Hybrid Phase Change Materials Research Articles

Transmission/reflection/absorption individually control multifunctional metasurfaces

We propose a metasurface based on hybrid phase change materials GeTe and vanadium dioxide (VO2), which can manipulate the transmission /reflection /absorption of terahertz waves independently. By changing the external temperature from 25°C to 160°C, the function of this structure can be dramatically changed. When VO2 is in a dielectric state (i.e. 25°C), the designed structure behaves as a transmission-mode terahertz vortex beams manipulator. When VO2 is in a dielectric state (i.e. 68°C), the proposed structure serves as a reflection-mode terahertz vortex beams controller. When GeTe is in crystalline state (i.e. 160°C), the designed structure becomes as a terahertz perfect absorber at a frequency of 1.98THz within the incident angle of 30°. The proposed structure provides a new method toward the use of multifunctional terahertz devices for their potential in applications including terahertz wireless communication and detection.

Vertical orientation graphene/MXene hybrid phase change materials with anisotropic properties, high enthalpy, and photothermal conversion

Vertical orientation graphene/MXene hybrid phase change materials with anisotropic properties, high enthalpy, and photothermal conversion

Performance analysis of a novel hydrogen production system incorporated with hybrid solar collector and phase change material

In this technical article, a novel experimental setup is designed and proposed to produce a hydrogen by using solar energy. This system comprises a hybrid or photovoltaic Thermal (PVT) solar collector, Hoffman's voltameter, heat exchanger unit and Phase Change Material (PCM). The effect of PCM and mass flow rate of water on the hybrid solar collector efficiency and hydrogen yield rate is studied. This experimental results clearly showed that by adding the thermal collector with water, decreases PV module temperature by 20.5% compared with conventional PV module. Based on the measured values, at 12.00 and 0.011 kg/s mass flow rate, about 33.8% of thermal efficiency is obtained for water based hybrid solar collector. Similarly, by adding Paraffin PCM to the water based thermal collector, the maximum electrical efficiency of 9.1% is achieved. From this study, the average value of 17.12% and 18.61% hydrogen yield rate is attained for PVT/water and PVT/water with PCM systems respectively.

Shape-stable and fire-resistant hybrid phase change materials with enhanced thermoconductivity for battery cooling

Thermal safety issues related to the thermal runaway problems in Li-ion batteries have been greatly concerned due to their wide applications. In this study, a low-cost and facile strategy for Li-ion battery thermal management was enabled by packing hydrated salt into organic paraffin and further stabilization of the composite by adsorption into a porous supportive material (expanded graphite, EG). The resultant composite phase change material (HPC@EG) demonstrated good shape stability and enhanced thermal conductivity (TC, 1.53–4.35 W m−1 K−1 at EG loadings of 5–15 wt%). HPC@EG also exhibited high latent heat (196.6 J/g) with sustained thermal storage performance over at least 500 heating / cooling cycles. The favorable performance of HPC@EG resulted from the paraffin acting both as a sealant and nucleating agent for the hydrated salt and as a co-phase change material, and the contribution of EG to the shape-stability and thermal conductivity. An added advantage of using hydrated salt and EG was their intrinsic fire-resistance which was also inherited by the HPC@EG composite. Such a combination offered effectiveness in preventing overheat of Li-ion batteries as we demonstrated, showing great promise in Li-ion battery thermal management in respect of price, safety and the cooling performance.

