Storm Window Solar Panels
(Page 3 of 4)
January/February 1984
By the Mother Earth News editors
At the lower ends of the two side rails, wing nuts slipped inside each tube served as a "catch" for the 1/4-by-3/4-inch bolts that hold the lower support legs in place. Those half-inch E.M.T. props are offset at one end so they'll crisscross, and bolt together, in the middle for added stability. (Naturally, the dimensions of this "X" brace will depend upon the size of your completed collector and your home's latitude. Just remember that the ideal winter angle for your sun grabber's surface is that latitude plus 10 degrees.)
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Congratulations! The collector itself is now complete, so it's time to move on to the insert that fits in the grooves of your home's window. This wooden "plug" supports the collector from the top and houses the blower fan, along with the air supply and return ducts. To make it, simply cut a section of 1/2-inch plywood to 12-by-20-inch and 12-by-26-inch dimensions, then fasten a 1-by-1-by-20-inch piece of 16-gauge angle iron to each edge of the longer board — flush with one end — so the other slab can slide snugly into the track you've created. Bolster the outer ends of each board with 1/2-inch spacers (the long one will take a 3/4-inch-wide strip, and the short one a hunk about 3 inches wide) tacked in place on sides opposite each other.
Next, using your two remaining dryer duct pipes as templates, trace and cut out openings in the longer piece of plywood that are 2 1/2 inches apart and at least 2 inches from the window-frame end of the board. Seal and tack the metal collars into these holes so they extend to the home's outside (away from the angle iron tracks), then bolt a shelf-and-pole bracket to each of the sliding boards. (Fasten one to the 1/2-by-3-by-12-inch spacer, and the other about 2 inches to the inside of the ducts.) A No. 6 3/4-inch roundhead wood screw threaded through the interior panel and forced into the exterior one will keep the sliding insert from slipping once it's placed within the window tracks.
The way you utilize your blower fan is a matter of preference. If it has limited delivery (under 100 cubic feet per minute), it can be mounted to the upper insert duct and connected, with dryer hose, to the fitting on the collector's air channel. This will draw air in from the middle of the room, feed it to the bottom of the collector, allow it to flow upward along the absorber face, exit it out the corner duct, and return it to the house via the dryer hose connected to the lower window vent. Alternatively, if your fan has more than enough capacity, it can be fastened over the lower window duct and used to suck air through the system, with the supply and return tubes reversed. This will slow down the flow — and further heat the air — but be forewarned that you'll sacrifice some efficiency by doing so.
Either way the fan is mounted, its thermostatic control should be wired in, as shown in our diagram, and that unit should be fed through the corner duct tube and allowed to rest on the absorber surface. Some protective housings — bent from sheet aluminum like those shown in the photo — can be used to cover the window vents if you want to avoid the expense of purchasing louvered grilles, and homemade foam-rubber plugs will keep those openings from leaking cold air in the evenings. (If you live in a particularly cold climate, you'll also want to insulate the dryer hoses by wrapping batts or foam around them and covering that with duct tape. You could also seal the joints between the insert and the window with weatherstripping, and you might even want to glue scraps of insulation board to the surface of the plywood.)
