[Mesuge]

The heat pumps come in many designs as water-water or air-water cycle and much more. Recently, I've seen some diy designs utilizing the same components as used in the expensive products. Basically your are paying almost 2/3 of the price for the drill and you can't make it that cheaper. You can save only on the heat exchanget itself which is just a box with plumbing, compresor, gas and some electronics.. The magic is to have some extensive manual how to put it together (so far I haven't found one in English but in other languages are poping up).

A bit less efficient air-water system which doesn't need any expensive 120m drilling is in a sense inverted AC box and can be made for $2-3k with smaller COP about 3.0 => 1kW of electricity IN and 3kW of heat OUT. The system is not working efficiently under -5C but this shouldn't be an issue with rising global warming and you can always expand and have hybrid heating by burning some additional firewood if necessary. I've read that the compressor can last 30yrs, although the cheap air-water cycle heat exchanger needs more maintance due to condensing vapour etc..
The drill water-water system is basically no maintanance system..

Obviously you can get that state of the art system from major MNCs for $15-20k but I think this is an overkill for average user..

What I haven't heard addressed is the issue of soil<>heat exchange capacity decline around these drills. Yes it will function 10-15yrs. but there must be some decline in say 20-30yrs time frame - something like an aging battery effect. This effect has been observed when using shallow depth drills already (the first generation of this whole technology)..

[nocar]

$this->bbcode_second_pass_quote('', ' ')How common is this technology in Sweden?

[jpfrazer]

Hi - just to say there are cheap alternatives. As far as I understand at about 3m below ground, the earth reaches the average annual surface temperature. In the UK that's about 6deg C, in the desert in India where I'm building a hotel, its about 27deg C. This 'heat' can therefore be used for heating or cooling (in the Indian desert in the middle of night in winter air temp can be 5deg C - so the earth is a good heater; in the middle of the day in mid summer air temp can be 55deg C - so the earth becomes a cooler). The system proposed for the hotel, and I expect its possible elsewhere, is a passive air-based system. Scoop and suction/solar towers (think yacht) draw air through 40m long pipes at three meters depth- the cooled/ heated air then enters the rooms (via further passive cooling tanks from night radiative cooling systems if needed in the summer). The main cost is the tunnels, and the design time inventing & modelling the towers (mainly made of cloth and bamboo). No heat pumps are used in this system - just doors as 'valves' plus the tuneable sails of the towers to regulate flow.

[Keith_McClary]

$this->bbcode_second_pass_quote('Mesuge', 'W')hat I haven't heard addressed is the issue of soil<>heat exchange capacity decline around these drills. Yes it will function 10-15yrs. but there must be some decline in say 20-30yrs time frame - something like an aging battery effect. This effect has been observed when using shallow depth drills already (the first generation of this whole technology)..

[Starvid]

If you don't drill the hole deep enough it will cool down and the you have to make a new hole later. But with a deep enough hole from the beginning the heat will last forever.

[nocar]

Well, the guy who installed our system said that if houses very close together, like "town houses" or "terrace houses" (that are built with adjoining walls), each make a deep shaft for this, they can end up freezing the ground deep down. That is no good, because the system relies on water flowing in the bedrock cracks. He did not suggest combining it with air-conditioning, which would make sense - that technique seems to have developed since 8 yrs ago. And we had ample space around. And we have minor use for air-conditioning, so it has never been much of an issue - it always cools off at night here, even if a very occasional summer day gets hot.

It is almost always water flowing deep in the bedrock this guy said.

It is a little cheaper installing a horizontal system rather than a vertical shaft. I said "no way" because that means first digging up the whole garden with trees and all, and second that the ground will thaw somewhat later in the spring, some days later, is what they say. Since it thaws too late for my taste, not until middle April, that is a major drawback when the growing season is too short anyway. Getting the soil warm enough for beans and squash already takes forever. And then there is a risk of destroying the system if you dig deep in the garden.

But if you have a lakefront property it is very good to use the lake.

nocar

[Keith_McClary]

I have learned a bit more. The technology is better called "ground source heat pump" rather than "geothermal" (which implies volcanic or hot springs).

Some calculations I found on a government website indicate that it would increase my electric bill by $266/year to heat my proposed house with GSHP - much less than natural gas. And it costs me $250/year to be connected to natural gas, even if I don't burn any. So if I'm not connected to gas, $266 - $250 = $16. Sounds good. (GSHP hot water would cost an additional $150/year according to these calculations, but I don't shower that often).

[FatherOfTwo]

$this->bbcode_second_pass_quote('Keith_McClary', 'T')hanks for the information. I have heard that this technology comes from Sweden and there are only a few (20?) installations in western Canada. So I would worry that parts and service might be expensive. How common is this technology in Sweden?

