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There is a material that is currently being used in drink warmers call phase change material. It absorbs heat which causes it to melt and then hangs on to that heat for much longer and releases it slowly. I wonder if this material could be used for what you are talking about.

GT deep energy to Storage in ground, and if looped

Well, a deep subject for storage,
dry earth and earth drying about cisterns has successfully been used.

IF the GeoThermal was from higher temp deep geothermal [below the conventional GTHP uses of the solar energy stored near -grade] as well, I have reason to believe:
YES, it can be stored in the ground.

-ground used for storage, as the Swedish demonstrated with solar exchanges over 110-degrees, for reuse.
Plausibility for that is going to require more than what is posted above. How much wanted stored, how fast/ how fast transferred requirement---

An error with energy transfer storage was found on an ice-melt tank cooling-storage system. OEM and installers were quite puzzled, as well as the very analytical owner:
The tanks were large enough for the heat content (or cooled content ) to handle peak loads, BUT the RATE of transferrance (in a piece of sales literature) through the systems was 2/3rd's what was needed at a peak moment , all systems on. So more vessels were added for the heat energy transfer "speed" required.

This thread went WAY away from the OP it seems (he was not talking about conventional Geothermal systems, and instead about using the ground for storage). In which case, i still feel the best way, no matter the size, is a stratified water tank. Bury it if you want the added insulation, but there is a reason just about every thermodynamic system on earth (natural or synthetic) uses water as it's primary medium. A reinforced concrete tank below grade will outlast any other part of the system, even if left completely unlined. Build it under your drive-way, and you have the added benefit of not needing to shovel snow.. (for you poor saps that have to deal with that hellish stuff) :-)

Originally Posted by GermainPilon

Madhat

Since every ground , is the "condition" , no 2 loops are identical in storage, nor depleting exchange or admission of heat energy, I have reason to believe.

Found that horizontal boring works fine in workable conditions, and seems 10-12% more footage at depths under 10ft boring , is better than vertical (even 15% more boring, like a dry , non-rock, vertical borehole may require).

In situ testing I did in 1997 showed a 30% variation from just locations in Cleveland 5 miles away from each. one test was over in 1/2 day static water was 44ft from grade ; and the other static water at 125 ft , used for a library, had a 19th hole installed, because 12 hours into the testing, it was still gaining at 30% warmer than that first one... More footage on the spot (at my and the drillers expense) to cover the engineering for 'hoping' to not have to use antifreeze at all. It worked. above 38 entering, but jamming over 3gpm per "size-ton" close to 4gpm per compressor-label-ton.

Originally Posted by madhat

Trane was experimenting with something similiar in the mid 1970s. They were heating a slury that was similiar to concrete, that would never set. I believe the stuff also had a lot of salt in it.
Horizontal Ground Source heat pumps loops do that to some extent.

The Swede's in the 70's posted reports with graphical cross section views of cisterns heated for storage.
In 1980 an article had a view of a cross section of the DRY earth - stored heat- shown as a cardioid shape about a cistern that was 2" insulated at the top, and top was 5ft deep . Can't rem the soil conditions, nor ground temp.

Madhat

Originally Posted by GermainPilon

I'm agree with your thoughts.

I'm agree with your thoughts.

that site:
installation view and scheme below

http://www.geopros.org/job-gallery.html

wording is rough, certain points are there

Originally Posted by ChrisJ RI

My horizontal loop was installed with a PVC piped drip loop about 12-18" above HDPE pipes. I can introduce moisture to the soil if need be....


ChrisJ RI

yes, and overall Earth RADIATES AWAY the solar gains that are lower than our additions, net to net:

another 3rd addition to the above, please:

3) ENTER: HOW ARE WE HEATING DOM HW WITH GT , AND IS IT 100% HEAT RECOVERY IN THE COOLING MODE: IS IT SERIES FLOW REFRIGERATION FOR ON-DEMAND HW (which uses as much energy as a 1990's mid size car) and IS IT INSTANT- "ON" AND LIKE AN OVERSIZED DESUPERHEATER IN HEATING...?
and I think you will find the net heat production is going down the sanitary sewers, thus relatively (and in newest "green" homes) equalizing any of the long ground-drying, absorbing , etc discussion.

