Surprisingly good result from the natural thermosyphon. With a fan, have you considered the counter intuitive option of ducting the warmer air from the top of the greenhouse down through the compost and out at floor level? That way you will be recovering heat and warming the coldest air in the greenhouse to protect the plants. In England, some Victorian greenhouses had a large under floor area filled with lots of compost material. By comparison, your compost bin looks tiny. How many days do you estimate you will get heat before the compost cools down?
BackwoodsBungalow yes, I agree! Great idea to vent the warm air at floor level. If I had more space in my tiny greenhouse I’d try it. Sadly you are also correct about the limitations of my small pile. I’m estimating 3 weeks at reasonably high temperatures (100 deg F or higher). I’m going to try aerating with a drill auger to see if I can salvage the heat. Hopefully I’ll be able to limp through the last hard freezes.
A compost pile of this size will last between 2 and 4 weeks (above 100 deg F/40 deg C). Unfortunately the size of my compost pile is limited. I may try to expand UP next year to get more volume.
@@MorganBrown It depends on the "fuel" you put in. Dan Brown wrote a nice book books.google.fr/books/about/The_Compost_Powered_Water_Heater_How_to.html?hl=fr&id=pKZwAwAAQBAJ&redir_esc=y#v=onepage&q&f=false From differents experiments it seems that a very carboned substrate with differents size of bits, from sawdust to chunks passing by "schredded chips" last the longer, until around one year ! depending of the size, some were made inside insulated boat container.. (the best system for me !) Very informative book !
Yes, but the results are neglible for such a small system. Geothermal is great, but you have to go big (relative to the size of your greenhouse). th-cam.com/video/ch0VD-_9Xxc/w-d-xo.html
you will extract more heat in the short term, but the pile will cool faster. And the more tubes you have inside the pile, the harder it is to turn the pile. Best solution is probably to have a pile so large that you don't need to turn it over the course of a winter. Then you can put more tubes in the pile and it will be fine. I don't think my wife would have approved, had I built a giant pile in the backyard! I needed a small farm.
Interesting that you could get a 10 degree rise with only 2 1/3 yards, and with such a short heat exchanger. I think I'll give my own idea that we discussed a go. I was discouraged by hearing everyone say "water carries heat much better than air". While "they" are quite correct, it involves the technical complications you mentioned. Thanks again for going to the trouble of doing this.
Yes, I was very pleased with this result. The high conductivity of the aluminum duct certainly helped heat transfer. Unfortunately, the compost pile is just too small, probably by a factor of 4. The pile only stays hot for about 2-3 weeks without a full turn. And turning this compost pile was essentially impossible (my own fault there). Some type of easy-to-turn small compost pile would be a real innovation.
@@MorganBrown Speak of easy-to-turn small compost pile, I managed to build a reactor which is only 0.28 cubic meters in volume. It reached 64 degrees Celsius within 24 hours after the materials are put in.(Ambient temperature is 28 to 32 degree Celsius) And I also managed to keep it above 45C for more than 30 days by adding new materials into it. Here's a summarizing video I made :th-cam.com/video/hWEspeI20ZU/w-d-xo.html
I realize this is 2 yrs old but one input or variable you didn't cover was the core temperature of the compost. Id really like to know that part of it.
Hehe I’m still alive 😂 This compost mixture easily hits the max temp of 140-160…but it is too small to stay hot for long, maybe 1-2 weeks. That’s the fatal flaw. Either I come up with a way to turn this pile, or I make the pile about 4x larger. If you have a farm, the big pile is doable, but for the rest of us, some innovation is required to turn the pile.
