We noted in the original report that the funnel works as a cooler at
night, by reflecting heat out of the canning jar and up to the cold
sky. We have found that this works during the day also, when the
funnel is pointed to a region of the sky away from the sun (and
buildings, etc.). We found cooling of about 12 degrees F., compared
with about 20 degrees cooling at night. To achieve this, the jar was
placed on a rabbit-wire support as described above, and housed in
two cheap, clear polyethylene bags, such as used for vegetables in
the United States.
Hot-and-cold running water.
By placing a large funnel around a water barrel, it will be
solar-heated during the day, or cooled at night. Thus, having two
barrels each with a funnel-like reflector around it, and covering
one when not sunny and the other whenever it is sunny, one can have
hot and cold water. These barrels could be placed on a platform or
roof to provide hot-and-cold running water!