So I was sitting on the roof of my house the other day, drinking a beer (I'd been cleaning the leaves out of the gutters) and I noticed a warm breeze blowing on my elbow. It was coming from the downpipe. I realized that the sun was heating up the downpipe and the air inside it, and the hot air was rising out of the pipe.

When I got down, I felt the bottom of the pipe where it leads down underground to the soakwell. It was cool, probably 10 degrees cooler than the surrounding air. The hot air being drawn out of the pipe was drawing cool air from underground. So there was the start of my idea. Where I live, it gets very hot in summer, and energy is expensive when you're using it to cool down a house, so any free cooling would be a bonus.

http://img395.imageshack.us/img395/4777/heatpipeguttersmg6.jpg

If you look at the picture, you'll see that instead of running the downpipe on the outside of the house, you run it on the inside, against a wall, in a corner or something. Then the pipe exits the roof and runs along the outside of the roof. The outer roof pipe would be painted black to maximize the air temperature inside it.

As for the gutters, at the roof line, a common S bend pipe would contain a water trap, connected to the gutter. That S bend would allow rainwater to travel down the pipe freely in winter as normal, but it would force the air to travel right to the apex of the roof in summer.

The way it works is that the pipe along the roof heats up, and the hot air inside it rises. This draws cool ground air from the soakwell, and as that air moves along the pipe inside the house, it absorbs heat from the room, and takes it outside. The process would work exponentially according to the weather, ie the hotter the day it is, the faster the air would flow, and the more heat it would extract. The inside pipe could also contain baffles to slow down the cool air so it has more time to absorb heat from the room. The air out of the soakwell never actually gets into the house, so there's no bad smell or anything silly like that. Soakwells always have vents to prevent downpipe bubbles, so that's not an issue either.

It might not seem like much, but here, even dropping the temperature a few degrees is a great achievement.

And the great thing is it performs two functions for the price of one, and it requires no energy to run. What do you think?

Sounds like an interesting project, although I can't tell you if it'd work or not.

Sounds like an interesting project, although I can't tell you if it'd work or not.

Indeed. Really wonder how well it would work...

Do you have some kind of radiator to exchange the heat? If it's just one pipe going through a room it won't work nearly as well.

Do you have some kind of radiator to exchange the heat? If it's just one pipe going through a room it won't work nearly as well.

Yeah I thought I might need some kind of radiator type thing, but wasn't really sure how to approach that, since I'd be dealing with such low temperatures.

Geothermal cooling. I've been really interested in such a concept for a while.

Commerically, the way this works is that the solar chimney on top of the building draws air out of the building and replaces it with air cooled underground. The intake should be a pipe close to ground level (high enough not to draw in water) and you need a dessicator in the coolant system. This ensures maximum airflow as the air close to the ground (assuming its not sitting next to concrete) is denser than air at the exhaust pipe even without a heat differential.

You shouldn't pipe it through the walls because walls have insulation in them, and central AC doesn't duct the cool air through walls. Central AC blows the cooled air directly into rooms via vents.

As for radiators, you can perhaps use alot of car radiators buried deep in the ground. however, it would be better to get large intercoolers from big diesel trucks if you can find them, but they will probably be more expensive. In all, its probably going to be too expensive to go with car radiators or intercoolers, so you could probably just weld together a bunch of heat exchange fins and pipe the air directly through that. That would probably work alot better, if you can weld.

One of the things that is going to be important is to be able to clean out mold if it starts to grow. An ozonation system could be made in DIY style and probably work quite well and seamlessly to kill mold growing in the system. The dessicator should keep alot of the mold out since it won't be a moist environment, but its better to plan ahead instead of having to fuck around with it when its in the ground.

Argon, I don't think we're on the same page about the radiator... I was thinking of having the radiator inside the house to cool the air, not have air directly coming into the house. Underground air in the house presents way too many problems with mold and such, where a radiator would isolate outdoor air and indoor air, keeping everything nice and clean, and eliminating the need for the ozone system. Plus ozone is an indoor air pollutant and irritates eyes/nose/skin/lungs, so it'd be a bad idea to have any of that if the system was open. Wouldn't be so bad in a closed system, but hey, as long as the mold isn't clogging anything, there wouldn't really be a problem with it existing.

And while I have your attention, can we sticky the material bartering thread?

