Synthesis and thermal energy storage properties of xylitol pentastearate and xylitol pentapalmitate as novel solid-liquid PCMs

In this study, xylitol pentastearate and xylitol pentapalmitate were synthesized as novel solid-liquid PCMs by an esterification reaction in order to eliminate the unfavorable thermal properties of xylitol (such as high melting point) and stearic and palmitic acids (such as high melting point, low corrosivity, bad odor, and sublimating property). The synthesized ester compounds were characterized chemically by using Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance ( ¹H NMR) spectroscopy methods. By using the differential scanning calorimetry (DSC) method, the melting temperatures of xylitol pentastearate and xylitol pentapalmitate were measured as 32.35 °C and 18.75 °C, respectively, while their latent heats of melting were determined as 205.65 J g ^-1 and 170.05 J g ^-1 respectively. These results indicate that the synthesized PCMs have high latent heat values and suitable phase change temperatures for thermal energy storage applications. The thermal cycling test shows that the synthesized PCMs have good thermal reliability after 1000 thermal cycles. Thermogravimetric (TG) analysis results also reveal that the PCMs have good thermal stability over their working temperatures.