• Energy Research

Phase change materials (PCMs) face obstacles in being widely used due to issues with heat transfer and maintaining their shape. In this research, instead of using binders, the Hexadecane (H) is melted in such a way that the capillary forces of the molten wax allow it to be impregnated into the low-density polyethylene (P) molecules and bind it together as a composite. It was found that the hot melt extrusion (HME) combines the two materials at the micro-scale, forming a phase change composite (CPCM) with various geometries that possesses superior latent heat and shape stability during phase transition. The structure can incorporate a higher percentage of PCM (60 %) using this method, which also results in lower costs. According to the thermal analysis, (H60P40) provides great thermal stability and can store a lot of energy per unit of weight. It has a high capacity of storing latent heat at 129.56 J/g and can also prevent Hexadecane leakage. Based on the mechanical properties results, hexadecane acts like plasticizer thus the addition of PCM decreases Young's modulus, stress in break, and stress at yield. This trend is observed as the PCM content increases. The high values of elongation at break also indicates the strong plasticizing properties of PCM. Based on the obtained results, the CPCMs as a potential candidate for an application in buildings for thermal regulation, reducing energy consumption, and reducing indoor temperature swing.

Phase change materials (PCMs), as an effective thermal energy storage technology, provide a viable approach to harness solar heat, a green energy source, and optimize energy consumption in buildings. However, the obstacle preventing widespread practical use of PCM is its poor performance in terms of heat transfer and shape stabilization. This article focuses on the application of the shape stabilization method. To improve the thermal conductivity of organic PCMs (hexadecane), copper microparticles are added to form phase change composites (PCC). This process allows an enhanced PCM (75 wt%) that distributes effective thermal storage capabilities while maintaining low cost. SEM, FTIR, ATG, infrared thermography (IRT), and DSC were used to characterize the composites’ micromorphology, chemical composition, thermal degradation stability, and thermal energy storage capabilities. DSC results showed that a proportion of 75 wt% phase change material with 15 wt% Cu had excellent thermal stability and high energy storage density per unit mass. In light of its high latent heat storage capacity of 201.32 J/g as well as its ability to prevent Hexadecane exudation, PCC ensures higher thermal conductivity and shape stability during phase transition than ordinary PCM. The incorporation of Cu to paraffin causes delay in PCM phase transformation, leading it to respond to rapid charging and discharging rates and, consequentially, to challenges in temperature control, as shown by IRT. The new PCCs had favorable thermal stability below 100 °C, which was advantageous for practical application for thermal energy storage and management, and notably for solar thermal energy storage.

Abstract In this work, a Shape-stabilized phase change materials were prepared by absorbing hexadecane into the network of styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) tri-block copolymer and coating them with a low-density polyethylene (LDPE). The four composites were prepared at different mass fractions of Hexadecane/SEBS (80/5, 75/10, 65/20, 55/30, w/w %) with 15% of LDPE by the melt-mixing method. Thermal conductivities and diffusivities were evaluated using a Hot Disk Thermal Constants Analyzer (TPS 2500S) and the Transient Guarded Hot Plate Technique (TGHPT) was used to investigate thermal storage and release capacity of the composites. Results were compared to DSC/TGA data. The thermal properties of the composite were improved by the incorporation of the Hexadecane, where the latent heat of composites increased from 106.15 kJ/kg to 179.76 kJ/kg for the composite containing 80% PCM. Interestingly, the mass fraction of Hexadecane could reach approximately 80% with a good form stability, which surmounts almost all mass fraction values reported in the literature.

Abstract This paper focuses on the experimental investigation of the storage and release of thermal heat during melting and solidification of PCM (phase change material). The materials tested have a gypsum or epoxy resin matrix which incorporates metallic tube filled with PCM. An investigation by means of a differential scanning calorimeter (DSC) was carried out to obtain the latent heat and the transition temperature of paraffin. The main objective is to elucidate which is the most efficient composite-PCM by measuring, effective thermal conductivity, total heat accumulated; the average heat capacity and latent heat stored using a new transient hot plate apparatus. Comparing the results, it was demonstrated that that the considered composite gypsum-PCM has potential thermal energy storage purpose in buildings. Experimental investigations of the thermophysical properties of the considered composite (gypsum/copper tubes) have shown that the material combines a high heat storage potential and an improved heat transfer at the same time. Besides, the results showed that the shape-stabilized phase change material prevents the leakage of the molten paraffin during phase transition and proved a good thermal stability.