Your radiator idea sounds good for keeping the air supplies separate, but its not going to be as efficient. I think that you still need a dessicator and ozonator because if mld does start to build up it's going to tend to clog up the ducting, which is a health hazard. Because you need the equipment anyway, I'd just say that I would go with blowing the air directly in.

Your radiator idea sounds good for keeping the air supplies separate, but its not going to be as efficient. I think that you still need a dessicator and ozonator because if mld does start to build up it's going to tend to clog up the ducting, which is a health hazard. Because you need the equipment anyway, I'd just say that I would go with blowing the air directly in.

Thanks man, that made my day! :D

And I'd still keep them seperate. With your system on one hand, you have mold in the air, on the other, theres ozone in the air, and on both, you could have radon in the air.

Link (http://en.wikipedia.org/wiki/Indoor_air_quality#Common_pollutants)

Inefficiency would be a weakness of my system but without ozone generators it seems the cost would be reduced enough to allow for an equal or lower cost per sqft/°F lowered. No way to really tell without building it though, so at this point might as well agree to disagree.

And what do you guys think of a different heat transfer medium? I like water.


Oh, and I'm just going to hijack and expand the thread real quick. Since most of us are in the US and are approaching winter, what do you guys think about solar heaters? I initially saw something like this (http://www.instructables.com/id/Solar-Heater/) and decided it'd be a neat way to help with oil costs this winter. I have to go up on my roof soon to fix some shingles that were knocked down in a storm, and my parents think it's a cool idea, plus I got lots of lumber lying around. And oddly enough, some plexi.
Questions-
-Anybody built one? Comments?
-Regular glass vs plexi? Real glass is a lot cheaper and I already have a lot more of it
-Keeping snow off it passively?
-Best method of trapping heat?

This will be interesting...

Heating would be quite a challenge I think. However, isn't deep ground still about 60 *F no matter what? If so, you could just install an auxiliary heating system form a central air unit in the cooling system. There is still a problem of getting the air to circulate, so its a good idea to use install a fan inside the ductwork.

I would say heat some water using a black canister on the roof, but if you are using this in the winter its going to be hella cold no matter what because the heat is going to go into the water and then radiate out into the ambient. This is going to require a good deal of thought.

Also, I didn't intend for the ozonation device to remain on all the time. It's just there to kill mold, so it only needs to run occasionally.

I'm no expert, but it sounds like you're onto something.

(just my input)

Seriously though, this could be marketable if you threw a green sticker on the idea.... :cool:

Heating would be quite a challenge I think. However, isn't deep ground still about 60 *F no matter what? If so, you could just install an auxiliary heating system form a central air unit in the cooling system. There is still a problem of getting the air to circulate, so its a good idea to use install a fan inside the ductwork.

I would say heat some water using a black canister on the roof, but if you are using this in the winter its going to be hella cold no matter what because the heat is going to go into the water and then radiate out into the ambient. This is going to require a good deal of thought.

Also, I didn't intend for the ozonation device to remain on all the time. It's just there to kill mold, so it only needs to run occasionally.

I think it's 55° constant underground. I don't really see how it would be beneficial in a heating system though, as conventional systems heat the air inside the house, and the heat escapes through cracks/walls to the outside.
The only way I could see this being better is if someone wanted to constantly add new air to their indoor environment, in which case outdoor [super cold] air could be run down through a radiator in the ground to bring the temp to 55°, then heated up a bit more to the desired temp. This would be highly inefficient compared to the closed [well, as closed as possible] system for heating we use now, so it doesn't even matter.

I really like the initial idea a lot, though I'll stick with my idea of isolated air systems. Obviously even an active system would use much less electricity than an air conditioner, and even though a passive system could be electricity free, it would be much more difficult to fit on to already existing houses, so active would be good for retrofitting old homes. I might try this next summer to complement the solar heater I plan on making for this winter. I'm thinking pretty much a radiator buried maybe 5' deep running up to a radiator in whatever room, with a constantly running fan in between.

Note- I'm getting solidworks soon and an XP from RDP, so hopefully I can start doing quick CAD sketches of things to actually model our musings. I'm fuckin pumped! :)

My point about the heating system would be if it's always 65 or so you could just pump warm air inside. However, I forgot that the heat differential will be much less in the winter, possibly not high enough at all for air to flow.

