Form-stable Composite Phase Change Materials Research Articles

Tetradecanol/expanded graphite composite form-stable phase change material for thermal energy storage

Natural flake graphite was chemically intercalated to prepare expandable graphite. The expandable graphite was then expanded by means of microwave irradiation to obtain expanded graphite (EG). Tetradecanol (TD)/EG composite form-stable phase change materials (PCMs) were prepared by mixing TD with EG through an autoclave method. The highest loading of TD in the composite form-stable PCMs with good form-stability was 93wt%. The composite form-stable PCMs exhibited excellent thermal energy storage capacity. The melting enthalpy (ΔHm) and crystallization enthalpy (ΔHc) of the composite form-stable PCM containing 93wt% TD were 202.6 and 201.2J/g, respectively. However, the solid–solid phase transition of TD in the composite form-stable PCMs was hindered as TD was strongly absorbed by EG. As a result, the ΔHm and ΔHc of the composite form-stable PCMs were slightly lower than the theoretical value. The thermal conductivity of the composite form-stable PCMs was greatly enhanced by EG and was increased with the increasing of EG loading. The thermal conductivity of the composite form-stable PCM containing 7wt% EG attained 2.76W/mK. Besides, effects of the prepared EG on properties of the composite form-stable PCMs were compared with those of EG derived from commercially obtained expandable graphite.

Graphene oxide improved thermal and mechanical properties of electrospun methyl stearate/polyacrylonitrile form-stable phase change composite nanofibers

In the present work, a novel PAN-based form-stable composite phase change materials with the methyl stearate (MES) encapsulated in the supporting matrices of polyacrylonitrile (PAN) nanofibers were fabricated through electrospunning for the storage and retrieval of thermal energy. Influences of graphene oxide (GO) addition on the chemical properties, structural morphologies, mechanical properties, thermal energy storage properties, thermal stability, and thermal energy storage/retrieval rates of electrospun MES/PAN/GO phase change composite nanofibers were systematically investigated by FT-IR, FE-SEM, tensile testing, DSC, TG, and measurement of melting/freezing times, respectively. The results revealed that the incorporation of GO effectively enhanced the mechanical properties, thermal stability, as well as heat storage and release rates of the phase change composite nanofibers. The averaged tensile strength of electrospun MES/PAN/GO phase change composite nanofibers increased significantly by 573 % with 10 mass% loading of GO, while elongation at break had a maximum 107 % increment when adding 3 mass% of GO. The DSC results indicated that the electrospun PAN-based phase change composite nanofibers with various GO loadings had suitable phase transition temperatures with the latent heat ranging from about 92 to 109 kJ kg−1 and exhibited good thermal reliability in terms of DSC measurements during 50 melting-freezing cycles. Moreover, the melting and freezing time were significantly decreased about 44 and 43 % for the MES/PAN/GO5, as well as 59 and 64 % for the MES/PAN/GO10 after introducing the GO into the composite nanofibers systems.

Fabrication of Stearic Acid/Silicon Dioxide Composite Shape-Stabilized Phase Change Materials for Thermal Energy Storage

Stearic acid/silicon dioxide composite shape-stabilized phase change materials with different mass fraction of stearic acid have been successfully prepared using sol-gel methods. In such an organic/inorganic composite structure, the stearic acid was used as the filling material that is the latent heat storage phase change material (PCM), and the silicon dioxide acted as the matrix material which prevented the leakage of the melted stearic acid. The structure, morphology, thermal properties, thermal conductivity of the composite PCM were determined by X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectra, Scanning electron microscope (SEM) and Differential scanning calorimetry (DSC). The results show that the form-stable composite PCM has the optimal effect, preventing the leakage of stearic acid from the matrix of silicon dioxide, emerges when the composite containing 50% (mass fraction) stearic acid. The latent heat and melting temperature of the corresponding composite PCM is measured as 85.7J/g and 52.2 °C respectively. Meanwhile, the thermal conductivity of the composite PCM could be improved effectively by using silicon dioxide as a supporting material.

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

Abstract 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.

