Why Manhattan? Arizona, or maybe Death Valley would be proper locations for solar-powered stills. I've seen a solar powered kitchen range: aluminum mirror about 6 feet in diameter, with three metal rods forming a sort of a tripod - and on that tripod a kettle was hung. On a regular 90 F day the water in that teakettle was brought to boiling surprizingly fast, something like 20 minutes, IIRC.
surprizingly=surprisingly. Adjacent key typo.