solar heat from pop cans...

[Mr. Peepers]

Quote:
It's interesting to learn that you're actually using such a device. Have you done an energy audit? What do you do for heat on cloudy/rainy/snowy days? I would be very curious to see if a pop can heater could be any more effective than south facing windows.

Is your concrete slab bare? Could you post a few photos of the whole setup?

 

[patandchickens]

Quote:
Eh? The plans are for a solar heater, not everything else that might help keep the coop warm *too*

Even if you do not install anything purpose-built, the coop itself has SOME thermal mass just by virtue of its construction and existance, especially if it is largish and/or has a slab or dirt/sand floor and/or heavy timber framing. ANY building of reasonable size DOES keep day warmth through the night to a considerable degree (that, combined with latent heat of the earth in the first part of winter, is why even unheated and unoccupied outbuildings will stay warmer than the nightly low outdoors, especially on the coldest nights of the year).

So it isn't like "it doesn't give any nighttime benefits unless you go to special lengths to build in extra thermal mass". Doing that iwll make it work *better* but even without, it will work in proportion to however much air volume and ground surface and building-material thermal mass the coop *already* has.

(edited to add:

But is a fancy box with black cans really that much more efficient at collecting heat than just a south facing window?

Yes, it is. Considerably, in most cases. First, because it is likely to involve a lot extra area (it is in addition to existing windows, not instead of, and does not have the size limitations that windows do); second, because its heat capture can be somewhat more effective; and thirdly (a biggie) because you shut it off when the sun is not shining and it does not lose heat from the coop, whereas windows are always large heat-LOSERS unless you are there with a very heavily insulated panel to cover the window with as soon as the clouds roll in or night falls. And realistically, I doubt that 0.1% of coop owners actually cover their coop windows like that, making windows a pretty significant source of heat loss.

Pat​

 

[patandchickens]

Mr. Peepers :

It's interesting to learn that you're actually using such a device. Have you done an energy audit? What do you do for heat on cloudy/rainy/snowy days? I would be very curious to see if a pop can heater could be any more effective than south facing windows. Is your concrete slab bare? Could you post a few photos of the whole setup?

I am not sure kind of energy audit you have in mind, but I can tell you that I have fooled around fairly extensively when we have a stretch of stable weather (same temps, sunniness, windiness for several days) where one day I will open popdoor/window and let the solarized run heat the building, the next day keep it closed, the next day open it again, etc, and look at how coop temperature behaves. That is the basis from which I can say that it makes a 2-5+ C difference (that's like 4-12+ degrees F) despite the large building size and considerable thermal inertia in the building. Mathematics suggests it should make a much larger difference to a more normal-sized coop, although how much the heat peaks in daytime vs being distributed through nighttime hours obviuosly depends on the thermal mass involved.

I am not sure what you mean by "what do I do for heat on cloudy/rainy/snowy days". I don't do anything for heat, the building is just whatever temperature it IS on those days, cooler than on sunny days, but you know, they're chickens, they are SUPPOSED to experience weather

and do fine with the temperature range they experience here. (Obviously I have no need for solar heating on RAINY days anyhow, since that implies a fairly warm temperature

)

As described in a previous post, there are several advantages of a popcan type panel (or my solarized run) over a window, but the biggest is that you can SHUT IT OFF when not actively heating, so there is little or no heat loss. (I expect I get some small extra benefit from my particular setup since it traps dead air, with exposed ground mass too, against half of one of the short walls of the building, thus presumably reducing radiant heat loss a bit even at night. I doubt this is a large effect jsut b/c of the small proportion of wall covered by the run, but in a more normal sized coop it would be significant)

Here are the pics of the chicken building that I've posted on other threads in the past. I should probably take some more. Actually I have some from this year somewhere on the computer but dialup makes it real hard to upload pics to photobucket so I dunno when/whether that'll happen

Here is a view of the whole building last winter from the south (the roofed part on the L that was used for storage last year is now chanlinked in and partly tarped on the W side, for use as a chicken run).

this is a closeup of the front run from last year before I had the door entirely plastic-covered, so there is junk propping a scrap of clear acrylic across the bottom of the door, but you get the general gist. It did btw work much better once I properly plastic-covered the whole door and stopped up air leaks.

The building is 15x40, with a slab floor exposed on approximately 60% of the floor area (the rest is covered with OSB and shavings, some parts have foamboard under the OSB too - I did not do this, it was originally a dog breeding/boarding kennel). The buidling has 6" stud walls fully insulated, and a well-insulated drywalled ceiling. Last winter, which is when those numbers I quote are from, I had one *large* (dog sized

) popdoor open most of the day on all but the nastiest days; this year I will have two or three open (on opposite sides of the building, for reasons beyond my control) and will be interested to see how that works out temperature-wise, presumably the building will be a bit colder than it did last year, oh well.