Role of phase change materials thickness for photovoltaic thermal management

The efficiency of photovoltaic (PV) panels plummet due to its escalating surface or operating temperature. Knowing this fact, the thermal regulation of PV panels is inevitable. Passive cooling techniques i.e. using phase change material (PCM) has gained attention in recent years for thermal regulation of PV panels. The present study investigates the performance of PV panels by varying thickness of hybrid PCMs in the climate of Taxila, Pakistan. The two PCMs having various melting points, kept apart by an aluminum plate were placed on rear side of PV module. The performance of three different configurations (B, C, D) of PV panels containing various thickness of hybrid PCMs was measured with respect to configuration A which was subjected to natural cooling. The PV panel configuration that has more amount of low melting point PCM as compared to other PCM showed better performance. It was witnessed that average reduction in temperature for configurations ‘B’, ‘C’ and ‘D’ were 4.9 °C, 6.5 °C and 8.1 °C respectively in comparison to configuration “A”. Also, increment of electrical efficiency for these three configurations were observed as 5.0%, 6.1% and 7.8% respectively due to enhancement in electrical power of PV panels. The configuration “D” having highest thickness of low melting PCM indicated best results in the sense of electrical power and electrical efficiency as compared to the other two configurations B and C having high melting PCMs.

Flexible and foldable composite films based on polyimide/phosphorene hybrid aerogel and phase change material for infrared stealth and thermal camouflage

Infrared stealth technology plays a vital role in development of defense industry and new military equipment. The current study focused on a novel type of flexible and foldable composite films based on polyimide (PI)/phosphorene (PR) hybrid aerogel and phase change material (PCM) for infrared stealth and thermal camouflage applications. The composite films were successfully obtained by fabricating a PI/PR hybrid aerogel through prepolymerizaton, film casting, freeze-drying, and thermal imidization, followed by vacuum impregnation of polyethylene glycol (PEG) as a PCM into the aerogel framework. The combination of PI and PR nanoflakes endows the hybrid aerogel with an effective enhancement in mechanical properties, near infrared absorption, and infrared photothermal conversion. The resultant composite films not only present prominent tensile and fatigue-resistant performance but also exhibit a good thermal regulation capability with a high latent-heat capacity of over 150 J/g. More importantly, the composite films demonstrate good infrared stealth and thermal camouflage performance on the high-temperature targets through effective thermal buffer and insulation. With ultralight, flexible, foldable, shape-tunable, and thermal self-regulatory characteristics, the PI/PR aerogel/PEG composite films developed by this work exhibit great application potential in infrared stealth and thermal camouflage for new military equipment.

Near-IR reconfigurable 1D Ag grating Fabry-Perot absorber hybridized with phase-change material GSST.

Chalcogenide phase-change materials (PCMs) offer a unique feature that can be used to dynamically control the response of the photonic devices and achieve fast, nonvolatile, reversible, multilevel, and specific optical modulation. The phase-change material Ge2Sb2Se4Te1 (GSST) has recently received a lot of attention due to the large index contrast between its amorphous and crystalline states with significantly low optical loss in the optical to near-IR spectrum. In this paper, we propose a tunable and reconfigurable hybrid PCM plasmonic nanostructure composed of a spacer layer of GSST sandwiched between a Ag back reflector and a 1D Ag Fabry-Perot grating structure. We use the finite element method (FEM) to numerically calculate the light absorption, absorption contrast, and figure of merit of the plasmonic nanostructure for both the amorphous and crystalline state of the GSST. Our calculations show that with constant structural variation the observed multimode absorption is drastically modified when the GSST undergoes a phase change from the amorphous to the crystalline state. The absorption contrast spectrum, which is defined as the absorption difference between the amorphous and crystalline state of GSST, shows four extrema modes between 70% and 89%. The figure of merit spectrum shows two large values of 44.39 and 37.78 at the 1502 nm and 2063 nm wavelengths, respectively. We also address the observed modes in the absorption contrast spectrum through spatial representation of the enhanced electric field distribution at their corresponding wavelengths. We show how the phase change in the GSST spacer can control the coupling between the optical cavity modes and the Ag surface plasmon resonance modes in the cavities and GSST spacer strip boundaries. The findings in this paper may open new avenues toward the design of next-generation photonic systems such as thermal emission controllers, sensors, ranging holograms, modulators and optical detection devices.

