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paullad

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Reply with quote  #1 

Let me qualify this post by saying I don't know what I'm doing. [smile] Just experimenting. I've currently got 150 sq ft of glazing on my solarium/porch which should net me about 70k btu on an average full sunny winter day (near Chicago). My little house overheats even in the winter to about 80 degrees on a full sunny day. I figure (rough estimate) maybe 20k btu in losses (based on a test) and 50k btu that could be stored during the collection period.

Here's my plan. Fill the space between some of the floor joists under my living room with 200 - 2 liter pop bottles full of water (approx 100 gal); enclose the joists underneath with 2" foam and plywood and super-insulate the sides to about R50. Then if I move about 400 cfm of the 130 degree sunspace air into this little water vault and get good heat transfer it should keep the solarium at about 80 degrees and might take the water from 50 to 110 degrees. Then I can just open the vent in the living room floor as heat is needed.

It may hardly seem worth doing because of the small amount of excess heat to store but of course in the spring and fall this number could be doubled and since losses will be much less it might heat the living room for a whole day or more. Plus it will make the solarium usable on sunny days. And it will be really nice to have a warm living room floor. Plus if I can get a system like this working, I plan to add at least another 100 sq ft of collector.

The big question in my mind is how to make sure there is enough heat transfer to the bottles. Would this really be a big issue though since the 2 liter bottles have so much surface area and the plastic is so thin?

Does anyone have any thoughts on any or all of this? Thanks for your insights.

Garage_Hermit

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Reply with quote  #2 
Hi, Paullad,  welcome on board !

I'd forget about plastic bottles in joist bays - it is asking for trouble (they will eventually LEAK and rot your joists, which would cost more than installing a proper heating system...).

At the least, condensation occurring on them would likely encourage MOLD, which is *very_bad* for health...

==========
If you have access to the underfloor, by the sound of it you have, then maybe you have a basement or at least a crawlspace, in which case you probably have room for THIS idea...
http://www.builditsolar.com/Projects/SpaceHeating/Multi%20Drum%20Heat%20Storageb.pdf


Please don't think I am knocking your ideas, on the contrary - you are bang-on with your thinking - i.e. getting some THERMAL MASS into your home, to absorb heat...

there's just better ways to do it...

Maybe post some details of your home - such as existing structures, walls, ceilings, floors...

Some off-top-of-head ideas FWIW:

G_H

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(1)  "Heat goes from hot to cold, there is no directional bias"
(2) It's wrote, "voilà" unless talking musical instruments...
stmbtwle

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Reply with quote  #3 
Hmm I like the idea of a water tank disguised as a BAR. Does anyone know the specific heat of booze? Does anyone care? [wink]
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Willie, Tampa Bay
mattie

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Reply with quote  #4 
You are on the right track for sure with water as your energy storage medium, condensation is a concern . Wouldn't fancy moving concrete furniture around so much G_H ,cannot fault the built to last design ethic though [smile] Other links are great too and well worth taking from.
paullad

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Reply with quote  #5 
Quote:
Originally Posted by Garage_Hermit
Hi, Paullad,  welcome on board !


Thanks. Glad to be here.

Quote:
I'd forget about plastic bottles in joist bays - it is asking for trouble (they will eventually LEAK and rot your joists, which would cost more than installing a proper heating system...).


I've never heard of 2 liter bottles leaking if they are sealed well and haven't had that problem myself. Either way, I wasn't planning on making this water proof and if water leaks onto the ground in the crawl space I'm not worried about it.

Quote:
At the least, condensation occurring on them would likely encourage MOLD, which is *very_bad* for health...


Are you sure about this? That would kill the idea if its a sure thing. But I never had any problem with condensation when I had bottles in the attic and the temperatures are not much different between the attic and the space between the floor joists in the winter...50-55. BTW, my rafters are insulated. That's why it stays warm in the attic. Actually the attic has been converted into living space so its no longer an attic.


Quote:
Please don't think I am knocking your ideas, on the contrary - you are bang-on with your thinking - i.e. getting some THERMAL MASS into your home, to absorb heat...
there's just better ways to do it...


