Heating my Greenhouse

[Joe Bifano]

I had an idea on how to heat my greenhouse and wanted to know what you all think.

 

I was going to get a pellet stove insert from a friend for free and started to brainstorm. I have a greenhouse that measures 24x64' and it has 17' high ceiling in the center.  It is way to big to heat the whole thing so I had an idea on how to heat just some parts of it.

 

With the pellet stove I was thinking of making another room, inside the greenhouse, out of plastic and maybe a thermal blanket. I want to maybe put the plastic on some rafters that come across the greenhouse at 10' high and enclose a space that would be just for tomatoes about 8' wide and 64' long.  Put the pellet stove in that area and see what I get at night. I would roll up the thermal blanket during the day and drop it at night.  I could do the same thing above instead of using the plastic so I get a higher R-value.

 

Also if the thermal blanket idea would not get enough R-value I had another idea on using 2 pieces of plastic creating a air space. Then using a woodworking cyclone add static free peanuts to it creating a pocket of peanuts to make a high R-value filling in the walls and ceilings.  Then in the daytime vacume it all back out to a large container or feed siloh.

 

Your thoughts.

[Johann]

How many BTU's does the Pellet stove have?

What kind of greenhouse is it?

My  "wonderwood " woodstove is a 135,000 Btu stove and it will heat my house with the lowest heat setting very easy.

I know a house got way better insulation, but a greenhouse does not need that high a temperature either.

I never found a insert that will put a lot of heat out. My freestanding wood stove is very efficient to run and uses only about $ 10 per week of wood I have to buy. Pellets would cost more money.

If you use 2 layers of plastic with an air-space in between, this air-space would act like an insulation. This could do the trick and you may be able to heat your greenhouse enough to grow tomatoes.

But you would need a duct system or fans to distribute the heat throughout the greenhouse.

You may also run your exhaust pipe from your pellet stove inside the greenhouse for about 20-30 feet before exit the pipe for heat exchange. I do not know how much creosote, pellets will build up inside the exhaust pipe of the pellet stove.

[TCLynx]

I think the reason many people like pellet stoves is the even heating they can get with minimal feeding since they usually have an auto feed so depending on the stove it may only require filling and attendance once or twice a day rather than every so many hours to put in more wood as with many other wood stoves.  Also I think some pellet stoves have been set up to burn other things instead of just wood pellets, like corn or cherry pits or whatever is approximately the right size and shape.

 

Another option that I've heard of is using in floor hydronic heating.  If you insulate under the floor and run tubing in the floor you can run water through a boiler and pump it through the tubing in the floor for radiant heating, this may be adaptable to work with a stove that is already heating the air as well in the greenhouse.

[Joe Bifano]

After a lot of discussions and work I have come to a conclusion on how I will heat this greenhouse. I laid everything out in the greenhouse where I was going to have my deep water rafts and installed a R15 plastic on the ground and up the sides of the rafts. Then installed PEX just on the ground. In the fish tanks that are buried in the ground the same thing, R15 bottom sides and ends then PEX in the same place.  Each fish tank and raft has a smart valve that is connected to a large variable speed pump that is connected to a traditional hot water heater. You can not use anything else for small BTU loads.  All Tank less Hot water heaters will not go low enough. If you have just one raft calling for heat and it only requires 2000 BTU's the tank less style heaters will cycle and not go off at all. Only a Hot water heater will work.  Now when they all go off the Hot water heater I have will take care of everything.

 

The next thing I want to do is add in line with the setup a wood or pellet boiler, not a stove. Then during winter I will heat everything as far as the rafts and tanks but the greenhouse as well. The Hot water heater is not going to go on until the wood boiler runs out of fuel and will only be a backup. The boiler would have 2 pumps one for the setup for rafts/fish and one for the inside of the greenhouse. That way my hot water  heater will not have to deal with the inside because it just will not have the capacity to do it. The greenhouse will need 200,000 or more BTU's to keep it at 68 degrees at night. If I do not grow tomatoes then the heat would be far less and the boiler will not need to be going as much.

 

Here are the differences between a wood boiler and pellet boiler.  Wood is free for me on my property and surrounding area. I just have to go get it. So if I pay someone or myself then their are labor costs. In a large wood boiler you do not have to split the wood. If it can handle 3 foot long pieces then cutting it to 3' will be fine. With wood you start it up in the evening and let it go till morning. If it is cloudy/snowy day then load and do it again. Maybe 2 to 3 times all day including the last nigh load. The only thing that you have to do to keep the extra heat is build in a large storage tank. Then when heat is needed it can come from storage. As far as I know there is no wood boiler that can start up when heat is needed and shut down when no heat is needed so that is the reason for the large storage tank. The wood boilers can be expensive and the extra storage tank is another cost. But the wood can be reasonable if you can cut it and it is free to get.

The pellet boiler is a hopper style that has 15 bushels of pellets, cherry pits, corn or bio fuel. It also has the ability to have a silo style hopper next to it that can auger in more fuel. This has capacity's for an entire season of heating so you do not have to fill in anything. A pellet boiler will start up when there is a call for heat and shut down when there is no call for heat. No extra storage is needed.  Yes the cost of buying wood pellets is what it is, and a lot more than what I pay for my wood.. BUT you can make your own pellets. In the BIO fuel pellets process you can make grass, cardboard, paper, switch grass, weeds of any kind, pine cones, pine needles and of coarse wood. If you purchase, an extra cost, the pellet making equipment you can run a greenhouse all day, all night and all year without loading anything except a large hopper. If you get an auger it will auger it to the top of the hopper when you are making the pellets. Auger it to the boiler has needed. Then you just have to make sure your augers are working and pellet boiler is working.

