arkieoscar,
Read my post below the one with the (2) 1500 gal tanks. I took a trip out to see the guys setup and found out he has not (2) 1500 gal tanks but (3) 4500 gal tanks for a total of 13,500 gal of water (a LOT bigger than I remembered from a previous visit awhile ago).

For all the sceptics out there I personally think this system has to work as good if not better than several hundred feet of buried pipe (but with an added expense I'm sure). I'll try to update everyone on how the system is functioning later this year provided he gets his solar panels installed.

There is a lot to figure, ie; a 4 ton closed loop heat pump requires 12 GPM or at peak load loosley 17,000 gallons/day of flow. Depending on how the tanks are laid out, you may go through your augmented water twice in 24 hours.
Solar heated water could allow us to get by on 1 1/2 to 2 GPM, but without ground loop assisst, I could see your tanks running shy after a couple of cloudy MI winter days.
Does the owner of the system vary the GPM flow?
Sounds like the system will elevate COP and drive down operating cost, but its more of a tinkerer's (or engineer's) dream than a practical system. Installation cost sounds quite high and level of homeowner participation is as well.
Sounds perfect for jonr, he's been wanting to fill his basement with tubs of water for years.
Keep us posted.
j

13500 gallons * (160F - 40F) = 13.3 million BTU. A 3-ton heat pump extracting 25,000 BTU/hr will cool the tanks from 160F to 40F in 22 days of continuous max-load operation. No point in going below 40F; I can get that from a ground loop.

As a practical matter, geo HPs have an upper limit of allowed EWT, even in heating mode, around 100F or a bit higher.

Posted By engineer on 12 Mar 2010 10:15 AM
As a practical matter, geo HPs have an upper limit of allowed EWT,
even in heating mode, around 100F or a bit higher.

Yep, but it should not be difficult (in principle) to temper the water from the storage
tanks. The price would be added complexity and a reduction of COP (compared to
what might theoretically be possible with EWT > 100F).

OTOH, for a smaller capital investment, it should be possible to build a ridiculously
oversized ground loop and achieve very high heating COP (plus A/C) with a vastly
less complicated system.

..."clever" is often the opposite of "smart,"

Looby

I would think once your above 100F you might as well just circulate the liquid in the storage tanks rather then use the heat pump. Then once you fall below 100F switch back to the Heap pump. Even more tinkering, but it sounds like it would not be much more than what is already there.

Brock,
I agree. I think this guys setup will do just that, meaning if the water temp is above 100 f or so then he will just circulate (via pump) thru the radiant floors for heat (bypassing the GSHP).

The whole thing strikes me as a bit of a Frankensystem - an interesting one-off but not one I'd want to be responsible for care, feeding and support.

If the loop was developing frost in the ground and there was little A/C load , like here in Canada , its a real good idea that would recharge the field during the summer. I wanted to do it on a commercial job I did but without some goverment funding no one wants to fund  such concepts.

In our area there is a company that is using a solar panel to dump heat into the ground after the exchanger in the GSHP.
this way it only heats up the ground loop and does not have a huge impact on the EWT. In the summer of course it could have a serious effect on the EWT. using a solar water heater control it monitors the ewt and only allows it to dump heat below a set limit. Doing this will increase the COP around 1 point which is a huge impact on the efficiency of the unit.
I have not tried it yet, waiting for a customer who is willing to take the challenge. Some issues which I am not aware of are the antifreeze issues. most of what we use in geothermal is not rated for the lower temps needed for solar panels, shell and tube exchanger to isolate the two may be needed.

Posted By Looby on 12 Mar 2010 09:25 AM
13500 gallons * (160F - 40F) = 13.3 million BTU. A 3-ton heat pump extracting 25,000 BTU/hr will cool the tanks from 160F to 40F in 22 days of continuous max-load operation. No point in going below 40F; I can get that from a ground loop.

Not sure how you get the water to 160*. You would kill summer EERs if you were trying to bank that kind of heat in a closed loop situ. If it is an open loop situation, then you wouldn't have 13500 gals available as you would have to have a discharge tank.
We don't know enough to be sure, but without supplemental loop wouldn't you remove btus from your tanks faster than a large solar set-up might provide them? If not, then why do you need the heat pump at all, you could go all solar.
I think it is more likely that this set-up is designed to elevate water a few degrees simply to impact COP, I think it unlikely that it could run more than a short time without augmentation.
j

Posted By joe.ami on 16 Mar 2010 09:58 AM
Not sure how you get the water to 160*.

I didn't get the water to 160F, one of rjdagala's neighbors did (or theorized
that he might). See posts #9 and #11 in this thread.

Apparently, he's not worried about summer -- 'cause the tanks are insulated.

Appears to be closed loop. Starting with 160F water, you'd just recirculate
until the tank temp was no warmer than what a ground loop would provide.

I wasn't arguing for or against the proposed setup -- I just calculated the
BTU storage capacity under the conditions described. Lots o' BTUs, and
lots o' complexity. Personally, I prefer simple...

...because Murphy was an optimist,

Looby

Looby, I get what your saying, I'm just trying to figure out the layout here.
I agree sounds optimistic, complicated and is likely off the ROI charts.
J