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Dielectric metasurfaces have made great progress over the past decade to enhance light-matter interaction. Recently, dielectric nanohole structures have been employed for the creation of dielectric metasurfaces. However, the optical characteristics of most dielectric nanohole structures remain fixed once they are manufactured. This study investigates the optical properties of Ge2Sb2Te5 (GST) film perforated with a periodic dual nanohole array. The GST dual nanohole array is capable of supporting multiple guided resonances and bound states in the continuum (BICs). By introducing asymmetry in the radius, BICs can be transformed into quasi-BICs with high- Q resonances. The wavelengths of guided resonances and quasi-BICs can be dynamically controlled through the phase transition of GST. Furthermore, modifying the gap allows for the achievement of active high- Q electromagnetically induced transparency, resulting from the interaction between one guided resonance and one quasi-BIC mode. The GST asymmetric nanohole array holds potential for applications in optical modulators, slow-light devices, and nonlinear optical devices. [ABSTRACT FROM AUTHOR]

This study explores the conduction mechanism of NbTe4, a novel phase-change material (PCM) for phase-change random access memory (PCRAM), and addresses the limitations of the widely used Ge2Sb2Te5 (GST). Unlike traditional PCMs, NbTe4 in its amorphous state demonstrates low resistance, which indicates semiconductor behavior. However, the Hall and Seebeck coefficient measurements reveal an intriguing anomaly--amorphous NbTe4 displays N-type conduction with Hall voltage and P-type conduction in the positive Seebeck coefficient. This Hall effect anomaly, which is typically associated with highly resistive chalcogenide materials, raises questions about the conduction mechanism in amorphous NbTe4. This study delves into the electrical transport properties of NbTe4 and provides insights into the unique characteristics of this PCM. [ABSTRACT FROM AUTHOR]

Actively tunable ultrafast broadband terahertz (THz) polarimetry using a reconfigurable phase‐change material holds great potentials and prospects for the achievement of next‐generation versatile integrated THz components and systems in a variety of THz applications. Here, an optically tunable ultrafast broadband THz polarimetric device (THz‐PoD) composed of a phase‐change material Ge2Sb2Te5 (GST) and a thin mica substrate is demonstrated. This proposed novel THz‐PoD is verified for a frequency range of 0.1–2.5 THz, exhibiting broadband and ultrafast determination of polarization states for linearly polarized THz waves at polarization angles from −90° to 90°. It is shown that optical excitation with ns pulses allows easy and efficient control of the polarimetric properties of such THz‐PoD. The essential role of the GST film in switching the phase transition between the amorphous and crystalline phases is emphasized by the theoretical investigation of the optically tunable ultrafast polarimetric mechanism of the device. This phase transition allows optically changing the THz‐PoD's properties by ns‐pulsed laser in a controlled way to achieve THz polarimetry for linearly polarized THz waves. The combined advantages of this strategy can open up a new and promising way for realizing versatile reconfigurable and integrated THz devices, which may further promote the development of novel THz systems and applications. [ABSTRACT FROM AUTHOR]

To gain a complete understanding of the optical switch that uses phase-change material, Ge2Sb2Te5 (GST), we conducted a simulation considering various physical phenomena related to the switch, such as electrical conduction, Joule heating, heat diffusion, phase change of GST, and light propagation. It was found that the phase state (amorphous and crystalline) of the GST film can be controlled by applying an appropriate pulse voltage to the indium tin oxide (ITO) heater layer, thereby changing the transmittance of the optical switch. Calculations showed that during cooling in the amorphization process, part of the GST film was recrystallized, reducing the transmittance of the optical switch in the ON state. Moreover, the large temperature difference in the GST film during heating was caused by a substantial amount of Joule heat generated in the region distant from the GST film. This difference in distance from the heat-generating region resulted in a considerable temperature difference in the GST film. Thus, herein, we have proposed modified model structures to reduce this temperature difference in the GST film, which can recrystallize during the amorphization process. Calculation using the modified model structures revealed that increasing the thickness of the ITO heater layer, over which the GST film was not placed, can effectively reduce the temperature difference and eventually suppress recrystallization. [ABSTRACT FROM AUTHOR]

Dielectric metasurfaces have made significant advancements in the past decade for enhancing light–matter interaction at the nanoscale. Particularly, bound states in the continuum (BICs) based on dielectric metasurfaces have been employed to enhance nonlinear harmonic generation. However, conventional nonlinear metasurfaces are typically fixed in their operating wavelength after fabrication. In this work, we numerically demonstrate tunable third harmonic generation (THG) by integrating a dielectric metasurface with the phase-change material Ge2Sb2Te5 (GST). The hybrid phase-change metasurface can support two BICs with different electromagnetic origins, which are transformed into two high-Q quasi-BICs through the introduction of structural asymmetry. The two quasi-BICs are selectively excited by controlling the polarization of incident light, and their wavelengths are tunable due to the phase transition of GST. Notably, the efficiency of THG is significantly enhanced at the fundamental wavelengths corresponding to the two quasi-BICs, and the operating wavelength for THG enhancement can be dynamically tuned through the GST phase transition. Furthermore, the wavelength of THG enhancement can be further tuned by manipulating the polarization of pump light. Additionally, a high-Q analog of electromagnetically induced transparency is numerically achieved through the interaction between a low-Q Mie resonance and a quasi-BIC mode, which also improves the THG efficiency. The high-Q polarization-controlled hybrid phase-change metasurface holds promise for applications in dynamically tunable nonlinear optical devices. [ABSTRACT FROM AUTHOR]

Latent Heat Transfer Thermal Energy Storage (LHTES) units are crucial in managing the variability of solar energy in solar thermal storage systems. This study explores the effectiveness of strategically placing layers of anisotropic and uniform metal foam (MF) within an LHTES to optimize the melting times of phase-change materials (PCMs) in three different setups. Using the enthalpy–porosity approach and finite element method simulations for fluid dynamics in MF, this research evaluates the impact of the metal foam's anisotropy parameter (Kn) and orientation angle (ω) on thermal performance. The results indicate that the configuration placing the anisotropic MF layer to channel heat towards the lower right corner shortens the phase transition time by 2.72% compared to other setups. Conversely, the middle setup experiences extended melting periods, particularly when ω is at 90°—an increase in Kn from 0.1 to 0.2 cuts the melting time by 4.14%, although it remains the least efficient option. The findings highlight the critical influence of MF anisotropy and the pivotal role of ω = 45°. Angles greater than this significantly increase the liquefaction time, especially at higher Kn values, due to altered thermal conductivity directions. Furthermore, the tactical placement of the anisotropic MF layer significantly boosts thermal efficiency, as evidenced by a 13.12% reduction in the PCM liquefaction time, most notably in configurations with a lower angle orientation. [ABSTRACT FROM AUTHOR]

