Author Topic: Solar Air heater for my shop...  (Read 12096 times)

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Tweety

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Solar Air heater for my shop...
« on: May 28, 2013, 05:35:42 PM »
Hello everyone!

I'm in the planning stages of building a Solar Air heater to keep my shop at half decent temperatures at a low cost...

The "problem" is that i have a few design constraints to work within, partly by my own doing, and partly imposed on me by my significant other, as she has a tendancy to look at the asteathics alone, and doesn't really care if it makes things difficult for me... ;)

Basically what I have to work with is a 80*195 cm doorframe on a south facing wall that lacks any practical usage... The building is a couple of centuries old, so I'm unwilling to make to large and permanent changes too it, partly because I don't want too, and partly because it would be next to impossible as the wall surrounding the door is made out of stone boulders in the 4-10 fot range, and the timber on the top part of the wall is 16" thick oak timber... So making any holes is a bit impractical to say the least...

So, as the space I want to heat is around 30m2 with 3m high cielings, and about 25m2 open up to the roof, about 6m high to the highest point, I'm trying to figure out the best way to get as high as possible efficiency out of the available space...

Frank S

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Re: Solar Air heater for my shop...
« Reply #1 on: May 29, 2013, 12:18:44 AM »
You didn't mention the direction of your roof and its slope or construction materials
 I am guessing you probably have the typical European clay tiles which are next to impossible to mount through them without shattering them.
  You will need several m2 of collector and a way to store excess heated air not as easy as one would think But you could construct an air to water heat ex-changer then use the stored thermal energy in the water to be circulated as radiant heat at night
 You might have a look at the following link I don't know anything about these folks and therefore make no claims or recommendations
 http://shop.new-energy-portal.com/background-information.html
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Tweety

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Re: Solar Air heater for my shop...
« Reply #2 on: May 29, 2013, 04:22:17 AM »
Sorry, I got interrupted halfway, and had to come back later... ;)

Well, the roof is out of the question, since it's straw covered... Not going to work at all, as you can't mount anything too it, and sealing around the potential holes is insanely expensive... The space I have to work with is the door, period, the house is listed as a historical building, so I'm limited in what I can do...

I know it's not going to be enough to keep temps too high, I'm just hoping to keep it from freezing... While not exactly insulated per see, as the walls are naked stone, once heated, they stay that temp forever, so all I need to do is maintain enough warmth...

My thoughts are to build a solar air heater, by making a timber frame in place of the old door frame, placing a pane of thinwall polycarbonate glasing, (10 mm channels) and using black corrugated metal sheets behind that as the absorber, and a "door" behind it of insulation and planks...

My thoughts are to increase the efficiency of that solar airheater as much as possible without making it hugely expensive...

I already have a 10W PV panel scavenged from an RV, to run two 120mm computer fans from, which are supposed to have a combined airflow of 160 cfm at full speed, and the plan is to make an intake at the bottom where I can select outside air, or inside air... The SO says she won't accept the PV panel sitting on the wall "looking unsightly" so it has to sit inside the SAH, meaning I need airflow over it, and can't use a backpass construction...

I was thinking that if I used two sheets of corrugated metal, I could place them so that they meet at the highpoints, making standing channels between them... By then allowing air in at the bottom, up and over one sheet, and down between the two sheets, I'm hoping it's a efficent enough design to heat the air... Then either a flat sheet, or another corrugated one to direct the air up to the top and out again... The fans will go on the bottom, as pusher fans, to prolong lifetime...

How do you all think the idea with the "channels" works? Will it be to restrictive? I'm hoping that the sun will be able to at least partially heat the second sheet of metal...

Frank S

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Re: Solar Air heater for my shop...
« Reply #3 on: May 29, 2013, 05:05:36 AM »
this leads me to think that since you have such a limited open area you might want to consider solar vacuum tubes and circulated water instead of air or if you have any sun side area detached from the building you might design an architectural landscape model and route the air or water through the door
 corrugated sheet metal  is not going to yield much in the way of thermal efficiency 
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electrondady1

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Re: Solar Air heater for my shop...
« Reply #4 on: May 29, 2013, 07:41:30 AM »
she can't be a swede, she must be a geat ! ;D (Beowulf humour)

why can't you build the size of solar heater you need  in sections and simply use the door  section as the  air entry/exit point. and the p.v area.

