Nanofluids application in direct absorption solar collectors: review and numerical model

The application of nanofluids has the potential to solve technical key issues in many solar thermal engineering systems. Recent literature indicates that nanofluids offer unique advantages over conventional fluids. Nanofluids are made of solid nanoparticles suspended in a liquid. These particles enhance optical properties of the liquid suspension, increasing the efficiency in the conversion of solar radiation into thermal energy. This study investigates the application and challenges of nanofluids in solar energy systems. The main literature on numerical models of nanofluids in solar thermal energy is here presented. In particular, the attention has been focused on nanofluid-based direct absorption solar collectors (DASC). Based on this review, a new model of a nanofluid-based direct absorption solar receiver for a concentrating solar collector has been proposed and then applied to predict the performance of a receiver with single-wall carbon nanohorns aqueous suspension.