I am looking for some information on the geothermal heating and cooling. What are some of the down falls of this type of system as compared to the standard hvac? Are there any restrictions as far as the use of geothermal?
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story

Understand lumens, ceiling brightness, beam spread, tilt, and color options to make a wise choice on a common fixture that can range from $75 to $750 or more.
Featured Video
SawStop's Portable Tablesaw is Bigger and Better Than BeforeHighlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
I have heard that geothermal heating and cooling is great! This comes form a close friend of mine. He recently built a 3200 sq foot house and is paying a little more to heat it than I am to heat my 1940 1100 sq foot house.
I to am interested in installing it in my next house (hopefully breaking ground next August) so far I have just been surfing the net to gather more inforamtion. Just go through a search engine.
I would get a bid from an excavation contractor. From my experiance, you may save money on your heating and cooling bill but it will take you about 500 years to break even because of the amount of excavation that has to be done.
the amount of excavation that has to be done
Not necessarily so, DB Most times when installing a closed-loop geothermal system, the out and return lines are laid in the corners of the same trench, about 1.5 to 2 ft of backfill placed in the trench, and then the other half of the loop is laid on top of that, and backfill completed. End result is that the pipe goes out the length of the trench, loops back to the beginning, and then does it all over again, so that, for example, 600 feet of pipe can be laid in a 150 ft trench.
If there's not enough room for a horizontal loop, then a vertical loop can be used. The usual technique here is to drill a 4 or 6 inch well (or two, if necessary), install a loop of pipe in each, and fill the remaining space with something like Bentonite to prevent insulating the collector pipe. No well casing is necessary when done this way, and the "well" or hole can be as close to your foundation as the drill rig can operate.
My heat pump operates on an open loop - - I have two drilled wells on the same seam of water, each can produce about 60 lpm, so I pump from one (which also supplies my domestic water) and return the cooled water to the other well. A pond or stream could be used the same way.
Probably a good idea to talk to the heat pump installer to find out which method he/she uses and just how much excavation needs to be done
Doc - The Old Cynic
You have a water source geothermal? From my experience and studies, that is the most efficient system. Next comes solid rock in a vertical install, followed by layered rock and dense clay, agian in a vertical loop. Back filling in a vertical loop should be done with the same material that was drilled out.
Horizontal loops are also efficient, but care must be taken durring the install. depth and seperation of loops are important factors. A good Geothermal HVAC designer can give you the best system for the area.
Dave
One thing I would like to mention. I had a vertical loop system installed and it required 7 loops to get the capacity. Also, after it was all finished and the grass grown back, we developed 2 sink holes in the lawn, they appeared over night and were about 15 feet deep and about 10 feet wide. We managed to fill them in only to have them reappear. To this day we fill them in about twice a year. We live in an area where soil is very easy to come by so we can live with this problem, but i can only imagine if a sink hole developed right next to - or under the foundation of the house. If we don’t fill in the hole it simply gets bigger and bigger. This has been going on for about ten years and still the problem persists.
Edited 8/20/2003 5:00:13 PM ET by gecko
Interesting. Might be convenient if one wished to live in a valley. (G)
What kind of rock is underneath you - limestone or gypsum, or something more solid? And how deep are those holes? The loop-holes, I mean.
Everything I could read or find out would reinforce what DR and Pino wrote about efficiency and the expected rise in fuel prices. and those were some of the things we considered before choosing the geothermal HP. A few people suggested we would be better off with electrical heat, its more efficient, cleaner, etc, but almost all of our power comes from burning coal or oil. I am told that our newest thermal generating plant is one of the most efficient in North-East America, but still only runs about 64% on a good day- while most oil-fired furnaces are approaching 90, and I'm told that the condensing furnaces on NG can do even better - and then add in 5 - 10% transmission losses getting it home. Seems a heck of a price to pay to get all that green house gas and other emissions away from my house.
Whole-house AC is very nice to have on these hot, sticky nights, plus the heat recovered goes into the hot water tank, not back in the ground. And in cooling mode, it functions as a whacking great dehumidifier. Brand new house, and we haven't wintered in it yet, so that will tell the final tale.
