Solar Air Screen Collector Design - Heating My 12x12 Shed

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  • unt0uchable
    Member
    • Oct 2013
    • 35

    Solar Air Screen Collector Design - Heating My 12x12 Shed

    Well, since posting in the off grid section for my shed, I've learned some very useful information so I thought I would post my first plans for my Solar Air Screen Collector that I plan to set outside the window of my shed to see if I can pipe some hot air into this place.

    First thing is first, the shed is not insulated. It's double sheeted on the exterior of the walls, and there is a single sheet of 1/2"OSB on the inside to finish it off. There is an 8' ridge vent, and 2x 3x12 vents to allow airflow from near the soffit area. I'm not insulating it. This is just going to be a fun DIY project and something that I can use when I'm working out there.

    I plan to build it out of 2x6 (hopefully metal studs if the local HD has them). It will be 4'x4' and it's a little different from most of the others I've seen out there. Here are the plans I've drawn up rather quickly on the computer.

    Cool air will be drawn into the lower duct and fall down the backside of the collector. That side will be insulated with 1/2" foam board and sealed off with a 1/2" piece of OSB. This will be a free flowing area, though I have thought about making channels to disperse the air evenly, I have not shown this in the drawing.

    The lower portion of the collector will be open where the air begins to pass through the screen. I've designed it so the screen zig zags back and forth up the heating side of the collector. This is to cause turbulence and allow for some scrubbing effect on the air. It should also slow it down and allow it to be heated evenly as it passes through the hot screen 13 different times.

    This next part is even more different than everyone else's designs. Please give me your comments and concerns with the design.

    For mine, I will not have the clear acrylic cover exposing everything inside to the sun like everyone else. Instead, I will be placing black solar pool heating blanket material (which is basically heavy duty bubble wrap) on the inside of my clear plastic glazing. This will soak in the heat from the sun and heat the space behind it just as it works on the pool water, only this time with air. The cooling and heating sides of the collector will be separated by a 1" piece of foam insulation. The heating side will also be lined with single sided foil reflective bubble insulation to help reflect what heat is coming from the solar pool blanket back into the space, effectively reflecting heat onto the air passing through and heating it more so.

    The duct work at the top of the collector is built this way because the window in my shed is a vertical slider. The ducts will be 12" wide x 2 1/4" tall and they reduce into a 6" vent. I plan to take a 1/2" piece of OSB, cut it to about 8" wide and however tall my window is, and then attach some foam insulation to the other side. I'll probably paint the outside of it black so it doesn't stand out too much. I will likely leave this as a passive heater until I can find a deal on some 6" solar fans that I can attach to the duct work. I could also run the fans off my solar electricity since they would only be running during the day, I wouldn't be discharging much. I'll have to

    Here are the plans I've come up with thus far. I'll probably start on it in the next couple of weeks. As soon as I get my garage cleaned out and the shed organized enough to get side tracked again....

    Let me know what you all think of the design. I'm not going to be getting super technical with testing it. I'll use an IR laser thermometer that we use here at work to measure curing temps for printing garments. I'll also put a thermometer up inside the shed to read the change in temp, etc.

    I'll explain the colors:
    Pink: Ridgid Foam Insulation - varies thicknesses
    Black: Solar Heating Pool Blanket Masterial
    Grey: Foil Reflective Bubble Wrap Insulation
    White: Clear Plexiglas Glazing
    Brown: Wood Materials
  • Naptown
    Solar Fanatic
    • Feb 2011
    • 6880

    #2
    Lose the pool cover material and paint the screening black
    Use foil face polyisocyanurate foam ( Home Depot has it ) foil face up
    I would use a polycarbonate glazing that looks like cardboard but clear ( can't remember the name at the moment)
    Make the panel steeper more like latitude + 15-20 degrees for more convective action
    NABCEP certified Technical Sales Professional

    [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

    [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

    [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

    Comment

    • unt0uchable
      Member
      • Oct 2013
      • 35

      #3
      You don't think the pool cover material will make it act like an oven behind it? I remember making a solar over in like 4th grade that was essentially a black box with foil inside. No area for sun to enter and we could like a quesadilla or something in it. Wouldn't it work to that effect?

      The screen that HD sells is already black.

      Foil face foam noted. This eliminates the need for the foil faced bubble wrap insulation, correct?

      Steeper angle noted.

      For glazing, are you talking about the stuff that covers interior fluorescent lighting? It's sort of got that corrugated look to it...and it's cheap at $9 for a 24x48 piece...

      Comment

      • Naptown
        Solar Fanatic
        • Feb 2011
        • 6880

        #4
        The pool cover will act as an insulator and raise the temperature of the glazing.

