Long-chain diesters of fattyy alcohols as novel phase change materials for thermal energy storage

Abstract

In this study, long chain diesters of fatty alcohols were synthesized for use in thermal energystorage applications. Long-chain diesters of adipic acid were proposed for the first time in thisstudy to be used as phase change material (PCM). For this purpose, ditetradecyl adipate (DTA)and dioctadecyl adipate (DOA) were synthesized as novel solid-liquid PCMs by means of thedirect esterification reaction of adipic acid with 1-tetradecanol and 1-octadecanol. The reactionwas yielded at around 90% as an average at the end of 6 hours. The DTA and DOA werecharacterized chemically using FT-IR and 1HNMR techniques as the energy storageproperties, total enthalpy, and specific heat (Cp) capacity values were determined by DSCanalysis. Melting temperatures and enthalpies of DTA and DOA were measured as 44 and 60C respectively; and 142.4 and 186.2 Jg-1 respectively. Total enthalpy calculation showedthe latent heat storage capacity along with sensible heat capacity of fatty alcohols and longchain diesters between 0 and 80 C. Cp values of fatty alcohols and long-chain diesters alsocalculated for solid and liquid phase separately. TGA analysis was performed to determinethermal stability of the esters. DTA and DOA compounds were found stable up to 248.3 and342.5 C respectively. Thermal cycling test was applied to the materials and it was found thatDTA and DOA are both found stable after 1000 times accelerated thermal cyclings. Accordingto the results obtained, DTA and DOA with high energy storage capacity are promising to beused as new solid-liquid PCMs in thermal energy storage applications for medium temperatureapplications.