scholarly journals Silver Attached Graphene-Based Aerogel Composite Phase Change Material and the Enhancement of Thermal Conductivity

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3271
Author(s):  
Liang Zhang ◽  
Zhongke Shi ◽  
Buning Zhang ◽  
Jinhui Huang
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Waste Heat ◽  
Graphene Sheets ◽  
Renewable Energy Resources ◽  
Improve Energy Efficiency ◽  
Graphene Aerogels ◽  
Anisotropic Thermal Conductivity ◽  
Aerogel Composite

Phased energy storage technologies are highly advantageous and feasible for storing and utilizing clean renewable energy resources, for instance, solar energy and waste heat, and it is an effective method to improve energy efficiency and save energy. However, phase change energy storage has some problems, for example, low thermal conductivity and phase change leakage, which lead to limited application. In this paper, anisotropic graphene aerogels were prepared by ice crystal template method with high thermal conductivity of graphene, and silver was attached to the pore wall graphene sheets and the graphene sheet boundaries of the aerogels. The results show that anisotropic graphene aerogels were successfully prepared, and SEM and EDS indicate that up to 9.14 at % silver was successfully attached to the graphene sheets and boundaries. The anisotropic thermal conductivity of the PArGO phase change composites after adsorption of the paraffin is significant, with a maximum axial thermal conductivity of PArGO of 1.20 W/(mK) and radial thermal conductivity of 0.54 W/(mK), compared to the pure paraffin (0.26 W/(mK)) increased by 362% and 108%, respectively. The enthalpy of the composite has been reduced to 149.6 J/g due to the silver particles attached, but the thermal properties have been greatly improved. In experiments simulating real temperature changes, PArGO achieves phase transitions very fast, with a 74% improvement on thermal efficiency of storage and discharge over the pure paraffin.

Molecular Dynamics Predictions of Thermal Conductivity in Graphene for Phase Change Energy Storage Applications

2011 ◽  
Author(s):  
Masoud H. Khadem ◽  
Aaron P. Wemhoff
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Energy Storage ◽  
Phase Change ◽  
Md Simulations ◽  
Heat Diffusion ◽  
Graphene Sheets ◽  
Covalent Bonds ◽  
Energy Storage Applications ◽  
Change Material

Additives of highly-conducting nanoparticles such as graphene to a phase change material (PCM) improves PCM heat diffusion, which in turn produces better energy storage than pure PCM. Equilibrium Molecular Dynamics (EMD) simulations with Green-Kubo relations are used to predict the thermal conductivity of graphene sheets of various sizes and using different ensemble formulations. The Tersoff potential function has been implemented to model the covalent bonds between carbon atoms. The MD simulations predict an increase in thermal conductivity with graphene sheet size, and the predictions for the canonical (NVT) ensemble are consistently larger than those using the microcanonical (NVE) ensemble. The autocorrelation functions for the NVT simulations converge to zero for large sampling periods, which is not the case for NVE simulations.

scholarly journals A Form Stable Composite Phase Change Material for Thermal Energy Storage Applications over 700 °C

2019 ◽  
Vol 9 (5) ◽  
pp. 814 ◽  
Author(s):  
Zhu Jiang ◽  
Feng Jiang ◽  
Chuan Li ◽  
Guanghui Leng ◽  
Xuemin Zhao ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Waste Heat ◽  
Renewable Energy Sources ◽  
Composite Phase Change Materials ◽  
Change Material

Thermal energy storage (TES) is a highly effective approach for mitigating the intermittency and fluctuation of renewable energy sources and reducing industrial waste heat. We report here recent research on the use of composite phase change materials (PCM) for applications over 700 °C. For such a category of material, chemical incompatibility and low thermal conductivity are often among the main challenges. Our aims are to address these challenges through the formulation of form-stable composite PCMs and to understand their thermophysical properties. The eutectic K2CO3-Na2CO3 salt was used as a PCM with MgO as a form stabilizer. We found that such a formulation could maintain shape stability with up to 60 wt.% PCM. With a melting point of ~710.1 °C and an energy density as high as 431.2 J/g over a temperature range between 550 °C and 750 °C, the composite PCM was shown to be thermally stable up to 885 °C. An addition of 10 wt.% SiC enhanced the overall thermal conductivity from 1.94 W·m−1 K−1 to 2.28 W·m−1 K−1, giving an enhancement of 17.53%. Analyses of thermal cycling data also showed a high extent of chemical compatibility among the ingredients of the composite PCM.

scholarly journals Thermophysical Properties of Multifunctional Syntactic Foams Containing Phase Change Microcapsules for Thermal Energy Storage

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1790
Author(s):  
Francesco Galvagnini ◽  
Andrea Dorigato ◽  
Luca Fambri ◽  
Giulia Fredi ◽  
Alessandro Pegoretti
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Epoxy Resin ◽  
Storage Modulus ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Neat Epoxy ◽  
Low Density ◽  
Syntactic Foams

Syntactic foams (SFs) combining an epoxy resin and hollow glass microspheres (HGM) feature a unique combination of low density, high mechanical properties, and low thermal conductivity which can be tuned according to specific applications. In this work, the versatility of epoxy/HGM SFs was further expanded by adding a microencapsulated phase change material (PCM) providing thermal energy storage (TES) ability at a phase change temperature of 43 °C. At this aim, fifteen epoxy (HGM/PCM) compositions with a total filler content (HGM + PCM) of up to 40 vol% were prepared and characterized. The experimental results were fitted with statistical models, which resulted in ternary diagrams that visually represented the properties of the ternary systems and simplified trend identification. Dynamic rheological tests showed that the PCM increased the viscosity of the epoxy resin more than HGM due to the smaller average size (20 µm vs. 60 µm) and that the systems containing both HGM and PCM showed lower viscosity than those containing only one filler type, due to the higher packing efficiency of bimodal filler distributions. HGM strongly reduced the gravimetric density and the thermal insulation properties. In fact, the sample with 40 vol% of HGM showed a density of 0.735 g/cm3 (−35% than neat epoxy) and a thermal conductivity of 0.12 W/(m∙K) (−40% than neat epoxy). Moreover, the increase in the PCM content increased the specific phase change enthalpy, which was up to 68 J/g for the sample with 40 vol% of PCM, with a consequent improvement in the thermal management ability that was also evidenced by temperature profiling tests in transient heating and cooling regimes. Finally, dynamical mechanical thermal analysis (DMTA) showed that both fillers decreased the storage modulus but generally increased the storage modulus normalized by density (E′/ρ) up to 2440 MPa/(g/cm3) at 25 °C with 40 vol% of HGM (+48% than neat epoxy). These results confirmed that the main asset of these ternary multifunctional syntactic foams is their versatility, as the composition can be tuned to reach the property set that best matches the application requirements in terms of TES ability, thermal insulation, and low density.

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