Can geothermal heat be stored in the earth?

[jpsmith1cm]

again, youre ignorant to what youre talking about. I, as well as other members of this site, install them currently. I put in two last week. There isn't thousands of feet of pipe or thousands of pounds of refrigerant. Its more like 10-25 lbs, depending on the system. Youre passing judgement on something you obviously know nothing about. As far as breaking a pipe, who pays for the well pipe to be replaced when a hdpe pipe breaks?

Gross,

Got any info you would be willing to PM me on these systems?

My dad was talking about these a few years back, before he got sick and passed.

[kaleun]

I thought that was going to be the angle you took.

So, vertical wells are the 'only' way to go, then? No way to make a hoizontal field work by depth or sizing?

you can make it work. but you have to live with the fact that the water temperatures are further away from where you want them with the energy/wear penalty. If you dig deeper or make the field larger you can get close in performance to vertical field. but then you spend more money and saving money is the whole point of a horizontal field.

Most applications also would run out of space with horizontal fields. Space already is an issue with vertical fields in cities, unless you have a farm for your commercial building, I don't see horizontal fields working well. I'm not even talking about retrofit.

Again, I'm not saying it is not possible, I'm just making the case that there is a reason why almost everyone uses a vertical field. To each his own, I'm not telling you what you should do. Maybe I should start by saying: "this is what I would do... ". Is there a chance that in 1 out of 100 applications a horizontal field is more economical on the long run, sure... . but most people installing horizontal fields do it because of upfront savings, not operating savings.

This all requires some good soil analysis and someone designing who has experience with that. It is not rocket science, but requires consideration. I'm not an expert in this and don't claim to be one. I have a bit experience with it.

[kaleun]

again, youre ignorant to what youre talking about. I, as well as other members of this site, install them currently. I put in two last week. There isn't thousands of feet of pipe or thousands of pounds of refrigerant. Its more like 10-25 lbs, depending on the system. Youre passing judgement on something you obviously know nothing about. As far as breaking a pipe, who pays for the well pipe to be replaced when a hdpe pipe breaks?

I'm not claiming to be an expert and you have experience in that, it seems and where you live they seem legal. I just wonder how you have so much less pipe length than with a water-based system? the main bottle-neck is soil conductivity and you need long pipe-runs to have enough surface.
Regarding leaks, HDPE is more flexible and less likely to break. What pipe material do you use, copper? It also will require quite some refrigeration knowledge since you basically create an evaporator/condenser. Most contractors wouldn't be able to do that since most systems basically get designed by the refrigeration system manufacturer (incl. pipes between condenser/evaporator).

Regarding leaks, besides HDPE less likely to break, the refrigerant is under higher pressure and would leak out sooner. With a water or even glycol system I could live with a tiny leak for a long time by re-filling.

I'm not trying to argue, I'm curious about this since I had researched on that a while ago and had concluded in my area it isn't worth pursuing. It is a similar issue with in building WSHP or VRF systems where with a VRF system I get more efficiency, but the potential of refrigerant in the building. Obviously I can route pipes so that I can fix them, which is hard in the ground.

when you use refrigerant geo systems, do you can simultaneously heat and cool? unless you run separate loops, I don't see how that works.

Again, not trying to argue and I admit you likely have more knowledge than I do. But I think I raise some good points to consider and would be happy to learn more about. .

[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?

[ga-hvac-tech]

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.

[Bethlehem]

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.

[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. 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.

[swei]

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.

[swei]

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.

[ga-hvac-tech]

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.

[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.

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

ChrisJ RI

[swei]

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.

[SolarMike]

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.