Has anyone ever done a DIY geothermal A/C?
 

My Bio-Diesel Garage is going to be in need of A/C soon. I have a dehumidifier in there now; but when things warm up I'd rather just cool and dry it than just dry it.

I would like to do everything I can to keep the project as green as posable; but the budget is slim (especially with fuel prices low).


So here's the Idea Take an old window unit build a water tight box around the condenser, put a submersible pump at the bottom on one side and the return on the other. I could also silicone a series of walls to both sides of the condenser forcing the water to flow in an S shape many times . . . I'm thinking about using typical horizontal in ground loop using coils of tubing. My garage is in a 3.5 acre field so space is absolutely no issue.

Looking at
5,000 btu Window unit $ Free (already have)
Fountain pump $30
water tight box $30
Tubing $200 ?? EDIT: Just found 100' of 3/4" Polyethylene tube for $17 at lowes so 500' is $50http://www.lowes.com/lowes/lkn?action=productDetail&productId=24166-000000150-24166&lpage=none
Excavator rental $200 ??

So under $400 for a Geothermal cooler. Payback would still be pretty long but at that price point I'm willing to absorb it.

Any Ideas? Comments? Modifications? Reasons it won't work?

Please no "Just buy a commercially produced system and pay someone to install it" that is way out of the price range I'm looking at for this project.

Damn; I was hoping for some discussion.

I did have a good Idea for testing; 55 gallon barrels of water to replace the ground loop (just for testing/ short term).

If you have a stream flowing past, or a beach, or the aquifer has flow through it, you might not need a pump, as the water comes to you courtesy of Mother Nature.

That would be super sweet, unfortunately our aquifer is around 100 feet; ground water can be found at 10~20' though . . .

Going by the post on the other thread I think I'm going to give it a go with barrel testing. I just acquired another free window unit of questionable quality going to try that one out first.

Then you're in excellent shape: Rent one of those 2-stroke augers to drill down to the ground water, to a depth ~10' below the water table, making a couple of holes laterally separated by ~50' to ~100'. Or, Google for "driven well point," available at home improvement centers and hardware stores for ~$50. Pump water up out of one hole, pass it through the heat exchanger, then drain back down the second hole. If your'e in Lousisana, soil is probably pretty sandy and wet, with ground temp ~60ish, which is perfect. This will provide all the heat and cooling you'll ever need, assuming your place has decent insulation.

For the barrel test, I suggest immersing the heat exchanger at the bottom of the barrel, making sure that there is adequate space around it for the water to circulate by convective heat transfer (Google for it), as works with an old fashioned room radiator.

Once the barrel test works out, you could simply bury the barrel in the yard, below frost line, then route the tubes to/from the wells into/out of the barrel. The barrel itself with also radiate or absorb heat through its skin into/out of the surrounding soil, effectively increasing the size of the heat exchanger. Since water is ~800 times denser than air, and since the ground water at your place is probably just about perfect temp, you oughta have lots of free heat and cooling.

I have access to an auger for the tractor no problem, but I may need to make some sort of extension; might be 6 feet max now. . . .



Soil here is high clay, but where the clay isn't it is sandy.

Where my camp is (15 miles east) is blackjack.

My well water temp is 63~68 depending on season.



Actually no insulation at the moment; but very well sealed. I will be hanging sheet rock and filling the 2x4 walls with cellulose before the cooling season comes around.

Garage is 200 square feet, asphalt roof, metal walls concrete slab floor.

I don't want to get ahead of myself but the house with the same setup would be killer.

My "Plan" is to leave the condenser in place, building a box around it and pumping the water around it, I prefer the submerged idea, but then I'd have to re-charge the a/c unit.

No frost line here :-) Buried barrel/s sounds like a good idea to me. Best part is that way I would have x btu's pre transfered.


Heat would be cool also :-) Do you happen to know if the Heat/ Cool window units are heat pumps, or just heat strips?


I'm getting excited

If it's a heat pump, I think to heat it absorbs heat from the air or whatever medium (i.e., ground water), and to cool it disperses heat to that medium. So, it heats or cools by running forwards or backwards, and if your unit is a window heat pump (as opposed to an air conditioner) you're good to go. On reflection, an AC should be essentially the same, cool outta one side and heat from the other.

The underground container should be metal (preferably aluminum), which conducts heat vastly better than wood or plastic. Concrete is pretty good, too. The container and pipes are, in effect, extensions of the heat exchanger, so you'd want to insulate that portion carrying the heated or cooled product to the house.

Your 68 degree ground water temp is excellent for heating, could be better for cooling.

Plant deciduous trees to provide shade in summer, yet allow sunlight to the house in winter. In addition to shade, a tree is a wonderful air conditioner, as it draws hundreds of gallons of water from the soil, then evaporates it into the surrounding micro-climate, dissipating heat via latent heat of evaporation, just as your skin does with perspiration. That's the principle behind those atrium fountains the ancient Romans and Moors used--fountain sprinkle evaporates and cools the surrounding air.

The Chinese have a tree that makes small berries which are excellent fuel, being mostly oil, that could be burned in winter in a wood pellet stove. Your county ag extension agent could help with particulars.

Paint the building white, as white reflects sunlight and infared/ultraviolet energy much better than dark colors. A light-colored roof is a major advantage in the Sun Belt. Home improvement stores also sell perforated reflective foil to put in attics or under shingles, which reflects energy away from the interior (or back into it). Cheap to install during original construction, but a pita after.

Best to keep the building from getting too hot in the first place, rather than then trying to expel heat from the building after the heat gets in. Indigenous or "cracker" architecture in the South was developed from keen insight and experience long before the days of the air conditioner, with lots of good passive methods to keep cooler, such as higher ceilings, attic fans, white paint, etc..

In colonial Williamsburg VA, they ate ice cream in August, a century before electricity or air conditioning existed, by preserving winter ice in an ice house, buried below ground and insulated with straw. Seems to me, such ancient technology could be applied today.

The unit(s) that I own do not heat; I've never seen an operational unit that did have heat, What I'm wondering is if anyone knows if the window units with heat are heat pumps, or if they just put some resistive coils in the airflow and called it a heater.
If they are heat pumps I'd be happy to go out and buy a new one, if they just have resistive coils then I'll just stick with what I've got.





Metal would definatley be better, but plastic barrels are free to me, and I think that 2 plastic would beat out 1 metal in my fairly low load situation.

I'm still trying to figure out if 30 deg ground temp would be best for cooling/ 100 deg ground temp for heat. Obviously if you had that situation you would skip the compressor, but as a mental exercise I'm trying to wrap my mind around the concept that colder/ hotter (to the max) is best, or is not.


No fires allowed in bio-diesel production shed; Hundreds of gallons of Vegetable oil, 55 gallons of Methanol, various other flamable materials around.

Not a bad Idea; just not for this situation.

Already white walls; red roof. I like it that way. My house has a painted white roof though.


Definitely was a big difference in the house.

I'm not sold on the stuff just yet; but I may have to try it out.

Primary purpose of the system is actually to dry out my process water; the cooling is just a great by-product; my energy is going mostly in to leak sealing; but for a living space; absolutely.

If your primary purpose is to dry out water, why not run a dehumidifier instead of cooling down the entire area? I'm sure the dehumidifier could be augmented with a heat pump as well.

I just have a dehumidifier now; works fine, but in the summer it would be much nicer to have cooling as well.

Now that I'm thinking about it I realy don't need heat but for 5-10 nights per year just to prevent freezing.