scholarly journals Enhanced Performance and Diffusion Robustness of Phase-Change Metasurfaces via a Hybrid Dielectric/Plasmonic Approach

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 525
Author(s):  
Joe Shields ◽  
Carlota Ruiz de Galarreta ◽  
Jacopo Bertolotti ◽  
C. David Wright
Keyword(s):  
Melting Point ◽  
Phase Change ◽  
Noble Metals ◽  
Phase Change Materials ◽  
High Efficiency ◽  
The Body ◽  
Design Stage ◽  
High Melting ◽  
Optical Performance ◽  
Electrical Conductors

Materials of which the refractive indices can be thermally tuned or switched, such as in chalcogenide phase-change alloys, offer a promising path towards the development of active optical metasurfaces for the control of the amplitude, phase, and polarization of light. However, for phase-change metasurfaces to be able to provide viable technology for active light control, in situ electrical switching via resistive heaters integral to or embedded in the metasurface itself is highly desirable. In this context, good electrical conductors (metals) with high melting points (i.e., significantly above the melting point of commonly used phase-change alloys) are required. In addition, such metals should ideally have low plasmonic losses, so as to not degrade metasurface optical performance. This essentially limits the choice to a few noble metals, namely, gold and silver, but these tend to diffuse quite readily into phase-change materials (particularly the archetypal Ge2Sb2Te5 alloy used here), and into dielectric resonators such as Si or Ge. In this work, we introduce a novel hybrid dielectric/plasmonic metasurface architecture, where we incorporated a thin Ge2Sb2Te5 layer into the body of a cubic silicon nanoresonator lying on metallic planes that simultaneously acted as high-efficiency reflectors and resistive heaters. Through systematic studies based on changing the configuration of the bottom metal plane between high-melting-point diffusive and low-melting-point nondiffusive metals (Au and Al, respectively), we explicitly show how thermally activated diffusion can catastrophically and irreversibly degrade the optical performance of chalcogenide phase-change metasurface devices, and how such degradation can be successfully overcome at the design stage via the incorporation of ultrathin Si3N4 barrier layers between the gold plane and the hybrid Si/Ge2Sb2Te5 resonators. Our work clarifies the importance of diffusion of noble metals in thermally tunable metasurfaces and how to overcome it, thus helping phase-change-based metasurface technology move a step closer towards the realization of real-world applications.

Screening of high melting point phase change materials (PCM) in solar thermal concentrating technology based on CLFR

Solar Energy ◽  
2005 ◽  
Vol 79 (3) ◽  
pp. 332-339 ◽  
Author(s):  
Akira Hoshi ◽  
David R. Mills ◽  
Antoine Bittar ◽  
Takeo S. Saitoh
Keyword(s):  
Melting Point ◽  
Phase Change ◽  
Phase Change Materials ◽  
Solar Thermal ◽  
High Melting ◽  
High Melting Point

scholarly journals A Review of New Solar Still Design Comprising a Five-Sided Glass Cover and Equipped with an External Tank for PCM

2021 ◽  
Vol 877 (1) ◽  
pp. 012038
Author(s):  
Abbas Sahi Shareef ◽  
Hayder Jabbar Kurji ◽  
Hassan Abdulameer Matrood
Keyword(s):  
Melting Point ◽  
Phase Change ◽  
Solar Collector ◽  
Phase Change Materials ◽  
Review Paper ◽  
Pure Water ◽  
Solar Still ◽  
Glass Cover ◽  
Solar Distillation ◽  
Change Material

Abstract Various human activities have led to the consumption of large quantities of pure water, which has led researchers to find efficient and economical methods for desalinating seawater and water containing impurities. In this review paper, solar energy where it is permanent, abundant and environmentally friendly, to produce pure water was discussed using a new solar distillation device, representing the paper’s novelty. The distillation was designed and used in the way led to increase efficiency and improve productivity by adding a solar collector to the system and equipped with a tank containing phase change material (PCM). It has a low melting point and can change the phase by absorbing the system’s latent heat to maintain the system’s temperature. Which contributes to increasing the distillation period even after sunset, thus increasing the daily productivity of freshwater. Using phase change materials will increase distillation hours from (3-4) hours after sunset, increasing the amount of production between (75 - 90) %.

scholarly journals Recent Investigations of Phase Change Materials Use in Solar Thermal Energy Storage System

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Qianjun Mao ◽  
Ning Liu ◽  
Li Peng
Keyword(s):  
Energy Storage ◽  
Melting Point ◽  
Phase Change ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Heat Storage ◽  
Solar Thermal Energy ◽  
Temperature Heat

Solar thermal energy storage (TES) is an efficient way to solve the conflict between unsteady input energy and steady output energy in concentrating solar power plant. The latent heat thermal energy storage (LHTES) system is a main method of storing thermal energy using phase change materials (PCMs). Thermal properties, that is, melting points and latent heat, are the key parameters of PCMs for the TES system. In this paper, the PCMs are classified into inorganic and organic by the chemical composition, and according to the melting point, the inorganic PCMs can be divided into three contributions: low-temperature heat storage (less than 120°C), medium-temperature heat storage (120–300°C), and high-temperature heat storage (more than 300°C). The present article focuses mainly on the recent investigations on the melting point and latent heat of PCMs via DSC setup in the solar TES systems. The results can provide a good reference for the selection and utilization of PCMs in the solar TES systems.

