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Scott Davis

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Reply with quote  #1 

The aluminum downspout collector was my first hot air project.  The advantages it offers are that it works well in a horizontal configuration and it completely isolates your heated air from the rest of the collector. 




The downspout design is more expensive than the screen design and may not perform quite as well, but it will provide plenty of free heat and depending on your circumstances, may be the best choice:

Here is an overview of the aluminum downspout solar hot air collector:



You'll find more information here:

http://www.n3fjp.com/solar/solarhotair.htm

Here are a couple other examples of downspout hot air collectors:
 





Have you built an aluminum downspout solar hot air collector? Please reply and tell us about it here! Please be sure to include pictures if you can!

Do you have questions about the aluminum downspout solar hot air collector? Please reply, this is the place to ask about it! We will do our best to help!



 

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philsboat

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Reply with quote  #2 
Hi.I'm new to the forum.
I'd like to build the aluminum downspout collector but would like to use it as a solar heated fresh air supply to reduce dampness in our house.Any thoughts?
I would screen the intake air to keep out unwanted pests.

Phil
netttech

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Reply with quote  #3 
Welcome Phil!

Interesting idea. I don't think anyone in this group has tried that idea. I remember seeing a post with the similiar idea but it was a commercial panel, using performatted metal collector. It was being touted as a pre-heat fresh air exchanger though.

Have you decided on the size of the panel?

My concern is IF the panel isn't big enough it may not raise the temps hi-enough to actually produce warm air into the house. I don't know what your normal winter temps are outside, but keep in mind how much of a temp raise the panel needs to produce heating outside air, blowing it inside.

Your post indicates the dampness is already in the house...correct? I believe a standard Solar hot air systems would likely remove the dampness if you circulate the air within the house. I'll let other members answer that to be sure.

A down-spout is a proven good working panel. Admittedly I am biased towards dual-screen since it's easy to work with & cheaper to build. The performance is nearly the same between the two collector types. However, everybody has a different situation & if you think the down-spout fits your place the best...go for it.

Have you got a basic idea how you want panel to look? If possible, post a few pictures of the house, sketch of your panel idea, so we have a good idea of your plan.

Welcome to Solar heat...it's an addictive hobby!

Jeff
Central IL
philsboat

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Reply with quote  #4 
Thanks Jeff
I was thinking of a two downspout unit about twenty feet long across my southeast facing deck with the hot air piped into my workshop.
The low humidity outside air should dry the house and push moist air out through the range hood and bathroom fan vents.
I like the looks of the low profile collector as it blends into the house nicely.

Merry Christmas

Phil
Garage_Hermit

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Reply with quote  #5 
Scott, I checked out your Downspout Collector Vid several times, it's great and I want one for me !

In particular, the horizontal configuration suits my restricted basement location (see photo).

I have knocked out a preliminary schematic design (see enclosed PDF file).

The "unusual geometry" of my collector is due to the fact that I have a tightish location, but an adjacent facade wall, that would allow maximizing the collection area.

Thanks for any feedback!
 
Garage_Hermit

Attached Images
jpeg FUTURE_HYPOCAUST_LOCATION.JPG (440.46 KB, 582 views)

 
Attached Files
pdf Hypocaust_Downspout_Collector-Rev-3.pdf (76.65 KB, 149 views)


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charlie

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Reply with quote  #6 
Where did you get the fan for this project?  size, model etc?  Thanks.
NomadCF

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Reply with quote  #7 
So I'm getting ready to build my first aluminum downspout collector, and I was wondering something. Would "filling" the space/gaps between the downspouts with bricks (not concrete) or ceramic pieces help in any way. My thinking on this is that if we can "fill" the spaces with something with a high heat retention. That the collector will be able to function longer though out a day, more "evenly" though the day and possibly hotter. 

I can see a few downsides to this though, 
  1. The collector will take longer to heat up (possibly). 
  2. It will add a good about of weight to the setup. 
  3. Added cost
  4. A liquid would work better (oils, molten salt, etc). But I think a hot solid would be allot safer [rolleyes] and easier to handle.

