RMH to heat a bigger pit greenhouse

Hi everyone, and Happy 2015!
My name is Steve, and I live in Serbia. I recently started a red wiggler farm and am about to build a 8mx50m (26x165feet) valipini for the worms but also to start an organic vertical bottle garden.

Pro veggie growers here, use huge furnaces to heat water and then pump the hot water trough PVC pipes that are just layed on the floor of the greenhouse (although some others hang the pipes and just heat the air). I am looking for some info on heating a larger greenhouse using an RMH. I read a few books and understand the principle of an RMH.

The way I figure it, I have 2 options.

1. I can use the same principle as a typical RMH, using hot gases to heat a thermal mass. I would build a bigger RMH in the lower part of the greenhouse and then just lay the pipes in the ground trough the entire length of the greenhouse, so as the gases normally go upwards, they would heat the greenhouse air before they exit on the far end. However I gues it would need to be a very very big RMH and consume a lot of fuel.

2. option sounds more effective to me. I saw this video in youtube https://www.youtube.com/watch?v=YTnr8ua54Uw (check out 0:32)
So if I would do the same thing (probably would have to be bigger) and attach it to a system of pipes and have a water pump circle the water, that should be a good, effective way to heat the greenhouse.

Having in mind it's a valipini, shouldn't have to raise the heat too much.

Has anyone tried any of this? Any thoughts?

Stevan Covic wrote:Hi everyone, and Happy 2015!
My name is Steve, and I live in Serbia. I recently started a red wiggler farm and am about to build a 8mx50m (26x165feet) valipini for the worms but also to start an organic vertical bottle garden.

Steve : Happy 2015m and welcome to Permies! Wow, that is a huge greenhouse by any name, There is a problem with pit type green houses in that they make ideal places
for cold air to settle into, you need a plan to isolate your worm beds from this effect, if you had a large area at ether end to serve as Wood storage and air-locks you could
mitigate the effects of cold air spilling into your Greenhouse!

Share some information about your local type of Mediterranean climate and your elevation, Will this be heated for all of your winter, or are you trying to extend the
growing season at ether end !

With a Hanging garden (!?), you will need to heat the air as There will be much less buffering of the plants temperatures created by the warm earth ! Normally one of the
biggest benefits of an in ground RMH system is tempering of the swings in ground/air surface temperatures! Also the nearly unlimited options in number and size of heated
seed beds, that and being able to manage a cold snap by covering the young plants with row cover plastics - as this all happens inside your greenhouse - you don't have to
use valuable time in securing your row covers from winds or heavy rain, just drape and move on !


Pro veggie growers here, use huge furnaces to heat water and then pump the hot water trough PVC pipes that are just layed on the floor of the greenhouse (although some others hang the pipes and just heat the air). I am looking for some info on heating a larger greenhouse using an RMH. I read a few books and understand the principle of an RMH.

Let me reassure you that because of the freaky High Temperatures that The RMH burns wood at, we get a very efficient and clean burn, and your wood use will
be much lower than expected


The way I figure it, I have 2 options.

1. I can use the same principle as a typical RMH, using hot gases to heat a thermal mass. I would build a bigger RMH in the lower part of the greenhouse and then just lay the pipes in the
ground trough the entire length of the greenhouse, so as the gases normally go upwards, they would heat the greenhouse air before they exit on the far end. However I gues it would need
to be a very very big RMH and consume a lot of fuel.

1a )The biggest benefit of the RMH is its long term storage of heat, once the RMH has been run in the evening for several hours the slow radiation of heat off of your
thermal mass will help hold the ground and air temps within a temperature range that promotes plant growth !

Generally the 8 inch diameter RMH system is as large as is easily handled, horizontal runs of heat pipe through your thermal mass generally are limited to 50' With the new
style Horizontally loaded Batch fed RMHs, you may be able to stretch that to 75 feet, in ether case you will need a minimum of 2 RMHs which is more practical for the actual
heating loads of most Growing seasons Days/Nites

There is a common problem easily dealt with- During much of your heating season, in the evening when you wish to start a fire to recharge your Thermal mass, your green
house temperatures will be in the 12ºC - 16ºC Range, due to the Buffering Effect on temperatures by the soil in your Pit Greenhouse, Outside air Temperatures will have
reached a high of perhaps 20 -25ºC and you will have troubles getting Any heating device to Draft or Draw Well under these conditions, the longer the horizontal run within
your Thermal Mass, and the cooler that Mass is the greater the problem You will have, A quick solution is to have a inspection/Clean out ''T'' located at the base of the final
vertical chimney, this allows you to start a small hot paper fire to quickly warm up the system and get it to draw !

