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Folks,
Before I bought my land I wanted to make sure there was water. The first well was 300-320 feet deep and made 1 gal a minute with water comming up to 30 feet. The second well made five and is 300 feet away from the first. The first well is about 50 feet from the homesite.
I have heard that geothermal is expensive because you need to drill a seperate well.Well I have two deep wells and one near the house. Please give me a rough idea if this is possible with the 1 gal min well.If it is sounds do-able I will call out a pro for a consultation and estimate.
Also would appreciate any good references on Geothermal or websites.
Thanks
Frank
Replies
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sorry about the double post- can't figure out how to fix it.
FB
*Frank: At 1 gpm and a 10F temp drop in the water (in at 60F? out at 50F - if post where you live, many variables about climate and groundwater temperature could be estimated), you can only recovery 5,000 BTU/hour. 10,000 BTU/hour if you can get 20F out of the water. 10,000 BTU/hour would keep my house warm down to ambient temperatures of -20F but my house is of modest size, really tight and well insulated. Most houses would need 3 times more heat input (i.e. 3 to 6 times more water flow). Like maybe your 5 gpm well? You will also need some place to put the water and your state likely has regulations about that. From a strictly hydrogeologic prespective, a 1 gpm well can't accept 5 gpm (if the head you impose is the same but opposite as the well test drawdown). So even if your state allows reinjection (some don't), that 1 gpm well won't work. Do you need to create swamp land somewhere? A shallow reinfiltration trench is likely a lot cheaper than another deep well. Good Luck, David
*dave is right on... also.. check the track record of the mfr.. probably still wet behind the ears.. the geothermal guys don't have a good history of staying in the business long enough to service the equip..and the equip. is high tech..(read.. expensive service rates)..spend your money on energy conservation strategy...it works all the time...
*Frank, Take a look at:http://www.geoexchange.org/They have a lot of info and links to manufacturers, etc.Larry
*Guys,Thanks for the responses. I am in central Virginia. Temp ranges 104 max to -10 at the worst. I think Ground water runs about 50-60 degrees. Most winter days are high of 40ish low in mid 20s.I was hoping I could make something out of the bother of drilling two wells. Looks like I should put the money instead into isocyn. insulation and a masonary stove. I can always water the garden with the second well. ThanksFrank.
*Frank,We also drilled a well looking for water. 805' later, quit at 1/2 gpm. Choose geothermal and quite happy. We have a closed-loop system with 1 1/2" pipe running down the well and back up, so we needn't worry about the gpm of the well. We were "promised" 48,000 btu/hr, and are measuring over 52,000 btu/hr. It's heating over 6000 sq ft. Once we are switched to Time-of-Use electric rates, we should be able to heat this place for
*Frank: I think you're on the right track now. An tight well insulated house gives you lots of low cost options for heating and cooling. It also takes a longer time to (thermally) notice a power failure.Jim brings up another kind of geothermal system which doesn't rely on the extraction of groundwater, just the thermal conductivity of the saturated ground and, to a lesser extent, the migration of groundwater to move heat to the well. Such a well's ability to provide BTUs is mostly a function of its saturated interval (and somewhat the soil types and groundwater velocity). Since you have a deep well, it may work for you. While the water cycled through the well won't be as warm as from a pumped well, there won't be as much hp needed to pump the water since it is in a closed loop.I know it's rarely done, but I've always thought that such system should run in the summer to warm the ground up. A big water-to-air HX to heat a hot well in the summer and another to cool off a different cold well in winter. With a single well, you hope the AC need in the summer replaces many of BTUs extracted in the winter. As an aside, your groundwater temperature is probably between 51 and 54, depending on whether the slope faces north or south. -David
*Frank,It's not either/or. You can do great insulation and you can do efficient heat/cooling production. In fact, you ideally WILL do both. If you trench from one well to the other, you'll have about 2000' of buried tube. We have 1700 (North Carolina mountains) and get 52000 btu/hour. Hot water in winter and cold for A/C in summer. Geothermals are efficient producers, too, beating air-based heat pumps, natural gas/propane, etc for energy output for a given energy input. Worth consideration, I'll suggest.