Phase change dynamics in a cylinder containing hybrid nanofluid and phase change material subjected to a rotating inner disk

In this numerical study, the phase change dynamics of a 3D cylinder containing hybrid nanofluid and phase change material (PCM) is investigated with a finite element solver. The PCM consists of spherical encapsulated paraffin wax, and the flow is under the forced convection regime. The dynamic features of the phase change process are studied for different values of the Reynolds number (between Re=100 and 300), the rotational Reynolds number of the inner disk (Rew=0 and 300), and the size of the rotating disk (length between 0.1L and 0.55L; height between 0.001H2 and 0.4H2). The flow dynamics and separated flow regions are found to be greatly influenced by the rotational speed and size of the inner disk. As Re is increased, the difference between the transition times at different rotational disk speeds decreases. At Re=100, a 21% reduction in the phase transition time is observed when the inner disk rotates at the highest speed as compared to the motionless case. Up to a 26% variation in the phase transition time occurs when the size of the inner rotating disk is varied. A 5 input-1 output feed-forward artificial neural network is applied to achieve fast and reliable predictions of the phase change dynamics. This study shows that introducing rotational effects can have a profound effect on the phase change dynamics of a hybrid nanofluid system containing phase change material.

Controlling the melting and solidification points temperature of PCMs on the performance and economic return of the water-cooled photovoltaic thermal system

The use of phase change materials (PCMs) in photovoltaic-thermal systems (PVT) is essential for developing PV systems and raising their productivity. PCM is distinguished by its many variations and properties, the most important of which is the melting point. In this study, the driven question and focus was on investigating which is better for use in a PVT, PCM systems with a high or low melting point? Two types of PCM were used in the study: paraffin wax (melting point 45 °C), Vaseline -petroleum jelly (melting point of 25 °C), and hybrid PCM (mixtures of the two PCMs in proportions of 25%, 50% and 75%). The study was conducted indoors by simulating the harshest condition in Iraq's weather in summer. The results showed that the wax and the Vaseline mixed entirely with an apparent decrease in the product's melting point.In contrast, the rest of the thermophysical properties of the product were relatively affected. The use of paraffin, petroleum jelly and 50% paraffin + 50% Vaseline in the PVT system caused a decrease in the surface temperatures of the photovoltaic cell, which resulted in a more significant improvement in the performance of the system. The maximum electrical efficiency reached was 13.7%, while the maximum thermal efficiency was 39.0%. Reducing paraffin melting point leads to better performance of PVT systems, as the hybrid paraffin (50% wax + 50% Vaseline) have better productivity than pure paraffin wax due to its lower melting point.

Experimental investigation of novel hybrid phase change materials

The novel potential of hybrid phase change materials (PCM) as a mix of animal fat, specifically pork fat (lard), with edible and waste oil from the food processing industry was investigated in this paper. Lard is a relatively accessible phase change material of organic origin, with a significantly lower unit price when compared to conventional PCM materials (wholesale price of lard can be less than 0.50 €/kg). On an annual basis, a large amount of lard is thrown away because it has become inedible from a nutritional point of view. Experimental results directed that the addition of oils can improve the thermal constants of lard such as thermal conductivity, volumetric heat capacity, with the thermal diffusivity being reduced. The best result was achieved for a hybrid PCM as a combination of pork fat and waste burnt oil as the thermal conductivity was improved by 1.4% and the volumetric heat capacity by 11% with respect to the base PCM, i.e., pork fat (lard). The novel proposed hybrid PCMs are more economically viable, enabling the utilization of waste resources, and securing less environmental impact when compared to conventional PCMs as organic materials. The possible application of lard should be further investigated for specific engineering applications, such as thermal energy storage.

A comprehensive optimization of phase change material in hybrid application with solar chimney and photovoltaic panel for simultaneous power production and air ventilation

Ventilation process is a significant requirement of healthy life-style and its importance was further highlighted through the recent Covid-19 global outbreak. Solar chimney is a natural indoor air ventilator without the requirement of any electricity power consumption. Hybrid solar chimney, photovoltaic panel, and phase change material (SC-PV-PCM) is investigated in this study (see graphical abstract) as the most recent newly proposed technology which is able to provide simultaneous natural ventilation and electricity in an effective manner. The contribution of this research is to identify the most efficient characteristics of phase change material (PCM) for this unique application using a comprehensive 3D validated numerical simulation. It is note that, the desirable phase change material should be able to enhance the efficiency of the ventilation process and power generation simultaneously. Hence, in order to reach the aim of this research, the impact of many effective parameters of phase change material including conductivity, melting point, heat capacity, and its enthalpy on both ventilation features of the solar chimney and electrical efficiency of solar panel is investigated for the mentioned (SC-PV-PCM) hybrid technology. Besides, the economic characteristics of the above system is evaluated as well. The simulation is performed under transient real weather conditions of Hong Kong (solar radiation intensity, ambient temperature, sky temperature, and wind speed) through the month of June from sunrise until sunset.