I think instead of using the heat differetial in the winter, you can build a large box, with all sides thermally insulated except the top. Inside you can put galvanized steel water pipes running around as a heat exchanger. Cover the inside of the box with aluminum and paint the pipes matte black (zero gloss). Over the top, you can place a one-way mirror oriented to where you can look inside. Also, you can place a thermally insulated glass pane (dual pane glass with argon between the panes) over the mirror so radiant heat comes in, but convection losses are minimized.

If you have a large ratio of black surface area to aluminum area, the light will be most completely absorbed and not reflected back out, therefore the inside will stay dark so the mirror effect will work correctly. This way, you trap light and infrared coming in and it can't be easilly reflected out.

Argon that's a super intense set up. I see where you're going, trying to minimize heat loss and such, but I saw one online where I guy built a flat box with 2X4s and plywood [might've been a little bit of insulation, but I don't think so], plexi on top, and soda cans painted matte black inside, and he heated his garage with it. Although yours would own this as far as efficiency, in the game of overall cost effectiveness, simpler is almost as effective and a lot cheaper in this case. Your design would be perfect in the city or somewhere you didn't have a lot of space or roof access to toy around with.

In my case, I got plenty of roof to build on and I think I'm going to try building a 2X8 panel [possibly bigger, depends on if I get some cheap ply] and face it east on a slant. I'm thinking a flat box of 2X4s and ply would work well, along with lots of caulking to seal it up, possibly some foam/fiberglass insulation depending on availability, conduit bent into a heat exchanger with my pipe bender, and insulated pvc running down into my window. I'll have a fan to move air inside up through the system and back, and hopefully it'll be sweet.

Oh and for the AC thing the conduit radiator also seems like a good idea. I could build two, bury one, run pipe up to the other [inside somewhere], then throw a fan in to move the air around. I'm opting for the closed system on both ends as I don't want to deal with mold/condensation/water build up in the pipes ever, so this way I'm safe and it should be maintenance free.

That is of course if I finish my other stuff I got going on. On overload right now, we'll see.

I'm more thinking of using it in the winter where you absolutely need to minimize heat lost to the environment. The sun is also not quite as intense, so it is a good idea to try to get the temperaure as high as you can. Hell yea it's overkill for the summer, but I was aiming for suboptimal conditions. Of course you might also be able to use a fresnel lens array to get a higher temeprature, of course that might get it too high for general use and would be more suited to driving a steam turbine.

I've seen some solar furnaces using a single projection TV fresnel lens get over 1000 *F. :)

I'm more thinking of using it in the winter where you absolutely need to minimize heat lost to the environment. The sun is also not quite as intense, so it is a good idea to try to get the temperaure as high as you can. Hell yea it's overkill for the summer, but I was aiming for suboptimal conditions. Of course you might also be able to use a fresnel lens array to get a higher temeprature, of course that might get it too high for general use and would be more suited to driving a steam turbine.

I've seen some solar furnaces using a single projection TV fresnel lens get over 1000 *F. :)

Wait, so is your idea to combine the two? Like run air through the underground radiator to the solar collector so it's easier to heat up?
I thought the plan to do it just with house air would work fine though, cause that's already just as warm as the ground air. If you didn't mean that... I'm not sure. This is where solidworks would really come in handy. I wouldn't use it to answer "how do i bild a gocart?", but hey, if we got complex systems and shit, it'd sure be useful.

Overkill- I meant overkill in winter. That dude online was getting some good temps, I don't think you need to over engineer the insulation of the box so much.

Fresenel turbine- How are we not powering our entire electricity need with this? What's so hard about building some cheap turbines and pumpin out some green electricity for free? 1000° can boil some serious amounts of water, and imagine like 5 focused on one spot. Just run a pipe through there made out of something difficult to melt [don't know metals well enough to pick one off the top of my head..]. There would be one on top with other lenses angled in from all sides so they have one focal point. Am I completely overestimating their power or is this plausible? I really want to make my house run off this when I grow up.

Shit dude, what about water purification in africa? Couldn't we make some solar furnaces out of metal or adobe for there so they could boil water to make it safe? That stuff seems to be a big deal, plus then they could desalinate at the coast and farm more. Fresnel lenses must cost a lot right? Something doesn't work here, what is it? I think if the government funded it or some philanthropist, the price could be brought down a significant amount per unit because of the volumes of lenses being ordered. Then we could solve all these fucking crazy problems!