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As a natural biaxial hyperbolic material, α-phase molybdenum trioxide (α-MoO3) exhibits dielectric and metallic properties in the plane, rendering it an exceptional candidate for polarization-dependent devices. In this work, we design a lithography-free polarization-dependent absorber consisting of an α-MoO3 film, a germanium layer, and a silver substrate. The results show that a narrowband absorption of up to 0.99 is achieved at a wavelength of 12.2 µm for transverse magnetic polarization. In contrast, the absorption is only 0.06 at this wavelength for transverse electric polarization. This remarkable polarization-dependent absorption performance is attributed to the coupling of epsilon-near-zero modes and Fabry-Perot resonances, which is confirmed by the electric field and power dissipation density distributions. Furthermore, strong polarization-dependent performance could also be achieved when the crystal axis of α-MoO3 is rotated in the out-of-plane. This work demonstrates that in-plane anisotropic α-MoO3 has the potential for designing high polarization-dependent devices. [ABSTRACT FROM AUTHOR]

Optimal optical absorption properties are imperative for the utilization of nanofluids in solar energy applications. Excellent optical absorption facilitates the augmentation of solar energy utilization efficiency. The base fluid contributes significantly to the optical properties of the nanofluid. However, the effect of base fluid on the nanofluid optical properties has yet to be explored. This work investigates the effect of three base fluids, deionized water, ethylene glycol, and 1,2-propanediol, on the optical absorption properties of titanium nitride (TiN) nanofluids. The results show differences in the optical properties of the TiN nanofluids prepared for different sonication times. With the absence of surfactant addition, the stability of TiN nanofluids based on ethylene glycol-based and 1,2-Propanediol-based surpasses that of deionized water-based TiN nanofluids. However, in comparison to ethylene glycol-based and 1,2-Propanediol-based, deionized water-based TiN nanofluids exhibit commendable light absorption capacity. Finally, the photothermal conversion efficiency is calculated for different base fluids. The photothermal conversion efficiency of the deionized water-based TiN nanofluid is 50.82%, which is 13.91% and 15.98% higher than that of the ethylene glycol-based and 1,2-propanediol-based TiN nanofluids under the same conditions, respectively. Thus, deionized water-based TiN shows excellent optical absorption properties, essential for enhanced solar energy thermal utilization. This work will help guide the application of TiN nanofluids. [ABSTRACT FROM AUTHOR]

Solar absorber is the key component to realize efficient utilization of solar energy. In this paper, only titanium nitride (TiN) is used to create a broadband, wide-angle, polarization insensitivity solar absorber. The average absorption of the absorber in the spectral range of 300-2500 nm is 91.3%. The distributions of electric and magnetic fields indicate that the strong absorption is caused by the coupling effect of surface plasmon resonance and guided mode resonance. Investigate the effects of the geometric parameters of the absorber on the spectral absorption performance. Moreover, we also discuss the absorption performance of the solar absorber at different incidence angles. It is demonstrated that even at a large incidence angle of 60°, the average spectral absorption can exceed more than 70%. The proposed solar energy absorber is also insensitive to polarization. The research results in this work could benefit the applications in solar thermophotovoltaic system. [ABSTRACT FROM AUTHOR]

Concentrating photovoltaic (CPV) technology is a promising approach for collecting solar energy and converting it into electricity through photovoltaic cells, with high conversion efficiency. Compared to conventional flat panel photovoltaic systems, CPV systems use concentrators solar energy from a larger area into a smaller one, resulting in a higher density of solar radiation and increased electrical output. However, the use of concentrators can lead to nonuniform radiation and high temperatures that may damage the solar cells. Therefore, implementing a suitable thermal management solution is crucial to ensure optimal performance of CPV systems. This review article aims to provide a comprehensive overview of recent research and technical challenges in solar concentrators, trackers, and cooling systems for mitigating temperature effects and enhancing the efficiency of CPV cells. It will explore the causes and potential solutions for temperature effects in CPV systems, particularly focusing on the components involved. [ABSTRACT FROM AUTHOR]

Solar absorber is a key device that converts solar irradiation into heat via photothermal conversion, which has potential applications in solar thermal power systems, and seawater desalination. In this paper, we propose a wide-angle, broadband and polarization insensitivity metamaterial solar absorber based on titanium nitride (TiN). Numerical results show that this solar absorber has a total average spectrum absorption of up to 97.5% at wavelength of 300–2500 nm. Based on the distributions of the electric and magnetic field, it is believed that the coupling resonance of surface plasmon resonance, guided mode resonance and cavity resonance is responsible for its excellent absorption of solar energy. Furthermore, we discuss the effects of incidence angle on the solar absorber and demonstrate that the average spectrum absorption of more than 85% can be obtained even at a large incidence angle of 60°, and it is insensitive to the change of polarization angle. The effect of geometric parameters of the solar absorber on spectrum absorption performance was investigated. This research will provide new ideas for the design of solar thermophotovoltaic and thermal conversion systems. [ABSTRACT FROM AUTHOR]