Thermal performance of organic PCMs/micronized silica composite for latent heat thermal energy storage

The aim of this study is to prepare a form-stable composite phase change material (PCM) for latent heat thermal energy storage (LHTES) in buildings. Octadecane as paraffinic PCM and BioPCM as non-paraffinic PCM were used in the experiment as kinds of organic PCM by vacuum impregnation. It is loaded with porous of micronized silica (MS). The composite PCMs were characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) analysis techniques and determination of thermal properties and thermal reliability of the composite PCMs were analyzed using differential scanning calorimetry (DSC) and thermo gravimetric analyses (TGA) analysis techniques. SEM results showed that ocatadecane and BioPCM confined into porous of MS. FT-IR analysis indicated that the composite formation of porous MS and octadecane and BioPCM were physical. 241.8J/g of latent heat of composites, 26.9°C of melting point, and 120.0J/g of it, 22.1°C, was respectively measured by DSC analysis. The values for latent heat capacity reduction ratio of BioPCM as non-paraffinic PCM and octadecane as paraffinic PCM were nearly 29% and 56%. Furthermore, TGA analysis result showed that composite PCM had good thermal durability in the working temperature range. As a result, this composite PCM could be considered to have good potential for thermal energy storage because of its good thermal energy storage properties, thermal and chemical reliability.

Structures and thermal properties of fatty acid/expanded perlite composites as form-stable phase change materials

Capric acid/expanded perlite (CA/EP) and capric-stearic acid/expanded perlite (CA-SA/EP) composites were prepared. The composite phase change materials (PCMs) were characterized by scanning electron microscopy (SEM) and Fourier transformation infrared spectroscopy (FT-IR). The thermal properties and thermal reliability of the composites were determined by differential scanning calorimetry (DSC), melting-freezing test, polarization microscope equipped with hot stage. Results show that the form-stable composite PCM has an optimal mass ratio of 50% fatty acid. The fatty acid is impregnated into EP by physical attraction. The measured latent heat values of CA/EP composites are 87.3J/g for the melting process and 89.0J/g for the freezing process. The corresponding values of the CA-SA/EP are 82.1J/g and 82.6J/g, respectively. The DSC, FTIR, and thermal cycling test results show that the thermal reliability of the composite PCMs imperceptibly changes. All of the conclusions indicate that the composites have good thermal and chemical stability.

Facile synthesis and performances of PEG/SiO2 composite form-stable phase change materials

A facile route based on ultrasound-assisted sol–gel method has been developed and applied to rapid synthesis of polyethylene glycol (PEG)/silicon dioxide (SiO2) composite form-stable phase change materials (PCMs) without co-solvent and surfactant. This method was carried out under ultrasonic power of 300W using HCl and Na2CO3 as the acidic and alkaline catalyst, respectively. The temperature is below 50°C. The PCMs were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC) and thermogravimetric analysis apparatus (TGA) measurements. The PCMs display low density, high volume energy density, excellent form-stable effect, good phase-change and temperature control performance, which are very important for the actual application of PCMs in energy-saving construction materials.

Research of Thermo-Regulating Fibers Based on the Crosslinked Composite Phase Change Materials of PEGA

The novel form-stable composite phase change materials (PCMs) of crosslinked PEGA and P(PEGA-HAM)/PEG gels were synthesized, which based on PEGA . Using crosslinked PEGA and P(PEGA-HAM)/PEG gels as the working substance , PP/PCM thermo-regulating fibers were prepared by blends via melt spinning respectively. TGA results indicate that the crosslinked form-stable PCMs have good thermal stability. The morphology of the surface of PP/PCM thermo-regulating fibers smooth mainly by SEM. The breaking strength of thermo-regulating fibers first increases and then decreases when increased some content of PCM. DSC results indicate the phase enthalpy of PEGA crosslinked gel and its the blend fibers with PP are 122.97J/g and 13.83J/g, while that of P(PEGA-HAM)/PEG crosslinked networks gel and its the blend fibers with PP are 107.48J/g and 4.62J/g respectively.

Preparation, characterization and thermal properties of dodecanol/cement as novel form-stable composite phase change material

This research was aimed at preparing novel form-stable composite phase change material (PCM) for thermal heat storage application in buildings. Dodecanol was incorporated into cement through vacuum impregnation technique. The microstructure, chemical compatibility, thermal properties, thermal stability and reliability were determined by environmental scanning electron microcope (ESEM), Fourier transformation infrared spectrum analysis (FT-IR), differential scanning calorimetry (DSC), thermal gravimetric analyzer (TGA) and thermal cycling test. Test results showed that the maximum mass fraction of dodecanol retained in cement without seepage was 9%. This composite was characterized as form-stable composite. FT-IR results indicated that the form-stable composite is chemically stable. The melting temperature and latent heat of the form-stable composite were found to be 21.06°C and 18.39J/g. TGA and thermal cycling test results revealed that the form-stable composite is thermally stable and reliable. It can therefore be concluded that the prepared form-stable composite is a potential candidate for thermal energy storage application in buildings. With the help of an example it is shown that the 2 storey residential building has the capacity to store 2448MJ of thermal energy. This, in turn, will have significant impact in reducing the energy consumption of buildings.

