Do It Yourself

yes, a vent stack; it helps air flow. There are three two-inch (5cm) holes at the bottom end to admit air. An earlier iteration of this design had screens over the holes to keep critters out, but it turned out to not be an issue so we have not screened the holes on this unit.

We saw a design for a solar dryer popular with Peace Corps volunteers - a heat-collector box with a small dryer compartment on top and three little trays in a stack. But I thought, why not put the dryer trays right inside the heat collector? I just checked the temperature and with partly-cloudy skies, it is 50C in the box.

It's probably related to the exif data on rotation of your phone. I guess that is stripped when uploading with other exif data for privacy reasons (to not expose GPS coordinates etc.) and then the real orientation shows up.

I built it to fit some glass that was about the right size, so not really a design others would emulate precisely. But a standard sheet of galvanized sheet metal is about three feet by six feet, so four 10-foot boards will nicely make the "box". I used 1x2 for the corner bracings (just glued and screwed), window frames, and dryer trays. I had made an earlier version with a sheet of translucent corrugated roofing for the lid, and that heated up quite well, too. The legs were just some scrap - I think the angle of the box should be around 45 to achieve some natural convection and good mid-day sun collection area. But it could vary with one's latitude I suppose - in a more northern clime (I'm at 20N), a more vertical "cabinet" might work - the dryer trays would be shallower, but convection would be better. I am not sure the vent stack makes any difference.