 

Picking the best solution is up to you.  I am going to look at the pellet style for my operation because I want the automated approach. I also think I can sell pellets and even make other kinds of pellets to sell from my equipment purchase. 

 

 

[Manross]

We actually created a system like this a friend’s barn.

 

He heats his barn with radiant heat from the energy stored in 55 gal drums of softener salt at night.

 

He burns wood during the day and has a copper coil over the flue with glycol circulating through it.

The heat in stored the salt drum, then at night the flow is reversed and the salt drums heats the barn until morning.

 

We created a computer system to control it.

He gets heat from #1 solar panels (first), #2 wood stove (second), and as emergency backup #3 propane.

 

Jeff (New B) Manross

 

Chi Ma said:

I wonder if you could heat up 55 gallon drums full of sand for thermal mass.

[Manross]

Here is a pellet maker: http://www.makeyourownpellets.com/

very easy to get the lawn and garden scraps people leave on the curb for the trash man.

make your own pellets from someone elses trash... love it. 

[Susie Gehri]

Joe....

Thats a huge greenhouse. AWESOME!!   I have a much smaller one, that I'm heating with a Rocket Stove!  

First I studied Rocket Heaters, or Rocket Stove Heaters.  They are amazing.  Not the cooking type, but the type that heats a home.  (They use about 1/4 the amount of wood a wood burning stove uses.)  Google: Hermon Rocket Stove Heater. 

 

Then, after studying "thermal mass" and searching for a way to most efficiently heat my greenhouse, I learned that "water" has 4 times thermal mass as stone, or cob or brick.  Folks make "cob" benches for home heating Rocket Stoves that holds and releases heat, so I thought, how about using water instead of cob? It holds and releases 4 times what cob does!  So....with the ol wheels turnin' I thought, "how can I use a rocket stove and heat large quantities of water to heat the greenhouse"?

I came up with, instead of "cob" around the stovepipe, lay steel 55 gallon barrels filled with water on top of a "U" channel that contains the stovepipe and use the heat from the stovepipe to warm the water in the barrels.  That hot water in the sealed barrels will release warmth all night long.  So...thats what i'm doing.  Pellet stoves are sort of a pain, and everyone I know thats gotten them, eventually change them out.  Do some research on Rocket Stoves on Google. The stove pipe on a large Rocket Stove can be 40-60 ft long!  You can make it larger by using 'brick' as in the Hermon Heater, instead of a 55 gallon barrel one, that most use for Rocket Stoves.  Hope this helps.

[Joe Bifano]

Hi Susie,

 

I am not using a pellet stove but will be using a pellet boiler which is a big difference. Plus making my own pellets gives me the ability to use waists and products that are lying around this area for years.After buying a pellet making set up all of my waists again and items to make my pellets are free. It is automatic as far as going on and off.

With a rocket stove you still need to put wood into it. How long can a rocket stove heat at night with one load in it? Can you load wood automatically. I do not want to keep putting in wood all day and night long to keep a lot of 55 gallon barrels heated.

How many barrels do you have for your greenhouse? How big is your greenhouse? How cold does it get at night in your area?  What is the average temperature at day and night?Then after I get this info I can compare to what I have here and see. If i have 65' of pipe and 55 gallon barrels on top of the pipe how much growing space do I loose? If I expand to 5000 or 10000 square feet greenhouse how many barrels do I need and how much growing space do I loose?

With all of the rafts and fish tanks in the 1500 square foot greenhouse I will have over 10000 gallons of water.  The hot water heater I am using will keep this water at 75 degrees. With 10000 gallons at 75 degrees I will have plenty of thermal mass to keep my plants warm and will not use but 1/4 capacity of the hot water heater. In the start up of getting them all to 75 degrees I will need the hot water heater to do a little at a time. How could a rocket stove heat my fish tank water and raft water to 75 degrees? My water needs to be warm so the roots get warmed so they grow way more than the air needs to be warmed.

The amount of room the barrels take up and the manual feeding of wood and the ability of heater water is not there so it would not work at all for this situation.

Susie Gehri said:

Joe....

Thats a huge greenhouse. AWESOME!!   I have a much smaller one, that I'm heating with a Rocket Stove!  

First I studied Rocket Heaters, or Rocket Stove Heaters.  They are amazing.  Not the cooking type, but the type that heats a home.  (They use about 1/4 the amount of wood a wood burning stove uses.)  Google: Hermon Rocket Stove Heater. 

 

Then, after studying "thermal mass" and searching for a way to most efficiently heat my greenhouse, I learned that "water" has 4 times thermal mass as stone, or cob or brick.  Folks make "cob" benches for home heating Rocket Stoves that holds and releases heat, so I thought, how about using water instead of cob? It holds and releases 4 times what cob does!  So....with the ol wheels turnin' I thought, "how can I use a rocket stove and heat large quantities of water to heat the greenhouse"?

I came up with, instead of "cob" around the stovepipe, lay steel 55 gallon barrels filled with water on top of a "U" channel that contains the stovepipe and use the heat from the stovepipe to warm the water in the barrels.  That hot water in the sealed barrels will release warmth all night long.  So...thats what i'm doing.  Pellet stoves are sort of a pain, and everyone I know thats gotten them, eventually change them out.  Do some research on Rocket Stoves on Google. The stove pipe on a large Rocket Stove can be 40-60 ft long!  You can make it larger by using 'brick' as in the Hermon Heater, instead of a 55 gallon barrel one, that most use for Rocket Stoves.  Hope this helps.