A review on thermophysical properties and thermal stability of sugar alcohols as phase change materials

The increasing use of renewable energy sources has highlighted the importance of energy storages, and in particular of latent heat thermal energy storages (LHTESs). Among the phase change materials (PCMs) that can be used in such systems, sugar alcohols (SAs) are considered potential substances that may lead to interesting applications in the LHTES sector. In this work, a detailed literature review analysis of six SAs (xylitol, sorbitol, erythritol, mannitol, inositol, dulcitol), their thermophysical properties, their thermal stability and their main LHTES applications is presented for the first time. The thermophysical properties under discussion include melting and crystallization temperatures, latent heats of melting and crystallization, specific heat, thermal conductivity, density and dynamic viscosity. Thermal stability was evaluated by taking into account studies of thermal endurance, degradation temperature and cycling stability. Differential scanning calorimetry (DSC), T -history, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were considered as measurement techniques. Applications include the use of SAs in solar collectors and cookers, heat exchangers, porous materials, absorption cooling systems, mobilized thermal energy storages (M-TESs). New measurements of phase transition properties and degradation temperature for the studied SAs were also carried out by the authors of the present study. A good agreement between the proposed data and the literature values was found. The analysis reveals that some SAs may be considered suitable for low-to-medium temperature LHTES appli-cations, provided that their drawbacks are adequately evaluated and addressed. To this purpose, the study also highlights the most critical aspects that should be considered when developing both fundamental research and engineering applications related to SAs.