Candidate For Thermal Energy Storage Research Articles

A novel candidate shape-stabilized phase change material for building energy conservation based on lauric acid/roasted iron tailings-expanded graphite

This study presents the fabrication of a novel shape-stabilized phase change material (SSPCM) characterized by high thermal capacity and heat transfer efficiency. The material was composed of lauric acid (LA) embedded in roasted iron tailings (RIT) and expanded graphite (EG), utilizing a straightforward, low-cost, and direct impregnation method. The as-prepared LA/RIT-EG SSPCM underwent a comprehensive analysis of leakage tests, surface morphology, chemical compatibility, phase change properties, thermal stability, and reliability. Furthermore, the heat transfer efficiency and thermal conductivity were measured through cooling tests and a laser thermal conductivity analyzer, respectively. The LA/RIT-EG formulation demonstrated an ability to absorb 61.57 wt% LA without leakage, maintaining excellent form-stability with a mass fraction proportion of 29:9.43 for RIT and EG. DSC results revealed phase temperatures and latent heats of 42.49–46.31 °C and 108.1–113.1 J/g, respectively. Compared to pure LA, LA/RIT-EG exhibited a 489.7 % increase in thermal conductivity. Additionally, heat storage and release rates were improved by 81.25 % and 88.24 %, respectively. The study elucidated the mechanism behind the enhancement in encapsulation capacity and thermal conductivity by RIT-EG, validated through specific surface area and wettability tests. Overall, the results suggest that LA/RIT-EG, characterized by high thermal capacity and heat transfer efficiency, holds promise as a potential candidate for thermal energy storage, particularly in the context of energy conservation in buildings.

Investigation of forced convection of a novel hybrid nanofluid containing NEPCM in a square microchannel: Application of single-phase and Eulerian-Eulerian two-phase models

In the present study, laminar forced convection flow and heat transfer of novel hybrid nanofluid of Al 2 O 3 -n-octadecane/water through a horizontal microchannel under a constant wall heat flux condition are investigated. N-octadecane is regarded as a nano-encapsulated phase change material (NEPCM). Simulations are performed utilizing single-phase and Eulerian-Eulerian two-phase models. Governing equations are discretized by finite volume method and then solved using SIMPLE algorithm. Effects of nanoparticles volume fraction ( φ ), Reynolds number ( Re ), and melting range ( T mr ) on thermal and hydrodynamic parameters of hybrid nanofluid are evaluated. It is shown that predictions by Eulerian-Eulerian approach are more accurate than those by single-phase approach when compared to available experimental data. Addition of Al 2 O 3 and n-octadecane nanoparticles to water-based fluid leads to a reduction in fluid and wall temperatures, which is intensified at higher φ and Re . Also, these nanoparticles do not have a significant effect on hydrodynamic development of flow, while they delay its thermal development. NEPCM with a higher T mr only slightly improves thermal performance of hybrid nanofluid, which is more noticeable in single-phase procedure. Total efficiency of hybrid nanofluid ( η hnf ) is amplified by raising φ for both approaches. This augmentation is more evident in Eulerian-Eulerian model due to better thermal and hydrodynamic performances. Maximum increases in η hnf concerning single-phase and Eulerian-Eulerian models are 27% and 60%, respectively, occurring at φ Al 2 O 3 = 1 % and φ n ‐ octadecane = 10 % . Therefore, this type of hybrid nanofluids, because of its enhanced thermo-physical properties, can be considered as a suitable candidate for thermal energy storage, heat transfer, and renewable energy applications.

Multiple H-Bonding Cross-Linked Supramolecular Solid-Solid Phase Change Materials for Thermal Energy Storage and Management.

Solid-solid phase change materials (SSPCMs) are considered among the most promising candidates for thermal energy storage and management. However, the application of SSPCMs is consistently hindered by the canonical trade-off between high TES capacity and mechanical robustness. In addition, they suffer from poor recyclability due to chemical cross-linking. Herein, a straightforward but effective strategy for fabricating supramolecular SSPCMs with high latent heat and mechanical strength is proposed. The supramolecular polymer employs multiple H-bonding interactions as robust physical cross-links. This enables SSPCM with a high enthalpy of phase transition (142.5 J g-1 ), strong mechanical strength (36.9MPa), and sound shape stability (maintaining shape integrity at 120 °C) even with a high content of phase change component (97 wt%). When SSPCM is utilized to regulate the operating temperature of lithium-ion batteries, it significantly diminishes the battery working temperature by 23 °C at a discharge rate of 3 C. The robust thermal management capability enabled through solid-solid phase change provides practical opportunities for applications in fast discharging and high-power batteries. Overall, this study presents a feasible strategy for designing linear SSPCMs with high latent heat and exceptional mechanical strength for thermal management.

