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Old 10-07-2008, 10:10 PM
 
393 posts, read 976,605 times
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Anyone out there use geothermal to heat/cool their home? It's horridly expensive to retrofit a home but if you are building from scratch, it's not so much more than a normal HVAC, just the cost of the deeper digging for your well adds about $5K to the cost. The question is, do you really find it works as well as you'd hoped? How about homes that are off the grid and use battery power/propane?
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Old 10-07-2008, 10:49 PM
 
Location: Forests of Maine
37,215 posts, read 60,933,271 times
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Very few areas have Geo-therm hot spots.

For a few years we lived in one area that did, they built a Geo-therm power plant.

Geo-therm requires molten magma vents bringing hot lava from the earth's core up to near the surface, where the heat can be used to flash water to steam.

Having a million dollar power plant is one thing, to then use it to cool your home is another.

Perhaps you mean heat-pumps.

Heat-pumps have been tried in Maine, at least three different companies have tried, as well as the university. Heat-pumps do not work in Maine.

They require a great deal of power.
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Old 10-08-2008, 06:13 AM
 
Location: Waldo County
1,220 posts, read 3,916,205 times
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Quote:
Originally Posted by forest beekeeper View Post
Very few areas have Geo-therm hot spots.


Perhaps you mean heat-pumps.

Heat-pumps have been tried in Maine, at least three different companies have tried, as well as the university. Heat-pumps do not work in Maine.

They require a great deal of power.

Oh now, Forrest, you are absolutely incorrect. The author of the thread does in fact mean heat pumps, but heat pumps can source their "heat" from geothermal energy. Temperatures below grade level increase in temperature the closer to the center of the earth the source is, and it stablizes at around 50 degrees below about six feet depth in Maine.

To say that "Heat pumps do not work in Maine" is absolutely incorrect. You need to speak with companies like Maritime Geothermal in Pedicodiac, New Brunswick and Hallowell International right here in Maine. Both of these companies (among others) manufacture cold weather heat pump systems that work at least as well in Maine as any other heating system. Maritime Geothermal has been manufacturing ground source heat pumps for more than twenty years, and Hallowell International has an AIR source heatpump that uses a proprietary technology that will provide hot air for space heating at tempertures down to zero.

The issue is not that whether or not heat pumps will work well or not, it is in what application and by what means they work. There are many types of ground source heat pumps, including those that pull water out of a deep well which is what the thread author suggested. There are also direct exchange systems that flow coolant through a loop of copper or some form of polycarbonate snaked through trenches in open fields, as well as closed loop systems that run coolant down a deep well and back. All of these systems will work very well and the cost of the system initially is not greatly above the cost of a good old fashioned (?) oil burning furnace.

But the issue is not whether or not they work, but it is in the cost of retrofitting an older house, which includes proper insulation, and of course, the cost of the infrastructure to support the system. Drilling a well for the simplest of heat pumps might require the well to be drilled to 500 feet or deeper depending on the btu output required of the system which will be greater the larger the home being heated.

Heat pumps aren't magical devices. They work much like air conditioners in reverse, taking a medium..water or some form of antifreeze liquid... at one temperature and putting it under pressure to raise that temperature. This is an application of Charles' Law from basic chemistry really. So if the transfer medium comes out of the ground at 50 degrees, it goes through the heat pump where it is placed under pressure and comes out at some other temperature that is warmer.

The issue with heat pumps in Maine is the relative cost of operation of a heat pump, which requires electricity. I have wanted to use a heat pump system in the new, "off grid" home that we are planning to build, and considering that all heat pump systems use pumps of various types to pump up from a well, and then through the system, and electric compressors within the heat pump, AND then will require some sort of pump to circulate the heat, either through a slab, or into a heat exchanger that will require a fan to blow the warm air around, the electrical load that heat pump systems is simply too great for an off grid system. Maritime Geothermal's Nordic Heat Pumps apparently use 14 amp motors to drive their compressors, and it is highly unlikely that a hybrid off grid electrical system using passive solar arrays and a wind turbine with battery storage will be large enough in a residential setting to drive a series of 14 amp motors continuously...at least one that I could afford.

Heat pump systems like passive solar arrays are just as effective in Maine as anywhere else. They may not work in all circumstances but depending on the application, design and availability of power at a price point, they surely will work in Maine's climate.
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Old 10-08-2008, 07:12 AM
 
973 posts, read 2,365,567 times
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gcberry,
I happened to be talking to the owner of Harbison Plumbing in Houlton the other day and we got talking about the weather and he said he hoped it didn't change too quickly because he had 3 geothermal systems to put in this fall. He's already done quite a few. He installs the Nordic system that Acadianlion speaks of. If it's a vertical loop you use, you need 200ft per ton. I think it's more efficient to have several 200 ft wells rather than one deeper well, because of the pumping distance. If you have the land and can get deep enough, a horizontal loop is cheaper to install than the wells. I know Nordic has sold over 500 of the direct expansion systems (they use a refrigerant in copper buried in the ground (either grouted in a well or horizontal) I looked into one of those, but couldn't find anyone on this side of the border selling them (or installing them). Canadian dealers can't get the work permits to come across and do the work. With the number of satisfied customers in Canada, I'm very confident that a properly installed system would work just fine here in Maine. You will have more than 5 grand in the wells however. Every dealer I spoke with said one of the biggest mistakes is not properly sizing the system. So if someone tells you that you will need 4 200 ft wells, that's what you need. Don't try to stick it in your existing well that's 300 ft deep and expect it to pull enough thermal energy. It's basic math and physics that determine how much energy you can pull from the system. Undersized units are what gives the systems the bad rap that you hear about. You need a professional to do a heat load study of your place, then a professional to properly size the system that is required. Then you will have a great system that will pay for itself over time. And if oil stays high, that time will not be too long. In another year or two there will quite a few antedotal stories as to how effective these systems are in Maine, at least quite a few are going in up here in the County.
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Old 10-08-2008, 07:51 AM
 
Location: Forests of Maine
37,215 posts, read 60,933,271 times
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I listen to 'Hot and Cold' with Prof Dick Hill and Tom Gozce routinely.