No offense taken. Knock away. [smile]  That's why I post this stuff. I love constructive criticism...as long as the person knows what they're talking about.

Quote:
Maybe post some details of your home - such as existing structures, walls, ceilings, floors...


Its a little story and a half house and about 800 sq ft including solarium. Walls are drywall except wood in the solarium, ceiling on the main floor is wood. The 1/2 story ceiling (under roof) is drywall. Floors are wood except vinyl in bathroom.


Quote:
Some off-top-of-head ideas FWIW:



Thanks for posting those. The reason I'm not using mass in the solarium for storage is because I would have to insulate the 150 sq ft of glass and that means a manual operation of very expensive ($10/sq ft.?...not in the budget) insulated shutters (I've got these in my living room and have yet to see other good options for the solarium). And how do you deal with full sun for a few hours, then cloudy for a few hours, then sunny again, then cloudy again (as it has been the last few days) without manually closing the shades during the cloudy periods? During the cloudy periods, I might lose all of the stored heat if I don't close the shades.

I could put mass in the living space but since its such a small house, there really isn't any room other than in the floors which would get very little direct sun.

Moving the heat to a permanently insulated storage seems like a much better idea and the crawlspace is the only good option that I can figure. Originally I planned on using 5 gallon buckets in a super insulated water vault below the living room. I considered the pop bottles in the joist bays because of the better heat transfer than buckets.

Any way, thanks for the ideas.

mattie

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Reply with quote  #6 
You should have the option of some type of ventilation and humidity sensors to reduce any condensation issues. Im sure what G_H is saying relates to an induced dew point on the surface of the bottles due to a difference in temperature between the water inside the bottle and the incoming air.The moisture from the air will end up sitting externally on the water bottles.
Garage_Hermit

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Reply with quote  #7 
Hi, again, Paullad...

  

MOLD, which is *very_bad* for health...

Don’t take my word for it:

http://www.jeswork.com/crawlspace-repair/crawlspace-mold-and-your-health.aspx

http://www.cdc.gov/mold/dampness_facts.htm


========

 

Quote:
The reason I'm not using mass in the solarium for storage is because I would have to insulate the 150 sq ft of glass

 

Not necessarily: sure, if you insulated the glass, the heat would stay in longer after sun-down etc.

 

However, enough thermal mass (read, barrels of water) in a sunspace would still provide more heat than none at all…

Which means that because of the higher temperature difference, the rest of the house would in turn *lose* *less* heat to the sunspace…

 

That is why I suggested :

(Which gets around the “lack of direct sun” issue…)


Good to have a crawlspace: you could simply store static barrels of water down there – you would get more mass than bottles…

(I forgot to say, another anti-bottle point is, filling a joist-bay with bottles is great for giving a certain vol of water, but is not conducive to having a BIG volume of air, and for effective heat transfer, you would need the latter...)

 Even a barrel of water will not give up all the heat it has absorbed, but it WILL go a long way to absorbing temperature swings…

 

G_H…

 

 


__________________
(1)  "Heat goes from hot to cold, there is no directional bias"
(2) It's wrote, "voilà" unless talking musical instruments...
stmbtwle

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Reply with quote  #8 
Barrels of water while a good idea DO take up a lot of space.  Sometimes the "boss" has other ideas.  Mine did [frown]  She doesn't pay the bill, so only cares about "appearances".

I'm having to put mine outside in an insulated space, and pump the heat in.  Upside is I'll have to pump the heat into the barrels, so they should heat up faster, and store more heat, which I can then pump out on demand.   I hope...



__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Garage_Hermit

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Reply with quote  #9 
Quote:
pump the heat into the barrels, so they should heat up faster, and store more heat, which I can then pump out on demand.  
I hope...

Willie, I am certainly quite a few steps behind you, but that is exactly where I want to get, also !

G_H

P.S. ?? Need a good air-water HEX design, cheap [wink]

__________________
(1)  "Heat goes from hot to cold, there is no directional bias"
(2) It's wrote, "voilà" unless talking musical instruments...
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