Free heat

[Joel_BC]

I'm glad we had this conversation because I do see a small greenhouse in my future and I may incorporate something similar in the planning stages. Perhaps in conjunction with, or additional to, a soda can heater.
Things that make you go Hmmmm.

Yeah, I appreciate your willingness and interest in kicking ideas around. Thanks.

And I appreciate that you started this thread (re the soda cans).

 

[sunsaver]

Sorry to interject, but just wanted to note that in order for the antifreeze/water solution to circulate without a pump, the black collector pipes would need to be downhill from the radiant flooring of the greenhouse. Also, the pipes in the floor would need to spiral downward so that the water can sink as it cools. I also had another idea. What about making the southern wall of the greenhouse transparent or even better, one way mirror coated, and making the floor out of black pipes filled with antifreeze. You would still need to supplement with wood or gas heat on cloudy days, but the thermal mass of the floor might be enough to keep it above freezing on most sunny winter days. Just a thought.

 

[lighthawk]

Sorry to interject, but just wanted to note that in order for the antifreeze/water solution to circulate without a pump, the black collector pipes would need to be downhill from the radiant flooring of the greenhouse. Also, the pipes in the floor would need to spiral downward so that the water can sink as it cools. I also had another idea. What about making the southern wall of the greenhouse transparent or even better, one way mirror coated, and making the floor out of black pipes filled with antifreeze. You would still need to supplement with wood or gas heat on cloudy days, but the thermal mass of the floor might be enough to keep it above freezing on most sunny winter days. Just a thought.

Please do not apologize. Actually I was hoping you would join the discussion. In my opinion you are the most qualified on this forum. You might also know if a 12V DC pump can be operated just using a solar panel much as the fans on my window unit?
Also at builditsolar there arwe numerous thermosiphon projects which did you use. TIA.
Rich

 

[Joel_BC]

Sorry to interject, but just wanted to note that in order for the antifreeze/water solution to circulate without a pump, the black collector pipes would need to be downhill from the radiant flooring of the greenhouse. Also, the pipes in the floor would need to spiral downward so that the water can sink as it cools. I also had another idea. What about making the southern wall of the greenhouse transparent or even better, one way mirror coated, and making the floor out of black pipes filled with antifreeze.

Okay, well... This is an existing GH. It must go into service again in late March. The floor now is earthen. Above that are raised beds full of soil. Not an easy task to 'replace the floor'. Time, much effort, and some expense - for an idea that we're just tossing around. I certainly appreciate the thought you guys are putting into it, but as we're forced to admit here, it's all speculative. IOW, no northern climate R&D to base the gamble on.

Originally, when I started posting in this thread, I was thinking about an add-on: one of those soda-can collectors, attached to the south end as an enhancement of heat gathering during the shoulder seasons. That seemed easy enough to experiement with... a reform, rather than a revolution for my GH! The screen design sounded even potentially better (because a little more efficient).

 

[lighthawk]

All right you got me. I admit I have a tendancy to "overthink" things. That said every little thing you can do to retain heat will make a difference.
Something as simple as painting a plastic 2 litre bottle black and filling it 3/4 full with water can act as a heat sink. Black matte or black paint on the north wall would prevent sunlight from escaping and absorb it to warm the air naturally. Concrete block painted black in direct sunlight works as a great heat sink. Black weed block on the ground between the beds would also help absorb sunlight and warm the ground. Addition of a soda can or screen heater certainly can't hurt. I wish you luck and I could find myself in very similar shoes next season so I hope you will keep us updated with your choices and progress.
Rich.

 

[sunsaver]

12vdc pumps, fans, on other appliances are ideally suited for solar panels, because no inverter is need to convert to 110vac. However, its best to have the solar panels and batteries as close to the 12volt appliance as possible. This is because 12volt appliances typically run at higher current levels (amps). Ironically, a 12volt home such as an RV, is more likely to catch fire from an electrical overload than a 110vac system. A 12volt wired home needs to have very accurate gauges of wiring for this reason. My sunlight is quite a distance from my shade covered home, so i convert the solar power to 110vac before sending to the house so that i can use smaller, more affordable gauge wire. Also, i had already wired my home for 110vac, because i used to be on the grid like every other home in my nieghborhood. It was a simple matter of sending in the solar 110vac strait into the existing breaker box.
As for the thermosiphon type solar water heater, i posted detailed plans and a description of all of the parts i used. I'll look back at my old threads and see if i can find it.

 

[sunsaver]

Dunno. It's buried in my journal maybe or one of my old alternative energy threads.

 

[lighthawk]

Dunno. It's buried in my journal maybe or one of my old alternative energy threads.

Wasn't sure if I could find it in your journal. I am only up to page 3 I will keep looking. Thanks.