CaCl2·6H2O/Expanded graphite composite as form-stable phase change materials for thermal energy storage

In this study, CaCl2·6H2O/expanded graphite (EG) composite was prepared as a novel form-stable composite phase change material (PCM) through vacuum impregnation method. CaCl2·6H2O used as the PCM was dispersed by surfactant and then, was absorbed into the porous structure of the EG. The surfactant was used to enhance the bonding energy between CaCl2·6H2O and EG, which fulfilled the composites with good sealing performance and limited the leakage of the inside CaCl2·6H2O. Differential scanning calorimetry and thermal gravimetric analysis show that all the composite PCMs possess good thermal energy storage behavior and thermal stability. Thermal conductivity measurement displays that the conductivities of the samples have been significantly improved due to the highly thermal conductive EG. The thermal conductivity of the sample including 50 mass% CaCl2·6H2O (8.796 W m−1 K−1) is 14 times as that of pure CaCl2·6H2O (0.596 W m−1 K−1). Therefore, the obtained composite PCMs are promising for thermal energy storage applications.

Preparation and properties of highly conductive palmitic acid/graphene oxide composites as thermal energy storage materials

PA/GO (palmitic acid/graphene oxide) as PCMs (phase change materials) prepared by vacuum impregnation method, have high thermal conductivity. The GO (graphene oxide) composite was used as supporting material to improve thermal conductivity and shape stabilization of composite PCM (phase change material). SEM (Scanning electronic microscope), FT-IR (Fourier transformation infrared spectroscope) and XRD (X-ray diffractometer) were applied to determine microstructure, chemical structure and crystalloid phase of palmitic acid/GO composites, respectively. DSC (Differential scanning calorimeter) test was done to investigate thermal properties which include melting and solidifying temperatures and latent heat. FT-IR analysis represented that the composite instruction of porous palmitic acid and GO were physical. The temperatures of melting, freezing and latent heats of the composite measured through DSC analysis were 60.45, 60.05 °C, 101.23 and 101.49 kJ/kg, respectively. Thermal cycling test showed that the form-stable composite PCM has good thermal reliability and chemical stability. Thermal conductivity of the composite PCM was improved by more than three times from 0.21 to 1.02. As a result, due to their acceptable thermal properties, good thermal reliability, chemical stability and great thermal conductivities, we can consider the prepared form-stable composites as highly conductive PCMs for thermal energy storage applications.

Characterization and thermal conductivity of modified graphite/fatty acid eutectic/PMMA form-stable phase change material

We prepared and characterized a form-stable composite phase change material (PCM) with higher thermal conductivity. Capric acid(CA)-myristic acid(MA) eutectic as core, poly-methyl methacrylate (PMMA) as supportive matrix and modified graphite (MG) powders serving as the thermal conductance improver were blended by bulk-polymerization method. The composite PCMs with different MG mass fraction (2%, 5%, 7%, 10% and 15%) were characterized by FT-IR, SEM, DSC technique and mechanical tests. Thermal conductivities of the composites were measured by transient hot-wire method. The results indicate that MG powders have been successfully inserted into the CA-MA/PMMA matrix without any chemical reaction with each other. The MG/CA-MA/PMMA composites maintain good thermal storage performance while the thermal conductivity has been enhanced significantly. The composite PCM added with 15 wt% MG powders increases approximately as 195.9% in thermal conductivity. Moreover, the thermal conductivity improvement of the composite PCMs is also verified by the melting-freezing experiment, which is profitable for the heat transfer efficiency in latent heat thermal energy storage system.

Preparation, characterization and thermal properties of Lauryl alcohol/Kaolin as novel form-stable composite phase change material for thermal energy storage in buildings

This research was aimed at developing novel form-stable composite phase change material (PCM) by incorporation of Lauryl alcohol (LA) into Kaolin (KO) through vacuum impregnation. The composite PCM was characterized by using SEM and FT-IR. Thermal properties, thermal stability and reliability of the composite were determined by using DSC, TGA and thermal cycling test. Thermal performance of cement paste composite PCM panel was also evaluated. Test results showed that the maximum fraction of LA retained in KO was 24%. SEM images showed that LA was held by the porous and layered structure of KO due to the effect of capillary and surface tension forces. FT-IR results indicated that the composite PCM has good chemical stability and the interaction between LA and KO is physical. The melting temperature and latent heat of the composite PCM were measured as 19.14 °C and 48.08 J/g by DSC analysis. TGA and thermal cycling test revealed that the composite PCM is thermally stable and reliable. Thermal performance test showed that the cement paste panel with composite PCM reduced the indoor temperature by 4 °C. It can therefore be concluded that the prepared composite PCM is a potential candidate for thermal energy storage in buildings.

