Highly efficient selective metamaterial absorber for high-temperature solar thermal energy harvesting

Abstract

ABSTRACT:In this work, a metamaterial selective solar absorber made of nanostructured titanium gratings deposited on an ultrathin MgF 2 spacer and a tungsten ground film is proposed and experimentally demonstrated. Normal absorptance of the fabricated solar absorber is characterized to be higher than 90% in the UV, visible and, near infrared (IR) regime, while the mid-IR emittance is around 20%. The high broadband absorption in the solar spectrum is realized by the excitation of surface plasmon and magnetic polariton resonances, while the low mid-IR emittance is due to the highly reflective nature of the metallic components. Further directional and polarized reflectance measurements show wide-angle and polarization-insensitive high absorption within solar spectrum. Temperature-dependent spectroscopic characterization indicates that the optical properties barely change at elevated temperatures up to 350°C. The solar-to-heat conversion efficiency with the fabricated metamaterial solar absorber is predicted to be 78% at 100°C without optical concentration or 80% at 400°C with 25 suns, and could be further improved with better fabrication processes and geometric optimization during metamaterial design. The strong spectral selectivity, favorable diffuse-like behavior, and excellent thermal stability make the metamaterial selective absorber promising for significantly enhancing solar thermal energy harvesting in various system at mid to high temperatures.

Micro‐ and Nanostructured Surfaces for Selective Solar Absorption

“…The 2D array from ref. [ 107 ] A comprehensive investigation of the dependence of absorption on the polar and azimuthal angles of the incident wave was conducted as well. [ 75 ] , but works for both TE and TM polarizations.…”

Infrared Plasmonic Refractive Index Sensor with Ultra-High Figure of Merit Based on the Optimized All-Metal Grating

“…Recently, the plasmonic metamaterial absorbers based on the surface plasmon resonance (SPR) have attracted increasing attention due to their potential extensive applications in energy harvesting [1–3], hot-electron collection [4–7], thermal emitters [8–11], and biosensors [12–17]. Up to date, various plasmonic metamaterial absorbers have been proposed in different wavebands, which are mainly divided into two main categories: broadband absorbers and narrowband absorbers.…”

Numerical study of a wide-angle polarization-independent ultra-broadband efficient selective metamaterial absorber for near-ideal solar thermal energy conversion

“…In this work, W and SiO 2 are chosen as the base materials of the solar absorber owing to their thermal stability at high temperatures. 28,39 The nanopores of the structure are to reduce the effective refractive index of this absorber, which can achieve a better impedance match to free space. The rst SiO 2 layer coated onto the structure is operating as an antireective material, which is to further reduce the impedance mismatch.…”

“…8 To our knowledge, the reported selective solar absorption are mainly realized by these broadband absorbers based on the nanostructures constructed by arraying different nano-sized resonators in one plane to combine multiple plasmonic resonances. [38][39][40][41][42][43][44][45] For example, Aydin et al proposed and demonstrated a plasmonic absorber capable of selective high absorption over the visible spectrum(400-700 nm) owing to the symmetric arrangement of crossed trapezoid array geometry. 37 However, this absorber only can realize broadband high absorptions in the visible region and cannot satisfy the spectral requirements for solar energy absorption.…”

“…Note that, most of current selective solar absorbers also suffer from these three fundamental problems: (i) the low absorption efficiency in UV region; (ii) the absorption efficiency dropping at the middle of the high absorption band; (iii) angle-dependent absorption in TE polarization. 15,[38][39][40][41][42][43][44][45] In addition, these patterned metamaterial nanostructures increase much complexity to the fabrication owing to the large number of different nano-sized resonators. Then, the larger area applications of these broadband absorber are also limited by the complexity of the structure and fabrication difficulties.…”