Shape-stabilized Phase Change Materials Research Articles

A critical review of polymer support‐based shape‐stabilized phase change materials for thermal energy storage applications

AbstractPhase change materials (PCMs) have drawn considerable attention in recent years due to their capability of storing and releasing thermal energy during phase transformation. However, traditional PCMs face challenges like limited thermal conductivity, leakage while phase transformation from solid to liquid, thermal degradation, and durability. Researchers have concentrated on creating shape‐stabilized PCMs (SSPCMs) employing polymers as the supporting matrix to overcome these difficulties and incorporating highly thermally conductive additives to improve thermal conductivity. Compared to conventional PCMs, polymer‐based SSPCMs are often more flexible, lightweight, and durable and may be easily customized according to specific applications. Various factors like PCM loading, thermal cyclability, cost‐effectiveness and environmental concerns must be considered while constructing polymer‐based SSPCMs. This review paper comprehensively explored various polymers, including polyurethane, polyacrylates, polyolefin, and so on, as promising supporting materials for SSPCMs due to their relatively high mechanical strength, compatibility with PCM, excellent thermal stability, and chemical resistance. Natural polymers like chitosan, cellulose, and starch are also considered for eco‐friendly solutions. We have also discussed about specific properties of each polymer, their cost‐effectiveness, and the environmental impact while developing such SSPCMs to guide researchers in material selection. Applications of polymer‐based SSPCMs in solar energy storage, medical devices, building materials, electronics, transportation industry, and waste heat recovery are briefly discussed. Finally, some future development areas have been discussed to attract the attention of new researchers in this field. The information provided in this review will assist readers in understanding polymer‐based SSPCM and selecting their desired polymer for support material with diverse application methods.

Harnessing leather waste in polymer matrix for sustainable smart shape‐stable phase change materials

AbstractThe utilization of leather waste (LW) in a polyurethane (PU) matrix makes a smart and novel shape stable phase change material (SSPCM). This is essential for sustainability as it reduces landfill waste after use. The PU is synthesized in bulk with a 90% yield, using biodegradable polycaprolactone diol and bio‐based polyol (castor oil), along with tolylene‐2,4‐diisocyanate. PL and PLG composites are prepared by blending of constituent components PU (P), LW (L), and poly(glycidyl methacrylate) (PGMA, G), as specified by their code names. Role of LW (hydrogen bonding and chemical crosslinking) and morphology are elucidated by FTIR and SEM, respectively. Self‐healing time (2 h), shape fixity ratios (Rf) (PL: 60–80% and PLG: 60–70%) and shape recovery ratios (Rr) (100% for both) are determined at 60°C. PLG displays faster shape recovery in water (<30 s) compared to air (>300 s). Shape stability and thermal properties of the SSPCM are examined using the temperature responsive leakage study, TGA, and DSC. This research introduces a new approach for using leather waste (LW) in SSPCM, with self‐healing and 100% Rr. This material may find application where SSPCM with high durability and flexibility is essential such as textile and footwear materials.

Development of a cooling system for marine power batteries

For green shipping, lithium-ion battery-powered ships are rapidly developing. Compared with power batteries for electric vehicles, the large volume and capacity of cells in electric ships make it difficult to dissipate heat, thus requiring efficient cooling. Herein, a novel shape-stabilized phase change material (SSPCM) channel/thermoelectric cooler (TEC) cooling system for marine power batteries was proposed and experimentally studied. It uses TEC for localized cooling and seawater flowing inside the SSPCM as coolant. First, the arrangement of the TECs was experimentally determined. Then, the cooling performance of the system was verified by comparative experiments. The results show that, compared to the cooling system without TECs, the maximum temperature difference was reduced by 28.8 %, with the maximum temperature and temperature difference of 49.8 °C and 3.7 °C, respectively. Compared with the single cooling method, the maximum temperature and temperature difference were reduced by 15.5 % and 53.3 %, respectively. Finally, the experiments were conducted to explore the impact of various parameters on the cooling performance of the system. The unique combination of SSPCM channel, seawater, and TEC provides a new strategy for efficiently cooling marine power batteries at high charge/discharge rates.