Impregnation of a porous material with a PCM on a cotton fabric and the effect of vacuum on thermo-regulating textiles

The purpose of this study was the preparation of a form-stable composite phase change material (PCM) by incorporation of n-nonadecane within the expanded dolomite (ED). In this investigation, two approaches called impregnation treatment with vacuuming and impregnation by magnetic stirrer were used. This method was first proposed for textile thermal protection. In this method, n-nonadecane was applied as the phase change material and ED as the supporting in order to prepare and construct the composite PCM. Composite properties were determined by Fourier transformation infrared spectroscope and scanning electronic microscope (SEM) techniques and the heat transfer measurement and differential scanning calorimeter (DSC) were used to determine the thermal properties of composite on fabrics. Also, moisture transfer properties were measured. The SEM results showed that the n-nonadecane was well absorbed in the porous network of the ED. DSC analysis and heat transfer also indicated that fabric temperature range for the amount of coated PCM depends on its area; further, by adding composite to the fabric surface, thermal transfer could be reduced. The maximum percentages of n-nonadecane within ED in the composite PCM1 and PCM2 were measured to be about 90 and 70 mass%, respectively. Thus, the composite PCM1 can be considered as a form-stable composite change phase materials.

Development of form-stable composite phase change material by incorporation of dodecyl alcohol into ground granulated blast furnace slag

This research was aimed at developing form-stable composite phase change material (PCM) by incorporating dodecyl alcohol (DA) into Ground granulated blast furnace slag (GGBS) through vacuum impregnation. The composite PCM were characterized by using Scanning electron microscope (SEM) and Fourier transformation infrared spectrum analysis (FT-IR). The thermal properties, thermal stability and reliability of the composite were determined by using Differential scanning calorimetry (DSC), Thermal gravimetric analyzer (TGA) and thermal cycling test.Test results showed that the maximum percentage of DA retained in GGBS without seepage was 11%. This composite was therefore called as form-stable composite PCM. FT-IR results validate that the components of the form-stable composite are chemically stable. The melting and freezing temperatures of the composite PCM were found to be 21.16°C and 19.1°C while the latent heat of melting and freezing were 22.51J/g and 21.62J/g. The results of TGA and thermal cycling test confirmed that the form-stable composite is thermally stable and reliable. It can therefore be concluded that the prepared form-stable composite is a potential candidate for thermal energy storage in buildings.

Thermal and mechanical properties of nanofibers-based form-stable PCMs consisting of glycerol monostearate and polyethylene terephthalate

An innovative type of nanofibers-based form-stable composite phase change materials for the storage and retrieval of thermal energy was successfully prepared by encapsulating glycerol monostearate (GMS) into the porous structure of polyethylene terephthalate (PET)-supporting matrices on the nanoscale through electrospinning. The field-emission scanning electron microscopy and transmission electron microscopy images revealed that the composite nanofibers possessed desired morphologies with the average fiber diameters ranging from about 290 to 1000 nm which increased with the contents of GMS. The two phase separation (e.g., GMS phase and PET phase) was clearly observed from the images. When GMS content reached 60 %, the amount of the GMS distributing on the surface of the composite nanofibers was significantly increased during the electrospinning. The Fourier transform infrared spectroscopy spectrum proved that the PET supporting matrices were physically combined with GMS molecules. The differential scanning calorimetry analysis indicated that the GMS/PET composite nanofibers had reversible phase change behaviors, and the melting enthalpies increased from 32.63 to 66.99 kJ kg−1 with increasing GMS amount. The TG results showed that both the onset thermal degradation temperature and charred residue of the GMS/PET composite nanofibers at 700 °C were higher than those of pristine GMS powder owing to the better thermal stability of the PET molecules. The tensile testing revealed that the averaged tensile strength and elongation at break of the all GMS/PET composite nanofibers varied from 3.29 to 10.30 MPa and from 2.42 to 42.30 %, respectively.