Doc - The Old Cynic
I have experience with about six geothermal installs, five vertical and one horizontal. Stories I have heard from the installers would lead me to believe that your sink holes are from bottom wash out of the well holes. They either went through an underground spring or into a small cave. If you live in an area that has sink holes or caves, then that is the most likely cause of the sink holes. One driller told of lossing 60' of drilling bit/shaft into an under ground cave that knowone knew about.
You might want to check with the US Geological Survey Dept. US Army Core of Engineers, or a local college department of geology about your local geology.
Dave
I have come to believe that we did hit an underground stream or something of the like. I don’t think it is a cave as it would have to be a pretty huge one to consume the amount of soil we put into the sink holes. We have asked a handful of installers, and engineers and they all seem to think that this is the most likely case.
I don’t remember the depth of these holes (the loops).
Aside from the sink holes developing, I can say that geothermal heat is a great way to heat the house. It’s nice not to get a gas bill each month.
One of the nice things about hitting an underground stream is that it can increase the output of your unit. As you use a GSHP in winter, for example, the ground will get colder and colder throughout the season as you transfer heat from it. The running water can mitigate that change and kinda replenish the "heat" in the earth. We've checked mine, and the installer expected the incoming water temp to drop from beginning of heating season till the end, but it stayed constant, and that suggested to him an underground stream.
Lots of info from the U.S. gov't:
http://www.eere.energy.gov/power/consumer/hc_space_hc.html
Regards,
Tim Ruttan
Do you recall the efficiency rating for geothermals? I am working off memory, but straight resistance heat is 100% efficient, right?
One of the post mentioned an 18 year payback for the installed cost of a geothermal system. My experience with them over the last 12 years is that a properly installed system will save, in energy cost, the difference in price of a air to air heat pump and geothermal in just under 10 years.
You have had a little more recent experience with them, so feel free to correct my thinking here.
Another real world savings comes from improved building practices. ASHRAE load calculations are based on "standard" building practices and code minimum construction. Tight construction and enhanced insulation packages can mean anywhere from a 2k to 5k btuh reduction in load. Depending on climate and house size, that could be as much as a 5 to 10% savings.
Dave
I got in trouble with Tim the other month for using the word efficiency, so I'll avoid it. What I had heard is that for elec resistance, one unit of energy in results in one unit of heat out. For gas and for heat pumps, 1 in results in 2-3 out. For geo, 1 in results in 3-4 out. Or something like that. I'd have to look up the numbers for real. Another way to measure is that 19 amps of 220 gets me 12000 btu/h for the supplemental elec heater on my system, while 13.9 amps of 220 gets me somewhere between 48000 and 60000 btu/h. That's why I pulled the cutoff on the supplemental heater.
And when you talk about improved building practices, don't forget controlling solar gain! Blocking the sun in the summer but allowing it in the winter will probably be more helpful than any single other thing, assuming you're following standard practices with the rest of the place.
I missed the dscission and lecture on using the word efficiency. I personaly don't like it either, but that is how they sell HVAC packages. Same thing applies to refrigerators and other appliances. Even SEER numbers have been used to "rate" unit efficiency.
I agree totaly with the solar gain statement. The house I am currently building was designed for passive solar. I am still explaining to everyone that visits why it is "out of square to the world", eh, road.
Dave
I'm meeting with a rep from a local (Western Colorado) outfit, owned by a rural electric coop, that has done over 200 systems. I've got some reservations about the variety of soils & rock they'd have to drill through (it would be vertical), and the integrity of the piping and grout - it's one thing to replace a compressor in January or July, but if the ground source piping itself breaks...........
Any guesstimates on total system cost? Was that one figure 15k just for the loop installation? How much for the "furnace" itself? How quiet is it? Not much heat released at the point of the unit? Does condensate have to be drained?
