Nanocomposite produced by dispersing nano CuO in solar salt: An investigation about enhancement of thermophysical properties in solar energy storage application

Solar salt (SS), serving as both a thermal energy storage (TES) material and heat transfer fluid (HTF), plays a critical role in determining the overall efficiency of concentrating solar power (CSP) plants through its thermophysical properties. Thus, a high-temperature static melting method and ultrasonic aqueous solution method was used to prepare nano CuO-SS nanocomposites for investigating the thermal properties improvement of SS by two different particle sizes of nano CuO (40 nm and 100 nm). The liquid specific heat capacity (c p ) appeared a trend of first increasing and then decreasing with the addition of nano CuO. It was 1.99 J/(g·K) and 1.81 J/(g·K) when the two nano CuO content was both 1.5 wt% in two system, and there was an increase of 28.39 % (nanocomposite CuO1-SS-4 of CuO1-SS system, Cu1SS-4) and 16.77 % (nanocomposite of CuO2-SS system, Cu2SS-4) compared with the pure SS respectively. The nanocomposites Cu1SS-4/Cu2SS-4 maintained excellent thermal stability, showing no change in their working temperature range compared to pure SS. The uniform dispersion of nano CuO particles was confirmed through scanning electron microscopy (SEM) characterization. The superior heat storage capacity results from the greater surface area and higher surface energy of smaller nano CuO, which facilitated more efficient thermal energy storage in the system. It had increasement of 47.25 % and 56.04 % about thermal conductivity of nanocomposite Cu1SS-4 and Cu2SS-4. The nitrate-based nanocomposite as a promising candidate material for thermal energy storage, due to its high heat storage, excellent chemical compatibility, large suitable working temperature and high thermal stability.