Development of CaCl2·6H2O-mannitol/SiO2 shape-stabilized composite phase change material for the radiant cooling panel system

Radiant cooling panel systems are now popular solution for low carbon buildings, so has received great attention of researchers. Current development, however, is that radiant cooling panel systems have low cooling efficiency and cause high pressure on national energy supply during peak energy consumption periods. This study, therefore, has developed a novel composite phase change material (CPCM) coupled with a typical radiant cooling panel system, providing longer indoor comfort duration and less temperature fluctuation, while also alleviating the pressure on national energy supply during peak energy consumption. In this study, eutectic hydration salt of CaCl2·6H2O and mannitol have been combined with SiO2 to prepare a shape-stabilized CPCM. It has been placed in a test room to justify the impact of the new material. Experimental results have demonstrated some major properties of this material, namely, a melting point of 20.7 °C, a high latent heat value of 119.8 J/g, and a supercooling degree of 1.3 °C, as well as good stability and thermal reliability. Therefore, it can be used as a good solution for radiant cooling panel systems. Comparing the results with another test room with ordinary radiant cooling panels, the room with the new CPCM panel showed less indoor temperature fluctuation and 73 % longer indoor comfort duration. This work provides further development of using hydrated salts and CPCMs with different phase change temperatures in radiant cooling panel systems.

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.

Molten Bismuth–Bismuth/Zinc Oxide Composites for High-Temperature Thermal Energy Storage

Thermal energy storage is at the leading edge of various applications, including waste heat recovery, solar storage and zero-energy buildings. Phase change materials (PCMs) can be utilized to store heat through reversible solid–liquid phase transitions. PCMs provide high energy storage capacity at a constant temperature. The volume change during the phase transition, on the other hand, causes inconsistency in crystallization and leakage, increasing the system’s complexity and shortening the lifetime of these materials. These shortcomings can be diminished by impregnation in a porous matrix or encapsulation with an inert shell, resulting in shape-stabilized PCMs that maintain their macroscopic shape during phase change. The synthesis and properties of Bi/ZnO nanocomposites were investigated in order to obtain shape-stabilized phase change materials. All samples consisted of metallic Bi and oxide, doped with 1–3% at. zinc. Heat storage capacities between 31 and 49 Jg−1 were obtained, depending on the mass fraction of the metal. All samples had good thermal reliability, retaining their heat storage properties after 50 consecutive heating–cooling cycles. An average oxide layer thickness of 75–100 nm is sufficient to prevent the molten metal leakage at temperatures above its melting point, resulting in shape-stabilized PCMs.

Shape-stable phase change materials based on carboxymethyl chitosan/boron nitride nanosheets high-strength aerogel

The application of phase change materials (PCMs) in energy storage and temperature control systems holds significant promise for enhancing energy efficiency and environmental sustainability. Herein, the development of a boron nitride nano-aerogel-supported PCM, reinforced by carboxymethyl chitosan (CMCS) and oxidized corn starch (DCS) cross-linking was reported. This approach involved the utilization of polydopamine-modified boron nitride nanosheets (PDA@BNNS) for the fabrication of a thermally conductive skeleton, while carboxymethyl chitosan (CMCS) and oxidized corn starch (DCS) were utilized as reinforcing material and cross-linking agent, respectively. The skeleton was prepared via a sol-gel method and freeze-drying technique, while polyethylene glycol (PEG) was subsequently encapsulated using a vacuum impregnation method. Notably, the prepared skeleton exhibits a compressive stress of 12.18 MPa at 80 % strain, much higher than other boron nitride nanosheets aerogels reported in literature. The cross-linked boron nitride skeleton enhances the thermal conductivity of the composites by 137.4 % compared to pure PEG. Furthermore, due to the highly porous structure of the skeleton, the PEG mass fraction reaches 96.0 wt%, resulting in a phase change enthalpy of 181.5 J/g. The results suggest that this composite material is a promising PCM candidate for thermal energy storage applications.

Stable and reliable PEG/TiO2 phase change composite with enhanced thermal conductivity based on a facile sol-gel method without deionized water

