Abstract
Latent heat storage systems are gaining the attention of researchers as possible substitutes to conventional sensible heat storage systems due to their compactness and their ability to absorb and release heat almost isothermally. Among the Phase Change Materials (PCM) for energy storage studied so far, esters are believed to show promising properties. In particular, a broad range of melting temperatures, little to no supercooling, low corrosivity, chemical and thermal stability, and high enthalpies of fusion are reported. Many esters have the advantage of being bio-based and biodegradable, making them more sustainable in comparison to other popular PCM. Still, a clear lack of experimental data exists in regards to this class. In the present study, esters derived from saturated fatty carboxylic acids (myristic, palmitic, stearic, behenic), coupled with primary linear alcohols of different length (methanol, 1-decanol) were synthesized through Fischer esterification and their properties were investigated. Purities higher than 89% were obtained for all cases as proven by gas chromatography coupled with mass spectroscopy and nuclear magnetic resonance analysis. Additionally, the esters’ formation and reaction kinetics were characterized by attenuated total reflectance infrared spectroscopy. The esters produced showed to possess relatively high enthalpies of fusion above 190 J/g and thermal stability over three repeated cycles with differential scanning calorimetry. The melting points measured ranged between 20 °C and 50 °C, therefore proving to be interesting candidates for low-medium temperature applications such as heating and cooling in buildings. A correlation could be observed between the chemical structure and melting point of the produced esters. Additionally, thermogravimetric analysis revealed a higher thermal resistance for esters with longer aliphatic chains in comparison to shorter-chained ones.
Highlights
The recent trends in energy consumption and energy policies are shifting the focus to sustainable utilization of energy as a key issue [1,2]
Fatty esters from methanol and 1-decanol and fatty acids of different carbon chain length to be used as possible Phase Change Materials (PCM) were successfully synthesized through Fischer esterification with purities over 89%
While methyl esters of myristic, palmitic and stearic acid have been synthesized before and their thermal properties partially investigated, to the best of the author’s knowledge, a clear lack in experimental thermal data exists in regards of methyl behenate and all decyl esters produced
Summary
The recent trends in energy consumption and energy policies are shifting the focus to sustainable utilization of energy as a key issue [1,2]. Studies focused on salt hydrates as inorganic PCMs due to their availability, low cost, and high latent heat storage capacities. In order to allow for identification of potential esters to be used as future PCM in relevant temperature ranges, more experimental data on the thermal properties of esters is required. Examined 11 commercially available linear fatty esters for use as PCM, and confirmed the trends reported above for melting points in relation to molar mass. Synthesis of linear fatty esters from fatty acids of different even-numbered chain (C22 )), coupled with alcohols (methanol (C1 ) and 1-decanol (C10 )) was performed. 1-Decanol, and their availability limited.data has been found on fatty esters derived from 1-Decanol, and their commercial availability is limited
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