Thermal Properties of Alternative Phase Change Materials for Solar Thermal Applications

Phase change materials (PCMs) with a solid-solid phase transition are receiving increasing attention as promising materials for thermal energy storage (TES) systems. Unlike the more well-known and widespread solid-liquid PCMs, they generally have negligible volume change during phase transition, no contamination, and long cyclic life. Among the most studied solid-solid PCMs, a group of organic materials known as plastic crystals and their mixtures seem to show energy storage properties suitable for solar thermal systems at low-medium temperatures (80-150 & DEG;C). In this study, to deeply analyze their suitability for these applications, the thermophysical properties and thermal stability of two promising plastic crystals, pentaerythritol (PE) and pentaglycerine (PG), and their mixture are reviewed. The phase transition properties of these two pure substances were also assessed in this study through differential scanning calorimetry (DSC). The experimental measurements showed good agreement with the data collected from literature. The analysis showed that various properties and characteristics of these materials should be further investigated since a limited number of studies related to their properties is available. However, if their drawbacks are adequately addressed, the studied plastic crystals seem suitable for TES applications.