LOOPS personally hands on 15% glycol, near Cleveland Ohio, in 1983, with Jeff Abbe and Jim Schafer of Grace GeoThermal, on a Friedrich, NEVER CHANGED the 2 x 250ft series x 1.1/4" PE vertical two wells surrounding Earth Coupling after a couple years balancing without On Demand HW ,

AND in a commercial job : 24 tons rejected to only a measly 3200 vertical bore at 103f x 55 gpm off of a 20- ton compressor, recovered to 57 degrees , dead of summer, off line in 3 weeks... [[ don't ask the app and OEM sizing, there 1994-1995 ]]

the more gracious 1997 Superior Branch Lib Cleve I added loop to get to 5400 ft block cooling load 27 tons, of compressors engineered, not actual net btu's and all ...
never goes below 38 degrees in the winter at a high glass building, and uses NO ANTIFREEZE - getting maximum use in their-design with 45f EW Trane GT HVAC instead of the larger HX 30-deg rated GT components. -jamming ovr 3gpm-ton in the summer, though. Every year the same.

see website installation drawings that work well at just 7 and 5 ft deep. The south has specs at under 4ft deep, I see.

that trench is an 8ft deep with an over lay 5ft deep 52 clay soil on 4t CM/ DeSuperheating, never below 34f in 3 years running (36f actual peak low) damp clay: under $ 22k, new HW tank, some ducting R/Air changes, half the Loop cost of subbing-vertical installers of over 6000 systems... 100 year old farmhouse , 780 gal oil down to under 100 gal topping off HW production. 3yr ROI, not adding inflation, etc. comparing only to a "plus-gas Propane and HP 14SEER" it hits "seer's" OVER 30+ all considered in HW boosting generation, in Cooling mode.

a $ 600. uty rebate helped too in addition to all receiving, as were qualified, the 30% TC

Originally Posted by jpsmith1cm

I thought that was going to be the angle... a hoizontal field work by depth or sizing?

Late hello:
but
I believe a few points are correct along the JPS response Q'd---

and removed a 21 pound r-22 leaked, Dx erroding away, for 1/2 ton smaller (by compressors) on demand 100% instant HW, heat-reclaims in cooling mode (loop pumps off line then - that 20-min 80 gal recovery of HW periods)

removed 3 systems at a parade of homes, lasting under 10 years...(dx must have soil considerations)
(vert bore grouted DX ? Hows that doing to under 20k trenches including instant-100% HW Priority in Heat-Reclaim cooling mode, to really know, please?)

Originally Posted by jpsmith1cm

Gross,

Got any info ...

JPS

I understand the thread is older, but the inaccurate info I have read about DX to say horizontal is alarming.
You now probably know you were in the right vein of heat transfer--- but vs cost to the situation.

A school of 32 x 7ft x 250 ft trenches GT horizontal is up and fine for a 4th -going to 5th year now...
and at 1/3 less than the vertical complemnt.
that ~ 120 ton ground loop is netting over 90 , just fine with 3 x 1" sdr9 (not the exorbitant sdr-11, seen comm spec in Ohio) is PE 3408 AND IS A CONDUCTOR, ALBEIT A SLOWER CONDUCTOR THAN COPPER.

The vertical loops in our area at 35f and 31f back to the loop hit loop absorption between 41 to only 44 btuh/vertical, STANDARD grouted , least expensive per ton installed foot. So like my 1980-1981 quick solar collectors of window screens and air boxes, 6000+ btuh per then $ 2000 installed (!) heating air, 3500 for water 3-way air to HX coil box looping-
these vertical loops ARE effectually capable of virtually EQUAL to DX without the worry of lime and mineral ionic degradation of say a Cu copper pipe

Typically a 4.0 size-rated, 38k compressor in the box, absorbing 27000 btus every hour needs about 4 x 15 ft vertical boreholes to run 24/7 for 3 or 4 weeks regardless of being overloaded- say, for now.

and an extra 200 ft as Mike S uses in colder ground I guess than 52f, damp, standard grouting, etc etc...
is what BARD and many specified, as DID Hydro-Temp in the southern to Northern, all markets...

I found I could performance guarantee contracting with (for mktg reasons) 186 per rated -size "ton" comes out in the above 38k (3.17 label-Ton of the compressor) to ~ 234 ft per COMPRESSOR TON like used as the actual TONS in a Wtr:Wtr, for 24/7 operation / 3 to 4 weeks/ radiant, bbd, ice melt, apps, etc..
FOR A PREMIUM SAVINGS like DX experience, without the misapps of the Cu in various soils the PEthelyne piping knows not.

2) THE WELLS IN CINCINNATI-DAYTON OF 56 AND 54.1f , respectively, and Col 53f have not changed 1/10th of 1 degree F, every time I look at them , GT one site installed, 1980, Dayton Ohio.

The Largest WF Dealer in that area reports the same, also installing since 1980, as 'well'.

Originally Posted by swei

I've seen the heat load dumped into PEX loops that circle the house just outside the basement walls. Clobbers basement humidity during the summer.

Yup, I've done it under driveways or around the outside of the house as well. It can work well. Uses a lot of glycol though.

belated reply

Originally Posted by ga-hvac-tech

THX! This makes good sense to me. The area I live in (Atlanta GA area) is basically an AC market

I know GSHPs are popular in GA, but I just looked you up to see what the numbers are. According to http://www.homeinsight.com/home-value/ga/atlanta.asp you have 1832 heating degree-days and 2319 cooling degree-days, which fits.

the ground could be 'heat soaked'... because the geo system was removing heat more than adding heat (thus a build-up of heat in the loop. What remedies do you suggest for this condition? Larger loop, using wells (better chance of wet soil)? Wish there was a stream or lake available... but not so.

