Single Phase Change Materials Research Articles

Development of PCM tile for residential buildings in hot and dry climate: design and optimization

In recent years, the building sector has become more conscious of sustainability, and the use of phase change materials (PCMs) in concrete has gained more attraction. Integration of PCM with building facades is a successful method to reduce energy consumption and improve human comfort. However, no single PCM can work in an all-weather scenario. Hence, in this research work, an attempt is made to select a suitable PCM for Chennai city, India, and this methodology can be employed at any geographical location. The PCM tile is designed by including certain features to increase the thermal conductivity of the PCM zone. The optimum design of the PCM tile is achieved through multi-objective optimization techniques. L27 orthogonal array is employed, and all the tests were conducted through validated numerical simulation. Redesigned PCM tile includes a PCM layer of 2 cm thickness with a 10% mix of copper nanoparticles covered by plaster. Redesigned PCM tile reduces the peak indoor temperature by 6.62℃ compared with conventional roof systems.

Numerical study on the combined application of multiple phase change materials and gradient metal foam in thermal energy storage device

Latent heat thermal energy storage (LHTES) offers significant energy-saving benefits, but its application is limited due to the low thermal conductivity of phase change material (PCM). To address this issue, this article studied the combined application of metal foam structures with different porosity gradients and multiple PCMs with different melting points through numerical simulation to accelerate the melting of PCM and enhance system efficiency. The results showed that the application of multiple PCMs improved the heat transfer performance of the system, reducing the complete melting time by 9.18% compared to using a single PCM with uniform metal foam. Based on the multi-PCM storage system with an average porosity of 0.90, this article designed metal foam structures with one-dimensional and two-dimensional porosity gradients and explored their impacts. The results indicated that in the structure with a one-dimensional porosity gradient along the heat flow direction, the positive gradient decreased thermal resistance, further reducing the complete melting time by 6.18%, while the negative gradient increased it by 19.78%. However, the temperature non-uniformity was lowest with the negative gradient and highest with the positive gradient. The optimal two-dimensional porosity gradient multi-PCM storage model not only reduced thermal resistance but also effectively solved the issue of uneven melting, reducing the complete melting time by 17.96% and increasing the energy storage efficiency by 20.16% compared to the single PCM system with uniform porosity. Furthermore, the article conducted a dimensionless analysis of the optimal structure and different gradient structures, establishing formulas for the liquid fraction concerning modified Fourier number, modified Stefan number, and modified Rayleigh number.

Cascade Latent Heat Storage for Solar Cooking Applications

The present investigation explores the potential of multiple phase change material (PCM) based storage for real-time solar thermal applications. There are two types of storage configurations tested in this work for the simultaneous charging and discharging operation, i.e., single PCM-based NaNO3 storage and 2-stage cascade latent heat storage having NaNO3 and NaNO2 as the storage mediums in the consecutive stages. The storage is designed to achieve the end-use temperature condition of 513 K (the highest temperature required for cooking) with the latent thermal energy accumulation capacity of 1 MJ. The study envisages that instead of using a single PCM in the storage unit, 2-stage cascading of the PCMs can improve energy accumulation and retrieval in storage. After 8 hours of operation, none of the storage achieves the complete charging state. The energy accumulated in the NaNO3/NaNO2 cascade storage is found to be 2.6 times higher than the energy accumulated in the NaNO3 storage. NaNO3/NaNO2 storage achieves the desired constant outlet temperature of cold heat transfer fluid for chapati making (531 K) after 165 minutes of operation. At this moment, the latent energy accumulated in the NaNO3 and NaNO3/NaNO2 storage is observed as 35% and 14%, respectively

Development and Investigation of Nitrate Phase Change Filler Material for Solar Process Heating Applications

