Improving air conditioner efficiency could reduce worldwide temps

Yeah, i lived near a place where wells were incredibly common, so there were plenty of well drillers. I can believe 30k installed. With the 30% federal tax credit that used to exist, and Maryland's 30% state tax credit, it can be worth it. Now, without the 30% federal tax credit, it's probably only worth it on new home construction.

"I have three friends/co-workers that had the systems installed. None were particularly impressed with the average cost savings. They said bills went down, but not dramatically. One person had the whole system redone at the suggestion of another HVAC contractor (saying the first cut many corners) the re-done system wasn't much better. "

This depends a lot on where you live, the climate, etc. Also how much you are spending on heating/cooling. You know all this. I was in a fairly large house in a climate that seems 90+ summers and ~25-30 winters. This kinda sucks for heat pumps. It's also the case that, as it's become more popular (relatively), there are some crappy untrained contractors looking to make a buck. I definitely did a bunch of research, and talked to a bunch of contractors before doing the system. I think out of 5-6 contractors, 1 was clearly a snake, and 1 didn't really know what they were doing based on the questions i asked. 3 could tell me intricate technical details about the systems (IE one launched into a discussion of the merits of parallel vs series vertical piping and reynolds numbers), etc.

FWIW: I've also meant plenty of happy vertical closed loop people. I haven't met any happy horizontal open or closed loop people.

That said, unlike the air based units[1], all, for example, of the waterfurnace units have detailed submittal that tell you, for a given entering water temperature, what the EER/COP will be, what the pressure drop should be, the leaving air temperature, etc.

http://www.waterfurnace.com/literature/7series/SD2700AN.pdf

Most of these things are easily amenable to sensors. I had an arduino and a bunch of sensors that told me whether the system was performing okay.

After they first flushed the lines, they weren't sure they got everything out of it and told me to try it. So I did, and the measurements told me something was off. System worked, when cooling, water temps were raising too quickly. They ended up digging the manifold back up, and there was a rock in it (terrain is fun!) After redoing the manifold, everything was perfect.

So i can also believe that if you aren't watching the till, you may not know if the system is doing okay. But at least, unlike most random heat pumps, i feel like I could know and track that stuff pretty well. Overall, my system actually overperformed (which means they probably didn't need to go as deep as they did, but such is life).

[1] This data exists, it's just not usually easy to get for air source heat pumps unless you are an installer/technician.

So they do something like:

outlet | | manifold inlet in the ground | a bunch of pipes formed into U's, stuck in very deep vertical holes filled with thermal grout | | manifold outlet in the ground | | inlet

The manifolds look like this: https://www.geohydrosupply.com/index.php/fittings/socket-fus...

If it's done in series, each u-bend connects to a set of two outlets on that manifold. If it's done in parallel, each u-bend connects to a single outlet on each of two manifolds, one in, one out.

Here's a drawing: https://blog.heatspring.com/wp-content/uploads/2012/01/paral...

If you can imagine a really huge refrigerant loop, that's what they are, with water+glycol as the refrigerant going through the pipes. But the water only moves in this loop, it's never going into the ground, etc.

Open loop systems exist, and those are the ones where they are sucking something in one pipe, and pushing it out the other.

Sometimes this is done in a pond, sometimes a well, etc. What happens depends a lot of the design (horizontal, vertical, etc).

Open loops are pretty uncommon.