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Old 05-26-11, 09:32 AM   #1
vmike
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Default Thoughts on Solar Cooling

This is not exactly solar heating, but looked like a good place to discuss this. Background; I've been playing with solar hot water heating systems for many years. My house is retrofit solar heated since 1987, with only a wood stove for back up. The house is 2750 square feet, to make this more dramatic. Over the years I've collected a number of pieces of water source heat pump stuff to experiment with, which has stimulated an idea that I first toyed with in the 70s when I started this solar heat adventure.

So, I'm throwing out the idea for cussing and discussing.

What I've been thinking about is placing an unglazed set of collectors to face the north sky to collect the cold at night, to be stored for daytime cooling use. I, years ago did the experiment of putting a thin film of water on a black painted cookie sheet at night and freezing the water when the ambient air temp was above 60 degrees. I figure if I could store enough cold to greatly improve the water source air conditioner, it'd be cheaper than drilling wells or digging trenches. Or even putting hundreds of feet of plastic tubing in the creek I have on the property. This would also be much easier for the in town experimenters to pursue.

I plan to build this up in the near future, I deliberately oriented one of the buildings on the new place with a north facing roof with this in mind. I not certain that the cold collecting water panels would have to have any particular angle, just a clear view of the night sky. The reason for my north facing thoughts was to keep the daily panel heating as low as possible.

Anyway, sorry for the rambling, I think much faster than I can compose this.

What think?

mike

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Old 05-27-11, 12:53 AM   #2
Ryland
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It should work just fine, only thing I can see is that by having them face north you double your cost in panels, altho you are right that they will stay cooler in the day time I have to wonder how fast they will cool off at night.
Also, altho they are not common yet, there is a blue coating that is now being used more and more with solar hot water panels, it absorbs heat but does not give off heat as well, so it would not give up the heat if used in this way, I've only seen it in the testing phase a year or so ago, but they said it was going to be put in to use.
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Old 05-28-11, 03:28 PM   #3
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I would go the high water volume and stupid simple approach: just pump the water to the top of your roof's north slope and recollect it at the bottom during the night. I dont see any significant advantage that all the panel equipment would provide, so just eliminate it all together. As long as the roof is a good enough heat conductor, and the nights are cool I dont think evaporation losses will be significant. just my $0.02.
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Old 05-28-11, 09:08 PM   #4
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Unless your roof is black you will not dump as much heat in to the sky as a solar hot water panel would with it's black face, because you are trying to radiate that heat out in to the sky so the darker surface will work better.
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Old 06-02-11, 04:23 PM   #5
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Or you could build a solar thermal powered absorption chiller - Solar Thermal Panels and Absorption Chiller. That might be a better way to use the "extra" solar hot water you have in the summer.

FWIW,
Tim
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Old 06-03-11, 08:44 AM   #6
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I tried the absorption chiller experiments in the late 70s. The panels I was using at the time would only give me 250 degrees of temp on a good sun day. No where near what the gas flame put into the regenerator. I put a circulation pump in the ammonia refrigeration circuit, which made the chiller actually work, sort of. About ten years ago I made up a mirrored 4' dish with a boiler at the focal point and circulated hot motor oil to a modified heat generator on a camper fridge. The unit cooled well and made ice. I have in inventory a 4 ton gas absorption water chiller and a 10' dish and some aircraft aluminum skin set aside to try this on a building sized experiment. One of these days.

I dug around and came up with a pump, unglazed solar panel, a water tank and a small fan and coil water to air heat exchanger to put together to take some measurements of how much heat I can sink. I've always had this vision of freezing a ball of ice in the winter and cooling from it in summer and I keep thinking with a water source heat pump I can do this.

Probably put this together after I get my wind spinners back up and finish the refurb of my PV power systems.

Too many toys, too little time!

mike
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Old 06-04-11, 10:45 AM   #7
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Quote:
Originally Posted by vmike View Post
I tried the absorption chiller experiments in the late 70s...
Do you have any photos from this historical experiment?

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Old 06-04-11, 08:18 PM   #8
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store enough cold

that phrase alone is enough to give the engineer in me shivvers..!

If you think along the line of radiating water stored heat to space vs. 'store..cold' you may have some epiphany insights??

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