Composite Phase Change Materials Research Articles

Structurally engineered 3D porous graphene based phase change composite with highly efficient multi-energy conversion and versatile applications

Micro-nano encapsulation strategy combining three-dimensional (3D) porous carriers and phase change materials (PCMs) has been widely investigated due to its structure stability, high efficiency, and designability. However, the current 3D scaffolds suffering from structure regularity are hard to meet the urgent requirements of high energy conversion efficiency and versatile applications. Herein, a 3D porous graphene scaffold (2LrGO@LIG), which is fabricated from polybenzoxazine/graphene oxide (GO) composite using laser irradiation that structurally engineers a gully-shaped surface and a 3D overlapped graphene networks, was employed for PCMs encapsulation. The addition of GO is proved to enhance the quality of produced laser induced graphene (LIG), which could also be reduced into laser-reduced graphene oxide (LrGO) and connect the adjacent LIGs as thermal bridges. As a consequence, the obtained phase change composite (2LrGO@LIG/MA) showed photo-thermal and electro-thermal conversion efficiency of 94.1 % and 99.1 %, respectively. In addition, benefiting from the surface hydrophobicity (135°), high energy storage density (167.7 J/g) and electrical conductivity (307.9 S/m), 2LrGO@LIG/MA also demonstrated great potential in smart building materials and wearable electronic devices. This study provides a facile method for designing advanced PCM composites with multi-energy conversion capacity and application versatility.

A comprehensive experimental study of cooling photovoltaic panels using phase change materials under free and forced convection – Experiments and transient analysis

Solar radiation is captured by photovoltaic (PV) panels, which use it to create electricity. However, an overabundance of photons striking the PV's surface raises its temperature, which lowers its efficiency. These days, cooling solar panels is very important, and research on these methods is widely available in the literature. Thus, the study field's problems truly lie in developing new or improved methods for doing the same tasks. The goal of this work is to further boost the efficiency of photovoltaic (PV) panels beyond what can be achieved with PCM and free/forced convection alone. To do this, phase change materials (PCM) are cooled using both free and forced convection. In accordance with the latitude of Lebanon's Bekaa Valley, four cooling techniques are experimentally investigated. A photovoltaic panel using phase-change material (PCM) with copper and aluminum wires in a 70 %–20 %–10 % mass ratio (CPCM-PV), respectively, is the first cooling method. In the second approach, four 5 cm long fins are fixed under free convection using the same combination of aluminum fins inside the PCM container while preserving the same ratio (IEF-PCM-Free-PV). The third technique is the same as the second but with forced convection (IEF-PCM-Forced-PV), while the fourth technique uses an aluminum finned plate with 16 finned plates under forced convection (F-Forced-PV). IEF-PCM-Forced-PV showed the most relative increases in efficiency rate of energy dissipated of 20.36 % and 62.24 %, respectively, as compared to the regular PV panel, according to the results. F-Forced-PV, IEF-PCM-Free-PV, and CPCM-PV showed an increase in relative efficiency of 16.87 %, 6.3 %, and 3.9 % respectively, and correspondingly, these enhancements were accompanied by an increase in energy dissipation of 55.80 %, 44.85 %, and 41.18 % for each system. Economically, the IEF-PCM-Forced-PV had the highest total yearly savings of $17.87 with a payback period of 1.9 years. An appropriate transient energy balance is conducted and permitted to demonstrate clearly the transient behavior of the system under the various cooling techniques. Finally, the percentage of enhancement using the newly suggested composite PCM with internal and external fins under forced convection is compared to the enhancement found in the literature for various classical techniques and shows greater potential for further enhancement of the PV performance.

