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Step 5Install Metal Window Screen
Cut and staple black metal window screen (two layers) to the wood inserts in the box.
Note, this needs to be metal window screen for good heat exchanging; fiberglass screen won't work well.
I used 48" wide screen and had to trim the edge some with a utility knife.
Note, this needs to be metal window screen for good heat exchanging; fiberglass screen won't work well.
I used 48" wide screen and had to trim the edge some with a utility knife.
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To double the output, you would need to double the area of sunlight you are collecting from, not the area of the collector surface.
You can however collect more energy by angling the collector to point towards the sun so that the collector is making best use of its area, but the angle and gains would depend on your latitude and I suspect not be worth that much in terms of construction problems compared to just making it slightly bigger.
I would love to hear of other experiments with 1" or 2" air filters that have been painted with flat black paint, especially fiberglass, open-cell sponge and cheap pleated filters.
Although it is expensive, 1/4" thick white Melamine foam (like in Mr Clean Magic Sponge and thicker sound dampers) has outstanding properties and might be close to 98% efficient in absorbing solar energy, once it is painted.
I suspect that the material does not have to be a good thermal conductor, if it is in intimate contact with the air stream. The earliest american patents on solar air heaters refer to prior art using wool!
1) Air flow through the panel is much better than laminar air flow along the panel.
2) A louver-shaped punched will admit very little light through the panel to the wall surface.
3) A Micro-punched array will minimize laminar flow and reduce the surface temperature of the sheet. Foil, or very thin sheet metal, is easy to micro-punch.
4) Using stainless steel, which has a high nickel content, means that the surface can be heated until it oxidizes the nickel content, creating a dark blue metal surface. Many studies show that this is an excellent selective solar absorber. This should increase the performance of the absorber by a factor of 2 or 3 over any available paint.
Say you have south facing windows - what's stopping us from using the screen for each window, pitching it correctly and having it placed so air can pass between it and the window easily (since most screen blocks 70% of air flow)?
Wouldn't this work in the same manner - just inside the structure, rather than outside the structure?
I will be trying this as I have many windows appropriately placed in the house and 1 large 1 in the work space I am hoping to heat.
Any suggestions on measuring efficacy since it will be in a heated space but a cloudy location of the US?
http://www.perforatedmetalscreen.com/perforatedmetalimages/perforatedmetallouvers.jpg
http://www.okayi.com.sg/sunscreen.html
I'm planning on making one for an unheated work space to extend my work time by a couple of months.
I'll try whatever.
It seems like a lot of labor to make thousands of cuts through corrugated at an angle, but if a power-tool was used on, say, eight or sixteen layers at a time... (Eight layers can be cut in three steps, sixteen in four steps.)
If this is economical, a cat scratcher company could make them.
As for other materials - someone mentioned quilt batting. Yes - it's white, but as mentioned, it can be painted. You can get black batting, but it's pricer.
If you wanted to try something like that, I'd go with Fleece. It's very cheap now, is in all fabric stores and you can buy it in black. 4.99 per 36x60" piece. And if you work it right, you can get it on sale for less. It started out as recycled soda bottles, so doubt there's much outgassing. But I don't know how well it will hold up to sun exposure over time.
There's also a product called Shade Cloth that's used in nurseries. You can get it in a variety of shade blocking thickeness. What little I've seen is made out of the same material as fleece - polypro. To me - this is a great one to try. Very airy so plants don't stifle, but already dark - no painting, and in a variety of densities for varying climates or heat needs.
All I'll say is don't buy this from FarmTek. They are very expensive and you can get this stuff very cheap.
All materials do a great job at blocking radiant heat - just look at a stove/fireplace screen. The difference in the amount radiated out is incredible.
Am hoping to get to mine within the next few weeks. It all depends on several other projects I've got going - like making apple sauce.
Screen of any type blocks radiant heat - as noted with a screen in front of a fireplace or open wood stove - thus, capturing and holding some of the sun's energy that has passed through the screen, rather than just reflected back out with minimal capture by the backside of the screen.
Has it been tested? Just curious is all. Not trying to say it's a superior idea.
The idea behind using screen is that All the air comes in very close contact with the hot screen to get to the air exit. This cools the screen and minimizes infrared emittance. Of course, to get All the air to pass through the screen, you must stretch it diagonally across the box! In this design, the screen would be attached to the back wall above the bottom vents and to the front of the box near the top.
The heat storage should be located indoors within the building's insulation envelope, not in the collectors. This makes the collector responsive to morning light and prevents heat loss at night.
Once the air is at a comfortable level, the excess heat can be diverted to the heat sink. such as cement board, indoor brick walls, water tanks, concrete floor or even the soil under the concrete floor. (Soil is dirt-cheap)
Thanks for your comments
You are correct about adding more screen. If I'm right you got this idea from the man that built one on his shop "Gary Reysa" Mother did the article on him. He has a fantastic website www.builditsolar.com That is if you don't know that already.