Phase Change Materials For Energy Storage Research Articles

Performance simulation of a natural circulation solar air heater with phase change material energy storage

The one-dimensional radial heat conduction in a phase change material (PCM) heat storage system that is encapsulated in cylindrical pipes in a single glazed flat plate natural circulation solar air heater is presented. The PCM is prepared in modules, with the modules equispaced across the absorber plate. Enthalpy method is applied to convert the relevant energy balance equations into dimensionless forms for easy tracking of the moving phase boundaries. Crank-Nicolson implicit finite difference scheme which has the features of being stable, accurate and fast in its solution is used in the solution of the governing equations subject to suitable initial and boundary conditions. The scheme is applied at each node and the resulting simultaneous equations are solved using the Gauss-Seidel iterative method. An existing computer programme in BASIC known as the EGGINC which was developed for the rectangular channel containing the PCM is modified to cylindrical coordinate for the pipes containing the PCM to predict the temperature distributions in the solar air heater. The predicted temperatures of the system are compared with the experimental data under daytime no-load condition over the ambient temperature range of 18.5-36.0OC and daily global irradiation of 4.9-20.1MJ/m 2 -day. The predicted temperatures were found to agree closely with experimental data. Keywords : Phase change material, Natural circulation; Solar air heater; implicit finite difference, Predicted temperatures

Analysis of Phase Change Energy Storage Material Selected Based on Rural Kang Body

Improving rural living thermal environment and rural residential energy-saving effect has becomes a hot society issue. As to two main problems of rural kang which are poor regenerative performance and surface temperature uneven,combined with the characteristics of phase change energy storage technologies,phase change energy storage technology was used in kang body. Grasping the properties and characteristics of different types of energy storage materials,according to the requirement of the human body comfort temperature of the kang surface,selecting phase transition temperature of the phase change energy storage materials which should be put forward kang surface comfort temperature between 24 ~ 35°Cphase change heat storage is particularly important. Through the phase change material selection, get three types of phase change thermal storage materials which are suitable for rural kang, which provides analysis method and basic reference for the selection of the phase change material to kang body, enhanced the heat storage capacity of kang,protected kang surface temperature uniformity and improved the energy-saving efficiency of housing in rural areas.

Modification of fly ash as a carrier of paraffin wax based phase change energy storage material for waste heat recovery

Modification of fly ash as a carrier of paraffin wax based phase change energy storage material for waste heat recovery

Recent Advances in Form-Stable Phase Change Materials of Polyethylene Glycol

The polyethylene glycol is a kind of phase change energy storage material with small thermal hysteresis effect, the phase change enthalpy and phase transition temperature varies with its different molecular weight. This article summarizes polyethylene glycol as research progress of phase change energy storage material, which mainly discusses the preparation methods and outlook about form-stable phase change materials.

Synthesis and Properties of a Novel Environmentally Friendly Phase Change Energy Storage Coating Additive

Waterborne polyurethane (PU) coatings are diluted with water as the medium, without volatile organic solvents and harmful to human body and environment. Adding insulation materials in building individually is a waste of resource. We found a kind of waterborne PU phase change energy storage material easily dissolved and formed film after solvent evaporating having the potential of coating. In this article, we synthesized a new kind of waterborne PU phase change energy storage coating additive via two-step synthesis method, of which a new type of aromatic tetrahydroxycompound (ATTC) is used as branch unit, 4, 4'-diphenylmethanediisocyanate (MDI) and polyethylene glycol (PEG) respectively as hard and soft segments. POM photographs show that the sphaerocrystals of this new coating additive can reach 200-500μm. The crystal structure is characterized by XRD, and the phase change unit is PEG. DSC tests show that the phase change enthalpy value of this coating additive is very high reached more than 90 J/g. The preservation of this water-soluble PU coating is relatively simple, using water as solvent, which can be easy to dissolve in water and form film after water evaporated.

