geothermal green house?

[Drexel]

I hope to start building a new home this summer and am planning on going with geothermal. While researching geothermal it got me to thinking. Why wouldn't a "passive" (for lack of a better term) closed loop system work for a greenhouse? By passive I'm thinking along the lines of burying X number feet of pipe about 8' deep near the greenhouse which would connect to pipe ran through the floor or walls, using a very small pump to move an antifreeze liquid through the system. I've looked on the net etc. but find nothing about such a system as I'm thinking of. The big unknown that I can think of is how much pipe (inside & outside) would be needed per cubic feet of greenhouse to keep it at say 40 degrees when the sun isn't there to help?
I'm posting this in hopes that someone has tried this before and could tell me how sucessful it was, or if it's even feasable. Living in Kansas 5 to 10 below zero is about as cold as we see, at least in the area I live in.

 

[theomodog]

Try looking here, This guy is in Alliance Nebraska sounds like he is doing something like what you are talking about.

Alternative Energy eMagazine - Heat From The Earth | AltEnergyMag

Mark

 

[dave1949]

Try looking here, This guy is in Alliance Nebraska sounds like he is doing something like what you are talking about.

Alternative Energy eMagazine - Heat From The Earth | AltEnergyMag

Mark

That's a nice greenhouse setup. As mentioned in the article, he had to divide his greenhouse space into tropical and northern areas to allow dormancy to occur.

I wonder if someone really into greenhouse gardening could give you a better idea of what temps are needed - based upon what & when you want to grow? That info is what really determines your design goal. I know JimmyJ is knowledgeable on this topic.

My impression is you get a goodly amount of sunshine year round in Kansas? If that is true, you may be over-engineering the heating requirements. It's possible with earth berming, some thermal mass like water barrels, and decent glazing - that may be all you need. Some greenhouses use an additional inside layer of plastic row cover during the coldest months.

The pros and cons of a heat system dependent greenhouse are a trade off to consider. If you depend on the heat system and it fails, not good. It costs something to install, maintain and run the heat system. If you have a system that will hold the correct temperatures all the time, it should increase your production. If I were going to spend any money on a heat system, I would want to end up with one that covers all my needs.
Dave.

 

[Drexel]

Very impressive results. I like the air flow idea but the cost of 6" pipe can get expensive very quick. 1" plastic pipe would be more in my price range. The reason I was favoring water as the heat transfer medium. Not sure if running pipe under a concrete floor would be better or running pipe in the walls. Maybe run the water through an "A" coil from an old ac unit with a fan behind it? A very small water pump should be able to keep the water circulating through the ground and greenhouse at a very low cost (maybe even from a solar panel).
We have a fair amount of sunshine days in kansas but we also have times when you don't see the sun for days at a time. I don't think this idea would work for warm weather plants such as tomatoes but for lettuce, broccoli and other cool weather plants I would think it possible to grow them year around.
For closed loop systems on homes I've seen estimates from 300' to 600' of pipe, but thats for a heating unit. Not sure these numbers would relate well to a system with no heating unit hooked to it.
I'll be busy on the house this summer, but was hopeing to trench for the greenhouse during the home construction and then build the greenhouse once i'm moved in.

 

[dave1949]

Very impressive results. I like the air flow idea but the cost of 6" pipe can get expensive very quick. 1" plastic pipe would be more in my price range. The reason I was favoring water as the heat transfer medium. Not sure if running pipe under a concrete floor would be better or running pipe in the walls. Maybe run the water through an "A" coil from an old ac unit with a fan behind it? A very small water pump should be able to keep the water circulating through the ground and greenhouse at a very low cost (maybe even from a solar panel).
We have a fair amount of sunshine days in kansas but we also have times when you don't see the sun for days at a time. I don't think this idea would work for warm weather plants such as tomatoes but for lettuce, broccoli and other cool weather plants I would think it possible to grow them year around.
For closed loop systems on homes I've seen estimates from 300' to 600' of pipe, but thats for a heating unit. Not sure these numbers would relate well to a system with no heating unit hooked to it.
I'll be busy on the house this summer, but was hopeing to trench for the greenhouse during the home construction and then build the greenhouse once i'm moved in.

Yeah, if you know you want a greenhouse and you are building, now is the time to put the structural/mechanical/electrical stuff in place. No doubt about that.

If you google 'earth-bermed greenhouse' you will get several hits. Amazon has a book on the subject I see.

Another thought may be to grow on benches and radiant/hydronic heat the bench surface. Warm soil, warm roots, warmth rising around the plants. If you have a cloudy spell with cold, or overnight, you can drape plastic over the bench.

Don't know about Kansas, but 90% of our really cold weather comes with clear skies.

My AC hydronic circulation pumps draw a max of .79A @115V. About 95W. Since you will have AC right there, be careful of the payback period on the solar panel and DC pump.

A temperature 'tempered' greenhouse allows you to extend the start and end of the growing season for things like tomatoes and peppers. That may be all you really need to do for home use. Beware of the $400 tomato
Dave.

 

[petes]

Beware of the $400 tomato
Dave.

Yeah, I just ate a $200 habanero pepper this week out of my 10' x 20' greenhouse. (in another couple weeks I'll have tomatoes, lots more peppers, lettuce, spinach and cabbage ready to eat so the cost per bite will soon come down!)

I swear each year I'll bury a gas line and buy a natural gas heater instead of using electric heat, but I haven't done it yet. That'd cut the cost to about a quarter of electric. I've also kicked around the idea of using ground source heat - extracting the heat from my well water and dumping it back into a return well... just hasn't made the top of the to-do-list.

 

[Drexel]

Yeah, I just ate a $200 habanero pepper this week out of my 10' x 20' greenhouse. (in another couple weeks I'll have tomatoes, lots more peppers, lettuce, spinach and cabbage ready to eat so the cost per bite will soon come down!)

I swear each year I'll bury a gas line and buy a natural gas heater instead of using electric heat, but I haven't done it yet. That'd cut the cost to about a quarter of electric. I've also kicked around the idea of using ground source heat - extracting the heat from my well water and dumping it back into a return well... just hasn't made the top of the to-do-list.

Sounds like my hunting & fishing trips. The $200 pheasant, the $200 bass. I think a lot of greenhouses fall in this category, I know this one will. But like the pheasant & the bass..it is fun.
I think the idea of heating a small greenhouse for pennys a day just appeals to my cheap nature