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Thermal energy storage (TES) systems are significant to solve inevitable intermittency and curtailment issues of clean renewable energy sources. Thus, the high-density and high-efficient TES technologies are required to achieve carbon neutrality. This study aims to synthesize an egg-carton-shaped paraffin microsheet for high-density latent heat storage. Poly(methyl methacrylate) (PMMA) microparticles (3 μm in diameter) are homogeneously placed onto a silicon wafer (10 × 10 mm2) via Langmuir–Blodgett technique. The PMMA monolayer on the silicon wafer is then dipped in a colloidal silica sol and dried to form the bottom structure of the egg-carton. Paraffin, a phase change material with a large melting enthalpy, is injected into the void space of the egg-carton produced by the decomposition of the PMMA particles. Finally, the upper silica shell covers the egg-carton structure with spherical paraffin to ultimately obtain an approximately 3.4-μm-thick microsheet for latent heat storage. The thermal performance of the paraffin microsheets is evaluated using differential scanning calorimetry. The encapsulation ratio, defined as the mass ratio of the paraffin to the microsheet, is calculated to be approximately 80.2%. This novel paraffin microsheet enables an increase in the TES capacity and ultimately overcomes poor heat transfer in paraffin owing to its low thermal conductivity. [Display omitted] • Egg-carton-shaped paraffin microsheet with 3.4 μm thickness is synthesized by Langmuir–Blodgett technique, sol-gel reaction, and dip-coating. • Low TEOS concentration improves denseness of the egg-carton-shaped SiO 2 structure. • 35% enhanced heat storage capacity was obtained in the paraffin microsheet, compared to water. [ABSTRACT FROM AUTHOR]

Abstract Nanocomposites consisting of paraffin/graphene nanoplatelets mix embedded in carbon foams via vacuum infiltration were fabricated with the aim of developing new phase change material (PCM) formulation with excellent shape stabilization, improved thermal conductivity and outstanding thermal reliability and structural stability. Physicochemical and thermal properties of the nanocomposites were evaluated using a suite of techniques such as scanning and transmission electron microscopy, X-ray diffraction, attenuated total reflection - Fourier transform infrared spectroscopy, nitrogen adsorption analyzer, differential scanning calorimetry, mechanical tester, Raman spectroscopy, thermal conductivity analyzer and thermogravimetric analyzer. The carbon foams exhibited good cyclic compressive behavior at a strain of up to 95% and kept part of their elastic properties after cyclic testing. Due to the robust mechanical integrity and layered meso-/macroporous morphology of these carbon foams, the nanocomposites are well equipped to cope with volume changes without leaking during thermal cycling. A 141% thermal conductivity enhancement observed for the carbon foam nanocomposite demonstrates the contributing role of the carbon foam in creating effective heat transfer through its conductive 3D network. The results have shown that proper chemical modification and subsequent carbonization of the low cost porous foams can lead to ultralight multifunctional materials with high mechanical and physical properties suitable for thermal energy storage applications. Highlights • Developed new carbon foam nanocomposites for thermal energy storage. • Carbon foam can embed the PCM mix while enhancing its thermal conductivity. • PCM consists of graphene nanoplatelets dispersed in paraffin wax. • A 141% thermal conductivity enhancement of the nanocomposite has been demonstrated. • Nanocomposites exhibit excellent thermal reliability and stability. [ABSTRACT FROM AUTHOR]

Abstract Encapsulated paraffin-type phase change materials are considered important candidates for thermal energy storage applications. In this paper, we present icosane coated in a layer-by-layer fashion using the weak polyelectrolytes poly(acrylic acid) and poly(allylamine) in order to create ultra-thin cross-linkable and robust polymer encapsulations with storage capacities close to the pristine icosane. After coating, SEM images displayed an average particle size between 20 and 50 µm. Generally, smooth surface structures of the coated particles compared to uncoated icosane-surfactant particles, 1H NMR and FT-IR spectra as well as fluorescence imaging confirmed the successful encapsulation. Calculations of the PCM content revealed that the final product consisted of 88.6% core material. Accordingly, the resulting PCM capsules showed high storage capacities of 199.1 J g−1 close to the original value of pristine icosane (223.6 J g−1). Thermal stability was confirmed by TGA, revealing an increased resistance to thermal degradation of the coated particles (T 10, bulk = 175.7 °C and T 10, capsule = 186.8 °C). Moreover, repeatability and reliability of the phase change behavior were confirmed in thermal cycling experiments including 100 heating-cooling cycles with no observable influence on the performance of our material. Graphical abstract fx1 Highlights • Layer-by-layer coated phase change materials have been fabricated. • Weak polyelectrolytes can provide stable encapsulation of icosane as PCM. • A storage capacity close to the pristine PCM can be maintained. [ABSTRACT FROM AUTHOR]

