Computational Analysis of Sugar Alcohols as Phase-Change Material: Insight into the Molecular Mechanism of Thermal Energy Storage

Abstract

Sugar alcohols are one promising candidate for phase-change materials (PCMs) in energy industrial societies because of their large thermal storage capacity. In this paper, we investigate the melting point and enthalpy of fusion related to the thermal storage of six-carbon sugar alcohols (galactitol, mannitol, sorbitol, and iditol) by molecular dynamics simulations and elucidate physical principles required for new PCM design. The computational melting points and enthalpies of fusion reproduce the experimental trend qualitatively. On the basis of the energy decomposition analysis we find that their enthalpies of fusion originate mainly from the decrease in the number and strength of intermolecular hydrogen bonds upon melting. Furthermore, we examine the origin of the difference of enthalpy of fusion between the four isomers. The results show that the larger enthalpy of fusion of galactitol and mannitol comes from their stable solid phases associated with the absence of notable repulsive electrostatic interaction between oxygen atoms in the molecule. In accordance with these results and an additional statistical survey, we propose the 3-fold guideline for developing new sugar alcohol like PCMs with larger thermal storage: (1) linear elongation of a carbon backbone, (2) separated distribution of OH groups, and (3) even numbers of carbon atoms.

Molecular structure and melting: implications for phase change materials

“…The rule of mixtures does not always predict ∆ fus H accurately for eutectics, especially if there are strong interactions between the components of the eutectic in the liquid phase. For example, the succinonitrile-phenanthrene eutectic system shows 32 ∆ fus H much larger than would be expected based on the rule of mixtures, likely due to non-ideal behaviour as exemplified by liquid-liquid phase separation.Inagaki and Ishida33 have examined the four six-carbon sugar alcohols: galactitol, They differ only in stereochemistry, with the hydroxyl groups on the four chiral centers arranged differently. Galactitol and mannitol were found to have high values of ∆ fus H (60 kJ mol -1 , 52 kJ mol -1 ) and T fus (460 K, 439 K), while sorbitol and iditol were found to have lower values (34 kJ mol -1 , 372 K, 31 kJ mol -1 , 353 K) 33.…”

Melting Point Depression and Phase Identification of Sugar Alcohols Encapsulated in ZIF Nanopores

“…Regarding sugar alcohols, this study focuses on erythritol as a representative of sugar alcohols having hydroxyl (OH) groups. The thermodynamic properties of sugar alcohols are substantially affected by the OH group, which forms strong intermolecular hydrogen bonds . Bulk erythritol has an outstanding heat of fusion (Δ h m = 337 J g –1 ) among sugar alcohols and a melting point ( T m = 118 °C, 391 K) not too far from the liquid water working range.…”

“…The thermodynamic properties of sugar alcohols are substantially affected by the OH group, which forms strong intermolecular hydrogen bonds. 29 Bulk erythritol has an outstanding heat of fusion (Δh m = 337 J g −1 ) among sugar alcohols and a melting point (T m = 118 °C, 391 K) 30 not too far from the liquid water working range. The short carbon chain is also suitable for being confined in the nanopores of a ZIF.…”

Development of Renewable Biomass-Derived Carbonaceous Aerogel/Mannitol Phase-Change Composites for High Thermal-Energy-Release Efficiency and Shape Stabilization

“…For example, erythritol has a high latent heat capacity of approximately 340 J/g. Furthermore, Inagaki et al , predicted that non-natural sugar alcohols can achieve a thermal storage density of up to 450–500 J/g. Such data are much higher than the other organic PCMs including the paraffin series (∼240 J/g) in the low-to-medium-temperature range.…”