Importance of type of grout (thermal conductivity) for vertical loops
Last Post 26 Aug 2014 03:27 AM by docjenser. 43 Replies.
Printer Friendly
Sort:
PrevPrev NextNext
You are not authorized to post a reply.
Page 2 of 3 << < 123 > >>
Author Messages
docjenserUser is Offline
Veteran Member
Veteran Member
Send Private Message
Posts:1400

--
01 Aug 2014 01:01 AM
Posted By jonr on 31 Jul 2014 10:02 AM
You might get the free evaluation of "Ground Loop Design" software. Probably full featured enough for learning about the effects of different grouts on loop length. And if you really want to have fun, rig up a water heater and do thermal tests (which aren't hard, the problem is that drilling a hole and then waiting a few days to drill more isn't so practical).

You could also buy "Grouting for Vertical GHP Systems" from IGSHPA. Also see table 4 here (roughly ~15% length reduction for .8 grout and another ~15% for double U-tubes).

This document seems to say that just bentonite should only be used with saturated, unconsolidated soils (not in rock).


This is when you might realizes that this discussion is academical. In real life you just drill 15% more, and get that for a lesser amount.
www.buffalogeothermalheating.com
jonrUser is Offline
Senior Member
Senior Member
Send Private Message
Posts:5341

--
01 Aug 2014 09:48 AM
> This is when you might realizes that this discussion is academical. In real life you just drill 15% more, and get that for a lesser amount.

Or in this particular real life case, the contractor doesn't drill 15% more and hopes that nobody notices the small performance reduction.


> Some of the contractors who gave me estimates use TC-enhanced grout around here and drill to the same depth or more
joe.amiUser is Offline
Veteran Member
Veteran Member
Send Private Message
Posts:4377
Avatar

--
01 Aug 2014 09:51 AM
"This is when you might realizes that this discussion is academical."

Exactly. When a new client or blogger talks about loop efficiency my eyes glaze over. I don't care how "efficient" it is, I care if it's adequate for the job and doesn't cost too much to pump due to gross over engineering.

One thing we haven't discussed RW is how little "a little extra loop efficiency" matters. One of the things newbs often ask is "if more loop is better why not just put a little extra loop in the ground?". I've repeatedly modeled projects and raising the EWT from just 30 to 35F might require 1.5 times the loopfield (adding thousands to the project) and save less than $50/yr in operating cost.

There are many ways to achieve the same operating parameters so the only one that's "better" is what your installer is best equipped to put in.

Some grouts are much harder to pump, double u-bends may require larger bores and more labor to install........drilling a little deeper is often the easiest of all.
Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort!
joe.amiUser is Offline
Veteran Member
Veteran Member
Send Private Message
Posts:4377
Avatar

--
01 Aug 2014 11:00 AM
"Or in this particular real life case, the contractor doesn't drill 15% more and hopes that nobody notices the small performance reduction."

....and when we say small, we mean miniscule. So many things impact loop performance, fancy grouts and loops are not particularly interesting to those who install for a living.

Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort!
Bill NeukranzUser is Offline
Veteran Member
Veteran Member
Send Private Message
Posts:1103

--
01 Aug 2014 05:52 PM
Posted By joe.ami on 01 Aug 2014 11:00 AM

... fancy grouts and loops are not particularly interesting to those who install for a living.



Unless you install for commercial structures.  Just happened Wed night to chat with my friend who indeed does this.  He's waiting to receive word on if his proposal is accepted.  1100 holes at 300' each.  They're not in to fancy loops, but they sure pay attention to the grout. 

