Very Cool! I actually built one of these (in the smaller variety) with my daughter last year to heat the chicken coop in the winter. Here is what we built (sorry no picks, you'll understand in a minute):
Materials:
Old storm window (36" x 24" approximately)
Flexible dryer vent kit
36" x 24" (approximate) sheet of 1/2" thick pressure treated plywood
(2) 6" x 3/4" thick pressure treated pine boards x 6' lg.
Can of high heat (grill) paint, black
Tube of caulk
Tube of construction adhesive
Start by building a box that fits the exact outside dimensions of the window, utilizing the plywood as the back of the box, then making the sides (depth) of the box from the 6" pine boards. Drill a hole in the top pine board (4" diameter) all the way to one end, just big enough for the dryer vent kit's aluminum duct flange to fit through, then do the same on the opposite end bottom side pine board. Slide the vent kit's aluminum duct flanges through these two holes, sticking out about half way (about 3") through the hole. Caulk them in place and let dry. Then take the flexible foil tubing that came with the vent kit and attach one end of the tubing to one of the duct flanges with the supplied hose clamp on the inside of the box. Start making "S" curves with the flexible foil tube until you can fit almost all of the tubing into the box, attaching the other end of the tubing to the remaining flange with the supplied hose clamp. You may want to shoot a bit of caulk or construction adhesive to the bottom of the flexible foil tubing in a few spots to attach it to the plywood backing and let that dry. Once everything is fit up and dry, paint the whole inside of the box with the high heat paint. Lastly, once everything is secured and well painted on the inside of the box, attach the window to the face of the box with construction adhesive, and let dry.
You have yourself a solar heater. This is a convection current heater, that will heat a small room (like a chicken coop). I tested our little unit on a 30 degree morning with sun, and within about 10 minutes the output side (top) was registering 120 degree air.
Unfortunately, before we could mount our heater, it got knocked over onto the floor and broke the glass. It sat around for about a year after that, and have since thrown it away, but my daughter and I will most likely build another one once we find a nice donor window in the garbage.