Reverse Osmosis and Other Treatment Technologies - Global Drinking Water Management and Conservation - page 59

Fig. 4.7 Flowdiagramof amultiple effect distillation system (California Coastal Commission 1993 )
Fig. 4.8 Flow diagram of a vapor compression system (California Coastal Commission 1993 )
in Fig. 4.9 , solar radiation provides the energy to turn the raw water into steam. Once
the water enters a gaseous state it rises and collects at the top of the glass or plastic
barrier. The steam then cools, condenses, and is collected as freshwater.
In the past, solar stills produced only 6 l of freshwater per square meter per day
of collector surface (Kunze 2001 ). This would mean that approximately 3.78 mil-
lion square meters of collector surface would be required to match the modest
production capacity of the Sand City six mega-gallon-a-day desalination facility.
Since space of this magnitude is rarely available, solar stills are a poor choice for
large-scale freshwater production. Even with modern advances in heat recovery and