i know i will be building some solar air heaters soon.
i have seen designs using black bug screen as a heat transfer medium.
 that must be much cheaper than sheets of metal.
« Last Edit: May 29, 2013, 09:20:43 AM by electrondady1 »

Tweety

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Re: Solar Air heater for my shop...
« Reply #5 on: May 29, 2013, 10:09:09 AM »
this leads me to think that since you have such a limited open area you might want to consider solar vacuum tubes and circulated water instead of air or if you have any sun side area detached from the building you might design an architectural landscape model and route the air or water through the door
 corrugated sheet metal  is not going to yield much in the way of thermal efficiency

Well... If I had my way, I'd definetly do something like that... But anything detatched from the house means a building permit, as long as it's large enought to actually be of any use what-so-ever... And getting that on a listed house is a very long, and very, very expensive process... Not an option...

As long as it's attached to the surface of the house, and not an actual extension I get around the building permit rules... And if it uses an existing opening, like the door frame, I get around the need to get it pre-approved and rubber stamped in several instances based on the rules of keeping a listed house "looking intact"... Ie, if I replace the door with a SAH, it can easly be make back into a door, and the building is intact, which is a "loophole" in the rules... Also, it's not allowed to be "deviating from the look", by too much... So sticking panels on the entire facade, is not an option at all either... Getting approval for that is even less likely than getting a building permit... To give you an idea of the strictness of the rules... I can't paint the wood in whatever color I like... It has to be the classic red for the panels, and black for the doors and similar... Nothing else allowed...

As far as putting solar vacuum tubes there... Well, it's an idea... But it also requires me to run that water to a radiator somewhere... And it's making the entire thing a lot more expensive, than using material I already have as left over and free of cost... I might end up doing that as a next step, if I can't get enough out of the SAH... But, for now I'm going to test that first... So any help making it as efficient as possible would be great...

Tweety

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Re: Solar Air heater for my shop...
« Reply #6 on: May 29, 2013, 10:18:37 AM »
Well... I guess I should have lead with the fact that this a listed building... This got all upside down, when my posting was interrupted by real life... I'm simply not allowed to do anything but use the door hole, or the window holes if I choose to do that, but that would be fairly pointless... Simple as that...

I am allowed to use the roof, as long as I keep the straw roof intact underneath, but that's something that's entirely out of my budget as it would require a full re-build and renovation of the underlying structure to support it, and a full replacement of the straw roof once the structure is replaced and the mounts for the panels of whatever type are in place... So, for now, with the budget I have, it's the door, or nothing...

GaryGary

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Re: Solar Air heater for my shop...
« Reply #7 on: May 29, 2013, 11:13:47 AM »
Hi,

You might want to consider doing the collector with a flow through screen absorber.
This is some testing that Scott and I did a couple winters back comparing the performance of various air collector designs:
http://www.builditsolar.com/Experimental/AirColTesting/Index.htm

The simplest one to build and the one with the best efficiency was the one that uses two layers of black insect screening for the absorber.

I don't want to be discouraging, but you should not expect a lot out of this collector because of the small size.  I'd go ahead and do it, but, if it were me, I'd avoid putting a whole lot of time into it as its just not going to put much of a dent into heating such a large space.

Just some random ideas that might (but probably won't) get past your restrictions:
- Glaze the south wall in such a way that you see the wall through the glazing and that the glazing does not show up much to outside viewers.  The makes it a Trombe wall, and would be an effective solar heater for the space.

- Use a solar collector that is hidden along the base of the south wall -- there is a picture of one on this page: http://www.n3fjp.com/solar/index.htm
It barely shows up in the view from the street, but still provides some useful collection area.

- Look for an area in the yard around the building where you could put a detached collector, and duct the heat to the building.  Collectors can be disguised as fences (or other things).

But, bottom line is that you need more collector area.

Gary





Tweety

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Re: Solar Air heater for my shop...
« Reply #8 on: May 29, 2013, 06:08:06 PM »
Hi,

You might want to consider doing the collector with a flow through screen absorber.
This is some testing that Scott and I did a couple winters back comparing the performance of various air collector designs:
http://www.builditsolar.com/Experimental/AirColTesting/Index.htm

The simplest one to build and the one with the best efficiency was the one that uses two layers of black insect screening for the absorber.

I don't want to be discouraging, but you should not expect a lot out of this collector because of the small size.  I'd go ahead and do it, but, if it were me, I'd avoid putting a whole lot of time into it as its just not going to put much of a dent into heating such a large space.