Molecular dynamics simulations of nano-encapsulated and nanoparticle-enhanced thermal energy storage phase change materials

The nano-encapsulated and nanoparticle-enhanced phase change materials (PCM) which can be used for thermal energy storage have attracted much attention in recent years. To understand the heat and mass transfer mechanisms of the nano-encapsulated and nanoparticle-enhanced PCM on the molecular and atomic scale, the molecular dynamics (MD) simulations were performed in the present paper. The nano-encapsulated PCM with different shell thicknesses were fabricated by using n-octadecane as core material and SiO2 as shell material. The nanoparticle-enhanced PCM were formulated by mixing Al nanoparticles into n-nonadecane. The n-nonadecane, n-eicosane, n-heneicosane and n-docosane were used to build the pure PCM models as unencapsulated PCM systems for comparison. The results showed that the torsion and extension of the core material molecule chains could be restricted by excessive thick shell in the nano-encapsulated PCM systems. The mobility of the nanoparticle-enhanced PCM decreased with the increase of the diameter of added nanoparticles. Both excessive thick and thin shells were disadvantageous for encapsulated PCM. And the appropriate size of particle was very important for heat transfer enhancement of the nanoparticle-enhanced PCM. The MD simulations proposed herein can be helpful for the material design and performance optimization of thermal energy storage and transport PCM.

Low temperature solid state synthesis and characterisation of lauric acid/SiO2 phase change energy storage materials

Lauric acid/silicon dioxide composite phase change energy storage materials were prepared by low temperature solid state reaction using lauric acid as phase change component and sodium silicate as matrix. The structure, morphology and thermal performance of the composite were characterised by X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM), Fourier transform infrared spectrometer (FT-IR) and differential scanning calorimetry (DSC). The test results show that lauric acid materials are effectively imbedded into the net of silicon dioxide by low temperature solid state reaction. The latent heat and melting temperature of the composite are 98·94 J g−1 and 58·6°C respectively. Furthermore, the thermal conductivity of composite phase change materials is improved by using silicon dioxide as matrix material.

Influence of nanosized semiconducting additives on the properties of energy-storage phase-change materials subjected to a high-intensity electron beam

The stability of paraffin with a different concentration of copper nanopowder (a particle size of 50 and 100 nm) against a high-intensity nanosecond electron beam is studied experimentally. It is shown that the size and concentration of nanoparticles have a great influence on the thermophysical properties of the paraffin-copper oxide system and govern a phase transition in it.

Effect of d-mannitol polymorphism in its thermal energy storage capacity when it is used as PCM

The main objective of this paper is to study the possible use of d-mannitol as phase change material (PCM) for thermal energy storage. PCM are materials that have high phase change enthalpy and this thermophysical property gives them the ability to store energy as latent heat. d-mannitol is a material which has different morphological phases (polymorphism); here were studied β-form and δ-form. Different polymorphic forms produce changes on melting point of d-mannitol. For this reason it is necessary to establish a suitable working temperature range for the use of d-mannitol as phase change material. The thermal characterization was performed with DSC analysis using 0.5Kmin−1 slow-dynamic method. Polymorphism analysis of d-mannitol was analyzed to associate the thermal behavior obtained by DSC with a specific polymorphic phase. d-mannitol presented three different thermal behaviors: the first one had a melting peak at 167°C, the second was a double melting peak at 155°C and 166°C, and the third a single peak at 155°C. Due to irregular results, two working range were studied and through the thermal characterization, it was possible to define a working range where d-mannitol could be used as PCM for energy storage: this range is between 135 and 175°C. Furthermore, it was possible to differentiate two crystalline phases of d-mannitol applying FT-IR analysis and to link them with thermal behavior observed in DSC. The percentage of times each thermal behavior is observed in DSC analysis was calculated. δ-form is obtained 15.8% of analyzed cycles, the β-form appears 44.7% of times, and an intermediate transition between the two phases is found 39.5% of cycles.

Study on Paraffin/Expanded Perlite Composite Phase Change Energy-Storage Materials

Paraffin/expanded perlite composite phase change energy-storage material (PPCM) was prepared by vacuum adsorption method with expanded perlite as adsorption material and paraffin as phase change energy-storage material. The diffused-exudative circle method was used to determine that the best adsorption quantity of expanded perlite was 65%. The phase transition process and microstructure of PPCM with the best adsorption quantity were characterized by DSC and SEM. The results shown that the internal micropores of expanded perlite particles were almost completely filled with paraffin and the expanded perlite particles became close-grained particles. The phase change temperature of PPCM was basically similar with that of paraffin and its phase change latent heat was corresponded with that of paraffin in the PPCM.

Application of the Phase Change Material in Building Energy Efficiency

Phase change material possesses excellent heat storage performance that can provide some advantages to buildings. This paper introduces the properties of the phase change material , discusses the criterion of the phase change material that can be used in architecture, analysis the principles about the architectural application of phase change material, and especially discusses the ways how to use the phase-change energy storage materials for construction in building energy efficiency. Besides, this paper also analysis the future prospects and some problem still existing.

