This work reports a new design of solar still with a hemispherical top cover for water desalination with and without flowing water over the cover. The daily distillate output of the system is increased by lowering the temperature of the cover by water flowing over it. The fresh water production performance of this new still was observed in Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore (11 degrees North, 77 degrees East), India. The efficiency was 34%, and increased to 42% with the top cover cooling effect. Diurnal variations of a few important parameters were observed during field experiments such as water temperature, cover temperature, air temperature, ambient temperature and distillate output. Solar radiation incident on a solar still is also discussed here. (C) 2011 Elsevier B.V. All rights reserved.