Just some random ideas that might (but probably won't) get past your restrictions:
- Glaze the south wall in such a way that you see the wall through the glazing and that the glazing does not show up much to outside viewers.  The makes it a Trombe wall, and would be an effective solar heater for the space.

- Use a solar collector that is hidden along the base of the south wall -- there is a picture of one on this page: http://www.n3fjp.com/solar/index.htm
It barely shows up in the view from the street, but still provides some useful collection area.

- Look for an area in the yard around the building where you could put a detached collector, and duct the heat to the building.  Collectors can be disguised as fences (or other things).

But, bottom line is that you need more collector area.

Gary

I'm very well aware of the fact that I have a lot of room to heat, with a very restricted area to use... My hopes aren't that high, really... At the best, I think it might be possible for me to keep the room above freezing in the winter, and drive out the worst feeling of raw chill in spring and fall... And since I'm supplementing the heat with a woodstove for when I'm using the shop, hopefully the SAH might keep the heat I generate then in the walls a little longer, and reduce the time it takes me to heat the place up for use...

I think the experiment budget allows for some screen, even though I have the corrugated metal for free already... Especially since it seems the consensus is that my original idea won't work?

Like you guessed, none of the options really works for me, as the rules are to strict... But, the last option got me thinking... I saw a collector somewhere, were the builder had used plack PVC piping to make something that looked like a fence... I think it might be possible to perhaps pass it off as that, with a little smooth talking... At least it's worth pondering...

SteveCH

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Re: Solar Air heater for my shop...
« Reply #9 on: May 31, 2013, 08:57:13 AM »
I built a solar water heating system last fall [heavy reliance on the builditsolar web site referenced above] and it worked out well. I realize you are restricted, and with that building you already realize you won't "heat" the space with those restrictions. I would simply build the air collector you propose, using as many materials as possible that you already have [keeping cost to a minimum], and install it. See what happens. If it works better than expected, or anywhere near as much as hoped, you can be thinking, meanwhile, about how to improve it or build a better one. Plus, keep reading and researching possibilities. I am not so sure the proposed system will do much to keep the chill off, as at night you will have zero gain and those stone walls will be re-radiating heat, and it will likely take a lot of heat during the day to significantly increase any stored heat in the stones. It should help some during daytime. But give it a try and see. The sun is free and you have some materials already. The computer fans will increase efficiency.


gww

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Re: Solar Air heater for my shop...
« Reply #10 on: May 31, 2013, 03:56:00 PM »
If I lived in a place I couldn't touch I would move.  I know many people are proud and enjoy taking care of history but I can't stand anyone else being part of my decisions.

I don't mean that as a put down, I am glad people are different as long as they don't make decisions for my stuff.

I do agree with stevech.  I would do it with what I had and see how it went and go from there.

Good luck
gww

Tweety

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Re: Solar Air heater for my shop...
« Reply #11 on: June 01, 2013, 08:15:07 AM »
I built a solar water heating system last fall [heavy reliance on the builditsolar web site referenced above] and it worked out well. I realize you are restricted, and with that building you already realize you won't "heat" the space with those restrictions. I would simply build the air collector you propose, using as many materials as possible that you already have [keeping cost to a minimum], and install it. See what happens. If it works better than expected, or anywhere near as much as hoped, you can be thinking, meanwhile, about how to improve it or build a better one. Plus, keep reading and researching possibilities. I am not so sure the proposed system will do much to keep the chill off, as at night you will have zero gain and those stone walls will be re-radiating heat, and it will likely take a lot of heat during the day to significantly increase any stored heat in the stones. It should help some during daytime. But give it a try and see. The sun is free and you have some materials already. The computer fans will increase efficiency.

Well... That's what I plan on doing...

For now, apart from the salvaged PV panel and the computer fans, I have a very large pile of beams and planks, in about every variety of size's left over from the repairs and renovations already made to the house, and some random left over insulation, and a few sheets of corrugated black metal roof...

I also have large sheet of 10 mm thick clear plastic roof, the type with square channels making up the thicknes... Not brand new, as it's salvaged from a green house that was partially destroyed by a winter storm... One corner is broken off, but other than that it's looking almost new, it's still clear in color, along with some aluminium side pieces for it...

So, so far the net cost of it all has been nil... Perhaps I'll have to buy some little things I'm missing, but other than that, it's well withing budget at the moment... ;) I'm pondering splurging a whole of $50 on a roll of metal insect mesh, instead of my idea with layers of corrugated steel, so I'm thinking sub $100 completed...