Are we talking double or triple the cost of a conventional forced air (gas) system? Out here most use evaportative cooling, which is still probably more efficient that ground source, unless you get a humid day (we spent over a month in SINGLE DIGIT relative humidity this summer)
Actually the vertical loops that i have seen installed are less prone to failure than the horizontal loops. In the earlier years of horizontal loops there were some problems whith leaks, but with the better grade of polypropylene pipe and the heat welding, I haven't heard of any recent problems. In vertical loops if a leak occurs the only thing that is dug up is the loop manifold (about 6' deep) where the multiple loops tie together and home run to the unit. Loops are not taken out, but abandoned in place and a new well bored. Horizontal loops can be treated the same if there is enough room. If not the leaky loop has to be removed, and the new one installed in its' place.
The 15K figure quoted was for the unit under discussion. That generally is the total install. Unit, loops and distribution system.
Noise is about the same as for a standard forced air HVAC system. Maintenance is a whole lot easier. There are no condenser coils to clean and everything else is located inside where it not only stays cleaner, but is easier to service. (try to get a service tech. on a 10 degree day to come out on an air to air heat pump and see what kind of excusses they give). Heat generated by the compressor durring both heating and cooling cycles is calculated in, and accounted for in the unit sizing.
Yes to the condensate question.
If you have single digit RH you are beneath the recommended RH listed in the ASHRAE standards. Mostly the concern with low RH is the "dry throat and nose" type health issues. On the plus side, you never need to worry about mold growth either. With low RH you may want to ask your contractor about a two stage unit. These are units with two compressors, one large and one small. Depending on load demands and a humidistat, you may only need one of the compressors to run to satisfy the cooling demand. Don't get sold on one the multistage single compressor units. My contacts in the HVAC world generally agree that knowone has made a decent one for residential hermatically sealed units yet. Untill you get to the 20+ ton units they just don't do what they are advertized to do.
Dave
Thanks for the input. Met with my guy this morning & looked at the site. Since we're in the guesstimating stage he said a 5 ton, possibly 4 ton system for a 2300 sq.ft. house, and a ballpark of around $25k. Big uncertainty in drilling costs for a vertical system = he said they've been going up to 300 ft. deep, and we have an unpredictable mix of bentonite, sandy clay, sandstone, "claystone" etc. at least in the top 20 ft. or so. These guys, being an offshoot of a utility, are probably good at the engineering, but perhaps not as competitive on the construction end? (They only sub out the drilling & do the rest in-house) I'll have to check with their competition in the area, a long-established plumb-heat-refr-mechanical company.
$ 1/3 for the loop, 1/3 for the unit, 1/3 for distribution? $7-8K sounds a bit high for ductwork on a house that size (crawlspace).
a lot of information in this thread, i realize i am out of the loop but would like to ask a question. what about solar? i live in california and solar is being touted as the next thing. is it different for other parts of the country? isn't geothermal an unknown as to future activity? what happens when the source changes? it seems like a big investment on an unknown to me. for what i know of a solar system with electric appliances is a constant. yes amounts of sunlight will vary but even a geothermal requires electricity to operate the pumps yes? the thing i like about solar is that you sell back to utility the excess ( meter runs backwards during the sunny days) and with carefull calculations you install a system that makes the amount of energy you use on average and try to break even on utilities, you have a constant in cost of system.
> isn't geothermal an unknown as to future activity? what happens when the source changes?
If you're talking about true geothermal, such as lava flows near the surface, then I don't know. But if you're using the word to mean ground sourced heat pump, which is the popular meaning, the source is just regular ol' earth, and unlikely to change for perhaps the next few million years (depending on the second coming and all that).
Solar...every time my alternative energy specialist has done the calcs for a real project in real conditions, the numbers for the generation of electricity via solar have not worked out. The capital cost was too expensive to make the sale of excess worthwhile, especially when you factor in the time value of money. In other words, it still costs too damn much. In certain situations, such as if electric power is just not available to a site, it can work at a price. Solar hot water, on the other hand, is viable now in many situations.
As Cloud pointed out, photovoltaics don't yet work economically for most. Solar heating on the other hand is alive and well. Our next place will be 100% active solar for our supplemental heat. My system is well over 100% of need for every month but January. Then it's just a storage factor. This is 450 sq ft of collector in a climate with 48% January insolation, 4166 degree-days, and a 40,000 cu ft house. Most parts of California would be a piece of cake in comparison.