@@MorganBrown i just find out about this hot composting stuff. If things work out I may have a chance to try it in about 2 yrs. I have no experience but have been going over this and working on it in my offgrid notebook. 2 things I would implement is a mid level shaker pipe made from drainage pipe. In your system maybe a 3/4" pvc with holes drilled in the center. Use a removable cap or valve on the intake side. The other thing is do is make it a closed loop system. Why keep heating super cold air? Instead, draw the intake from the floor off your green house but not too close to the warm air discharge. Just some thoughts , good luck
@@jim55282 I'm not sure if you were proposing this, but I tried having air holes in the heat exchanger (inside the compost pile) and it was a big mistake. Biggest issue was that the compost pile dried out around the pipe, and the entire pile pretty quickly got cold. A lot of that moisture ended up in the greenhouse, where it just created trouble (condensation, ice, mold, fungus). In my experience with (small) compost piles, aeration is VASTLY overrated! The biggest concerns with small piles are insulation and moisture preservation. I have easily gotten 160 degree temperatures from nearly airtight compost piles. Aeration seems to be more of an issue for industrial-scale compost applications. You could certainly make this a closed loop with a much longer section of dryer vent laid through the greenhouse, acting as a pure radiator. I actually did this in the previous year's compost heat exchanger. Unfortunately, some condensation actually filled the pipe and air stopped flowing! So you'd need to account for that problem (not difficult). However, one very nice thing about the application shown here is the natural thermosiphon - I get excellent airflow and heating without adding a fan (purely passive heating). I think for a closed loop you would need to carefully ensure that air is flowing in the loop...or include a duct fan (a simple 12 watt fan will suffice)
Thank you for sharing this information. I'm designing a heat exchanger for my greenhouse with a similar design (using compost) but you've given me more to think about. My greenhouse is 8'X10' and my compost ben will be 4'X4'X4' (covered), and I plan to insulate it as you did on all sides except the side that touches the greenhouse, there I will use corrugated metal to radiate inside the greenhouse. What do you think instead of using ridged dryer pipe I use 4" PVC pipe? That way I could make bends (turns) with elbows inside the compost pile giving me more heated air volume to pull into the greenhouse.
Ron, sorry, I did not see this comment until now. The 4 inch PVC pipe would be more durable for sure. It won't conduct as much heat as the aluminum dryer duct, but it will still work. One problem with having a lot of complicated pipe inside the compost pile is: how to you turn the compost? I'm keen on desigining a compost bin that allows for much faster turning. My previous compost piles have simply been too difficult to turn. Since they are not very big, they cool down after a month or so. If you want a compost pile that stays hot all winter, it will have to be huge (more like 8x8x8 feet)
@@MorganBrown Thanks for the info. I didn't get mine completed before winter. My wife and I both got sick so it's been on hold. Hopefully before spring.
@@ronjohnson8684 haha, yeah, I had Covid when I made this video (mid March 2020). Sadly we sold the house and moved to a townhouse without much of a private yard. My days of compost heating may be over, but hopefully I still get to do some gardening. Have been busy fixing up the house for now. ;-)
I have a 49 sq/foot 8' tall poly greenhouse with 15 feet of duct down to 5 feet and get 55f constant. I am added a slightly smaller box than yours with emerg foil blankets lining with poly then put my indoor air through that plus a void at 5 feet as storage. I'm in 8b Vancouver Canada use it for citrus. You had same concept with results thanks!
that's great to hear. Vancouver seems like the perfect place to implement a lot of these types of passive heating & cooling. And if you're doing citrus...you are succeeding! I was able to keep a tomato plant bearing fruit until December 15 one season, which was my sole greenhouse triumph. haha
@@MorganBrown Still lucky I have space for trees inside though. I'll at least have cooler air in summer. No AC option but solar and will double poly wall it in winter. My yard is 1907 fill so has rocks to heat and sandy loam. The citrus needs seasonal cues or they may go dormant under indoor lighting.