Some shortcomings exist in organic phase change materials, including leakage susceptibility, low thermal conductivity, and preparation complexity. Herein, polyethylene glycol/titanium dioxide shape-stabilized composite phase change material (PEG/TiO2 ss-CPCM) was fabricated by facile sol-gel method without deionized water using tetrabutyl titanate (TBOT) as precursor. In this composite, not adding deionized water prolonged the gelation time, allowing PEG to bind as much TiO2 as possible and enhancing energy storage capability; TiO2 acted as the supporting framework to maintain the material's shape stability and enhance thermal conductivity. The melting and crystallization phase change enthalpies of prepared PEG/TiO2 ss-CPCM were 128.3 J/g and 113.1 J/g with an encapsulation efficiency of 74.14 % when PEG: TBOT = 1.5: 1. After repeating 300 thermal cycles, the phase change enthalpy remained almost constant. Besides, the thermal conductivity of PEG/TiO2 ss-CPCM was 1.22 times that of PEG, and the potential for thermal management applications. The advantages (energy storage capability, shape stability in thermal environments, thermal reliability, and thermal management) of the PEG/TiO2 ss-CPCM prepared by facile synthesis, not only propose a phase change material with excellent thermal properties and shape stabilization but provide a green and feasible strategy for the fabrication of PEG/TiO2 composite phase change materials utilizing the sol-gel method.

Energy and economic performance optimization of a window with variable transparency shape-stabilized PCM in hot summer and cold winter climate zone

Improving the thermal performance of windows is important for building energy efficiency. Filling windows with variable transparency shape-stabilized phase change materials (VTSS-PCM) improves the thermal inertia of windows while avoiding the leakage of PCM. In this paper, a new type of VTSS-PCM window was proposed, tested, simulated and optimized in hot summer and cold winter climate zone. A numerical model of the VTSS-PCM window was built, and the model was validated using experimental tests. On this basis, three key parameters of VTSS-PCM were investigated and optimized. Finally, the energy and economic performance of the optimized VTSS-PCM window were compared with a typical hollow glass window. The results showed that the total annual unfavourable heat transfer (TAHT) and the annual investment cost (AIC) of the VTSS-PCM window obtained from the optimization were 118.16 kWh/m2 and 8.53 CNY/m2, respectively. Compared with the hollow glass window, the VTSS-PCM window reduced the TAHT by 30.14% and the total annual cost by 28.39%. The VTSS-PCM window produced a better development potential in terms of energy performance and economic performance. This study provided a reference for the application of the VTSS-PCM window in hot summer and cold winter regions of China.

Innovative cementitious mortar incorporated with sepiolite based shape-stable phase change material for thermal controlling of buildings

In light of the urgent demand for enhanced temperature control within the realm of construction and building applications, this research presents an innovative shape-stabilized phase change material (PCM). Effective thermal energy storage has been made possible by combining myristic acid (MA) and lauric acid (LA) with sepiolite in cement mortars. These innovative PCM-incorporated mortars present promising solutions for reducing daytime cooling loads and enhancing thermal comfort in buildings. The research thoroughly examines the influence of Sepiolite infused with PCM on the thermoregulatory efficiency of cement mortar in specially designed test chambers simulating real ambient conditions. The research findings underscore the material's remarkable thermal stability, reliability, and capacity to efficiently absorb and release substantial latent heat. The study discloses the latent heat storage properties of the SEP/LA-MA composite, with 79.01 J/g absorbed during melting and 78.67 J/g released during solidification. Thermal durability, evaluated through 500 consecutive cycles, demonstrates consistent phase transition characteristics. Post-cycling, the composite maintains an impressive 78.68 J/g latent heat of fusion, retaining 99.5% of its original capacity. The TGA results emphasize the exceptional thermal stability of Sepiolite, LA-MA, and the composite, underscoring their ability to withstand typical operating conditions effectively. The introduction of these innovative cement-based composites with shape-stable PCM holds significant potential for enhancing various building components, aiming to elevate both energy efficiency and comfort levels in buildings.

Preparation and thermal performance enhancement of roasted iron tailings based shape-stabilized phase change materials for thermal storage

A new type of shape-stabilized phase change material (SSPCM) was fabricated for thermal energy storage (TES) using a facile synthetic strategy. Lauric acid (LA) was synchronously incorporated into the structural framework of roasted iron tailings (RIT) and graphene nanoparticles (GNP), in which RIT and GNP served as an ideal compatible supporting matrix, meanwhile, GNP was employed as a superior thermal conductivity additive, and LA acted as the working medium. The leakage results of the prepared composites were qualitatively and quantitatively analyzed. The surface morphology, chemical structure, thermal properties, heat transfer efficiency, thermal reliability, and thermal stability of the prepared SSPCMs were examined systematically. The prepared LA/RIT/GNP (5%) SSPCM exhibited relatively excellent thermal performance, which can meet the requirement of the future applications. Particularly, compared to pure LA, the measured thermal conductivity of LA/RIT/GNP (5%) with the addition of GNP was 9.03 times higher. The heat transfer efficiency of SSPCM was augmented by 91.67%. The mechanism of the improvement in thermal performance was revealed by the analysis of the microstructure characteristic parameters. In conclusion, the prepared SSPCM not only has great value in the low-temperature field of TES but also provides a new approach for high-value use of solid waste tailings, which expands the conventional utilization of iron tailings with a high-value approach.