*David, I wrote my prior msg before I saw yours--I wasn't trying to answer yours in any way. You have lots more experience. I was just adding thoughts I forgot when my 3-year-old daughter yelled for help be/c she'd fallen into the toilet!!!Now, in response to David, we do AC in the summer for the reasons you mention. My installer is guessing that we have some reasonable underground water flow keeping the ground from getting colder from the heat extraction, be/c the efficiency has measured constant over the three months it's run. He expected a bit of a drop off and we haven't seen it. (We dug the well in a drought, so there may be more water than we thought.)Also, we have a water-to-water system, with RFH and a Unico AC system.It's all quiet, it uses energy efficiently, it's draft free, and we have no combustables. So far, so good. But like all said, it starts with a good thermal envelop.
*Jim: I'm not sure about having more experience. I've always been in places where water wells are 30-60 feet deep and so I think of geothermal as requiring water extraction. But when you have wells that are 100's of feet deep, then heat exchange within the well casing (and then ultimately to the formation), would be more attractive. Jim: I'm curious, what temp water is circulated out of the well? Versus the GW temperature? I've got a lot a other projects to finish first, but I may go this route for a radiant driveway. The sidewalk is already radiant (natural gas heated antifreeze) but to thaw snow on 700' of road would run >$100 per event. So a source of "free" BTU is tempting. But with 42F groundwater, that's a lot of pumping or trenching. -David
*>I'm curious, what temp water is circulated out of the well? Versus the GW temperature?I think the temp reaching the geothermal heat pump is in the 50's, but I'm not sure. I'll see the installer tomorrow and ask him. Ground water? Not sure either. Mountains of NC, so not too different from Frank's, I imagine.
*Guys,So local GT guy told me for my planned 3,000 sq ft house with r-28 wall I would need 4 tons worth of system (40,000 btu) at about $5,000 a ton. The price would include a closed loop using the well and about 150 feet of trench. So if I save $200/ month on heating and cooling (seems far fetched) it would take 100 mo (about 9 years) to break even assuming no other additional maintainence costs. This seems pricey. Do these prices sound realistic ? Frank
*Frank,Geothermal is the way to go for heating and cooling. If I was in your situation I would use the well hole for a closed loop and have additional holes bored for the rest of the loops. Granted this is a more expensive option up front but it is better to have one type loop system than a hodgepodge of different type loops. When they bore the holes ; two polyethelene pipes with 180s fused together are slid to the bottom of the hole. Once this is completed the hole is back filled with a bentonite grout.On the price of the system; if you are looking at just a forced air system I figure it would be about $11,000.00 without ductwork.(this might be low since I have'nt seen your house layout but his bid seems a little high; get a another bid.) Also, check with the geoexchange. I installed a 5-ton heat pump with a well system in 3400sq. ft. home a year and 4 months ago; installed a meter to read the KW useage. The first year operation was 594.00; which includes all pumping of water, running of heat pump and domestic hot water generation. With the price of fossil fuels you are looking at pay back of 3-5 years. Sincerely, Dennis Dostal Rice Lake,WI
*David, we're getting water into the geothermal at 56 and putting it back out at 47. The differential is good, and these temps have been consistent through the entire heating system.Jim
*Jim: You must have a fairly decent flow of groundwater past your well. I (back of envelope) calculate that you'd see a 13F temp drop by the end of your heating season if all the heat from the well was conduction through the soil. But a GW velocity of 4 feet per day through the soils around your well would be enough to convect that much heat to the well. -David
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Folks,
Before I bought my land I wanted to make sure there was water. The first well was 300-320 feet deep and made 1 gal a minute with water comming up to 30 feet. The second well made five and is 300 feet away from the first. The first well is about 50 feet from the homesite.
I have heard that geothermal is expensive because you need to drill a seperate well.Well I have two deep wells and one near the house. Please give me a rough idea if this is possible with the 1 gal min well.If it is sounds do-able I will call out a pro for a consultation and estimate.
Also would appreciate any good references on Geothermal or websites.
Thanks
Frank