Best regards,

Bill
Energy reduction & monitoring</br>
American Energy Efficiencies, Inc - Dallas, TX <A
href="http://www.americaneei.com">
(www.americaneei.com)</A></br>
Example monitoring system: <A href="http://www.welserver.com/WEL0043"> www.welserver.com/WEL0043</A>
waterpirateUser is Offline
Basic Member
Basic Member
Send Private Message
Posts:467

--
02 Aug 2014 09:10 AM
Is it grout season again allready???? I am glad I missed this. Grouts primary function is to seal the borehole from contamination, period. In accomplishing that, it adds insulation to the loop. You can either accept that fact or not. Addding TC grouts are an efffort to conteract the effects of the insulation properties of the bentonite. In a residential, no test bore done, design this is just blogging fodder talking about reductions or increases in efficency because there was NO data gathered in the TC test to base any subsequent choices/decisions on. In essance my favorite buzz phrase, GIGO.

The big differance between residential and commercial is how the load is applied. Commercial projects due their size demand that the data be gathered prior to construction to ensure that the load applied is going to be dealt with. Also note that with the heavy load of commercial projects, the load is also continuous. There are no spring or fall days when we shut the system down and throw open the windows. Commercial projects occupants also never go on vacation and set the thermostat to a minimum while they spend a month in FLA scuba diving.

Worrying about things is fun for some and bothersome for others. How you measure or track the effeciency of a system is a whole nother thread of a different color.
Cheers
Eric
Eric Sackett<br>www.weberwelldrilling.com<br >Visit our Geothermal Resource Center!
docjenserUser is Offline
Veteran Member
Veteran Member
Send Private Message
Posts:1400

--
02 Aug 2014 12:42 PM
Posted By jonr on 01 Aug 2014 09:48 AM
> This is when you might realizes that this discussion is academical. In real life you just drill 15% more, and get that for a lesser amount.

Or in this particular real life case, the contractor doesn't drill 15% more and hopes that nobody notices the small performance reduction.


> Some of the contractors who gave me estimates use TC-enhanced grout around here and drill to the same depth or more


I would argue that in this particular real life case the loop is already generously sized, so the addition of grout will not make much of a difference. Some people might not know where you get a good bang for the buck.
www.buffalogeothermalheating.com
rwgardnerUser is Offline
New Member
New Member
Send Private Message
Posts:42

--
02 Aug 2014 09:16 PM
Thank you all for the replies. This has been and is helpful.

Another question: What defines a "good" design? Should a good system avoid switching to electrical-resistance heat in the winter? Do we want to consistently achieve a good entering and leaving temperature difference through the summer and winter? Is it all about economics? (What should I be able to say about my system if it's designed well?) Thanks again.

jonr, the pointer to the design software is really helpful, as have been the studies you've pointed me to. I didn't realize you could get free trials. I'm going to check the software out as soon as I get a hold of a Windows machine.
waterpirateUser is Offline
Basic Member
Basic Member
Send Private Message
Posts:467

--
03 Aug 2014 08:21 AM
A good design is one that takes a " wholeistic " look at the economics for the entire project. That means that to achieve 100% of load coverage, may incur a install cost that can not be justified. Also the EWT and LWT is a range that is spread out over the entire year, and is a moving target of effecency, not any given snapshot. The pendulum effect or change in a closed loop system gives the shoulder months increased performance, while delivering chart performance during the heart of a given season.
Eric
Eric Sackett<br>www.weberwelldrilling.com<br >Visit our Geothermal Resource Center!
joe.amiUser is Offline
Veteran Member
Veteran Member
Send Private Message
Posts:4377
Avatar

--
03 Aug 2014 11:07 AM
"What defines a "good" design?"
That's is a good question. I think the answer would be very subjective to the designer. For me it is the most efficient system possible within the budget and a reasonable payback period.
For some it might be the most efficient system possible.

"Should a good system avoid switching to electrical-resistance heat in the winter?"
Absolutely not (in a heating dominated climate). Flee the installer who suggests auxiliary heat is to be avoided. Higher first cost and often higher operating costs are the result of that strategy. Common practice in the 80s-90s (when most systems were pump and dump) I would call the designer who avoids auxiliary in heating dominated climes "un-evolved" and I would suggest they be avoided.