Thermocline thermal energy storage system is an imperial system for solar process heating applications. The thermal energy storage system comprises filler material and heat transfer fluid. In the present study, the commercial phase change material (PCM) (filler material) solar salt (60%NaNO3+40%KNO3) is synthesized, and it is encapsulated with a 1mm thickness of stainless steel 316L encapsulation with the macro-size of 60mm; the encapsulated PCMs is considered as a single particle in the thermocline thermal energy storage system. The performance of the single encapsulated PCM is studied with a constant heat transfer fluid (Therminol-VP1) flow rate of 0.00015 kg/s during the charging process. The specific heat of the solar salt is measured in Differential Scanning Calorimeter (DSC) in the solid phase is found as 1.381 J/gK, and liquid phase is identified as 1.551 J/g-K, the enthalpy during the phase change process is found as 116.72 J/g. As well, the thermal conductivity of the solar salt is measured in Transient Heat Conduction method, and the thermal conductivity follows the linear relationship of -0.0025(T)+0.4023 (45ºC<T<100ºC) in the sensible region. The temperature variations and the phase change phenomena for the solar salt is identified and the contours are provided. The charging time for the encapsulated solar salt is identified as ~138 minutes. The energy storage cost for the single filler material (Solar Salt + SS316L encapsulation) is identified as Rs.5.93/- (USD 0.071) for the period of charging duration.

Performance of a combined battery thermal management system with dual-layer phase change materials and air cooling technologies

Lithium-ion batteries are increasingly applied in electric vehicles, energy storage and more. In order to ensure its stable operation under different ambient temperature, an innovative battery thermal management system (BTMS) based on phase change material (PCM) has the dual-layer PCMs arrangement is proposed in this research. To prove the effectiveness of this structure, the temperature variation of lithium-ion battery 18,650 with single PCM and dual-layer PCMs arrangement is calculated and compared by numerical simulation. The findings reveal that the dual-layer PCMs arrangement proposed in this paper has better environmental adaptability at different ambient temperatures (Tamb). When the Tamb is 20 °C and the discharge rate increases from 1C to 5C, the maximum temperature (Tmax) of the battery under the dual-layer PCMs arrangement is 25.33 °C, 30.80 °C, 33.58 °C, 35.80 °C, 39.07 °C, respectively. And in response to the high ambient temperature and high discharge rate, the dual-layer PCMs layout is combined with air cooling to form a hybrid BTMS. The results show that Tmax of the hybrid BTMS is reduced by 21.5 % compared with the PCM-based BTMS when the Tamb is 40 °C and the discharge rate is 3C. The proposed hybrid BTMS with dual-layer PCMs structure controls the Tmax of the battery pack well and the temperature uniformity is also maintained within acceptable level, which has great application potential in battery thermal management.

Enhancing thermal comfort in buildings through the integration of phase change material on the building envelope: a simulation study

Abstract According to the report published by the International Energy Agency (IEA), active space cooling and air conditioning systems consume approximately 16% of the building sector’s final electricity consumption and contribute 3.94% of global greenhouse gas emissions. In this regard, the use of low-cost but effective passive solutions, such as organic phase change materials (PCM) on the building envelope, can provide high thermal mass and thus can lower the temperature fluctuation inside the building. In the current study, the potential of PCM-enhanced building envelopes to enhance thermal comfort has been studied. The study has been performed using the conduction finite difference (ConFD) algorithm in EnergyPlus software. A comparative study has been done for a traditional reinforced cement concrete (RCC) reference test room of size (5m x 6m x 3m) and another room of the same size with PCM-enhanced walls for the hot and humid climate zone of Guwahati (latitude 26.1, longitude 91.7), in India. A PCM thickness of 20 mm is used at the external surface of the wall between the red clay burnt brick (120 mm in thickness) and the cement plaster (25mm thick). The PCM used for the study is a biocomposite PCM, named WH-PCM, with a melting point of 31.5°C and thermal conductivity of 0.27 W/mK. The simulation results reveal that the R-value of the external wall of the room with PCM walls has been increased by 84.90% compared to the reference room with the incorporation of WH-PCM, resulting in a mean zone temperature difference of 0.3°C throughout the year. Also, the indoor thermal discomfort hours have been annually reduced by 15.82% with the use of WH-PCM when compared with the reference room. A similar temperature difference trend, which is 1.93°C, is also observed in the single PCM brick experimental result under identical testing conditions as a regular brick of the same size.

