• Post Reply Bookmark Topic Watch Topic
  • New Topic
permaculture forums growies critters building homesteading energy monies living kitchen purity ungarbage community wilderness fiber arts art permaculture artisans regional education experiences global resources the cider press projects digital market permies.com all forums
this forum made possible by our volunteer staff, including ...
master stewards:
  • Nicole Alderman
  • r ranson
  • paul wheaton
  • Jocelyn Campbell
stewards:
  • Devaka Cooray
  • Burra Maluca
  • Miles Flansburg
garden masters:
  • Dave Burton
  • Anne Miller
  • Joylynn Hardesty
  • Mike Jay
gardeners:
  • Bill Crim
  • Pearl Sutton
  • Greg Martin

passive garden heater  RSS feed

 
master steward
Posts: 26342
Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
  • Likes 4
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
This is an idea I have shared with others for about six years, but I don't think I have created a thread about it.  

The idea is to create something like a 40 foot deep well with steel casing.  But it's dry.  No water.  And then mount a 4 foot tall steel cap-ish thing that has glass on the south side.  (note, the glass must not block any light (as most exterior glass does))  And then there is a 3/4 inch black anodized tube that is exposed to the glass at the top and travels to near the bottom of the "well".  

When the sun shines, the tube pulls air from the bottom of the hole - thus the air temperature for the whole 40 feet is relatively homogenized.   This warms the area 40 feet down in the summer.   At night, the air in this pipe stratifies - so the warmest air is at the top.  

When the sun shines, the stuff at the bottom is heated.   All the rest of the time, the warmest air moves to the top.  

If this works, the heat from the summer will slowly be given off through the winter.    So maybe something like 50 to 60 degrees is slowly given off.

If this doesn't work, then then the temperature, around here, that deep will be something like 45 degree year round - so the heater will constantly give a temperature that is warmer than freezing.  

I know of some homesteaders that use a technique like this to keep animal waterers from freezing.  The idea is to upgrade this to try and store even more heat.


Here are my feeble images to try to "paint a picture" of what I am suggesting.
passive-garden-heater.png
[Thumbnail for passive-garden-heater.png]
cased hole, tube and glass
passive-garden-heater-sun1.png
[Thumbnail for passive-garden-heater-sun1.png]
add some sun
passive-garden-heater-sun2.png
[Thumbnail for passive-garden-heater-sun2.png]
the heat on the tube pulls cold air from the bottom
passive-garden-heater-sun3.png
[Thumbnail for passive-garden-heater-sun3.png]
so the warm air moves down to displace the cold air
passive-garden-heater-sun4.png
[Thumbnail for passive-garden-heater-sun4.png]
that warm air will eventually get to the bottom of the hole
passive-garden-heater-sun5.png
[Thumbnail for passive-garden-heater-sun5.png]
now the bottom of the hole can be heated much more
passive-garden-heater-moon1.png
[Thumbnail for passive-garden-heater-moon1.png]
when the sun goes down, the heat from the bottom goes to the top
passive-garden-heater-winter.png
[Thumbnail for passive-garden-heater-winter.png]
in winter, the heat from the bottom heats the stuff at the top
 
Posts: 293
Location: Rural Unincorporated Los Angeles County Zone 10b
30
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
That's a sound idea because it'a based on a valid physical principles. I wonder if a Solatube might work as a cap for the well.



It's an efficient light gathering lens from all directions as the Sun moves. A section of reflective tube could extend down into the well and could have small perforations near the top to let the hot air escape.




 
steward
Posts: 4490
Location: Zones 2-4 Wyoming and 4-5 Colorado
391
bee books forest garden fungi greening the desert hugelkultur
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
So you would surround the top part with something like a horse trough and the water would not freeze?

What other applications can you see it being used for ?

I am wondering if it might help heat a small greenhouse?
 
steward
Posts: 3050
Location: Northern WI (zone 4)
644
books food preservation hunting solar trees woodworking
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I like this idea too.  I think Travis Johnson uses a culvert buried vertically below stock tanks to deice them.

I think the sun hitting the glass would need to heat the small tube more than it heats the casing.  Otherwise both will get hot and the air won't move up or down the small pipe.  If the top of the casing was lined with something reflective (aluminum trim coil, tinfoil), and the small pipe was black, then the light entering the casing would bounce around until it heats the small pipe, creating the airflow.

I bet the pipe would only need to go down 10' or so.  It would lose tons of heat to the surrounding soil.  Possibly it would lose all its heat.  In the winter you'd still get the stratification heating of the 45 degree deep earth (or 46 degree if the summer sun heat didn't all get dissipated).  

