Form‐stable Na ₂ SO ₄ ·10H ₂ O‐Na ₂ HPO ₄ ·12H ₂ O eutectic/hydrophilic fumed silica composite phase change material with low supercooling and low thermal conductivity for indoor thermal comfort improvement

Abstract

Summary In this research, a novel form‐stable composite phase change material (CPCM) based on Na2SO4·10H2O‐Na2HPO4·12H2O binary eutectic hydrated salt (EHS) as phase change material (PCM) and porous hydrophilic fumed silica (SiO2) as the carrier was prepared via the impregnation method, which is aimed at being integrated into building envelopes for the improvement of indoor thermal comfort and the reduction of building energy consumption. Thereinto, Na2SiO3·9H2O utilized as the nucleating agent suppressed the supercooling of the EHS enormously. Differential scanning calorimetry (DSC) result and the crystalline phase obtained by X‐ray diffraction (XRD) revealed that the mixture consisting of 20‐wt% Na2SO4·10H2O and 80‐wt% Na2HPO4·12H2O exhibited a eutectic melting behavior. Depending on DSC and leakage tests, the optimum amount of SiO2 in CPCM was determined as 30 wt%, which successfully stabilized the shape of the EHS to avoid leaking, simultaneously reduced thermal conductivity, and further facilitated its crystallization. Additionally, scanning electron microscope (SEM) manifested that the EHS was well adsorbed into the mesopores of SiO2. The obtained CPCM revealed an applicable phase transition temperature (25.16°C), moderate melting enthalpy (142.9 kJ·kg−1), negligible supercooling degree (0.24°C), and low thermal conductivity. More importantly, after 200 melting‐solidifying cycles, it displayed an excellent thermal reliability. All these results showed that the CPCM possessed desirable properties for applications.

Use of cellulose nanofibril (CNF)/silver nanoparticles (AgNPs) composite in salt hydrate phase change material for efficient thermal energy storage

“…The melting point was identical both before and after 100 melting/freezing cycles, and the enthalpy of PCM composite decreased only around 2% after 100 melting/freezing cycles relative to the enthalpy after one melting/freezing cycle. These two measurements indicated that the prepared PCM composite had a higher thermal reliability than previously reported, giving it a competitive advantage [58][59][60][61][62]. This prepared PCM composite with excellent thermal reliability is suitable to use in long-serving energy storage systems, improving the cost-effectiveness of these systems.…”

A Review of Composite Phase Change Materials Based on Porous Silica Nanomaterials for Latent Heat Storage Applications

“…The total heat storage capacity of the composite decreased from 134.0 to 111.6 J g −1 after 100 heating-cooling cycles. A similar amount of fumed silica (30%) was also needed to obtain shape-stabilized PCMs using the Na 2 SO 4 ·10H 2 O-Na 2 HPO 4 ·12H 2 O eutectic and Na 2 SiO 3 ·9H 2 O as nucleating agent [ 189 ].…”

Preparation of inorganic molten salt composite phase change materials and study on their electrothermal conversion properties

“…The authors of the paper synthesized LiNO 3 -KCl/SiO 2 composite PCM, achieving an energy storage density during the phase change stage of 3.4 × 108 J m −3 , which is 2.5 to 4 times higher than that reported in previous studies. [7][8][9] Qi et al proposed a hydroxylation method, resulting in a phase change enthalpy of the molten salt composite PCM reaching 355.52 J g −1 . 10 Shuai et al utilized porous silicon carbide ceramics and solar salt to form a composite PCM, resulting in a more uniform temperature distribution during phase change, with the maximum temperature difference reduced from 148 °C to 130 °C, and an overall phase change rate increased by 42.9%.…”