Conceptual design and numerical analysis of a miscibility gap alloy-based solid-state thermal battery for electric vehicles

Heating the passenger cabin of electric vehicles at low temperatures consumes a large amount of battery power, resulting in a significant reduction in cruising range. On-board thermal energy storage is an effective way to improve the cruising range of electric vehicles in winter. Miscibility gap alloy is a new type of shape-stabilized composite phase change material, which has the advantages of high energy storage density, high thermal conductivity, low cost, and good safety. Therefore, using it to heat electric vehicles can increase their cruising range, prolong battery life, and reduce cost. In this paper, the concept of a compact on-board solid-state thermal battery based on miscibility gap alloy is proposed for the first time, and the heat charging, thermal insulation and heat discharging performance of the design are analysed based on numerical simulations. The results show that the thermal battery can reach a heat storage density of 553.8 Wh/L, and the average heat discharging power can reach 1.326 kW. The results of this paper can provide guidance for the engineering development of miscibility gap alloy-based solid-state thermal batteries.

Anisotropic and hierarchical porous boron nitride/graphene aerogels supported phase change materials for efficient solar-thermal energy conversion

The formation of shape-stabilized composite phase change materials (CPCMs) with special structure is an efficient strategy to prevent the leakage of phase change materials (PCMs) and improve the solar-thermal conversion ability. In this work, graphene and boron nitride nanosheets (BBNS) were prepared by the magnesiothermic reduction SHS method in CO2 and N2 atmosphere, respectively. Then, an anisotropic and hierarchical porous boron nitride/graphene aerogel with three-dimensional network was constructed by directional ice-freezing method using carboxymethyl cellulose as supporting framework and adhesive, and polyethylene glycol (PEG) was impregnated to prepare novel CPCMs. The CPCMs had enthalpies of 150∼160 J/g, and a highest thermal conductivity of 0.390 W/(m·K), which was around 47% higher than that of pure PEG. The ability of the CPCMs to convert solar energy to thermal energy was significantly enhanced. Under a simulated light intensity of sunlight (100 mW/cm2), its solar-thermal conversion efficiency reaches 94.92%, and after 20 min of irradiation, the surface temperature can reach 72 °C. These CPCMs are promising for the efficient use of renewable solar energy due to their high solar-thermal conversion efficiency and thermal storage capabilities.

Valorization of coconut peat to develop a novel shape-stabilized phase change material for thermal energy storage

Coconut peat (CP) is a product derived from coconut husks and it has been recognized as a valuable resource for the removal of heavy metals, as an oil-sorbent material, and for agricultural purposes. However, large quantities of coconut husks are still discarded yearly, leading to environmental pollution. In this study, a series of CP/polyethylene glycol (CP/PEG) composites were prepared as novel shape-stabilized phase change materials (SSPCMs) by vacuum impregnation to demonstrate a potential new application of CP in the area of thermal energy storage. The composites were investigated by thermogravimetric (TG) analysis, differential scanning calorimeter (DSC), scanning electron microscopy, attenuated total reflection-Fourier transform infrared spectrometer, leakage test, and thermal cycling testing. The results revealed that the CP/PEG composites exhibit minimal leakage of PEG while the composite with a CP/PEG mass ratio of 3:7 has a high latent heat storage of 108.5 J/g and relative enthalpy efficiency of 91.7%. Meanwhile, TG results indicated that it has good thermal stability up to 150 °C and the thermal cycling test showed that it has excellent thermal reliability even after 100 thermal cycles. The heat harvesting and releasing performance of the sample was evaluated as well to understand its thermoregulation capability. Therefore, the obtained CP/PEG composite demonstrates that it can potentially be utilized for thermal storage applications such as in wallboard or building materials for passive cooling, thus fostering a cleaner process by realizing energy savings.