Impact of energy storage of new hybrid system of phase change materials combined with air-conditioner on its heating and cooling performance

The influence of thermal energy storage (TEGS) of coupling new hybrid system of two phase change materials (PCMs) with air conditioning (A/C) unit on its cooling and heating performance in summer and winter, respectively is investigated. PCM RT 10 HC (PCM10HC) of 10-12°C phase change temperature and PCM type SP 24E (PCM24E) of about 24-25°C phase change temperature suitable for working on winter and summer climate conditions, respectively are integrated as a hybrid system and coupled with the condenser/evaporator of the A/C unit. The performance of the A/C unit of this hybrid system is compared with the unit performance using only PCM24E system in summer and PCM10HC system in winter. The study is studied at two configurations of the hybrid PCMs system. The studied physical systems are modeled by a complete mathematical model that is numerically solved by utilizing ANSYS-Fluent software. The solution numerically is validated by using an experimental setup which shows the high accuracy of the numerical solution. The findings based on the stated design conditions of Egypt demonstrate that the time of complete charging and discharging procedures is nearly the same for hybrid and single PCMs systems. The maximum increase of the A/C unit COP is about 88% for the hybrid system in summer while it is nearly 22% in winter. The percentage increase of the saving power for the single system, the hybrid system is about 6.85%, and 6.5%, respectively in summer and 3.9% and 2.8% in winter, respectively compared to A/C without PCM units. Increasing the distance between the PCMs’ plates impacts negatively on the exit air temperature from PCMs plates and the saving power. The results demonstrate that the hybrid system has nearly the same merits on the A/C working as the single systems plus it can work during the hot and cold climate conditions.

Artificial Synapse with Mnemonic Functionality using GSST-based Photonic Integrated Memory

Here we present a multi-level discrete-state nonvolatile photonic memory based on an ultra-compact (<4μm) hybrid phase change material GSST-silicon Mach Zehnder modulator, with low insertion losses (3dB), to serve as node in a photonic neural network. Emulating an opportunely trained 100 × 100 fully connected multilayered perceptron neural network with this weighting functionality embedded as photonic memory, shows up to 92% inference accuracy and robustness towards noise when performing predictions of unseen data.

Avoiding thermal runaway propagation of lithium-ion battery modules by using hybrid phase change material and liquid cooling

In order to maintain the proper operating temperature and avoid thermal runaway propagation of lithium-ion power battery module, this paper proposes a novel hybrid battery thermal management system based on phase change material (PCM) and liquid cooling. In the proposed system, the operating temperature of the battery is maintained mainly by latent heat of PCM. In the case of thermal runaway condition, PCM acts as a heat buffer, and the heat dissipates through the liquid cooling system to avoid the thermal runaway propagation. The heat transfer model and the thermal runaway model are established and then verified. The performance of system is numerically analyzed under extreme operating and thermal abuse conditions. The results show that the proposed system combines the advantages of PCM and liquid thermal management schemes, which can fully meet the heat dissipation demand under extreme operating conditions. The high thermal conductivity of PCM is beneficial to the reduction of battery temperature but may cause thermal runaway propagation. The proposed system also have good heat dissipation capacity in avoiding the thermal runaway by optimizing some parameters, such as thethermal conductivity of PCM and water velocity.

