Thermal characterization of phase change materials based on linear low-density polyethylene,paraffin wax and expanded graphite

Thermal characterization of Phase Change Materials (PCMs) based on linear low-density polyethylene (LLDPE), paraffin wax (W) and expanded graphite (EG) is reported in this paper. Investigated PCMs showed high potential for application in energy storage systems.The latent heat, L_m, sensible heat Q_sens, and the ability of the prepared PCMs to store and release thermal energy were investigated using specific home-made equipment based on the transient guarded hot plane method (TGHPT). The sensible heat of PCM containing 40 wt.% of paraffin wax was investigated in the temperature range 25–35 °C, they exhibited a drop in Q_sens from 31 to 24 J/g depending on the concentration of EG. A similar decrease in sensible heat with increased loading of EG was observed for PCMs containing 50 wt.% of EG.The storage and release of thermal energy during phase change which is associated with the latent heat of the materials were investigated within the temperature range 20–50 °C. PCMs containing 40 wt.% of paraffin wax exhibited latent heat of 36 J/g, whereas the latent heat of PCMs containing 50 wt.% of paraffin wax was 49 J/g. The addition of EG decreased the time needed to melt and solidify PCMs due to increase in thermal conductivity of PCMs with increase in EG content. This behavior was confirmed by the thermal conductivity measurements, where thermal conductivity increased from 0.252 for sample without EG to 1.329 W/m × °C for PCM containing 15 wt.% of EG.The reproducibility of storage and release of thermal energy by PCMs was demonstrated by subjecting them to repeated heating and cooling cycles (over 150 cycles).     

Thermal conductivity and latent heat thermal energy storage characteristics of paraffin/expanded graphite composite as phase change material

This study aimed determination of proper amount of paraffin (n-docosane) absorbed into expanded graphite (EG) to obtain form-stable composite as phase change material (PCM), examination of the influence of EG addition on the thermal conductivity using transient hot-wire method and investigation of latent heat thermal energy storage (LHTES) characteristics of paraffin such as melting time, melting temperature and latent heat capacity using differential scanning calorimetry (DSC) technique. The paraffin/EG composites with the mass fraction of 2%, 4%, 7%, and 10% EG were prepared by absorbing liquid paraffin into the EG. The composite PCM with mass fraction of 10% EG was considered as form-stable allowing no leakage of melted paraffin during the solid–liquid phase change due to capillary and surface tension forces of EG. Thermal conductivity of the pure paraffin and the composite PCMs including 2, 4, 7 and 10 wt% EG were measured as 0.22, 0.40, 0.52, 0.68 and 0.82 W/m K, respectively. Melting time test showed that the increasing thermal conductivity of paraffin noticeably decreased its melting time. Furthermore, DSC analysis indicated that changes in the melting temperatures of the composite PCMs were not considerable, and their latent heat capacities were approximately equivalent to the values calculated based on the mass ratios of the paraffin in the composites. It was concluded that the composite PCM with the mass fraction of 10% EG was the most promising one for LHTES applications due to its form-stable property, direct usability without a need of extra storage container, high thermal conductivity, good melting temperature and satisfying latent heat storage capacity.     

Thermal conductivity improvement of stearic acid using expanded graphite and carbon fiber for energy storage applications

The influence of expanded graphite (EG) and carbon fiber (CF) as heat diffusion promoters on thermal conductivity improvement of stearic acid (SA), as a phase change material (PCM), was evaluated. EG and CF in different mass fractions (2%, 4%, 7%, and 10%) were added to SA, and thermal conductivities of SA/EG and SA/CF composites were measured by using hot-wire method. An almost linear relationship between mass fractions of EG and CF additives, and thermal conductivity of SA was found. Thermal conductivity of SA (0.30 W/mK) increased by 266.6% (206.6%) by adding 10% mass fraction EG (CF). The improvement in thermal conductivity of SA was also experimentally tested by comparing melting time of the pure SA with that of SA/EG and SA/CF composites. The results indicated that the melting times of composite PCMs were reduced significantly with respect to that of pure SA. Furthermore, the latent heat capacities of the SA/EG and SA/CF (90/10 wt%) composite PCMs were determined by differential scanning calorimetry (DSC) technique and compared with that of pure SA. On the basis of all results, it was concluded that the use of EG and CF can be considered an effective method to improve thermal conductivity of SA without reducing much its latent heat storage capacity.     