A solar-powered combined cooling, heating, and power (CCHP) plant integrated with a water electrolysis unit is investigated in terms of energy, exergy, and exergo-economic (3E) assessments. A comprehensive parametric study and optimization is conducted following the thermodynamic and exergo-economic assessment of the proposed system to evaluate the key performance parameters of the system for efficiency and economic factors. This system employs a heliostat field and a receiver tower by taking advantage of thermal energy from the sun and produces a continuous energy supply with an integrated phase-change material (PCM) tank to store the heat. In addition, a supercritical CO2 Rankine cycle (RC), an ejector refrigeration cooling (ERC) system, and a PEM water electrolyzer are coupled to produce cooling, heating, power, and hydrogen. Thermodynamic analysis indicates that the system exergy efficiency and energy efficiency are improved to 33.50 % and 40.61 % , respectively, while the total cost rate is 2875.74   U S D / h and the total product cost per exergy unit is 25.65   U S D / G J . Additionally, the system produces a net generated power, heating load, and cooling load of 11.70 , 13.92 , and 2.60   M W , respectively, and a hydrogen production rate of 12.95 g / s . A two-objective optimization approach utilizing a non-dominated sorting genetic algorithm (NSGA) was performed, demonstrating that the system's ideal design point offers a cost rate of 1263.35   U S D / h and an exergetic efficiency of 34.17 % . [ABSTRACT FROM AUTHOR]

The preservation of perishable food items within the cold chain is a critical aspect of modern food logistics. Traditional refrigeration systems consume large amounts of energy, without an optimal temperature distribution, leading to potential food spoilage and economic losses. In recent years, the integration of Phase Change Materials (PCMs) into cold chain systems has emerged as a promising solution to address these challenges. This article presents a comprehensive analysis of the utilization of PCMs for food preservation in a refrigerated truck, focusing on the impact on temperature control, phase change fraction, costs, and energy savings. The effectiveness of PCM-based refrigeration system to maintain the refrigerated truck at a temperature of −18 °C under various scenarios and environmental conditions using a transient model was evaluated. The TRNSYS model includes a representation of a conventional refrigerated van's system, with simulations conducted in a Mediterranean climate (Naples). The model's core components consist of Type 56 for cooling load estimation and Type 1270a for the new PCM component. Results indicate that for guaranteeing −18 °C for 10 h, 96.4 kg and 102.2 kg of E-26 and E-29 PCM are needed, respectively, for scenarios with 10 door openings during transportation and for two different velocities of the truck: 30 and 80 km h−1. Results indicate that the incorporation of PCMs in the refrigerated van leads to significant improvements in temperature stability and uniformity, thereby extending the shelf life of perishable food products and reducing the risk of spoilage. Furthermore, the analysis shows that, using the PCMs, a significant reduction of the energy costs can be obtained (up to a maximum of around 79%). [ABSTRACT FROM AUTHOR]

Leakage is a high-incidence disease of embankment dams, and efficiently addressing this disease guarantees the safe operation of dams. Underwater leakage self-priming plugging technology is a new technology that utilizes the melting and solidifying characteristics of phase-change materials and the negative pressure in the leakage entry area to accurately plug the leakage. However, little is yet known about the underwater melting process of phase-change materials and how their characteristics influence the plugging effect. In this study, three kinds of phase-change materials, namely, paraffin, rosin, and stearic acid, were used to conduct underwater leakage self-priming plugging tests, observe and analyze the underwater melting process, and compare the plugging effects. The results showed that the underwater melting process of phase-change materials exhibited different plugging window periods depending on their melting points, specific heat capacities, and mobilities, which were the main factors affecting their plugging effects. In the final plugging stage, paraffin had the best plugging effect, but the material strength was low; rosin had good plugging compactness, but the fluidity performance was poor, and the material effective utilization was low; stearic acid had a low melting point but dispersed easily. Therefore, a blocking material with a suitable blocking window period can be produced by adjusting the material properties accordingly for an improved blocking effect. [ABSTRACT FROM AUTHOR]

Solar‐driven steam generation by heat localization has proven to be one of the most promising technologies for broad water‐related applications to relieve global water shortage and pollution due to the excellent interfacial water evaporation ability demonstrated both experimentally and theoretically. However, solar power changes fast in practical, such fluctuations on solar energywould invalidate conventional solar evaporator, leave a challenge on sustaining an efficient thermal evaporation. Herein, a mitigating‐solar‐fluctuation hybrid gel material (MHG) with chemical integrating of phase‐change material to achieve efficient steam generation under solar fluctuations is reported. By storing solar energy when it is surplus and providing thermal energy to sustain evaporation when it is insufficient, the MHGs solar evaporator under solar fluctuations achieves optimized water evaporation rate of 1.7 ± 0.02 kg m−2 h−1 for the high period of 0.8 sun and 1.3 ± 0.06 kg m−2 h−1 for the low period of 0.5 sun. The MHGs also exhibit outstanding solar desalination performance with good stability and demonstrate an effective brine desalination during round‐the‐clock desalination process with an average high evaporation rate of 1.24 kg m−2 h−1 d−1. This new material design provides a feasible strategy for solar evaporator to mitigate damage from solar fluctuations. [ABSTRACT FROM AUTHOR]

The application efficiency of the Dynamic Rotating Latent-Energy-Storage Envelope (DRLESE) system is highly contingent upon dynamic rotation timings. To gain the optimal rotation timings, six different timings were examined by employing the liquid fraction, thermal storage and release, surface temperature and heat flow. The numerical heat transfer method was employed and verified an experiment. Results indicated that the optimal initial rotation occurs in the forenoon, when the inner surface temperature aligns with the sol-air temperature. Subsequently, achieving optimal secondary rotation is possible in the afternoon when the sol-air temperature equals the liquid temperature of PCM (Phase Change Material). Under these optimized initial and secondary rotation timings, the significant enhancements in thermal performance of the DRLESE system were observed. By optimizing rotation timings, indoor effective heat release can reach up to 3182.9 kJ/Day with an effectiveness percentage exceeding 99.99%, and inner surface heat flow was increased by 5.86%–12.26%.

