hot air

[MooseToo]

toying with the idea of putting together a solar heat collector (air) and need advice as to transfer ducts to a gravel bed heat storage bin -
does anyone have an experience factor that might suggest the highest temp air that might be blown through pvc or abs piping without degrading the pipe ?
thanks !

[MadTripper]

I believe the pvc I used for my exhaust pipes on our furnace is rated to 300 F but I'll have to double check that. Do you have a diagram of your intentions?

Tripper

[MooseToo]

no - just playing it by ear - planning to build a pole barn and put a pit down the center - a couple feet of gravel at the bottom with hot air channeled through and cover the whole thing back up to grade level -
the idea being to heat the whole thing up during the warmest fall days and see what residual heat remains when it gets colder -
nothing sophisticated or expensive - just an experiment really -

[flatwater]

MT ,I would give you a good source of hot air but I would have to ask Buck first.Hee Hee :D I would even invent the hook up for you :P.
Flatwater

[MooseToo]

i don't think plastic pipe would hold up to THAT -
heat or pressure - not both -

[Drawbar]

I don't think he is talking about much pressure hear, and as Tripper pointed out, our mini-boilers have been using PVC pipe as a vent and exhaust for years.

I like your idea, but my only suggestion is before you put gravel down, put a whole lot of rip-rap in. That is what I did on my radiant floor heated new house addition (28 x 40). I put 100 yards of big rock, 8 inch to 4 inch in diameter, in first and then put gravel over that. I still put 2 inch insulation between that and the concrete, but that added mass really acts as a heat sink. You would get even more heat from that mass in your situation.

Interestingly enough, a city somewhere did a study regarding a city street. They figured the black top absorbs a lot of sun and heat in the summer and they wondered if it could melt the snow in the winter. So as an experiment they took a ¼ mile of highway and sunk wells deep into the ground and then let the sun heat that water up. In the winter they switched on some pumps and melted the snow. In fact the water was so hot, and of such a volume that they hooked it up to the heating system of a nearby apartment complex and heated that place too.

[johnjmw]

Interesting Idea. What would you use to circulate the the hot air? Fan or natural air flow (from what). Maybe a small solar panel with a fan attached and a thermal coupler that only turned the fan on when the collector temp was high enough?

John

[MooseToo]

yes - i was planning to use forced air - my whole idea centered about trying to bottle a little summer to take the peaks out of winter -

[12vman]

Let's see how long it takes for Buck to find these comments.. ;) ;D (He has no interests here, IMO)

Anyhow, since you plan to use forced air, this may be an easier alternative being that you have enough area to install the underground pipes..

http://mb-soft.com/solar/saving.html

By looking at the map, the average ground temperature in your area is around 60 degrees. There wouldn't be any need to depend on the sun and I believe this idea would be more cost effective. No special construction to the building would be needed. It can also keep things cooler during the summer!

[MooseToo]

yeah - i've looked into that and it surely has potential - but i'd lose the opportunity to satisfy my accursed curiosity and force me to deny my suspicion that God gave us summer heat for something more than swilling lemonade and swatting no-see-ums -