It strikes me that all heat extraction compost systems i've seen, are based on a vertical stacking of the material. Heat is moved by water in tubes or air movement. Direct radiation is ignored or underused in general. A lot of work is needed to stack and excavate the compost. However, if you assume that compost moves down by it's weight and acts as a slow fluid, things change. Why not angle the compost pile in order to let the compost flow down, remove compost from the bottom and fill up at the top. Use a corrugated steel roofing sheet under an angle of let's say 45 degrees, as an heatexchanger. Sides and top of the slanted pile are only for aeration, insulation and guidance.The steel will/can radiate the heat into the GH. I don't have enough compost material avail to put it to the test in my attempt for a passive solar GH. At this moment I'm using thermal mass to keep the GH above freezing (water and insulated brick footings). Last 2 winters lowest outside temp overhere was -10 C at ground level. My system relies on capturing solar heat during the day and storing enough to keep the temp above freezing during night. A long clouded period shows max temp in GH drops to max daily outside temp. During a day with max sun, temp in GH rises 20 C above outside temp. Ran a test last winter with lettuce in the GH: transplanted them in fall at size of 5 cm into pots with poor soil, but they did develop leaves of 15 cm. Stay safe, best wishes, greetings from Holland.
Earl Shine I like your idea for a compost “feeder”. Seems like you could definitely use gravity to aid in the turning of the compost. My current system is not very “turning friendly”, and I will probably be unable to actually turn it. I’ll have to disassemble. I actually have some galvanized steel sheet metal sitting in my garage for like 5 years. The wife is dying for me to get rid of it! It seems like any compost pile will have a shell of about 20-30 cm of cool material before you reach the hot core. I think you need to access the core of the pile to get meaningful heat extraction. I’ve studied many successful passive greenhouses and I think that the principles you mention are more important than compost. Quality construction, insulation, thermal banking, etc. I do like compost as a backup for sunless days, as you mention.
Good idea. But why don't you try to put the hot air exchanger - fan in opposite side of the green house. I think the cold air pipe sucks the most of hot air .
Why keep the compost gasses out. If the compost has good aerobic decay going on it should produce CO2 and not methane. Some commercial growers add CO2 to their greenhouse to increase growth.
If you duct the gases into the greenhouse, run them through a filter of woodchips or straw or something. That will absorb the ammonia and some moisture, but the co2 will pass. Then toss the saturated straw onto the next compost pile.
water has the highest insulation value. all you need to figure out is how much tubes you can run throught that compost vs speed of flow. this will tell you your threshold of max BTU output . dont use air use water.
too complicated. Here, I just put a pipe in the compost and the heat transfer happens without any supplemental equipment. If I was going to use water, I'd need: 1) a network of fragile water pipe inside the compost, 2) a water reservoir inside the greenhouse, 3) a strong pump pushing the water. A single pin prick hole in your water pipes and you have a soggy mess. A pin prick hole in my heat exchanger is no big deal at all. I've seen these guys with the huge compost piles circulating water. Funny how they never show you "season 2", since after they deconstruct the compost pile, I'm positive that their water circulation pipes are a mess and full of holes. If you've got an industrial-strength application, then sure, water circulation could be great. But if you have a small compost pile and want to pull some heat out of it, I very much like this extremely simple air circulation system.
@@MorganBrown Use water lines (cheaper & easier) under the (posibly insulated from the bottom) compost pile which still enables you to "turn the pile" any time as you wish or cycle various piles. Thermosphoning will also proceed very effectively with water vs air. Having the cooling end of the thermosyphoning loop at a high elevation will increase the force (powered by gravity: the greater the density difference & the greter the elevation difference) thus speed thus effectiveness/efficacy of thermosyphoning/heat transfer. The ‘cooling end’ of the cycle can be a radiant heater above the plants which will be very effective.
This is exactly what I needed to see!!!
...now I'll be adding it to my greenhouse in VA!
Thank you!!!
Don't forget to make that compost pile BIG!
Surprisingly good result from the natural thermosyphon. With a fan, have you considered the counter intuitive option of ducting the warmer air from the top of the greenhouse down through the compost and out at floor level? That way you will be recovering heat and warming the coldest air in the greenhouse to protect the plants. In England, some Victorian greenhouses had a large under floor area filled with lots of compost material. By comparison, your compost bin looks tiny. How many days do you estimate you will get heat before the compost cools down?
