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Old 01-04-15, 01:50 PM   #1711
Geo NR Gee
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Interesting.

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Old 01-04-15, 08:07 PM   #1712
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Default diy cable tool

Couple of notes on cable tool drilling.

1st try was 45 years ago for drinking water - simple capstan and 200# bit with manila rope.
Got down about 10 ft and hit a basalt boulder - dead stop, bit just bounced - ended up HAND digging a 18 ft well that performed adequately for household water till the drought of 1987 - basically no rain from April till December.

So had to go deeper, could just 'do it' then as already had water rights, etc. Early 1990s there were new law and permit fees for drilling in WA.

Anyway, drilled down to 60 ft. Probably spent 500 hours of time building a tower, welding up walking beam on back of old Datsun truck, etc, etc. and drilling the well with an 800# bit. Some days, as when going thru a 3 ft dia basalt solid boulder (as evidenced by chips brought up) it was literally only inches per hour.

At the end, hit blue clay later at 60 ft with 5 ft of balck sand over it, pumped 29 gpm all day in July and no slow down of flow, biggest pump I had.

That all said, this last summer AT&T drilled a soil test hole 40 ft deep 100 ft from my well with a 3/4 million dollar rotary rig that only took them about an hour total !! - then filled it in immediately. They did go thru some 1 ft dia basalt boulders.

Moral or story. DIY well drilling is fine to do once, just for the knowledge and experience, but at an effective $$ return vs pro job I 'made' less than 1/2 minimum wage for time spent.
Would not do multiple wells - buy a backhoe and dig a lot of 15 ft deep trenches, then you have the backhoe to keep too. Or get a 'package deal' on multiple wells, half the hour cost of the driller for a single well is getting to and from the site.

Moral of story
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Old 01-04-15, 11:58 PM   #1713
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Quote:
Originally Posted by IWarm View Post
The label 'Ground source heat pumps' may be leading us astray. AC, you have repeatedly discussed the differing heat exchange rates of air and water when focusing on the HX. Yet, you haven't fully applied this knowledge to what happens under ground.
Well, I'll have to agree with you... life is short and learnin' is long.


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When you refer to rain as a 'heat event' I suspect you're simply too close to see that the heat carried by the rain is only part of the improved result. Perhaps the smaller part. Rain is also improving heat transfer from your normally dry ground.
I will agree with you that there is a dual nature to the increase of heat extraction after a substantial rain.

I'm also sure that the rain will increase the heat extraction because of the increased thermal conductivity of water, especially as compared to dry earth.

It helps to know that where I live, the earth is wet all winter long, so a heavy rain changes things from very wet to more very wet.

We get an annual rainfall of about 36 inches per year, and it is focused on the winter months.


The above chart illustrates the pattern of rainfall, and as you can see, our rainfall is substantially reduced in the summer, and occurs in great abundance in the winter.

Also, on the above chart, notice what our winter temperatures look like, and compare that to a similar chart for Oakham, MA.

You will see that our winters are milder than yours, even though we are on about the same latitude.

The difference is the steady weather that blows in from the Pacific. Here, in the winter, if it is clear, it is generally cold. If it rains, it generally gets warmer.

When liquid vapor condenses, it releases heat, no matter if the vapor is Freon, Propane, or water.

This process is at the heart of all vapor-compression refrigeration machines, and likewise, the weather.

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I suspect that many of the GSHP systems that fail to deliver satisfactory results are similarly located in dry ground.
You are right. However, the IGSHPA manuals supply tables that indicate the conductivity of various soils. You can still build a perfectly good GSHP system in dry soil, you just need to calculate the size of the loop field correctly. The IGSHP manual guides you through these steps.

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For those of us blessed with a high water table, when it comes to the storage of heat, it is important to know what type of water source we have, ponded or flowing. We have a glacial esker in the center of our property. When the truly artesian well was drilled, they logged 35' of gravel. To the east we have 100'+ of brook joining 800'+ of river. These above ground sources drop a combined 30' from north to south and are indicative of what is happening under ground. Our ground water flows from north to south. Any heat or coolth I take from the ground is quickly replaced from the north. Only those with a dry ground or a ponded water table can reasonably expect ground storage to hang around long enough to be useful.
I do hope this is useful. It is all I currently have to offer.
Thanks again,
Charl
Sounds very promising. I hope you post your project here, with lots of pictures.