If you did have this issue, the stream would the best solution, and it doesn't have to be above ground. As long as there is some water movement across the loop field (or you run an open loop system which has water moving across the withdrawl/reinjection well sites) your heat plume becomes someone else's flywheel problem. Highly unlikely to be a real issue unless all the neighbors are using GeoExchange too.

Larger loops, deeper wells, deeper dug horizontal field, etc. are ways of increasing the surface area of the heat exchanger. Any competent PE firm that does GSHP work will have software that can model all of this stuff.

My horizontal loop was installed with a PVC piped drip loop about 12-18" above HDPE pipes. I can introduce moisture to the soil if need be.

I don't know what temp the ground water is in GA is but could bring down the loop temp in summer.

ChrisJ RI

Originally Posted by swei

Geo exchange still works best when the seasonal heating load and seasonal cooling load are roughly comparable. If the imbalance between them is significant and there's no significant water flow across the loop field, accumulation happens.

THX! This makes good sense to me. The area I live in (Atlanta GA area) is basically an AC market... so following this reasoning; the ground could be 'heat soaked'... because the geo system was removing heat more than adding heat (thus a build-up of heat in the loop.

What remedies do you suggest for this condition? Larger loop, using wells (better chance of wet soil)? Wish there was a stream or lake available... but not so.

Originally Posted by SolarMike

To me the reason to dump the solar heat into the ground is to keep the glycol from boiling too much. Otherwise it will need to be replaced every couple of years. We have installed a number of systems and the clients always want more solar heat than can be absorbed during the summer.

I've seen the heat load dumped into PEX loops that circle the house just outside the basement walls. Clobbers basement humidity during the summer.

Originally Posted by ga-hvac-tech

I was talking to someone a week or so ago... they said something about the ground getting heat-soaked or cold soaked. What that means is; after years, the efficiency just goes down. I can understand this, makes good sense.

Geo exchange still works best when the seasonal heating load and seasonal cooling load are roughly comparable. If the imbalance between them is significant and there's no significant water flow across the loop field, accumulation happens.

To me the reason to dump the solar heat into the ground is to keep the glycol from boiling too much. Otherwise it will need to be replaced every couple of years. We have installed a number of systems and the clients always want more solar heat than can be absorbed during the summer. You an always use a drainback solar system if you don't want to dump the heat.

Most of the GSHP installs we have done over the years have been wells, 200-250'/ton and MINIMUM of 12' apart. It all depends on the soil conditions but better to be safe than sorry. We have done a few lake systems where the piping was laid out like a slinky and weighed down with a steel grid and cement blocks. It was always HDPE or PEX. The only problems we ever had was with horizontal piping which seldom measured up.

It can be done, but it is also can be intensive to monitor all of the specifics of performance. We have done this with solar thermal panels on one of our geo houses. This scenario is only enabled when they are in the heating season and when the DHW tank is satisfied. We have 120 gallons of domestic storage and have a bottom of tank high limit of 150 degrees. After high limit has been reached, and the solar panels are warm enough, the solar pump is activated along with the diverter valve and geo-ground loop pump.

What we have seen through logging the temperatures of the ground-loop supply and return lines, is that this is having quite an effect on the return temperature of the fluid from the loop field thereby boosting the COP quite high. The energy used to deposit the BTUs to the ground loop is much less than the actual energy deposited.

The panels will run for a long time when they are heating 55 degree water. It has worked quite well, but of course if you have a high water table, it will not work. I have not spent too much time tracking everything on the logs since there is so much information to look at. The controls are quite intensive with radiant heating, radiant cooling, solar, geo, IAQ, etc. No time to look at the logs at this point.

We have also worked with an engineering team for a large geo project that was going to use heat accumulators with solar. They never received the grant, but it has been done quite successfully in the past. It is really a matter of cost/benefit ratio with many, many engineering problems to solve. Hope this helps out some.

Originally Posted by thehvaclady

Are there many Geo thermal systems being installed in the south? I did a little research and found that there are only a couple of aquifers in Georgia. I attended a RSES meeting that gave a presentation of Geo Thermal systems. Are there any technicians near Georgia (or nearby states) who has installed one or do any type of maintenance on one?

Last time I went to the home show at the Cobb Galleria center... Water Furnace had a booth with folks from a few geo contractors in the area. They are here... just not advertized much. Look up my Email in my profile and send me an Email... and I will send you the names of two I have info for.

Geo Thermal in the South

Are there many Geo thermal systems being installed in the south? I did a little research and found that there are only a couple of aquifers in Georgia. I attended a RSES meeting that gave a presentation of Geo Thermal systems. Are there any technicians near Georgia (or nearby states) who has installed one or do any type of maintenance on one?