Earth Air Heat Exchanger - Page 2

dhaslam · 09-15-15, 05:05 AM

It is very easy to make a seasonal heat store on the side of a steep hill. You can cut out a section of the hill, insert insulation, water protection and heat exchange pipes and refill it. It works in the same way as conventional heating/cooling with a heat pump but you retain practically all of the heat. I have much the same but it is constructed above ground with straw bale insulation and uses solar panels for heat because the house does not need cooling in summer. It probably wouldn't cost any more overall than a conventional ground loop system. You get about 50% better COP as well as needing as using a smaller heat pump. The advantage of using the existing hill is that it is completely hidden and stays dry inside.

Robaroni · 10-06-15, 05:30 PM

I've thought about this type of system also but for warm air in the winter. Looking at the charts you need to go down 12 feet to get stable temps.

Here's a pretty good evaluation:

Ground Temperatures as a Function of Location, Season, and Depth

I'm playing with a low power system with Peltier Junctions which is a little different but if I were doing your system I'd do it closed loop. Bury a 4 or 6" pipe and have it come into a sealed radiator so there's no outside contact.

Rob

MEMPHIS91 · 10-06-15, 07:58 PM

Thanks for the link, good info there.
I'm not sure what your saying by your post, are you saying a closed loop of AIR pipe? or water? It being 4-6" I am assuming air.

Robaroni · 10-07-15, 06:31 AM

Memphis,
Yes, The outside air from the tubes never reaches you. Think of it like you would a closed loop fluid system where the fluid, lets say, antifreeze only transfers the outside temperature to a radiator.
This way any bacteria is isolated in your system as you're just extracting the temperature differential from it.
I don't think it would take much, just a small fan blowing air through the radiator and if convection doesn't work on the tube to keep things moving a small fan in the pipe.
I guess you could run 2" pipe with water like the geothermal systems do, you would not have the COP gain of a compressor but maybe you won't need it.

Rob

natethebrown · 10-07-15, 07:34 AM

We live at roughly the same latitude and I have considered this as a possibility myself. As you well know, we have some serious humidity problems down here and that is a huge concern. Honestly, the ONLY piping I would use is that super expensive German made anti-microbial piping specifically designed for this application. Also, I would DEFINITELY couple the piping with an ERV (not HRV) system or small HVAC unit (one coil on input stream and one coil on output stream) to help regulate the humidity.

I think using the right type of materials, extremely good air filtration on the inlet of the earth-air HX system, and a method to remove humidity from air going into the house are the methods to success.

MEMPHIS91 · 10-07-15, 07:38 AM

Rabaroni, That's a very interesting idea. My brain instantly went to a heat exchanger. I was looking at building one anyway. Even if it was only 50% efficient it would be better than nothing. If I used it for cooling I would have to find a way to deal with the condensation on the inside coils/radiator. Thanks I will continue thinking on this idea!

Natethebrown, Would it matter as much if the air from the tube never reached the inside air? It could mold all it wanted to then, though I would still clean it often.
Radon is always a issue but not bad here. Again the air should never make contact with the inside air. http://county-radon.info/MS/Lafayette.html

natethebrown · 10-07-15, 07:38 AM

One more thing, I don't know if you have this problem where you are at, but we have pockets of areas with very high Radon. Something else to consider.

Robaroni · 10-07-15, 08:33 AM

Quote:

Originally Posted by natethebrown

One more thing, I don't know if you have this problem where you are at, but we have pockets of areas with very high Radon. Something else to consider.

I'm liking my heat exchanger idea more and more!
Rob

natethebrown · 10-07-15, 09:27 AM

Quote:

Originally Posted by Robaroni

I'm liking my heat exchanger idea more and more!
Rob

Yeah, with the Radon issue I will more than likely go with a Geothermal Heat Pump system. Plus, I have been told that areas that originally didn't have Radon issues may one day have them in the future due to plate shifts, aquifer levels dropping, and other natural and man made events.

