Thermal properties of phase change materials ionic liquid/fatty acids for thermal energy storage applications

Abstract

Researchers have developed advanced energy storage techniques in response to the depletion of energy resources and the escalation of environmental problems caused by increasing population and technological advancements. One of the most promising methods to overcome such issues is the latent heat thermal energy storage (TES) method, which employs phase change materials (PCMs). TES using PCMs are an important category of novel materials that significantly contribute to the efficient use and conservation of solar energy and wasted heat. This work presents a new family of PCMs based on ionic liquid (IL) tris(2-hydroxyethylammonium) formate and fatty acids for the first time that operate in the temperature range of 50–150 °C and offer a safe and inexpensive capacity. Good chemical and thermal stability, low flammability, and low volatility along with the potential to tune chemical and phase properties provide an inherent “green” property for ILs that is well suited to PCMs. Using PCM3, tris(2-hydroxyethylammonium) formate/stearic acid, we demonstrate effective latent heat 246 J·g−1. The results of differential scanning calorimetry analysis show that the PCM2 tris(2-hydroxyethylammonium) formate/palmitic acid has a higher heat capacity 8.194 J·g−1·K−1 at the melting point than the other two PCMs due to its small alkyl chain. Thermal stability analyses show the maximum stability (98 %) for PCM3. Additionally, based on the structure of these PCMs, this study explores the molecular basis for the high thermal energy storage capacity of these materials and highlights the significance of hydrogen bonds in PCM performance. Using simple, cost-effective materials, this method gets around the complexity and expense of composite PCMs. We present design recommendations for implementing our approach in the management of thermal energy storage applications.