Development and energy evaluation of phase change material composite for building energy‐saving

Phase change materials (PCMs) contributed to building energy‐saving and thermal comfort through increasing the thermal capacity of building envelopes. In this study, a phase change material composite was developed by using the PCMs mixture of capric acid (CA) and lauric acid (LA) as the primary phase change energy storage agent and using the solid waste fly ash as a carrier material. The results showed that for Guangdong, the ideal PCMs mixture should have a transition temperature of 25.5^oC, which could be obtained by using a mass ratio of CA/LA of 4:6. Then, experiment results also indicate that the optimum adsorption ratio of 2:1 (FA/PCMs) was detected for the synthesis of this FA/PCMs composite, which has the latent heat of 45.38 J/g and exists excellent thermal reliability. Moreover, simulation results by using EnergyPlus show that the proposed composite has a good building energy‐saving effect.     

Composite phase change material based on reduced graphene oxide/expanded graphite aerogel with improved thermal properties and shape-stability

Composite phase change materials (PCMs) based on reduced graphene oxide/expanded graphite (rGO/EG) aerogel were prepared by hydrothermal self-assembly and impregnation method. The morphology, chemical structure, thermal properties, and shape-stability of the composite PCMs based on rGO/EG aerogel were examined. The results show that rGO sheets form a three-dimensional (3D) network structure and EG particles are attached to rGO sheets and uniformly interspersed in the aerogel. The oxygen-containing functional groups remaining in rGO/EG aerogel promote heterogeneous crystallization of paraffin, leading to increased latent heat. The 3D thermally conductive pathway provided by rGO/EG aerogel improves the composite PCM's thermal conductivity up to 0.79 W·m⁻¹·K⁻¹, which is about 4 times of that of pure paraffin. The leakage of composite PCMs is remarkably improved at very high percentage of paraffin. Simulative light-thermal experiments reveal that the composite PCMs have the ability of conversion and storage of light-thermal energy. In short, 3D network structure of rGO, with the aid of EG, endows the composite PCMs with improved thermal properties, good shape-stability, and light-thermal storage performance.     

Preparation and characterization of urea/ammonia bromide composite phase change material

In order to find phase change materials that can be better applied in the field of solar collectors, the phase change heat storage properties of urea (U) and ammonium bromide (AB) were studied. The eutectic ratio of UAB was found by the Edison method, and different additives were added to UAB by dipping and mixing. The structure and property of the composites were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), differential scanning calorimetry (DSC), and TG/TGA, respectively. The results showed that the eutectic ratio of UAB was 6:3; it was weakly acidic after melting not layered. When 6-wt% EG and 1-wt% nanometer titanium dioxide (TiO₂) were added, the thermal conductivity of the material increased by 3.62 times; the thermal diffusivity was increased by 6.77 times. When the mass fraction of EG is between 1% and 6%, the larger the mass fraction of EG, the greater the thermal conductivity of the material. After 1000 cycles, the composite material performance was stable; at the same time, the used materials can be used as fertilizers to solve the problem of material pollution, which indicated that the prepared UAB/TiO2/EG composite PCMs had great application prospect in the field of solar collectors.     

Solar-thermal energy conversion and storage of super black carbon reinforced melamine foam aerogel for shape-stable phase change composites

Thermal energy harvesting and storage with phase change materials (PCMs) have attracted extensive exploration in solar-thermal utilization. Solving leakage issue of PCMs and improving the energy absorption, storage and transport are facing great challenges. As a typical aerogel with porous structure and strong light absorption, carbon aerogel (CA) becomes an attractive support material for PCMs. In this work, the carbon aerogels reinforced melamine foam (CA/Foam) were prepared by sol-gel polymerization, freeze drying and carbonization. To further optimize the pore structure and optical properties, CO₂ activation is implemented to obtain the super black reinforced melamine foam, which is named as activated CA/Foam (ACA/Foam). After vacuum adsorption of PW, the prepared paraffin wax/activated carbon aerogel/foam (PW/ACA/Foam) maintains high thermal storage density of 143.4 J/g and shows excellent thermal stability, which can effectively solve the shortcoming of PCMs leakage due to rich pore structure. Encouragingly, the photothermal conversion efficiency of PW/ACA/Foam composite material can reach 92.1% with 5% weight fraction of resorcinol and formaldehyde in the precursor solution. The thermal conductivity of PW/ACA/Foam is 0.71 W/(m·K), 97.2% higher than pure PW, which will be the potential material for composite PCMs applied in solar energy utilization.     

