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PaddyKevin 02-23-2010 03:08 PM

Geothermal: DIY- Would This Work?
I have no engineering or other related education training or aptitude, so I am probably missing a key here. I would be most grateful if you can tear me apart, since my feeble mind cannot see why geothermal cannot be a simple diy project. Thanks so much for your critisisms folks

It seems to me that we might be talking apples and oranges, not in the use of geothermal but in the efficiency of the product. My thinking is that we may be able to do a diy job to get benefit from this source of energy but that it would not be the great return that a pro job would give. Now this trade off is to be considered in light of the great differences in cost the professionally installed vs the diy project would involve. Still with me here?

The exchange of heat

My understanding is that the basics of this is that:
1. the temperature of the air in the house is at a different temp than the liquid from the ground
2. the principle is that when these two meet the basic physics is that the two “banks” try to equalize out, or go to the same temperature.
Am I right there?

The two banks

My vision is a loop or tubing running underground and a separate loop of tubing running in the house so that, before the two loops meet, they are at different temperatures. This to me is just restating the foundation of the whole system. Do I have this right?

The interchange of the two banks

Now, if we bring the two loop systems together, they will by their own magical powers try to modify each other, so that we wind up with an end product that is not as warm as the warmer one and not as cold as the colder one. Right?

Can this interchange be as simple as weaving the house loop over and around the loop from the ground, so that the two loops (here it would be copper tubing since it is the most conductive, right?) come into as much contact as possible. If this interaction is in a closed and insulated unit then it should be the most efficient. Right?

My thought on this unit would be to build a bench at the back of my garage and insulate it then run a length of insulated, perhaps 6” diameter pipe through it. The copper tubing would run through that pipe.

I just have no idea how much intersection is needed here. Perhaps it would have to be the entire rear wall of the garage, insulated on both sides to improve efficiency?

The in ground loop

From what I have read, this is a major key to the effectiveness of the whole system. We need to have the external loop in a proper location so as to be in an area with constant temp and an area where the transfer of temperature from the home will not impact the temperature of the surrounding area so as to negate the benefit of routing the loop through the ground. This later concern is one of the reasons why we need to have long sections under the ground, with the other reason being the volume of the liquid pumped through the system depends on the cubic area in the home we seek to moderate. Right?

Running Water

If we can tie into subterranean water then we have the benefit of constant heat normalization by the moving water taking with it the temperature difference that was brought in by the loop after it passed through the house. This assumes that the water into which our unit is placed is itself at a constant temperature, as would the ground be beyond a certain depth. Right?

Most of us in suburbia do not have streams or ponds in our yards into which we can place the loop. But here comes my insane idea.

We in suburbia do have a water line coming into the home, and I also have a drainage system running around the yard, a number of feet down, to drain the water from what would be the water table mark. Suppose we take advantage of this but wrapping the ground loop around, or perhaps just under these piping systems? This is what I am the most excited about. The water would serve to eliminate the constant flow of different temperature provided with the “used” liquid as it flows through the outer loop.

Well, there you have my craziness. I do have some other questions.

First, assume I use one of the small pond pumps to move the liquid through the system, is there a way to figure out the size of the pump (gallons per minute) that I need?

Second, how do I attach the pump? I know that there is one end that has a nipple onto which tubing is placed, but the intake part is usually a large area.

Third, for economy, I would use black plastic pipe under grounds as much as possible. I would try this in my 20 x 20 or so garage first, so I think one 400 foot line might be enough. I keep reading of having to fuse the connections. Is there a way to connect lengths of this plastic piping to one another, and also to copper tubing, that would not require an expert?

Finally, can the inground loop simply deposit into a water tank, such as a 30 gallon bucket, into which the in house loop is run, and then pump out the other side, or do I have to keep it all in the tubing?

Many thanks,
Buffalo NY

SPS-1 02-23-2010 05:47 PM


Originally Posted by PaddyKevin (Post 404842)
2. the principle is that when these two meet the basic physics is that the two “banks” try to equalize out, or go to the same temperature.
Am I right there?

Not really.
Geothermal systems do not try to equalize the temperature between the house and the ground. If they did, 50 degree ground temp would never get your house to a comfortable temperature. There is still plenty of heat energy in 50 degree ground ( or air, or anything ). A geothermal system PUMPS that energy into your house. A geothermal system is exactly a heat pump.
You lost me in your description of your plan, but since I didn't see the words "heat pump" in there, I am not sure how well it would work.

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