Direct exchange (DX) geothermal

[fredhargis]

Anyone have this technology (or an opinion of it)? I'm having an estimate done today and it competes with the more common systems for my shekels. For those not familiar, as I understand it the DX systems recirculate the refrigerant through the ground loop...as opposed to a water based solution to transfer heat. The installer claims much higher transfer efficiency (which I believe, it's a copper loop instead of plastic) and lower operating costs (not sure about that) versus the common systems. I had a ground source heat pump installed at the last place and truly loved it. We moved here a few months back and this place also has geo, but it's a 1998 system using a pond loop. It's really doesn't work that well and we'll be replacing it. Thanks for any comments/input.

[cams2705]

Don't have it, but my initial thought was the cost difference between plastic pipe and copper (x 300'+ deep X 2 for the loop) as well as the cost of water/antifreeze mix vs. refrigerant for that length of pipe.

[fredhargis]

True, but the copper loop is shorter. This outfit digs a pit, then inserts some number (depending on unit size) of copper pipes down 70' feet into the ground. As i understand it, you can also have a trench loop but the local guy does a vertical loop. No doubt it will cost more, but I need to move while Uncle Sam picks up 30% of the tab.

[Robert Adams]

I looked into those a while back. Performance etc looks good however well drilling is $25+ a foot here so cost prohibitive. It should be much better than using a cooling loop. I worry about the life of the copper coil though.

The problem is finding real world data and someone who knows how to do it as geothermal is still very small and the few places I talked to I found I knew more then they did after I did my research.

The only place I have found decent info is on http://ecorenovator.org where many there have built their own geothermal systems from scratch and built their own heat pumps etc.

I looked into doing a trench coil system but because of the high ground temps and soil type it would take a very dep and large trench to do it and we have too many trees to do it.
Maybe our next place it'll be do able or hopefully have a stream or pond to use. I mainly care about cooling heating is cheap as it is.
I have been planning to run the well output through a coil with a fan to cool the shop while it's running. Might as well use that cold water for something before dumping it on the yard.

[JDuke]

Robert Adams said:

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I have been planning to run the well output through a coil with a fan to cool the shop while it's running. Might as well use that cold water for something before dumping it on the yard.

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I have thought about doing something like this with output from a well through a radiator in the shop and dump the output either into a holding tank to irrigate, or into a pond or yard water feature.

I am thinking that you wouldn't get much cooling with direct exchange like that due to the relatively minimal temperature difference given the short time the pump would likely be on.

You should be able to increase significantly the efficiency of either a mini split or a window unit, by running your coil around the compressor and heat exchanger on either of those, and using it to pull the heat from that, much the way that a geothermal heat pump does now.

It shouldn't be to difficult using a couple relays to turn the water on only when the window unit compressor is cycling.

Duke

[Robert Adams]

True and I wouldn't expect much but say with the shop in the summer and the ac not running it will be well over 100*. So say 70* water would help take some heat out of the building. Especially considering how many hours the pump runs to water the grass.