BackwoodsBungalow yes, I agree! Great idea to vent the warm air at floor level. If I had more space in my tiny greenhouse I’d try it. Sadly you are also correct about the limitations of my small pile. I’m estimating 3 weeks at reasonably high temperatures (100 deg F or higher). I’m going to try aerating with a drill auger to see if I can salvage the heat. Hopefully I’ll be able to limp through the last hard freezes.
Fascinating. How long do you expect to get out of the compost before it begins to cool and cure?
A compost pile of this size will last between 2 and 4 weeks (above 100 deg F/40 deg C). Unfortunately the size of my compost pile is limited. I may try to expand UP next year to get more volume.
@@MorganBrown It depends on the "fuel" you put in. Dan Brown wrote a nice book books.google.fr/books/about/The_Compost_Powered_Water_Heater_How_to.html?hl=fr&id=pKZwAwAAQBAJ&redir_esc=y#v=onepage&q&f=false From differents experiments it seems that a very carboned substrate with differents size of bits, from sawdust to chunks passing by "schredded chips" last the longer, until around one year ! depending of the size, some were made inside insulated boat container.. (the best system for me !) Very informative book !
What about the geothermal portion, did it work?
Yes, but the results are neglible for such a small system. Geothermal is great, but you have to go big (relative to the size of your greenhouse). th-cam.com/video/ch0VD-_9Xxc/w-d-xo.html
Would adding another line , like 2 of those lines going thru be worth it?
you will extract more heat in the short term, but the pile will cool faster. And the more tubes you have inside the pile, the harder it is to turn the pile. Best solution is probably to have a pile so large that you don't need to turn it over the course of a winter. Then you can put more tubes in the pile and it will be fine. I don't think my wife would have approved, had I built a giant pile in the backyard! I needed a small farm.
Interesting that you could get a 10 degree rise with only 2 1/3 yards, and with such a short heat exchanger. I think I'll give my own idea that we discussed a go. I was discouraged by hearing everyone say "water carries heat much better than air". While "they" are quite correct, it involves the technical complications you mentioned. Thanks again for going to the trouble of doing this.
Yes, I was very pleased with this result. The high conductivity of the aluminum duct certainly helped heat transfer. Unfortunately, the compost pile is just too small, probably by a factor of 4. The pile only stays hot for about 2-3 weeks without a full turn. And turning this compost pile was essentially impossible (my own fault there). Some type of easy-to-turn small compost pile would be a real innovation.
@@MorganBrown Speak of easy-to-turn small compost pile, I managed to build a reactor which is only 0.28 cubic meters in volume.
It reached 64 degrees Celsius within 24 hours after the materials are put in.(Ambient temperature is 28 to 32 degree Celsius) And I also managed to keep it above 45C for more than 30 days by adding new materials into it.
Here's a summarizing video I made :th-cam.com/video/hWEspeI20ZU/w-d-xo.html
@@gitpharmmakes7985 very interesting result! I guess insulation is the key factor
@@MorganBrown I agree with you. Here's the original design which is tested in Ireland: th-cam.com/video/dP20LkAZJIc/w-d-xo.html
I realize this is 2 yrs old but one input or variable you didn't cover was the core temperature of the compost. Id really like to know that part of it.
Hehe I’m still alive 😂
This compost mixture easily hits the max temp of 140-160…but it is too small to stay hot for long, maybe 1-2 weeks. That’s the fatal flaw. Either I come up with a way to turn this pile, or I make the pile about 4x larger. If you have a farm, the big pile is doable, but for the rest of us, some innovation is required to turn the pile.