"Do we want to consistently achieve a good entering and leaving temperature difference through the summer and winter? Is it all about economics?"
Common design parameters are 30-90F meaning EWT should rarely be lower than 30 or higher than 90. This is a design that ensures you get the most bang for the buck as return on additional loop (money spent) will be very nominal.

"(What should I be able to say about my system if it's designed well?)"

1 "I am comfortable"
2 "My bills Rock!"
Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort!
rwgardnerUser is Offline
New Member
New Member
Send Private Message
Posts:42

--
06 Aug 2014 08:57 AM
Posted By jonr on 31 Jul 2014 10:02 AM
You might get the free evaluation of "Ground Loop Design" software. Probably full featured enough for learning about the effects of different grouts on loop length.


On their website they say: "** DEMO VERSION SHOULD NOT BE USED FOR DESIGN PURPOSES. AS THE RESULTS FROM DEMO VERSION WILL BE INACCURATE. **". Do you know otherwise? (I'm obviously not about to build something from it, but are the numbers from the trial version any good?) Thanks.
rwgardnerUser is Offline
New Member
New Member
Send Private Message
Posts:42

--
06 Aug 2014 09:07 AM
I'm trying a trial of GeoAnalyzer.
jonrUser is Offline
Senior Member
Senior Member
Send Private Message
Posts:5341

--
06 Aug 2014 10:26 AM
DEMO VERSION SHOULD NOT BE USED FOR DESIGN PURPOSES.


Parts I've looked at appear accurate (ie, consistent with other sources), but that's the reason for "probably" and "learning".

Would be interesting to know how results compare to GeoAnalyzer.
tamarUser is Offline
Basic Member
Basic Member
Send Private Message
Posts:128

--
06 Aug 2014 10:43 PM
Posted By rwgardner on 06 Aug 2014 08:57 AM
Posted By jonr on 31 Jul 2014 10:02 AM
You might get the free evaluation of "Ground Loop Design" software. Probably full featured enough for learning about the effects of different grouts on loop length.


On their website they say: "** DEMO VERSION SHOULD NOT BE USED FOR DESIGN PURPOSES. AS THE RESULTS FROM DEMO VERSION WILL BE INACCURATE. **". Do you know otherwise? (I'm obviously not about to build something from it, but are the numbers from the trial version any good?) Thanks.


I downloaded and taught myself how to use GeoDesigner. It is free on the ClimateMaster website. Though it's interesting to see what changing inputs one at a time does to results, it is not a replacement for expert advice, by any means.
rwgardnerUser is Offline
New Member
New Member
Send Private Message
Posts:42

--
24 Aug 2014 12:49 AM
If it's of interest to anyone, I got a trial version of looplink to design my system and explore this; the results are as follows:

I estimated the ground composition to be 50 ft of unconsolidated soil/light clay (accounting for the overburden), followed by 100 ft of gneiss, followed by 100ft of schist, all with "average" moisture level/density. I based this off of information from the Maryland Geological Survey's website: http://www.mgs.md.gov/geology/index.html (I live on the piedmont.)

With these assumptions, looplink specifies 160 ft of bore per ton or 168 ft/ton adjusted bore depth for normal (.4 btu/hr ft grout). (The adjusted bore depth accounts for running the system for years and affecting the ground temperature over time. It's the estimated depth desired after running the system for about 10 years.) It says 119 ft/ton of bore or 128 ft/ton adjusted bore depth for .88 btu/hr ft grout.

I.e., for my area you need about 31% more bore for normal grout than for .88 btu/hr ft grout.

(I don't know what looplink's goal is exactly when it's deciding on the bore depth.)