In this study, a novel microencapsulated phase change material, paraffin@Cu-Cu 2 O, was prepared by a hydrothermal method. The diameters of the microcapsules were 600–900 nm. The micro morphology, chemical compositions, phase change properties, and thermal stability of the products were characterized. It was calculated that the encapsulation efficiency of the microencapsulated paraffin@Cu-Cu 2 O composite was 62.79%. The melting temperature and freezing temperature of products were close to those of paraffin, but the products had better thermal stability and higher thermal conductivity because of the metal shell materials. Additionally, we compared the paraffin@Cu-Cu 2 O slurry with paraffin emulsion, and we found that the slurry had better light absorbing properties, thermal conductivity, and photo-thermal conversion performance. The developed material is a promising candidate for application in direct absorption solar collector systems. [ABSTRACT FROM AUTHOR]

This study was to explore the hydrophilic surfactant/Brij L4 mixture scheme for fabrication of highly stable paraffinic nano-emulsions melting at 55 °C by the low-energy phase inversion temperature method that has not been reported previously. Two commercial paraffin waxes were chosen as the PCM agents, Sasolwax 5203 with a higher onset T m of 54 °C in the initial development and OP44E with a lower onset T m of 44 °C for further assessment and fabrication. At accelerated stability testing by thermal approach, the rate of droplet size increase was mainly attributed to Ostwald ripening destabilization mechanism, and decreased by about 5 times for every 5 °C drop. Only a moderate increase in the particle size was observed, from 47.7 nm to 120.6 nm, over a period of 9 months at 45 °C. The exciting results in the accelerated stability evaluation greatly outperformed than those previous results only obtained from the regular stability testing including room temperature storage and heating-cooling cycles in a container, and hence this experimental result can offer a more meaningful reference in terms of service life of nano-emulsions flowing in pipelines. With the optimized surfactant mixtures, a series of highly stable paraffinic nano-emulsions in the working temperature range of 30–50 °C were successfully formulated as promising coolants in the active thermal management system. • High melting point paraffin PCM nano-emulsions/suspensions were fabricated by phase inversion temperature method. • The PCM nano-emulsions remained stable over 9 months at 45 °C up to 120.6 nm particle size. • Ostwald ripening was identified as the major destabilization mechanism at 45 °C or higher. • A novel polymetric nucleating agent has been found effective for supercooling reduction. • The excellent stability and relatively high latent heat were desirable for thermal management. [ABSTRACT FROM AUTHOR]

Radiative cooling promises an effective strategy against global warming by sending waste heat to the deep universe in a passive manner. However, the mismatch between cooling supply and demand can significantly compromise the efficacy of spectrally-static radiative cooling devices in cold weather. Therefore, the present work introduced paraffin wax as the phase change material (PCM) to develop a spectrally self-switchable cover (SSC) for flexible radiative cooling. The transmittance of the paraffin wax at different temperatures, thicknesses and phases was characterized. In the UV-VIS-NIR band, the transmittance of the paraffin wax was over 90% in the liquid phase but below 5% in the solid phase. In the "atmospheric window" band, the transmission of the paraffin wax in the liquid phase was also much higher than that in the solid phase with a maximum difference of 41.1%. The optical constants of various paraffin waxes in solid and liquid phases were calculated according to the two-thickness inversion method. The average error of transmittance between the calculated and measured values was only 1.8% and 4% for the 0.19–1.1 μm and 8–13 μm bands, respectively. Moreover, the microstructure analysis of the solid-state paraffin wax revealed that the size of paraffin grains was around 10 μm with interlocking and irregular grain boundaries. The integrated multilayered-like structure resulted in a significant transmittance reduction of the solid-state paraffin wax. In the end, self-switchable PE-PCM-PE (polyethylene-phase change material-polyethylene) covers were prepared and spectrally characterized. The paraffin-based cover provided a new and low-cost candidate solution for achieving dynamic radiative cooling. [Display omitted] • The paraffin transmittance is significantly different between liquid phase and solid phase. • The multilayer-like structure of paraffin crystal grains reduces the transmittance of solid-state paraffin. • The optical constants of paraffin are considerably different in liquid and solid phases by the two-thickness inversion method. • The polyethylene-phase change material -polyethylene shows potential as a spectrally self-switchable cover. [ABSTRACT FROM AUTHOR]

