Pop Can / Downspout Solar Heater... - Page 2

creeky · 11-04-11, 07:11 PM

downspouts should speed up the manufacture. Forget the cans, downspouts are cheap. I've got a couple of extras, hmmm.

One thought. I remember a study done on colours that warmed up the quickest; I think it was for fishing boat manufacturers who were trying to decide what colour carpet to use in their boats. Dark green gathered more sun energy, ie. heated up faster than black.

Anybody try dark green paint on their solar heaters?

I've always thought the green had something to it; I mean, grass, trees, etc ...

absolute0 · 11-04-11, 10:42 PM

Without the cans, assuming the intake is not pumping in air too fast, the air should rise fairly slowly, and I don't think cans will be of any help. Like someone already said, the air will do best touching the pipes being heated.

Since you are doing this to learn about the technology, some things to think about:

If the air in the downsprout is taking x degrees of heat from the metal, then the air outside the downsprout (but inside the collector) is taking heat at a similar rate. The goal in engineering more efficiency out of the collector comes from preventing that heat from leaving the collector.

Some of the issues: The air is touching 6 faces. The 5 non glass/plexiglass borders, and then the glass/plexiglass. If you insulate the bottom of the collector, that eliminates a large surface from transferring the heat of the air to the colder outside.

But the glass/plexiglass you use will be directly touching the outside air. It should not be absorbing enough radiation to heat up more than the inside air, thus it will be taking heat from the inside and transferring it to the outside. This reduces the efficiency, especially during winter months.

Kind of a bummer for us diy-ers making these without access to special coatings and argon gas...or materials strong enough to resist a vacuum.

strider3700 · 11-04-11, 11:10 PM

Of course by being dirt cheap and easy to build you can always just make two and will probably come out way ahead on time, money and heat collected compared to trying to make the perfect collector.

absolute0 · 11-05-11, 12:03 AM

I didn't think of it that way. Would probably come waaaaay ahead on time/money/heat. I need to start thinking like that before I start my projects.

nitro-nige · 05-01-13, 01:27 AM

I'm in the planning stage for a Solar heater/thermosiphon and have been wondering how effective it would be to replace the pop cans with a sheet of dark corrugated roofing material?
Is my understanding correct that it's the contact between the air moving through the heater and the "internal element" that has been heated by the sun that makes the system work? So the pop cans have to conduct the heat to the inside of the can.

iamgeo · 05-01-13, 08:45 AM

edit.. nevermind.

Daox · 05-30-13, 01:00 PM

The cans are so thin it doesn't take anything to transfer heat from the outside to inside. Really, you want a material that is good at absorbing and releasing heat (like aluminum or copper) as your absorber material.

Mikesolar · 06-08-13, 01:20 PM

If you have a fan at the top, it is best to have a bigger return at the bottom. This is the rule in ductwork and liquid piping. The higher head is on the output side of the fan/pump.

iamgeo · 06-08-13, 01:24 PM

I have to ask. Why would you consider putting cans INSIDE the downspout? I have been researching Solar Air Heaters for a couple years and never came across that idea.

11-04-11, 10:42 PM	#12
absolute0 Lurking Renovator Join Date: Nov 2011 Location: Connecticut Posts: 2 Thanks: 0 Thanked 0 Times in 0 Posts	About the air flow...and other stuff Without the cans, assuming the intake is not pumping in air too fast, the air should rise fairly slowly, and I don't think cans will be of any help. Like someone already said, the air will do best touching the pipes being heated. Since you are doing this to learn about the technology, some things to think about: If the air in the downsprout is taking x degrees of heat from the metal, then the air outside the downsprout (but inside the collector) is taking heat at a similar rate. The goal in engineering more efficiency out of the collector comes from preventing that heat from leaving the collector. Some of the issues: The air is touching 6 faces. The 5 non glass/plexiglass borders, and then the glass/plexiglass. If you insulate the bottom of the collector, that eliminates a large surface from transferring the heat of the air to the colder outside. But the glass/plexiglass you use will be directly touching the outside air. It should not be absorbing enough radiation to heat up more than the inside air, thus it will be taking heat from the inside and transferring it to the outside. This reduces the efficiency, especially during winter months. Kind of a bummer for us diy-ers making these without access to special coatings and argon gas...or materials strong enough to resist a vacuum.

05-01-13, 01:27 AM	#15
nitro-nige Lurking Renovator Join Date: Dec 2010 Location: Melbourne, Australia Posts: 12 Thanks: 0 Thanked 2 Times in 2 Posts	Alternative construction idea I'm in the planning stage for a Solar heater/thermosiphon and have been wondering how effective it would be to replace the pop cans with a sheet of dark corrugated roofing material? Is my understanding correct that it's the contact between the air moving through the heater and the "internal element" that has been heated by the sun that makes the system work? So the pop cans have to conduct the heat to the inside of the can.

05-01-13, 08:45 AM	#16
iamgeo Apprentice EcoRenovator Join Date: Aug 2010 Location: Lakehills, Tx Posts: 168 Thanks: 4 Thanked 10 Times in 9 Posts	edit.. nevermind. Last edited by iamgeo; 05-01-13 at 08:49 AM..

05-30-13, 01:00 PM	#17
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	The cans are so thin it doesn't take anything to transfer heat from the outside to inside. Really, you want a material that is good at absorbing and releasing heat (like aluminum or copper) as your absorber material. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

11-04-11, 07:11 PM	#11
creeky Journeyman EcoRenovator Join Date: Jun 2011 Location: a field somewhere Posts: 304 Thanks: 64 Thanked 44 Times in 31 Posts	downspouts should speed up the manufacture. Forget the cans, downspouts are cheap. I've got a couple of extras, hmmm. One thought. I remember a study done on colours that warmed up the quickest; I think it was for fishing boat manufacturers who were trying to decide what colour carpet to use in their boats. Dark green gathered more sun energy, ie. heated up faster than black. Anybody try dark green paint on their solar heaters? I've always thought the green had something to it; I mean, grass, trees, etc ...

11-04-11, 11:10 PM	#13
strider3700 Master EcoRenovator Join Date: Dec 2008 Location: Vancouver Island BC Posts: 745 Thanks: 23 Thanked 37 Times in 30 Posts	Of course by being dirt cheap and easy to build you can always just make two and will probably come out way ahead on time, money and heat collected compared to trying to make the perfect collector.

11-05-11, 12:03 AM	#14
absolute0 Lurking Renovator Join Date: Nov 2011 Location: Connecticut Posts: 2 Thanks: 0 Thanked 0 Times in 0 Posts	I didn't think of it that way. Would probably come waaaaay ahead on time/money/heat. I need to start thinking like that before I start my projects.

06-08-13, 01:20 PM	#18
Mikesolar Master EcoRenovator Join Date: Aug 2012 Location: Toronto Posts: 958 Thanks: 40 Thanked 158 Times in 150 Posts	If you have a fan at the top, it is best to have a bigger return at the bottom. This is the rule in ductwork and liquid piping. The higher head is on the output side of the fan/pump.

06-08-13, 01:24 PM	#19
iamgeo Apprentice EcoRenovator Join Date: Aug 2010 Location: Lakehills, Tx Posts: 168 Thanks: 4 Thanked 10 Times in 9 Posts	I have to ask. Why would you consider putting cans INSIDE the downspout? I have been researching Solar Air Heaters for a couple years and never came across that idea.