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Forum Index : Other Stuff : Passive Cooling for your Home
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Greenbelt Guru  Joined: 11/01/2009 Location: United StatesPosts: 566 |
Something worth a kilowatt. Many people using this site are aware of the buried pipe for cooling the home, certainly there are some who are not. 130 meters of pipe buried 1-1/2 to 2, meters deep and a small fan, 20 watts. I could only find geothermal hot spot maps for Australia. Country's with Cold winters and hot summers will find this very effective for cooling because ground temp will be lower in higher latitudes. Could also use this as a closed air system for a heatpump evaporator. You may ask why not install a geo earthlink system for both heat an cooling?. $20,000 US quoted bid from 3 installers. at .08 cents KWH, = 480 KWH per month, 520 months 43.33 years I could buy power without the system for the same money. A rented trencher,Ditch witch, etc. will make a quick job if soil is not to sandy(falls in) 
Time has proven that I am blind to the Obvious, some of the above may be True? |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
I think that 20W of fan power pulling air through 130 meters of contorted pipe will be a struggle... Klaus |
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Loomberah Regular Member  Joined: 11/06/2008 Location: AustraliaPosts: 43 |
Under mosr circumstances your deep underground temperature will be close to the average yearly temperature, approximated by ((winter min + winter max) / 2 + (summer min + summer max) / 2) / 2 You'd generally need to be about 2m deep to keep the annual variation low, and you would probably need something like 150+m of 10cm pipe in a parralleled arrangement, (say 6 X 25m) and a 100+ watts of fan power to shift enough air to have a useful system in a medium sized house. I'm planning on setting up something like this at home, its not going to be inexpensive though, 100mm PVC pipe is over $20 per 6m length and Poly pipe quite a lot more than that. I'll be recirculating water on cold winter nights to cool the ground a bit more too. Gordon Loomberah weather +solar&UV, astronomy, photography, organic farm |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5029 |
Repost of missing post, this goes above Loomberah's post above. stevet47 wrote..... 68F for thrifty people.. lol, what am I then? I keep it at 60F during the day and 55F at night. CraziestOzzy wrote..... Geothermal heating is very much a reality, as is also geothermal cooling. In addition to our (anthropogenic) comfort raised by the OP, geothermal sourcing of energy is viable but must meet a wide range of criteria (geological and geographical to name but a few), which often excludes the majority of sub-surface exposures of geothermal activity throughout the world. ...having had my spill, I wouldn't mind my household water supply pipes to be slightly deeper than they are so I can have a cool drink of water during summer 
The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Greenbelt Guru Joined: 11/01/2009 Location: United StatesPosts: 566 |
HI- Loomberah I see you have done your homework. I was reading somewhere that dry earth conducts 1.2-1.5 BTU. per cubic foot per hour for each degree F. difference in temp. A 100 mm pipe is 1.03 ft in circumference, so 400 ft.(122)meters X 1.2 BTU at 25deg.F temp. difference = 12,000 BTU. I doubt the fan would have to be so beefy, 100 watts is equal to 341 Btu. this heat is either in the house ( if air is vacuumed through the pipe) or in the pipe if forced through it. also fast moving air generates frictional heat in the elbows and fitting ridges. It may be best to use a squirrel cage blower with speed control and mount the motor outside to radiate its heat. I'm working on my own Geo Earthlink with a water system for a heat pump. I have 179 meters) 19 MM. dia. pvc.in the ground. just waiting for some cash to get the rest together. I was not able to get 6 ft of depth here because of solid rock at 41/2 Feet. but I will move some dirt to fill over this. When I was covering the pipe with my backhoe I would test the pipe often to see if a rock had crushed it.Just like inflating a balloon I would blow through the pipe and check the return for airflow, I used 2 tubes in 1 ditch, 1 going in and 1 coming out then on to the next ditch completing a single path through the pipe. there was a little resistance when pressure was first applied it took about 2 seconds to get all the air moving but then it seemed very easy to move air. This is 179 meters X 19 MM. A 4" pipe of this length should handle 1 cu. meter per minute with a small fan. Perhaps it would not cool the whole house but the bedroom would be delightful on a super hot summer night. I would prefer a small amount of really cool air to a large amount of slightly cool air.I am hopeful you can get the cash to work on this but I know things are tough everywhere now. Time has proven that I am blind to the Obvious, some of the above may be True? |
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