Ground source heat pumps do similarly to what I do, use the earth's mass to warm and cool the house. Difference is PAHS (passive annual heat storage) has no moving parts, nothing to wear out, and no $15-30K price tag. There is no unknown when you add and remove heat from the earth mass.
In Virginia, geothermal involving removal and replacement of subsurface water is not allowed by the health dept.PAHS Designer/Builder- Bury it!
"the thing i like about solar is that you sell back to utility the excess ( meter runs backwards during the sunny days) and with carefull calculations you install a system that makes the amount of energy you use on average and try to break even on utilities, you have a constant in cost of system."
In the long run that is going to backfire.
It will cause rates and polution to increase.
You are trying to sell "used goods" retail to the power company and then make them resell it for the same price to someone else. Where as they could buy "new" at wholesale.
And if you had a large number of solar homes doing this as soon as it became dark they the power companies would have to fire up the more expensive peaking units to replace this power.
Take a whole lot of solar powered homes to cause a generating facility to shut down even a small 3 o4 megawatt generator.
The peak power NG turbines are only allowed to run when a utility can not meet the load demand in its' service area, or an off system utility need the additional power, and is willing to pay the high cost of running a ppg. In our state we are only allowed to run peak power generators 4 hours per day per unit. With the coming increase in NG I will guess that megawatt cost for a ppg is going make them un-marketable.
I think as the energy crunch gets worse we will see a return to some of the co-generating facilities that were developed in the mid eighties. Take a production facility that needs steam for its process and use the steam to produce electrity as well as meet the production needs. Pollution controls for coal fire steam production is about the same as for a coal fired generator. With some improvements in fluid bed technology and the new generation of sulfur dioxide removal system the environmental impact of these small co-generating plants will actually help postpone the need to build more power plants.
Wind turbin production is coming of age also. It is even available for home owner use, but not very many developements will approve a wind turbin in your backyard. If you have the acerage, enough average wind, and the right deed restrictions they could be more viable than active solar.
Dave
I agree, in general with what you are saying.
But I still don't like the idea of net metering. It still cost the other users on the system.
I don't know what the studies show on the reliablity of wind power, placed in appropriate areas. But a mass of "individual" wind generators might generate enough power that they are a measurable affect on the system.
I suspect that you are right about the "industrial" co-generators.
Here Sprint has their headquarters and of course it is one of their major network points and so they need full backup power.
They have a large generator, maybe gas turnbine, on site and it is operated/managed by or in cooperation with the local utility. So it can run the Sprint campus alone or act as reserve for the larger system.
I think we are on the same page. the media seems to be hyping the need for more generation of electric power, and in some areas that may be needed. Deregulation has switched the burden from the generating plants to the transmission grids. The distribution networks seem to be holding up well from the major substations outward.
You may understand this better than I do, so feel free.... My thinking is that reducing the load on the demand side will reduce the need to import power through a outdated transmission grid. The problem as I see it now is that FERC is pushing the formation of RTOs (Regional transmission Organizations) that would have the authority to order utilities to build new tarnsmission line fro A to B areas in thier region and have all the region, say A,B,C,&D, utility customers fund the new line. While this looks great to areas like the NE that are having problems, it is unfair to the rural areas with lower cost and lower population densities to baer the big burden.
Being able to reduce the peak load need on the distribution side of the system by 10 megawatts would take about 6,000 homes being off the grid, or at near zeroe sum usage. That is 10 mw that doesn't have to wheeled in from say Cleaveland to NYC. Lines don't overheat, fusses blow, and systems fail in a cascadeing debacle like we just had. Because of the way our nations electric grid grew out of useage and load requirements it was never designed to wheell large megawatts of power across many different areas. If we need a nation wide infrastructure, then lets design and build it, but not at the expense of the areas that had the good sense to design, build and operate thier systems at lower rates than the energy hogs elsewhere. IMO deregulation was never about supplying this countrys energy needs. It was/is all about how to make more money whith what we already have.
