New Hampshire Underground

New Hampshire Underground => Underground Projects => House Building => Topic started by: dalebert on November 07, 2008, 11:26 AM NHFT

Title: Costs for Geothermal?
Post by: dalebert on November 07, 2008, 11:26 AM NHFT
Anyone have any notion of what it cost to install a geothermal? Perhaps to incorporate it into the existing distribution system? Seems like it might be worthwhile for a large enough home and may pay for itself in time.

This site says the cost of installing a geothermal unit is about the same as a traditional forced air system and that it can supplement other systems. Sounds promising. Seems like the cost is easier to justify if you don't already have air-conditioning because geothermal can cool as well. Based on how it works, seems like it would cool even more effectively than traditional air-conditioners but I don't know for sure.

http://www.alliantenergygeothermal.com/stellent2/groups/public/documents/pub/geo_001407.hcsp
Title: Re: Costs for Geothermal?
Post by: SpeedPhreak on November 07, 2008, 11:56 AM NHFT
I can't find the issue - but Home Power magazine had a DIY article on building a solar collector/geo cooling system.

http://www.homepower.com/search/results/?sort=relevance&search=geothermal&columnid=&resourceid=&energyapplicationid=&articletypeid=&readerlevelid=&regionlocationid=&authorname=&issue=

lots of articles.

Sorry I don't know much outside that.
Title: Re: Costs for Geothermal?
Post by: dalebert on November 07, 2008, 12:24 PM NHFT
I don't want to fiddle with solar just yet. The technology isn't quite developed to the point of being cost-effective. I think it's getting close though and I'll be keeping an eye on it. May not be very viable in NH for a while. I think CA ppl will be able to justify it easier, sooner, with their weather patterns.

Geothermal, however, could make a lot of sense in NH where our winter heating costs can be quite significant. And it's kind of icing that it can be a cooling system in the summer as well considering that many NH homes don't bother with cooling.
Title: Re: Costs for Geothermal?
Post by: SpeedPhreak on November 07, 2008, 01:10 PM NHFT
I didn't mean solar electric.  The article I refer to consists of an insulated out building w/a good southern exposure.  The south side is all glass & there is a liquid (don't remember if it was an anti freeze or H20) in black pipes.  The liquid is heated then carried underground to the house to heat water & for radiant floor heating.  In the summer the liquid is re routed to only flow threw the under ground pipes & thus cooled - cooling the floor threw the same radiant floor tubing.

As far as the site goes - they have "real" geo thermal info too (I know what I described isn't exactly what you are refering to).  The whole magazine is about alternative energies for the home & focus a lot on DIY.
Title: Re: Costs for Geothermal?
Post by: ByronB on November 07, 2008, 03:39 PM NHFT
There are a lot of ways you can save energy, the trick is finding something that is cost effective...  it is awfully easy to find a way to use alternate energy only to find that you need to run a circulating pump(s) to get at it (that may use more energy then you are getting) and you may find out that your payback on your investment is a LONG time, plan carefully if the end goal is to save money.

The problem with geothermal is the ground is about 50 degrees (varies though) consequently it is a lot more efficient to cool with geothermal then it is to heat with geothermal, this makes geothermal more ideal for warmer areas where heating isn't as critical as in NH. In order to get a (traditional) geothermal system you would have to drastically oversize the system to meet your heating needs.

I'm not sure about the south facing wall with radiant floor heating/geothermal with floor cooling... cooling through the floor is a poor may to do it, it may sorta work in NH but in most places would just result in a hot, humid house with a constantly damp floor from condensation. Heating of course would be entirely dependent on how much sunlight you get on that wall... it wouldn't work at night when you need it the most, it may a better idea to simply have a lot of big windows facing South to get heat into the building.

Title: Re: Costs for Geothermal?
Post by: MengerFan on November 07, 2008, 04:11 PM NHFT
Here in the Ohio cornfields, I spent around $15k on geothermal. Went from paying hundreds per month on propane to paying about $20 extra per month in electricity during the winter and having a lower electricity bill in the summer. Totally awesome. With all the tax breaks, the savings is more than enough to make the payment on the 5-year loan to pay for the system.
Title: Re: Costs for Geothermal?
Post by: dalebert on November 07, 2008, 04:19 PM NHFT
Yes, I'd heard 50 deg ground temperature. In NH, that's quite high compared to the outside temp in the winter. The idea is to use a heat pump to draw that relative heat from there and pump it into your home. It's working like an air conditioner in reverse. I thought it was due to this relatively small temp difference vs. the outside, that geothermal was viable in NH.
Title: Re: Costs for Geothermal?
Post by: Lloyd Danforth on November 07, 2008, 04:50 PM NHFT
You need optimum or at least adequate Sun attitude for Solar.  All you need is a large enough area of dirt that you can dig down deep enough for Geothermal.
Title: Re: Costs for Geothermal?
Post by: KBCraig on November 07, 2008, 09:25 PM NHFT
The huge variable in a geothermal installation, is rock.