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09-15-15, 05:05 AM	#11
dhaslam Lurking Renovator Join Date: Oct 2012 Location: Co Tipperary, Ireland Posts: 21 Thanks: 0 Thanked 11 Times in 11 Posts	It is very easy to make a seasonal heat store on the side of a steep hill. You can cut out a section of the hill, insert insulation, water protection and heat exchange pipes and refill it. It works in the same way as conventional heating/cooling with a heat pump but you retain practically all of the heat. I have much the same but it is constructed above ground with straw bale insulation and uses solar panels for heat because the house does not need cooling in summer. It probably wouldn't cost any more overall than a conventional ground loop system. You get about 50% better COP as well as needing as using a smaller heat pump. The advantage of using the existing hill is that it is completely hidden and stays dry inside.

10-06-15, 05:30 PM	#12
Robaroni Journeyman EcoRenovator Join Date: Jun 2013 Location: Delhi, NY Posts: 332 Thanks: 20 Thanked 53 Times in 40 Posts	I've thought about this type of system also but for warm air in the winter. Looking at the charts you need to go down 12 feet to get stable temps. Here's a pretty good evaluation: Ground Temperatures as a Function of Location, Season, and Depth I'm playing with a low power system with Peltier Junctions which is a little different but if I were doing your system I'd do it closed loop. Bury a 4 or 6" pipe and have it come into a sealed radiator so there's no outside contact. Rob

10-06-15, 07:58 PM	#13
MEMPHIS91 Journeyman EcoRenovator Join Date: Apr 2015 Location: Oxford, MS USA Posts: 496 Thanks: 69 Thanked 87 Times in 61 Posts	Thanks for the link, good info there. I'm not sure what your saying by your post, are you saying a closed loop of AIR pipe? or water? It being 4-6" I am assuming air.

10-07-15, 06:31 AM	#14
Robaroni Journeyman EcoRenovator Join Date: Jun 2013 Location: Delhi, NY Posts: 332 Thanks: 20 Thanked 53 Times in 40 Posts	Memphis, Yes, The outside air from the tubes never reaches you. Think of it like you would a closed loop fluid system where the fluid, lets say, antifreeze only transfers the outside temperature to a radiator. This way any bacteria is isolated in your system as you're just extracting the temperature differential from it. I don't think it would take much, just a small fan blowing air through the radiator and if convection doesn't work on the tube to keep things moving a small fan in the pipe. I guess you could run 2" pipe with water like the geothermal systems do, you would not have the COP gain of a compressor but maybe you won't need it. Rob

10-07-15, 07:34 AM	#15
natethebrown Apprentice EcoRenovator Join Date: Aug 2012 Location: North Alabama Posts: 167 Thanks: 0 Thanked 40 Times in 20 Posts	We live at roughly the same latitude and I have considered this as a possibility myself. As you well know, we have some serious humidity problems down here and that is a huge concern. Honestly, the ONLY piping I would use is that super expensive German made anti-microbial piping specifically designed for this application. Also, I would DEFINITELY couple the piping with an ERV (not HRV) system or small HVAC unit (one coil on input stream and one coil on output stream) to help regulate the humidity. I think using the right type of materials, extremely good air filtration on the inlet of the earth-air HX system, and a method to remove humidity from air going into the house are the methods to success.

10-07-15, 07:38 AM	#16
MEMPHIS91 Journeyman EcoRenovator Join Date: Apr 2015 Location: Oxford, MS USA Posts: 496 Thanks: 69 Thanked 87 Times in 61 Posts	Rabaroni, That's a very interesting idea. My brain instantly went to a heat exchanger. I was looking at building one anyway. Even if it was only 50% efficient it would be better than nothing. If I used it for cooling I would have to find a way to deal with the condensation on the inside coils/radiator. Thanks I will continue thinking on this idea! Natethebrown, Would it matter as much if the air from the tube never reached the inside air? It could mold all it wanted to then, though I would still clean it often. Radon is always a issue but not bad here. Again the air should never make contact with the inside air. http://county-radon.info/MS/Lafayette.html