I don't have any concrete numbers at present, but design considerations alone can present challenges. For example, what is the world's largest greenhouse in terms of floor area and in terms of overall volume (a solar still essentially needs a design similar to a greenhouse, especially on the ceiling)? Second, how well will a batch process with labor-intensive between-batch cleanup (a solar still needs to be periodically cleared of its deposited minerals, which don't just include salt) work against a more-or-less-continuous demand for clean water (not just among farmers, but also among a sprawling metropolis like Los Angeles which basically never sleeps)? Third, just how much sunlight will you need to evaporate X gallons of water? For a frame of reference, near Los Angeles is the world's largest solar-thermal energy plant in the world, the Ivanpah Solar Power Facility. It generates 392MW (e or t, no one says) over a span of some 1400+ ha. Sounds like a lot until you realize they say this'll power about 100,000 homes. Los Angeles County alone has over ten million homes according to the 2010 US Census. Oh, and BTW, what about the energy needed to move all this water and waste to and from the desert (and please note, most of California's desert is actually elevated several hundred feet—in comparison Death Valley and the Salton Sea are pretty small areas—which means you'll be pumping seawater uphill)?
Biting the hand that feeds IT