Shape-stabilized phase change material based on MOF-derived oriented carbon nanotubes for thermal management of lithium-ion battery

Phase change material (PCM) is a suitable candidate for thermal energy storage as its high latent heat and narrow temperature fluctuations during phase change process. However, low thermal conductivity and poor shape stability seriously hinder the large-scale utilization of phase change materials. Here we fabricated the highly oriented N-doped carbon nanotubes (N-CNTs) derived from metal-organic frameworks (MOFs) by a facile and high-yield strategy. Then the N-CNTs/docosane composite PCM (CPCM) was fabricated with the as-synthesized N-CNT as the supporting material and docosane as the functional material. It can be revealed that the shape stability of docosane was significantly enhanced by integrating with N-CNTs. The CPCM possessed a thermal conductivity increased by 197.47 % (0.5286 W·m−1·K−1) than that of docosane. Besides, the CPCM exhibited an excellent cycle performance with ultrahigh retention of latent heat (99.95 % in melting process and 99.94 % in freezing process) after 20 melting-freezing cycles. Further exploration reveals that the electronic conductivity of the CPCM increases to 2928.26 S·cm−1. The CPCM was then used to fabricate a flexible thin film for the thermal management of lithium-ion battery (LIB). In the charge-discharge cycle performance test, the maximum temperature of LIB is about 2 °C lower by the utilization of CPCM film. This exploration exhibits great potential in stimulating the development of PCMs and provides a new technology for LIB thermal management.

A novel biomass solid waste-based form-stable phase change materials for thermal energy storage

To improve the energy storage capacity of phase change materials, the influence of plant ash, a typical biomass solid waste, with different particle sizes on the encapsulation of palmitic acid has been investigated to find better supporting materials for preparing form-stable phase change material (FSPCM). During the experiment, palmitic acid/Plant ash composites with different mass fractions of palmitic acid were fabricated by the direct impregnation method. And the packaging capability, particle size distribution, surface area, microstructure, chemical compatibility, and thermal properties were investigated systematically. The particle size distribution test shows that the mean-volume diameter of plant ash sieved by 30–60 mesh (PLA-1) and PLA sieved by −60 mesh (PLA-2) is 60.21 and 41.21 μm, respectively. The DSC results show that the enthalpy of PA/PLA-2 FSPCM is 99.7 J/g, which is almost twice that of PA/PLA-1 FSPCM. In short, as-prepared PA/PLA FSPCM exerts a bigger energy storage capacity, which makes it a great candidate for thermal energy storage.

Sustainable Thermal Energy Batteries from Fully Bio-Based Transparent Wood.

The sustainable development of functional energy-saving building materials is important for reducing thermal energy consumption and promoting natural indoor lighting. Phase-change materials embedded in wood-based materials are candidates for thermal energy storage. However, the renewable resource content is usually insufficient, the energy storage and mechanical properties are poor, and the sustainability aspect is unexplored. Here a novel fully bio-based transparent wood (TW) biocomposite for thermal energy storage, combining excellent heat storage properties, tunable optical transmittance, and mechanical performance is introduced. A bio-based matrix based on a synthesized limonene acrylate monomer and renewable 1-dodecanol is impregnated and in situ polymerized within mesoporous wood substrates. The TW demonstrates high latent heat (89Jg-1 ) exceeding commercial gypsum panels, combined with thermo-responsive optical transmittance (up to 86%) and mechanical strength up to 86MPa. The life cycle assessment shows that the bio-based TW has a 39% lower environmental impact than transparent polycarbonate panels. The bio-based TW holds great potential as scalable and sustainable transparent heat storage solution.