The conventional latent-energy-storage-envelope relies solely on the phase changes of Phase-Change Materials (PCMs) to regulate heat transfer, thereby lacking the effectiveness in active indoor heating or cooling. To overcome this technical barrier, the Dynamic Rotating Latent-Energy-Storage Envelope (DRLESE) was proposed to achieve active indoor heating by rotating the PCM layer. The DRLESE can absorb solar gain efficiently and release thermal energy directly indoors. In order to assess the application efficiency of DRLESE, two high-insulation walls incorporating a PCM layer were constructed, with the static one serving as a reference. A numerical heat transfer method was employed and verified an experiment. The numerical results demonstrated that compared to the Static Latent-Energy-Storage Envelope (SLESE), the DRLESE system can release stored thermal energy directly indoors by rotating the PCM layer near the interior, resulting in a released heat flow ranging from −22W/m2 to −80W/m2. However, due to differences in the heat release environment, DRLESE exhibits a lower thermal release rate leading to a reduction of up to 33.8 %∼34.8 % in its thermal release and storage capacity. The DRLESE not only limits thermal dissipation from outdoors but also provides indoor heating, while it provides the thermal energy per unit area to minimize the cooling load of the SLESE with 10.39 m2∼14.10 m2. Finally, it is identified on the present deficiencies and limitations for further the comprehensive investigations.

Switchable radiative cooling based on the phase-change material vanadium dioxide (VO2) automatically modulates thermal emission in response to varying ambient temperature. However, it is still challenging to achieve constant indoor temperature control solely using a VO2-based radiative cooling system, especially at low ambient temperatures. Here, we propose a reverse-switching VO2-based radiative cooling system, assisting indoor air conditioning to obtain precise indoor temperature control. Unlike previous VO2-based radiative cooling systems, the reverse VO2-based radiative cooler turns on radiative cooling at low ambient temperatures and turns off radiative cooling at high ambient temperatures, thereby synchronizing its cooling modes with the heating and cooling cycles of the indoor air conditioning during the actual process of precise temperature control. Calculations demonstrate that our proposed VO2-based radiative cooling system significantly reduces the energy consumption by nearly 30 % for heating and cooling by indoor air conditioning while maintaining a constant indoor temperature, even surpassing the performance of an ideal radiative cooler. This work advances the intelligent thermal regulation of radiative cooling in conjunction with the traditional air conditioning technology.

Phase-change materials (PCMs) are commonly employed in building service equipment to regulate indoor temperatures and reduce energy consumption. This study conducted multi-scale finite element modeling to analyze the steady-state and dynamic thermal behavior of a hydronic radiant floor heating system integrated with macro-encapsulated PCMs. It predicted performance values for hydronic floor heating with and without macro-encapsulated PCMs. The study assessed the impact of the PCM volume fraction, heating water temperature, capsule thermal conductivity, and shape on the thermal performance of hydronic floor heating through various finite element models. The predictive capability of the finite element model was validated using experimental data, showing good agreement. Although the inclusion of PCMs lowered the floor temperature, it improved temperature distribution and retained heat when the system was inactive. The PCM volume fraction significantly influenced the performance of the hydronic floor. However, the shape of the macro-encapsulated PCM and thermal conductivity of the shell had minimal effects in the studied case. For instance, increasing the thermal conductivity of the shell of the PCM capsule fifty times from 0.3 to 15 W m−1 K−1 resulted in an increase in surface temperature by 1.2 °C. [ABSTRACT FROM AUTHOR]

Polyethylene glycol (PEG) is a widely available and environmentally friendly phase change material known for its high energy storage capacity. However, its application in various industries is limited due to slow heat absorption and release, poor mechanical properties, and inadequate weather resistance. PEG was blended with waterborne epoxy resin (WER) to improve its mechanical properties and weather resistance. Furthermore, graphene nanoplatelets (GNPs) and boron nitride (BN) were incorporated into the WER/PEG resin substrate to prepare WER/PEG/BN@GNP coatings, resulting in enhanced thermal conductivity. When the GNP content was 0.5 wt%, the WER/PEG/BN@GNP coatings performed excellent anti‐corrosion. Otherwise, the leakage of PEG under heat‐cool cycling was addressed by the preparation of WER/PEG/BN@GNP coatings, as well as the low rates of heat absorption and release. In this work, the preparation method successfully combines the phase‐change characteristics of PEG, the outstanding mechanical properties of WER, and the high thermal conductivity of BN and GNP. The WER/PEG/BN@GNP coatings present significant potential for practical applications. Highlights: A new coating is prepared by incorporation of BN/GNP into PEG/WER matrix.The prepared coating performs phase change and good heat conduction efficiency.The phase‐transition leakage of PEG is resolved by the combination with WER.The synergy of BN and GNP fillers can enhance thermal conductivity effectively.The prepared coating exhibits insulation and anti‐corrosion at low GNP content. [ABSTRACT FROM AUTHOR]

The optical properties of phase‐change materials (PCMs) can be tuned to multiple levels by controlling the transition between their amorphous and crystalline phases. In multi‐material PCM structures, the number of discrete reflectance levels can be increased according to the number of PCM layers. However, the effect of increasing the number of layers on quenching and reversibility has not been thoroughly studied. In this work, the phase‐change physics and thermal conditions required for reversible switching of single and multi‐material PCM switches are discussed based on thermo‐optical phase‐change models and laser switching experiments. By using nanosecond laser pulses, 16 different reflectance levels in Ge2Sb2Te5 are demonstrated via amorphization. Furthermore, a multi‐material switch based on Ge2Sb2Te5 and GeTe with four discrete reflectance levels is experimentally proven with a reversible multi‐level response. The results and design principles presented herein will impact active photonics applications that rely on dynamic multi‐level operation, such as optical computing, beam steering, and next‐generation display technologies. [ABSTRACT FROM AUTHOR]