Horizontal piping buried in the Ground to heat the Thermal Mass will have to be protected from being stepped on and crushed


2. option sounds more effective to me. I saw this video in youtube https://www.youtube.com/watch?v=YTnr8ua54Uw (check out 0:32)
So if I would do the same thing (probably would have to be bigger) and attach it to a system of pipes and have a water pump circle the water, that should be a good, effective way to heat the greenhouse.

2a Using a water system ether requires a large holding tank insulated against heat loss, and pumps and valves to circulate hot water through several zones of the Green
house - or If you needed to save the room required for the hot water tanks mass, then the nighttime circulation of hot water would be accompanied by 1 or more dedicated
people to monitor and maintain the fire in your tankless system to transfer heat from one section of the greenhouse to the other, This type of Man power dependent Heat
energy delivery system would require being a self taught learner, and would be very hard to Automate, balancing future (early-morning?) heating requirements against firing
needs, Who ever gets selected for this job will not see many weekends holidays of during the heating season

Having in mind it's a valipini, shouldn't have to raise the heat too much. Has anyone tried any of this? Any thoughts

There are several Forum threads on RMHs in green houses and if you use the search function found in the Permies tool box at the top of the page You can easily find lots
more information.

As the Largest Permaculture group in the world you also have several Fellow Members from Europe to weigh in on this thread ! Good luck and Good hunting !

For the good of the Crafts ! Big AL

allen lumley wrote:
Steve : Happy 2015m and welcome to Permies! Wow, that is a huge greenhouse by any name, There is a problem with pit type green houses in that they make ideal places
for cold air to settle into, you need a plan to isolate your worm beds from this effect, if you had a large area at ether end to serve as Wood storage and air-locks you could
mitigate the effects of cold air spilling into your Greenhouse!

Hey Big All, thanks for the welcome.
The size of the greenhouse is my biggest issue. All permies usually talk about small, "family" sized greenhouses, not much info on commercial ones. 8x50m is a standard sized greenhouse for veggies, in these parts. I am not sure how the principles of a pit greenhouse apply for bigger ones, but we'll see..
The cold air settling will be a plus during Summer time. During Winter, a huge earthbag cob plastered wall will serve as thermal mass. I contemplated digging a cold air sink, but don't have the funds for the walkway right now.
I will start a thread on my walipini in the apropriate section, so we can continue the discussion there.

Share some information about your local type of Mediterranean climate and your elevation, Will this be heated for all of your winter, or are you trying to extend the
growing season at ether end !

Subotica is located in a plain, at an average of 115meters, no hills or mountains for 60 miles around. Here's some other info:
The climate here is mild, and generally warm and temperate. The rainfall in Subotica is significant, with precipitation even during the driest month. The Köppen-Geiger climate classification is Cfb. The temperature here averages 10.9 °C. The rainfall here averages 561 mm. At an average temperature of 21.1 °C, July is the hottest month of the year. At -0.5 °C on average, January is the coldest month of the year.


With a Hanging garden (!?), you will need to heat the air as There will be much less buffering of the plants temperatures created by the warm earth ! Normally one of the
biggest benefits of an in ground RMH system is tempering of the swings in ground/air surface temperatures! Also the nearly unlimited options in number and size of heated
seed beds, that and being able to manage a cold snap by covering the young plants with row cover plastics - as this all happens inside your greenhouse - you don't have to
use valuable time in securing your row covers from winds or heavy rain, just drape and move on !

About the hanging garden, I want to recycle plastic bottles and make a hanging garden for organic veggies on the north wall. (I'm in the northern hemsphere, so the south side gets the most sun. Eventually, I want to hook the vertical garden up to an aquaponic system, but that's another story..

1a )The biggest benefit of the RMH is its long term storage of heat, once the RMH has been run in the evening for several hours the slow radiation of heat off of your
thermal mass will help hold the ground and air temps within a temperature range that promotes plant growth !

Generally the 8 inch diameter RMH system is as large as is easily handled, horizontal runs of heat pipe through your thermal mass generally are limited to 50' With the new
style Horizontally loaded Batch fed RMHs, you may be able to stretch that to 75 feet, in ether case you will need a minimum of 2 RMHs which is more practical for the actual
heating loads of most Growing seasons Days/Nites
Ok, so I'll probably start with a 8" RMH and see how it goes. Your reference is to length. Keep in mind I have 8m with. So I guess I'll need more than one heat pipe in line, and that means a whole bunch of RMHs. That's why option 2 sounds better, but it will also need testing..

There is a common problem easily dealt with- During much of your heating season, in the evening when you wish to start a fire to recharge your Thermal mass, your green
house temperatures will be in the 12ºC - 16ºC Range, due to the Buffering Effect on temperatures by the soil in your Pit Greenhouse, Outside air Temperatures will have
reached a high of perhaps 20 -25ºC and you will have troubles getting Any heating device to Draft or Draw Well under these conditions, the longer the horizontal run within
your Thermal Mass, and the cooler that Mass is the greater the problem You will have, A quick solution is to have a inspection/Clean out ''T'' located at the base of the final
vertical chimney, this allows you to start a small hot paper fire to quickly warm up the system and get it to draw !