Reconfigurable All Dielectric Metasurfaces based on Optical Phase Change Materials: Design Approaches

2020 ◽  
Vol 35 (11) ◽  
pp. 1445-1446
Author(s):  
Mikhail Shalaginov ◽  
Sensong An ◽  
Yifei Zhang ◽  
Fan Yang ◽  
Clayton Fowler ◽  
...  
Keyword(s):  
Phase Change ◽  
Light Propagation ◽  
Phase Change Materials ◽  
High Efficiency ◽  
Focal Length ◽  
Large Change ◽  
Optical Phase ◽  
Main Challenge ◽  
Arbitrary Phase ◽  
Large Tuning Range

Optical metasurface is a recently emerged paradigm for controlling light propagation, which enables implementation of ultra-compact optical devices with extended functionalities. Nowadays the main challenge in the field is to realize active metasurfaces with high quality, high efficiency, and large tuning range. Here we present a design approach for constructing a two-state reconfigurable metalens made of low-loss optical phase-change material (O-PCM). The metalens design is capable to produce diffraction limited focusing, large change in focal length (from 1.5 mm to 2mm), and decent focusing efficiency of about 20% in both states. The proposed design methodology is generic and can be easily extended towards constructing metasurfaces, which can switch between two or more arbitrary phase maps.

Experimental investigations of a solar dryer with and without multiple phase change materials (PCM’s)

2016 ◽  
Vol 13 (3) ◽  
pp. 210-217 ◽  
Author(s):  
T.S. Sreerag ◽  
K.S. Jithish
Keyword(s):  
Energy Storage ◽  
Melting Point ◽  
Phase Change ◽  
Phase Change Materials ◽  
Drying Process ◽  
Absorber Plate ◽  
Content Type ◽  
Air Heater ◽  
Multiple Phase ◽  
Solar Dryer

Purpose This paper aims to present a comparative study of a solar dryer with and without multiple phase change materials (PCMs). It also involves designing and fabricating the experimental model of an indirect solar dryer which uses PCMs for thermal energy storage. Design/methodology/approach A corrugated aluminium sheet is used as an absorber plate. Aluminium pipes of 0.75 inch are welded under the corrugated sheet to store the PCM. Here, multiple PCMs are used – one with a high melting point and the other with a low melting point for the purpose of improving efficiency. A single air pass model in which air moves over the absorber plate is used for the study. Air is heated in an air heater section which also contains thermal energy storage. The energy obtained in the air heater section is first used to heat and melt the PCM. Findings Thus, heat energy is stored into the PCM and then the heated air moves into the drying chamber in which drying take place. When the sun’s insolation reduces, discharging from the PCM takes place. Thus, it reduces the fluctuation in the energy and provides continuous energy to the system. Glass wool is used as an insulation material. Different parameters for this air heater-dryer have been calculated. Originality/value The current study enhances the understanding of solar drying process and the developed model with and without multiple phase change materials can be used for optimising the drying process.

scholarly journals Preparation of n-Alkane/Polycaprolactone Phase-Change Microcapsules via Single Nozzle Electro-Spraying: Characterization on Their Formation, Structures and Properties

2020 ◽  
Vol 10 (2) ◽  
pp. 561 ◽  
Author(s):  
Shengchang Zhang ◽  
Christine Campagne ◽  
Fabien Salaün
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Phase Change Materials ◽  
High Efficiency ◽  
Two Phase ◽  
Structures And Properties ◽  
The Matrix ◽  
Ft Ir ◽  
The Mean ◽  
Poly Caprolactone

The phase change microcapsule (mPCM) is one of the primary candidates in the fields of energy storage and thermal regulation. In this study, electro-spraying, as a green, high-efficiency electrohydrodynamic atomization technology, is applied to the microencapsulation of two phase change materials (PCM) (n-hexadecane and n-eicosane) with three loading contents (30%, 50%, and 70% by weight) in a polycaprolactone matrix. Ethyl acetate (EA) and chloroform (Chl) were chosen as solvents to prepare the working solutions. The objective of this study is to clarify the microencapsulation process during electro-spraying and to optimize the structure and properties of the electro-sprayed mPCM. The structures, morphologies, and thermal properties of the mPCM were characterized by optical microscopy (OM), scanning electron microscopy (SEM), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and fourier transform infrared spectroscopy (FT-IR). Electro-sprayed spherical and non-porous mPCM have been successfully prepared. The mean diameter and the particle size distribution depend mainly on the choice of the n-alkane, as well as the solvent used to prepare the working solutions. Meanwhile, the structure formation of electro-sprayed mPCM and the loading content of PCM were mainly influenced by the evaporation of the solvent and the phase separation between PCM and poly(caprolactone) (PCL) matrix. During the shell formation or PCL solidification, the control of the PCM leaching out of the matrix allows improving the loading content. Finally, based on a high latent heat and simple formation process, the electro-spraying route of PCM is a green, non-toxic, and high-efficiency direction for energy storage and heat regulation.

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