Structure and thermal properties of expanded graphite/paraffin composite phase change material

Different contents of expanded graphite (EG) composite phase change material (PCM) were prepared by the melt mixing method, taking paraffin as the PCM and EG as the supporting material. Phase compositions of EG, paraffin, and EG/paraffin composite were investigated using X-ray diffraction (XRD). Microstructures of EG and EG/paraffin composite PCMs with different EG contents were observed by a scanning electron microscope (SEM). Thermal properties, such as phase-transition temperature and latent heat of the materials, were determined by differential scanning calorimetry (DSC). Mass loss and thermal properties after 100 heating cycles were measured. The results show that physical absorption exists between paraffin and EG. EG is beneficial for the PCM composite to reduce leakage of paraffin, decrease the phase change temperature and latent heat, and strengthen the thermal stability. The solid–liquid phase change latent heat of materials is larger than that of the solid–solid one. The heating cycle has little effect on the phase-transition temperature and latent heat.     

Preparation and properties of caprylic‐nonanoic acid mixture/expanded graphite composite as phase change material for thermal energy storage

To satisfy the application demands for latent heat storage in the temperature range from 5°C to 15°C, an original composite phase change material (PCM), CA‐NA/EG (caprylic‐nonanoic acid/expanded graphite), was prepared and characterized. For CA‐NA/EG, the mass ratio of CA and NA was 8:2, and the mass percentage of the CA‐NA in CA‐NA/EG composite PCM was determined as 90% by leakage test. The melting and freezing points of the CA‐NA/EG were 6.84°C and 9.34°C, and corresponding latent heats were 108.75 kJ/kg and 107.67 kJ/kg. In addition, its thermal conductivity, thermal stability and reliability were investigated by thermal conductivity apparatus (TCA), thermal gravimetric analyzer (TGA), and accelerated thermal cycle test for 100 melt/freeze cycles, respectively. The results showed that the CA‐NA/EG had a good thermal stability and an excellent thermal reliability. Moreover, the thermal conductivity of CA‐NA/EG had an improvement of 25% than that of the CA‐NA. On the other hand, the accelerated thermal cycle test also indicated that the CA‐NA/EG had no supercooling during all melt/freeze cycles. Therefore, the prepared composite PCM, CA‐NA/EG, can be applied for low‐temperature thermal energy storage owing to its proper melting temperature, acceptable latent heat and thermal conductivity, excellent thermal stability and reliability.     

Fabrication and characterization of electrospun fatty acid form-stable phase change materials in the presence of copper nanoparticles

Latent heat storage system using phase change materials (PCMs) has been recognized as one of the most useful technologies for energy conservation. In this study, a novel type of fatty acid eutectic of methyl palmitate (MP) and lauric acid (LA)/polyacrylonitrile (PAN) composite phase change fiber is prepared by single electrospinning method. Additionally, copper nanoparticles (CNPs) with different mass ratio are combined for improving the thermal conductivity of the PCM. The structure and morphology of the fabricated composite PCMs are observed by scanning electron microscopy (SEM), and the thermal properties and performance are also characterized. SEM results show that the liquid fatty acid has been fully stabled by the three-dimensional structure of the fibers. Good compatibility among the components of the composites is also demonstrated. Besides, the addition of nanoparticles leads to an improved thermal conductivity by over 115.2% and a phase transition temperature 21.24 °C as well as a high latent heat of 85.07 J/g. Moreover, excellent thermal reliability of the phase change fiber is confirmed by multiple thermal cycles. Hence, the composite PCM prepared in this study shows a promising potential for thermal energy system such as building insulating and thermal mass regulating textiles.     

Preparation, thermal properties and thermal reliability of palmitic acid/expanded graphite composite as form-stable PCM for thermal energy storage