Optimization of Thermal Conductivity of NanoPCM-Based Graphene by Response Surface Methodology

Common phase change materials (PCMs) possess very low thermal conductivity whilst hybrid PCM with graphene filler could be produced to achieve increased thermal conductivity. This research focuses on the effects of graphene flakes on the thermal conductivity of a PCM (paraffin wax). Three experimental parameters at different levels of average lateral sizes of graphene flakes (4.5, 5 and 7µm), mass fractions (0.1, 0.2 and 0.25 wt.%), and rising temperatures (25-75°C) are considered. For the first time in the literature, the impact of various parameters on the thermal conductivity performance of the nanoPCM-based graphene nano-composites is investigated extensively by adopting response surface methodology supported by central composite design. Thermal conductivity prediction is proposed by a new general correlation and a promising value of the coefficient of determination (R2) higher than 0.88. Amongst the investigated various variables in terms of impact on thermal conductivity, the temperature is identified as the most influential parameter on response variables. According to the implemented optimization technique, for the composite with the average graphene flake size of 4.5 µm, the optimum value of the thermal conductivity is found 0.275 W/m K at the mass fraction of 0.186 wt.% and temperature of 69.73°C.

The effect of using hybrid phase change materials on thermal management of photovoltaic panels – An experimental study

The temperature regulation of photovoltaic (PV) modules using passive approach with phase-change materials (PCMs) has fascinated many researchers now-a-days. This article presents real-time experimental investigation of PV panels with PCM under warm climate of Taxila, Pakistan in two phases. In first phase, effect of fins inserted into PCM, is examined by varying number of fins as 2, 5, 8 and 11. Due to improved heat conduction within PCM through metal contact, PV cell temperature lowered by maximum 22.9 °C, 23.7 °C, 24.1 °C, 24.9 °C and 26.5 °C with finless, 2-fin, 5-fin, 8-fin and 11-fin PV/PCM configurations respectively, improving electrical conversion efficiency from 10.2% to 10.9%, 11.3%, 11.6%, 11.8% and 12.2% respectively. In second phase, effect of using 2 PCMs of different melting points, separated by finned-aluminum plate, is investigated and compared with one PCM for PV cooling. It is found that one PCM configuration is more efficient than two PCM configurations as cell temperature lowers on average by 9.7 °C, 7.9 °C and 7 °C with one PCM configuration and two different configurations (i.e. different order) of 2 PCMs respectively. Electrical power output also enhances by 13.3%, 8.8%, and 7.8% respectively. 2-PCM configurations shows better performance than 1-PCM configuration in case only when it is compared to 1-PCM configuration having PCM of higher melting point. Order of PCMs has no significant effect on PV-performance.

Facile fabrication of shape-stabilized polyethylene glycol/cellulose nanocrystal phase change materials based on thiol-ene click chemistry and solvent exchange

How to realize large-scale manufacture of phase change materials (PCMs) with high latent heat storage and excellent shape stability is still a great challenge. Recently, encapsulating PCMs with three-dimensional porous structure is of great interest due to its excellent leak-proof ability and large latent heat storage capacity. However, the conventional fabrication techniques of 3D supporting skeletons for loading PCMs commonly involves hydrothermal process, freeze-drying and vacuum impregnation, which is difficult to operate and costly for large-scale manufacture. Herein, a facile and novel strategy for the potential large-scale manufacture of 3D porous structure supported PCMs is presented. This strategy involves two steps: rapid preparation of a novel CNC hydrogel based on UV-induced thiol-ene click chemistry and direct impregnation of PEG PCMs into the CNC hydrogel using solvent-exchange strategy for the first time. The structure and properties of CNC hydrogels and PEG/CNC hybrid PCMs are characterized. High latent heat, improved thermal conductivity, excellent thermal and shape stability are observed in the PEG/CNC hybrid PCMs. An obvious decrease of the crystalline phase change temperature is also observed due to the strong hydrogen bonding between the well reserved CNC nanofiber network and PEG molecule chains. This solvent-exchange strategy shows great potential in the large-scale manufacture of high-performance and shape-stable PCMs.

