Polyethylene glycol/fumed silica composites as shape-stabilized phase change materials with effective thermal energy storage

Form–stable phase change materials (FSPCMs) composed of poly(ethylene glycol) (PEG) encapsulated in SiO2-modified expanded graphite (EG@SiO2) were prepared and investigated for thermal energy storage behaviors. The modification of SiO2 on EG was done using a simple sol–gel method, and then the resulting EG@SiO2 was introduced to confine PEG at varying content (60–90 wt %). Surface properties (including microstructure, morphology, and functional groups), PEG adsorptivity, leakage-proof ability, and thermal energy storage of the prepared materials were thoroughly characterized and discussed. The EG@SiO2 with 15 wt % SiO2 outstandingly adsorbed PEG as compared to the pristine EG, showing up >80 wt % of PEG. As a result, PEG was well stabilized in EG@SiO2 porous network without leakage, owing to capillary force, surface tension, and hydrogen bonding interactions. The optimal 80 wt % PEG/EG@SiO2 composite possessed high crystallinity (93.5%), high thermal energy storage capacity (132.5 J/g), and excellent thermal conductivity (4.086 W/m·K). In addition, it exhibited good cycling durability after 500 repeated melting/crystallization cycles. The high thermal efficacy and inexpensiveness would make the PEG/EG@SiO2 FSPCMs suitable for scale–up applications in thermal energy storage.

Section: Resultsmentioning

confidence: 84%

“…TGA curves of PEG and the obtained PEG/EG@SiO 2 FSPCMs. The TGA curve of pure PEG was obtained from our recent report …”

Section: Resultsmentioning

confidence: 99%

Polyethylene Glycol Confined in SiO₂–Modified Expanded Graphite as Novel Form–Stable Phase Change Materials for Thermal Energy Storage

Tien Nguyen,

Truong,

Duy Dat

et al. 2023

“…However, these peaks exhibited broadening, indicating that the calcination process at 2400 °C was insufficient to entirely convert the cotton into graphite. PEG, on the other hand, exhibited two prominent peaks at 19.2 and 23.3°, corresponding to the (120) and (032) crystal planes of PEG . Remarkably, the XRD patterns of the two composite samples distinctly displayed the characteristic peaks of PEG, implying that the crystalline structure of PEG was preserved, even after its incorporation with CCM.…”

Section: Resultsmentioning

confidence: 99%

Using Carbonized Cotton Fabric Waste to Prepare Poly(ethylene glycol) Composite Phase Change Materials with Improved Thermal Conductivity and Solar-to-Thermal Conversion

Tien Nguyen,

Minh Tam,

Thi Nhung

2024

Poly(ethylene glycol) (PEG) boasts excellent thermal energy storage capabilities but lacks efficiency in thermal conductivity and solar absorption. Simultaneously, the escalating concern surrounding the substantial volume of discarded cotton fabric underscores environmental issues. In this study, we devised composite phase change materials (PCMs) by embedding PEG into a carbon cotton material (CCM), varying PEG content from 50 to 80%, and conducted a comprehensive analysis of their thermal properties and solar-to-thermal conversion. The CCM, crafted from a waste 100% cotton towel through carbonization, provided an optimal porous structure that accommodated a significant 70% PEG content without any leakage, thanks to interactions such as surface tension, capillary forces, and interfacial hydrogen bonds. These PEG/CCM composites exhibited impressive crystallization fractions (>92%), resulting in notable thermal energy storage capacities ranging from 85.3 to 143.2 J/g as the PEG content increased from 50 to 80%. Moreover, these composites showed high thermal stability and exceptional cycling durability even after 500 melting/crystallization cycles. Notably, their thermal conductivities markedly increased to a range of 0.46−0.85 W/m•K compared to pure PEG's modest 0.24 W/m•K. Furthermore, the PEG/CCM composites substantially augmented visible and near-infrared (VIS-NIR) light absorption. Evaluation of solar-to-thermal conversion illustrated the composite's ability to efficiently convert solar energy into thermal energy, storing and subsequently releasing it through melting and crystallization processes. This study introduces a novel class of composite PCMs characterized by cost-effectiveness, outstanding thermal performance, and impressive solar-to-thermal conversion capabilities. These composite PCMs hold significant promise for large-scale solar-to-thermal energy storage applications while contributing to the sustainability of cotton waste management.

“…For the application of PEG/mARHA SSPCM in building thermal management, the SSPCM with 70% PEG was mechanically mixed with gypsum at 15 and 30% SSPCM and their thermal transfer delay was evaluated compared to pristine gypsum using an apparatus developed in our recent report. 37 Briefly, a portion of 30 g of the tested material was packed in a cylinder (30 mm × 70 mm), preconditioned in a lower-temperature bath (10 °C), and then moved to a higher-temperature bath (55 °C) for melting. After reaching plateau temperatures, the cylinder was moved back to the lower-temperature bath for crystallization.…”

Section: Methodsmentioning

confidence: 99%

Polyethylene Glycol/Rice Husk Ash Shape-Stabilized Phase Change Materials: Recovery of Thermal Energy Storage Efficacy via Engineering Porous Support Structure

Tien Nguyen,

Van Phuoc,

Thi Nhung

et al. 2024

This study focuses on modifying the porous structure of acid-treated rice husk ash (ARHA) to enhance the thermal energy storage capacity of poly(ethylene glycol) (PEG) confined within shape-stabilized phase change materials. The modification process involved a cost-effective sol−gel method in which ARHA was initially dissolved in an alkaline solution and subsequently precipitated in an acidic environment. ARHA, being a mesoporous SiO 2 -based material with a high surface area but low pore volume, had limited capacity to adsorb PEG (50%). Furthermore, it hindered the crystallinity of impregnated PEG by fostering abundant interfacial hydrogen bonds (H-bonds), resulting in a diminished thermal energy storage efficiency. Following modification of the porous structure, the resulting material, termed mARHA, featured a three-dimensional macroporous network, providing ample space to stabilize a significant amount of PEG (70%) without any leakage. Notably, mARHA, with a reduced surface area, effectively mitigated interfacial H-bonds, consequently enhancing the crystallinity of impregnated PEG. This modification led to the recovery of thermal energy storage efficacy from 0 J/g for PEG/ARHA to 109.3 J/g for PEG/mARHA. Additionally, the PEG/mARHA composite displayed improved thermal conductivity, reliable thermal performance, and effective thermal management when used as construction materials. This work introduces a straightforward and economical strategy for revitalizing thermal energy storage in PEG composites confined within RHA-based porous supports, offering promising prospects for large-scale applications in building energy conservation.