Synthesis and characterization of an environmentally friendly PHBV/PEG copolymer network as a phase change material

Novel environmentally friendly poly(hydroxybutyrate-co-hydroxyvalerate) and poly(ethylene glycol) (PHBV/PEG) copolymer networks were synthesized through free-radical solution polymerization with PHBV diacrylate (PHBVDA) and polyethylene glycol diacrylate (PEGDA) as macromers. The molecular structure of PHBV/PEG copolymer network was characterized by Fourier transform infrared (FT-IR) and 1H nuclear magnetic resonance (1H NMR). The morphology of the PHBV/PEG copolymer network was characterized by polarization optical microscopy. Thermal energy storage properties, thermal reliability and thermal stability were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis. The results indicated that the PHBV/PEG copolymer network hindered the growth of PEG crystalline segments or PHBV segments. PHBV/PEG copolymer network had a higher latent heat enthalpy, which didn’t reduce with the components of PHBV increased. Moreover, PHBV/PEG copolymer network still had good thermal stability even at 300 °C. These results suggested that such environmentally friendly copolymer network would have wide applications in phase change energy storage materials.

Preparation, characterization, and thermal properties of the microencapsulation of a hydrated salt as phase change energy storage materials

Microcapsules loaded by disodium hydrogen phosphate heptahydrate (Na2HPO4·7H2O) were prepared by means of the suspension copolymerization-solvent volatile method, with modified polymethylmethacrylate (PMMA) as coating polymer under the conditions of various organic solvents. The formation of the microencapsulated phase change materials (MEPCMs)-PMMA/Na2HPO4·7H2O was investigated and analyzed. The morphology of the resultant materials was characterized by using scanning electron microscope (SEM) and phase contrast microscope. Its final composition was confirmed by the Fourier transformation infrared (FT-IR). Thermo gravimetric analyzer (TGA) and differential scanning calorimetry (DSC) were adopted to reveal its thermal stability and thermal properties. Results indicated that the materials owned improved subcooling degree and good thermal properties, enabling the materials to be one promising phase change materials for thermal energy storage.

Dodecanoic acid as a promising phase-change material for thermal energy storage

The melting transition of dodecanoic acid (CH3(CH2)10COOH, also known as lauric acid) has been examined with a view to use for latent heat energy storage in solar thermal applications. The influence of purity (reagent grade [98% pure] compared with practical grade [<80% pure]) on the melting transition was found to be insignificant. The long-term stability of the melting transition of practical-grade dodecanoic acid was investigated by thermal cycling of samples from completely solid through complete melting and back to the solid phase, nearly 500 times. It was found that the transition enthalpy and the melting onset temperature remain within experimental uncertainty of their values, 184 J g−1 and 43.3 °C, respectively. Neither data set showed significant trends with number of thermal cycles. The freezing temperature of 41 °C for practical-grade dodecanoic acid also was stable with respect to thermal cycling, showing almost negligible hysteresis, without addition of nucleating agents. The specific heat in the region of the phase transition was determined, along with the thermal conductivity in the solid state (0.150 ± 0.004 W m−1 K−1 at 30 °C) and the volume change associated with melting (6%). Although the thermal conductivity of dodecanoic acid is low in both the solid phase and liquid phase, and thermal energy storage devices would need to be designed accordingly, dodecanoic acid is inexpensive, readily available (used as a foodstuff), has a low volume change on melting, and is stable over hundreds of thermal cycles even in practical grade, making it a promising phase-change material for thermal energy storage.

Recent research on conductive phase-change materials for energy storage

(PCM) for energy storage are materials that can store and release thermal energy through melting and solidification processes. Over the years a fair amount of work has been done to determine the suitability and properties of such materials. The first challenge was to find ways to prevent the leaking or flow of the molten paraffins. Some solutions e.g. encapsulation of the PCM by a thin polymeric shell and the formation of immiscible polymer/ PCM blends were investigated. The most recently investigated challenge is to improve the thermal conductivity of the systems, because both polymer and paraffin have relatively high thermal resistivities. A few papers were published during the past four years where the PCM was directly mixed with the conductive filler. These investigations included expanded graphite, carbon nanofibres and carbon nanotubes as fillers mixed into several paraffinbased PCMs. Generally the thermal conductivity increased, but several factors such as particle shape and orientation and particle dispersion were found to influence the extent of improvement in thermal conductivity. Another approach was the microencapsulation of a PCM by an inorganic conductive shell. The most investigated approach was the impregnation of thermally conductive, porous fillers with the liquid PCM. It was observed that the PCM was trapped inside the pores of the fillers, and generally no leakage was observed after melting of the PCM. The last approach, which involves polymers, is the formation of immiscible polymer/PCM blends containing conductive fillers. The effectiveness of such systems is determined by the extent of immiscibility of the polymer and PCM, and the strength of the interaction between the polymer or PCM and the conductive filler. To me the last approach is the most interesting from a polymer scientist’s viewpoint, because there are a number of factors that may determine the properties and effectiveness of such a phase-change system, e.g. crystallization kinetics of polymer and PCM, extent of co-crystallization, location and dispersion of conductive filler particles, extent of interaction of the filler particles with respectively the polymer and the PCM, to name a few. This may not be groundbreaking research, but the results of such research will certainly contribute to the finding of solutions for the provision of renewable energy.

