As part of a house design I'm working on in coastal Rhode Island I will need an underground electric service of about 300', A trench to a well of about 100', a trench for a gravity fed irrigation system of about 400' and a trench for septic of about 200' and a trench for a power feed to a wind tubine of about 100'. So all totaled, about 1,100 feet of buried stuff. My question is this - is there any point in my dropping a loop (or 2?) of Pex into these trenches in the hope of caputuring either some ground heat or cooling? The house will ot be air conditioned as the local climate is very temperate and electric rates are too huge to run a heat pump ($.64/kWh). One thought was the hope to dehumidify a bit by running air over first a coil with water direct from the ground loop and then over a "reheat coil" with water from a solar thermal collector. This is a damp island climate (think nice clear days and foggy nights. The normal routine is to open the windows for the breeze about mid morning after the fog "burns off" then close all the windows at sundown to keep the fog out. This still results in some mustiness in most houses in the area and hydroscopic stuff like paper and fabrics can get moldy. I realize that if i dehumidify at night then open the windows the next day all my "gains" are gone literally out the window (I know - you can't condition what you can't contain....) but I thought this might help to remove some of the moisture load from the house. Perhaps this might help to reduce moisture in a mostly enclosed basement (which will be ICF). Any thoughts?

There are two problems. The trenches will likely be "shallow" compared to regular horizontal loop depths, so the ground temps will fluctuate much more, much closer to surface temps. Secondly, even though the coolant that is circulated around will be cooler then the air it likely won't be enough to dehumidify, it has to be quite a bit cooler, high 30's to mid 40's?.

Having said that I don't dump heat to our field in summer, instead I dump the heat in to our pool / hot tub or the kids outside pool. Then I cool at night or off peak and during the day I run the fan on 1 or 2 (of 4) and just circulate the water from the field through a coil in the furnace. At the warmest part of summer I was pushing 63F coolant out to the field temps and returning about 60F, while it didn't "cool" the house it kept the temps from rapidly rising during the day.

I say go for it, at the most you will be out your time and the cost of the tubing. You will get some cooling; the question is how much...

64 cents per kWh? Move back to the mainland!

I think Brock is right - Ground temperature plus a few degrees for heat exchange isn't going to be cool enough for effective dehu.

The well / irrigation water, fresh out of the ground, is 10 degrees or so cooler than the ground loops' in summer in Michigan. I had thought of passing the cool well water in a passive air cooler / dehumidifier, before using it in the house or in the yard. It's just a thought.
Regards, Masoud

Commercial chilled water systems provide AC and dehu with a water supply at 42 deg. If the water is much warmer than that some cooling may be available but dehu will be limited