Abstract

In recent years, investigations and research has focused on exploring methods and finding ways to enhance solar stills efficiency and increase the production rates. In this study, experiments were carried out for 24 h during summer, autumn, and winter in order to investigate the affect of incorporating passive external condensers to a single-slope, single basin type solar still. Therefore, three identical solar stills were designed and constructed with the glass covers mounted on the stills at an inclination of 20° to the horizontal plane, with an effective area of 1 m². The first still was used for reference; the other two were connected at the back by means of pipes to passive cylindrical condensers in two different ways. One still was connected only, through the upper part of its back, while the other still was connected from both upper and lower parts of its back. The distilled (condensed) water was collected either through the condensers or by running down the inclined glass cover into a trough. It has been found that the average production rate obtained from the experiments conducted during the summer season is about 42.9% higher than that obtained during the autumn season and 117.4% higher than that obtained during the winter season. It has also been found that the still connected through the upper part only yielded an increase in its production rate of 15.1, 15.08 and 16.6% for the summer, autumn, and winter respectively in respect to the conventional simple solar still. The still connected to the condensers through its upper and lower parts yielded an increase in its production rate of 30.54, 33.6 and 35.8% for the summer, autumn and winter respectively, in respect to that produced by the conventional simple solar still. The overnight production rate was found to represent an average ratio of 10.8, 13 and 19.7% of the total daily production rate, for the summer, autumn, and winter respectively.

Key words: Solar still, solar distillation, water desalination, solar still efficiency.