Desalination 242 (2009) 205–214 0011-9164/09/$– See front matter © 200 Elsevier B.V. Effect of inclination of external reflector of basin type still in summer Hiroshi Tanaka Mechanical Engineering Department, Kurume National College of Technology, Komorino, Kurume, Fukuoka 830-8555, Japan Tel. +81 (942) 359359; Fax +81 (942) 359321; email: tanakad@kurume-nct.ac.jp Received 12 December 2007; accepted 15 April 2008 Abstract In this paper, we present a geometrical model to calculate the radiation reflected from an external reflector inclined backwards and then absorbed onto a basin liner of a basin type still. The effect of the inclination of the external reflector on the distillate productivity of the still with both the internal and external flat plate reflector on a summer solstice day at 30°N was theoretically predicted. We found that the distillate productivity of the still can be increased by inclining the external reflector even in summer, but the augmentation is smaller than in winter. Further, the benefit of both the internal and the inclined external reflectors of the basin type still would be considerably less in summer than in winter. Keywords: Solar still; Solar desalination; Solar distillation; Basin; Inclined reflector; Summer 1. Introduction Internal and external reflectors can increase the distillate productivity of a basin type still as indi- cated by many researchers [1–6]. El-Swify and Metias [4] and Tripathi and Tiwari [5] presented geometrical models to evaluate the effect of in- ternal reflectors on the distillate productivity of a basin type still. In addition to this research, we have presented a geometrical model to calculate the reflected radiation from an external vertical flat plate reflector and then absorbed onto a basin liner [7]. As a result, we found that the external vertical reflector can remarkably increase the dis- tillate productivity of the basin type still during the spring and autumn seasons. But during the summer and winter seasons, the effect of the ex- ternal vertical reflector would be small or even negligible. Therefore, the arrangement of the ex- ternal flat plate reflector has to be changed from vertical in these seasons. In winter, the distillate productivity of the ba- sin type still may be increased by inclining the flat plate reflector slightly forwards since the al- titude angle of the sun becomes low and a con- siderable amount of the radiation reflected from doi:10.1016/j.desal.2008.0 .00 4 7 8 All rights reserved.