Ionic Liquids for Application as Heat Transfer Fluids for Solar Thermal Energy

The feasibility of using ionic liquids (ILs) in solar thermal power plants as heat transfer fluids (HTFs) and liquid thermal storage media has been investigated. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), viscometry, and other pertinent techniques were used to synthesize and thoroughly characterize a number of IL variants, including [C4min][PF6 ], [C8mim][PF6 ], [C4min][bistrifluoromethane sulflonimide], [C4min][BF4 ], and [C4min][bistrifluoromethane sulflonimide]. Important parameters were carefully determined, including density, heat capacity, viscosity, melting point, decomposition temperature, and thermal expansion coefficient. To evaluate the thermophysical properties of basal ILs and nanoparticle-enhanced ILs (NEILs), experiments were carried out. Because solar thermal energy (STE) is more effective than photovoltaic solar cells, energy researchers have been paying close attention to it lately. Heat transfer fluids (HTFs), a secondary medium, are used in STE to transport heat. As such, the thermophysical characteristics and thermal behaviour of the HTFs determine the overall performance of STE systems. High melting point, high decomposition temperature, and high vapor pressure are problems for conventional HTFs. To overcome these constraints, scientists have started working on creating new HTFs specifically designed for STE applications. Because of their improved thermophysical characteristics, such as their strong ionic conductivity, low vapor pressure, and thermal stability at high temperatures, ionic liquids (ILs) have become intriguing candidates for the next generation of HTFs. Moreover, adding nanoparticles to ILs can improve their thermophysical characteristics and thermal performance even more. This is a rapidly developing field of study that aims to increase the effectiveness of solar thermal systems. An overview of recent studies using IL-based nanofluids as HTFs is also given in this study.

Keywords: Heat transfer fluids (HTFs), Ionic liquids (ILs), Solar thermal energy (STE), Thermophysical properties.