solar heat from pop cans...

[camillebug]

The reason behind the pop cans is to increase the surface area that can come into contact with the air. More surface area of heat exchange will drive the efficiency up until you reach the limit of diminished return. The pop cans serve an efficiency role not a necessary one.

 

[patandchickens]

Mr. Peepers :

Is this thing practical?

(e.t.a. - sure it's practical! lots of people use that general sort of setup to heat their workshop, barn, part of house, whatever.)

It seems to me that it wouldn't work in the dark, in clouds, and at high latitudes...in other words, all of the times when it would be useful. I've never built one, so I can't say for sure, but I'd guess that if you need heat in your hen house, a nice ceramic bulb heater would be a lot cheaper and easier.

Not necessarily. Not cheaper if you are scrounging materials, CERTAINLY not cheaper in operating costs (since a 125 or 250w bulb will make a noticeable dent in your electric bill if you run it 24/7, whereas the solar setups have no operating costs at all). Also passive solar is independant of the public grid and does not accidentally start fires

Passive solar works well in higher latitudes as long as the sun is still meaningfully above the horizon (this includes *nearly* everyone who keeps chickens, and even in the furthest north areas solar is still useful the rest of the year)... you just need to arrange it so the collector is roughly perpendicular to the noontime sun, and fortunately by the time you get the coldest part of the winter (mid Jan through mid Feb) the days are much longer and the sun much higher than they were in mid-December.

Solar would not be a good choice for a nearly-always-cloudy location, but for most people that is not the case. Even here, where we get a lot of lake-effect stuff in Nov-Dec and sometimes thereafter, and thus a lot of cloudiness, solar is DEFINITELY worthwhile.

"In the dark" is why you want to ensure sufficient thermal mass (through large size of coop per se, through a slab or dirt floor, and/or through design features specifically providing extra thermal mass). The idea is not so much to heat the coop *air* as to heat the thermal mass *in* the coop, so a reasonable amount of heat carries through til morning. Thermal mass (especially coupled with tapping into the latent warmth of the ground) carries a LOT more heat over than you might think. Especially in a well insulated coop with not-too-high ventilation requirements.

Solar works best when the rest of the building is designed/adapted to complement it well; but it is ALWAYS worthwhile IMHO if you are in a situation where you have any heating needs at all. It may not fulfill all your needs all the time (or, it may -- solar plus lotsa thermal mass and a slab floor is quite sufficient for my setup) but it will always go a long way *towards* them.

Pat​

 

[AkTomboy]

We have been saving cans for a bit and after our trip will be building one. I know it will be quite cheaper than having to heat with bulbs or panel heaters as the sun is free. Even if it just works for part of the day it will help.

 

[Mr. Peepers]

Quote:
(e.t.a. - sure it's practical! lots of people use that general sort of setup to heat their workshop, barn, part of house, whatever.)

It just seems to me that by the time you built a big enough heatsink in your coop, installed and adjusted switches to turn the thing on/off when it's dark or cloudy, installed a thermostat to run the switches, installed a fan and installed a solar cell to power all this you would be running into way more expense and effort than if you just plugged in a heater when (and if) you need it. There would also be the chore of cleaning off leaves, pine needles, ice, snow and dust from the solar cell and the heater.

Solar certainly has it's applications, but I can't convince myself this is one of them. It may be practical for a workshop, barn, house, etc. where people are present during the day and can control the thing and a large heat sink is practical or no one is present at night. You'd have to have concrete or stone walls on your coop to even approach a decent heat sink and that would run into some real expense. I cover my floors with pine shavings/straw and a concrete, earth, or stone floor covered with 6" of insulation is not much of a heat sink.

 

[patandchickens]

Mr. Peepers :

Quote:
(e.t.a. - sure it's practical! lots of people use that general sort of setup to heat their workshop, barn, part of house, whatever.)

It just seems to me that by the time you built a big enough heatsink in your coop, installed and adjusted switches to turn the thing on/off when it's dark or cloudy, installed a thermostat to run the switches, installed a fan and installed a solar cell to power all this you would be running into way more expense and effort than if you just plugged in a heater when (and if) you need it. There would also be the chore of cleaning off leaves, pine needles, ice, snow and dust from the solar cell and the heater..​

Um, speaking as someone who has a (chicken-occupied) version of this *actually in operation*, in its second year now...

1) I did not build a big heat sink in the coop, it's part of the coop structure (slab). If it weren't, I'd just fill some (scavenged) plastic barrels/jugs/carboys with saltwater and sit them where they can't fall on anything. Not a big investment of effort, and free.

