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I built solar thermosyphens for the knee wall of my south facing screen porch.

My goal was to use as much recycled and reclaimed material as possible.

The heat is fed into the enclosed porch. I open the house window and I have free heat in the winter.

In the summer months the sun tracks higher in the sky and the overhang of the roof prevents the sun from hitting the collectors.

Step 1: Trimming Window Panes

 I picked up a bunch of double hung windows out of a house that was getting replacement windows. The contractors are happy to give them to you. Saves them a trip to the dump.

I used a circular saw and a straight edge and trimmed them  to  all have a uniform side, I made them about 1 3/4 inch.

Step 2: Building Frames

 Once I had the window panes trimmed I now had my working dimensions.  I cut a rabbit in the frame for the window pane to sit in. I also laid in some vertical bracing and a nailer for the window to join over.

Step 3: Fastening to Wall

 I primed all the surfaces with a good exterior primer. Next using a pocket hole jig I set out a series of pocket holes for fastening frames to kneewall.

Step 4: Shoot It Up

 Set frames in place, level up and shoot screws into pocket holes. 

lay a bead of caulk on inside and outside. caulk in pocket hole pockets and prime.

Step 5: Paint Interior

 Paint the interior flat black, I laid on 2 coats.

Next is to drill holes top and bottom for air to circulate. Touch up flat black paint around holes.

Step 6: Interior Metal

 I used several items for my metal collectors. The long collector is pieces of scrap sheet metal in my garage.  One collector is made of dog food cans and my third collector has old license plates. 
paint all the metal flat black.

On the flat metal collector i have the metal suspended from cup hook attached to the top of the collector box. The dog food cans are glued to the back of the collector.

Step 7: Glazing

 Pre Prime all the window pane edges you cut with the saw. Windex inside side of window pane.

Set window panels into a bed of caulk and screw into place.

Caulk any gaps and paint with top coat color. I trimmed in spaces next to panels with vinyl siding.

I can sit on my porch in January in a tee shirt and enjoy my afternoon coffee in a balmy 70 degrees
<p>Wow, now that is ONE LARGE SCALE solar air heater! I built interior-based window units. Mine are limited by the two windows that I have. I'd love to build something much larger like yours, but I cant :( Here is my setup if u r interested in seeing it!<br>https://diybarrelstoveoutdoorfurnace.wordpress.com/2014/12/28/diy-window-mount-solar-air-heater-presentation/</p>
<p>Going into my 5th winter, just wanted to do a quick update. I have set up thermocouples and run tests and am very impressed with the amount of heat these crank out even on an overcast day. </p><p>The panel with the tin cans cranks out the most heat overall.</p>
Hi, <br>Neat idea. Couple of questions. <br><br>1) How does the heat actually get onto the porch? Are there vents above the collectors?<br><br>2) Have you considered water tanks as collectors rather than metal plates. They would hold the heat long after the sun went down wouldn't they?<br><br>Thanks for sharing.
This is the simplest of solar systems you can use.<br><br>There are vents on the inside of the porch both at the top and bottom of the collectors. I open a window or the front door and allow air and heat to naturally convect.<br><br>When ever you add water to the equation you have obstacles to overcome including added weight to structure and maintainability issues.<br><br>I have a separate domestic water heating system that I an working on for this spring, however in Ohio we can only use this during the summer months then we need to drain down and winterize, or use glycol which adds even more complications and considerations.
Passive design works the same as a heatilator on fireplaces.
Drbill,<br><br>Thanks I thought so but is wasn't quite obvious from the instructions. It's a lot like the cansolair units that are made commercially. I've seen installations that use a small solar fan to help circulate the air and that have dampers to avoid reverse convection when the temperatures get cooler at night.<br><br>I was particularly interested in the use of a different medium of exchange given the longer winter nights and shorter days, to see if there was a way to extend the working time. With the windows above the unit, this system as is supplements the daylight, I wondered if instead we could use the black units to store the daily sunlight as a heat sink and then slowly allowed them to cool via convection into the room.
Nice passive design. <br>Metal heats up. <br>Hot air rises and goes out top holes. <br>Draws in cool air behind it through bottom holes to heat up as it passes hot metal and out the top holes. <br>
Clever. Clever indeed. Well done and a good instructable. Thanks mate.

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Bio: I'm a professional craftsman, Pipe-fitter, plumber. electrician millwright and artisan I've been tinkering with machines since I was old enough to hold a ... More »
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