This study is focused on the preparation and characterization of thermal properties and thermal reliability of palmitic acid (PA)/expanded graphite (EG) composite as form-stable phase change material (PCM). The maximum mass fraction of PA retained in EG was found as 80 wt% without the leakage of PA in melted state even when it is heated over the melting point of PA. Therefore, the PA/EG (80/20 w/w%) composite was characterized as form-stable PCM. From differential scanning calorimetry (DSC) analysis, the melting and freezing temperatures and latent heats of the form-stable PCM were measured as 60.88 and 60.81 °C and 148.36 and 149.66 J/g, respectively. Thermal cycling test showed that the composite PCM has good thermal reliability although it was subjected to 3000 melting/freezing cycles. Fourier transformation infrared (FT-IR) spectroscopic investigation indicated that it has good chemical stability after thermal cycling. Thermal conductivities of PA/EG composites including different mass fractions of EG (5%, 10%, 15% and 20%) were also measured. Thermal conductivity of form-stable PA/EG (80/20 w/w%) composite (0.60 W/mK) was found to be 2.5 times higher than that of pure PA (0.17 W/mK). Moreover, the increase in thermal conductivity of PA was confirmed by comparison of the melting and freezing times of pure PA with that of form-stable composite. Based on all results, it was concluded that the form-stable PA/EG (80/20 w/w%) has considerable latent heat energy storage potential because of its good thermal properties, thermal and chemical reliability and thermal conductivity.     

Thermal property measurement and heat transfer analysis of acetamide and acetamide/expanded graphite composite phase change material for solar heat storage

As a phase change material (PCM), acetamide (AC) can be a potential candidate for energy storage application in the active solar systems. Its utilization is however hampered by poor thermal conductivity. In this work, AC/expanded graphite (EG) composite PCM with 10 wt% (mass fraction) EG as the effective heat transfer promoter was prepared; its thermal properties were studied and compared with those of pure AC. Transient hot-wire tests showed that the addition of 10 wt% EG led to about five-fold increase in thermal conductivity. Investigations using a differential scanning calorimeter revealed that the melting/freezing points shifted from 66.95/42.46 °C for pure AC to 65.91/65.52 °C for AC/EG composite, and the latent heat decreased from 194.92 to 163.71 kJ kg⁻¹. In addition, heat storage and retrieval tests in a latent thermal energy storage unit showed that the heat storage and retrieval durations were reduced by 45% and 78%, respectively. Further numerical investigations demonstrated that the less improvement in heat transfer rate during the storage process could be attributed to the weakened natural convection in liquid (melted) AC because of the presence of EG.     

Influences of expanded graphite on structural morphology and thermal performance of composite phase change materials consisting of fatty acid eutectics and electrospun PA6 nanofibrous mats

In the present work, three fatty acid eutectics of capric acid (CA)–lauric acid (LA), capric acid–palmitic acid (PA), and capric acid–stearic acid (SA) were prepared through melt-blending followed by ultrasonication and were investigated as model phase change materials (PCMs); for comparison, the individual fatty acid of CA was also studied. The DSC measurements indicated that the phase transition temperatures of fatty acid eutectics were lower than those of individual fatty acid of CA. Thereafter, the polyamide 6 (PA6) nanofibers and PA6/EG composite nanofibers with 10 wt.% expanded graphite (EG) were prepared by electrospinning; and then composite PCMs with fatty acid eutectics absorbed in and/or supported by the overlaid mats of electrospun nanofibers (e.g., PA6 and PA6/EG) were explored for storage and retrieval of thermal energy. Influences of the EG on structural morphologies, thermal energy storage properties and thermal energy storage/retrieval rates of composite PCMs were respectively characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and measurement of melting/freezing times. The results indicated that the additions of EG caused the interfaces between fatty acid eutectics and PA6 nanofibrous mats to become more illegible; increased the absorption capacity of fatty acid eutectics within nanofibrous mats. The enthalpies of melting and crystallization of composite PCMs with EG were higher than those of the corresponding composite PCMs without EG, whereas there were no appreciable changes on the phase transition temperatures. The EG improved thermal energy storage/retrieval rates of composite PCMs were also confirmed by comparing the melting/freezing times of CA/PA6/EG and CA–SA/PA6/EG with those of CA/PA6 and CA–SA/PA6, respectively. The results from the SEM observation showed that composite PCMs had no or little variations in shape and surface morphology after heating/cooling processes.     