2) whatchyou talkin bout, all that equipment?? Of course you CAN do it that way if you enjoy gadgetry but by no means are any of those things necessary and I sure don't use any of them at all.
switches -- no, I walk out and open or close the window and popdoor. Usually this coincides with putting chickens in/out
or getting eggs anyhow. if you want something that will operate untended, you can make backflow-preventer
flaps w/ a grid and a piece of flimsy plastic taped on as a flap. In northern climates this should ideally be
manually covered by insulating panel for night but will at least prevent back-circulation, which is the most
important thing.
thermostat -- no, that would be 'me', or if you make the above-mentioned flaps they work automatically by air pressure.
fan -- no, the whole point of passive solar power is that you do not NEED a fan, the rising hot air makes the whole thing 'go'
on its own. one can certainly add a booster fan, and may need to if you want to route the air somewhere weird
and unnatural, but normally it is not needed.
solar panel -- no, see above re: lack of need for fan

(the above was edited about a billion times to try to get the tabs right

)

3) you never need to clean leaves, pine needles, ice or snow off the collector panel because it is at a steep angle. Solid objects do not collect there (more than very very briefly at most), and snow and ice melt off real quick on their own. I end up with a bit of a snowdrift (from stuff that has slumped off the front) at the base of the solarized run, but leave it there as it does not block any meaningful height of active panel and I figure it gives a bit of insulation. Also I am lazy

Really, this is a very easy to build and very LOW WORK INPUT heating system.

Pat

 

[AkTomboy]

Quote:
It just seems to me that by the time you built a big enough heatsink in your coop, installed and adjusted switches to turn the thing on/off when it's dark or cloudy, installed a thermostat to run the switches, installed a fan and installed a solar cell to power all this you would be running into way more expense and effort than if you just plugged in a heater when (and if) you need it. There would also be the chore of cleaning off leaves, pine needles, ice, snow and dust from the solar cell and the heater..

Um, speaking as someone who has a (chicken-occupied) version of this *actually in operation*, in its second year now...

1) I did not build a big heat sink in the coop, it's part of the coop structure (slab). If it weren't, I'd just fill some (scavenged) plastic barrels/jugs/carboys with saltwater and sit them where they can't fall on anything. Not a big investment of effort, and free.

2) whatchyou talkin bout, all that equipment?? Of course you CAN do it that way if you enjoy gadgetry but by no means are any of those things necessary and I sure don't use any of them at all.
switches -- no, I walk out and open or close the window and popdoor. Usually this coincides with putting chickens in/out
or getting eggs anyhow. if you want something that will operate untended, you can make backflow-preventer flaps
with a grid and a piece of flimsy plastic taped on as a flap. In northern climates this should ideally be manually
covered by insulating panel for night but will at least prevent back-circulation, which is the most important thing.
thermostat -- no, that would be 'me', or if you make the above-mentioned flaps they work automatically by air pressure.
fan -- no, the whole point of passive solar power is that you do not NEED a fan, the rising hot air makes the whole thing 'go'
on its own. one can certainly add a booster fan, and may need to if you want to route the air somewhere weird
and unnatural, but normally it is not needed.
solar panel -- no, see above re: lack of need for fan

3) you never need to clean leaves, pine needles, ice or snow off the collector panel because it is at a steep angle. Solid objects do not collect there (more than very very briefly at most), and snow and ice melt off real quick on their own. I end up with a bit of a snowdrift (from stuff that has slumped off the front) at the base of the solarized run, but leave it there as it does not block any meaningful height of active panel and I figure it gives a bit of insulation. Also I am lazy

Really, this is a very easy to build and very LOW WORK INPUT heating system.

Pat

Pat I am super excited to try this out. I do have an panel heater in my coop now on a thermostat. Simple but can get spendy at -50 super fast. So we hope to have this help out during the day, and as you said we go and do things such as eggs and pop door and such every day so opening and closing the vent will be an easy thing. I also agree with your experiance of the lact of snow build up and such. Thanks for the great post AkTomboy

 

[chookchick]

Sorry if this has been covered--didn't read the whole thread, but I see a major design flaw with this solar pop can heater. The problem is that the heat is abundant when the sun is out, but there is no built-in heat sink to store heat for when you really need it (like at night). The best design would be a south-facing coop, with large windows or window (insulated), that had a wall of black containers filled with water, or a stone wall painted black as Pat mentions. The window wall would of course need to be covered when it gets really hot. This would hold heat through the night. I really don't see the point of having a solar collector that only makes heat when it is sunny out--you can do this with just a plain window.

 

[Mac in Wisco]

It's supposed to be free supplemental heat to help cut your heating costs during cold weather. Not the only means of heat.

As I mentioned before, our layer barn ventilation is designed to pull warm air from the attic in the winter. Does it heat all the time? No. But when it's sunny out the added heat in the dead of winter sure helps a lot.

 

[chookchick]

Mac that sounds like a good system--you are using your roof as a heat collector and then moving the warm air through as needed. This actually makes a lot more sense to me since you have a large volume of air. But is a fancy box with black cans really that much more efficient at collecting heat than just a south facing window? Just trying to be a realist here. OOPs the lights flickered!! (there is a windstorm outside).

 

[Mac in Wisco]

Quote:
I guess it depends upon what you have inside the window. The window itself isn't the collector, it's just transparent insulation. It's what's inside that's collecting the energy.

I've looked at these designs in the past and have even seen ads for a commercial version. The commercial version had a thermostatically controlled damper that only allowed air flow through the unit when it was being heated and an optional fan to move the air.