Horizontal piping buried in the Ground to heat the Thermal Mass will have to be protected from being stepped on and crushed

Don't understand how the outside temp during Winter will be 25C!? But I get what you meant about the draft problems. I will keep that in mind when designing the RMH.

2a Using a water system ether requires a large holding tank insulated against heat loss, and pumps and valves to circulate hot water through several zones of the Green
house - or If you needed to save the room required for the hot water tanks mass, then the nighttime circulation of hot water would be accompanied by 1 or more dedicated
people to monitor and maintain the fire in your tankless system to transfer heat from one section of the greenhouse to the other, This type of Man power dependent Heat
energy delivery system would require being a self taught learner, and would be very hard to Automate, balancing future (early-morning?) heating requirements against firing
needs, Who ever gets selected for this job will not see many weekends holidays of during the heating season

The room is not an issue. I would like to use sawdust pellets so I can make an automated, or batch feeder. I figure, the pellets being equal size and weight, it would be easier to fine tune the draft so that I can fill a batch in the evening and leave it till morning.

There are several Forum threads on RMHs in green houses and if you use the search function found in the Permies tool box at the top of the page You can easily find lots
more information.

As the Largest Permaculture group in the world you also have several Fellow Members from Europe to weigh in on this thread ! Good luck and Good hunting !

For the good of the Crafts ! Big AL

Thanks for all the advice, I am roaming the forum still, and have already read the "simillar threads". I will try to give back to the forum by posting all my progress and conclusions..

Stevan : I am sending some eye candy your way, this is the only green house operator who was successfully mated a D.I.Y. Pellet feed to a Homebuilt RMH .

I am sending you there to look at the rocket, don't blame me if you get lost and lose a couple of hours .

P.S. There is a LOT of Crap out there on you-tube, please be very cautious and use due diligence .

I was using an extreme Temperature spread, Bright sunny spring days can create a local micro climate in front of south facing structures with daytime highs
created around 3pm.

This can be followed by bitter cold nights with zero cloud coverage ! So- About the time you are starting to make your evening fires to provide maximum heat
storage and heat radiation through the coldest hours of the night - The outside temps can be higher than the inside temps, causing problems with creating draft !

For the Good of the Crafts Big AL

Great, but where's the link? There's only a thread on feeding chickens

Thanks for the explanation. I get it now

Stevan Covic wrote:Great, but where's the link? There's only a thread on feeding chickens

Thanks for the explanation. I get it now

https://www.youtube.com/user/web4deb

Steve : Link Below :

https://www.youtube.com/user/web4deb/playlists

For the good of the crafts ! Big AL

Thanks guys. I saw this a few months ago, and then spent yesterday watching almost all of the videos

His solution seems to do an awesome job, but I will have to go a slightly different path, because I will be using briquettes instead of pellets. I am active in a association for disabled kids, and recently they started a project with a wood chip briquette maker. So the kids will have work related therapy in the briquette making center. I will probably be getting the briquettes from them.
They are approximately the size of a hockey puck, so I thought of making a feed tube slightly wider than the briquette. If I layer them inside the tube, they shouldn't clog up. I can make a 1 or 2 meter feeding tube and position it so it releases one or maybe two briquettes at a time. That way I can create a small but intense flame.
I already picked up some details form the videos that hadn't occurred to me before. Apart from the feeding tube, the rest I will do as shown in the videos.

You mention feeding the fire through the night, but the point of the RMH is to make a hot fast fire which gives its heat up to a storage mass for slow release. With 8" or so of cob around the duct, you woun't get the new heat coming out for about 8 hours after you start the fire; then it will radiate continuously for many hours after that. So you don't need to meter your fuel for slow release. I understand you are planning on these briquettes, but the people who use wood in a batch box load a full batch, let it burn for an hour or so until it is gone, then load another batch if the heating needs will require it. Experimenting with briquettes loaded in a batch box may be advantageous, as it will require no mechanism or power to run.

I understand how the RMH was conceived. I just want to apply the principles in a different way.
Yes, the advantage is thermal mass, and it's good when you heat a bench or smaller area. If I make a standard RMH and place 160 foot exhaust trough a thermal mass, I doubt I could get it warm enough with just one batch of wood or pellets.
Or, if we go with the second option (which I think will eventually be the solution), I would discard the thermal mass portion of it, and use the RMH to heat water (like they did on Zaytuna farm). Even then, by the time my heated water circulates trough a number of pipes going up and down the greenhouse, by the time it comes back it will be cold. I believe this "loss" of heat from the RMH itself, would cool it down very fast if the fire was out. That is why I believe I would need a constant feed, because the area to be heated is just huge.