Thermal regulation of photovoltaic panels using shape-stabilized phase change materials supported by exfoliated graphite/graphene nanofillers

This experimental research focuses on using shape-stabilized phase change materials (SS-PCMs) for thermal management of a PV panel. SS-PCMs are composed of 50% beeswax and 50% coconut oil, and exfoliated graphite (xGnP)/graphene (GP) nanoparticles to enhance shape-stabilization and thermal conductivity of the SS-PCM. The influence of weight fraction of xGnP/GP (φ = 0, 2.5, 5, 7.5, and 10%wt) and weight fraction ratio of GP to xGnP (α = 1/1, 1/3, 1/5, 1/7, and 1/9) on the performance of PV panel are evaluated. The results demonstrated that using the SS-PCMs, maximum temperature reduction of PV panel is from 60.52 °C to 44.06 °C, while it is 57.62 °C for PCM without nanofillers. It is identified that φ = 10% shows the minimum temperature and maximum electrical efficiency for the PV panel. However, the difference between PV temperature and electrical efficiency for φ = 7.5 and φ = 10 are not very remarkable. A small amount of GP and xGnP with α = 1/3 achieved the more shape-stabilized and high thermal conductivity PCMs. Finally, SS-PCMs with φ = 10 and α = 1/3 had maximum electrical efficiency of 13.50% and power of 80.15 W.

Shape-stabilized phase change materials for thermal energy storage and heat dissipation

Shape-stabilized phase change material (SSPCM) are widely used as energy storage materials due to its advantages of easy preparation and adjustable scale. But the thermal conductivity enhancement of SSPCM still need to be further studied to improve the energy storage efficiency. In this work, silicone rubber (SR)/paraffin@SiO2 (Pn@SiO2)/graphene nanoplates (GNPs) shape-stabilized phase change materials (SPG) with different GNPs content were prepared. Pn@SiO2 and GNPs can be homogeneously dispersed in the SR matrix due to the enhanced interfacial compatibility between Pn@SiO2 and SR. The leakage rate of SPG composites was as low as 0.25% due to the protection of SiO2 shell, SR matrix and GNPs. The SPG composites had excellent thermal storage properties, with the enthalpy about 50 J·g−1. The thermal conductivity of SPG composites was improved with the content of GNPs, the thermal conductivity of SPG reach 0.989 W·m−1·K−1 at a GNPs content of 10 phr. The low hardness of SPG composites above the phase change temperature can provide a more cohesive surface when applied to heat dissipation. The heat dissipation of the SPG composites in electric devices was simulated and demonstrated that the addition of GNPs made the heat dissipation rate of the SPG composites increased significantly. Therefore, the SPG composites can be applied in thermal energy storage and heat dissipation of electronic devices.

Numerical simulation and optimization of compact latent heat exchanger with micro-channel plate in shape-stabilized composite phase change material

To enable the rapid provision of domestic hot water, this study presents the independent design of a plate heat exchanger featuring a large heat exchange area and a compact structure. Utilizing a sandwich structure, the thermal storage unit integrates two shaped composite phase change materials (CPCM), namely sodium acetate trihydrate (SAT)/expanded graphite (EG) blocks of identical thickness — in conjunction with a micro-channel heat exchange plate. Multiple thermal storage units are stacked to create the heat exchanger. Experimental validation of the heat transfer performance of this thermal energy storage heat exchanger is conducted, accompanied by the establishment of a heat transfer model elucidating the interaction between the phase change material (PCM) and the fluid. The investigation explores the impact of varying thicknesses of shape-stabilized CPCM, thermo-physical parameters of CPCM, and flow rates on enhancing the thermal efficiency of the thermal energy storage heat exchanger. Results indicate a competitive relationship between the phase change enthalpy and thermal conductivity of CPCM under constant density. Increasing the mass fraction of SAT effectively boosts its heat storage density. However, this improvement is counterbalanced by a reduction in CPCM's thermal conductivity, resulting in diminished heat transfer rates within the material and reduced efficiency in transferring heat between the material and the fluid. Optimal performance is achieved when the mass fraction of sodium acetate trihydrate is 80 wt% and the CPCM thickness is 20 mm. At these parameters, the thermal energy storage heat exchanger exhibits the highest heat transfer efficiency. Furthermore, the heat exchanger is capable of producing 197.86 kg of hot water in 1365 s at an inlet flow rate of 300 L/h, achieving an impressive discharging efficiency of 82.73 %. These findings underscore the feasibility of employing the mini-channel plate thermal energy storage heat exchanger for the rapid preparation of domestic hot water.