@@MorganBrown i just find out about this hot composting stuff. If things work out I may have a chance to try it in about 2 yrs. I have no experience but have been going over this and working on it in my offgrid notebook. 2 things I would implement is a mid level shaker pipe made from drainage pipe. In your system maybe a 3/4" pvc with holes drilled in the center. Use a removable cap or valve on the intake side. The other thing is do is make it a closed loop system. Why keep heating super cold air? Instead, draw the intake from the floor off your green house but not too close to the warm air discharge.
Just some thoughts , good luck
@@jim55282 I'm not sure if you were proposing this, but I tried having air holes in the heat exchanger (inside the compost pile) and it was a big mistake. Biggest issue was that the compost pile dried out around the pipe, and the entire pile pretty quickly got cold. A lot of that moisture ended up in the greenhouse, where it just created trouble (condensation, ice, mold, fungus). In my experience with (small) compost piles, aeration is VASTLY overrated! The biggest concerns with small piles are insulation and moisture preservation. I have easily gotten 160 degree temperatures from nearly airtight compost piles. Aeration seems to be more of an issue for industrial-scale compost applications.
You could certainly make this a closed loop with a much longer section of dryer vent laid through the greenhouse, acting as a pure radiator. I actually did this in the previous year's compost heat exchanger. Unfortunately, some condensation actually filled the pipe and air stopped flowing! So you'd need to account for that problem (not difficult). However, one very nice thing about the application shown here is the natural thermosiphon - I get excellent airflow and heating without adding a fan (purely passive heating). I think for a closed loop you would need to carefully ensure that air is flowing in the loop...or include a duct fan (a simple 12 watt fan will suffice)
Thank you for sharing this information. I'm designing a heat exchanger for my greenhouse with a similar design (using compost) but you've given me more to think about. My greenhouse is 8'X10' and my compost ben will be 4'X4'X4' (covered), and I plan to insulate it as you did on all sides except the side that touches the greenhouse, there I will use corrugated metal to radiate inside the greenhouse. What do you think instead of using ridged dryer pipe I use 4" PVC pipe? That way I could make bends (turns) with elbows inside the compost pile giving me more heated air volume to pull into the greenhouse.
Ron, sorry, I did not see this comment until now. The 4 inch PVC pipe would be more durable for sure. It won't conduct as much heat as the aluminum dryer duct, but it will still work. One problem with having a lot of complicated pipe inside the compost pile is: how to you turn the compost? I'm keen on desigining a compost bin that allows for much faster turning. My previous compost piles have simply been too difficult to turn. Since they are not very big, they cool down after a month or so. If you want a compost pile that stays hot all winter, it will have to be huge (more like 8x8x8 feet)
@@MorganBrown Thanks for the info. I didn't get mine completed before winter. My wife and I both got sick so it's been on hold. Hopefully before spring.
@@ronjohnson8684 haha, yeah, I had Covid when I made this video (mid March 2020). Sadly we sold the house and moved to a townhouse without much of a private yard. My days of compost heating may be over, but hopefully I still get to do some gardening. Have been busy fixing up the house for now. ;-)
I have a 49 sq/foot 8' tall poly greenhouse with 15 feet of duct down to 5 feet and get 55f constant. I am added a slightly smaller box than yours with emerg foil blankets lining with poly then put my indoor air through that plus a void at 5 feet as storage. I'm in 8b Vancouver Canada use it for citrus. You had same concept with results thanks!
that's great to hear. Vancouver seems like the perfect place to implement a lot of these types of passive heating & cooling. And if you're doing citrus...you are succeeding! I was able to keep a tomato plant bearing fruit until December 15 one season, which was my sole greenhouse triumph. haha
@@MorganBrown Still lucky I have space for trees inside though. I'll at least have cooler air in summer. No AC option but solar and will double poly wall it in winter. My yard is 1907 fill so has rocks to heat and sandy loam. The citrus needs seasonal cues or they may go dormant under indoor lighting.
