Experimental Investigation of Performances of Microcapsule Phase Change Material for Thermal Energy Storage (original) (raw)
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Solar Energy Materials and Solar …, 2009
This study is focused on the preparation, characterization, and determination of thermal properties of microencapsulated docosane with polymethylmethacrylate (PMMA) as phase change material for thermal energy storage. Microencapsulation of docosane has been carried out by emulsion polymerization. The microencapsulated phase change material (MEPCM) was characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Thermal properties and thermal stability of MEPCM were measured by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). DSC analysis indicated that the docosane in the microcapsules melts at 41.0 1C and crystallizes at 40.6 1C. It has latent heats of 54.6 and À48.7 J/g for melting and crystallization, respectively. TGA showed that the MEPCM degraded in three distinguishable steps and had good chemical stability. Accelerated thermal cycling tests also indicated that the MEPCM had good thermal reliability. Based on all these results, it can be concluded that the microencapsulated docosane as MEPCMs have good potential for thermal energy storage purposes such as solar space heating applications.
Microencapsulation of phase change materials (PCMs) is an effective way of enhancing their thermal conductivity and preventing possible interaction with the surrounding and leakage during the melting process, where there is no complete overview of the several methods and techniques for microencapsulation of different kinds of PCMs that leads to microcapsules with different morphology, structure, and thermal properties. In this paper, microencapsulation methods are perused and classified into three categories, i.e. physical, physic-chemical, and chemical methods. It summarizes the techniques used for microencapsulation of PCMs and hence provides a useful tool for the researchers working in this area. Among all the microencapsulation methods, the most common methods described in the literature for the production of microencapsulated phase change materials (MEPCMs) are interfacial polymerization, suspension polymerization, coacervation, emulsion polymerization, and spray drying.
Applied Thermal Engineering, 2018
Thermal energy storage (TES) plays an important role in the development of an efficient solar energy system by storing the solar energy when available during the daytime and use it at night when required. The main component of a TES system is encapsulated phase change materials in macro, micro and nano sacles. Microencapsulated lauric acid (LA) as a renewable (obtained from vegetable oils) and non-toxic Phase Change Material (PCM) with a polystyrene shell was prepared using an emulsion polymerization technique. The individual and interactive effects of operating variables including lauric acid to styrene mass ratio, sodium dodecyl sulfate (SDS) to styrene (St) mass ratio, stirring rate and temperature on the microencapsulation ratio (ME.R) were investigated. Response surface method was applied to the statistical design, analysis of experiments and process optimization. Analysis of Variance (ANOVA) showed that the interaction between the stirring rate and temperature had non-significant effects on ME.R (%). The maximum achieved value of ME.R was 93.14% in the process optimization. It was enhanced compared with microencapsulation ratio of lauric acid in previous studies. By using the optimal values, LA/St mass ratio of 0.42, emulsifier (SDS) to styrene mass ratio of 0.01, stirring rate of 1076 rpm and the temperature of 55 o C, ME.R of 91.64% was obtained. Thermal properties, morphology and thermal stability of the optimal microcapsules were studied using DSC thermograms, Scanning Electron Microscopy (SEM) and thermogravimetry analysis (TGA), respectively. The results showed that microencapsulated renewable PCM with a melting point of 43.77 o C and latent heat of 167.26 kJ/kg has a good potential for utilizing renewable solar energy.
Solar Energy Materials and Solar Cells, 2010
In this study, phase change materials (Rubitherms RT 27) microcapsules were successfully obtained by two different methods. The main difference between them remains on the shell composition, as they are composed of different coacervates (Sterilized Gelatine/Arabic Gum for the SG/AG method and Agar-Agar/Arabic Gum for the AA/AG method). Microcapsules were thermally characterized by thermo-optical microscopy and differential scanning calorimetry. Using scanning electron microscopy, their spherical morphology (sphericity factor of 0.94-0.95) and their particle size distribution were determined, obtaining an average diameter of 12 mm for the SG/AG method and lower values for the AA/AG method, where nanocapsules were also observed (average diameter of 4.3 mm for the microcapsules and 104 nm for the nanocapsules). The thermal stability determination was carried out by Thermogravimetric analyses (TG) and the results show a high decomposition temperature, although the process takes places in four steps for the two mentioned methods. Moreover, the microcapsules obtained by the AA/AG method decompose in a more gradual way, as in the TG results a double step, instead of one, is appreciable. On the whole, the prepared microencapsulated PCM are totally capable of developing their role in thermal energy storage.
