Solar heat basic question?

[Clik]

Pole Barn: No Insulation on Walls: When the sun shines on my south facing facing bare metal walls they get fairly warm on the inside. I try to capitalize on that free heat by blowing fans on those walls when they are warm but I'm not always there to turn the fans on and of at just the right times.

Is there a cheap sensor that could be stuck to the metal that would simply open and close a 120V circuit as the metal warms or cools?

 

[Shiftless]

Seems to me that a thermostat meant to control an air conditioner would close a switch when it got warm and open the switch when the cool set temperature is met.
You will most probably need a relay because I don't think you can find an AirCon thermostat that takes line voltage.

Anybody else have a better idea?

 

[walrus]

Anybody else have a better idea?

Yeah, why waste your money, I'll bet you don't get enough energy to offset the electricity used by the fan.

if you insist on throwing money away
http://www.zoro.com/dayton-line-vol...grznbY014ddIP08HMXhJ4hoCaivw_wcB&gclsrc=aw.ds

 

[Clik]

Yeah, why waste your money, I'll bet you don't get enough energy to offset the electricity used by the fan.

The reason is that raising the temp a few degrees keeps condensate off things and prevents rust. Air circulation is needed anyway so what is inefficient about picking up some free heat when fans would be running anyway?

 

[walrus]

Yeah, why waste your money, I'll bet you don't get enough energy to offset the electricity used by the fan.

The reason is that raising the temp a few degrees keeps condensate off things and prevents rust. Air circulation is needed anyway so what is inefficient about picking up some free heat when fans would be running anyway?

If you have to run a fan anyway I guess there is no harm.

 

[Squankum]

You could aim for "almost free" fan operation by rigging the fans up to solar panels. Of course, the panels aren't free up front, but in the long run, they pay for themselves. How much panel for how much fan, of course, is a good question. But a solar panel is also your sunlight sensor, and wouldn't fan speed increase with the strength of the sun? Kinda neat.


I keep a box fan running 24/7 in my shop (low speed) to keep air circulating in my shop to fight mildew, and by duct taping a quality furnace filter to it, fight dust, too:

http://www.garagejournal.com/forum/showpost.php?p=3244586&postcount=19

This GJ member built a solar wall:
http://www.garagejournal.com/forum/showthread.php?t=224095

I think I saw another guy on GJ in Canada who did something similar with his southern wall, black paint, whole wall, air ducts, double layer, etc etc.

There are passive versions of things like that that thermosiphon their own air, no fan required. (But a fan can still help, I think.)

The Complete Handbook of Solar Air Heating Systems
http://www.amazon.com/gp/product/1603220232/?tag=atomicindus08-20

 

[Squankum]

Hmmm... you could paint that south wall black... but then cover it with something in the summer. Maybe put some false wall inside the wall and have push air through from low input to high exit.

 

[jives]

If it warms that much, it may be worthwhile to set up some sort of solar air heater. Google search, e.g.,

http://www.builditsolar.com/Experimental/PopCanVsScreen/PopCanVsScreen.htm

http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm

Of course, this is much more involved, but could be worth looking into.

 

[Clik]

Good idea there Squankum with the box fan filter thing.

 

[HOTFR8]

What about a plug in time switch for the fan ? Just set the times you want it on and off.

 

[dfiler2]

Here is a surface mount thermostat that would probably work, have you checked to see what kind of temp the surface reaches? this unit is would open/close at 100 degrees which would probably happen pretty early in the day.

 

[2011laramie]

http://www.comstatinc.com/close-rise-snap-disc-p-736-l-en.html

snap disc, closes the circuit when it gets hot, opens when it cools off.