A numerical investigation of novel segmented PCM blocks filled with different phase change material cooling for Lithium-Ion battery

Phase Change Material (PCM) embedded systems have gained attention for their latent heat absorption and release capabilities in Battery Thermal Management. However, conventional PCM-cooled battery systems often exhibit low heat absorption rates, resulting in temperature irregularities and uneven melting. To overcome these challenges, this study introduces an innovative cooling system using segmented PCM blocks, each storing different types of PCMs. The PCM block is divided into three or four parts, employing distinct PCMs based on the observed heat propagation pattern during high-current discharging. A three dimensional numerical investigations are conducted in ANSYS Fluent using the MSMD battery model to explore three segmented and four segmented PCM blocks, comparing them with a single PCM block. The parametric variations considered in this work include varying PCM block thickness, PCM types, and discharging rates. Results show that increasing PCM thickness controls temperature rises but also raises the system’s weight. The study demonstrates that incorporating different PCMs in four segmented block maintains battery temperature at 319 K, with uniform distribution across the surface. The proposed PCM-based battery thermal management system reduces system weight by 17.84 % and enhances PCM heat absorption by 32.59 % compared to a conventional PCM block system when discharging at a high current rate of 4C to stay within the safe operating temperature range.

Energy assessment of a sliding window integrated with PV cell and multiple PCMs

Windows often serve as a thermal weak point between a room's interior and the outside world. As such, we are exploring a new design for a sliding window that integrates both multiple phase change materials (PCMs) and photovoltaic (PV) cells. During the day, the PV cells produce electricity, which can be used in the building during the night. The sliding mechanism introduces several innovative features: use the PV-PCM glass unit (as the external sliding layer) or a standard glass unit (the internal sliding component). The PV-PCM window also can be used as a sliding light shutter or curtain. The PV cell in the proposed design is operated in the closed and open case due to the sliding design. We compared the thermal performance of a single PCM type (either RT-35or RT-27) with a combination of multiple PCMs (RT-35-RT27). Further, we evaluated various thickness combinations of the multi-PCM configuration (RT-35-RT27), including 2.5mm–7.5mm, 5 mm–5 mm, and 7.5 mm–2.5 mm, to identify the best-performing setup. Over the course of a day, the multi-PCM setup (RT-35-RT27) maintains a consistently lower average interior wall temperature than using a single PCM. Among the configurations tested, the 5 mm–5 mm multi-PCM setup (RT-35-RT27) emerged as the most effective, displaying steadier results than the other variations. Compared to a standard single glass pane, the proposed PV-PCM window reduced the highest interior wall temperature by up to 46 % when employing multiple PCMs. As a result, we advocate for the adoption of this innovative sliding window in future building designs.

Mathematical model of the solar combined cycle power plant using phase change materials in thermal energy storage system (Thermodynamic analysis)

This research presents a novel mathematical framework for optimizing solar combined cycle power plants, with a particular emphasis on the exergy analysis of various superheating heat exchanger configurations used in thermal energy storage. The importance of phase change materials (PCMs) in improving the thermodynamic efficiency of solar combined cycle power plants is emphasized in this study. The investigation includes three configurations, two with a single PCM and one with two PCMs. The use of PCMs is intended to increase storage density, reduce volume, and maintain consistent temperatures, thereby favoring latent energy storage. The model developed evaluates exergy efficiency and output temperature profiles during the charging and discharging processes. The results show that the single PCM configuration has an impressive charging efficiency of 93.12 %, reaching an output temperature of 371 °C in 8 h. The two PCM configurations, on the other hand, achieve even higher efficiency at 94.89 % during charging, with an output temperature of 367 °C over a slightly longer 10-hour period. This comparison emphasizes the benefits of using two PCMs, demonstrating increased exergy efficiency and a marginal increase in output temperature over a single PCM setup. Furthermore, a comparison of the outcomes resulting from the use of a single type of PCM in exchangers reveals that the disparity in PCM melting temperatures causes only minor variations in the system's efficiency. The findings emphasize the significance of optimal PCM utilization for efficient solar energy retention, particularly during periods of low radiation.

