Toward productivity enhancement of a stepped solar still using bio-phase change material, modified flat plate collector and nanoparticles

A stepped solar still having an aluminum stepped basin cum container filled with a uniform layer of beeswax (a bio-phase change material) coupled with a modified flat plate collector (beeswax-loaded system) was tested for flow optimization and productivity enhancement. The experiments were performed at 20, 30 and 40 ml/min water flow rates. The designed setup gave a yield of 3.98 kg/m(2) (maximum) at 30 ml/min. Further investigation was performed on this system by dispersing 0.5% w/w aluminum nanoparticles in beeswax (nanodispersed beeswax system) for 30 ml/min water flow rate. The productivity and energy and exergy efficiencies of nanodispersed beeswax system were enhanced by 8.79%, 12.42% and 17.58%, respectively. The annual energy output, CO2 mitigation and carbon credit earned by this system were 8.79%, 9.17% and 9.18%, respectively, higher than the beeswax-loaded system. Due to increased distillate output, nanodispersed beeswax system has lower energy payback time than the beeswax-loaded system. The annual productive cost and payback period of nanodispersed system were $183.0/ year and 513.67 days, respectively.