Arguably, what would happen if you just took a metal culvert, 2' in diameter, and sunk it vertically 10' deep with a cap on it at grade.  Possible bonus points if the bottom of the pipe found groundwater (more constant heat?).  Then at night the air at the top of the culvert would stay warmer (deep earth temp) and heat the soil right around the culvert.  Plant your growies one inch from the pipe in a circle and their roots may be kept warmer.  
 
paul wheaton
master steward
Posts: 26342
Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

Greg Mamishian wrote:That's a sound idea because it'a based on a valid physical principles. I wonder if a Solatube might work as a cap for the well.



Supposing that the anodized tube is still in the picture, I think it would be pretty good!  I think that exposing 4 feet of of southern exposure through glass would be even better.

 
paul wheaton
master steward
Posts: 26342
Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
  • Likes 2
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

Miles Flansburg wrote:So you would surround the top part with something like a horse trough and the water would not freeze?



That would be one possibility.   I am thinking that what I really want to do is grow a lemon tree, outdoors, in montana.

 
paul wheaton
master steward
Posts: 26342
Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

Mike Jay wrote:I like this idea too.  I think Travis Johnson uses a culvert buried vertically below stock tanks to deice them.



Do we have a thread here?


I think the sun hitting the glass would need to heat the small tube more than it heats the casing.  



agreed.


I bet the pipe would only need to go down 10' or so.  It would lose tons of heat to the surrounding soil.  Possibly it would lose all its heat.  In the winter you'd still get the stratification heating of the 45 degree deep earth (or 46 degree if the summer sun heat didn't all get dissipated).  



I agree that you can get most of the effect at just 10 feet.   But I am trying to shoot past harvesting the ambient ground temperature to making an attempt to SET the ambient ground temperature in this area.  

Maybe the first thing to do is a bit of an experiement.   With and without the annodized tube.   10 feet, 20 feet and 40 feet deep.  With a solar tube at the top, or something more elaborate.   And maybe something that is simply a metal cap.  



Arguably, what would happen if you just took a metal culvert, 2' in diameter, and sunk it vertically 10' deep with a cap on it at grade.  Possible bonus points if the bottom of the pipe found groundwater (more constant heat?).  Then at night the air at the top of the culvert would stay warmer (deep earth temp) and heat the soil right around the culvert.  Plant your growies one inch from the pipe in a circle and their roots may be kept warmer.  



I already have something kinda like that - a pump house.   All the plumbing does not break.   Now that I think about it - it has a metal lid, but I haven't thought to check it for snow in the winter.  I will try to be a bit more observant.
 
Mike Jay
steward
Posts: 3050
Location: Northern WI (zone 4)
644
books food preservation hunting solar trees woodworking
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

paul wheaton wrote:Do we have a thread here?

 Not a thread but a reply to a thread.  Here's a link to where Travis mentioned it in detail Who's using heated waterers?

I do like the idea of being able to set the ground temperature in the area.  I'm just not sure if that relatively small amount of sunlight will be able to overcome the thermal inertia and conduction of the dirt down deep.  I really don't know.  More experiments are needed!
 
gardener
Posts: 539
Location: Maine, zone 5
104
food preservation forest garden homestead solar trees wood heat
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

Mike Jay wrote:I'm just not sure if that relatively small amount of sunlight will be able to overcome the thermal inertia and conduction of the dirt down deep.  I really don't know.  More experiments are needed!



Experiments, experiments!!!  Mike, I like you're questioning about the energy balance issue and the rate of that small area's energy collection vs. the rate of the earth's ability to move that heat away.  But then I start thinking about an array of these that are active all year such that during the summer you get a large hot zone of soil that goes down fairly deep....how long will that hold in there?  Seems like a very interesting way to add to the microclimate of a space.  It makes me think more about the tefa thread and perhaps modifying the radiator idea a bit like such:
solar-enhanced-radiator.jpg
[Thumbnail for solar-enhanced-radiator.jpg]
 
Mike Jay
steward
Posts: 3050
Location: Northern WI (zone 4)
644
books food preservation hunting solar trees woodworking
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
That's a beautiful diagram Greg!  Is that the start of a new acronym?  GWPGRAYRPIESC?  What are the pebbley rectangles at the bottom of the pipes?  Wait... are they even pipes?