AbstractIntegrating phase change materials (PCMs), which store thermal energy as latent heat, into renewable energy production is an efficient way to harness solar energy. Thereby, the aim of this work is to develop convenient and efficient method to prepare a bio‐composite phase change materials (BCPCMs) that are eco‐friendly and cheap. The polyethylene glycol (PEG) with large latent heat was used as PCM, eggshell powder (ES) as an energy storage material (bio‐energy resources/bio‐waste is converted into useful energy storage material), the low‐density polyethylene (PE) performed as the supporting material and powder graphite (G) was the additives for improving the thermal conductivity. According to thermal gravimetric analysis (TGA), the use of ES and G improved the thermal stability of BCPCM. On the other hand, the results of the differential calorimetric analysis (DSC) showed that BCPCM6 with the addition of 5 wt% of graphite filler in the mixture PEG/PE/ES (70/20/5 wt%) provides excellent thermal stability and high energy storage density per unit mass. In light of its high latent heat storage capacity of 120.1 J/g as well as its ability to prevent PEG exudation, BCPCM ensures higher thermal conductivity and shape stability during phase transition than ordinary PCM. Significant enhancement in melting‐solidification time shows an improvement in Thermal Energy Storage (TES) response time to the demand by adding ES and G respectively to the PCM. Based on the obtained results, the BCPCM as a potential candidate for an application in buildings of hot and dry climates.Highlights Shape‐stabilized BCPCMs were prepared by blending and impregnating method. The BCPCM combines a high storage capacity and high heat propagation rate. BCPCM6 provides excellent thermal stability and high energy storage density. Enhancement in melting‐solidification time by adding ES and G to the PCM. BCPCM as a candidate for an application in buildings of hot and dry climates.

Thermal Energy Storage (TES) technologies based on Phase Change Materials (PCMs) with small temperature differences have effectively promoted the development of clean and renewable energy. Today, accurate thermal characterization is needed to be able to create an optimal design for latent heat storage systems. The thermo-physical properties of PCMs, namely latent heat, phase-change temperatures, enthalpy and specific heat capacity are obtained by means of differential scanning calorimetry (DSC), which is one of the most widely used techniques to study reactions related to the transformation of a material subjected to temperature constraints. This method presents some limitations due, among other things, to the fact that only a very small quantity (less than 90 mg) of material can be tested. Indeed, the small mass samples, taken out of the large testing specimen and out of testing system, is not representative of the thermal behavior of a material on a large scale. The Transient Guarded Hot Plate Technique (TGHPT) presents several advantages when compared to the commercially available thermal analysis methods (DSC, DTA) to determine PCM thermophysical properties. The most significant are large sample amount, optimized measuring time and a simple and economical built up.

This study reports the results of experimental and numerical investigations on the thermophysical properties and the process of melting of a phase-change composite material. The proposed phase-change composite material based on epoxy resin with spherical shape paraffin wax (RT27) was used as a new thermal storage system. Thermal characterization was performed using a transient guarded hot plate technique. The results revealed the importance of thermal storage by latent heat. The numerical analysis is realized using numerical COMSOL® Multiphysics 4.3b. The effect of various parameters of the numerical solution on the results is examined: in particular, the term describing the mushy zone in the momentum equation and the influence of temperature melting range. The findings of the experimental investigation compare favorably with the numerical results.

Abstract Phase change material (PCM) composites based on low-density polyethylene (LDPE) with paraffin waxes were investigated in this study. The composites were prepared using a meltmixing method with a Brabender-Plastograph. The LDPE as the supporting matrix kept the molten waxes in compact shape during its phase transition from solid to liquid. Immiscibility of the PCMs (waxes) and the supporting matrix (LDPE) is a necessary property for effective energy storage. Therefore, this type paraffin can be used in a latent heat storage system without encapsulation. The objective of this research is to use PCM composite as integrated components in a passive solar wall. The proposed composite TROMBE wall allows daily storage of the solar energy in a building envelope and restitution in the evening, with a possible control of the air flux in a ventilated air layer. An experimental set-up was built to determine the thermal response of these composites to thermal solicitations. In addition, a DSC analysis was carried out. The results have shown that most important thermal properties of these composites at the solid and liquid states, like the “apparent” thermal conductivity, the heat storage capacity and the latent heat of fusion. Results indicate the performance of the proposed system is affected by the thermal effectiveness of phase change material and significant amount of energy saving can be achieved.

Abstract This paper reports the results of an experimental investigation on the thermophysical properties of composites materials (Epoxy resin/paraffin spheres) and (Epoxy resin/metal tubes) filled with paraffin developed to improve different properties of PCM and open a wide field of applications to latent heat storage systems. The objective of this research is to use PCM composite as integrated components in a passive solar wall. The proposed composite TROMBE wall allows daily storage of the solar energy in a building envelope and restitution in the evening, with a possible control of the air flux in a ventilated air layer. An experimental set-up was built to determine the thermal response of these composites to thermal solicitations. The results have shown that most important thermal properties of these composites at the solid and liquid states, like the “apparent” thermal conductivity, the heat storage capacity and the latent heat of fusion. Experimental investigations of the thermophysical properties of composites materials (Epoxy resin/metal tubes) filled with paraffin have shown that these materials combines a high heat storage capability and an enhanced heat transfer at the same time.