It strikes me that all heat extraction compost systems i've seen, are based on a vertical stacking of the material. Heat is moved by water in tubes or air movement. Direct radiation is ignored or underused in general. A lot of work is needed to stack and excavate the compost. However, if you assume that compost moves down by it's weight and acts as a slow fluid, things change. Why not angle the compost pile in order to let the compost flow down, remove compost from the bottom and fill up at the top. Use a corrugated steel roofing sheet under an angle of let's say 45 degrees, as an heatexchanger. Sides and top of the slanted pile are only for aeration, insulation and guidance.The steel will/can radiate the heat into the GH.
I don't have enough compost material avail to put it to the test in my attempt for a passive solar GH. At this moment I'm using thermal mass to keep the GH above freezing (water and insulated brick footings). Last 2 winters lowest outside temp overhere was -10 C at ground level. My system relies on capturing solar heat during the day and storing enough to keep the temp above freezing during night. A long clouded period shows max temp in GH drops to max daily outside temp. During a day with max sun, temp in GH rises 20 C above outside temp. Ran a test last winter with lettuce in the GH: transplanted them in fall at size of 5 cm into pots with poor soil, but they did develop leaves of 15 cm.
Stay safe, best wishes, greetings from Holland.
Earl Shine I like your idea for a compost “feeder”. Seems like you could definitely use gravity to aid in the turning of the compost. My current system is not very “turning friendly”, and I will probably be unable to actually turn it. I’ll have to disassemble. I actually have some galvanized steel sheet metal sitting in my garage for like 5 years. The wife is dying for me to get rid of it! It seems like any compost pile will have a shell of about 20-30 cm of cool material before you reach the hot core. I think you need to access the core of the pile to get meaningful heat extraction. I’ve studied many successful passive greenhouses and I think that the principles you mention are more important than compost. Quality construction, insulation, thermal banking, etc. I do like compost as a backup for sunless days, as you mention.
I love the idea of a renewable pile as opposed to one I need to completely tear down regularly....
Good idea. But why don't you try to put the hot air exchanger - fan in opposite side of the green house. I think the cold air pipe sucks the most of hot air .
Tomas Jokubauskis good idea
Why keep the compost gasses out. If the compost has good aerobic decay going on it should produce CO2 and not methane. Some commercial growers add CO2 to their greenhouse to increase growth.
Fair enough. My main concern isn't gas, but moisture. I want the moisture to stay in the compost pile, not in the greenhouse.
Morgan Brown . Yes, would cause fungus issues and the like.
If you duct the gases into the greenhouse, run them through a filter of woodchips or straw or something. That will absorb the ammonia and some moisture, but the co2 will pass. Then toss the saturated straw onto the next compost pile.
water has the highest insulation value. all you need to figure out is how much tubes you can run throught that compost vs speed of flow. this will tell you your threshold of max BTU output . dont use air use water.
too complicated. Here, I just put a pipe in the compost and the heat transfer happens without any supplemental equipment. If I was going to use water, I'd need: 1) a network of fragile water pipe inside the compost, 2) a water reservoir inside the greenhouse, 3) a strong pump pushing the water. A single pin prick hole in your water pipes and you have a soggy mess. A pin prick hole in my heat exchanger is no big deal at all. I've seen these guys with the huge compost piles circulating water. Funny how they never show you "season 2", since after they deconstruct the compost pile, I'm positive that their water circulation pipes are a mess and full of holes. If you've got an industrial-strength application, then sure, water circulation could be great. But if you have a small compost pile and want to pull some heat out of it, I very much like this extremely simple air circulation system.
@@MorganBrown Use water lines (cheaper & easier) under the (posibly insulated from the bottom) compost pile which still enables you to "turn the pile" any time as you wish or cycle various piles. Thermosphoning will also proceed very effectively with water vs air. Having the cooling end of the thermosyphoning loop at a high elevation will increase the force (powered by gravity: the greater the density difference & the greter the elevation difference) thus speed thus effectiveness/efficacy of thermosyphoning/heat transfer. The ‘cooling end’ of the cycle can be a radiant heater above the plants which will be very effective.