Solar heated shop?

[ironhat]

I'd like to implement a simple solar collector into my 20" window but after a couple of fruitless hours of online searching I'm ready to go with my gut and failing memory. As I recall, a simple box 4" deep and 20" wide (in my application) by ?? feet long with a baffleplate dividing the 4" dimension in half with an opening at the bottom for the heated air to circulate the cooler air drawn in at the window end should work. Besides insulation and black interior, is there anything I'm forgetting? With the prices of fossil fuels going through the roof I want a little assist and a woodstove is out of the question for space reasons.
TIA,
Chiz

[LCHIEN]

according to Wikipedia solar energy density is 1020w/ sq meter
at the equator, sea level.

So with a 20x20 window (you only gave one dimension so I assumed it was square) you would have available a maximum of 268 watts.

THis assumes that the sun is at perfect right angles to the collector. The energy is further reduced by sin(compound incident angle) at which the sun strikes the collector.

That implies:
For an unobstructed, side mounted window facing due south at a mid-latitude location and mid-year, you will get a maximum of 189 watts at noon, and much less in the evening and morning when the sun is to the right or left, falling to zero at dawn and dusk.

Considering that most solar capture schemes are only at very best 20% efficient you'll probably get an average of 5-10 watts during the daytime.

[Thom2]

IOW: Loring doesn't think it'll do much to heat your shop


Thom
plain english translator [)]

[dlminehart]

For solar heating of spaces, people generally use an entire wall rather than merely a window. E.g., a glass wall with floor-to-ceiling black barrels full of water inside it, with a second pane of glass about 6 inches inside of the first. During the day, the sunlight heats the barrels of water. At night, foam beads are blown in to insulate the space between the windows, and the heat radiates into the interior space. In the morning, a vacuum sucks the foam beads out so the sun can again shine in.

Other walls and ceiling must be super-insulated for this to be of much use.

[PoolQ]

Perhaps I can provide some information based on what is attached to the roof of my computer room.

From the big box:
1 foam panel 2x8 or what ever the standard is, foil covered 1" thick
2 fence rails with the channel dado'd down the center
2 metal corrigated awning panels, not the fiberglass ones
2 large foam pipe insulators, the ones that are split to put around copper pipe
1 low CFM fan (75 cfm or so)

Put the fence rails on each long end of the foam panel
brad in some scrap strips between the channels and across the back of the foam to hold it in place

overlap the metal panels to fill up the front of the foam, between the rails

calk it down and seal it good

open the foam pipe insulation and put it over each short end of the foam and metal pannels

calk it

plug one end of each side

this will form the solar panel, the fan takes room air and blows it into one foam pipe insulator, through the metal/foam panel and into the other foam pipe insulator, then back into your shop.

moderate climate here, if the suns out one panel gets it uncomfortably warm in here. mid 80's. does not heat fast and i run it from sun up to sun down.

normal insulation in the room and no snow outside.

I got the idea from this place

http://www.solarwall.com/

[ironhat]

Thanks folks. The link is hlpful, poolq. And LCHIEN, the window is 42" high - sorry 'bout that - and I was thinking of a flat, baffled collector which would convect air from inside the shop, to the bottom chamber of the panel while the top chamber heated up and convected the warm air into the shop. I know that I saw a slew of these back in the 70's but I;ll be hanged if i can come up with one now. I think I'll experiment a bit. I'm just looking for an assist from a unit. Not full out heating capability.
Thanks again,
Chiz

[Tom Miller]

I think after this winter there will be another slew of information available re:solar (and any other alternative) heat. [:0]

Regards,
Tom

[ironhat]

I'm bettin' you're right, Tom!

[ironhat]

Just a follow-up. Here's the unit I was trying so poorly to describe. Apparently, it's a thermo-siphon. I;m still thinking that the baffle should be metal so that it heats up quickly and transfers heat better than wood. http://www.jrwhipple.com/sr/solheater.html

[SteveR]

Iron, IMHO, agree on the metal, makes sense. If you build one please advise as to how it works...I am very interested.
Steve

[ironhat]

Steve,
The only issue I see with a metal baffle is that the incoming air on the underside may prematurely cool it and actually slow the siphoning effect. Perhaps a foamboard underlayment would help. Any thoughts on that?
Later,
Chiz

[SteveR]

Chaz,
After rereading that link you have..
I think the author had his designed so the metal piece (aluminum for his) was mounted 3/4" above the thin insulation panel, so the thin insulation panel may help dissipate heat transfer into the cold air space feed? So this may help eliminate the issue you brought up. I was going to suggest placing the metal 2" down creating 2-2" equal warm air spaces above the thin insulation piece..but his way may be better?

So if I understand his setup correctly, described from the top glass down......top glass, 3.25" warm air space, thin metal panel painted black, 3/4" warm air space, thin insulation panel, 4" cold air space then another thick insulation piece. I do not understand the purpose of the thick insulation piece on the bottom (unless to keep the cold air cold, but if it cold outside anyway why?) nor why lining the cold side with aluminum foil??? On that same site the guy had some solar ovens with "wings" to help focus the rays....interesting.

For the thin piece I think Borg or lowes sells a polystyrene material, try to use the blue or pink instead of the white...It is a bit more rigid and has a better R/inch value.

I think this design could be made a bit more aggressive (efficient maybe the correct word) with the addition of a small sized fan like PoolQ did? PoolQ, you by chance have a section sketch?

open to ideas,
Steve

[ironhat]

I like your ideas, Steve. The only problem I see with a fan is neeing some sort of thermostat with a narrow on/off set of parameters. Otherwise I would be in and out of the house doing the swithing manually. I posted on a newsgroup and it was suggested that a mylar flap be used to automatically open/ close the output opening when the termosiphon attempted to reverse. I like the simplicity but the fan would be far better. If you come across or know of a solution, please post it!!
Thanks,
Chiz