[Kingcoal]

Geothermal heat pumps are becoming popular in the Pocono’s because most homes must use their own well for domestic water. A friend of mine has a system that cycles well water through a heat exchanger. He said that the air conditioning in the summer is almost free because the well water is about 45 degrees year round. In the winter, the heat pump keeps working because the coils are kept from freezing by the well water.

[PhilH]

$this->bbcode_second_pass_quote('BabyPeanut', '')$this->bbcode_second_pass_quote('Backpacker', '.') I'm thinking of going with FHP. link

[Graeme]

The Case for Geothermal
$this->bbcode_second_pass_quote('', 'G')eothermal heating and cooling is based on one simple fact: that 6 feet down in the ground the temperature is the same—between 50˚F and 60˚F- the whole year round. This means that it is relatively cool in the summer, and relatively warm in the winter. Geothermal heating is thus quite different from solar heating: solar heating works worst when you most need it--in the cold, cloudy, snowy conditions of winter; the source for geothermal heating and cooling is not affected by the weather.
For geothermal cooling, all one needs to do is to circulate water in a pipe through the ground to cool it, and use this cool water to cool the air pumped through the house in the heating ducts.
For heating, there is an extra wrinkle. Most of us prefer the temperature in the house in the winter to be nearer 70˚F then 60˚F, so we need to raise the temperature of the relatively warm air a little.

[Retsel]

My wife and I are installing a ground sourced heat pump for our house. We are installing an extra large unit to prepare for eventual expansion projects for our house. They are extraordinarily efficient, averaging over 400 percent in efficiency. They are usually more mechanically reliable as well compared to conventional furnaces.
Despite the higher efficiency, the very high installation cost (for our closed loop system) would not be justified at today's energy prices when we could install a 95% efficient furnace and an efficient air conditioner instead. However, the expected run up in natural gas costs as energy supply diminishes will greatly improve the return on investment.
I am looking forward to when the installation is complete.

[JRP3]

I've been wanting to do a GSHP myself, what unit are you using, how big is the ground loop, and how much of the cost is installation? I have my own backhoe so I'm planning to do much of the installation myself.

[JRP3]

Also, are you using long narrow trenches, shorter wider trenches with looped piping, or drilled holes?

[mekrob]

The units supposedly last for a good 50 years, which, if true, is pretty amazing compared to other energy appliances.

[IslandCrow]

I had a unit installed in November. The collector pipes are in a well drilled in the rock, 154 metres deep. All the costs of the system (including taking out a very old oil furnace) came to a rather high € 16 000.
I estimated that the total work came to about 8 man-days, not including the fact that we are about 1 1/2 hours drive away from where all the workmen and equipment was based.
Regarding payback. When compared to having to buy heating oil, at todays prices plus 5% fuel inflation, then I reckon that the payback time is in the 9-12 years range. This is a long time for such an investment.

[Kingcoal]

A friend of mine has a ground water based system that pumps well water, which is at the same temperature as the earth, through the heat pump heat exchanger. He tells me that his air conditioning in the summer is almost free and it works well in the winter. With his system, you have to keep after the mineral deposits as they build up quickly and reduce efficiency. I think this type of system is much cheaper than the kind where you install pipes in the ground.

[JRP3]

Do you know what he does with the water after it's done it's job? Does it get pumped back into the well or just discharged? If pumped back I'd think it would warm up the well in the summer and cool it in the winter, not what you'd want. If it's just discharged that seems wasteful. Not to mention I'd think it would take more energy to pump water up out of the ground than it would to circulate it in a horizontal closed loop system in the ground.

[frankthetank]

I believe the water has to be discharged. Would be nice if you could then use that water for something useful (agriculture, storage tanks of some kind). Wonder what kind of pumps they use? The submersible ones are pricey, and when used constantly probably don't more then 10-15 yrs.

I'll just put my ice shanty next to Old Faithful.

[Retsel]

For our ground source heat pump, we are using a Bryant/Carrier sytem model number GT-PX. It is very efficient. To compare between different systems, go to the ARI webpage: link

and you can compare between different ground source heat pumps. Another very efficient model is made by Water Furnace called Envision. A third unit employing a very interesting technology is a direct exchange unit made by ECR. These units avoid the need for a second heat exchanger by running the refrigeration loop, comprised by copper tubing, out to the yard and into the wells dug into the earth. This may be the most efficient of the bunch, without using an open loop. The drawback of this technology is that copper prices have skyrocketed increasing their prices significantly.

Open loop systems do have the additional lifting costs of moving the water out of the earth, but they are more thermally efficient because the water is always the temperature of the ground, while closed loop systems tend to heat the ground in the summer, and cool the ground in the winter. It would not surprise me if the ground around the pipes freezes in the winter caused by the heat extraction from the ground.

Our unit, for our planned house size of 2400 sq ft (including additions) will be costing us around $23,000 and that does not include the work that I must do to upgrade the electrical (this unit is on its own meter as the local electrical company charges a lower rate for this form of heating), and upgrade the current heating ducts from 4 inches to 6 inches.