Mechanically strong, flexible, and multi-responsive phase change films with a nacre-mimetic structure for wearable thermal management

Phase change materials (PCMs) are a highly promising candidate for thermal energy storage owing to their large latent heat and chemical stability. However, their intrinsic brittle induces poor flexibility and low mechanical strength, which limits them use for wearable thermal management. And, the electrical insulation and weak solar absorption make them lack multi-responsive capability. Herein, we report a facile strategy to synthesize mechanically strong and flexible multi-responsive phase change films by stirring an aqueous dispersion of cellulose nanofibrils (CNFs), MXene (Ti2C3) nanosheets, and polyethylene glycol (PEG), followed by air-drying self-assembly and coating with hydrophobic fluorocarbon. The hydrogen bonds and nacre-mimetic synergistic toughening networks formed by ternary CNFs, Ti2C3 nanosheets, and PEG endow films with high mechanical strength (16.7 MPa) and strain (10.4%), which are 18.6 and 8.7 times higher than those of pure PEG film, respectively. The films exhibit outstanding flexibility and do not crack or fracture even when bent, twisted, and folded into a complex small boat. Meanwhile, the laminar structure formed by the self-assembly Ti3C2 nanosheets enhances electrical conductivity (3.95 S/m) and solar absorption, affording excellent electro-thermal (68.3%–81.0%) and solar-thermal (85.6%–90.6%) conversion efficiency, thus achieving multi-response to external stimuli (electron/solar radiation). In addition, the as-prepared films also deliver large latent heat (136.1 J/g), outstanding cyclic and shape stability, leak-free encapsulation even under compressed at above 5000 times its weight, excellent hydrophobicity (131.4°), and self-cleaning function. This work paves the way for developing flexible, mechanically strong, and self-cleaning phase change film with multi-responsive function for wearable thermal management devices under high humidity condition.

Experimental studies on thermophysical properties of protic ionic liquids for thermal energy storage systems

Energy storage chemicals play an important role in the design of thermal energy storage systems due to their thermal and chemical properties. In this regard, ionic liquids can be used as a potential for thermal energy storage owing to their remarkable thermophysical properties. At present, little research has been done in this field. In this project, protic ionic liquids 2-hydroxyethylammonium lactate [HEA]La, bis(2-hydroxyethylammonium) lactate [BHEA]La and tris(2-hydroxyethylammonium) lactate [THEA]La were synthesized. The synthesized ionic liquids have low toxicity, high thermal stability, easy and economical synthesis with suitable physical and chemical properties for thermal energy storage systems. In the following, thermophysical measurements such as thermal conductivity, heat capacity, surface tension, density, speed of sound, and electrochemical potential windows for the pure ionic liquids at different temperatures were performed to evaluate the efficiency of these systems as thermal energy storage. The differential scanning calorimetry analysis shows that the ionic liquid 2-hydroxyethylammonium lactate has a higher heat capacity at 1.800 J·g−1·K−1 at T = 298.15 K than the other two ionic liquids due to its small cation and structure. Heat capacity also increases with increasing temperature. The electrochemical potential window values for the ILs [HEA]La, [BHEA]La and [THEA]La were obtained at 2.5 V and 2.2 V, and 1.7 V, respectively. Efficient thermal energy storage systems have a sufficiently high heat capacity and thermal energy density with beneficial thermal conductivity. The ionic liquid 2-hydroxyethylammonium lactate with a maximum thermal conductivity of 0.255 W·m−1·K−1 compared to the other two ionic liquids is recommended as an appropriate candidate for thermal energy storage.

Design and development of novel LiCl–NaCl–KCl–ZnCl2 eutectic chlorides for thermal storage fluids in concentrating solar power (CSP) applications

Molten chloride mixtures are of great scientific and technical interest for sensible heat storage in solar power generation. In this work, the condensed phases in a LiCl–NaCl–KCl–ZnCl 2 multicomponent system were critically evaluated and predicted via literature review and simulations of LiCl–KCl and KCl–ZnCl 2 systems. Two innovative LiCl–NaCl–KCl–ZnCl 2 quaternary chloride systems with low melting points were proposed and developed on the basis of a thermodynamic design. The thermal–physical properties of these two eutectic compositions, including melting point, mixing enthalpy, specific heat capacity, density, thermal conductivity, and mass loss, were then experimentally determined. The experimental results were consistent with the theoretical predictions. The novel quaternary eutectic chlorides with excellent thermophysical properties developed herein are potential candidates for thermal energy storage and transfer materials in concentrating solar power plants. • Thermodynamic prediction of LiCl–NaCl–KCl–ZnCl 2 system was performed via CALPHAD. • Two novel quaternary eutectic chlorides were successfully designed for thermal energy storage and transfer. • Thermophysical properties of the system were determined by experiment and classical prediction method. • Thermodynamic performance of the novel chlorides was substantially improved compared with other potential materials. • The novel quaternary eutectic chlorides were proposed as potential candidate materials in CSP applications.