In this paper, graphite nanoparticles have been dispersed into a paraffin/water emulsion with the purpose of improving the thermal conductivity and photothermal conversion performance of the emulsion. The melting enthalpy and apparent specific heat of 20 wt% paraffin/water emulsion is 39.2 J g − 1 and 9.105 J g −1 K −1 and its melting and freezing temperatures are very close to those of paraffin. Moreover, the 300 heating–cooling cycles test indicates that the paraffin/water emulsions containing 0.1 wt% graphite exhibits good thermal reliability. The viscosities of all samples are lower than 0.0750 Pa s, meeting the transportablilty requirements in pump systems for applications. In addition, the thermal conductivity of the emulsion containing 0.1 wt% graphite increases by 20.0% as compared to the base fluid and its receiver efficiency is higher than 86.0% as the temperature ranges from room temperature to 80 °C. As a result, the paraffin/water emulsion containing graphite with high energy storage capacity, enhanced thermal conductivity and excellent photo-thermal performance, good thermal reliability and good fluidity shows great potential for use as advanced heat transfer fluid (HTF) in the low temperature applications of direct absorption solar collector (DASCs). [ABSTRACT FROM AUTHOR]

Double-shell alginate microcapsules containing paraffin phase change material (PCM) were prepared for latent heat storage by a method of repeated interfacial coacervation/crosslinking. The proposed process consisted of three main steps: (1) preparation of paraffin containing core particles by dripping an O/W emulsion of melted paraffin and aqueous sodium alginate into a calcium chloride ionic cross-linking solution, (2) encapsulation of the core particles into double alginate shell by ionic gelation/crosslinking by repeated interactions between the sodium alginate and calcium chloride solutions, and (3) consolidation of the capsule shells by contact heat treatment. The effects of process parameters such as the sodium alginate concentration, the calcium chloride concentration in certain stages of the process, and the contact time between the formed core particles and the surrounding alginate solution on the paraffin content and the mean diameter of capsules were studied by experimental design and statistical evaluations. The prepared PCM capsules had uniform sizes, core/shell structure, double-walled non-porous alginate coating, tunable void space inside the core, and suitably high paraffin content at properly selected process conditions, corresponding to 95.0 J/g melting and 91.7 J/g freezing latent heat capacity. Thermogravimetric analysis and repeated thermal cycling evidenced good thermal stability, and proper mechanical strength for leakage free microcapsules. [ABSTRACT FROM AUTHOR]

Highly paraffin/butyl stearate-loaded phase change microcapsules were synthesized by cosolvent-free interfacial polymerization using low-toxicity dicyclohexylmethane-4, 4′-diisocyanate as the shell material. The formation of the microcapsules and their distribution in the epoxy were studied by means of optical microscope and scanning electron microscopy, respectively. The chemical composition of microcapsules was confirmed through Fourier transform infrared spectrometer. And the phase change properties, thermal stability and cyclic thermal stability of microcapsules and their thermal insulation properties and thermal response behavior in the epoxy were investigated through differential scanning calorimetry, thermogravimetric analysis, leakage prevention test, thermal conductivity test and temperature response experiment, respectively. The synthesized spherical microcapsules have distinct core-shell structure with an average diameter of 220.6 μm. The microcapsules achieve an encapsulation rate of 78.5%, with the melting enthalpy and the crystallization enthalpy being 148.5 J/g and 159.2 J/g, respectively. They not only exhibit good thermal stability and cyclic thermal stability, but also can disperse in the epoxy uniformly and combine with the epoxy tightly. In addition, compared with the pure epoxy, the epoxy containing 15 wt% microcapsules experiences a 10.1% decreases in thermal conductivity and a 55.4% increase in delayed time of temperature rise/fall, showing an excellent temperature regulation ability. [Display omitted] • HMDI was employed as the shell material due to low toxicity. • The microcapsules with core-shell structure achieve an encapsulation rate of 78.5%. • High enthalpy microcapsules exhibit 99.2% of heat-storage efficiency. • The microcapsules have high thermal stability, reliability and applicability. • 15 wt% microcapsules increase the time delay by 55.4% for temperature rise/fall. [ABSTRACT FROM AUTHOR]

