I thought of a normal glass pannel covering a plastic bowl or plate. The heat will evaporate water (even bore well water of Chennai is equivlane to sea water) and the condensed water can be used for drinking.
While browsing an useful link on the said subject reflecting the same idea link given below for better understanding. It gives a do it yourself kit mo
A solar power photoelectric convertor by a Japanase guy is mind boggling looks to be directly from Sci-fi movie. A small floating device (just like in movie) draws energy from and by simple capilary rise make water potable (drinkable).
A more interesting topic is that if you keep three glass layers the temperature can go as high as 100 deg C the boiling point of water. An mexican company has done a home base model which uses water used for cleaning from kitchen and bath to get water. The sun light evaporates the water and gives artificial rain which is collected for use. see the link below.
Some more nice workable models are given in the below link.