Solid–liquid organic phase-change micro/nanocapsules are potential candidates for energy storage. Recently, significant progress has been made regarding phase-change micro/nanocapsules in terms of their synthesis, properties, and applications. Extensive research has been conducted to enhance their thermal properties, such as thermal storage capacity, thermal conductivity, and thermal reliability. However, factors that influence the thermal properties of micro/nanocapsules have received little attention. This study presents a comprehensive review of phase-change micro/nanocapsules focusing on their thermal properties and their influencing factors. In addition, the thermal properties of the major solid–liquid organic pure phase-change materials are summarized. Furthermore, common micro/nanoencapsulation methods and their influence on the thermal properties were analyzed. Finally, the potential applications of these phase-change micro/nanocapsules were also investigated. This study was devoted to enhancing the thermal properties of micro/nanocapsules, which play a crucial role in their practical applications. [ABSTRACT FROM AUTHOR]

This paper presents a review of the storage of solar thermal energy with phase‐change materials to minimize the gap between thermal energy supply and demand. Various types of systems are used to store solar thermal energy using phase‐change materials. The performance of latent heat storage is dependent on the shape and size of the fins, the orientation and design of the storage unit, and its position. The efficiency of a solar thermal collector integrated with phase change material depends on the inclination of the collector, the position of the phase change material, and its thermo‐physical properties. The study of the thermo‐physical properties of various phase‐change materials and their effects is the focus of this paper. [ABSTRACT FROM AUTHOR]

Latent thermal energy storage (LTES) devices can efficiently store renewable energy in thermal form and guarantee a stable-temperature thermal energy supply. The gravity-driven motion melting (GDMM) process improves the overall melting rate for packaged phase-change material (PCM) by constructing an enhanced flow field in the liquid phase. However, due to the complex mechanisms involved in fluid–solid coupling and liquid–solid phase transition, numerical simulation studies that demonstrate physical details are necessary. In this study, a simplified numerical model based on the Eulerian method is proposed. We aimed to introduce a fluid deformation yield stress equation to the "solid phase" based on the Bingham fluid assumption. As a result, fluid–solid coupling and liquid–solid phase transition processes become continuously solvable. The proposed model is validated by the referenced experimental measurements. The enhanced performance of liquid-phase convection and the macroscopic settling of the "solid phase" are numerically analyzed. The results indicate that the enhanced liquid-phase fluidity allows for a stronger heat transfer process than natural convection for the pure liquid phase. The gravity-driven pressure difference is directly proportional to the vertical melting rate, which indicates the feasibility of controlling the pressure difference to improve the melting rate. [ABSTRACT FROM AUTHOR]

The current study aims to improve the energy storage capability of the thermal energy storage system by utilizing multiple phase-change materials. In this regard, a new thermal energy storage system has been studied when multiple phase-change material with different melting temperatures are employed. In this study, three-set, each having 70 encapsulated phase-change materials, are arranged horizontally in the order of decreasing melting temperature for the charging cycle and increasing melting temperature in the case of discharging cycle. Water is employed as heat transfer fluid, and the SAE 304 spherical capsule with a diameter of 60 cm is used to encapsulate the phase-change material. The arrangement showed an excellent thermal response for input parameters such as inlet temperature, flow rate. Further, it was observed that as the heat transfer fluid flow rate increases from 1 litres per minute (LPM) to 5 LPM, the melting and solidification time decreases from 10% to 30% and 14% to 28%, respectively. It was also noticed that as the flow rate increases, exergy and overall efficiency decreases. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive review of the thermal management strategies employed in cylindrical lithium-ion battery packs, with a focus on enhancing performance, safety, and lifespan. Effective thermal management is critical to retain battery cycle life and mitigate safety issues such as thermal runaway. This review covers four major thermal management techniques: air cooling, liquid cooling, phase-change materials (PCM), and hybrid methods. Air-cooling strategies are analyzed for their simplicity and cost-effectiveness, while liquid-cooling systems are explored for their superior heat dissipation capabilities. Phase-change materials, with their latent heat absorption and release properties, are evaluated as potential passive cooling solutions. Additionally, hybrid methods, such as combining two or more strategies, are discussed for their synergistic effects in achieving optimal thermal management. Each strategy is assessed in terms of its thermal performance, energy efficiency, cost implications, and applicability to cylindrical lithium-ion battery packs. The paper provides valuable insights into the strengths and limitations of each technique, offering a comprehensive guide for researchers, engineers, and policymakers in the field of energy storage. The findings contribute to the ongoing efforts to develop efficient and sustainable thermal management solutions for cylindrical lithium-ion battery packs in various applications. [ABSTRACT FROM AUTHOR]

Phase-change materials (PCMs) are widely used in the thermal management of electronic devices by effectively lowering the hot end temperature and increasing the energy conversion efficiency. In this article, numerical studies were performed to understand how temperature instability during the periodic utilization of electronic devices affects the heat-dissipation effectiveness of a phase-change material heat sink embedded in an electronic device. Firstly, three amplitudes of 10 °C, 15 °C, and 20 °C for fixed periods of time, namely, 10 min, 20 min, and 40 min, respectively, were performed to investigate the specific effect of amplitude on the PCM melting rate. Next, the amplitude was fixed, and the impact of the period on heat sink performance was evaluated. The results indicate that under the 40 min time period, the averaged melting rate of PCMs with amplitudes of 20 °C, 15 °C, and 10 °C reaches the highest at 19 min, which saves 14 min, 10 min, and 8 min, respectively, compared with the constant input of the same melting rate. At a fixed amplitude of 20 °C, the PCM with a period of 40 min, 20 min, and 10 min has the highest averaged melting rate at 6 min, 11 min, and 19 min, saving the heat dissipation time of 3 min, 8 min, and 14 min, respectively. Overall, it was observed that under identical amplitude conditions, the peak melting rate remains consistent, with longer periods resulting in a longer promotion of melting. On the other hand, under similar conditions, larger amplitude values result in faster melting rates. This is attributed to the fact that the period increases the heat flux output by extending the temperature rise, while the amplitude affects the heat flux by adjusting the temperature.