If you can drill in dirt, it's obviously much cheaper than drilling rock, and they don't call it the "Granite State" just because it sounds cool.
Title: Re: Costs for Geothermal?
Post by: dalebert on November 07, 2008, 09:31 PM NHFT
The huge variable in a geothermal installation, is rock.

Crap, I'd forgotten about that for a min.
Title: Re: Costs for Geothermal?
Post by: margomaps on November 07, 2008, 09:37 PM NHFT
I've read that a geothermal system is ~ 1/3 more expensive than a good "conventional" system (fuel-oil or propane or gas boiler I guess).  That 1/3 might be a little higher due to labor for drilling/excavation costs in NH because it's so rocky.
Title: Re: Costs for Geothermal?
Post by: Lloyd Danforth on November 08, 2008, 07:31 AM NHFT
Actually, I've seen a lot of digging in NH and I haven't seen any more solid rock than I have anywhere else in New England.
Title: Re: Costs for Geothermal?
Post by: dalebert on November 08, 2008, 07:34 AM NHFT
I don't understand why it has to be a forced air system. Seems like a heat pump could be used to heat or cool liquid for radiators or baseboard systems, or whatever.
Title: Re: Costs for Geothermal?
Post by: ByronB on November 08, 2008, 03:12 PM NHFT
I don't see how people come up with idea that geothermal is about the same price as a traditional system... basically you have pretty much all the same expenses PLUS the real big expense of digging around in your yard installing ground loops and don't forget... a backup heating system is pretty much essential.



dalebert:
The problem with using a heat pump for cooling via radiators is the moisture, it is kind of like taking a cold beer out of the frig, condensate forms on the radiators and on real hot humid days I've seen a room cooled with radiators in the ceiling have its own rain shower... I suppose it could be fixed by insulating all the piping and putting drain pans underneath the radiators but it still won't drop the humidity like a forced air system will.
Title: Re: Costs for Geothermal?
Post by: dalebert on November 08, 2008, 03:30 PM NHFT
dalebert:
The problem with using a heat pump for cooling via radiators is the moisture, it is kind of like taking a cold beer out of the frig, condensate forms on the radiators and on real hot humid days I've seen a room cooled with radiators in the ceiling have its own rain shower... I suppose it could be fixed by insulating all the piping and putting drain pans underneath the radiators but it still won't drop the humidity like a forced air system will.

Oh, that makes complete sense. I was only thinking of the heating aspect when I said that.
Title: Re: Costs for Geothermal?
Post by: MaineShark on November 08, 2008, 07:41 PM NHFT
The problem with geothermal is the ground is about 50 degrees (varies though) consequently it is a lot more efficient to cool with geothermal then it is to heat with geothermal, this makes geothermal more ideal for warmer areas where heating isn't as critical as in NH. In order to get a (traditional) geothermal system you would have to drastically oversize the system to meet your heating needs.

There is no "oversizing."  The system is sized to the heating/cooling load.

Often, we will actually undersize geothermal, by sizing it to the cooling load (typically about half the heating load), and using fossil fuel to cover the very coldest part of the year.

I'm not sure about the south facing wall with radiant floor heating/geothermal with floor cooling... cooling through the floor is a poor may to do it, it may sorta work in NH but in most places would just result in a hot, humid house with a constantly damp floor from condensation.

Properly-designed radiant cooling systems incorporate humidity control, which does not allow the floor to get below the dew point.

I don't understand why it has to be a forced air system. Seems like a heat pump could be used to heat or cool liquid for radiators or baseboard systems, or whatever.

The limitation is temperature.  Peak outlet temperature on a water-water geothermal system is 125 degrees, and efficient operation really needs the water temp to be 110 or lower (just using the higher temp for domestic hot water, not space heating).  That's not hot enough for baseboard, which really needs 140-degree water.  Large radiators can be used (sized for 110-degree water, rather than 212-degree steam or 180-degree water, as are typical), but that can cost a lot.  Forced-air uses lower temperatures, so it's often the most cost-effective way to use geothermal.