Experimental Investigation on Heat Storage/Retrieval Characteristics of a Latent Heat Storage System

The charging and discharging characteristics of a latent thermal energy storage (LTES) system were experimentally studied. Pure paraffin and paraffin/expanded graphite (EG) composite containing 7% and 10% mass fraction of EG were used as the phase-change materials (PCMs). Various experiments were conducted with different heat transfer fluid (HTF) temperatures and flow rates for heat storage and retrieval, respectively. The time durations of the charging and discharging processes, the mean power, and the energy efficiency of the system, which are the important factors of the LTES system, were discussed. The results showed that natural convection played a crucial role in the heat transfer during the charging process of paraffin, but heat conduction was the main heat transfer mechanism during the discharging process of paraffin. The higher the flow rate was, the higher the charging and discharging rate would be. Large temperature difference between the HTF and the initial state of PCM would accelerate the charging and discharging processes. During the charging process, the large temperature difference would result in the accelerated phase-change process due to the enhanced natural convection that could be seen clearly when the PCM was paraffin. While no significant difference was found for different initial temperatures during the discharging process. The performance of the LTES was affected prominently by the PCMs, HTF temperatures, and flow rates. The energy efficiency was higher for the 10 wt% EG PCMs, and the mean power during the discharging process was larger accordingly.     

Numerical study on solar-driven methanol steam reforming reactor with multiple phase change materials

The multi-stage phase change material (PCM) fillings were proposed in the methanol steam reforming tube reactor driven by the parabolic-trough concentrated solar energy. Two-dimensional mathematical model of such surround filling reactor with numerical simulation was developed to evaluate its performance on eliminating the solar energy fluctuation. The effects of PCM with different thermophysical properties on chemical performance of the reactor were conducted when the sun is blocked. The optimal arrangement of multiple-stage PCMs was investigated and its performance under solar radiation fluctuations was investigated to improve the available latent heat of PCM and chemical performance of the reactor. The results showed that the PCM filling in the reactor significantly increased the time of methanol reforming reaction and improved the chemical performance when the heating by concentrated solar energy was ceased. PCM with lower phase change temperature and more latent heat could maintain the chemical reaction for a longer time. However, better chemical performance when PCM released latent heat could be achieved by PCM with higher phase change temperature. Compared to single PCM filling, Two-stage PCMs reached a maximum relative improvement in methanol conversion of 10.86%. Three-stage PCMs reached the maximum relative enhancement in methanol conversion of 11.36% compared to Two-stage PCMs. Under the cyclic and solar fluctuations, the multiple-stage PCMs reactor produced nearly twice as much hydrogen as that of the reactor without PCM. During a 6-h real solar radiation fluctuation, the multiple-stage PCMs reactor also have better methanol conversion. However, more than Three-stage PCMs arrangement improved the chemical performance of reactor only slightly.     

Synthesis and Characterization of Disodium Hydrogen Phosphate Dodecahydrate-Lauric-Palmitic Acid Used for Indoor Energy Storage Floor Units

Organic and inorganic phase change materials(PCMs) are considered potential materials for thermal energy storage(TES) with different phase change characteristics. In this study, a novel organic-inorganic composite phase change material(PCM) called disodium hydrogen phosphate dodecahydrate-lauric-palmitic acid(D-LA-PACM) was prepared. Expanded graphite(EG) was selected as the support material, and the novel organic-inorganic form-stable PCM called D-LA-PAPCM/EG was prepared using the vacuum adsorption method. Differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, leakage testing, melting and solidification cycle testing, thermal conductivity testing, scanning electron microscopy observation of the micromorphology, and other characterization methods were used to study the microstructure and morphology, thermal physical parameters, thermal conductivity, stability of the PCMs, and the comprehensive material properties of D-LA-PAPCM under the composite action of EG. Results indicated that the melting and freezing temperatures and latent heats of D-LA-PAPCM/EG were measured to be 31.6℃ and 34.3℃ and 142.9 and 142.8 J/g, respectively. Although some of the lauric-palmitic acid(LA-PA) and disodium hydrogen phosphate dodecahydrate(DHPD) separated in the multiple porous structures of EG after 1000 cycles, they could still absorb and release latent heats independently, with D-LA-PAPCM/EG still exhibiting good thermal stability. The thermal conductivity of D-LA-PAPCM/EG was 1.361 W/(m·K). Therefore, the material and thermal properties of the prepared D-LA-PAPCM/EG indicate that it could be well used as a feasible material for energy-saving phase change floor units in indoor TES systems.     