In this study, we developed a thermal storage medium comprising porous activated carbon filled with organic phase-change materials (PCMs) that utilizes the latent heat of phase-change to absorb heat during heating and release heat during cooling. For the activated carbon, we used both charcoal-based powdered activated carbon (250–350 mesh) and granular activated carbon. The organic phase-change materials used in the experiments were dodecane, tridecane, tetradecane, and pentadecane. Material properties such as thermal conductivity, latent heat, and melting temperature range were evaluated experimentally and theoretically, with the results observed to be consistent. The cyclic thermal performance of the proposed medium was also evaluated. Notably, filling the activated carbon with a mixture of organic PCMs resulted in the highest temperature-moderating effect. The procedure and results presented in this study are expected to aid in further improvement in the performance of thermal storage media containing PCM where stable temperatures are required, including building heating and cooling. [ABSTRACT FROM AUTHOR]

Faced with the world’s environmental and energy-related challenges, researchers are turning to innovative, sustainable and intelligent solutions to produce, store, and distribute energy. This work explores the trend of using a smart sensor to monitor the stability and efficiency of a salt-gradient solar pond. Several studies have been conducted to improve the thermal efficiency of salt-gradient solar ponds by introducing other materials. This study investigates the thermal and salinity behaviors of a pilot of smart salt-gradient solar ponds with (SGSP) and without (SGSPP) paraffin wax (PW) as a phase-change material (PCM). Temperature and salinity were measured experimentally using a smart sensor, with the measurements being used to investigate the stabilizing effects of placing the PCM in the solar pond’s lower convective zone. The experimental results show that the pond with the PCM (SGSPP) achieved greater thermal and salinity stability, with there being a lesser temperature and salinity gradient between the different layers when compared to a solar pond without the PCM (SGSP). The use of the PCM, therefore, helped control the maximum and minimum temperature of the pond’s storage zone. The UCZ has been found to operate approximately 4 degrees above the average ambient temperature of the day in the SGSPP and 7 degrees in SGSP. Moreover, an unstable situation is generated after 5 days from starting the operation and at 1.9 m from the bottom, and certain points have the tendency to be neutral from the upper depths in 1, 3 m of the bottom. [ABSTRACT FROM AUTHOR]

Glass curtain walls (GCWs) have become prevalent in office buildings, owing to their lightweight and modular characteristics. However, their lower thermal resistance, compared to opaque walls, results in increased energy consumption. Incorporating phase-change materials (PCMs) provides a viable solution through which to address the susceptibility of GCWs to external conditions, thus enhancing thermal performance and mitigating energy concerns. This study delves into the influences of the glazing solar heat gain coefficient (SHGC), the glazing heat transfer coefficient (U-value), and PCM thickness on the energy performance of buildings. Using Design Builder (DB) software version 6.1.0.006, a multi-story office building was simulated in different climatic zones in China, covering the climatic characteristics of severe cold, cold, hot summer and warm winter, cold summer and winter, and mild regions. The simulation results quantitatively elucidated the effects of the glazing parameters and the number of PCMs on thermal regulation and energy consumption. A sensitivity analysis identified the glazing SHGC as the most influential factor in energy consumption. Additionally, by employing Response Surface Methodology (RSM), the researchers aimed to achieve a balance between minimal building energy consumption and economic cost, ultimately determining an optimal design solution. The results demonstrated significant energy savings, ranging from 20.16% to 81.18%, accompanied by economic savings, ranging from 15.78% to 79.54%, across distinct climate zones in China. [ABSTRACT FROM AUTHOR]

Based on the research status of phase-change material (PCM) energy piles, this paper proposes a new type of PCM energy pile-spiral tube-encapsulated PCM energy pile. In order to study the related properties of the energy pile, this study designed and processed the relevant test equipment and built an indoor scale model experimental system. The thermodynamic performance of the spiral tube-encapsulated phase-change energy pile under summer conditions was studied by the test system. Through the indoor scale model test, it is found that compared with the traditional energy pile, the spiral tube-encapsulated PCM energy pile improves the heat exchange capacity of the unit pile body in the early and middle stages of operation, and reduces the surface temperature of the pile body and the heating rate of the surface temperature of the pile body. The upward displacement of the energy pile top is reduced. The heat exchange capacity of the unit pile depth is increased by 6.52 W/m, the maximum pile surface temperature difference is 0.62 °C, and the maximum pile top displacement difference is 0.005 mm. In addition, the total heat transfer of the spiral tube-encapsulated PCM energy pile during the whole operation period is 3.38% higher than that of the traditional energy pile. However, during the whole operation period, the surface stress value of the spiral tube encapsulated PCM energy pile is higher than that of the traditional energy pile. The maximum difference between the two is 9.84 kPa and the maximum difference is 10.8%. The difference between the two is finally stabilized at 1.4 kPa with an increase in time, and the final difference is only 8.8%. [ABSTRACT FROM AUTHOR]

Oscillatory neural networks (ONNs) exhibit a high potential for energy-efficient computing. In ONNs, neurons are implemented with oscillators and synapses with resistive and/or capacitive coupling between pairs of oscillators. Computing is carried out on the basis of the rich, complex, non-linear synchronization dynamics of a system of coupled oscillators. The exploited synchronization phenomena in ONNs are an example of fully parallel collective computing. A fast system's convergence to stable states, which correspond to the desired processed information, enables an energy-efficient solution if small area and low-power oscillators are used, specifically when they are built on the basis of the hysteresis exhibited by phase-transition materials such as VO2. In recent years, there have been numerous studies on ONNs using VO2. Most of them report simulation results. Although in some cases experimental results are also shown, they do not implement the design techniques that other works on electrical simulations report that allow to improve the behavior of the ONNs. Experimental validation of these approaches is necessary. Therefore, in this study, we describe an ONN realized in a commercial CMOS technology in which the oscillators are built using a circuit that we have developed to emulate the VO2 device. The purpose is to be able to study in-depth the synchronization dynamics of relaxation oscillators similar to those that can be performed with VO2 devices. The fabricated circuit is very flexible. It allows programming the synapses to implement different ONNs, calibrating the frequency of the oscillators, or controlling their initialization. It uses differential oscillators and resistive synapses, equivalent to the use of memristors. In this article, the designed and fabricated circuits are described in detail, and experimental results are shown. Specifically, its satisfactory operation as an associative memory is demonstrated. The experiments carried out allow us to conclude that the ONN must be operated according to the type of computational task to be solved, and guidelines are extracted in this regard. [ABSTRACT FROM AUTHOR]

