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Old 03-07-13, 04:25 PM   #1
Mikesolar
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So, I have never seen any kind of market numbers on this but I wonder how many DIY panels are made in the US each year. Just curious......

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Old 03-21-13, 10:46 AM   #2
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I don't think there would be any accurate way of finding out..
Today, I'm dreaming about building a 4'x8' hot air collector,
using Phifer Fiberglass Screen Wire.
Their product that stops 90% of solar looks like a great candidate for use
as the absorption element in a flat plate collector.

I'll bet one 4x8 collector would kick up the winter temperature
in my basement a couple degrees on sunny days..
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Old 03-21-13, 11:37 AM   #3
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Stops or absorbs?
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Old 03-21-13, 02:28 PM   #4
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Stops or absorbs?
I think it absorbs it, and quickly re-radiates it as radian heat.. IR range.?.
That's the only way I can explain it not melting or bursting into flames..

I think it would make a pretty collector element because it has a tight mesh, slowing air flow.
The low flow keeps air off the glazing..



|---------glazing-------
|------SunTex---------
|~~~air flow area~~
|________________
|___foam base_____
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Old 03-23-13, 06:35 AM   #5
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Is that an image of the 80%? The 90% that I've seen has more material and less holes. I'm thinking of making a hot air collector with that as a pass-through absorber. Allows low fan wattage as it isn't pushing through something ridiculous like a bunch of cut up aluminum cans. Granted those work but it's not going to get the most heat out and will require high static to move enough air. I'm thinking low wattage 12v bilge blower or possibly even a low sone energy star rated bathroom fan with it configured to push into the panel. I might just rip out one of my cheap ceiling shaker bathroom fans for testing this prior to spending cash on such a fan. Especially if I think I'm going to want a second 4x8 DIY air heating panel.

What would the output of a 4x8 sheet collector be at a northern latitude(top US states) would you figure? I'm hoping for close to 5000BTU/hr in the 11pm-1pm window on the clear direct sun days.


Ignore the dip between noon and 1pm, every day has that since this fall, I think a tree is growing into the solar path of the device.
According to that Jan 4th 2013 Solar Radiance detail in my area on a clear day there is about 487 watts per SquaM at noon and about 450 at 11pm and just after the 1pm 'dip'.

I could add all of the numbers up but I won't at the moment, just trying to figure peak values for now. We can average about 462 watts against a 3.5556 SquaM surface in my Minneapolish area to give 1642.7 watts to the exposure. 5604.9 BTU/hr. I'm figuring I'll probably lose about 20% from windwashing the glass and get 4483BTU/hr for the peak two hours of the day? Not shabby.

OP: You meant solar air heat, right? I meant to do this in the fall using a table saw at my brothers place but he had already tucked it into the shed so a car could fit in that space for when snow was going to fall so I was a tad too late to build the frame.
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Old 03-23-13, 06:53 AM   #6
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ok. I did some hourly averaging of the solar radiance readings and then added the cumulative total of wh radiance per SqM and it looks like 2401wh/sqm. 8536.9wh(29128BTU) of sun over a 4x8 surface minus the losses in the process and worse would be the cloudy days where this might do very little but on a good day. Basically a space heater running for nearly 5 hours(considering an hour loss due to losses in the system from conduction from the glass and wood) on sunny days with something primarily constructed out of wood. Taking a look at all of the winter days where my furnace would be running about 30 minutes less for that day and being slightly more comfortable inside, I think I might build two of these. If I had one it would have likely wiped out about 10 hours of furnace time so far this month. I think it would have been worth more than $5 of heat savings this month. The advantages would be greater in January where I dip into the furnace startup setpoint more often and could stand to gain the heat. Figuring I get half of the 'nameplate heat' versus a good day that would save about $5 in the less sunny November through February months. $20 savings per panel through the worst months, I figure. $100 after 5 years, I'm game.

Of course these are wild guesses. I do know of a couple in Minneapolis who has installed two commercial solar hot air panels in their upper level and they love them but the warm air upstairs isn't helping out the downstairs as its not moving down there on its own. May have been a better idea to have punched the holes in the house downstairs and figure that convection might help out with getting the heated air upstairs to be more even throughout the house. Either that or the solar installer might have been hoping to come back and install another one or two downstairs.

Grainger sells 90 degree on, 80 degree off snap switches to help control your fan for DIY panels.

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Old 03-23-13, 08:04 AM   #7
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That's 80% screen used in my Den cooling screens..
http://ecorenovator.org/forum/renova...n-project.html

Here's Gary's screen testing.
New Page 1

I'm not clear on the exact air-flow of the screen-collector design.
I'm still studying it. I'm in no rush, since I have no place to install the collector.

Hot air collectors on a second floor seems crazy, unless it's your primary living space, during daylight hours..

I just want to take the freakin chill out of my basement..
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Old 03-24-13, 02:56 PM   #8
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It seems to me that the screen only sees maybe 40%-50% of the sunlight available to it so I can't see how it would be as efficient as a solid flat body. It is all about (1)surface area, (2)absorption and (3)emission.
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Old 03-24-13, 03:05 PM   #9
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Quote:
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It seems to me that the screen only sees maybe 40%-50% of the sunlight available to it so I can't see how it would be as efficient as a solid flat body. It is all about (1)surface area, (2)absorption and (3)emission.
You use three layers. When Gary built it, I think three layers of fiberglass screen has the screen taking 79% of the sunlight. The rest hits the back of the collector and isn't lost if the back of the collector is rigid foam.

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