The main reason why I am going with an RMH is because standard furnaces loose a lot of the heat trough smoke. RMH has much better way of using all the generated heat from the fumes. Big Al believes I will probably need more than one RMH. Only testing will show the way to go..

I still think you will benefit from a mass storage system, as there will be many nights on the edges of winter when you need heat, but less than the system generates. You can't turn a rocket stove down to a trickle and have it still run efficiently; you will at some point get smoke and build up creosote in the ducts, which will eventually catch fire when you are running hard and possibly damage the system. Mass will let you coast through the milder nights with a short fire, while not hampering operation in cold times.

You may be right and I am not excluding thermal mass. I thought of running the exhaust just bellow the worm bins, giving them "floor heating". But again, I fear that by the time the gases reach half of the greenhouse they will cool down, so half of the worm bins will be heated, and half would remain cold. But I will test multiple options. I guess it remains to be seen which approach will work best.

However, I am sure it will not be "a trickle". I expect that the RMH will have to work full power all the time. I just want to have an automatic feed so I don't have to sit there all the time adding "fuel" to the fire.

If the RMH is powerful enough to heat the greenhouse in cold times, it will be too powerful to run well in mild times when you still need some heat. There is a thread on the facebook RMH group about the same kind of setup, where he is thinking of double opposed RMHs with the ducts running from opposite ends of a long bench. This would even out the heat over the whole length.
https://www.facebook.com/groups/rocketmassheaters/

Stevan Covic : i found this site where another person is attempting the sawdust to hockey puck brickets, and am sharing here !

Link below !

http://www.ecosnippets.com/diy/how-to-make-bio-fuel-briquettes/

Hope this is useful and timely ! Big AL

Interesting concept Glenn, Thanks for sharing. I will definitely have to try different variations before I cob everything up, and this concept might be useful. I will definitely give it a try.

Allen, those are exactly the ones I had in mind. As I've said, my NGO did a project and got a brickete making machine, and it's fully operational. It's just a press. You feed the sawdust trough a huge funnel and it compresses it into brickets. I am hoping that if I place those bricketes one on top of the other in a long pipe, they will not clog up. I've held the bricketes in my hand and they tend to chip off easily. I am worried that if they chip while I'm putting them in the tube, they will clog up.
Remains to be seen..

And build a small test batch box to see if you can load them directly in there (in stacks or piles or...?) without them falling apart, and if they burn well

Glenn Herbert wrote:And build a small test batch box to see if you can load them directly in there (in stacks or piles or...?) without them falling apart, and if they burn well

Stevan, i think this is best advice!

Have you ever built a rocket?

I would say i am on my 6 or 7th iteration of several rockets, over the course of three or four years. I think i get the hang of it by now. I mean i understand thoses better now.

And only now i am ready to start a real build, full scale, bells and whistles (duh, no whistles ) etc!

No. I have never built one before. I watched guys assemble a ceramic heating stove (typical for these parts) that is reinforced with cob.
I am not even sure when I will be able to start. I am hoping to get some testing done this spring, but it all depends on whether I finish my greenhouse in time.

Glenn, I am hoping to use a metal tube, or pipe, as a batch feeder. I think, if I can find a pipe that is a little wider then the bricketes, I can stack them inside and provide a stable source of fuel. As the one in the burn chamber burns away, the next one falls out. I am hoping that the draft will be so good as not to allow flames going up the feed tube.

Stevan Covic wrote:

Glenn, I am hoping to use a metal tube, or pipe, as a batch feeder. I think, if I can find a pipe that is a little wider then the bricketes, . As the one in the burn chamber burns away, the next one falls out. I am hoping that the draft will be so good as not to allow flames going up the feed tube.

Steve : Yes Probably ! Much like that great piece of advice on deep kissing, remember you are sucking on a tube over 30' long mostly full of semi digested food

Inorder to get the great efficiencies of a rocket stove we are trying to get and maintain firebrick surface temps and re-radiation in the 1100º +C range, that means
that you only have the temperate of the incoming air flowing by the end of your feed tube to cool the feed mechanism! Generally this is not a good place for metals
of any kind

Fellow Member Rob T. --> web4deb, is the only one who has successfully felt with this issue, and his plans require frequent replacement of metal parts

For the Good of the Crafts! Big AL

I just stumbled upon this.. it seems there is a guy in my country building RMHs for greenhouses commercially. Here is the add. You probably won't understand it but you can see the pics.

http://www.kupujemprodajem.com/Raketna-pec-17785245-oglas.htm

The guy claims that for 4 hours of burning it will radiate heat for the next 12h, and keep a 175 square meter greenhouse at 18 C. (that's about 1800 square feet, at 64 F)