Enhancement of energy utilization using nanofluid in solar powered membrane distillation.

Nanofluids have excellent solar energy utilization efficiency due to the localized surface plasmon resonance phenomenon. In this study, photothermal nanofluids were employed as the feed solution for energy harvesting in solar powered membrane distillation. Ten different nanofluids were compared and TiN (titanium nitride) was chosen following UV-Vis-NIR-waveband (ultraviolet-visible-near-infrared) optical absorption analysis, zeta potential measurement, and membrane distillation flux testing. Desalination experiments were conducted using a range of TiN concentrations and solar radiation powers. The results showed that water flux and solar energy utilization efficiency increased with increasing TiN content. Compared to the base fluid (35 g/L NaCl aqueous solution), flux increased from 0.47 to 0.74 kg/(m∙h), while energy utilization efficiency improved from 32.1% to 50.5% for 100 mg/L TiN nanofluid. Flux also increased with the increasing of solar radiation power markedly. With 5 kW/m solar radiation power, the flux reached 2.77 kg/(m∙h). Furthermore, the permeate water produced was of excellent quality contained less than 10 mg/L salinity when using 35 g/L NaCl feed solution. And no nanoparticles were detected transport through the membrane during the process. The nanofluid enhanced solar powered membrane distillation represents a promising perspective for better solar energy utilization.