Optimizing thermal properties and heat transfer in 3D biochar-embedded organic phase change materials for thermal energy storage

Enhancing the thermal properties and light-absorbing capabilities of phase change materials (PCMs) through the utilization of environmentally friendly, economically viable biochar materials is pivotal for optimizing solar energy capture and utilization. Herewith, initially, a green, three-dimensional, eco-friendly carbon nano inclusion is synthesized from Prosopis juliflora through vacuum oven carbonization at 130 °C, followed by size reduction via ball milling, promising high-impact contributions. Subsequently, green-synthesized nano-inclusions are dispersed in PEG-1000, creating advanced nano-enhanced phase change materials with improved thermo-physical properties using a two-step ultrasonication technique for enhanced thermal conductivity. This innovative study comprehensively explores the morphological behaviour, chemical stability, optical absorptivity, thermal properties, and reliability of the PEG-PJ composite. Remarkably, present research revealed that the composite achieved its highest thermal conductivity, an impressive 0.49 W/m⋅K, at 0.7 wt% of 3-D (PJ) biochar. Notably, the melting temperatures of the PEG-PJ composites consistently ranged from 40.1 °C to 40.5 °C. At the same time, their latent heat capacities displayed a notable increase, ranging from 145 J/g to 152.7 J/g, marking a substantial enhancement of 3.968% and 1.758%, respectively. Furthermore, to confirm the reliability and consistency of experimental findings, 500 thermal cycles were performed. Additionally, a numerical analysis study is conducted by utilizing 2-D energy modelling software to simulate the heat transfer rate owing to the improved thermal conductivity of the developed PEG-PJ composite PCM compared to PEG-1000. In conclusion, developed composites optimize solar storage, improve building thermal control, and enhance industrial heat exchangers for sustainable innovation in energy.

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.

Analysis of thermal storage behavior of composite phase change materials embedded with gradient-designed TPMS thermal conductivity enhancers: A numerical and experimental study

Phase change materials (PCMs) exhibit considerable potential for utilization in energy storage and temperature regulation applications, primarily attributed to their notable latent heat capacity. Nevertheless, the intrinsically limited thermal conductivity of PCMs necessitates the use of thermal conductivity enhancers (TCEs) that possess adjustable features to compensate for greater heat storage efficiency. Porous structures with flexible design freedom have garnered growing interest in contrast to traditional random foams, owing to their significantly larger surface areas and fully interconnected pore networks. This study fabricated three polar form-designed triply periodic minimal surfaces (TPMS) porous structures using selective laser melting (SLM) based on various radial density gradients, namely the uniform density, the linear gradient, and the Boltzmann gradient. The TPMS porous structures were incorporated as TCEs within a paraffin matrix to form composite TPMS-PCMs. The melting behavior of composite TPMS-PCMs during the charging process was investigated by employing both visual experiments and numerical methods. A thorough analysis was undertaken regarding the progression of solid-liquid phase interfaces, temperature distribution, convection distribution, and heat storage rate to elucidate the mechanisms that contribute to enhanced heat transfer. The findings indicate that the configuration of the density gradient has a notable impact on the melting behavior of composite TPMS-PCMs by tuning heat transfer paths. The heat storage rate of the linear gradient case is the highest among the three, reaching 12.1 W, 1.6 times that of the uniform density case, and twice that of the Boltzmann gradient case. Although the Boltzmann gradient case has the lowest heat storage rate, it demonstrates exceptional performance in terms of temperature uniformity. The average temperature gradient along the radius during melting is 348.6 °C/m, which is only 59% observed in the linear gradient case and 56% in the uniform density case. These findings substantiate the effectiveness of the radial gradient density design in the control of the thermal storage process of composite TPMS-PCMs. They serve as a reference for optimizing thermal storage and temperature control systems that rely on latent heat storage in the future.