        The glazing is called kal wall I believe and looks very similar to what you described. It is also a bit better insulated this will hold up longer than the light diffusers
        NABCEP certified Technical Sales Professional

        [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

        [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

        [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

        Comment

        • unt0uchable
          Member
          • Oct 2013
          • 35

          #5
          Thanks, I'll look into that.

          What about using the solar pool material as the back drop instead? If the screen is black, there is no reason to paint the silver foil on the foam insulation right? That would defeat it's reflective properties...?

          I was trying to create an oven affect inside the heating side of the collector. Would this not be as effective as just leaving it exposed to the sun? I may do a test run of it with the solar pool material and without to see.

          Thanks for the tips!!

          Comment

          • russ
            Solar Fanatic
            • Jul 2009
            • 10360

            #6
            Originally posted by unt0uchable
            For glazing, are you talking about the stuff that covers interior fluorescent lighting? It's sort of got that corrugated look to it...and it's cheap at $9 for a 24x48 piece...
            Make sure what you pick up is treated for UV resist characteristics.
            [SIGPIC][/SIGPIC]

            Comment

            • unt0uchable
              Member
              • Oct 2013
              • 35

              #7
              I'll make sure whatever I get has the UV properties.

              I found a few windows on CL that might also work. They are old school wood frame windows form the 40-40's. Single pane glass. Will this be alright for this project? The only thing is, the one is like 7'x5' and has 12" square panes all over that make up the window. Would the framing around the panes interfere with the efficiency of the unit?

              Also, looked up that Kalwall stuff. Apparently, after seeing some different people post about it, it runs about $40/sq ft. Too rich for my blood. I'll have to see if HD has something similar to it...

              Comment

              • russ
                Solar Fanatic
                • Jul 2009
                • 10360

                #8
                The small panes just reduce the amount of light hitting the heat transfer surface.
                [SIGPIC][/SIGPIC]

                Comment

                • unt0uchable
                  Member
                  • Oct 2013
                  • 35

                  #9
                  Well good news! I found that my local Lowes actually carries the roofing panels and I'll only need one to complete the 4x4 unit. Shown here, this is what I've seen some others using. Should work fine. Doesn't look as clean as clear acrylic but lexan, plexi, it all costs too damn much to make this project worth while. This sheeting is $22 and once it's cut in half, will cover my whole unit. Just going to have to buy the foam mounting cushions to keep it well insulation. That's another $10 so, for around $35, I'll be happy. Unless someone knows of a smoking deal on some (thick enough) polycarbonate sheeting...

                  Comment

                  • russ
                    Solar Fanatic
                    • Jul 2009
                    • 10360

                    #10
                    You got it - Polycarbonate is not cheap! Typically they should give some guaranteed lifetime - all will yellow after a number of years.
                    [SIGPIC][/SIGPIC]

                    Comment

                    • unt0uchable
                      Member
                      • Oct 2013
                      • 35

                      #11
                      I will have to check when I go to Lowes if they have a lifetime guarantee. That'd be nice. Every few years, get a new cover for it. Maybe by that time, I'll be rich like all these polycarbonate sales guys

                      Comment

                      • ChrisJ
                        Junior Member
                        • Feb 2011
                        • 23

                        #12
                        Originally posted by Naptown
                        The glazing is called kal wall I believe and looks very similar to what you described. It is also a bit better insulated this will hold up longer than the light diffusers
                        I think it's called twin wall polycarbonate, some greenhouse kits come with it.

                        Big box stores don't carry it, unless you live in a part of the US that has a Menards store, they carry it.

                        Chris

                        Comment

                        • unt0uchable
                          Member
                          • Oct 2013
                          • 35

                          #13
                          Holy crap I totally forgot about the Menards up the road! I'll have to start searching there website. I do have a bundle of shingles I need to return there...

                          Comment

                          • unt0uchable
                            Member
                            • Oct 2013
                            • 35

                            #14
                            So, is it eminent that I use the aluminum screen inside of one of these? My reason for asking is because I had to purchase a 25' roll of the cheaper fiberglass stuff to use on some soffit vents we are putting in before I insulate the attic more.

                            Would that be acceptable to use in the solar air heater? It is black already, but I wasn't sure how well it would work as opposed to the aluminum screen.

                            Thanks for any other tips.

                            Comment

                            • russ
                              Solar Fanatic
                              • Jul 2009
                              • 10360

                              #15
                              Originally posted by unt0uchable
                              So, is it eminent that I use the aluminum screen inside of one of these? My reason for asking is because I had to purchase a 25' roll of the cheaper fiberglass stuff to use on some soffit vents we are putting in before I insulate the attic more.

                              Would that be acceptable to use in the solar air heater? It is black already, but I wasn't sure how well it would work as opposed to the aluminum screen.

                              Thanks for any other tips.
                              For heat transfer the fibreglass stuff is useless.
                              [SIGPIC][/SIGPIC]

                              Comment

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