Fatty acid/poly(methyl methacrylate) (PMMA) blends as form-stable phase change materials for latent heat thermal energy storage

Fatty acids such as stearic acid (SA), palmitic acid (PA), myristic acid (MA), and lauric acid (LA) are promising phase change materials (PCMs) for latent heat thermal energy storage (LHTES) applications, but high cost is the most drawback which limits the utility area of them in thermal energy storage. The use of fatty acids as form-stable PCM will increase their feasibilities in practical LHTES applications due to reduced cost of the energy storage system. In this regard, a series of fatty acid/poly(methyl methacrylate) (PMMA) blends, SA/PMMA, PA/PMMA, MA/PMMA, and LA/PMMA were prepared as new kinds of form-stable PCMs by encapsulation of fatty acids into PMMA which acts as supporting material. The blends were prepared at different mass fractions of fatty acids (50, 60, 70, 80, and 90% w/w) to reach maximum encapsulation ratio. All blends were subjected to leakage test by heating the blends over the melting temperature of the PCM. The blends that do not allow leakage of melted PCM were identified as form-stable PCMs. The form-stable fatty acid/PMMA (80/20 wt.%) blends were characterized using optic microscopy (OM), viscosimetry, and Fourier transform infrared (FT-IR) spectroscopy methods, and the results showed that the PMMA was compatible with the fatty acids. In addition, thermal characteristics such as melting and freezing temperatures and latent heats of the form-stable PCMs were measured by using differential scanning calorimetry (DSC) technique and indicated that they had good thermal properties. On the basis of all results, it was concluded that form-stable fatty acid/PMMA blends had important potential for some practical LHTES applications such as under floor space heating of buildings and passive solar space heating of buildings by using wallboard, plasterboard or floor impregnated with a form-stable PCM due to their satisfying thermal properties, easily preparing in desired dimensions, direct usability without needing an add encapsulation and eliminating the thermal resistance caused by shell and thus reducing cost of LHTES system.     

组合式相变材料组分配比与储热性能研究

采用焓法对组合式相变材料(PCM)储热系统的相变过程进行了数值计算,分析了组合式相变材料中各个PCM组分质量分数的变化对系统储热性能的影响。结果表明,对于组合式相变材料储热系统,存在着最优组分配比,使得系统的储热性能达到最佳。     

Morphology and thermal properties of electrospun fatty acids/polyethylene terephthalate composite fibers as novel form-stable phase change materials

The ultrafine fibers based on the composites of polyethylene terephthalate (PET) and a series of fatty acids, lauric acid (LA), myristic acid (MA), palmitic acid (PA), and stearic acid (SA), were prepared successfully via electrospinning as form-stable phase change materials (PCMs). The morphology and thermal properties of the composite fibers were studied by field emission scanning electron microscopy (FE-SEM) and differential scanning calorimetry (DSC), respectively. It was found that the average fiber diameter increased generally with the content of fatty acid (LA) in the LA/PET composite fibers. The fibers with the low mass ratio maintained cylindrical shape with smooth surface while the quality became worse when the mass ratio is too high (more than 100/100). Moreover, the latent heat of the composite fibers increased with the increase of LA content and the phase transition temperature of the fibers have no obvious variations compared with LA. In contrast, both the latent heat and phase transition temperature of the fatty acid/PET composite fibers varied with the type of the fatty acids, and could be well maintained after 100 heating-cooling thermal cycles, which demonstrated that the composite fibers had good thermal stability and reliability.     

Hydrophilic expanded graphite–magnesium nitrate hexahydrate composite phase change materials: Understanding the effect of hydrophilic modification on thermophysical properties

Expanded graphite (EG) has shown excellent performances in compression resilience, thermal conductivity, and adsorption ability. EG can adsorb liquid phase change materials (PCMs) mainly because of capillary action; however, EG is hydrophobic, which makes it less compatible with hydrated salts. Herein, hydrophilic EG (HEG) was prepared with Triton X‐100 (TX‐100) as surface modifier. The HEG–magnesium nitrate hexahydrate (HEG‐MNH) composite as a PCM was investigated for thermal energy storage (TES) to understand the effect of hydrophilic modification on thermophysical properties. The powder‐state HEG is added into MNH to prepare HEG‐MNH composite PCM, which contains 1.71 wt% of TX‐100, 7.29 wt% of EG, and 91.00 wt% of MNH by control variable method. The melting point and latent heat of HEG‐MNH composite PCM were 89.05°C and 137.28 J/g, respectively. The endothermic enthalpy change of HEG‐MNH composite PCM only decreased by 0.90%, along with the exothermic values of HEG‐MNH composite that increased by 3.80% after 100 cycles. The thermal conductivity is higher 5.17 times than that of the pure MNH. Our work suggests that the HEG‐MNH composite PCM has a great potential to be used as a PCM for TES.