Carbonated balsa-based shape-stable phase change materials with photothermal conversion and application in greenhouse

Greenhouse enables to promote plant yield through creating optimal environment. Efficient solar energy conversion and storage is a promising strategy to address energy shortage issue of greenhouse in winter. This paper prepares form-stable composite phase change materials (PCMs) to store solar energy efficiently. Lightweight and porous balsa wood subjected to high-temperature carbonization is designed to simultaneously solve the liquid leakage, enhance the thermal conductivity, and improve the photothermal conversion and thermal energy storage of PCM. OP44E and SEBS are utilized as PCM and thickener, followed by vacuum impregnation into the carbonized balsa wood (CW). Results indicate that carbon content of CW increases with the augment of carbonization temperature. Shaping effects of CW and SEBS endow composite PCMs to have highest adsorption rate of 92.7 wt% with enthalpy over 190 J/g. Composite PCMs reveal reliable thermal properties and thermal stability below 100 °C. Composite PCMs have photothermal conversion larger than 88 % under a xenon lamp radiation. Temperature of PCMs on the shallow layer is higher owing to its photothermal conversion capacity. Greenhouse test indicates that CW/OP44E/SEBS greenhouse gains higher PCM temperature of 71.5 °C at 70 min, compared to 40.3 °C in empty and OP44E/SEBS cases. CW/OP44E/SEBS greenhouse maintaining indoor temperature over 20 °C lasts 15.3 min longer than empty and OP44E/SEBS greenhouses. In addition, form-stable composite PCMs featured with excellent thermal stability and photothermal conversion are capable of maintaining stable indoor temperature of greenhouse, indicating potential in the field of agricultural building temperature regulation.

Investigation on the battery thermal management and thermal safety of battery-powered ship with flame-retardant composite phase change materials

Pure battery-powered ships have attracted much attention because of its unique advantages of zero-emission. However, the problems of adaptability to extreme working conditions and thermal safety risks restrict the development of battery-powered ships. In this study, a novel flexible flame-retardant composite phase change materials (CPCM) with paraffin (PA)/EVA grafted on maleic anhydride (EVA-g-MAH)/expanded graphite (EG)/ammonium polyphosphate (APP)/triphenyl phosphate (TPP)/Na2SiO3 has been proposed and utilized in battery module. Among them, the sample ATPCM2 with APP/TPP/Na2SiO3 ratio of 5/10/10 achieved the optimal thermal properties and flame-retardant effect. The designed multifunctional CPCM harmonizes the competition between flame retardancy, mechanical properties and phase change latent heat by the synergistic effect. Besides, the ATPCM2-Module shows a good temperature control performance during charge-discharge cycles, such as the maximum temperature of battery module can be still controlled below 50 °C at 2C discharge rate and the corresponding temperature difference was effectively maintained within 4.1 °C. This is owing to the constructed stable three-dimensional heat conductive skeleton formed by synergistic flame retardancy effect, which could improve the dissipation heat capacity and thermal safety. With these prominent performances, the designed flexible CPCM with desired flame-retardant and thermal management performance can provide insights into the passive thermal management and thermal safety improvement of both battery-powered ships and high-power battery module under extreme conditions.

Characterization of novel lamellar porous Ti3SiC2 as shape-stabilized high-temperature phase change materials composites for durable enhancement thermal storage properties

In pursuit of leveraging porous media for high-temperature phase change materials (PCMs) to enhance the overall thermal conductivity and encapsulation performance of PCMs, this study delves into the corrosion behavior of Ti3SiC2 with a lamellar porous structure in different corrosive environments at both high and low temperatures. By manipulating the solid content to modify the porous structure, the investigation probes the corrosion phenomena and anti-corrosion mechanisms across various porous configurations. The results reveal that F ions exert the most extensive structural degradation on Ti3SiC2. Based on these insights, a successful fabrication of a molten salt phase change composite material, Ti3SiC2/KCl-NaCl, boasting a lamellar structure was achieved. With an increase in solid content, the thermal conductivity escalates from 6.13 to 9.27 W/(m∙K), tripling the heat conductivity of pure KCl-NaCl. However, this also leads to a reduction in latent heat from 126.7 J/g to 46.2 J/g. Consequently, the phase change energy storage performance of PCM prepared by sample 2 emerges as exceptionally commendable. Following 200 thermal cycles on the composite PCM, no discernible structural damage was observed, albeit a slight performance decline. Hence, the lamellar Ti3SiC2/KCl-NaCl structure not only boasts favorable phase change energy storage capabilities but also demonstrates an extended service life.