I like the array idea and using bricks as mass to hold the heat through the night (If I'm thinking the way you're thinking).  Would black bricks be better or glass on the South side?  I can see how having glass to suck in all the heat every day would be good.  Then again, having a black brick surface to radiate heat at night in the winter would also be good.

My hunch is that the energy balance of solar in vs earth heat moving would lead us to have shallower pipes in the ground.  If you can do twenty 10' pipes or five 40' pipes, I'm thinking the 10's would store the heat better in a more concentrated area.  Then as the earth sucks it away, it could be moving towards another pipe instead of into the depths.  Plus it would heat the roots of the lemons.  

I've realized that if you use a pipe (vs a stack of blocks), the digging part isn't that hard.  Assuming you have sandy soil, a post hole auger will make an 8" hole as deep as you want (straightness not guaranteed).

If you hit groundwater first, does that present an opportunity?  If the ground water is at a nice temp (say 45 degrees) and you sink the array of pipes down into it, would you have a permanent source of 45 degree air for the array?  And then the pipes wouldn't need the glass or the internal circulation riser pipe?  
 
Posts: 465
Location: 4b
70
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I would think you are going to need a real grid of pipes,  say 5 pipes by 5 pipes or something to overcome the heat loss. I can't believe a single pipe surrounded by earth would be able to keep any heat for any length of time. I think it would lose all its heat almost immediately after the sun stops hitting it.  You may be able to plant a tree in the middle of a grid of pipes with enough room between them for the tree roots to grow through and still be able to access enough water. I think Mike's idea of shorter pipes being more efficient is accurate.  If you keep the pipes the same size,  they are going to collect a certain amount of heat from the sun,  and the longer they are,  the more ground to suck the heat away. I would be interested in trying it with even shorter pipes than mentioned,  say down to maybe 4 feet long.  It would be interesting to see where the sweet spot occurred,  but my guess is that would change constantly dependent on the amount of sun on any given day.
 
Mike Jay
steward
Posts: 3050
Location: Northern WI (zone 4)
644
books food preservation hunting solar trees woodworking
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Oh, one more thought.  If the plants being protected drop their leaves in winter, the pipes could be really close together with the plant's branches intertwining around the pipes.  Then in winter the pipes would get sunlight and radiate it mere inches away from the branches.  In summer the heat isn't needed so the shaded pipes just hibernate.

This concept would mainly apply with dormant trees and arrays that don't/can't store summer energy for winter use, OR pipes that tap into ground water for their heat and don't need direct sunlight.
 
Greg Martin
gardener
Posts: 539
Location: Maine, zone 5
104
food preservation forest garden homestead solar trees wood heat
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

Mike Jay wrote:That's a beautiful diagram Greg!  Is that the start of a new acronym?  GWPGRAYRPIESC?  What are the pebbley rectangles at the bottom of the pipes?  Wait... are they even pipes?

I like the array idea and using bricks as mass to hold the heat through the night (If I'm thinking the way you're thinking).  Would black bricks be better or glass on the South side?  I can see how having glass to suck in all the heat every day would be good.  Then again, having a black brick surface to radiate heat at night in the winter would also be good.

My hunch is that the energy balance of solar in vs earth heat moving would lead us to have shallower pipes in the ground.  If you can do twenty 10' pipes or five 40' pipes, I'm thinking the 10's would store the heat better in a more concentrated area.  Then as the earth sucks it away, it could be moving towards another pipe instead of into the depths.  Plus it would heat the roots of the lemons.  

I've realized that if you use a pipe (vs a stack of blocks), the digging part isn't that hard.  Assuming you have sandy soil, a post hole auger will make an 8" hole as deep as you want (straightness not guaranteed).

If you hit groundwater first, does that present an opportunity?  If the ground water is at a nice temp (say 45 degrees) and you sink the array of pipes down into it, would you have a permanent source of 45 degree air for the array?  And then the pipes wouldn't need the glass or the internal circulation riser pipe?  



That acronym is catchy, isn't it?  But I think we'll need a few more letters before we're done!  The pebbley rectangles at the bottom represent coarse gravel.  I figured I'd want the water table to not rise above the gavel and into the masonry tubes that way the air can still circulate from side to side while still allowing the cold air to drop down to the ground water and exchange with it.  I want the water to not freeze and I figure the gravel would help with that too. I do think the ground water would help a lot.