Analytical modeling of phase change in a composite wall comprising two distinct phase change materials in series

Most of the past literature on solid-liquid phase change heat transfer modeling focuses on a single phase change material (PCM), whereas, a sandwich of two or more PCMs arranged in series may be of interest in several applications. The modeling of heat transfer and phase change in such a system is complicated by the presence of multiple phase change fronts propagating at the same time. This work presents a theoretical analysis of the problem of melting of a two-PCM stack being heated from one end. Depending on whether the lower-melting PCM is located next to or away from the heat source, two distinct cases are considered. The propagation of the phase change fronts in each case is divided into several stages, each of which is characterized by a distinct phase change and/or sensible heating processes. The transient temperature field in each stage is determined in the form of infinite series solutions, and the propagation of phase change front over time is then determined using energy conservation at the phase change interface. In this manner, explicit expressions are derived for the time taken for each layer to completely melt. Results are shown to be in good agreement with finite-element simulations, and with the exact Stefan solution under special conditions. Key non-dimensional parameters that influence the nature of the two-PCM phase change process are identified, and their impact on phase change performance is analyzed. Quantitative predictions are presented for the conditions under which both PCMs finish melting at the same time, which is a favorable outcome for efficient energy storage.

Dual-sided melting of a one-dimensional composite wall comprising two distinct phase change material (PCM) layers

Past literature on theoretical modeling of solid-liquid phase change heat transfer mostly addresses a single phase change material (PCM), whereas, a series combination of two or more PCMs is often used in practical applications. This work presents an approximate analytical model for the melting/freezing of a one-dimensional composite of two PCMs being heated/cooled from both ends. It is shown that up to three phase change fronts may simultaneously exist in this problem. In addition to direct melting/freezing from the respective walls, it is shown that each PCM may also melt/freeze due to heat transfer through the other PCM. Using a quasi-stationary assumption, temperature field during the multi-stage phase change process is approximated by solving a multilayer transient thermal conduction problem using eigenfunction expansion. Good agreement with numerical simulations, and with the Stefan solution for a special case is demonstrated. The impact of key non-dimensional parameters on performance metrics including total time for phase change is determined. A quantitative prediction of conditions leading to the thermodynamically favorable situation of simultaneous completion of phase change of two commonly used PCMs is carried out. This work improves the theoretical understanding of phase change in composite PCMs, leading to optimization of practical thermal systems.

Reduced Graphene Oxide/Cellulose Sodium Aerogel-Supported Eutectic Phase Change Material Gel Demonstrating Superior Energy Conversion and Storage Capacity toward High-Performance Personal Thermal Management.

By virtue of their capacity to absorb and release energy during the phase change process, phase change materials (PCMs) are ideal for personal thermal management (PTM). The combination of reduced graphene oxide/cellulose sodium aerogel (rGCA) and lauric acid/myristic acid binary eutectic phase change gel (LMG) creates a composite phase change material that possesses outstanding photothermal conversion capabilities, electro-thermal conversion capabilities, energy storage capabilities, and shape-stable performance. The results showed that rGCA had a maximum adsorption efficiency of 99.7% with a melting latent heat of 124.6 J g-1. The high absorption rate of rGCA to LMG is a result of the capillary force, pore characteristics, hydrogen bonding, and the π-π interaction. Notably, rGCA and LMG composite material (rGCG) exhibited an excellent photothermal conversion efficiency of 96.5% and electro-thermal conversion of 82.3%. Results indicate that binary eutectic phase change materials are more suitable for temperature regulation than single phase change materials, making them more suitable for PTM. It is anticipated that the innovative thermal comfort solution, which provides thermal shielding, thermal energy storage, self-supporting characteristics, and wearability, will offer new possibilities for the next generation of wearable PTMs.