Thermal energy storage by microcomposite of a phase change material and ethyl cellulose
Eco-Architecture V, 2014
Phase change materials (PCMs) are capable of storing and releasing large amounts of latent heat thermal energy when undergoes phase change. They are developed for various building applications such as thermal energy storage, thermal protection, cooling, air-conditioning, waste heat recovery and for solar heating systems. Paraffin PCMs have low cost and a moderate thermal energy density, though a low thermal conductivity. PCM microencapsulation is one of the best tools to enhance the heat transfer rate by enlarging the surface area. In this work ethyl cellulose as an environmental friendly encapsulating material was used to entrap n-hexadecane PCM by an emulsion-solvent evaporation method using poly(vinyl alcohol) (PVA), Tween 80 or poly(methacrylic acid sodium salt) (PMAA) emulsifier. The structure of the forming microparticles was predicted by determining the interfacial tensions between the phases. Both theoretically and in the experiments, composites prepared with PMAA showed the most desirable properties regarding the size (average: 80 m) and the latent heat storage capacity (of melting and freezing were 111.4 J/g and 117.9 J/g, respectively), furthermore, there was no significant temperature and enthalpy change observed after 1000 heating-cooling thermal cycles, thus, this microcomposite can be considered as suitable encapsulated PCM for thermal energy storage applications.
International Journal of Energy Research, 2022
Microencapsulated phase change materials (MEPCMs) have made tremendous advancements in recent years, owing to their increased demand for a variety of energy storage applications. In this paper, current microencapsulation techniques, enhancement, and use of medium-and high-melting phase change materials (PCMs) are reviewed, as well as their potential benefits and limitations. The most frequently employed PCMs for medium-and high-temperature applications were recognized as salt-based, metallic, inorganic compound, and eutectic. Meanwhile, polymethyl methacrylate (PMMA), polystyrene-butylacrylate (PSBA), polyethyl-2-cyanoacrylate (PECA), and polyurethane were widely used as polymer shell materials for encapsulating medium-and high-melting point PCMs via chemical method, whereas inorganic silica shell was synthesized via various techniques. Hydrolysis followed by heat-oxidation treatment has been extensively studied since 2015 to encapsulate either metal or alloy within Al 2 O 3 shells. Different techniques were developed to generate void between core and shell material to accommodate volume expansion during phase transition. Numerous approaches, including the incorporation of metal particles, carbon, and ceramic, have been found as ways to enhance the thermal performance of PCMs. Multiple storage arrangements were also established to be an effective way of enhancing the overall efficiency of medium-high melting PCM storage systems. Finally, the paper highlights the potential of medium-and high-melting temperature PCMs for solar power generation, solar cooking, and industrial waste heat recovering applications.
Journal of building engineering, 2023
This paper studies a new type of biobased phase change material (bio-PCM) for thermal storage applications. Novel microencapsulation of natural soy wax core with polyurea shell is designed and synthesized, so as to enhance its phase-change performance. The microcapsules with diameters in the range of 1 m to 10 m are fabricated by interfacial polycondensation method. The morphology and thermal behavior of the microcapsules are studied by optical microscope, SEM and thermal analysis. The thermal properties of the microcapsules revealed that the content of the core material was up to about 89%, and the microcapsules had a high latent heat (ca. 88.3 J/g). The dispersed microcapsules can be used for environmentally friendly latent thermal storage applications such as energy efficient buildings and smart textile.
Energy Reports, 2021
In the present study, nanoparticles of MgO, TiO 2 , and Graphite with mass ratios of 3, 5, 7, and 10% were added to the structure of the synthesized Lauric acid (LA) microcapsules, and the effect of nanoparticles on the thermal properties of microencapsulated Lauric acid as non-toxic phase change material for energy storage applications was investigated. The microcapsules containing nanoparticles were prepared by emulsion polymerization of Styrene as the shell. The microencapsulation ratio (E.R) of LA increases with the amount of MgO and TiO 2. However, the microencapsulation ratio was reduced by increasing the mass ratio of nano graphite. The highest microencapsulation ratio (69.90%) belonged to the microcapsules containing 10% of titanium oxide nanoparticles. Scanning electron microscopy (SEM) images showed that microcapsules obtained containing TiO 2 were spherical with a smooth surface and narrow particle size distribution. The thermal stability and thermal conductivity coefficient for the pure LA, microencapsulated LA with/without nanoparticles were examined. The thermal stability improved with the increasing mass ratio of the nanoparticles, no considerably. The microcapsules with 10% of TiO 2 nanoparticles had higher thermal stability. The weight loss temperatures in the first and second steps are 287 • C and 435 • C, respectively. The thermal conductivity of the lauric acid was increased by microencapsulation from 0.146 W/m.K to 0.149 W/m.K. The thermal conductivity coefficient of microcapsules increased by adding nanoparticles. Finally, the thermal energy storage performance of the obtained samples was evaluated in a designed experimental setup. The decrement percentage of the onset of the melting process time for lauric acid microcapsules and the microcapsules containing graphite nanoparticles, titanium oxide, and magnesium oxide were 1.2, 4.7, 8.5, and 16.7%, respectively.