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.

A review of microencapsulation methods of phase change materials (PCMs) as a thermal energy storage (TES) medium

Various types of solid–liquid phase change materials (PCMs) have been reviewed for thermal energy storage applications. The review has shown that organic solid–liquid PCMs have much more advantages and capabilities than inorganic PCMs but do possess low thermal conductivity and density as well as being flammable. Inorganic PCMs possess higher heat storage capacities and conductivities, cheaper and readily available as well as being non-flammable, but do experience supercooling and phase segregation problems during phase change process. The review has also shown that eutectic PCMs have unique advantage since their melting points can be adjusted. In addition, they have relatively high thermal conductivity and density but they possess low latent and specific heat capacities. Encapsulation technologies and shell materials have also been examined and limitations established. The morphology of particles was identified as a key influencing factor on the thermal and chemical stability and the mechanical strength of encapsulated PCMs. In general, in-situ polymerization method appears to offer the best technological approach in terms of encapsulation efficiency and structural integrity of core material. There is however the need for the development of enhancement methods and standardization of testing procedures for microencapsulated PCMs.

/pdf/review-of-solid-liquid-phase-change-materials-and-their-4qrepox763.pdf

Review of solid–liquid phase change materials and their encapsulation technologies

Developments in organic solid–liquid phase change materials and their applications in thermal energy storage

Fatty acids as phase change materials have attracted much attention for their various applications in building energy efficiency, solar heating systems and air-conditioning systems. After summarizing the basic characteristics of fatty acids, eutectic mixtures of fatty acids and fatty acid esters, as well as the preparation and characteristics of fatty acid composites as phase change materials (PCMs), this paper analyzes the thermal reliability and stability of fatty acids as PCMs and their heat transfer characteristics in a unit which is followed by an introduction to the energy storage systems of three kinds of fatty acids as PCMs. Besides, it also points out the future research direction of fatty acids as PCMs as a solution of the insufficiency and flaws of current researches.

Fatty acids as phase change materials: A review

The building sector is the dominant energy consumer with a total 30% share of the overall energy consumption and accounts for one-third of the greenhouse gas emissions around the world. Moreover, in recent years the energy demands for buildings have increased very rapidly due to increase in the growth rate of population and improvement in living standards of people. Furthermore, fossil fuels will continue to dominate the world's primary energy by 2030. Thus, the increase in energy demand, shortage of fossil fuels and environmental concerns has provided impetus to the development of sustainable building and renewable energy resources. Thermal energy storage is an efficient method for applying to building envelopes to improve the energy efficiency of buildings. This, in turn, reduces the environmental impact related to energy usage. The combination of construction materials and PCM is an efficient way to increase the thermal energy storage capacity of construction elements. Therefore, an extensive review on the incorporation of PCM into construction materials and elements by direct incorporation, immersion, encapsulation, shape-stabilization and form-stable composite PCMs is presented. For the first time, the differentiation between shape-stabilized and form-stable composite PCM has been made. Moreover, various construction materials such as diatomite, expanded perlite and graphite, etc. which are used as supports for form-stable composite PCM along with their worldwide availability are extensively discussed. One of the main aims of this review paper is to focus on the test methods which are used to determine the chemical compatibility, thermal properties, thermal stability and thermal conductivity of the PCM. Hence, the details related to calibration, sample preparation, test cell and analysis of test results are comprehensively covered. Finally, because of the renewed interest in integration of PCM in wallboards and concrete, an up-to-date review with focus on PCM enhanced wallboard and concrete for building applications is added.

Phase change materials integrated in building walls: A state of the art review

Synthesis and thermal properties of shape-stabilized lauric acid/activated carbon composites as phase change materials for thermal energy storage

Preparation and characteristics of microencapsulated stearic acid as composite thermal energy storage material in buildings

Comparative simulation analyses on dynamic performances of photovoltaic-thermal solar collectors with different configurations

As a kind of renewable energy, solar energy is paid more and more attention all over the world. Solar energy utilization system can be classified into two categories: thermal systems which convert solar energy to thermal energy, and photovoltaic systems which convert solar energy to electrical energy. Normally, both types of the collectors are used separately. In solar thermal system, the solar thermal energy can be used for heating working fluid via a heat collector. The conventional electrical energy is used to circulate working liquid through the collector. The use of conventional electrical energy can be avoided if combination of both types of thermal collector and photovoltaic collector is hybrid in one unit named photovoltaic–thermal collector (PV/T). In order to fully develop the applications of the photovoltaic–thermal collectors and systems, more researches on performances and characteristics of the photovoltaic–thermal collectors and systems have been carried out. This paper presents the performance evaluations and applications of the photovoltaic–thermal collectors and systems. The performances of the photovoltaic–thermal air collectors and photovoltaic–thermal water collectors are analyzed and discussed. The applications of the photovoltaic–thermal systems, such as building integrated photovoltaic–thermal systems, concentrating photovoltaic–thermal systems and photovoltaic–thermal heat pump systems are presented. Several factors affecting the performances and characteristics of the photovoltaic–thermal systems are also summarized.

Performance evaluations and applications of photovoltaic–thermal collectors and systems

This article presents the preparation and characterization of microencapsulated paraffin microcapsules with silicon dioxide (SiO2) shells as thermal energy storage materials. The microcapsules were prepared using a sol-gel method. Paraffin was used as the core material, and SiO2 prepared with methyl triethoxysilane (MTES) acted as the shell material. The morphology and particle size of the microcapsules were investigated using scanning electron microscopy (SEM). The chemical characterization of the microcapsules was measured using Fourier transform infrared spectroscope (FTIR). The crystalloid phase of the microcapsules was measured using X-ray diffraction (XRD). The thermal properties and thermal stability of the microcapsules were analyzed using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The FTIR, XRD, and SEM results showed that the paraffin was encapsulated in the shell of the SiO2. The DSC results indicated that the typical microcapsules melted at 57.96°C with a l...

Feng Shan

Papers

Synthesis and thermal properties of shape-stabilized lauric acid/activated carbon composites as phase change materials for thermal energy storage

Preparation and characteristics of microencapsulated stearic acid as composite thermal energy storage material in buildings

Comparative simulation analyses on dynamic performances of photovoltaic-thermal solar collectors with different configurations

Performance evaluations and applications of photovoltaic–thermal collectors and systems

Synthesis and Characterization of Microencapsulated Paraffin Microcapsules as Shape-Stabilized Thermal Energy Storage Materials