 

[hqueen13]

Alright, dragging this one out again. We're about to have to pay our own power bill after 4 years of being on somebody else's bill. That stinks! The other half and I are very much interested in this, but are pretty much building illiterate and handyman handicapped. Well, we just don't have much experience yet!
The directions on the Colorado Wind Power site are poorly written and vague for someone that is a real noob at this kind of thing.

So I've got a few questions and clarifications....

For the indoor box, if I read it correctly, you did not put any glass on the front. I am guessing that the glass serves to protect the cans/inside of the box from the elements?

Is the computer fan the only mechanism that propels the heated air into the room? Just want to make sure I understand the function of it.

In the original link to the Colorado Wind site, I don't really understand what he is talking about in photo 7. Is that black piece simply covering the gap left at the bottom of the cans, which would mean the air would be able to flow from one tube to the next? Or does that black piece plug the entire hole, essentially capping off the tubes?

It references that you can use cardboard or Styrofoam, are these ok to use despite the temps that the heater can reach? His example said that his thermometer went up to 130*! I don't want anything to melt or catch fire from the hot box!

Would it increase the effectiveness of the hot box if the cans were placed on a bit of an angle to the sun? Our house is south facing with deciduous trees, so we get really great sun in the winter. I wasn't sure if it was beneficial to slightly slope the face of the cans in order to improve the solar heat collection.

I noticed that it also commented about creating "ducts to the area you want heated". I assume this is primarily for use outdoors, or from the roof of a coop into the structure. How would one attach ducts? Could it be placed over the computer fan? I am wondering only because we have thermal drapes in our windows, and when it is below about 40, I usually keep them closed to retain the heat within the house. I am wondering if I had some sort of mini duct tube that could be placed between the curtains to vent the hot air into the room without opening the drapes. It might be beneficial for the days that are "partly sunny" or where the sun comes and goes a lot, when the sun is strong enough it would be pushing heat into the room, but when it isn't, the drapes would keep it from leaking out the windows again.

Thanks so much for helping 'splain things! We are so new at all of this, but are very excited about this project as it could really help save us money.

 

[lighthawk]

For the indoor box, if I read it correctly, you did not put any glass on the front. I am guessing that the glass serves to protect the cans/inside of the box from the elements?

You are correct. I did not use a glass front on the indoor unit as it fits snugly up against the thermopane. On an outdoor unit heat would escape by radiating out from the outside surface of the cans the glass prevents this heat loss.

Is the computer fan the only mechanism that propels the heated air into the room? Just want to make sure I understand the function of it.

Yep that is all it does. The brighter and more direct the sunlight the faster it turns.

In the original link to the Colorado Wind site, I don't really understand what he is talking about in photo 7. Is that black piece simply covering the gap left at the bottom of the cans, which would mean the air would be able to flow from one tube to the next? Or does that black piece plug the entire hole, essentially capping off the tubes?

It is to prevent the air from flowing up the front of the cans and forcing it to flow up through them. It doesn't matter if air flows from one tube to the next as long as it flows through them. On the indoor unit I did not drill a hole for air to enter. I left a one inch gap at the bottom the entire length of the unit.

It references that you can use cardboard or Styrofoam, are these ok to use despite the temps that the heater can reach? His example said that his thermometer went up to 130*! I don't want anything to melt or catch fire from the hot box!

I had the same concern so I used 1/4 inch luann backing.

Would it increase the effectiveness of the hot box if the cans were placed on a bit of an angle to the sun? Our house is south facing with deciduous trees, so we get really great sun in the winter. I wasn't sure if it was beneficial to slightly slope the face of the cans in order to improve the solar heat collection.

Yes it would help but then you would need to add a glass frontto the unit so it could stand alone.

I noticed that it also commented about creating "ducts to the area you want heated". I assume this is primarily for use outdoors, or from the roof of a coop into the structure. How would one attach ducts? Could it be placed over the computer fan? I am wondering only because we have thermal drapes in our windows, and when it is below about 40, I usually keep them closed to retain the heat within the house. I am wondering if I had some sort of mini duct tube that could be placed between the curtains to vent the hot air into the room without opening the drapes. It might be beneficial for the days that are "partly sunny" or where the sun comes and goes a lot, when the sun is strong enough it would be pushing heat into the room, but when it isn't, the drapes would keep it from leaking out the windows again.

The fan does not propell the heated air very far but a small section of duct to move the air past the curtains would work fine. 4" pvc drail pipe might work. Perhaps something as simple a a 3lb coffee can might work.
How you attach it would depend on what you use.
Hope this "splains" things a little better.
Good luck

Since I found that website there have been a huge number of design variations posted online. You may want to do a Youtube search for "pop can heater" Before you start you may find better instructions and designs that suit your needs better.