Shape-stabilized phase change materials with high thermal conductivity based on paraffin/graphene oxide composite

This paper mainly focuses on the preparation, characterization, thermal properties and thermal stability and reliability of new form-stable composite phase change materials (PCMs) prepared by vacuum impregnation of paraffin within graphene oxide (GO) sheets. SEM and FT-IR techniques and TGA and DSC analysis are used for characterization of material and thermal properties. The composite PCM contained 48.3wt.% of paraffin without leakage of melted PCM and therefore this composite found to be a form-stable composite PCM. SEM results indicate that the paraffin bounded into the pores of GO. FT-IR analysis showed there was no chemical reaction between paraffin and GO. Temperatures of melting and freezing and latent heats of the composite were 53.57 and 44.59°C and 63.76 and 64.89kJ/kg, respectively. Thermal cycling tests were done by 2500 melting/freezing cycling for verification of the form-stable composite PCM in terms of thermal reliability and chemical stability. Thermal conductivity of the composite PCM was highly improved from 0.305 to 0.985 (W/mk). As a result, the prepared paraffin/GO composite is appropriate PCM for thermal energy storage applications because of their acceptable thermal properties, good thermal reliability, chemical stability and thermal conductivities.

Preparation and Performance of Myristic Acid/Silicon Dioxide Composites as Thermal Energy Storage Materials

The myristic acid/silicon dioxide composite materials were prepared by sol-gel methods. The myristic acid was used as the phase change material for thermal energy storage, with the SiO2 acting as the supporting material. The structural analysis of these form-stable myristic acid /SiO2 composite phase change materials was carried out using Fourier transformation infrared spectroscope (FT-IR).The microstructure of the form-stable composite phase change materials was observed by a scanning electronic microscope (SEM). The thermal properties was investigated by a differential scanning calorimeter (DSC).The SEM results showed that the myristic acid was well dispersed in the porous network of SiO2. And the new nanocomposite material has favorable thermal storage capacity and can be applied to solar energy storage, industrial waste heat, recovery of waste heat and as civilian structural materials.

Preparation and thermal energy storage properties of building material-based composites as novel form-stable PCMs

In this study, ten kinds of composite phase change materials (PCMs) were prepared by impregnation of xylitol penta palmitate (XPP) and xylitol penta stearate (XPS) esters into gypsum, cement, diatomite, perlite and vermiculite via vacuum adsorption method. The form-stable composite PCMs were characterized by using SEM and FT-IR, DSC and TG analysis techniques. The maximum impregnation ratio of both XPP and XPS into gypsum, cement, perlite, diatomite, and vermiculite were found to be 22, 17, 67, 48 and 42wt%, respectively. The DSC results showed that the melting temperatures and latent heat capacities of the composite PCMs varied from 20°C to 35°C and from 38J/g to 126J/g. TG investigations revealed that the composite PCMs had excellent thermal durability above their working temperature ranges. The thermal cycling test also exhibited that the composite PCMs had good thermal reliability and chemical stability. In addition, thermal conductivities of the composite PCMs were increased by addition of EG in mass fraction of 10%. All of the conclusions indicated that among the prepared composite PCMs, especially perlite and diatomite based-PCMs are potential candidates for energy storage applications such as solar heating and cooling in buildings since they had relatively higher latent heat capacity.

Thermal energy storage properties and thermal reliability of some fatty acid esters/building material composites as novel form-stable PCMs

In this study, thermal energy storage properties and thermal reliability some fatty acid esters/building material composites as novel form-stable phase change materials (PCMs) were investigated. The form-stable composite PCMs were prepared by absorbing galactitol hexa myristate (GHM) and galactitol hexa laurate (GHL) esters into porous networks of diatomite, perlite and vermiculite. In composite PCMs, fatty acid esters were used as energy storage materials while diatomite, perlite and vermiculite were used as building materials. The prepared composite PCMs were characterized using scanning electron microscope (SEM) and Fourier transformation infrared (FT-IR) analysis techniques. The SEM results proved that the esters were well confined into the building materials. The maximum mass percentages of GHM adsorbed by perlite, diatomite and vermiculite were determined as 67, 55 and 52wt%, respectively as they were found for GHL to be 70, 51 and 39wt%, respectively. Thermal properties and thermal stabilities of the form-stable composite PCMs were determined using differential scanning calorimetry (DSC) analysis. The DSC results showed that the melting temperatures and latent heat values of the PCMs are in range of about 39–46°C and 61–121J/g. The thermal cycling test revealed that the composite PCMs have good thermal reliability and chemical stability. TG analysis revealed that the composite PCMs had high thermal durability property above their working temperature ranges. Moreover, the thermal conductivities of the PCMs were increased by adding the expanded graphite (EG) in mass fraction of 5%. Based on all results, it was also concluded that the prepared six composite PCMs had important potential for thermal energy storage applications such as solar space heating and cooling applications in buildings.