The thermal performance of a lithium-ion battery module comprising three cells contained within a casing was investigated at discharge rates of 3C and 5C with three different cooling strategies: forced air, phase-change material (PCM), and a hybrid system using a combination of forced air and the PCM. Three levels of fan speed (5000 rpm; 7000 rpm; and 9000 rpm) for cooling air flow were considered. A numerical simulation of heat transfer was performed using the ANSYS Fluent software. The electrochemical modelling of a battery was developed based on the NTGK approach, and the phase-change phenomenon was treated as an enthesis–porosity problem. The composite PCM, aluminum metal foam embedded in n-octadecane, had better heat dissipation performance than forced air convection. The PCM is significantly more effective at heat dissipation than forced air. Interestingly, when using a hybrid cooling system that combines forced air and a PCM, although it meets the operational requirements for Li-ion batteries in regard to maximum temperature and temperature uniformity at a 3C discharge rate, the airflow appears to have a negligible effect on thermal management and yields an indiscernible change in temperature. This can be attributed to a complex flow pattern that developed in a casing as a result of the suboptimal design of the inlet and outlet. Further studies will be required for the optimal positioning of the inlet and outlet, as well as the effectiveness of combining liquid cooling methods. [ABSTRACT FROM AUTHOR]

The paper focuses on the experimental study and implementation of the forced convection indirect solar dryer based on the phase-change material (PCM). The dryer consists of an air solar collector combined with a PCM cavity and a drying chamber. The paper investigates thermal processes in the solar dryer affecting agricultural product drying. It is shown that the air solar collector integrated with paraffin wax, is a thermal energy storage, which provides the automatic control for temperature and humidity. Experiments with sliced bananas include the hot air supply provided by the thermal energy storage with or without the solar radiation. It is found that at least 7 hours after sundown, the dry air temperature is 2 to 7.5°C higher than the ambient air. [ABSTRACT FROM AUTHOR]

Phase-change materials have various applications across industries from thermal energy storage through automotive battery temperature management systems to thermal stabilisation. Many of these applications are shell and tube structures with different shell shapes. However, it is not yet known how the shape of the shell affects the melting, solidification times, and heat transport processes in such structures. To fill this research gap, seventeen shell shapes/orientations were compared using a simulation study. The well-known and validated enthalpy porosity algorithm implemented in the Fluent 2021R2 software was used. The numerical calculations were preceded by the measurement of thermal conductivity, phase change enthalpy, and specific heat during melting and solidification of the phase-change material. The shortest melting time was achieved for a semi-circular shell shape in the downward position, which was 44% shorter than the reference circular case. The shortest solidification times were recorded for an isosceles trapezium in an upward orientation relative to the reference circular case. Therefore, it is possible to significantly reduce the melting time in shell-and-tube systems as a result of the appropriate selection of the shell shape. [ABSTRACT FROM AUTHOR]

Modern energy batteries are mainly used in pure electric vehicles. The stability of battery operation relies heavily on thermal management systems for which phase-change batteries have become an effective solution. In this study, we designed a battery thermal management system divided into two parts: a shaped phase-change material (PCM) module and a battery module. In the qualitative PCM module, polyethylene glycol was used to absorb heat, expanded graphite (EG) was used as the thermally conductive agent, and copper foam formed the support skeleton. The battery module comprised an 18650 lithium-ion battery with an enthalpy of 155 J/g. In our experiments, we applied PCMs to the battery modules and demonstrated the effectiveness of composite PCM (CPCM) in effectively lowering the temperature of both battery packs and minimizing the temperature discrepancies among individual batteries. At a gradually increasing discharge rate (1C/2C/3C), the battery's Tmax could be lowered and the temperature could be de creased at various positions. It was evident that the battery temperature could be effectively preserved using CPCM. The findings of this study lay a foundation for future research on battery thermal management. Finally, the copper foam and EG contributed significantly to the prevention of leakage. [ABSTRACT FROM AUTHOR]

In this paper, we present the results of an experimental study of the controlled contrast of optical properties of Germanium Telluride (GeTe) and Germanium Antimony Telluride (Ge2Sb2Te5 or GST) 100 nm thin films, caused by laser-initiated reversible phase transitions from the amorphous-tocrystalline state, and vice versa. We demonstrate a high contrast in the transmissivity and reflectivity spectra in the wide wavelength range from 500 to 20,000 nm. We show that such a contrast of optical properties can be controlled in the set–reset mode, when samples of thin films are exposed to a nanosecond laser pulse at a wavelength of 532 nm, with a spatial distribution close to "top hat." We confirm the laser-initiated changes in the thin film structures by X-ray diffraction analysis methods. [ABSTRACT FROM AUTHOR]

Implementation of integrated, nonvolatile, and reconfigurable solutions for on‐chip terahertz (THz) metadevices holds great potential for applications in sensing, integrated circuits, and high‐speed communications. This study demonstrates the non‐volatile reconfigurable dynamic manipulation of THz on‐chip metadevices through optical modulation of Ge2Sb2Te5 (GST) and 2π phase shift of metasurfaces. The approach allows for the simultaneous realization of surface plasmons (SPs) excitation, wavefront shaping, and amplitude modulation in a single device. Using the principles of 2D holography, a reconfigurable multilevel THz SP metalens switch with a maximum extinction ratio of 29.9 dB is presented. The focusing intensity of the metalens can be continuously modulated by varying the pump laser energy. The implementation of the approach is further demonstrated by realizing a switchable THz SP varifocal metalens. Reconfigurable, reversible, and repeated switching is achieved through optical and thermal stimuli, resulting in switching contrast ratios of 7.4 dB and −44.4 dB in the amorphous and crystalline states of GST, respectively. The results demonstrate a promising route toward developing non‐volatile, reconfigurable, and energy‐efficient on‐chip THz integrated metadevices. By enabling the dynamic manipulation of THz waves on a single chip, the approach holds significant potential for advancing the field of terahertz‐integrated photonics. [ABSTRACT FROM AUTHOR]

