The total fixed cost of modified basin solar still, when applying vacuum fan only, is about F = 140
$. Assume the expected still life 10 years. Assume the variable cost V equals 0.3 F per year, then C =
140 + 0.3 × 140 × 10 = 560 $ where the minimum average daily productivity can be estimated 4.0
l/day. The total productivity during the still life = 4x10x340=13600 l. Cost of litter from modified still
= 560/ 13600 = 0.041 $. When the nanomaterial is used in the modified basin still with providing
vacuum; F = 260 $, V equals 0.3 F per year, then C = 260 + 0.3 × 260 × 10 = 1040 $ where the
minimum average daily productivity can be estimated 6 l/day, Assume still operate 340 days in the
year. The total productivity during the still life = 20400 l. Cost of litter from the modified still = 1040/
20400 = 0.05 $.