Experimental study of a paraffin-based composite phase change material with graphite sheet, copper powder and silver copper powder

In order to study a kind of phase change material with high thermal conductivity (TC) and high latent heat (LH) of phase change used in mine cooling work clothes. This paper prepared a phase change material based on paraffin and added graphite sheet (GS) composite material with different thickness and metal (copper powder (CP), silver copper powder (SCP)) composite material, and test the thermal parameters. The results showed that the LH of the composites increased by 16 % when the thickness of GS was increased from 0.02 to 0.08 mm. And with the addition of GS, the TC of the composite was increased by 15 %. The LH of the SCP composite is greater than that of the CP composite when the metal addition is 5 %, after which the LH gradually decreases and is the same when the mass fraction of metal added is 8 %. The TC of the composite material grow from 4.451 to 6.012 W/(m⋅K) with the addition of CP; the TC of the composite material grow from 4.457 to 20.332 W/(m⋅K) with the addition of SCP. Through the performance test of the cooling clothing, the cooling clothing can effectively improve the thermal comfort of human body.

Lithium-ion battery pack thermal management under high ambient temperature and cyclic charging-discharging strategy design

To ensure the stable operation of lithium-ion battery under high ambient temperature with high discharge rate and long operating cycles, the phase change material (PCM) cooling with advantage in latent heat absorption and liquid cooling with advantage in heat removal are utilized and coupling optimized in this work. Based on the preferred hybrid cooling scheme, the two layers cold plates and fins are arranged, and the cold plate structure is redesigned to optimize cooling system. The coupling effects of composite PCM and water flow rate, as well as charging and discharging strategy, are numerically studied. The results show that the hybrid cooling is more suitable to high discharge rate of 5C and long-term cyclic operation at 40 °C. The two layers cold plate and fins arranged in hybrid cooling system can mitigate the temperature non-uniformity of batteries along the axis, and the maximum temperature Tmax and temperature difference ΔTmax are reduced by 4.44 °C and 4.17 °C, respectively. Also, the optimized cold plate can mitigate the temperature non-uniformity caused by battery dispersion, and the standard deviation of temperature of batteries is reduced from 0.48 to 0.37. Then, the composite PCM added with expanded graphite can further decrease the Tmax and ΔTmax by 2.18 °C and 1.79 °C, respectively. Lower charging rate offers more reliable cooling performance during continuous cyclic operations. In general, the designed fin-enhanced hybrid cooling system with composite PCM and two layers cold plate can control the Tmax and ΔTmax within 45.85 °C and 3.39 °C at 40 °C ambient temperature and 5C discharge respectively, and offers a reliable and desired cooling performance during continuous charging and discharging of 1C, 2C and 3C. During cyclic operation with 3C discharging and 1C charging, the Tmax and ΔTmax can be controlled below 44.39 °C and 2.64 °C, respectively.

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.

Phase change material coated geotextile for temperature regulation of subgrade soil

High temperatures leading to thaw settlement deformation of soil are the primary cause of damage to road structures in permafrost regions. In this study, phase change material (PCM) is prepared by adsorbing tetradecane, and epoxy resin composite phase change material (ERPCM) is prepared by combining epoxy resin with PCM. ERPCM is applied to geotextile to create phase change geotextile (PCG) with energy storage and impermeability characteristics. The impact of epoxy resin content and freeze–thaw cycles on ERPCM performance is analyzed using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The results show that epoxy resin enhances the thermal stability and freeze–thaw resistance of ERPCM. When the mass ratio of epoxy resin to PCM is 0.8:1, ERPCM exhibits its highest enthalpy values both before and after freeze–thaw cycles, reaching 81.5 J/g and 72.6 J/g, respectively. The energy storage modulus of ERPCM decreases with increasing epoxy resin content. Temperature regulation experiments demonstrate that PCG under different structures can adjust the sample temperature within the range of 6 to 16 °C. Higher quantities of ERPCM could store more energy in the PCG. The temperature regulation effect is more pronounced when PCG is placed at greater depths. Increasing the number of PCGs improves the overall temperature regulation effect but reduces the individual temperature regulation effect of each PCG. This study has theoretical significance and practical value for promoting the further application of PCM in permafrost subgrades.