Research on Thermal Character of Inorganic High Temperature Phase Change Materials

Recently advances in testing methods and study of the inorganic salt establish the high temperature phase change energy storage materials as a promising candidate for solar thermal power generation, industrial process heat use and waste heat recovery. In this paper, a phase change model related to the warming-cooling method was established to test the phase change temperature and the heat of LiCl-NaCl(1.08-1) and Ca(NO3)2-NaNO3(4-7). The result tested by the warming-cooling method is mainly in line with the one tested by other method. The data allows a promising development of the energy storage.

Preparation and Properties of Paraffin/Activated Carbon Composites as Phase Change Materials for Thermal Energy Storage

Paraffin/activated carbon composites as phase change energy storage materials were prepared by absorbing paraffin into activated carbon. In composite materials, paraffin was used as phase change material (PCM) for thermal energy storage, and activated carbon acted as supporting material, ethanol was the solvent. A series of characterization were conducted to analyse and test the performance of the composite materials, and differential scanning calorimeter (DSC) results showed that the PCM-2 composite has the melting latent heat of 51.7 kJ/kg with melting temperature of 60.4°C. Due to the capillary and surface tension forces between paraffin and activated carbon, the leakage of melted paraffin from the composites can be prevented. In a word, the paraffin/activated carbon composites have a good thermal stability and can be used repeatedly.

Design and optimization of an air heating solar collector with integrated phase change material energy storage for use in humidification–dehumidification desalination

Compared to solar water heaters, high-temperature solar air heaters have received relatively little investigation and have resulted in few commercial products. However, in the context of a humidification–dehumidification (HD) desalination cycle, air heating offers significant performance gains for the cycle. Heating at a constant temperature and constant heat output is also important for HD cycle performance. The use of built in phase change material (PCM) storage is found to produce consistent air outlet temperatures throughout the day or night. In this study, the PCM has been implemented directly below the absorber plate. Using a two dimensional transient finite element model, it is found that a PCM layer of 8cm below the absorber plate is sufficient to produce a consistent output temperature close to the PCM melting temperature with a time-averaged collector thermal efficiency of 35%. An experimental energy storage collector with an 8cm thick PCM layer was built and tested in a variety of weather and operating conditions. Experimental results show strong agreement with model in all cases.

Studies on Preparation and Properties of PEG/MMT Solid-Solid Phase Change Material

This paper details the preparation of one kind of PEG/MMT solid-solid phase change materials. With polyethylene glycol (PEG) as the phase change materials, montmorillonite (MMT) as skeletons, through the graft copolymerization method, prepare PEG/MMT solid-solid phase change energy storage materials. The structure, the phase transition behavior and thermal stability of PEG/MMT phase change materials were analyzed and studied by infrared spectroscopy (FTIR), thermogravimetry (TG) and differential scanning calorimetry (DSC), and studied the influence of different molecular weight PEG on the capability and structure of the material, polymer phase change energy storage behavior and crystallization behavior. Finally, The PEG/MMT solid-solid phase change material could improve enthalpy value and thermal stability.

Development of non-deform micro-encapsulated phase change energy storage tablets

This study evaluates the concept of developing a non-deform phase change energy storage material possessing higher thermal conductivity and energy storage density through pressure compaction process. The theoretical and experimental investigations have shown that the technique is able to reduce porosity and increase conductivity and energy storage density of a composite material. Even though there was some measure of plastoelasticity due to decompression, the average porosity was reduced from 62% to 23.8% at a relatively low compaction pressure of 2.8MPa without any structural damage to the tested sample. The mean energy storage density increased by 97% and the effective thermal conductivity also increased by twenty five times despite 10% reduction in its latent heat capacity. There is however the need for further development towards minimising the effect of decompression and achieving stronger energy storage tablets at relatively low compaction force.