The utilization of aerogel with the 3D network structure is regarded as an important method to construct phase change materials (PCMs). In this work, a series of novel paraffin-based composite PCMs were fabricated with boron nitrid@chitosan aerogel (BNCA) as skeleton materials by a freeze-drying and impregnation method. XRD, SEM, TGA, Hot Disk, DSC and FT-IR were used to character the samples and thermal cycles were employed to measure the shape stability. The results revealed that paraffin wax (PW) had been successful and effectively embedded into the prepared BNCA with a porous structure. Moreover, the morphologies of BNCA/PW composite remained stable after 100 times thermal cycles. In addition, the thermal conductivity of BNCA/PW composite was notably high as 1.14 W/(m·K), which was 4.07 times higher than PW (0.28 W/(m·K)). Simultaneously, the phase temperatures of BNCA/PW composite containing 41 wt% skeleton were 50.5 and 52.9 °C, and its latent heats were 118.4 and 114.9 J/g, respectively. The BNCA/PW composite showed an excellent chemical compatibility between PW and BNCA, and presented broad application prospects in energy storage of electronic systems. [Display omitted] • Synthesis of porous boron nitride@chitosan aerogel by freeze-drying method. • Synthesis of BNCA/PW composite PCMs by vacuum impregnation. • The mass fraction of paraffin can be controlled, without leakage. • Good thermal conductivity and thermal reliability of BNCA/PW composite PCMs. • After 100 thermal cycles, the thermal properties and shape stability of the composite remain good. [ABSTRACT FROM AUTHOR]

In the present work, a thermo-economic performance of the modified hemispherical solar still (MHSS) was studied and compared to traditional hemispherical solar still (THSS). The modulations accounted for two additives, namely: paraffin wax as phase change materials (PCM), and copper oxide (CuO) nanoparticles. Three cases of MHSS were investigated and compared to THSS: (0.3 wt%) CuO nanomaterials were immersed in the basin water, implementing PCM container below the basin, and combining PCM container below the basin plus mixing CuO nanoparticles in the basin water. The basin water depth in all stills was set at 1.0 cm in all cases. Moreover, the thermo-economic performance of the four studied cases was compared and evaluated by determining the freshwater productivity, the daily energy efficiency, and the freshwater cost. Experiments have been carried out on the proposed hemispherical distillers under hot climatic conditions of El-Oued (33°27′N, 7°11′E), Algeria. The results show that the single utilization of CuO/water nanofluid and pure PCM improved productivity by 60.41% and 29.17%, respectively, compared to THSS. While, the dual usage of PCM and CuO/water nanofluid further enhanced the productivity by up to 80.20%, relative to THSS. Moreover, the daily energy efficiencies of the hemispherical distillers under the different studied cases (THSS, MHSS/PCM, MHSS/CuO-water nanofluid, and MHSS/PCM + CuO-water nanofluid) were found to be 35.52%, 45.45%, 56.46%, and 63.61%), respectively. The economic feasibility of these modifications presented that the dual usage of PCM and CuO/water nanofluid is more effective as it reduces the cost of freshwater production by 75% compared to THSS. In the third distiller (Modified hemispherical solar still with 0.3 wt% CuO/water nanofluid (MHSS-CuO/water NF)), the modified was done by adding (0.3 wt%) copper oxide (CuO) nanomaterials to the basin water, to improve the thermal properties of nanofluid and increase the intensity of the absorbed solar energy. In the fourth distiller (Modified hemispherical solar still with paraffin wax as phase change materials and 0.3 wt% CuO/water nanofluid (MHSS-PCM + CuO/water NF)), it was designed and constructed a circular galvanized steel container 1 mm thick, 340 mm diameter, and edge height 40 mm, coated with the black pained. This container was placed inside the wooden basin of the hemispherical solar still. A gap of 20 mm thickness was maintained between the container and the wooden basin on the bottom side and sidewall. 2.0 kg of paraffin wax as phase change materials was placed in the gap between the container and the wooden basin, to store the solar energy in the periods of higher solar rays and recovery it in the periods of low solar rays and after sunset. Moreover, in this modification copper oxide (CuO) nanomaterials were also added to the basin seawater with a concentration of 0.3 wt%, to improve the thermal properties of saline water and increase the intensity of absorbed solar energy, and improve the rates of heat transfer. • Dual usage of PCM and CuO nanofluid has great influence on hemispherical distiller performance. • Thermo-economic performance of the modified hemispherical solar still was studied. • Dual usage of PCM and CuO/water nanofluid enhanced the productivity by 80.20%. • Dual usage of PCM and CuO/water nanofluid reduces the freshwater cost by 90%. • Daily efficiency of MHSS with dual usage of PCM and CuO/water nanofluid reached 63.61%. [ABSTRACT FROM AUTHOR]