Latent Heat Transfer Thermal Energy Storage (LHTES) units are crucial in managing the variability of solar energy in solar thermal storage systems. This study explores the effectiveness of strategically placing layers of anisotropic and uniform metal foam (MF) within an LHTES to optimize the melting times of phase-change materials (PCMs) in three different setups. Using the enthalpy–porosity approach and finite element method simulations for fluid dynamics in MF, this research evaluates the impact of the metal foam’s anisotropy parameter (Kn) and orientation angle (ω) on thermal performance. The results indicate that the configuration placing the anisotropic MF layer to channel heat towards the lower right corner shortens the phase transition time by 2.72% compared to other setups. Conversely, the middle setup experiences extended melting periods, particularly when ω is at 90°—an increase in Kn from 0.1 to 0.2 cuts the melting time by 4.14%, although it remains the least efficient option. The findings highlight the critical influence of MF anisotropy and the pivotal role of ω = 45°. Angles greater than this significantly increase the liquefaction time, especially at higher Kn values, due to altered thermal conductivity directions. Furthermore, the tactical placement of the anisotropic MF layer significantly boosts thermal efficiency, as evidenced by a 13.12% reduction in the PCM liquefaction time, most notably in configurations with a lower angle orientation.

A solar-powered combined cooling, heating, and power (CCHP) plant integrated with a water electrolysis unit is investigated in terms of energy, exergy, and exergo-economic (3E) assessments. A comprehensive parametric study and optimization is conducted following the thermodynamic and exergo-economic assessment of the proposed system to evaluate the key performance parameters of the system for efficiency and economic factors. This system employs a heliostat field and a receiver tower by taking advantage of thermal energy from the sun and produces a continuous energy supply with an integrated phase-change material (PCM) tank to store the heat. In addition, a supercritical CO2 Rankine cycle (RC), an ejector refrigeration cooling (ERC) system, and a PEM water electrolyzer are coupled to produce cooling, heating, power, and hydrogen. Thermodynamic analysis indicates that the system exergy efficiency and energy efficiency are improved to 33.50% and 40.61%, respectively, while the total cost rate is 2875.74 USD/h and the total product cost per exergy unit is 25.65 USD/GJ. Additionally, the system produces a net generated power, heating load, and cooling load of 11.70, 13.92, and 2.60 MW, respectively, and a hydrogen production rate of 12.95 g/s. A two-objective optimization approach utilizing a non-dominated sorting genetic algorithm (NSGA) was performed, demonstrating that the system’s ideal design point offers a cost rate of 1263.35 USD/h and an exergetic efficiency of 34.17%.

The preservation of perishable food items within the cold chain is a critical aspect of modern food logistics. Traditional refrigeration systems consume large amounts of energy, without an optimal temperature distribution, leading to potential food spoilage and economic losses. In recent years, the integration of Phase Change Materials (PCMs) into cold chain systems has emerged as a promising solution to address these challenges. This article presents a comprehensive analysis of the utilization of PCMs for food preservation in a refrigerated truck, focusing on the impact on temperature control, phase change fraction, costs, and energy savings. The effectiveness of PCM-based refrigeration system to maintain the refrigerated truck at a temperature of −18 °C under various scenarios and environmental conditions using a transient model was evaluated. The TRNSYS model includes a representation of a conventional refrigerated van’s system, with simulations conducted in a Mediterranean climate (Naples). The model’s core components consist of Type 56 for cooling load estimation and Type 1270a for the new PCM component. Results indicate that for guaranteeing −18 °C for 10 h, 96.4 kg and 102.2 kg of E-26 and E-29 PCM are needed, respectively, for scenarios with 10 door openings during transportation and for two different velocities of the truck: 30 and 80 km h−1. Results indicate that the incorporation of PCMs in the refrigerated van leads to significant improvements in temperature stability and uniformity, thereby extending the shelf life of perishable food products and reducing the risk of spoilage. Furthermore, the analysis shows that, using the PCMs, a significant reduction of the energy costs can be obtained (up to a maximum of around 79%).

Leakage is a high-incidence disease of embankment dams, and efficiently addressing this disease guarantees the safe operation of dams. Underwater leakage self-priming plugging technology is a new technology that utilizes the melting and solidifying characteristics of phase-change materials and the negative pressure in the leakage entry area to accurately plug the leakage. However, little is yet known about the underwater melting process of phase-change materials and how their characteristics influence the plugging effect. In this study, three kinds of phase-change materials, namely, paraffin, rosin, and stearic acid, were used to conduct underwater leakage self-priming plugging tests, observe and analyze the underwater melting process, and compare the plugging effects. The results showed that the underwater melting process of phase-change materials exhibited different plugging window periods depending on their melting points, specific heat capacities, and mobilities, which were the main factors affecting their plugging effects. In the final plugging stage, paraffin had the best plugging effect, but the material strength was low; rosin had good plugging compactness, but the fluidity performance was poor, and the material effective utilization was low; stearic acid had a low melting point but dispersed easily. Therefore, a blocking material with a suitable blocking window period can be produced by adjusting the material properties accordingly for an improved blocking effect.

Oscillatory neural networks (ONNs) exhibit a high potential for energy-efficient computing. In ONNs, neurons are implemented with oscillators and synapses with resistive and/or capacitive coupling between pairs of oscillators. Computing is carried out on the basis of the rich, complex, non-linear synchronization dynamics of a system of coupled oscillators. The exploited synchronization phenomena in ONNs are an example of fully parallel collective computing. A fast system’s convergence to stable states, which correspond to the desired processed information, enables an energy-efficient solution if small area and low-power oscillators are used, specifically when they are built on the basis of the hysteresis exhibited by phase-transition materials such as VO2. In recent years, there have been numerous studies on ONNs using VO2. Most of them report simulation results. Although in some cases experimental results are also shown, they do not implement the design techniques that other works on electrical simulations report that allow to improve the behavior of the ONNs. Experimental validation of these approaches is necessary. Therefore, in this study, we describe an ONN realized in a commercial CMOS technology in which the oscillators are built using a circuit that we have developed to emulate the VO2 device. The purpose is to be able to study in-depth the synchronization dynamics of relaxation oscillators similar to those that can be performed with VO2 devices. The fabricated circuit is very flexible. It allows programming the synapses to implement different ONNs, calibrating the frequency of the oscillators, or controlling their initialization. It uses differential oscillators and resistive synapses, equivalent to the use of memristors. In this article, the designed and fabricated circuits are described in detail, and experimental results are shown. Specifically, its satisfactory operation as an associative memory is demonstrated. The experiments carried out allow us to conclude that the ONN must be operated according to the type of computational task to be solved, and guidelines are extracted in this regard.

