Fig (4) indicated that increasing the glass cover thickness
from 2 mm, to 4 mm and 6 mm, increased significantly the
distillation output percentage, in the same order as the 6 mm
glass cover thickness gave the highest distillation output
percentage. This could be due to the heat loss in .6 mm
thickness which is less than that of 4 or 2 mm, since it
represents a high thermal resistance as compared to the other
thickness. This could be explained as the input quantity of
heat to 2 mm, 4 mm and 6 mm glass thickness are equally,
this due to the approximately equally, this due to the
approximately equally of transmittance and absorptance