In-floor radiant can often run with lower water temps (90-110, depending upon the floor construction), so it can be used for heating, at least.  When the humidity is low enough, it can also be used for cooling.  Alternately, wall-mounted blower units can be used - they look sort of like a space heater, but are operated by hot or cold water - that eliminates the need for ductwork, and gives room-by-room control.

I don't see how people come up with idea that geothermal is about the same price as a traditional system... basically you have pretty much all the same expenses PLUS the real big expense of digging around in your yard installing ground loops and don't forget... a backup heating system is pretty much essential.

Unless you are intentionally doing a hybrid system, there's no need for a fossil fuel backup.

Regarding the costs, when folks say that it's similar, it's probably because they had a high-producing well, allowing them to run an open system, eliminating the cost of a second well.  You need about 2 to 3 gallons per minute for every ton of geothermal capacity.  Most houses use three to six tons of geothermal, so a well that can produce somewhere in the 6-18gpm range can be used without needing to drill any additional wells.  Of course, you also need to have a place to discharge the used water, so not all sites are suitable for open systems (if you have downhill neighbors, they probably won't like you dumping the water on the ground, to run down and flood their basement).

Geothermal is, in most cases, more expensive that traditional.  Almost anything "alternative" is going to be.  If it were not more expensive, it would not likely be "alternative" at all.  Fossil fuels are the norm because the equipment is cheap, and the fuel has been cheap for a long time.

Realistically, installed geothermal in NH costs somewhere between $6k and $10k per ton, for most cases, depending upon the specifics of the project.  Given typical residential sizing, that yields a $18k to $60k range.  Operating costs are very low, so the price difference can be paid off pretty quickly, in most cases.  Most geothermal installations will see operating costs in the hundreds of dollars, rather than in the thousands (like is the case with most fossil fuel systems).  There are also rebates from PSNH and other power companies, since they want you to buy their power rather than someone else's oil.

Of course, there is the disadvantage that geothermal is strictly a grid-tied system.  You would need a ridiculously-large generator to power a geothermal system in an emergency.  Most installations get a separate electric service with their own meter, due to the power demands, and because PSNH will often charge a lower rate for the geothermal power.  So, if your goal is to be off-grid, geothermal may be a bad choice.

What it all boils down to is that there is a huge range of options in heating, both in the conventional and alternative markets, and there's no one right answer for all applications.  Some folks will be best off with oil.  Others will be very pleased with wood-fired heating.  Some will love their geothermal.  And still others will beg used fry oil from the local restaurants, and heat their houses using that.

Joe
Title: Re: Costs for Geothermal?
Post by: ByronB on November 09, 2008, 06:28 AM NHFT
There is no "oversizing."  The system is sized to the heating/cooling load.

Often, we will actually undersize geothermal, by sizing it to the cooling load (typically about half the heating load), and using fossil fuel to cover the very coldest part of the year.
What I meant is that since the ground is colder then what you want your house to be geothermal is more efficient at cooling a building then heating, therefore if you size a unit to cover all your heating needs you will have a bigger compressor and ground loop then you need for your cooling needs... sizing it by cooling needs like you said makes the most sense if you are trying to get your moneys worth IMO.


Properly-designed radiant cooling systems incorporate humidity control, which does not allow the floor to get below the dew point.
Hmmm, tie in a humidistat to a mixing valve to control the water temp? I have never seen anything like that... I suppose it would work; however on real hot humid days it may cut your cooling most all the way off... unless you know of a better way.

I'm use to having a week or two a summer hitting the 100s every day with the humidity never dropping below 90% so maybe the standards I'm use to are overkill for in NH.

Unless you are intentionally doing a hybrid system, there's no need for a fossil fuel backup.
Maybe I like redundancy too much (or I've fixed WAY to many ACs that crapped out) but I'd personally like to see at least a electric backup for any heat pump I'm depending on to keep my pipes from freezing.

Regarding the costs, when folks say that it's similar, it's probably because they had a high-producing well, allowing them to run an open system, eliminating the cost of a second well.  You need about 2 to 3 gallons per minute for every ton of geothermal capacity.  Most houses use three to six tons of geothermal, so a well that can produce somewhere in the 6-18gpm range can be used without needing to drill any additional wells.  Of course, you also need to have a place to discharge the used water, so not all sites are suitable for open systems (if you have downhill neighbors, they probably won't like you dumping the water on the ground, to run down and flood their basement).
Ok, I see how the costs could be similar, thanks for the info, I was thinking of a closed system...

