Theoretical and experimental investigations of inclined solar still using secondary reflectors on east-west for enhanced distillate yield

Abstract

An experimental study is conducted to observe the effect of flat secondary reflectors over inclined solar still with partitions. The inclined solar still prototype considered for the present study consists of 10 partitions with a total capacity of 35 kg feedwater and an aperture area of 1.32 m2. The authors have also developed an inhouse optical and mathematical models to determine non-uniform ray concentration and productivity from unit and validated the same with experimental investigations. The performance analysis is carried out for the ambient conditions and varying solar irradiation of Chennai (12.99°N, 80.24°E), India. The conditions of concentration, shadowing and neither concentration nor shadowing using reflectors for varying reflector angles and sun path are determined and considered. The thermal efficiency of the unit is observed as 39.81% for non-concentrating still, whereas 30.49%, 26.39%, 23.22% and 21.34% for concentrating still with 110°, 120°, 130°, 140° reflector angles. The determined optimum reflector angles for east–west reflectors from modelling are θm,E = 130° and θm,W = 130° respectively which were consistent with experimental findings in February. By integrating these reflectors to solar still in optimum angles, the distillate productivity has enhanced from 5.80 kg/day to 6.39 kg/day which is about 10.17% increment. The annual total radiation over still is determined as 8149.02 MJ and cumulative distillate yield is 1547.85 kg when operated for 300 clear days. Thus, the findings of this study provide strong evidence to support the practical implementation of concentrated solar stills as a viable solution for water treatment meeting demands.