AC rocket

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AC rocket

Postby thickstrings » Mon Jan 05, 2015 8:11 pm

I have just read Erica W's entry on rocket stoves in a warm climate at Permies...it got me thinking..[some times not a good idea] If a pipe were buried outside under ground 3-4' deep in a 20-25 ' loop, then into the cob bench inside of a building, then out the other side of the building to some sort of rocket stove outside....could enough cool air be drawn into the building to keep the bench inside cool in warm weather? I suppose it would have to be a closed system in order to draw the outside air......Just brainstorming....Any thoughts?
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Re: AC rocket

Postby matt walker » Tue Jan 06, 2015 2:09 am

I think so. Long buried tube in the earth, leading inside through some indoor mass like a bench, then open vented into the room. Then, a vent up high in the home, perhaps even a chimney type that protrudes a bit above the roofline and is painted black and in the sun. Warm days get the convective draft going, which vents the space, which drafts in fresh air from the buried inlet tube. Maybe? Would need to way oversize the inlet tube to minimize restriction.
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Re: AC rocket

Postby pa_friendly_guy » Wed Jan 07, 2015 3:12 pm

I agree Matt. The design I have seen for passive cooling [ and I think it also worked as a heating unit in Winter ] had a huge air pipe buried for quite a distance in the ground. It has been a long time since I have seen the plans but I think it was a 4 foot pipe underground that went into an envelope system that encased the house. As I recall the pipe started at a spot below the house [ down hill from the house ] and it had a naturel rise to the house. This envelope encased the entire house [ you really had to include this idea when you built the house, the house plans had 2 wall systems ] and the air exited out the roof area. Your home was encased in 56 degree air in the summer to help keep it cool. In the winter it was encased in 56 degree air to help keep it warm. Increasing the interior temp from 56 to 72 was fairly easy. Your idea of using a much smaller pipe and using a cobb mass to stay cool could work, but when it is 90 degrees outside it may be like trying to steer the Queer Mary with a row boat. :o The idea of opening a vent down low on the 1st floor on the wind side of the house and opening a vent high on the 2nd floor [ or at least higher than the 1st vent if you only have a one story home ] on the lee side of the house gives you a natural air flow that works with gravity. Having an outside air vent that is cooled by the air traveling underground for a distance and then entering the home, and being allowed to flow through the home naturally and exit at a higher point so after the air heats up it has a place to go does make sense. Its the volume of air needed to do the job that is a concern.
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Re: AC rocket

Postby 4seasons » Sun Jan 25, 2015 7:50 pm

In the past when I have seen this subject discussed, the consensus come to it will work but only slightly unless tremendous volume is used. If you think about it in term of heating it is very easy to raise the temperature in your house 30-60 degrees using a fire in a stove. The fire burns at a temperature from 500-2000 degrees. Since the fire is so much hotter than the house (despite the fact that some of the heat will be lost up the chimney) it is easy to gain a 60 degree increase from the outside temp. So by placing something that take up 10 cubic ft in your 10000 cubic ft house, because the stove is 50 times hotter than the outside temperature, it can warm your house to a comfortable level. However using underground air that runs around 50F to cool a house when the outside temp is 100F is only a 50% difference. So the math dictates that in order to cool the house to 75F you would have to move the same amount of cool underground air into your house as the amount of hot outside air can warm your house. So to use this simple average you would need at least the volume of your house in cool air to offset the outside temp. So unless you have a huge underground system (think caves) that you can access, or some tremendous insulation to keep the heat out, I doubt you would see much help with your cooling. My math may be a little off but the idea seem very logical.
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Re: AC rocket

Postby skyclad » Sat Jun 13, 2015 6:51 pm

I doubt if a rocket stove would move enough air to cool a home. But the idea has been used in coal mines for hundreds of years. Two parralel shafts would be sunk and connected by the work tunnel and a huge fire made in one to create a draft pulling fresh air into the work face via the other.
May I suggest an air scoop with a wind vane to catch ambient wind and force that through your home.
Also a old miners trick. Bonus needs no fuel and is surprisingly effecient.
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