the most straightforward approach is to use a basin solar still (figure 6.8). this is an internally blackened basin contraining a shallow depth of impure water. over this is a transparent, vapour-tight cover that completely encloses the space above the basin. the cover is sloped towards the collection channel. in operation, solar radiation passes through the cover and warms the water, some of which then evaporaters. the water vapour diffuses and moves convectively upwords, where it condenses on the cooler cover. ther condensed drops of water then slie down the cover into the cathment trouht.
example 6.4 show the substantial areas of glass are required to produce enough fresh water for even a mall community.