Side though, maybe lining the the whole back with ceramic titles. And filling in the gaps with bricks would be even better ?
netttech

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Reply with quote  #8 
Fans can be purchased in various locations including Mendards, lowes, home depot. Better, larger fans can be from Furnace dealers, etc.

Nomad, you want to have good airflow & very little air flow restriction. I don't know what you have planned to build the panel, but keep it in mind.

I built a test downspout panel 2 years ago & didn't have any gaps between the spouts. They were all lashed together (side-to-side), airflow went thru, above & below the spouts. The spouts were slightly suspended above the panel backing.

Once the Down spouts get heated up, depending on the panel size, it generally will sustain the heat, all day. I compared two panels of the same size (2'w6'T) one with DSpouts & the other 2 layers of aluminum screen.

Very little differences in regards to air temps (5 degrees). The air flow was better with the DSpouts, & the Dspout panel took about 15 more minutes to heat up, but also took longer to cool off.

Good luck with your first panel! [smile]

Jeff
Central IL
Garage_Hermit

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Reply with quote  #9 
Hello, Nomad CF,

Quote:
Would "filling" the space/gaps between the downspouts with bricks (not concrete) or ceramic pieces help in any way. My thinking on this is that if we can "fill" the spaces with something with a high heat retention. That the collector will be able to function longer though out a day, more "evenly" though the day and possibly hotter.


I guess there are two schools of thought on the subject:

  •     one states that a collector should be low-inertia,
  •     one proposes high inertia "under certain conditions")

The idea with a low-inertia collector is to grab the heat into air, and evacuate the air ASAP, the idea being that lingering hot air inside the collector stands a greater chance of leaking energy back out via glazing, frame etc.

On the other hand, a high-inertia collector (such as a Trombe wall) employs the notion of thermal mass to store  heat, which is then restored over a longer period…

I propose a high-inertia collector at Item 5 above, this was a long time ago, and I have not YET gotten round to testing it.

Jeff at Item 8 above puts it nicely: not much difference as regards air flow, between a Downspout and a Screen collector: however, the downspouts take longer to warm up but they also take longer to COOL DOWN...

I'd suggest that your design choice ought to be conditioned to some extent by your site: if you are more west-facing than east-facing, then a high-inertia downspout collector will prolong your solar gain into your evening; on the other hand, it will be a late-starter of a morning…

If you have a more east-facing site, then go for a nimble screen collector: it will kick in earlier, reacting to those early morning rays of light…  However, it will also kick out *earlier* in the evening, perhaps leaving you feeling somewhat chilly…

If you have a dead-south-facing site, consider using two collectors, a nimble screen facing east of south, and a heavy-inertia downspout collector with lots of brick and SLATE in it, facing west of south…  That way, you should really get the best of both worlds!

Which brings us to an interesting comparison: the Earth itself: imagine for a minute that the Earth is a Solar Collector: it employs a heat-transfer fluid (air) which conveys heat arriving from the Sun in the form of electrogmagnetic radiation.

But the Earth also contains a large amount of thermal mass (the oceans): they take a long time to heat up, and also a long time to cool down...

So the Earth employs two types of media, water and air, and neither would work without the other…

Good luck with your build !

G_H

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(1)  "Heat goes from hot to cold, there is no directional bias"
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Scott Davis

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Reply with quote  #10 
Hi Charlie,

On my downspout collector I used a Fantek radon fan rated at 160 CFM.  I'm only getting about 80 CFM out though due to flow restrictions.

Hi NomadCF,

Unless your collector is inside an interior living space (unusual), you want to it be as light as possible.  The heavier it is, the more BTUs will be held out in the collector, which with thin glazing isn't insulated nearly as well as your living space, so you will lose more BTUs before they are ever brought to your living space.

Gary did a test on the downspout collector and found it did not perform as well as screen.

We want our collectors to be light and nimble, to respond quickly whenever the sun is shining, like a high performance race car.

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