State-of-the-art ionic liquid & ionanofluids incorporated with advanced nanomaterials for solar energy applications

Ionic liquids are liquid salts that are composed entirely of ions having melting points lower than 100 °C. Ionic Liquid possesses some salient properties like low melting point, negligible vapor pressure, and elevated thermal stability, making them a potential candidate as a working fluid for solar energy systems. Ionanofluid is formulated by incorporating nanomaterials in Ionic Liquid, which tunes the Ionic Liquid's thermophysical, optical, and energy storage properties and allows them more reliable as a medium for energy storage and heat transfer fluids for solar systems. This current review deals with the applicability of Ionic liquids, Ionanofluids in solar systems together with the role of some advanced nanomaterials to meet the permissible properties. Energy storage capability (sensible and latent), optical properties (absorbance, transmittance, molar extinction coefficient), together with thermal stability, thermal conductivity, and viscosity are assessed. The effects of anion/cation variations on these properties are discussed. The applications of Ionic Liquids and Ionanofluids in different solar systems have been critically reviewed together with recent advances of nanoparticles in the solar energy system. Outstanding sensible energy storage properties of Ionanofluids together with improved thermophysical properties are the significant findings of this present review. Finally, the existing challenges that require to be overcome for the successful implementation in the real case are also brought to light.