I've always wanted to cool with water from a well, only run it straight through a heat exchanger instead of using it for condenser cooling... we use straight city water for cooling at the hospital I work at in some rooms for a backup when something in our chilled water system goes down, I had to use it once for our MRI room... couldn't tell there was a problem even though it was summer.
Title: Re: Costs for Geothermal?
Post by: dalebert on November 09, 2008, 07:44 AM NHFT
I'm use to having a week or two a summer hitting the 100s every day with the humidity never dropping below 90% so maybe the standards I'm use to are overkill for in NH.

Ah, yeah, definitely. Cooling is almost icing in NH, really. I used to live in GA so I know the type of climate you speak of. Ugh. NH summers are really mild and pleasant. We get hots days, but they're rarely relentless and ongoing. We usually get plenty of breaks and nights are rarely anywhere near as warm as days so we get breaks from the heat, unlike GA where the humidity traps all the heat from the day and it stays miserably hot all night long.
Title: Re: Costs for Geothermal?
Post by: MaineShark on November 09, 2008, 12:20 PM NHFT
What I meant is that since the ground is colder then what you want your house to be geothermal is more efficient at cooling a building then heating, therefore if you size a unit to cover all your heating needs you will have a bigger compressor and ground loop then you need for your cooling needs... sizing it by cooling needs like you said makes the most sense if you are trying to get your moneys worth IMO.

Cooling is more of a convenience thing, around here.  Regardless of your energy source, the cooling load will be lower.

Solar energy (when available) can be used to boost the ground water temperature before it is sent to the heat pump, thereby improving the efficiency during the heating season.

Properly-designed radiant cooling systems incorporate humidity control, which does not allow the floor to get below the dew point.
Hmmm, tie in a humidistat to a mixing valve to control the water temp? I have never seen anything like that... I suppose it would work; however on real hot humid days it may cut your cooling most all the way off... unless you know of a better way.

Actually, a humidity sensor, with either a standalone PID mixing control, or tied into a computer that manages the system.

Radiant cooling has significant limits.  It's a supplemental cooling option, even here in NH.  It's extraordinarily efficient, so you run it as much as you can, but you still need something else if you want cooling on the really hot/humid days.  An air handler or ductless fan convector can be set up with a chilled-water coil, to operate when there is demand above what the radiant can delivery.

In new construction, or major remodels, we can also install tubing in the ceiling and even the walls.  A larger surface area can provide the same cooling at a smaller temperature differential, thereby reducing the amount of days when the cooling load exceeds the ability of the radiant to deliver without condensation.

Unless you are intentionally doing a hybrid system, there's no need for a fossil fuel backup.
Maybe I like redundancy too much (or I've fixed WAY to many ACs that crapped out) but I'd personally like to see at least a electric backup for any heat pump I'm depending on to keep my pipes from freezing.

It takes at least a day for a house to freeze.  Usually a couple.  Plenty of time to get a repair done.  Geothermal is no less reliable than fossil-fuel.  I've replaced more failed electric elements on heat pumps, than anything in the actual heat pump, itself.

If you want a real backup, it should be something with little or no electrical demand; if you're concerned about having something to fall back on, you want something that will operate if there is a power failure.

Or, you can go the other direction, and install a wood-fired system for primary heat (properly-designed systems can be operated on a generator, or even a battery bank), and then install a heat pump (probably air-source, due to cost) to provide cooling in the summer, and supplemental heat in the winter, if you go away for a few days and aren't home to load wood.  Air-source heat pumps are expensive to operate in the dead of winter (when they are mostly running on resistive coils), but if it only operates a few days out of the year, the operating cost becomes trivial.

I've always wanted to cool with water from a well, only run it straight through a heat exchanger instead of using it for condenser cooling... we use straight city water for cooling at the hospital I work at in some rooms for a backup when something in our chilled water system goes down, I had to use it once for our MRI room... couldn't tell there was a problem even though it was summer.

I have a stream on the property, and I'm considering doing the same thing.  I'm planning on a cistern filled by a solar-powered pump when the sun is out, and drawn from whenever the there is demand (with the warmed water discharged, not returned to the cistern).  Alternately, since the stream can get pretty low during summer, I may try and use a pair of larger cisterns - pump water from one, use it for cooling, and dump it into the other, where it cools back down due to the ground temp, then reverse the cycle.  There's no way that the ground will cool the water enough to make that work, in the time it will sit in a regular cistern (low surface area/volume ratio), so I'm thinking of a few short ground loops that either operate based upon pumps or even natural convection.

But, as you noted, cooling is not a high demand here in NH, so that's pretty far down on the list of priorities, due to the amount of calculation needed to plan it.  I keep hoping I'll get a client who wants something like that designed, and I can get paid to design something that I want to design anyway.

Joe