Sorry about the rant. Sum zeroe usage at the consumer end, I guess is my way of getting back at the new breed of energy barrons that are fleecing all of us.
Dave
Some background data relative to the last few posts.
Did a large trade study in 1978-1980 for Carter/Brown's "MX racetrack" misslile deployment scheme, mid cenral Nevada to Utah. About 4 MW total power needed, constantly. No electrical grid in the area, so a clean slate trade study.
Options were solar, wind, localized true geothermal ("underground lava beds"), solar (only tracking concentrators considered as feasible), new nuke plant with distribution lines, new coal plant near 4 corners with distribution lines, and mini-pipeline with gasturbines every few score miles.
At the time, fuel cells looked like they were about to make a breakthru (it ain't happened YET folks) and an HBr regenerative system was envisioned to accompany the solar for energy storage.
For this 1980 cost scenario, a 25:1 tracking solar concentrator and fuel cell actually was a tie with the nuke plant for minimum life cycle (30 year) costs. The BIG plus was that over the entire deployment area, there had been ONLY 3 days straight without a full day sunlight over the previous 50 years. Anyplace else solar would have been a big loser.
Since then the greenies and fearmongers have shut down nuclear, environmentalists don't like the Navahos' coal, bird lovers fear wind turbines will kill a few xyz endangerd species, NIMBY for transmission lines (aka Cleveland/Detroit/NYC), etc, etc.
via Nasa Glenn funding (watch their web site) just installed in time for the June 23 HI solstice a 1.4 KW solar array as a test for possible space usage on Haleakala peak last month. Cost similar to a couple of houses in a new subdivision - go figure the $$ per kW-hr, when the 1.4 kW is only at Noon.
"efficiency rating for geothermals" 55% TOPS!
Figure the following comment out -- Simple Rankine cycle geothermal systems run up to near 35% efficiency, when coupled with topping and bottoming cycles, some of the best top 55%!
THAT is for geothermal heat sources, ground source heat pumps are a whole other matter.
Believe you are the ONLY person knowlegable enough in this thread to use GSHP vs. Geothermal. Do you know what marketing firm bastardized the correct technical terminaology, I don't know how it got started. Worked some with Rotorua geohermal and some small Nevada sites in 1978-1980, and know that most everybody in Klamath Falls, OR does have geothermal heat, plus a few other locations like Yellowstone <G>. How everybody else got to calling GSHP 'geothermal' is a mystery to me.
>How everybody else got to calling GSHP 'geothermal' is a mystery to me.
It's from the same people who invented "revenue enhancement" for "tax increase"!
I am aware of The difference in GSHP and true geothermal systems, but unfortunately marketing ploys have driven one term to replace the other. Rather than spin my wheels trying to correct terminology, I try to give what factual information I know about GSHP to those that ask. With the coming increase in NG prices we can expect a lot more interest in GSHP (i.e. geothermal). If the price increase stays for very long, the "payback" period for the high intial cost of GSHP will shorten considerably, and they will become more palletable.
Dave
Thanks for the information. I'm new to this and very unfamiliar with those heating and cooling systems.
We just received an estimate to install a vertical closed loop system on a smaller lot. At $15K, it is a little steep. Of course a horizontal loop would have been only in the vicinity of $9K.
Payback at current energy prices was around 18 years for our home, located near Chicago. However, most reports I have read suggest natural gas prices will skyrocket over the next decade. This comes not from environmentalists or consumer advocates but rather from industry expe
rts and wall street.
That said, geothermal might be a wise hedge against that future.
Thanks so much for your response to my question. You're probably right about the cost of heating going up. That's something I hadn't fully considered.
I quick insight regarding your original post. I have a former client that worked in the economic forcasting department of our local utility. he claims that the industry can foresee natural gas prices rising 50% or more over the next 5-7 years. There is a lack of offshore and coastal NG storage facilities, so we are unable to tap into foreign sources.
As utilities move away from coal (as they should) thre use of NG will outstrip supply. That means electricity will go up in most of the country as well.
Alan Greenspan gave a speach in the last few months indicating the same thing.
I can't read the tea leaves, but it looks like our energy costs will rise.
Good luck with your decision.