In this work, a novel sort of form-stable phase change materials (FSPCMs) which possesses simultaneously the shape memory function was designed and prepared. The FSPCMs consist of paraffin with melting point of approximately 53°C as a latent heat storage material and olefin block copolymer (OBC) as a supporting material. With mass percentage of paraffin up to 40wt%, the FSPCMs exhibit good shape stability until temperature approaches 90°C as shown by visual photographs, and this result is confirmed by dynamic mechanical analysis. At the same time, composites with 40wt% paraffin also maintain the excellent mechanical property of OBC and exhibit large elongation at break as well as similar tensile stress, insuring excellent tenacity and deformation ability. The results of shape memory testing demonstrate that the composites possess good shape memory property, with nearly complete shape fixing and recovery. Compared with other reported FSPCMs, this material can be both temperature-controlled and temperature-sensitive, and may show advantages in some advanced applications such as intelligent textile. The diversity of paraffin endows the composites with flexibility of design for applications with wide range of temperatures. Considering the inexpensive sources and easy processing, this work may open up opportunities to produce difunctional FSPCMs in the industrial field. [ABSTRACT FROM AUTHOR]

Abstract: Oleochemical carbonates are biobased materials that were readily prepared through a carbonate interchange reaction between renewable C10–C18 fatty alcohols and dimethyl or diethyl carbonate in the presence of a catalyst. These carbonates have various commercial uses in cosmetic, fuel additive, and lubricant applications. Oleochemical carbonates have not been examined for their applicability as phase change materials (PCM). The latent heats of melting and freezing for a series of symmetrical oleochemical carbonates ranging from 21-37 carbon atoms were evaluated to develop a fundamental understanding of the solid–liquid transitions for utilization in thermal energy storage (TES) applications. The phase transitions and associated thermal properties were determined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl carbonates had peak melting and freezing points of −2.2, 19.3, 33.7, 44.9, and 51.6 and −6.3, 14.3, 28.7, 40.3, and 46.9°C, respectively. In general, these carbonates exhibited sharp phase transitions and good latent heat properties. The latent heats of melting and freezing for decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl carbonates were 144, 200, 227, 219, and 223 and 146, 199, 229, 215, and 215J/g, respectively. These carbonates represent novel renewable-based PCM chemicals that compliment fatty acids, fatty alcohols, and their fatty acid esters while providing a potentially valuable biobased alternative to paraffin wax and salt hydrate PCM currently dominating the PCM market. [Copyright &y& Elsevier]

The COVID-19 pandemic has led to an increase in construction energy consumption and indoor occupancy; this, in turn, has increased the demand for energy efficiency. Thermal energy storage is an effective method for energy saving and improving efficiency. In this study, improved shape-stabilized phase change materials (SSPCMs) for enhancing the energy efficiency of buildings were manufactured and evaluated. These SSPCMs were prepared via the vacuum impregnation of n-octadecane into bentonite nanoclay. Bentonite exhibits a layered tetrahedral and octahedral crystal structure with Na+ cations (which feature high cation exchange capacity) in the interlayer space. The Na+ ion is a hydrophilic ion that affects the properties of the interlayer. However, paraffin-PCMs are hydrophobic and have poor compatibility with water. Therefore, hydrophobicity is induced in the organic nanoclay by using an organic modifier as the PCM container. Cloisite Na+, Cloisite 15, Cloisite 20, and Cloisite 93 were used to fabricate the SSPCMs. This study compares the amount of PCM impregnated depending on the compatibility of different PCMs between hydrophilic/hydrophobic nanoclays and also evaluates the thermal performance. The observed reduction in peak temperature and the time lag effect of the PCMs confirmed that the organically modified nanoclay and the PCM composites significantly improved the amount of PCM impregnated, thermal conductivity, and latent heat characteristics. The latent heat of the hydrophobic organic nanoclay was 209% higher than that of the SSPCM-based hydrophilic nanoclay. • Composites using paraffin PCM and nanoclay were fabricated and analyzed. • Hydrophobic nanoclay showed 124% higher PCM impregnation than hydrophilic nanoclay. • It was observed that PCM impregnation was affected by the microstructure. • SSPCMs showed up to 84% improved thermal conductivity than pure PCM. • The overall thermal performance in the SSPCM based hydrophobic nanoclay were high. [ABSTRACT FROM AUTHOR]