A Novel Sandwich-Structured Phase Change Composite with Efficient Photothermal Conversion and Electromagnetic Interference Shielding Interface.

Stability and multifunctionality greatly extend the applications of phase change materials (PCMs) for thermal storage and management. Herein, CuS and Fe3O4 nanoparticles were successfully loaded onto cotton-derived carbon to develop a multifunctional interface with efficient photothermal conversion and electromagnetic interference (EMI) shielding properties. 1,3:2,4-di-(3,4-dimethyl) benzylidene sorbitol (DMDBS) and expanded graphite (EG) formed an organic/inorganic three-dimensional network framework to encapsulate 1-octadecanol (OD) by self-assembly. Finally, multifunctional shape-stabilized PCMs (SSPCMs) with the sandwich structure were prepared by the hot-press process. Multifunctional SSPCMs with high load OD (91%) had favorable thermal storage density (200.6 J/g), thermal stability, and a relatively wider available temperature range with improved thermal conductivity to support the thermal storage and management realization. Furthermore, due to the synergistic enhancement of two nanoparticles and the construction of the carbon network with cotton carbon and EG, highly efficient photothermal conversion (94.4%) and EMI shielding (68.9 dB average, X-band) performance were achieved at about 3 mm thickness, which provided the possibility of the multifunctional integration of PCMs. Conclusively, this study provides new insights towards integrating solar energy utilization with the comprehensive protection of related electronics.

Shape-stabilized nanosilver-modified grapefruit peel-based porous carbon composite phase change material with high thermal conductivity, photothermal conversion performance and thermal management capability

Polyethylene glycol (PEG) is greatly limited in the fields of phase change heat storing and solar energy absorption due to its low thermal conductivity, poor thermal stability and weak photo-thermal effect. Aiming at solving the above concerns, this work structures a new composite phase change material (PCM)(PEG/BPC@Ag) with biomass grapefruit peel-based porous carbon foam (BPC) as the backbone material and Nano-Ag as a surface-modified component, and the phase change medium PEG by simple vacuum immersion method. The test findings revealed that the modified carbon foam with Nano-Ag has excellent three-dimensional structure and photo-thermal effect, which makes the prepared composite PCM(CPCM) have enhanced photo-thermal transformation capacity, an enhanced thermal conductivity and excellent thermal stability. Among them, the thermic conductivity of the PEG/BPC@Ag was increased by 2.1 folds to 0.68 W/Mk. similarly, its enthalpy efficiency λ and was increased from 82.0 % to 83.7 %, and the photo-thermal transformation performance θ was increased from 76.8 % to 91.2 %. As well, the PEG/BPC@Ag has exceptional reusability and thermic robustness performance. Comprehensively, the PEG/BPC@Ag prepared in this work has a wide potential for application both in waste heat recovery and solar energy absorption, as well as in thermal management of electronic components, as well as providing a feasible solution for solid waste recycling in utilization.

Synergistic phase change and heat conduction of low melting-point alloy microparticle additives in expanded graphite shape-stabilized organic phase change materials

Organic phase change materials (PCMs) have great potential for efficient thermal energy storage and passive thermal management applications due to their non-corrosiveness, high heat storage capacity and stable operating temperature. However, low thermal conductivity and easy leakage seriously restrict the actual application. Meanwhile, heat transfer enhancers typically have a serious negative effect on the heat storage capacity of the PCMs. In this paper, a novel strategy for preparing high performance shape-stable composite phase change materials (CPCMs) is reported, utilizing paraffin wax (PW) as the energy storage material and expanded graphite (EG) as heat transfer enhancers and supporting material, especially in which low melting-point alloy (LMA) micro particles having same phase change temperature as PW are employed with two purposes: one is to provide extra latent heat, and another is to construct a hybrid three-dimensional thermal conduction network in microscale to achieve synergistic thermal conduction with EG. The resulting CPCMs exhibit excellent characteristics in energy storage capacity, thermal conductivity, and thermal cycling stability. The thermal conductivity of ternary CPCM can reach 5.842 W m−1 K−1 when the LMA and EG loading are 4.55 wt% and 9 wt%, which is about 16.4 times higher than that of pure PW, with no obvious volumetric latent heat reduction. This work provides a novel and promising approach for the preparation of CPCMs with high and fast storage properties.