They often speak of heat pumps [in comparison to geo-therm plants]. They do commonly speak of the companies in Maine that have been trying to make heat-pumps work here.

They sound very knowledgeable on the topic, and check on the industries progress often.
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Old 10-08-2008, 08:00 AM
 
Location: Londonderry, NH
41,478 posts, read 59,530,043 times
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Acadianlion - if you are going completely off grid I suggest you talk with Central Maine Diesel in Bangor about one of their Lister type diesel generator sets. These can run very happily on waste oil, bio diesel or petroleum diesel. You can set up a way to recover heat from the cooling jacket and exhaust along with the electrical generation. The electricity can be used to run the Groundwater source heat pump.
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Old 10-09-2008, 08:50 AM
 
Location: Florida & Maine
13 posts, read 42,882 times
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I am building a log home on slab o grade. I am using ICF's at a height of 48" and filling it with rocks and sand. I am using the volume as a heat sink and the energy will come from a deep well of 1600'. The water temp is about 68 deg F and I will circulate and transfer that energy to my slab. The spent water will discharge into a pond that I am building. Additionally the water will circulate in my concrete slab for my garage and driveway. I an building a windmill to produce the electric with a inverter and a bank of 16 batteries. Any comments will be appreciated.
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Old 10-09-2008, 05:09 PM
 
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eastonmaine,
Do some research on frost protected shallow foundations (FPSF) if you are going with a slab on grade. You would want to follow those guidelines I would say. The foam is very important both under and along the sides of your slab. Also, from the research I've done, the is a point of diminishing return if you are pumping your water too far. The energy to lift water 1600 ft is much greater than say having 4 wells 400 ft deep. I would check with an expert before going that deep and continually be lifting water that far. Also the state is getting involved in licensing systems. Don't know how far it's gone yet, but I'd be surprised if they don't outlaw the pump and dump systems pretty soon.
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Old 10-09-2008, 09:51 PM
 
Location: Waldo County
1,220 posts, read 3,916,205 times
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Quote:
Originally Posted by eastonmaine View Post
I am building a log home on slab o grade. I am using ICF's at a height of 48" and filling it with rocks and sand. I am using the volume as a heat sink and the energy will come from a deep well of 1600'. The water temp is about 68 deg F and I will circulate and transfer that energy to my slab. The spent water will discharge into a pond that I am building. Additionally the water will circulate in my concrete slab for my garage and driveway. I an building a windmill to produce the electric with a inverter and a bank of 16 batteries. Any comments will be appreciated.
I'd love to see the data that enabled you to arrive at the well depth, the water temp, the pumping resistances as well as the size and capacity of the pond. If you already have a DEP permit to build the pond information on how that process went, would be very interesting, too.

A well that deep will cost something in excess of $20,000, I would think, so it seems to me that you are well beyond a point of diminishing returns, if you think that pumping water from a deep hole will heat the slab.

What is the amperage, size and type of the 16 batteries, and what prompted that particular number, I wonder.

This is an interesting project, but without a method of bringing the water temperature up to a heating level, I doubt that the "heated slab" will actually provide heat. I suspect that you will need a heat pump in line to raise the water temperature to around 125 or more degrees before the slab will actually provide heat to the interior of a dwelling.
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Old 10-11-2008, 09:50 AM
 
Location: Florida & Maine
13 posts, read 42,882 times
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Quote:
Originally Posted by kellysmith View Post
eastonmaine,
Do some research on frost protected shallow foundations (FPSF) if you are going with a slab on grade. You would want to follow those guidelines I would say. The foam is very important both under and along the sides of your slab. Also, from the research I've done, the is a point of diminishing return if you are pumping your water too far. The energy to lift water 1600 ft is much greater than say having 4 wells 400 ft deep. I would check with an expert before going that deep and continually be lifting water that far. Also the state is getting involved in licensing systems. Don't know how far it's gone yet, but I'd be surprised if they don't outlaw the pump and dump systems pretty soon.
the foundation will be fully insulated under and specially the sides (since the greatest heat transfer is laterally). The slab will be sitting on a prepared )150' x 65') that is 5' deep filled with 12 minus rocks and compacted (i already constructed). Additionally I built a french drain to facilitate the runoff. The well pump will use elctric from the windmill.

Regarding the "heating" of the slab (i am installing radiant heat) I must say that if/when i meet the 68 to 70 degree temp it should have enough energy stored to meet the heating demands for most of the year. Additionally I am installing a Polaris water heater (170,000 BTU-Propane) for back up. I must confessed that I will mostly use this home from May-Nov and we will be in Florida Nov-May. Thanks for the input and challenges.
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