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Air conditioning and heating are major energy consumers in American buildings - commercial, residential, and industrial. I have been curious for a while as to why it isn't more common to use the practically constant 50-60*F temperature of the earth just a meter below the surface to bootstrap our heating and cooling needs.

More information on Geothermal heat pumps

As I understand it, the "ground loop" is expensive to dig but lasts for decades. And once the system is in place it's 40-70% more efficient than traditional HVAC on a single household basis.

What I'm really wondering is: why don't municipalities provide geothermal ground loops like they do sewage and water pipes? They could and should be laid together. Tapping into the loop would have some monthly service fee but only for maintenance, not for consumption (unlike water usage).

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The question of why they aren't more popular for individuals is an interesting one, but the follow on question of why municipalities don't provide the service may be getting off topic here. –  BMitch Jul 9 '11 at 14:46
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Imagine the difference between municipal sewage versus every building in a city having its own septic tank system. I'm just wondering if there are technical reasons why the municipal approach to HVAC doesn't work. The political ones are definitely off topic. –  Matt Chambers Jul 9 '11 at 15:06
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$$$$. The cost to install a system like you mention in an existing city, would be far higher than most companies/cities would even want to think about. And once they spent the billions of dollars to do it, then they would have to convince residents to switch over and start using it. The ROI would be so far in the future, maybe your grand kids would see it if they were lucky. –  Tester101 Jul 9 '11 at 15:29
    
@Matt: Welcome to DIY StackExchange. This site is for specific questions about building and maintaining a home, it is not the place for a political/economical debate. If you have a specific question about how to install or repair a geothermal system feel free to ask it, but if you are just looking to start a discussion this is not the place for that. Please check out the faq, and have a look at some of the questions asked by other users to get an idea of what types of questions are "On Topic" here. Again, Welcome to DIY.StackExchange. –  Tester101 Jul 9 '11 at 16:05
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@Matt: efficiency and cost; while interrelated, are not the same. Efficiency deals with energy consumption; which can lead to lower operation costs, but cost does not effect efficiency. The question in it's current form is subjective, and cannot be easily answered. Therefore, it is not a good question for this site. This is a question and answer site, not a forum. We welcome clear questions that have clear answers, not topics that require extended discussion. –  Tester101 Jul 11 '11 at 12:16
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4 Answers

The technology is relatively young, and not as well known to consumers as traditional heating and cooling methods. The upfront costs of a geothermal system are also higher, and there are fewer companies around with the knowledge and tools to install the systems.

In the US most homes are not built by the home owners, they are built by development companies who buy large plots of land and build as many homes as cheaply as they can on them. When they build these homes most of the products they use are "Contractor grade" (meaning cheap), so that the companies can make the maximum profit. Because of this, the builders typically will not choose a geothermal system over a more common HVAC system if the cost of the geothermal system is higher.

As for municipalities controlling a geothermal system, again this comes down to dollars and cents. If you were building a new city from the ground up this might make sense, but to retrofit a system like this would cost billions of dollars.

Hopefully as the "Green" movement marches on, geothermal and other "alternative" power sources will become more popular. And as they become more popular they will become cheaper, and the cheaper they get the more attractive they will look to average home owners and home builders.

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Of course I'm not suggesting that existing urbs or suburbs be converted to geothermal just for the sake of it. But why wouldn't a developer of a new subdivision plan all the houses with a common geothermal loop? That would surely be cheaper than putting a separate HVAC in each house. Lower cost on the house and long term maintenance is win-win. There'd have to be a homeowner association to maintain the loop though. I'm left thinking there's either a technical problem with sharing a loop or...developers are too conservative or not too clever? –  Matt Chambers Jul 9 '11 at 15:35
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@Matt: the problem is responsibility. Who will be responsible for the loop? when it breaks, who pays to fix it? The fact is, nobody wants that burden. Even you don't want it, as you are trying to push the installation cost off to the developers and the maintenance cost off to somebody else. It's just not economically viable at this point, in most cases. –  Tester101 Jul 9 '11 at 15:56
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That's what the homeowner's association is for. It would be required if it was a private loop. But if it was a municipal system, it would be paid for by property taxes and the aforementioned maintenance fees, just like sewage and water. I think it would be much CHEAPER than water and sewage actually. –  Matt Chambers Jul 9 '11 at 17:43
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The installation costs of geothermal are usually 2-10X more than a traditional air-sourced heat pump (10-20% of the total cost of the house). Trying to build a development with Geothermal would probably kill the profit margin of most real estate developers. –  msemack Jul 12 '11 at 12:55
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For the second part of the answer, I believe the general problem is the nature of a 'loop' -- the further it goes, the more likihood of shifting, or some sort of a problem, and when it happens, it'll take out multiple homes, and require extensive work to figure out where the problem / leak / whatever is.

