lattice (which in general is far less than a picosecond). Depending on how well the plasmonic entities are isolated from the surroundings, they can be heated by hundreds of degrees and that rise in temperature can be used for diverse applications ranging from cancer therapy [21] to thermophotovoltaics [22].…”

Designer Perfect Light Absorption Using Ultrathin Lossless Dielectrics on Absorptive Substrates

“…Optical absorbers, materials with absorptance A that enable strong ( A > 0.9) to perfect ( A > 0.99) light absorption, have many applications in thermo‐photovoltaics, photodetectors, stealth technologies, thermal emission, optical switches, hybrid solar converters, and structural coloring . When light is critically coupled to an optical resonator, light is perfectly absorbed.…”