Energy and exergy analysis of solar stills with micro/nano particles: A comparative study

In this paper, a theoretical comparative study between modified solar stills (MSSs) and classical solar still (CSS) was carried out, based on the productivity and the thermal properties. The MSSs contain brackish water mixed with either graphite or copper oxide (CuO) micro/nano particles. Cost estimations of solar still desalination by using micro/nano particles was estimated. exergy destruction in various components of the solar still (SS) were calculated, analyzed and discussed. The exergy loss during the day time comprises the exergy destruction in the main components of the SS like basin plate, brine water, glazier plate and insulation material. The hourly convective, evaporative and radiative heat transfer coefficients (HTCs) with and without micro/nano particles were determined. The exergy destruction in various components of the SS have been analyzed and a solution was suggested. Results revealed that the exergy of evaporation, energy efficiency and exergy efficiency of MSSs were higher than that of the classical one. The daytime energy efficiencies of MSSs with graphite and CuO were 41.18% and 38.61%, respectively, but for the CSS was only 29.17%. The diurnal productivity of the MSSs was increased by 41.18% and 32.35% for graphite and CuO, respectively, compared with CSS. Moreover, the diurnal exergy efficiencies of MSSs were 4.32% and 3.78% for graphite and CuO respectively, while exergy efficiency for CSS was 2.63%. Furthermore, the costs of water production were found to be approximately 0.20, 0.21 and 0.24 RMB/L (1 RMB = 0.15 US $) when using MSS with CuO, MSS with graphite and CSS, respectively.