Stable salt hydrate-based thermal energy storage materials

Heating and cooling systems in building infrastructure utilize conventional materials that account for a considerable amount of energy usage and waste. Phase change material (PCM) is considered a promising candidate for thermal energy storage that can improve energy efficiency in building systems. Here, a novel salt hydrate-based PCM composite with high energy storage capacity , relatively higher thermal conductivity , and excellent thermal cycling stability was designed and developed. The thermal cycling stability of the PCM composite was enhanced by using dextran sulfate sodium (DSS) salt as a polyelectrolyte additive, which significantly reduced the phase segregation of salt hydrate . The energy storage capacity and the thermal conductivity of the composite were enhanced by the addition of various graphitic materials along with Borax nucleator. A significant increase in thermal cycling stability was observed for the DSS-modified composite, with over 100 thermal cycles without degradation. The final PCM composite exhibited as much as 290% increase in energy storage capacity relative to the pure salt hydrate, and approximately 20% increase in thermal conductivity. In addition, the PCM composite developed can be produced at larger scale, and can potentially change the future of heating/cooling system in building infrastructure. • Polyelectrolyte-stabilized salt hydrate phase change material (PCM). • Reduced phase separation of sodium sulfate decahydrate upon thermal cycling. • Significant increase in thermal cycling stability up to 100 thermal cycles. • PCM composite exhibited 290% increase in energy storage capacity. • High throughput processing technique.

Review of Technologies and Recent Advances in Low-Temperature Sorption Thermal Storage Systems

Sorption thermochemical storage systems can store thermal energy for the long-term with minimum amount of losses. Their flexibility in working with sustainable energy sources further increases their importance vis-à-vis high levels of pollution from carbon-based energy forms. These storage systems can be utilized for cooling and heating purposes or shifting the peak load. This review provides a basic understanding of the technologies and critical factors involved in the performance of thermal energy storage (TES) systems. It is divided into four sections, namely materials for different sorption storage systems, recent advances in the absorption cycle, system configuration, and some prototypes and systems developed for sorption heat storage systems. Energy storage materials play a vital role in the system design, owing to their thermal and chemical properties. Materials for sorption storage systems are discussed in detail, with a new class of absorption materials, namely ionic liquids. It can be a potential candidate for thermal energy storage due to its substantial thermophysical properties which have not been utilized much. Recent developments in the absorption cycle and integration of the same within the storage systems are summarized. In addition, open and closed systems are discussed in the context of recent reactor designs and their critical issues. Finally, the last section summarizes some prototypes developed for sorption heat storage systems.

Design and preparation of Ag modified expanded graphite based composite phase change materials with enhanced thermal conductivity and light-to-thermal properties

Phase change materials (PCMs) is an excellent performance candidate for thermal energy storage and utilization. However, low thermal conductivity and low light-to-thermal conversion efficiency of PCMs are the serious limitation factors for highly efficient energy storage and photothermal conversion. In this paper, we reported a novel composite PCM based on lauric acid (LA) as the PCM supported by Ag nanoparticles modified expanded graphite (Ag-EG). The composite PCM of Ag-EG/LA possessed good energy thermal storage properties, which melted at 47.2 °C with the latent heat of 129.5 J/g at the LA maximum loading of 70.2%. Meanwhile, based on the high thermal conductivity and local surface plasma resonance effect of Ag, the composite (Ag-EG/LA) exhibits improved thermal conductivities (2.85 W/(m•K)) and high light-to-thermal energy conversion efficiency (η=81.2%). Moreover, the TGA and thermal cycles test results shown that Ag-EG/LA have good thermal stability and reliability. Hence, this novel composite of Ag-EG/LA could be potentially applicated in solar energy harvesting system and electric devices for thermal energy management.

