05-24-11, 11:27 AM | #21 | ||
Supreme EcoRenovator
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Marginally Maritime...
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Where loop fields are concerned, size really does matter... bigger and deeper is better. For one, I under-estimated the effect that temperature changes close to the surface would have. I also learned there is also a temperature change time-lag (more depth = more time lag) factor that I now appreciate more than I formerly did. Last winter, I ran a test, using my little heat pump which I had previously measured to output around 4500 BTU per hour. I hooked it up to a car radiator and had a box fan blowing through it. I set it up in my basement which is not insulated and I let the thing run initially without any thermostat, for 24 hours a day, 7 days a week, for about two months. I had never used the radiator and fan setup before, but I just wanted to see how everything worked out on a sustained basis. All I logged was outside temperature, basement temperature, and loop water temperature. Since I only went down 17 feet, which is really shallow, my whole loop field is greatly subject to the transient temperature swings, but since the heat travels slowly, the effect was somewhat muted because the cold pulses (and warm pulses) took a while to work their way down. But still, whenever there was a period of unusual chill, I could see it clearly in the loop water temperature change about three days later... same for an unusually warm period. If there was a sustained 10 to 15 degree downturn... three days later, I would see my loop temp drop by two or three tenths of a degree. There was also a warming effect caused by significant rainfall... with a similar time lag as above. This diagram from the CLGS Installation Guide (#21020) book I mentioned previously helped me greatly in understanding what was going on... Long Term Loop Temperature Decline I also saw a steady, sustained decline in loop temp over a two month period, which was due to heat removal from the ground. During this time, on a couple of occasions, I turned the heat pump off for a day or two, to make changes in my heat pump setup, and I could see that the loop temp had 'sprung back' somewhat, but subsequent running of the heat pump showed that pretty quickly, within a matter of hours, not days, the loop temp worked itself back down to near what it had been before the equipment shut-off... which indicated to me that the full heat reserves take a considerably longer time to completely restore than I would have guessed. My conclusions from all of this... Where loop fields are concerned, size does make a difference... bigger and deeper really is better My initial idea of a shallow borehole loop field does work, but my optimism as to the total available heat is now somewhat tempered. In other words, I learned something from this experience. I would expect that there would be similar behavior from a loop field that was deeper and larger (larger in terms of loop filed size to heat load). I would suspect that a deeper field would reflect changes more slowly, and to a lesser degree. I would think that a bigger loop field would show similar changes but again, to a lesser degree. Assumption Error My calculation regarding boreholes, that... 200 = 200 200 = 2 x 100 200 = 4 x 50 200 = 8 x 25 200 = 16 x 12.5 ... is not correct, and that the shallower the boreholes are, the greater my error was. So a loop field composed of shallower boreholes will require more boreholes do deliver the required heat. I do think that a correction factor can be developed and that the above diagram holds the key to the formulation of this correction factor. Having said all that, I am getting useful heat from my loop field, and possibly enough useful heat to meet my original design target... because serious insulation is also part of the project. When I originally laid out my loop filed, I left enough space to add an additional 7 or 8 boreholes, which I can definitely use. Due to my arm injury, I may or may not be able to do it this summer, time will tell. Hybrid System When I started this project, I bought a small 3/4 Ton mini-split ASHP to see me through this project. The mini-split has worked out far better than I had anticipated, delivering reliable cheap heat, even on very cold (12 F) days, when it was obviously struggling to stay alive (low COP during that low temp, too). The climate in which I live has a pretty moderate heating degree day level of 4,000 to 4,500. Also, being as how Portland's weather is marginally maritime, heating requirements are fairly modest, compared to the central northern states & Alaska. In fact, there were a significant number of days this winter when the air temperature was higher than the loop field temperature. Those days are golden days for an ASHP. So, my current thinking is to combine a too-small mini-split ASHP with a too-small GSHP heat pump and leverage the best qualities of each. On the days when the air temp is higher, the heat loss from the house is not so high, and the ASHP is working at it's highest COP, so the ASHP alone is capable of doing the job... On days when the air temp takes a huge dive, the ground loop temp is looking pretty darn good, especially if I haven't been drawing it down all winter, then the GSHP comes into it's own. I still think that the best way to do the hybrid setup would feature a hydronic radiant floor. The GSHP is already a good fit, but my current ASHP is not. An ASHP hacked to be air-in and water-out would be ideal. So it is with tremendous interest that I am watching developments on the ASHP Hacks thread. Best Regards, -AC_Hacker
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05-27-11, 09:24 PM | #22 |
Lurking Renovator
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Depends on what state/county/city they are in and whether they are on their own property. It is not uncommon for people in rural areas to pound in sandpoint wells for watering their livestock. They sell the materials at my local farm store.