* * *

While we are on the subject of GSHPs and boreholes and drilling, I just came across a most excellent paper on determining the conductivity of a borehole by experimental testing.


This method would be even more reliable than IGSHP tables.

* * *

Good luck!

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Old 01-05-15, 04:04 AM   #1714
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IWarm,

Some of the best performing GSHP systems in the world use aquifers or rivers as their primary heat exchange fields. A prime example close to me is the Galt House East hotel in Louisville. It uses the third largest geothermal heat pump system in the world, pumping 7 million gallons per day from the Louisville aquifer into the Ohio river. The 4700 ton system is said to save $300,000 in heating and cooling costs per year over the adjacent, original Galt House hotel building. The original building runs off centrifugal chillers, a boiler, and a cooling tower.
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Old 01-05-15, 09:08 AM   #1715
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quick math:

7e6/4700 = 1489 gal/day per ton

= 62 gal per hour

= about 515 # per hour; or 515 BTU per hour per deg F

Say incoming aquifer water is 60F, out = 35F (to avoid freezing evaporator)

delta T = 25F, so 25*515 = 12875 btu/hr,

how about that, the math is consistent with the numbers, did not look right at first.
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Old 01-05-15, 10:22 AM   #1716
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Quote:
Originally Posted by AC_Hacker View Post
...
It helps to know that where I live, the earth is wet all winter long, so a heavy rain changes things from very wet to more very wet.
...
-AC_Hacker
Yes, I understand that's how you see it.
I don't like to argue, so I don't.
As I read your drilling reporting, it seems to have said you found drier ground under a 'hardpan' and never found the water table.
Only trying to help.
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Old 01-05-15, 11:05 AM   #1717
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Originally Posted by AC_Hacker View Post
...
You are right. However, the IGSHPA manuals supply tables that indicate the conductivity of various soils. You can still build a perfectly good GSHP system in dry soil, you just need to calculate the size of the loop field correctly. The IGSHP manual guides you through these steps.
...
-AC_Hacker
Yes, but the commercial process doesn't include a geologic study or a follow-up performance analysis. 'Around here' rules of thumb are applied presale. Local knowledge will not always get it right.
Finding the water table will go far to insuring good performance and is likely to also minimize field cost.
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Old 01-05-15, 12:13 PM   #1718
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if you want to maximize performance and minimize cost you can never do enough measuring ahead of time. if you're doing it yourself, there is plenty of time to piddle around and take many many measurements. contractors usually don't have this luxury.
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Old 01-05-15, 10:46 PM   #1719
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Yes, I understand that's how you see it.
I don't like to argue, so I don't.
As I read your drilling reporting, it seems to have said you found drier ground under a 'hardpan' and never found the water table.
Only trying to help.
IWarm
I actually think that in some areas, there can be more than one water-bearing layer.

I believe that my general area is one of those, but I think that my specific location is not.

What I was trying to convey in the 'Manifesto' was that I hit a year-round wet layer at 17 feet, then hard pan... so I stopped drilling.

It is possible that if I went deeper, I might find more wet layers. However, I live on a bluff, with no higher ground anywhere close. There may not be any wet layers deeper down.

> Only trying to help

I'm not exactly sure what kind of help you are offering?


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Originally Posted by IWarm View Post
Yes, but the commercial process doesn't include a geologic study or a follow-up performance analysis. 'Around here' rules of thumb are applied presale. Local knowledge will not always get it right.
Finding the water table will go far to insuring good performance and is likely to also minimize field cost.
IWarm
I hope you noticed that I linked to a study, that might point the way for a DIY guy to do an analysis of a borehole.

But enough talk of theory, the proof is in the pudding.

I will very interested to see how your project progresses.

Don't forget to include as much project detail as possible and lots of photos.

This will help others who embark on similar projects in the future.

Best of luck,

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Old 01-05-15, 10:56 PM   #1720
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...
I'm not exactly sure what kind of help you are offering?
...
As titled, 'The Importance of Groundwater.'
IWarm

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