The paper chronologically describes the results of research on the flow of micro-encapsulated PCM (mPCM) and nano-encapsulated PCM (nPCM) slurry in heat-transfer systems. The focus is on three thematic groups: mPCM (nPCM) slurry flow pressure drop; the friction factor in the laminar, transient, and turbulent flow of slurry in the channels; and the assessment of the effectiveness of using the mPCM (nPCM) slurry in the context of improving heat-transfer coefficients but with increased pumping power. It was found that the number of publications devoted to the above-mentioned topics is very limited compared to the research on the thermal and rheological properties of the mPCM (nPCM) slurry, which has resulted in the lack of systematized knowledge about the influence of slurry concentration, particle size, materials, etc., for example, on the friction factor. It was found that the use of the mPCM (nPCM) slurry in heat-transfer systems may be proper, provided that an appropriate and sufficiently high flow rate is ensured. [ABSTRACT FROM AUTHOR]

Thermal heat storage is becoming important in systems with renewable energy sources. Their largest benefit is smoothing the intermittent production and reduction in the site peak demand. The advantages of thermal energy storage with phase-change material are storing energy at a lower temperature for reduction in thermal losses, and enabling energy transfer at a constant temperature, which reduces the risk of equipment damage. In this paper, a low-order model of latent thermal energy storage, derived in a state-space form by using the mixed logical dynamical approach, is proposed. The model is compared to a stratified model and shows significant improvements of physical accuracy and execution time. Finally, a model predictive control algorithm suited for the real case study is designed, implemented and compared to classical rule-based control. The obtained results show significant energy savings of 8.43%, and improvements in user comfort and equipment duration. [ABSTRACT FROM AUTHOR]

This article presents the use of phase-change material (PCM) thermal storage within the Horizon 2020 HEART project (Holistic Energy and Architectural Retrofit Toolkit), aimed at decarbonising the European building sector through the retrofitting of existing structures into energy-efficient smart buildings. These buildings not only reduce energy consumption, but also incorporate advanced technologies for harnessing green energy, thereby promoting environmental sustainability. The HEART project employs state-of-the-art technologies for electricity production/dispatching and heat generation/storage, managed by a cloud-based platform for the real-time monitoring of parameters and optimising energy utilisation, enabling users to control their environmental comfort. The article provides a detailed examination of one of the project's demonstration sites in Italy, focusing on various components such as heat pumps, photovoltaic systems (PV), controllers, and particularly emphasising the significance of storage tanks. The study involved the measurement and analysis of three heat storage tanks, each with a total volume of 3000 L. These tanks utilised PCM modules for latent heat storage, significantly enhancing overall heat accumulation. Water served as the heat transfer fluid within the tanks. Through meticulous calculations, the article quantifies the accumulated heat and presents a comparative evaluation between PCM-based storage tanks and conventional water tanks, showcasing the advantages of PCM technology in terms of increased heat retention and efficiency. [ABSTRACT FROM AUTHOR]

Composite phase-change nanofibers were prepared by electrospinning with polyethylene glycol (PEG) as the phase-change material (PCM) and polyvinylpyrrolidone (PVP) as the carrier matrix. The high PEG content endowed the nanofibers with an excellent cooling effect and significantly reduced the smoke temperature. For PEG70/PVP nanofibers, the smoke temperature can be decreased 45℃ at the 8th puff, and be kept below 45℃. The cooling test proved that the electrospun PEG/PVP phase-change nanofibers exhibited a desirable cooling performance, improving the comfort of cigarette products. And the composite PEG/PVP phase-change nanofibers present great potential as the cooling cigarette filter material for HnB tobacco application. [ABSTRACT FROM AUTHOR]

This paper explores the potential of thermal storage as an energy storage technology with cost advantages. The study uses numerical simulations to investigate the impact of adding porous material to the HTF side during solidification to improve the heat transfer effect of TES using AlSi 12 alloy as the phase-change material. The research also examines the effects of adding porous dielectric materials and increasing air velocity on the discharge temperature, discharge power, and discharge time of high-temperature phase-change energy storage systems. The study found that the temperature difference of the PCM (increased), solidification time (reduced more than 85%), the outlet temperature of the air, and heat discharge power of the LHS did not vary significantly across different porous materials (copper foam, nickel foam, and silicon carbide foam) added to the HTF tube. These findings offer important information for the design of high-temperature phase-change energy storage devices and can guide future developments in this field. [ABSTRACT FROM AUTHOR]

The wide application of lithium-ion batteries (LIBs) brings along with it various safety problems, such as fire and explosion accidents. Aiming at the thermal runaway (TR) and fire problems of LIBs, we reviewed the evolution of TR within LIB and the release of TR gases and their hazards, as well as the research progress in recent years in the area of fire separation of LIBs. To begin with, physical, electrical, and thermal abuse are the three main factors leading to TR and the thermal stability of aging batteries significantly deteriorates. Furthermore, the decomposition of the electrolyte and the reaction between the active materials generates CO, CO2, H2, HF, and a variety of hydrocarbons. These TR gases have serious toxic and explosive hazards. In addition, fire separation can effectively delay the occurrence and propagation of TR within LIB modules. As a good heat-absorbing material, phase-change materials are widely used in the thermal management system and have a great prospect of wide applications in the fire separation of LIBs. Finally, the research on the TR gases' hazards of aging LIB and safer and more effective fire separation are prospected. [ABSTRACT FROM AUTHOR]