The other issue is a simple question of what the responsibilities of municipalities are. Now, I can say this as I'm a town commissioner, and so an elected municipal official -- I think this is completely outside the scope of our municipal charter. The closest thing I can think of is that there was a development where they wanted to put in a dry pond for water storage to deal with possible flooding issues, and our town (before I was elected in) agreed to foot part of the cost of their connection to the storm sewer system (which is run by a larger entity, on the scale of the county, not the town). The reason was, we didn't want the nuisance of an improperly maintained dry pond.

In that case, the local water company woud be dealing with the long-term maintanance, not the municipality ... and I have no idea what would be all of the issues of maintaining a ground loop long term. but I know it's not something I'd be willing to get our town involved with anytime soon. (personally, yes, I'd be willing to do it to my own house, even with the comment about a house blowing up; but I don't think it's in the best interest for the town to get involved with ... if a new development wanted to do something, and have it managed by a homeowner's association, that's fine)

update : Fine, fine ... you don't care about the political reasons ... so here's my thoughts from an engineering persepective :

Electricity, sewage and water benefit from a central processing location, rather than smaller individually sized solution, assuming there's sufficient density of the places being transmitted to (using recent technology; it's possible it might change in the future for electrical production). In some cases (septic), it limits building density if you have to provide for it on-site, so there's benefit it moving it off-site entirely. In the case of geothermal heat pumps, you actually need the ground contact for the heat exchange, and unless you're transporting the water at sufficient depth, you'll have signficant transmission losses.

If a town/county/state whatever were to get involved, they'd be better off not trying to build a large ground loop and trying to maintain it, but instead either contracting for drilling for their residents and businesses, or including such expertise and equipment necessary in their budget, and doing it in-house. (but then we get into issues with should the government being doing it, or competitively bidding, but this one isn't supposed to be the political answer)

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Politics are certainly the likely reason this isn't done more often. That said, there are examples of municipal heating/cooling systems especially in metropolitan areas. For instance, St. Paul, MN has a municipal heating/cooling system connected to any downtown building that wants in on it. –  DA01 Jul 11 '11 at 16:26
    
@Joe: I chose the wrong word. Replace "municipal" with "city/county/metro/state government". Basically, think of it as a service like sewage and water (both of which are equally susceptible to the same problems of a large loop, and both of which are more significant for our lifestyles than heating/cooling). And I'll reiterate it is the technical challenges of a large loop/system that I'm wondering about, not the political ones. –  Matt Chambers Jul 11 '11 at 23:14
    
@Matt : see update –  Joe Jul 12 '11 at 14:41
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These are admittedly guesses...

The reason it's not more popular is that it's very new compared to the average age of most houses. Most houses have existing heating/cooling systems in place and it's easier to maintain/upgrade those than switch over to geothermal.

As for new development, at least in the US, the trend has been to maximize square footage and scrimp on everything else. Not a good trend.

There's also likely a geology aspect...if you're on rather shallow bedrock, you can only spread out horizontally which isn't viable in urban areas.

As for the municipality aspect, my guess is it's an issue of distance. The heating/cooling fluid would have to be transported across large distances losing a lot of its efficiency.

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Large distances are what makes the system efficient - it's all about getting the fluid back to ground temperature so that the house can sink or draw heat to/from it. I would guess that the system could work in serial. Between house A and B with water flowing from A to B, there would be enough pipe to resume ground temperature. And so on from B to C. I think it's even possible to do a horizontal loop by digging from the side, but it's probably just as expensive if not more so than vertical drilling. –  Matt Chambers Jul 11 '11 at 23:41
    
Good point. Though I don't know what you'd gain from serial over individual. You can do Geothermal horizontally, though, so perhaps there's some advantage there. –  DA01 Jul 12 '11 at 0:59
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Good answers all; and the central theme seems to boil down to economics...with a smattering of technical issues like property considerations and rights...perhaps to which we might even add risks such as striking pipelines (flammable and otherwise), conduits and such, or violating easements.

At the most fundamental level it would seem that earth imbedded exchange offers little if any cost-benefit advantage over free-air exchange systems already used in great numbers. Those, too, have the advantage of long lives--in the sense that systems wear out and are replaced or rehabilitated (without need or or concern about excavation; or interface obsolescence).

It is that disposability aspect also that works to the advantage of conventional applications of heat pumping. The time perspective of most all household HVAC systems is one lifetime (in which, usually, one or two to a few system upgrades will happen. Ground imbed systems, however, take on more the character of use in a situation of multigenerational occupancy. Because (especially residential) occupancy that spans over, say, an hundred years invariably goes beyond the purview of land use planning: AC systems are most likely to be designed only to meet shorter, more realistic planning time horizons Accordingly HVAC systems for single unit housing are not designed for "future" generations' utilization.

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