Jones Beene wrote:
No, not a misspell of 'dessert ice' (not this time anyway)...
Poser-of-the-Day: Can anyone imagine making real ice, as in
solid-water ice, but in the desert, using zero electricity and only
natural forces?
Yes I have data on that technology its quite simple and was used to make
Ice in the middle east for centuries. The design described by Jones
below is a bit complex but will work but there is a simpler way. Some
middle eastern houses have a very shallow pond, 1 cm, placed between
narrow walls 1-2 meters tall and 1 meter wide. The walls run east west
so the pond is in shade for most of the day. Shade cloths are sometimes
pulled across to help shade the ground by day. *The ground stays
cold.* The heat from the water is radiated straight up into the night
sky. The Ice must be collected before dawn. It is still used today in
some villages but who wants to get up at 4 am to harvest ice? Its not
competing with powered refrigeration where energy technologies exist.
Production varies, 250 g to 5kg per square meter.
Some air well designs also produce ice and refrigeration. These are
white bricks staked in an open pattern so there is a free flow of air
but the bricks below become perfectly shaded. The upper bricks heat and
cool quickly because on the low contact surface area and high air
circulation. The lower bricks chill at night but because they are always
shaded and are below the hight of the outer wall so there is no hot
winds effecting them. Water condenses on the chilled bricks and runns
down into the cictern below. This water is cold enough to produce
Icicles in the cistern below.
Several animal species build small airwells.
The question arose out of this interesting thread on Slashdot, based
on a recent
Time Magazine article, telling us how Dave Williams is trying to make
ice for third-world applications using the Hilsch-Ranque vortex-tube
effect. As all on Vo know - this mechanical device was developed in
1930 by G.J. Ranque, using swirling air in a tube, such that the
counter-rotating vector components split the air stream into hot and
cold components.
Well, lo-and-behold, as it turns out: It is possible that the ancient
Egyptians did something even more remarkable, without a vortex tube.
If you build a solar reflector, and employ it at night, especially in
a dry environment, the items inside a reversed focal point can be
induced to become very cold, and can attain temperatures below
freezing, even if the previous day-time temp was 120 - since desert
nights can be quite chilly.
And that is a further interesting prospect of having a solar farm. Use
the solar concentrators at night to create cold water and store it for
air conditioning. I wonder how quick I can get this idea to the patent
office?