Numerical Investigation of Thermal Energy Storage Systems for Collective Heating of Buildings

This study aims to investigate and identify the most effective thermal energy storage (TES) system configuration for the collective heating of buildings. It compares three TES technologies, i.e., sensible, latent, and cascade latent shell and tube storage, and examines their respective performances. A fast and accurate lumped thermal dynamic model to efficiently simulate TES system performances under different operation conditions is developed. The validation of this model’s accuracy is achieved by aligning numerical findings with data from prior experimental studies. Key findings indicated that the latent and cascade latent shell and tube storage systems demonstrate superior thermal energy storage capacities compared to the sensible configuration. Using a single-phase change material (PCM) tank increases the duration of constant thermal power storage by about 50%, and using a cascade PCM tank further enhances this duration by approximately 65% compared to the sensible TES case. Moreover, the study revealed that adjusting the PCM composition within the cascade TES significantly influenced both thermal power storage durations and pumping energy consumption. In summary, the recommended cascade PCM configuration for collective heating of buildings offers a balanced solution, ensuring prolonged stable thermal power production, elevated HTF outlet temperatures, and improved energy efficiency, presenting promising prospects for enhancing TES systems in district heating applications.

Performance investigation and optimization of latent heat exchanger with pin fins based on non-uniform deployment strategy

Latent heat storage technology is an essential way of efficiently utilizing industrial residual heat, which helps to the objective of carbon neutrality in all countries. In this work, latent heat exchangers with pin fins are numerically investigated based on non-uniform deployment strategy and then optimized according to response surface method. The influences of rotation angle, non-uniform fin pitch, non-uniform fin length and combination of phase change materials with different melting temperatures on thermal storage performance are studied. Results show that the increment of rotation angle facilitates the reduction of complete melting time, and the optimal angle accelerates the melting speed by 10.3% compared to the 0° angle. The arrangements of gradually decreasing fin pitch and gradually increasing fin length along flow direction of heat transfer fluid improve the heat storage performance, which can reduce the complete melting time by 7.3% and 22.2% respectively, compared to the uniform arrangement. The multiple phase change materials latent heat exchanger with high melting temperature phase change material placed in high temperature region and low melting temperature phase change material in low temperature region can make better utilization of heat from heat transfer fluid, which can improve the melting speed by 16.8% compared with the single phase change material latent heat exchanger. The optimized latent heat exchanger based on response surface method reduces the complete melting time by 23.4% compared to the original model. In conclusion, the heat storage performance of latent heat exchanger with pin fins effectively improved by adopting the non-uniform deployment strategy.

The Influence of Composition Ratio on the Thermal Performance Parameters of Eutectic Phase Change Materials: Experimental Research and Theoretical Prediction

Eutectic phase change material (EPCM), compared with single phase change material (PCM), is widely studied by many scholars due to its flexibility in practical engineering applications by the characteristic of changing phase change temperatures. However, there is still a lack of theoretical prediction research on the thermal performance parameters of EPCM. The existing theories about EPCM are unable to accurately predict its thermal performance parameters, which increases the difficulty of selecting the composition ratio of EPCM and affects its practical application. Based on a background of the accurate prediction of EPCM thermal parameters, 12 binary EPCMs, and 7 ternary EPCMs are prepared by mixing capric acid, n-octanoic acid and tetradecane with different proportions, respectively. By using the cooling curves and DSC test, the variation patterns in thermal performance parameters of EPCMs are studied. After comparing various thermodynamic models, the Schrader model was selected and combined with experimental results to compare and calculate the experimental and theoretical values of thermal performance parameters. The results show that the binary PCM reaches the minimum eutectic point of 1.42 °C at a mass ratio of 0.33:0.67 for capric acid to n-octanoic acid, while the ternary PCM reaches the minimum eutectic point of 0.34 °C at a mass ratio of 0.231:0.469:0.3 for capric acid, n-octanoic acid, and n-tetradecane. The latent heat of a EPCM is between the lowest and highest values of the latent heat of the constituent components, and its value increases with the enhancement of the overall thermal storage density of the material. The modified Schrader equations can effectively predict the phase change temperatures and latent heats of EPCMs at different composition ratios. The equation has a fitting accuracy of over 0.986 and a bias error of less than 6%, demonstrating excellent accuracy and providing a reliable theoretical basis for the proportion design and thermal parameter prediction of EPCM in actual engineering applications.