Thermal properties and cyclic stability of sodium acetate trihydrate composites containing expanded graphite of different sizes

The thermal conductivity, thermal cycling behaviour, and deformation resistance of composite phase change materials (cPCMs) based on sodium acetate trihydrate (SAT) can be effectively improved using expanded graphite (EG). Existing studies have primarily focused on the effect of the expansion ratio on the cPCMs of SAT, and the effect of the particle size of EG on the cPCMs of the SAT has received limited attention. Additionally, more research is required on the degree of supercooling and effective thermal cycles in thermal cycles. In this study, the effects of EG of different sizes (250 and 425 μm) and proportions (0, 1, 2, 3, 4, 5, and 6 wt %) on the thermal properties and the phase change behaviour of cPCMs in thermal cycles were studied. The results revealed that the 425 μm EG had a better effect on improving the thermal conductivity of the cPCMs, whereas the 250 μm EG had a better effect on improving the thermal cycling stability of cPCMs, as evidenced by the sample with 3 wt% of 250 μm EG completing 512 solidification cycles out of 530 thermal cycles.

Experimental and analytical studies on latent heat of hydrated salt/modified EG-based form-stable composite PCMs for energy storage application

Expanded graphite (EG) is often used to encase phase change materials (PCMs) and improve their thermal performance. However, EG's effectiveness when used with disodium hydrogen phosphate dodecahydrate (DHPD) as a hydrated salt is diminished, due to its hydrophobic property. This study proposes modifying the hydrophobic surface of EG with highly hydrophilic nanoparticles, such as SiO2 and TiO2, to address this shortcoming and boost its hydrophilicity. Herein, the nanoparticles were synthesized by the sol-gel technique and mixed with EG to construct a modified EG (MEG). The microstructure, morphology, and adsorption ability of MEG were analyzed. Additionally, the thermal properties, as well as the thermal stability of form-stable composite PCMs, were investigated. The results revealed that by varying the mass ratio of SiO2@TiO2 in MEG, the supercooling degree of the form-stable composite PCMs decreased by 77.36%–78.49%. With 9% SiO2@TiO2 in MEG, the water contact angle of MEG was optimal, and the form-stable composite PCMs prepared (DSMEG3) exhibited a phase change temperature and latent heat of 32.88 °C and 142.13 J/g, respectively. This experimental latent heat was slightly lower than the calculated latent heat by 0.12 J/g. Meanwhile, the supercooling degree decreased to 3.01 °C, and the thermal conductivity increased to 1.23 W/(m ∙ K), which was 1.73 times than that of DHPD. Moreover, DSMEG3 also showed good shape stability, preventing leakage. Therefore, the form-stable composite PCMs, as prepared, are a great potential candidate for the energy storage applications.

Preparation and thermal property enhancement of sodium acetate trihydrate-lithium chloride-potassium chloride expanded graphite composite phase change materials