If anyone is interested in the actual looplink reports, I can try to post them somewhere.
docjenserUser is Offline
Veteran Member
Veteran Member
Send Private Message
Posts:1400

--
24 Aug 2014 01:54 AM
I am sometimes a bit scetchi on the impact of the grout. Hard to imagine that the surrounding grout can now transport 31% more heat to the pipe. But I must admit that I have not monitored different grouts. My first .88 grout project will come up within 6-8 months. I guess I will report in a couple years.
www.buffalogeothermalheating.com
waterpirateUser is Offline
Basic Member
Basic Member
Send Private Message
Posts:467

--
24 Aug 2014 06:01 AM
You have just rediscovered the math of geothermal. What the software does not telll you is that these are guesstimates, that while proven in the lab with mathematics, sometimes the guess does not translate well into the field. It also does not take into consideration the extra labor and other carges associated with TC grouts that are applied by the installer. Further it does not address that loops are sold in standard lengths. Standard lengths are cheaper longer than some of the software generated hybrid lengths that are shorter.

This argument while it looks good to you on paper does not translate well into the field. Also be warned that the peidmont like most of the formations are wildly differing. The geological survey is based on computer modelling of a few test bores linked together with best guesses.

IMHO you should go with what ever the looper is recomending as a standard length bore for your location, then pay more for the TC grout and let us know in a year or so if your loop temps are 33% better than if you did not use TC grout.

I over looped my personal house to see the what differance it would make. 50% more loop for upstairs, 30% more loop for downstairs. It made a whopping 2 degree differance in my loop operating temps when compared to conventional systems. Hardly worth the effort.

Eric
Eric Sackett<br>www.weberwelldrilling.com<br >Visit our Geothermal Resource Center!
jonrUser is Offline
Senior Member
Senior Member
Send Private Message
Posts:5341

--
24 Aug 2014 10:51 AM
Nobody is claiming that increasing the effective length of a loop with TC grout beyond the normal length is going to produce a 33% difference in loop temps - that's a GIGO math straw man. The interesting question is if one can use TC grout and get the same performance at less cost. But there have been few posts providing actual cost data - ie, drillers quoted $x for 800' with normal grout and $y for 650' with .8 TC grout.
Bill NeukranzUser is Offline
Veteran Member
Veteran Member
Send Private Message
Posts:1103

--
24 Aug 2014 11:58 AM
Posted By rwgardner on 24 Aug 2014 12:49 AM

...

With these assumptions, looplink specifies 160 ft of bore per ton ...


Must be nice.  Here where it's hot (Dallas) the generally drillers these days are doing 300' of bore / ton.  At 10' per drilling rod section, that's 29 times the driller has to stop, add another rod, and then continue.  And the reverse too: pull out 10', stop, remove the 10' drilling rod section, pull out another 10', stop, etc.

Very labor intensive to do 300' bore holes.

I'm envious of your climate and soil, where you essentially need half the amount of bore hole length for the same tonnage of heat rejection/extraction than we do in the Dallas area.

Best regards,

Bill
Energy reduction & monitoring</br>
American Energy Efficiencies, Inc - Dallas, TX <A
href="http://www.americaneei.com">
(www.americaneei.com)</A></br>
Example monitoring system: <A href="http://www.welserver.com/WEL0043"> www.welserver.com/WEL0043</A>
jonrUser is Offline
Senior Member
Senior Member
Send Private Message
Posts:5341

--
24 Aug 2014 12:34 PM
looplink specifies 160 ft of bore per ton or 168 ft/ton adjusted bore depth for normal

And your existing boreholes are 160ft/ton. So pretty much perfect (as far as these guesstimates go).
You are not authorized to post a reply.
Page 2 of 3 << < 123 > >>


Active Forums 4.1
Membership Membership: Latest New User Latest: janvin New Today New Today: 0 New Yesterday New Yesterday: 0 User Count Overall: 34705
People Online People Online: Visitors Visitors: 160 Members Members: 2 Total Total: 162
Copyright 2011 by BuildCentral, Inc.   Terms Of Use  Privacy Statement