Experimental study of thermal performance enhancement of molten salt nanomaterials

Concentrating solar power (CSP) plants are one of the maintechnologies harvesting solar energy indirectly. In CSP systems,solar radiant light is concentrated into a focal receiver, whereheat transfer fluid (HTF) as the energy carrier absorbs solarradiation. Thermal energy storage (TES) is the key method toexpand operational time of CSP plants. Consequently, thermophysical properties of the HTF is an important factor intransferring thermal energy. One of the promising chemicals forthis purpose is a mixture of molten salts with stable properties atelevated temperatures. However, low thermal properties ofmolten salts, such as specific heat capacity (cp) around 1.5kJ/kg°C, constrain thermal performance of CSP systems.Recently, many studies have been conducted to overcome thisshortcoming, by adding minute concentration of nanoparticles.In this work, the selected molten salt eutectic is a mixture ofLiNO3-NaNO3 by composition of 54:46 mol. % plus dispersingSilicon Dioxide (SiO2) nanoparticles with 10nm particle size.The results from the measured specific heat capacity bymodulated differential scanning calorimeter (MDSC) shows a9% cp enhancement. Moreover, the viscosity of the mixture ismeasured by a rheometer and the results show that the viscosityof molten salt samples increases by 27% and this may result inincreasing the pumping energy of the HTF. Consequently, overallthermal performance of the selected mixture is investigated byfigure of merit (FOM) analysis. The interesting results show an enhancement of the thermal storage of this mixture disregardwith the viscosity increase effect.