Phase change materials (PCMs) present promising solutions for enhancing energy efficiency in solar heat pump systems. In our study, we have innovatively developed a composite PCMs (CPCMs) by combining sodium acetate trihydrate (CH3COONa·3H2O, SAT), lithium chloride (LiCl), potassium chloride (KCl), and incorporating expanded graphite (EG). This addition of high thermal conductivity EG was aimed at bolstering the CPCM's thermal stability. Our findings reveal that SAT-LiCl-KCl/EG CPCMs, with 14 wt% EG, significantly enhances thermal energy storage performance while preserving the fundamental phase change characteristics. The resulting CPCMs demonstrates a phase transition temperature of 49.3 °C and a latent heat of 196.4 J/g, ideally suited to meet the demands of hot water heat pump systems operating in the 45–50 °C range. Notably, the thermal conductivity of this CPCMs, following the incorporation of 14 wt% EG, registers at 4.54 W/(m K), representing a remarkable 10.6-fold increase compared to the SAT-LiCl-KCl ternary eutectic salt. To ensure long-term stability, secondary encapsulation with a thermally conductive sealant was applied. Subsequent tests involved subjecting the CPCM to 3000 heating/cooling cycles, resulting in minimal deviations, with the phase transition temperature shifting by approximately 1 °C and a modest 6 % reduction in latent heat of phase transition. These outcomes underscore the robustness and reliability of our developed composite phase change materials.

Synthesis and characteristic analysis of an inorganic composite phase change materials for medium-temperature thermal storage

Composite phase change materials (CPCM) synthesized using inorganic salt (Na2HPO4·12H2O), lime fruit peel biochar (activated), and boron nitride have been explored as a solution for the medium-temperature thermal energy storage systems in this work. The activated biochar and BN concentrations were varied, and the effects of the activated biochar and BN on the thermal properties, chemical, and thermal stability of the phase change materials (PCM) were studied. XRD and FTIR studies confirmed the chemical stability of the synthesized CPCM samples. Leak test results revealed that the addition of biochar and BN has improved the shape stability. TGA studies revealed the superior thermal stability of the CPCM samples. Composite PCM with 2 g of activated biochar and 0.5 g of BN has exhibited better thermal properties with a latent heat of 121.33 J/g, encapsulation efficiency of 55.9%, and thermal energy storage capacity of 98.2% compared to the pure PCM.

CH3COONa·3H2O/flaky modified vermiculite composite phase change materials enhanced phase change behavior and thermal storage through curing lotus root starch modification

With the establishment of the basic policy of environmentally-friendly and resource-saving society, the energy storage technology using phase change materials (PCMs) as the medium has developed unprecedentedly. Hydrated salt PCMs plays a vital role due to its large latent heat density, wide range of phase transition temperature, and high thermal conductivity. However, the problems of low enthalpy, poor thermal stability and phase separation are critical drawbacks of composite phase change materials (CPCMs), which limited the extensive use in fields of energy storage. In this work, the flaky vermiculite (MEVM) was fabricated by the acid treatment and alkali leaching, and the cured lotus root starch (CLRS) was embedded and used to enhance the water holding capability of hydrated salts. A series of sodium acetate trihydrate (SAT)-CLRS/MEVM was prepared, and the form-stable composite phase change materials (SAT fs-CPCMs) were obtained. Results showed that the encapsulation capacity of SAT fs-CPCM with 2 wt% CLRS was 71.3 %, and the thermal enthalpy reached 180.1 J/g, which was 43.7 % higher than that of SAT/MEVM. The contact angle of the sample with H2O was 22.24°, which represented hydrophilicity. SAT fs-CPCM also had good thermal stability and thermal reliability. After 200 thermal cycles, the enthalpy loss of the SAT fs-CPCM was only 5.2 %, and the 200th enthalpy value was 173.72 J/g. In addition, Calculations indicated that there were hydrogen bonds and van der Waals weak interaction between SAT and CLRS. This work provides a new perspective for the improvement of the thermal properties of hydrated salt and offers a promising approach for the applications of PCMs in cost-effective energy storage.

