Tailored transition temperature plastic crystals with enhanced thermal energy storage capacity

Abstract

Pentaerythritol (PE), pentaglycerine (PG), and neopentylglycol (NPG) are non-ionic plastic crystal with high potential for latent heat thermal energy storage (TES) in solar heating applications. These molecules undergo reversible solid phase transitions with unusually large enthalpy of transition (110 J/g - 300 J/g) in the temperature range from 44 °C to 185 °C. To further enhance their heat storage capacity while lowering their price and preserving the advantage of solid phase transitions, a new class of shape-stabilized phase change materials (SSPCMs) in which a polyalcohol with adjustable solid phase transition properties (NPG/PG or PE/PG mixture) supports a cheaper and with higher latent heat solid-liquid PCM (paraffin wax) is proposed in this work. Combined with properly chosen paraffin waxes, NPG/PG mixtures allow tailoring the working temperature of corresponding SSPCMs between 24 °C and 81 °C, whereas PE/PG mixtures allow SSPCMs with phase change adjusted within 81 °C–190 °C temperature range. Produced SSPCMs were thoroughly characterized and their efficiency in terms of heat storage capacity and delivered power upon heat discharge were evaluated. The results achieved show proper anti-leakage effect due to good wettability between paraffins and polyalcohols and inner microstructure of SSPCMs promoting capillarity. In addition, volumetric latent heat storage capacity has been proven to be enhanced up to 45% compared to pure polyalcohols without detrimental effect in discharging power.