I'm thinking I'll put the collumns about 4' apart and they'd be the size of 2 cinder blocks side by side, either with or without brick cladding.   Here's what I was thinking about for a grid:


radiator-array-overhead.jpg
[Thumbnail for radiator-array-overhead.jpg]
 
Greg Martin
gardener
Posts: 539
Location: Maine, zone 5
104
food preservation forest garden homestead solar trees wood heat
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Then I figured I could add more off from it to produce a larger grid:
Full-Radiator-Array.jpg
[Thumbnail for Full-Radiator-Array.jpg]
 
Greg Martin
gardener
Posts: 539
Location: Maine, zone 5
104
food preservation forest garden homestead solar trees wood heat
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
It's lots of work and some cash to get all the blocks, so I was thinking of trialing just 4 radiators surrounded by a wall of foil faced foam to see what happens over the coarse of a year.  Would love to see if citrus, figs, coffee or tea can make it.  What do you guys think....will this be an ok trial size?  Should be able to see some effect and measure it, no?  Anything else I should be considering?


test-set-up.jpg
[Thumbnail for test-set-up.jpg]
 
Greg Martin
gardener
Posts: 539
Location: Maine, zone 5
104
food preservation forest garden homestead solar trees wood heat
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I'm thinking figs might be the easiest.  They will drop their leaves and are relatively speaking hardy.  Hardy citrus and tea might be next easiest.  Not sure if coffee will make it, but would love it.  I was only planning on going down 6 feet with the pipes at my site by digging down somewhat and raising the soil level the rest of the way to make the 6 feet.  I was also thinking of digging out a walk way between the trees and filling it will coarse gravel that would also allow cold air to drop down in the paths to get it away from the trees...a sort of cold well design, perhaps extending that outside the cube to let the coldest air drain out of the cube....but not at all sure about that part.
 
Greg Martin
gardener
Posts: 539
Location: Maine, zone 5
104
food preservation forest garden homestead solar trees wood heat
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I guess the bonus with the tall perimeter wall, besides blocking the wind and giving off a bit of radiated stored heat, would be that it would keep out the deer.  I don't mind a bit of deer browsing, but I wouldn't miss that.  They definitely like browsing my in ground fig trees.
 
Greg Martin
gardener
Posts: 539
Location: Maine, zone 5
104
food preservation forest garden homestead solar trees wood heat
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

Mike Jay wrote:

paul wheaton wrote:Do we have a thread here?

 Not a thread but a reply to a thread.  Here's a link to where Travis mentioned it in detail Who's using heated waterers?



Thank you Mike!!!  Travis' post really gives me a lot of hope that the radiator array will have a good chance of working.
 
gardener
Posts: 455
Location: SoCal USA
71
bike cat dog tiny house trees
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
A form of this has been used with a house, I thought I saw a youtube video of it but it might have been a web page, but each end of a 100-200 foot long tube was black and inside a glass space, with a screen on each end to keep stuff out. One end was in a sort of chimney space and much higher up than the other end. The sun would heat up both ends, which would cause a natural draft, drawing the warm summer air through the tube and heating up the earth mass around the house. In the winter both ends were closed to prevent drawing cold winter air through which would cool the mass.

This is very similar to the PAHS system, except PAHS runs year round and there are 2 tubes, with one end outside and the other inside the house so that fresh air is cooled in the summer and warmed in the winter. It's something I would like to try including in my own home design, having these tubes going around the house several times under the waterproof, insulated "umbrella" that would extend out into the earth berm.
 
Greg Martin
gardener
Posts: 539
Location: Maine, zone 5
104
food preservation forest garden homestead solar trees wood heat
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

paul wheaton wrote: Maybe the first thing to do is a bit of an experiement.   With and without the annodized tube.   10 feet, 20 feet and 40 feet deep.  With a solar tube at the top, or something more elaborate.   And maybe something that is simply a metal cap.



Just curious Paul, for those depths would you use something like this to dig or do you have a better tool/method?

(Start at 6:20 in to skip past the dousing and get to the drilling)

 
Mike Jay
steward
Posts: 3050
Location: Northern WI (zone 4)
644
books food preservation hunting solar trees woodworking
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
That's what I'd use.  I've dug down to 14' with one and it was tolerable.  I'm guessing I could go to 20 without any help.  After that I'd probably rig up a tall tripod with a pulley.  Run a rope from the halfway point of the pipe to the pulley.  I can imagine that getting you to 30'.  I'm imagining 40' would require a pretty tall tripod or a different technique.
 
He was expelled for perverse baking experiments. This tiny ad is a model student:
Getting ready for the Better World Book kickstarter - February 2019
https://permies.com/t/99513/ready-World-Book-kickstarter-February
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!