A new thermal management figure of merit for design of thermal energy storage with phase change materials

Phase Change Materials (PCMs) are frequently employed in thermal management of systems with high heat fluxes because their high latent heat of phase change limits transient temperature rises and damps temperature fluctuations. In general, detailed numerical analysis is used to design such systems. However, for an efficient thermal design process, it is desirable to have an analytic method to perform a quick quantitative comparison between all the available PCMs considering potential design configurations. The previously developed Figure of Merit (FoMc) for PCMs only depends on the thermophysical properties of the PCM and does not account for other relevant information such as geometry, melting temperature, and boundary condition. In the present work, we develop a novel performance factor (f) that works in conjunction with the material property based FoM to gauge the performance of different PCM-based thermal management systems (TMSs). The performance factor f is based on the characteristic timescales for thermal diffusion and thermal storage in a PCM system. First, this work demonstrates the range of applicability of our new FoM (fFoMc) for various PCMs (3 metallic, 4 organic, and 3 inorganic materials) across different geometrical and boundary configurations. The PCM performance is evaluated using transient numerical simulations with the metric of the maximum temperature rise in the domain after a fixed heating time. For a single PCM in different geometries, the maximum temperature rise decreases with increased f. For a general PCM-based TMS (i.e., a random combination of PCM, geometry, and boundary condition), the maximum temperature rise generally decreases with increasing the newly proposed FoM (fFoMc). Second, we extend the analysis to a composite PCM (an aluminum foam impregnated with organic PCM) to estimate the optimum porosity (ϕopt) for different geometric configurations. The analytically estimated ϕopt agrees well with the values calculated from optimizing detailed finite element simulations. Furthermore, this approach can explain the effect of expected duration of the PCM use on the ϕopt value using the proposed FoM. Overall, the proposed approach can identify the best performing geometrical configuration for a certain PCM or shortlist best performing PCM for a given setup of PCM-based TMS without detailed numerical simulations, making the design process more efficient.

Numerical study on thermal resistance of PCMs incorporated in novel roof structures against energy loss

Incorporating Phase Change Materials (PCM) into building enclosures is one of the passive techniques to improve thermal comfort and reduce energy costs. The present study is dedicated to the assessment of various configurations of PCM incorporation in a roof structure in order to evaluate their impact on thermal resistance and consequent reduction in energy losses. Several arrangements of the PCM and brick are tested: small PCM blocks distributed through the structure, multiple long PCM blocks distributed horizontally or vertically, single PCM block occupying either the right half or the left half, and single PCM block occupying the top half or bottom half. The equations governing the flow and thermal transfer in the PCM, as well as heat transfer in the plaster and brick, are defined and derived in the non-dimensional form. The hydro-thermal behavior of the melting PCM is assessed in the different configurations and for two values of Rayleigh number. The results indicate that for low Ra, the highest thermal resistance is obtained when a single PCM block is located at the top of the cavity and separated from the hot source by brick. For high Ra, the maximum resistance is found when the PCM is placed in multiple vertical blocks. Putting the PCM in multiple horizontal blocks or in small blocks does not change the PCM melting when Ra is varied. In all cases, the fastest PCM melting is obtained when the PCM block is close to the hot source and is either in one single block or in multiple vertical blocks.