Combining hybrid photovoltaic/thermal (PV/T) and photovoltaic/phase change material (PV/PCM) systems in a so called hybrid PV/T/PCM system is a potential solution for the high temperature gradients and unsatisfactory thermal regulation in conventional PV/T systems. Several combinations of different PCMs and different types of nanomaterials at different loadings are employed in this study to overcome the increased PV-temperature levels in the presence of a PCM and improve both the cooling and the thermal regulation of hybrid systems. A finite difference numerical model was developed and validated to evaluate the average PV panel temperature, the temperature gain across the cooling fluid, the thermal and electrical efficiencies, and the temperature distribution along the PV panel for the hybrid PV/T/nano-enhanced PCM system. The effects of the solar concentration and the operation season (summer or winter) were also assessed. Four types of PCMs and four nanoparticle materials were used at high loadings of 10 wt %, 20 wt %, and 30 wt %. When paraffin wax RT35 is used as the PCM, although the temperature increasing magnitude along the panel decreases from 41% to 12%, PV-temperature levels increase compared to the conventional PV/T system (65 °C with RT35 compared to 47.5 °C without a PCM). Increasing the loading of nanoparticles in a PCM provides better cooling and improved overall performance. Among the nanomaterials, Multi-walled carbon nanotube is the best to obtain better cooling (52 °C for RT35/MWCNT at a loading of nanoparticles of 10 wt %) and higher overall performance. Also, the addition of nanoparticles is more effective at higher solar concentrations. The CaCl 2.6H 2 O PCM provides better performance and relatively lower temperature levels, while the RT35 provides better thermal regulation of the PV panel, but at relatively higher temperature levels. No previous work has been conducted to study the effect of different combinations from the nano-enhanced PCMs on the performance and thermal regulation of the new hybrid PV/T/nanoPCM systems. In addition, the study is the first to assess their effect at high loadings of the nanomaterials and under different solar concentrations in summer and winter. • First to study effect of multiple nanoPCM mixtures on the performance and thermal regulation of hybrid PV/T/nanoPCM system. • High nanoparticles loadings, up to 30 wt%, are applied for the first time in this study. • CaCl 2.6H 2 O provides better thermal and electrical performance, while RT35 provides better thermal regulation. • Multi-walled carbon nanotube is the best nanomaterial to obtain better cooling and higher performance. • Addition of nanomaterials to the PCM is more effective at high solar concentrations. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) graphene-reinforced structural materials with excellent solar-thermal conversion, mechanical and thermal transfer properties present attractive prospects for the fabrication of high-performance composite phase change materials (PCMs). Herein, multifunctional 3D continuous sponge frameworks wrapping with reduced graphene oxide (rGO) are facilely prepared via simply circular impregnation and in-suit reduction process. Further, the stable combination of 3D support material and phase change matrix through vacuum melting infiltration can successfully obtain the rGO@sponge framework/paraffin wax (rGO@SF/PW) composite shape-stabilized PCMs. As an advanced energy conversion and storage PCMs, the rGO@SF/PW achieves efficient solar-thermal conversion effciency of 85%, excellent energy storage properties (phase-change enthalpy of 170.4 J/g for the loading amount of 90 wt%), high thermal transfer performance and good cycling thermal stability. Based on the comprehensive performances of the rGO@SF/PW, domestic storage systems for solar-thermal water are designed to broaden the application of PCMs in the solar-thermal energy area. • Multifunctional three-dimensional continuous sponge frameworks wrapping with reduced graphene oxide are facilely prepared via circular impregnation and in-suit reduction process. • The composite phase change materials exhibit excellent energy storage properties and high thermal conductivity. • The obtained shape-stabilized composite phase change materials achieves efficient solar-thermal conversion effciency of 85%. • Domestic storage systems for solar-thermal water are designed. [ABSTRACT FROM AUTHOR]