[at-l] Geo Exchange

[johns12312 at snet.net (John Soboleski)]

Jim Bullard wrote:

> At 02:06 PM 12/20/2005 -0500, John Soboleski wrote:
>
>> Jim Bullard wrote:
>>
>>> At 11:10 AM 12/20/2005 -0500, Nightwalker wrote:
>>>
>>>> Jim Bullard <jbullar1@twcny.rr.com> wrote:
>>>> :: At 05:33 PM 12/16/2005 -0500, John Soboleski wrote:
>>>> ::: The efficiency rating for geo exchange is somewhere between 300%
>>>> ::: and 600%, depending on the application.
>>>> ::
>>>> :: 300% to 600%? You can extract 3 to 6 times the BTUs from the ground
>>>> :: that are in there? At no cost? That doesn't make sense.
>>>> ::
>>>> Jim, not seeing the stat and it's derivation, but I'm guessing that 
>>>> the
>>>> claim is that you get 3 to 6 times the energy out that it costs to 
>>>> retrieve
>>>> it. Mo betta?
>>>
>>>
>>>
>>> The usual efficiency ratio of energy production is energy produced 
>>> relative to energy expended. Unless the scientific law that matter 
>>> and energy can be interchanged but not created or destroyed has been 
>>> repealed, 100% is an impossibility much less 300 to 600%. Now if 
>>> they are talking about relative cost of production, that a cost 
>>> ratio or percentage not an efficiency ratio.
>>>
>>>
>> True. But this gives people "apples to apples" terminology to compare 
>> systems. The lingo may be technically inaccurate but I don't think 
>> they are being deceptive in their claim of an efficient system to 
>> heat/cool your home.
>
>
> Apples to apples? For the sake of debate (not argument), exactly how 
> did they compare costs? The claim that digital photography is cheaper 
> than film comes to mind. Those who argue it is cheaper will tell you 
> that you don't have to buy film and have it processed any more. True, 
> but are they counting that the average digital camera costs 3-4 times 
> it's film equivalent and if you aren't going to pay for processing 
> elsewhere you also need a computer and printer with expensive ink and 
> paper. For me digital is cheaper. I take 100 or more photos a day when 
> I'm out but I know lots of people who shoot less than half that per 
> year. For them it wouldn't necessarily be cheaper.
>
> I have neighbors who love to tell that they heat their houses with 
> only their sweat. They fail to mention that they had to buy a woodlot 
> (and pay annual taxes on it), a chain saw and they own at least a gas 
> hog 4WD truck if not a tractor and/or a 4 wheel ATV or two for hauling 
> the wood. I'm always suspicious of cost comparisons that don't detail 
> how they calculated it. The guy who inherited 50 acres and burns wood 
> from his woodlot for example may not be taking into account that the 
> guy he's comparing his heat bill to, doesn't already own a woodlot.
>
> In the case of geo-exchange are they factoring in the cost of digging 
> up enough of the yard and installing the required piping? Most folks 
> don't have the equipment and technical know how to install that sort 
> of thing for themselves. They'd have to pay a contractor who 
> specialized in it. I don't doubt that the cost of the energy input to 
> run the system could easily be 1/3rd to 1/6th the cost of a 
> conventional system but what does this system cost to install and 
> what's the life span vs conventional systems?
>
> I considered the well water heat exchange idea when I needed a new 
> furnace a few years ago but the cost of drilling another 60+ foot well 
> at roughly $125/foot plus buying a heat exchanger unit compared to 
> $3000 for an oil furnace settled the question pretty quickly for me. 
> The extra $7,000 that the geo-exchange system would cost was (at that 
> time) about 14-15 years worth of fuel oil and I'd have still have had 
> the annual expense (albeit a lower annual expense) of running the 
> geo-exchange system. The fact that I had to borrow the money to do 
> either option and pay interest on what I borrowed entered into my 
> decision too.
>
>
>
I agree the installation cost could be prohibitive, unless you can get 
partial funding from the state or local utility.
I started the thread by saying if I were going to build a new house I'd 
go geo-exchange, it's easier to cost justify in new construction.
The amount of pipe you need is 250-1000 ft per ton of cooling required 
(my house would need 2 tons) , the variables are soil conditions the 
weather that the house has to endure, insulation and orientation of the 
house. Typically they dig a trench and use large staples to hold the 
pipes horizontally (a foot apart) to the side walls of the trench. This 
way they get many linear feet of pipe per foot of trench. The picture I 
saw of a local installation looked like 6 horizontal pipes along the 
trench walls. Anything I've seen on the pipe says it comes with a 50 
year warranty. Soil temperatures range from 45-75 degrees depending on 
latitude (after all this is based on solar energy). This state, and many 
others, offer financing with a low enough rate to make it attractive 
economically. Banks will even use the projected lower monthly utility 
costs to help you qualify for the mortgage.  They claim the additional 
cost of the system, added to the mortgage,  is offset by the monthly 
energy savings.The actual operating cost cost for geo is in the power 
bill.  Just like cost for an oil burner are based on that oil bill. The 
best comparison would be identical homes with the two systems, or a 
retrofit. There are case studies out there, I'll dig one up if you're 
interested. There are more than 900,000 systems installed in the US, 
plenty of sample data. These are just the economics, add the 
environmental aspect and the claim that these houses are more 
comfortable than homes using conventional systems makes it worthwhile to me.
 
A case study I read about here cost $18,500 for geo and $16,000 for oil 
heat and a/c in new construction. The local utility company rebate was 
$2300 for the geo with conditions. The house has to be super insulated 
to qualify, who knows what the additional cost of that is but I would do 
it regardless of the heating system installed. The rock on site 
prevented them from using horizontal trench so they drilled two wells 77 
meters deep and used 305 meters of pipe, $8700 of the total system cost. 
This house was built before the recent oil and gas price spike and the 
estimated payback vs. oil was one year, gas was two years. I've worked 
with this utility and their energy conservation program. They are tough, 
know their data and do not invest in systems that do not match projected 
savings.

The environmental impact of this system on microorganisms exists but I 
would guess it's minimal. A properly sized/designed system should not 
alter the temperature of the heat sink very much, I have the 
documentation somewhere, and I'll forward it when come across it . The 
natural heating and cooling of the earths surface between winter and 
summer is much more dramatic, frost line here is probably 3 ft,  for 
example. 

Like all of these energy alternatives, people have to use what works 
best for them.  Conservation is key.

John