Pat​

 

[Mr. Peepers]

Pat,

I got the wrong impression from something I read somewhere in this long and winding thread. I thought you were using a pop-can heater. From your photos it appears to me that you are just using an enhanced south facing window. Your setup appears way more practical, and I can easily understand how it might provide a little auxiliary heat without being too expensive, complicated or time consuming. I still can't say the same thing about a pop-can heater.

 

[patandchickens]

Mr. Peepers :

Pat,

I got the wrong impression from something I read somewhere in this long and winding thread. I thought you were using a pop-can heater. From your photos it appears to me that you are just using an enhanced south facing window. Your setup appears way more practical, and I can easily understand how it might provide a little auxiliary heat without being too expensive, complicated or time consuming. I still can't say the same thing about a pop-can heater.

No, it is NOT an 'enhanced south-facing window', it IS a popcan heater type setup, just one large enough for chicken occupancy LOL

The cool coop air comes into the 'collector' from the pophole at the bottom; is heated by the sun; and blows (naturally, without electricity) into the coop through the top of the window. (It would be better if the window were not a window but rather a long slot along the very top of the lean-to; but I see no reason to make major modifications to the building when it works fine for my purposes as is).

This is *functionally quite different* than just having sun shining in through a window.

Really, the field of passive solar design is fairly well-developed these days and there are lots of websites and books if you want to learn more about it.

I still do not see why you are calling a popcan-style heating panel expensive, complicated, or time consuming. You can knock together a very functional one out of a clear panel of something heat-stable such as glass or Suntuf, plus some black paint, a piece of scrap roof tin or any other similar thing (popcans even <g>), and a bit of plywood and insulating material.

Really, I could put a 3x3' unit together in about an hour from materials I have on hand right now, it is not a challenge for anyone to do it themselves for free. (bigger than 3x3 would be better, of course, but even that size would be useful for a small coop). Cut a low hole and a high hole into your coop wall for the 'plumbing', and there ya go. No batteries, no 'technology', no complications. The people whose websites or youtube videos you see, who've made it all complicated, have done that as a *hobby*, not as a necessity for operation

Actually that run of mine took MUCH longer to build than it would've if I were just making a passive solar panel of this type, and cost more

Pat​

 

[chookchick]

Aside from the question of whether or not the SPCH is more effective than passive solar heat from a window, I am looking at how this arrangement can benefit the chickens. Since the temperature is coldest early in the morning, in order to prevent frostbite, ameliorate cold temps etc...whatever is used MUST be able to hold temps somewhat higher for quite a while. The SPCH would quit collecting heat by about 5pm (in winter), I find it hard to believe that it could have much residual effect on temps 12 hours later. That much more effect than say, a black roof, or a concrete foundation. It seems to me that it would be far better to concentrate efforts on conserving the heat of your natural heaters (the chickens) through insulation, etc..or working on incorporating some type of heat sink into the wall of the coop. Creating drastic temperature swings in the coop does not seem like a productive thing to do for the chickens. BTW my husband thinks that we should use the hot air created on BYC to heat our coops!......

 

[Mr. Peepers]

Quote:
I can't see the pop cans in your photo. Your setup appears to be a small greenhouse assembly fronting a south facing window. Did I miss something? Effective use of solar and other alternative energy sources is a laudable goal, but I still have to question the practicality of heating a chicken coop with pop cans.

 

[patandchickens]

Mr. Peepers :

Quote:
I can't see the pop cans in your photo.

Yes you can. They are blue, and flat-with-corrugations, and approx 2' wide and 8' tall

Your setup appears to be a small greenhouse assembly fronting a south facing window. Did I miss something? Effective use of solar and other alternative energy sources is a laudable goal, but I still have to question the practicality of heating a chicken coop with pop cans.

Honestly, I am baffled by your fixation on literal popcans here

They are by no means essential to the design, as a thorough reading of the first umpty pages of this thread will show, and further reading elsewhere on other DIY passive solar panel designs of this type will further illustrate.

The CLASS of heater being discussed here is one that works like this:

__________________________________
|
__|
<--warm air blows in (b/c risen)<-- : sun
| : / / /
s| :
inside of building o| :
l| :
i| :
d| :
w| :
a| :
l| :
l| :
-->cool air goes into panel-->--> :
____________________________________:_______________________

The panel is shown here as a clear panel with a narrow airspace in front of a solid (ideally dark-colored) rear wall. That airspace can be just a coupla inches of airspace, or it can have various metal thingamajiggies (popcans, piping, metal fins, what-have-you) added in an attempt to increase its efficiency. (The airspace on mine is actually much wider than normal, with chickens added, as a compromise between heating efficiency and all-round usefulness

)

The CHARACTERISTIC feature of this type of passive solar heater, though, that makes it QUITE DIFFERENT from just having a sunny window or greenhouse, is not what if anything is in the airspace. It's the fact that you have an opening at the very bottom of the panel and at the very top of the panel. This creates active circulation of air through the panel -- air in the panel is heated, rises, escapes through the top opening (note that this works a lot better if it is a bit below ceiling level in the structure being heated, so it really can *rise*), and in doing so pulls cool floor air into the panel to be heated and rise and blow out and so on and so forth.

