How to build a Solar Drying Room?
We are on a permaculture property just outside of Byron Bay in Australia. We have converted and sealed off the upstairs of a barn to be used as a solar drying room.
At the moment, we have whirly birds in the roof, but even on days of 20C, things such as tomatoes and bananas go mouldy when laid out on mesh trays with no direct sunlight.
If I can figure out how to attach a photo I will, essentially the room is 50m2, or about 12m x 4m, with a tin roof.
Typically I think you want to blow hot air from a solar thermal panel of some kind over the food, but that’s not what we have because the room is so big compared to a normal solar dryer.
From what I have read, these are my proposed improvements:
1. Paint the roof black – Tin reflects heat better than most roofing materials. Painting black will abosrb on the outside, and then the unpainted side ont he inside should radiate it out.
2. Insulate. Ensure the walls and floors are well insulated (possibly with foam?). We have a window at one end in a wooden wall, a door at the other in a wooden wall, and wooden flooring. How about insulation under the floor, and behind the walls. Perhaps tin foil on the walls?
3. Get some 1.5kW fans in and line them up with the trays. Then the whirly birds should do the rest. 1.5kW fan is what I saw someone else had used.
Any thoughts?
I’m considering installing Perspex sheets into the roof on the north facing side, but I also read it’s best not to have direct sunlight on the food.
Please provide specifications with suggestions where possible. I need to know what size fans to use as far as power goes.
How about using thermsiphoning to create the air movement instead of fans. As you know, hot air rises. So get some long flexible 4" diameter aluminium tube and drill a 4" hole in your roof. Have one end of the tube sticking up through the hole about 1m. Paint that end black so that the air in it will be heated. Have the other end of the tube hanging just above your food. The heated air in the black end of the tube extending about the roof will rise out of the tube pulling fresh air in from the end above the food, creating the desired air flow.
Note: The above is just an idea off the top of my head. I’m sure it’s been done many times though. You will likely have to experiment a bit. Maybe looking up "solar chimney" will help.
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If at all possible add some heat lamps. These should aid in adding enough heat to dry.
Adding the fans to keep the air moving will help as will the lighting. These two things will make it more difficult for the mold to grow.
References :
How about using thermsiphoning to create the air movement instead of fans. As you know, hot air rises. So get some long flexible 4" diameter aluminium tube and drill a 4" hole in your roof. Have one end of the tube sticking up through the hole about 1m. Paint that end black so that the air in it will be heated. Have the other end of the tube hanging just above your food. The heated air in the black end of the tube extending about the roof will rise out of the tube pulling fresh air in from the end above the food, creating the desired air flow.
Note: The above is just an idea off the top of my head. I’m sure it’s been done many times though. You will likely have to experiment a bit. Maybe looking up "solar chimney" will help.
References :
Try something to dehumidify the air such as shallow pans of silica gel or salt, even a concentrated brine fountain or blowing the air through a fabric that’s wicking a concentrated brine would reduce the humidity.
You could put out UV lights to keep the foods sterile while drying.
Keep in mind that humid air is lighter than dry air.
References :