Adaptive machine learning based control of multi-temperature, multi-module latent thermal storage ensembles

Phase change material thermal energy storage systems can be used to alleviate disparities in renewable energy supply and demand. Performance of such systems can be enhanced using a cascade of multiple phase change materials but efficiency benefits currently rely on precise optimization of design parameters. Therefore, there is motivation to develop storage technologies which provide greater flexibility for applications with dynamic operating conditions. In this study, a novel system is proposed called a multi-temperature, multi-module ensemble which consists of multiple phase change materials combined in series and parallel configurations. The system is optimized and controlled by an artificial neural network trained using a multi-objective optimization scheme. The performance for the novel system is compared to two baseline systems: a single phase change material system and a cascaded system. Across a wide range of fixed operating conditions, the results show that the ensemble reduces the rate of exergy destruction by 60% compared to the single module system and achieves a 10 °C improvement in performance for matching target outlet temperature compared to the cascaded system. Over a dynamically changing load profile, the results show that the multi-temperature, multi-module ensemble with artificial neural network controller is the preferable design as it achieves the excellent exergy efficiency of a cascaded system while maintaining the flexibility needed to respond to dynamically changing operating conditions. Furthermore, this novel approach widens the potential applications of latent thermal energy storage by providing a means to standardize manufacturing to drive down system cost and allowing the system to adapt to unforeseen design parameters.

Thermal analysis of a cascaded latent thermal storage tank in a solar domestic water heating system

AbstractTo enhance the thermal characteristics of a solar collector storage system, this study investigates the performance of a rectangular thermal energy storage (TES) tank by incorporating cascade phase change materials (cascade‐PCMs). Three different commercially available PCMs (RT44HC, RT54HC, and RT62HC) with distinct melting temperatures are employed. These cascade‐PCMs are utilized as slabs in vertical rectangular modules, which are integrated into the water TES tank. The heat transfer fluid (HTF) in the flat‐plate solar collector captures solar energy and transfers it to the TES tank, where it is stored as latent thermal energy. A two‐dimensional (2D) numerical model, utilizing the enthalpy‐porosity approach and conservation equations, is developed to analyze the melting and heat transfer processes within the TES tank. The model is validated against previous experimental and numerical data. Performance evaluation of the cascade‐PCMs tank is conducted during a 9‐h charging period (from 8:00 am to 5:00 pm) under Marrakesh weather conditions in Morocco. An optimization study is carried out to determine the optimal height of each cascade‐PCM. The results suggest that an optimal design with heights of 23, 16, and 11 cm for RT44HC, RT54HC, and RT62HC respectively, offers improved melting and storage quality. The thermal characteristics of the TES tank incorporating cascade‐PCMs are compared to those of a TES tank filled with a single phase change material (single‐PCM) during the charging period. The findings indicate that the cascade‐PCMs achieve complete melting, while the single‐PCM only reaches a melting fraction of 0.903 at the end of the charging process. Furthermore, the optimal configuration of the cascade‐PCMs storage tank exhibits slightly higher sensible and latent thermal energy storage capacity compared to the single‐PCM tank. The combination of the solar collector with the cascade‐PCMs storage tank results in a 3.47% higher average collection efficiency when compared to the single‐PCM tank.

Self-Adaptive Multistage Infrared Radiative Thermo-Optic Modulators Based on Phase-Change Materials

Phase-Change Materials (PCMs) are widely applied in dynamic optical modulation due to the dramatic changes in their complex refractive index caused by temperature variation. As the functionality varies, the application of a single PCM cannot meet the compact, efficient and broadband needs of optical modulators. In this work, we combine vanadium dioxide (VO2) and a chalcogenide (Ge2Sb2Te5 (GST) or In3SbTe2 (IST)) to obtain a VO2–GST/IST multiple-stack film that is optimized by a genetic algorithm. This film has a wide spectrum and high modulation properties with three self-switchable modes varied by temperature, including transmission, absorption and reflection. The optimal results are an average normal transmittance, absorbance, and reflectance of 0.76, 0.91, 0.86 in 3–5 μm and 0.72, 0.90, 0.90 in 8–14 μm under different temperature ranges. The film enhances the transmission and absorption properties due to the formation of anti-reflective coating and Fabry–Perot resonance. Compared with GST, the film maintains high reflectance due to the metal-like interface reflection of crystalline IST, which exhibits metallic properties. For different polarization states, the film demonstrates great directional insensitivity when the incidence angles vary from 0° to 60°. The designed self-adaptive multistage infrared radiative thermo-optic modulator has promising implications for optical fuse, fiber-optic communication and energy storage fields.