Experimental Study on Hybrid Organic Phase Change Materials Used for Solar Energy Storage

The solar energy utilization in built environment has been limited due to its low heat flux, uneven distribution in time and space and temporal difference in day and night. The phase change materials have been used to collect the fluctuant solar energy to form a stable energy source for the terminal equipment of the buildings. In this study, the hybrid organic phase change materials was prepared for the capillary radiant heating system which formed a cascade utilization of solar energy. Firstly, lauric acid and stearic acid were selected as the basic organic phase change materials and the binary equilibrium phase diagram was completed based on the method of step cooling curve according to the experimental tests data. The results showed that the phase transition temperature of the mixed acid at the lowest eutectic point was 31.2°C and the latent heat value was 264.3 kJ/kg when the mass mixing ratio was 70% for lauric acid and 30% for stearic acid. Secondly, the expanded graphite was used as an additive to enwrap the mixed acid and enhance the heat conductivity. The experimental results showed that when the mass proportion of expanded graphite in the mixed acid was 10%), the mixed acid could be completely enclosed by expanded graphite and the stability of melting and solidification was optimal. Additionally, the phase transition temperature of the hybrid phase change material was 31.5°C and the latent heat value was 217.4 kJ/kg. The novel hybrid phase change material has a lower eutectic point and a higher latent heat of phase change, so it has a large application space and is quite suitable for the cascade utilization of solar energy with capillary network heating system.

Numerical Investigation of Reconfigurable Photonic Crystal Switch Based on Phase Change Nanomaterial

In this article, the novel reconfigurable all-optical switches are designed with ultracompact size, fast response time and high extinction ratio. The hybrid silicon (Si) and phase change material of Germanium−Antimony−Tellurides (GST) based nanoresonator coupled photonic crystal platform is used to realize the 1 × 1, 2 × 2, 3 × 3, and 4 × 4 switches. The GST-based nano-rods are playing a very significant role in “ON” and “OFF” states of the optical switch which can be triggered by changing the phase of the material. The introduction of GST rods within nanocavity provide high output power at the amorphous state and very low output power at the crystalline state, which in turn provide a very high extinction ratio. The designed nanoswitch is optimized through the Finite-Difference-Time-Domain (FDTD) method. The non-volatile 1 × 1 nanoswitch is designed with a low footprint of 44 µm2, the low delay time of 293.86 femtoseconds (fs) and high data rate of 3.40 Tbps. Hence, the reported switching platform is more appropriate for photonic interconnects and quantum computing.

Experimental thermal performance of wallboard with hybrid microencapsulated phase change materials for building application

Combining phase-change materials (PCM) into building envelopes can improve indoor environmental comfort and reduce energy consumption. To adapt to seasonal changes (e.g., hot summer and cold winter), a novel type of hybrid PCM-containing wallboard (including three different PCMs) was fabricated. The hybrid PCM wallboard has a wide phase-change temperature range and can work under different climates for indoor thermal comfort and energy saving. Reduce-scale test cells, two hybrid PCM wallboard integrated test boxes (including Mode 1 PCM wallboard and Mode 2 PCM wallboard) and another equipped with gypsum wallboards, were compared to study the thermal performance of the PCM contained wallboard in both passive and active systems. The results indicate that the hybrid PCM system can narrow indoor air temperature fluctuations and maintain indoor thermal comfort at any time of the entire year. Mode 2 PCM wallboards were found to be more suitable for regulating the indoor thermal environment, as they exhibited more heat release to the indoors during the daytime and less heat loss at nighttime during winter. Under stimulations of different temperature fluctuations, three different layers of the PCMs worked to respond to the temperature fluctuations. Two indices (I and E) were put forward to evaluate the thermal performance of the PCM wallboards. The I index showed that Mode 1 PCM wallboard is suitable for reducing fluctuations of indoor temperature in winter and transition season scenarios. According to the E index, throughout one year, Mode 2 PCM wallboard has higher utilization efficiency than that of Mode 1. Finally, a comparative test was performed with the active system to evaluate the energy saving potential of the two hybrid PCM wallboards. The results show that energy consumption in the hybrid PCM wallboard box is nearly 30% less than that of gypsum wallboard.