Solar Ice maker?

[the.fee.fairy]

This came through on a mailing list.

I know that Nev has been working on his solar oven, so would this, in theory, work with the same thing?

<from Organic Architecture>
Parabolic night time heat sink/ one tonne solar ice maker (long)
Posted by: "Shody Ryon" qi4u
Date: Thu Apr 26, 2007 10:36 am ((PDT))

http://www.cibse.org/pdfs/development.pdf

one tonne solar ice maker


http://www.infomotions.com/etexts/gutenberg/
dirs/etext04/cookr11.htm

X. How to Use the Solar Funnel as a
Refrigerator/Cooler
A university student (Jamie Winterton) and I were the
first to demonstrate that the BYU Solar Funnel Cooker
can be used--at night --as a refrigerator. Here is
how this is done.

The Solar Funnel Cooker is set-up just as you would
during sun-light hours, with two exceptions:

1. The funnel is directed at the dark night sky. It
should not "see" any buildings or even trees. (The
thermal radiation from walls, trees, or even clouds
will diminish the cooling effect.).

2. It helps to place 2 (two) bags around the jar
instead of just one, with air spaces between the bags
and between the inner bag and the jar. HDPE and
ordinary polyethylene bags work well, since
polyethylene is nearly transparent to infrared
radiation, allowing it to escape into the "heat sink"
of the dark sky.

During the day, the sun's rays are reflected onto the
cooking vessel which becomes hot quickly. At night,
heat from the vessel is radiated outward, towards
empty space, which is very cold indeed (a "heat
sink").

As a result, the cooking vessel now becomes a small
refrigerator. We routinely achieve cooling of about 29
degrees Fahrenheit(10 degrees Celsius) below ambient
air temperature using this remarkably simple scheme.

In September 1999, we placed two funnels out in the
evening, with double-bagged jars inside. One jar was
on a block of wood and the other was suspended in the
funnel using fishing line.
The temperature that evening (in Provo, Utah) was 78
degrees Fahrenheit. Using a Radio Shack
indoor/outdoor thermometer, a BYU student (Colter
Paulson) measured the temperature inside the funnel
and outside in the open air. He found that the
temperature of the air inside the funnel dropped
quickly by about 15 degrees,
as its heat was radiated upwards in the clear sky.
That night, the minimum outdoor air temperature
measured was 47.5 degrees--but the water in both jars
had ICE. I invite others to try this, and please let
me know if you get ice at 55 or even 60 degrees
outside air temperature (minimum at night). A black
PVC container may work even better than a
black-painted jar, since PVC is a good infrared
radiator--these matters are still being studied.

I would like to see the "Funnel Refrigerator" tried in
desert climates, especially where freezing
temperatures are rarely reached. It should be
possible in this way to cheaply make ice for Hutus in
Rwanda and for aborigines in Australia, without using
any electricity or other modern "tricks." We are in
effect bringing some of the cold of space to a little
corner on earth.


let me know how you get on, if anyone tries it!

[Wombat]

wow!

Well I haven't tried that. ( the one tone ice maker is slightly higher tech than I usually tackle - not that I couldn't mind you.....)

The refrigerator funnel, without having tried it sounds like BS to me, but I would like my old Physics Professor (Muddy)'s take on it.

Maybe one day I will give it a go.

Nev

[Muddypause]

No, no, I'm no physics expert - there's tons I don't know about it. But, this does seem a little odd. I mean, why don't we just build a few of these funnels on a large scale and solve the global warming problem?

I don't really understand how they are suggesting that the heat is being lost. They seem to be saying that the funnel will radiate it directly to outer space. That's a pretty long way through the insulating blanket of atmosphere, even on a cloudless night. And in any case, once the thing has cooled to ambient temperature, how does the funnel it keep on radiating better than the rest of the atmosphere?

I'm not, at this stage, saying this wouldn't work (though I can't for the life of me think how), but I am suggesting that it doesn't work in the way they say it does. There may be some other effect happening.

But broadly, it is quite a clever trick to make something cooler than its surroundings. Heat pumps and evaporation are two well known ways. Maybe there are other ways I haven't encountered.