Solar thermal energy conversion is gaining more attention among researchers due to the recent development in nanofluids and molten salt technology. Among various solar collectors, parabolic trough collector has received significant attention from researchers due to their operating temperature range (60-240 °C) feasible for power generation. Parabolic trough collector is currently having a higher number of installations compared to other concentrated solar power technology around the globe. Most of the conventional heat transfer fluid used in PTC has poor heat transfer and light to heat conversion properties. Therefore, it is advantageous to enhance the thermophysical properties of heat transfer fluid to improve the overall efficiency of the system. Well-engineered nano-enhanced heat transfer fluid is advantageous because a very low mass fraction of nanoparticles bring considerable enhancement in thermophysical properties. This paper focuses on the most recent advancement in heat transfer fluids, their preparation, and stability issues when doped with nanoparticles. Various heat transfer fluids currently used in parabolic trough collectors and the nano-enhanced heat transfer fluids having the properties better than conventional heat transfer fluids are compared and their preparation methods and properties are discussed.Enhancement of thermophysical properties of molten salts by doping nanoparticles and their enhancement in thermal stability at high temperature, the possibility of using mono and hybrid nanofluid, ionic liquids, gaseous heat transfer fluid, and vegetable oil as the heat transfer fluid in parabolic trough collectors are the key highlights of this review.

Energy storage is a global critical issue and important area of research as most of the renewable sources of energy are intermittent. In this research work, recently emerged inorganic nanomaterial (MXene) is used for the first time with paraffin wax as a phase change material (PCM) to improve its thermo-physical properties. This paper focuses on preparation, characterization, thermal properties and thermal stability of new class of nanocomposites induced with MXene nanoparticles in three different concentrations. Acquired absorbance (UV-Vis) for nanocomposite with loading concentration of 0.3 wt.% of MXene achieved ~39% enhancement in comparison with the pure paraffin wax. Thermal conductivity measurement for nanocomposites in a solid state is performed using a KD2 PRO decagon. The specific heat capacity (c p ) of PCM based MXene is improved by introducing MXene. The improvement of c p is found to be 43% with 0.3 wt.% of MXene loaded in PCM. The highest thermal conductivity increment is found to be 16% at 0.3 wt.% concentration of MXene in PCM. Decomposition temperature of this new class of nanocomposite with 0.3 wt.% mass fraction is increased by ~6%. This improvement is beneficial in thermal energy storage and heat transfer applications.

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