Tweety

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Re: Solar Air heater for my shop...
« Reply #12 on: June 01, 2013, 08:35:58 AM »
If I lived in a place I couldn't touch I would move.  I know many people are proud and enjoy taking care of history but I can't stand anyone else being part of my decisions.

I don't mean that as a put down, I am glad people are different as long as they don't make decisions for my stuff.

I do agree with stevech.  I would do it with what I had and see how it went and go from there.

Good luck
gww

Well, it's my SO's ancestral home, so we never really considered not moving in here... ;) Yeah, I agree totaly that it's a giant PITA that some yahoo decided it was "culturally significant", it's not my idea at all... But on the whole, it hasn't been that much of a problem...

Most of the things I wanted to do, I have been able too... It's just taken a few extra loops in my head to do them in a way that's non-intrusive, and looks old, instead of doing things the easy way... And while at times it's very annoying, and adds a little to the cost, the end result has always turned out good, perhaps better than if I just started doing it without thinking a few steps ahead, so I don't feel to restricted by it...

Besides, with 250 sqm of house, with massive stone walls, and a second layer of LECA inside the walls and new (old looking) triple glased windows and the roof and such isolated, all heated by a geothermal heatpump with 2x800 m loops, supplemented with two woodburning stoves with water mantle's feeding the same system, I'm living cheaper than I could hope to do in a newer house, half the size, so it has benefits...

Another of those being the 55 sqm of attached shop space in the old stables, the 100 sqm of the old barn for playing with cars and bikes in, and the 10 sqkm of fields and wood for the SO's to keep her horses on once we get around to building her a stable...

End result, I'm happy where I'm at... Now as long as I can figure out a way to build a solar collector as a fence, without breaking any of the obvious rules... I'm a happy man... That is since I prefer to see what I do once the inspectors aren't looking as "bending" the rules, vs their more rigid stance...;) They haven't complained too much yet...

It's gonna be a couple of days yet, before I get to the actual build, but I'll post up results ASAP...

GaryGary

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Re: Solar Air heater for my shop...
« Reply #13 on: June 01, 2013, 10:21:36 AM »
hi,
If you do the screen absorber collector, be sure to get the airpath right.  The air typically comes in along the bottom of the collector between the screen and the glazing, it spreads out over the screen absorber and works its way through it absorbing heat from the screen, then the air exits out the back of the collector behind the screen.  You want all of the air to have to pass through the screen layers. 

The screen is tilted a bit from bottom to top -- there is more distance between the screen and the glazing at the bottom and less at the top. 

Some construction pics here: http://www.builditsolar.com/Experimental/AirColTesting/ScreenCollector/Building.htm

Some people use ventilated aluminum soffit material instead of screen, and in our testing this performed just as well as the screen.  In some places it may be easier to get the vented soffit than the screen.


Gary

gww

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Re: Solar Air heater for my shop...
« Reply #14 on: June 01, 2013, 03:32:38 PM »
Quote
It's gonna be a couple of days yet, before I get to the actual build, but I'll post up results ASAP...


Can't wait, I like pictures too.

Hope all goes well
gww

Tweety

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Re: Solar Air heater for my shop...
« Reply #15 on: June 16, 2013, 11:48:47 AM »
I have started construction...

First removing the old door and frame (or what's left of it, it was so dry rotted that I didn't even need tools, just tore it away with my hands...)



First attempt at at frame, using scrap impreganted wood form the build of the patio... The odd shape is due to the foot thick wall on one side being headsized boulders, the other mostly plaster and a few small fist sized rocks, and breaking apart as I removed the frame... I'll need to fix it up a litte once I'm done...


I wasn't happy about the bottom part, so a better attempt at making air channels...

Tweety

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Re: Solar Air heater for my shop...
« Reply #16 on: June 16, 2013, 11:54:52 AM »
Framed up the insides, filled with insulation, and added a sheet of black metal and then painted the wood black...


Not done with the top part as of yet, with the three air outlets... The metal brackets are there so I can pull the frame out to the inside/back and access where I'm putting the solar panel for power...

A better view of the airchannels, the bottom of the frame extends over a step in the stone, allowing for the middle channel to be open to the outside...

Mary B

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Re: Solar Air heater for my shop...
« Reply #17 on: June 16, 2013, 12:23:38 PM »
Why pull in outdoor air? At least that is what it looks like you are doing.