Bifunctional biomorphic SiC ceramics embedded molten salts for ultrafast thermal and solar energy storage

Phase change materials (PCMs) are regarded as one of the most promising candidates for thermal energy storage due to possessing large energy storage densities and maintaining nearly a constant temperature during charging/discharging processes. However, the intrinsically low thermal conductivity of PCMs has become a bottleneck for rapid energy transport and storage. Here, we present a strategy to achieve ultrafast solar and thermal energy storage based on biomorphic SiC skeletons embedded NaCl–KCl molten salts. A record-high thermal conductivity of 116 W/mK is achieved by replicating cellular structure of oak wood, leading to an ultrafast thermal energy storage rate compared with molten salts alone. By further decorating TiN nanoparticles on SiC skeletons, the solar absorptance is enhanced to be as high as 95.63% via exciting broadband plasmonic resonances. Excellent thermal transport and solar absorption properties enable designed composites to have bifunctional capabilities of harvesting both thermal energy and solar energy very rapidly. This work opens a new route for the design of bifunctional energy storage materials for ultrafast solar and thermal energy storage.

Thermal performance of bare and finned tubes submersed in nano-PCM mixture

Phase change materials (PCMs) are well accepted as excellent candidates for thermal energy storage and many other important applications. One of their main drawbacks is the poor thermal conductivity which impairs their thermal performance. Many methods were proposed to solve this problem among which fins and nano-PCMs occupy leading positions in terms of efficiency and reliability. In this paper a homebuilt numerical code is used to calculate and compare the numerical predictions of finned and finless tubes submersed in PCM and nano-PCM. For both finned and finless tubes it is found that the increase in the nanoparticles fraction increases the interface position and the interface velocity and decreases the time for complete phase change. For the case of finless tube the addition of 10% of Al2O3 nanoparticles to the PCM and comparing the results with the case of finless tube in pure PCM are found to increase the interface position by 25%. On the other hand, the addition of 10% Al2O3 nanoparticles to the four fins tube and comparing the results with the case finless tube in pure PCM are found to reduce the complete solidification time by 9.1%.

Composite phase change materials with heat transfer self-enhancement for thermal energy storage

In this study, a heat transfer self-enhancement mechanism in novel composite phase change materials (CPCMs) was proposed and realized. The study aimed to develop aluminium ammonium sulfate dodecahydrate (NH4Al(SO4)2·12H2O, AASD) based novel CPCMs for thermal energy storage. A melting/solidification experiment with 2 modes and a comprehensive evaluation method were established to analyze the influence of various additives and thermal cycles on the heat storage/release performance of AASD based CPCMs. Thermal properties, chemical compatibility, thermal reliability and stability of the CPCMs with relatively low undercooling were further investigated. It was shown that the optimum formulations of the CPCMs were 97 wt% AASD/2 wt% XG/1 wt% APSD and 97 wt% AASD/2 wt% XG/1 wt% CCD (novel CPCMs). The adverse effect of 2 wt% XG on the heat storage efficiency of CPCMs could be eliminated spontaneously during the process of thermal cycles. The suitable melting temperature (MSE mode 1: 92.1–93.5 °C; MSE mode 2: 92.3–93.1 °C)/crystallization temperature (MSE mode 1: 60.2–80.5 °C; MSE mode 2: 59.0–77.3 °C) and high latent heat (187.2–255.5 J/g, 210 thermal cycles) enable the novel CPCMs with simple preparation method to be up-and-coming candidates for thermal energy storage.

Experimental research on an environment-friendly form-stable phase change material incorporating modified rice husk ash for thermal energy storage

Abstract In this paper, a novel environment-friendly form-stable phase change material (PCM) was prepared by use of a mechanical mixing and the impregnation method for thermal energy storage. An agricultural solid waste rice husk ash (RHA) was acted as supporting material due to its natural high porosity and surface area, as well as organic paraffin (PA) was selected as core material used for heat storage. Particularly, acid-treated RHA with higher loading capacity compared to rough RHA was used as a support to stabilize PA. X-ray fluorescence method (XRF) and nitrogen adsorption analysis (N2 adsorption) indicated that the impurities within RHA was effectively removed, the pore volume and specific surface area were increased by 37.3% and 54.2% after acid treatment. The leakage test exhibited that the prepared PA/RHA containing 50 wt% PA can maintain solid shape without leakage in melting state of organic PA. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy (ATR-FTIR) results suggested that there was no chemical reaction occurred between PA and RHA with the superior combination. Differential scanning calorimetry (DSC) was used to record the phase change properties of PA/RHA with the phase change temperature of 51.5 °C and latent heat of 68.1 J/g. Moreover, the prepared composite PCM maintained favorable thermal cycling reliability, being subjected to 200 thermal cycles. Furthermore, Thermal gravimetric analysis (TGA) illustrated a beneficial effect of RHA on the thermal stability of PA. Therefore, the prepared composite PCM can be regarded as a potential environment-friendly candidate for thermal energy storage in building energy efficiency.