I've helped put in monitoring wells with drill rigs at hundreds of sites and installed monitoring wells with hand augers at dozens of sites and have thought about putting in geothermal wells at home. I would say that if you are drilling more than 30' deep you will want somebody with experience and some substantial drilling equipment even if you are in easily drilled soft clays. If you encounter sand below the top of groundwater or below about 10' depth you will want hollow stem augers to keep the holes open while you build the well inside of them. A twenty foot string of hollow stems is too heavy to lift by hand, so even if you get a little one man drill rig and can find somebody to lend you the augers you'll need something to pull the string out of the well. Rock can be drilled, but you definitely should have somebody with experience help you with that because depending on the type of rock you need to use different methods (e.g. down hole hammer vs. tri-cone bit). If I were to install geothermal for myself, I would go with horizontal loop because bedrock is shallow and problematic at my home. |
05-27-11, 10:28 PM | #23 |
Lex Parsimoniae
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Well, many of us live in areas (towns & cities) that have governments that need
to completely control and tax everything they can. (Too much time on their hands). Some of it is sensible and needs to be done, but much is just for revenue. Sometimes, it makes me think seriously about moving to the boondocks.. |
05-29-11, 02:06 PM | #24 |
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I'll throw one in here, as have done a couple of wells.
1st one we literally dug by hand (small air hammer, posthole digger, tripod over the hole, vacuum cleaner on blower for air. 30 in dia, 18 ft deep, supplied all our domestic needs for 25 years.. Then a 62 house subdevelopment went in 500 ft uphill, so needed a deeper well. From well logs of others (check you state registers) knew I'd likely hit good abundant water at a blue clay layer about 60-70 ft down, but heeded to go thru 55 ft of hardpan with occasional 3 ft dia bassalt and granite boulders. Tried a rotary setup first after welding up a 30 foot tower to bolt to the back of my dozer. Twisted the shaft off every trnsmission drive I tried when hitting a boulder (including a specially machined 2 in dia 4340 shaft as have a machine shop) Went with the old cable tool standby, welded some 4140 steel to the end of a few 5 inch billets of steel (aka old railroad car axles) and hardfaced them. Built a walking beam out of some 8" channel and 3 old trucks, drove with the truck engine. Biggest pump I have will pump 29 GPM, did that one august and pumped all day with no drop in delivery. Hit the blue clay right at 60 ft, 5 ft of sand above that. 'Only' took 5 months of spare time, but still have a rig if I need one again..<G> |
05-29-11, 03:53 PM | #25 |
Lurking Renovator
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had the baby, might be a bit before you see much in the way of updates from me... but i'll be paying attention when I can
Her name is Miette ;-p |
05-29-11, 06:16 PM | #26 |
Supreme EcoRenovator
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Mighty fine baby you have there... congratulations!
Best regards to you all... -AC_Hacker
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05-29-11, 06:25 PM | #27 | |
Supreme EcoRenovator
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Quote:
Do you have any photos or drawings of this rig? I have no idea what a walking beam is... -AC_Hacker
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05-29-11, 09:28 PM | #28 |
You Ain't Me
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Junkhound,
Keep telling the people at green building talk the truth! Their treatment of you is absolutely fantastic! When you plain tell them that they are soaking people for tens of thousands of dollars they can only respond with scorn. I don't care if it GSHP or something else. I am poor as dirt, and so are a lot of other people. And we need to keep ourselves and our families warm in the winter. And we shouldn't have to pay more than the cost of oil heat to think we're saving money, the planet and humanity. |
05-29-11, 09:38 PM | #29 | |
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Quote:
Makes sense that the blue clay would seal off the water so it would accumulate in the sand layer. How did you keep the hole open/clean enough to build your well in the sand? Around here at that depth wet sand usually wants to heave and flow into your boring. For what its worth a lot of drill rig transmissions share parts with commercial trucks (e.g. drivehead swivel=truck transmission U joint.) Unless you have your own junkyard and a lot a free time, it'd probably cheaper to hire a driller than to build your own rig. |
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05-30-11, 08:34 AM | #30 |
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it'd probably cheaper to hire a driller than to build your own rig.
Yah, but think of the fun I'da missed. I figured I spent about 250 hours building the rig, spent $300 on 8" and 6" sch 4 steel pipe, $80 on welding rod, had most the steel and etc. in my 'personal junkyard<G>. Likely 'made' less than minimum wage (but tax free), way less than 'day job' wages. Did have fun though. Pic for AC_Hacker attached. re: How did you get the rock chips out of the boring? Had 2 winches on the rig, big one to pull the drill (cable wrapped around a car wheel); and a small elec motor winch to lower and raise a bail made of a piece of 4" sq tubing with a flapper at the bottom. Drill 2-3 feet, pull the drill, lower the bail and bail out the rock chips and mud. How did you keep the hole open/clean enough to build your well in the sand? Drilled a 6" hole down to the sand (very fine sand), then jetted a 4" coarse screen into the sand layer to the clay - used an old 'scrap' pump to pump out the water, which was laden with the fine sand for about 10 hours, after which it has been clear water for many years. Wish I was young again like in the pic......parts were from '63 GMC truck, '71 Datsun, and '62 Impala.......probably would have more than paid to have the well drilled if I'da just put them trucks and car in storage till now??? |
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