Tweety

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Re: Solar Air heater for my shop...
« Reply #18 on: June 17, 2013, 02:48:14 AM »
Why pull in outdoor air? At least that is what it looks like you are doing.

Well, the idea is to have the option of pulling outdoor air, for when the air is warmer outside and the shop is cold and damp in the middle of summer... Or when the inside is warmer, I'll just block that off and pull inside air...

I figured it was better to build it so that I have options now, than figure out later that I needed it... And since the bottom end was uneven anyways, making it impossible to just put one board across and tension the sides at the bottom, it was neccesary to make a jigsaw puzzle to put it together, putting the boards a bit higher up...

And that kind of gave me the idea to make the channels like this, using the uneven part where I couldn't use it for inside volume anyways...



Shots from the inside. Note that with no front on, the fans are spinning with every gust of wind, even though you can see that they aren't hooked up yet...

Tweety

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Re: Solar Air heater for my shop...
« Reply #19 on: June 17, 2013, 09:44:12 AM »
Anybody know somebody in Sweden that needs 90 m2 of aluminium bug screen/mesh?

I was rooting around the local building supply stores today, trying to find some bugscreen that wasn't made out of black plastic, since I didn't think that was the best option... After trying two stores, I end up in the same place where I usually end up, where they have all the odd stuff I need, and then some... I know the guys there by name since a long while...

So I ask the guy behind the counter if he have any metal mesh, not the plastic... And after a long discussion about how nobody nowadays want the aluminium screen, since it's a PITA to work with, getting stung on the ends, I tell him I still want it, since I'm not really using it for bugscreen... So he disapears inside a storage somewhere, and comes back out after a while...

"How much do you want?"
"Oh, about 5-10 m if it's wide enough..."
"Nope... Not good enough... You're buying the whole roll... I aint bothering to unroll it for you..."
"Well... uhm... How much is the whole roll then?"
"100..."
"Uh... Ok..." I take out a 100 and hold it out, he kind of pauses a while... (100 SEK, which is about $16)
"Fine..."
"So where is the roll then?"
"It's on it's way on the forklift..."
"Forklift? WTF?"

What I got dumped in the bed of my truck was a huge freaking roll of alu mesh, 1 mm holes, ½ mm string, 1m wide and 100m long on a freakishly huge wooden spindle...

I'm not sure what it's supposed to cost really, but a "normal" roll of the plastic kind is about 200 SEK for 5 m, so I'm guessing he just wanted to get rid of it... I didn't get that he was talking meters, not price...

I did end up buying two rattle cans of black, since it was natural color though... ;) Total cost $28...

And with the abundance of material, I ended up going hog wild and putting in 5 layers, before I was satisfied...

Frank S

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Re: Solar Air heater for my shop...
« Reply #20 on: June 17, 2013, 11:58:53 AM »
All I can say is you did good.
  I'd hang on to the rest of that mesh if I were you.
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Bruce S

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Re: Solar Air heater for my shop...
« Reply #21 on: June 18, 2013, 09:42:41 AM »
Nice!
That type of mesh will be good to make solar dehydrator shelves! Took me 2 weeks to find the stuff here, even then I paid that much for a roll only 1m(x)4m.
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electrondady1

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Re: Solar Air heater for my shop...
« Reply #22 on: June 18, 2013, 12:34:22 PM »
why can 't the fibreglass type screen be used ?


Frank S

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Re: Solar Air heater for my shop...
« Reply #23 on: June 18, 2013, 01:44:50 PM »
why can 't the fibreglass type screen be used ?
Thermal conductivity
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SteveCH

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Re: Solar Air heater for my shop...
« Reply #24 on: June 18, 2013, 02:24:07 PM »
Great job, looks really good. I'm eager to hear how it works out, once in operation.

Super deal on the screen. I, too, have to shop around a while to get the steel screening. My local, small-town lumber yard has it, though I can't say for how long. I'd probably be wise to buy up some for screen-door repair in the future.

gww

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Re: Solar Air heater for my shop...
« Reply #25 on: June 18, 2013, 03:26:21 PM »
Thank you for the build prosess pictures,  I too will be waiting for a progress report.
gww

john8750

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Re: Solar Air heater for my shop...
« Reply #26 on: February 26, 2014, 12:15:58 AM »
OK
Deep into winter, so how's it working?
My pop can heater works great.....

John Smith
Keep the fun in it. Give me sun light.
John Smith