2Research and Development Cell, SRM University, Lucknow, India
Abstract
The solar stills were developed to fulfil the freshwater need of the growing population. The paper presents the recent modifications made in still to improve their productivity like the application of phase change materials (PCM), connecting flat-plate collector (FPC), use of nanoparticles, stepped solar still, and attaching separate condenser in the still. Active solar stills are found more productive than passive ones and the thermal efficiency of active solar stills lie in the range of 50–70%, which is far better than passive still having 20–55% thermal efficiency. According to the literature studied in the paper, the maximum productivity of active solar still is 10 litres per day and in passive solar stills, it is 6 litres per day. The different approaches used to carry out the heat and mass transfer analysis of single and double slope active and passive solar stills are also discussed in the paper.