Characterisation and energy storage performance of 3D printed-photocurable resin/microencapsulated phase change material composite

The 3D fabrication of microencapsulated phase change material (MEPCM) doped resin polymer composites enables the creation of complex shapes and customized designs, opening doors for many applications in fields. This investigation fabricated a range of resin/MEPCM (20 %, 30 %, and 40 % by volume) composites using a mechanical mixing technique. This study investigates how the addition of MEPCM impacts resin matrix composite's mechanical strength, latent heat storage characteristics, and ability to regulate temperature effectively. With a 40 % MEPCM additive ratio, a pure resin porosity value of approximately 0.4 % increased to around 17 %. Thanks to the production of homogeneously dispersed MEPCM added resins with production with stereolithography (SLA), 40 % MEPCM additive enabled characteristic FTIR peaks of both MEPCM and resin to appear and, melting and solidification enthalpy values reached 87.15 j/g and 86.25 j/g, respectively. MEPCM addition enhanced the thermoregulatory properties of resin by absorbing or releasing heat during temperature fluctuations. On hotter days, 8 mm-thick composites create temperature differences exceeding 11 °C, while this difference exceeds 6 °C in the room center case. The produced 3D printed MEPCM/resin composite can be a potential material to effectively regulate the temperature of electronic devices, food packets, building materials, and electronic devices and automotive components.

Flexible insulating phase change composite film with improved thermal conductivity for wearable thermal management

Phase change materials (PCMs) are extensively employed as media for thermal energy storage and temperature regulation due to their remarkable capacity to absorb or release significant amounts of latent heat at constant phase transition temperatures. However, the inherent low thermal conductivity, solid-state rigidity and electric insulation issues of PCMs greatly limit their practical applications in the field of wearable thermal management of flexible electronic devices. Herein, we have developed a flexible composite PCM film with improved thermal conductivity by incorporating paraffin wax (PW) with a porous structure of polyvinylidene fluoride-boron nitride (PVDF-BN) film as a substrate. Remarkably, the composite film exhibits outstanding electric insulation properties and excellent cycle stability, further enhancing its suitability of thermal management in wearable electronics for safe and long-term applications. The obtained flexible composite PCM film exhibits a superior melting enthalpy of 105.63 J·g−1, along with a 200% improvement in thermal conductivity compared to the pure PW. Furthermore, this flexible composite film can not only retain its remarkable flexibility at room temperature but also demonstrate attractive shape recovery capabilities during phase transition process. The flexible insulating PCM film developed in this work may hold substantial promise for applications in the field of wearable thermal management for next-generation electronic devices.

Using Carbonized Cotton Fabric Waste to Prepare Poly(ethylene glycol) Composite Phase Change Materials with Improved Thermal Conductivity and Solar-to-Thermal Conversion.

Poly(ethylene glycol) (PEG) boasts excellent thermal energy storage capabilities but lacks efficiency in thermal conductivity and solar absorption. Simultaneously, the escalating concern surrounding the substantial volume of discarded cotton fabric underscores environmental issues. In this study, we devised composite phase change materials (PCMs) by embedding PEG into a carbon cotton material (CCM), varying PEG content from 50 to 80%, and conducted a comprehensive analysis of their thermal properties and solar-to-thermal conversion. The CCM, crafted from a waste 100% cotton towel through carbonization, provided an optimal porous structure that accommodated a significant 70% PEG content without any leakage, thanks to interactions such as surface tension, capillary forces, and interfacial hydrogen bonds. These PEG/CCM composites exhibited impressive crystallization fractions (>92%), resulting in notable thermal energy storage capacities ranging from 85.3 to 143.2 J/g as the PEG content increased from 50 to 80%. Moreover, these composites showed high thermal stability and exceptional cycling durability even after 500 melting/crystallization cycles. Notably, their thermal conductivities markedly increased to a range of 0.46-0.85 W/m·K compared to pure PEG's modest 0.24 W/m·K. Furthermore, the PEG/CCM composites substantially augmented visible and near-infrared (VIS-NIR) light absorption. Evaluation of solar-to-thermal conversion illustrated the composite's ability to efficiently convert solar energy into thermal energy, storing and subsequently releasing it through melting and crystallization processes. This study introduces a novel class of composite PCMs characterized by cost-effectiveness, outstanding thermal performance, and impressive solar-to-thermal conversion capabilities. These composite PCMs hold significant promise for large-scale solar-to-thermal energy storage applications while contributing to the sustainability of cotton waste management.