Low utility bills with geothermal heat

[eepete]

The way my geothermal guy explained it to me, you have a "normal" well with a well pump at the bottom. It pumps up through the geothermal unit, and then the water is dumped back down the well. The head of the well has to be "clean" and sealed up pretty good. The pump is often a 5-10 GPM depending on the size (tonage) of the geothermal unit you have. This is the most expensive type of geothermal, but the win is it can be used on small lots (i.e. suburbia). The potential close-ness to others is why things have to be clean. You also could have all the concerns mentioned above with open loop systems regarding Ph and hardness. I don't know if there is also a heat exchanger coil you can drop into a well. The loops that were in my pond were fairly substantial (8 250' coils), so I'm _guessing_ it would be difficult.

Pete

 

[luscsmith]

That sounds like an open loop system with the discharge draining back to a secondary well. 2000 ft of tubing, is that about standard even if it is buried?

Scott

 

[SpringHollow]

Closed loop vertical systems just use heat transfer through the pipe. Instead of lots of horizontal pipe, you have lots of vertical pipe.

ken

 

[eepete]

My geothermal guy mentioned that style ksimolo. He said the wells in this are were often so shallow (150 to 200') that that may not aways work. I suspect there is also the issue of how big a unit you're trying to run. As with many other things, which part of the world you're in changes the approach.

luscsmith: the water was discharged into the same well. The information I'm missing is how much water was in the pipe in the ground. For example, was the well dug to 200 feet and and 100' of water standing in it, etc. I do know that some people around here were unlucky and have a 500' well with about 150' of water at 2 GPM or so. They count on the storage in the pipe to get them thru. I would imagine that would work for a 3 ton unit when you look at the surface area of the pipe for the well vs. the surface area of a 5/8" pipe in a pond. Sorry I don't have more specific date, just passing on what I've heard.

Now for an area where I have direct experience: As for how much tubing is put in the ground, I have a 3 ton unit with 1000' and a 3 ton and 5 ton (total of 8 ton) on 4800'. When I had the 8 tons of load on a pond, it had 2000'. I suspect that's the difference between the pond and the ground is the difference in the thermal conductivity of water vs. the ground.

I abandoned the pond and went in the ground because the water coming out of the ground for heating was warmer that the water coming out of the pond. The pond was giving me 40 degree water, the ground was giving me 58 degree water.

 

[buckeyefarmer]

Ponds are normally better than ground loops for a closed loop system, but the pond has to be big enough and deep enough. 8 tons with 2000' of pipe sounds like a seriously undersized loop.

you can put closed loop vertical in very small spaces, such as 1/2 acre lots. Vertical "wells" are normally in the 200' - 300' depth and are grouted shut with thermal conductive grout.

I got my geothermal HP's delivered this week, unloaded them with my tractor forks but didn't take any pics. Now I need to get my loops buried before winter.

 

[SpringHollow]

With the vertical ones, they put in more than one vertical well in order to get the number of feet of pipe they need. It is usually only done when there is limited suitable land.

Ken

 

[irvingj]

As I recall, in my vertical loop --right down my only well with the well pump-- I have two 3/4" loops (manifolded to 1" lines coming in to the heat pump), down 275-300 feet, with a static level of 80' when we checked it.

It sounds low, but it looks like I've got about 800-1,000' of submerged loop.

COP when installed was around 3.25; 8.5gpm with a 4-5 degree drop, again, if I remember correctly. Seems to work!

 

[whistlepig]

I appreciate some peoples stances on the open loops, and there are a lot of locations where they couldn't be used, I E densely populated areas.

I am in a different situation, here in Missouri. I am located on a 4 acre tract and there are large 30 acre + parcels around me. Also our aquifers are abundant and not dropping in water level. I have a gauge on my well and I monitor its water level. no droop at all in the three years of use.

Unfortunately a lot of people have been fed the environmental Al Gore spin on everything, and don't really understand that a lot of the stuff is totally unfounded and not scientifically proven. Global warming is a perfect example. Totally unproven and not scientifically justifiable, but a few people have pumped it heavy, and all of a sudden every body is on the bandwagon. Enough of that rant!

In regards to my open loop heat pump, out aquifers are being replenished adequately by surface moisture, and we are not experiencing a drop in our levels. That is not the case in all locations, and open loop is not suited for all locations.

Nine months out of the year, I use my water that travels through my Heat pump, to water my lawn, and I have a wonderful lawn because of it.

Also I have not had a problem with mineral build up in the coils. I specifically questioned the installer if they had ever problems. He has had them in for 15 years and said that they install about half open loops, and they have never done a chemical treatment on one of them and they have not had any issues.

It makes sense, as people only have problems with hardness (calcium carbonate) depositing on things when its temperature is raised significantly (like in a water heater).
Calcium Corbonate hardness is much less soluble in hot water.

In the coils the water does not see high temperatures so there is not issues. My discharging water is only heated or cooled about 20 degrees so it never gets above 80 degrees. No issue with minerals.

Even if it would become an issue it would only take running dilute hydrochloric acid through the unit to remove the minerals. Not a big deal. They make a kit that can be installed to run the HCL through the unit, but because of my installers positive experience, I decided I would put it in later if it becomes a problem in 15-20 years.

Don't always believe what you hear, as sometimes fables get proported that are not always true.

My unit works great, and I feel comfortable that I am not desecrating the environment .

This is good information on an open loop system. I don't always believe what I hear. That's why I check in to this forum and listen to peoples advice. I would much rather hear from someone that has actual experience with something that someone that has read the brochure.

 

[AHNC]

Back in the late 70's-early 80's I was a mechanical contractor and we used to handle "water source hp" systems differently. I used to use a glazed solar system to heat the swimming pool water and use that as a heat sink for the hp. The pool could be outdoors with a good insulated cover or indoors. Given the low temps, collector efficiency was very high. In the AC operation you rejected heat to the pool and it would usually cool off at night. Be careful there!

Downhole heat exchanges (DHX) are very good in systems that have an aquifer that has a flow gradient. For instance, Klamath Falls OR, pretty much heats the whole town and homes with direct, hot geothermal water and it is done with the dhx (a hairpin of pipe). You're out of luck for cooling however. We tried the dhx in Calistoga, CA and found that they did not perform well as the geothermal resource was essentially a pool of static water so you tended to cold cap an area. Google the Geo-Heat Center at Oregon Inst Tech for a lot of info. Also, Cornell Univ is using a large system powered off the water resource of Cayuga Lake.

As to the open/closed loop system discussion, I would only use a closed loop. The systems I built 30 years ago are still running because of the closed loop systems. I think the heat pumps have been replaced but the systems are in place.

 

[SuperCobra]

...The best part is the utility bills. The largest heating portion of the electric bill we have ever had was $45/month, with the largest summer cooling bill of $30/month.

Ground source heat pumps rock

Curious - How do you isolate the heating portion of the electric bill from the rest? Separate wiring and meters?