It is like a forced-air system, in that air is actively moving through the unit all the time (as long the airspace of the panel is being sun-warmed); just not 'forced' air in the sense that you are not applying any electricity to it.

BTW since I took the time to do the ASCII pic I will point out that the way to make it shut off automatically when the sun is not out is to put a grid (in houses heated this way, people often use furnace vent register covers) over the top and bottom openings. On each opening you affix a flap of very flimsy plastic, like in plastic baggies, attached at the top only. You attach the top one on the INSIDE of the grid, and the bottom one on the OUTSIDE of the grid. Then when the airspace cools and the air tries to circulate backwards (which it *will* do if left to its own devices, actively cooling your structure

) the flaps are pressed against the grids and block off air circulation; when air is trying to circulate the *correct* direction, they are flimsy enough to just blow open and permit airflow. Insulated/weatherstripped covers are still smart to put in place for nighttime in cold climates though

Pat​

 

[patandchickens]

Quote:
I do not recall it being advocated that one create drastic temperature swings with these things??? Certainly that would be a bad idea. By no means is it an inherent element of the design, though.

The more thermal mass is built into your coop, the less swing you will get. The more thermal mass you've got, the less the heat output of the solar panel (or a sunny window, or just the warmer daytime air blowing in thru the vents and popdoor) warms the air.

And the more total stored heat you have from daytime, the more warmth the coop holds at night (decreasing asymptotically til coop temperature equals outdoor temperature, but in a decent size coop that does not happen on many if any nights). Except in a very small coop, yes, the boost from your thermal mass DOES last til dawn to some degree, also it lessens how cold it is *for how long*.

Anyhow, anywhere I've ever lived, days are *normally* at least 20F warmer than nights, it is unnatural to have constant temperatures. I've not seen people nor animals have trouble with temp fluctuations of 30-35F, either (more than that gets to be a little iffier... but only a little, unless you get to really bizarre things like when it's 60F one morning and then a cold front comes through adn drops things to 0F in less than 24 hours). So even if your solar heater warmed things up like 20-30F in your coop, I fail to see how that would be so terrible.

My coop is currently swinging by roughly 3-7 C (6-15 F) from day to night, depending on the weather (from sunny vs cloudy; wind speed/direction; outdoor temperature. Remember I have 3 popdoors open, each probably 3-4x the size of most peoples' popdoors). Not all of that is boost from the solarized run, though; even on cloudy days it swings this time of year just because of varying outdoor temps. It levels out somewhat in late winter, b/c the building's 'bones' have cooled down, at which point the solarized run is presumably a stronger contributor to fluctuations, but I have no reason to believe my solarized run has ever boosted the temp by more than 7C *maximum*, that's about 15+ degrees F.

If I were setting it up in a smaller coop -- well actually I expect I will next year, as I need to build a separate turkey shed -- I would arrange for more thermal mass to be more-directly influenced by the heated air, so that more of the heating goes into the heat sink for nighttime and less into the coop air. But these are details that each person can work out for themselves, and depend a lot on the particular structure and management of an individual coop.

Pat

 

[Mr. Peepers]

At an approximate latitude of 40 degrees N, the lowest latitude at which heating a coop might reasonably be considered necessary, a good mid-January day will give about 6.5 hrs of sunlight available for solar heating. A 1 meter square pop can heater operating at the maximum efficiency generally accepted for solar collection will collect about 80 watts of solar energy per hour. Assuming that 100% of that energy could be transferred/stored for warming the coop (in actuality, it would probably be more like 20%), that would mean that you'd get something like 520 watt-hrs of heating. This figure equates to the same effect as running a 20 watt light bulb all day. Of course you could build a half dozen pop can heaters and get the same effect as running a 120 watt bulb, but then you do get into a little complication and expense.

As latitudes get higher and/or skies get more cloudy, solar heater performance is even worse. In actual practice heating performance would probably be far worse than the figures above indicate. A pop can heater is a fun science project, and may have practical applications in some situations, but the numbers demonstrate that it's just not that practical for heating a chicken coop.

Don't get me wrong. In many applications, solar heating works well. For many years all the hot water in my home was solar heated. At the time I lived at a lower latitude in a sunny climate where such an application was practical. I wouldn't rely on solar heat for hot water in the winter in Manitoba. I guess my point in all of this discussion is that there are practical as well as impractical applications for solar technology. Advocating the impractical applications doesn't help anyone and will discourage many from seeking out those applications that might truly be worthwhile.