Synthesis and Nanoencapsulation of Poly(ethylene glycol)-Distearates Phase Change Materials for Latent Heat Storage and Release

Phase change materials (PCMs) are essential candidates for thermal energy storage and management. In this work, a library of PCMs with a wide range of phase transition temperatures and latent heat ...

Numerical investigation of the effects of heating and contact conditions on the thermal charging performance of composite phase change material

Abstract Phase change material (PCM) saturated in metal foam is a promising candidate for thermal energy storage (TES). However, there are some potential factors affecting the thermal charging performance of composite PCM, such as heating and contact conditions. In this paper, paraffin and copper foam are selected as PCM and metal matrix, respectively. Heating conditions are top, left and bottom heating. The contact gaps are set to 0, 0.4 and 0.8 mm to represent different contact conditions. The numerical investigation on thermal charging performance of composite PCM under different heating and contact conditions is performed. Based on volume-averaged method, the numerical model is developed to study the thermal characteristics of composite PCM including solid-liquid interface, liquid fraction, velocity, total melting time and average heat storage rate. Results show that there are the comprehensive effects of heating and contact conditions on thermal performance. The heating condition can affect phase change heat transfer mode, and thus has a significant influence on thermal charging performance. The contact conditions have the different effects on thermal behavior of composite under different heating conditions, e.g., under top heating condition, the total melting time of composite with 0 mm and 0.8 mm contact gaps is almost the same. Whereas, under left heating condition, the total melting time of composite with 0.8 mm contact gap is 2.6 times that of composite with 0 mm contact gap. The study of the effect mechanism of heating and contact conditions is of great significance for practical application of composite PCM in TES system.

Thermally Conductive and Shape‐Stabilized Polyethylene Glycol/Carbon Foam Phase‐Change Composites for Thermal Energy Storage

AbstractPhase‐change materials (PCMs) have been widely investigated as candidates for thermal energy storage and solar thermal energy conversion. However, low thermal conductivity and poor shape stability during phase transition processes are detrimental to their practical applications. In this study, we designed composite PCMs based on carbon foam (CF) via the vacuum impregnation method to overcome these problems. CF with 3D interconnected microporous structures and good compressive strength was fabricated from phenolic resin (PF) using a combined process of carbonization and sacrificial template techniques. The developer material is considered a promising support material for PCMs. The as‐prepared polyethylene glycol/CF composite (PCC) exhibited a high energy‐storage density with a melting enthalpy of 135.7 J/g, and the thermal conductivity was enhanced by 109.8% compared to that of pure polyethylene glycol. In addition, the PCC showed excellent thermal stability and leakage‐proof performance after 100 heating/cooling cycles and good compressive strength. Because of the simple preparation process and low cost, PCC is a promising material for various thermal energy storage applications, especially in building energy storage systems.

Synthesis and Characterization of the Paraffin/Expanded Perlite Loaded With Graphene Nanoparticles as a Thermal Energy Storage Material in Buildings

Abstract Various properties of the paraffin have made them compatible to be incorporated in the building materials for improving the latent heat storage capacity of the building envelope. However, the poor thermal conductivity of the paraffin reduces their thermal performance and hence limits their direct application/incorporation in the buildings. In this study, composite mixtures of paraffin and expanded perlite (EP) with an equal weight percent of 49.5 and 47.5, loaded with 1% and 5% of graphene nano-platelets, respectively, were synthesized. The developed samples were characterized uncycled and after 2000 thermal cycles. The results indicate that phase change material (PCM)/expanded perlite/graphene nano-platelets composite shows a significant increment in the thermal conductivity, reduction in the latent heat storage capacity, and a small weight loss. The heat storage/release test depicts that the phase change material/expanded perlite/graphene nano-platelets-5 shows 1.66 and 2.5 times faster heat storage/release rate than phase change material/expanded perlite/graphene nano-platelets-1 and paraffin, respectively. There is no significant change noted after 2000 thermal cycles in phase change material/expanded perlite/graphene nano-platelets-5 and phase change material/expanded perlite/graphene nano-platelets-1 samples, suggesting long-term reliability of the composite PCM. Additionally, thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR) testing were also conducted and the results suggest high thermal reliability and good chemical compatibility. These analyses suggest that the phase change material/expanded perlite/graphene nano-platelets composite can become a potential candidate for thermal energy storage.