There are some great posts in these forums about solar dehydrators. They are excellent. They are also pretty big.
I want to build a solar dehydrator but I'm on a tight budget right now, don't have much food to dry (so don't need a big one now), and don't have a ton of space to store it. Do the principles of these designs scale down? Would a smaller size significantly affect temperature and air flow? I'm thinking of building one with the drying space of a standard 5-tray electric dehydrator.
We built one of these. It cost around $300US (this included paint and we salvaged roofing from a local companies scrap pile) and took me (unskilled carpenter) and a very skilled carpenter friend of mine two casual days to build. In our climate (coastal cool and damp) it works great for drying herbs and flowers, and when we have taken it inland where it is hotter and drier it will definitely dry fruit and berries. The hardest part was finding food safe screen material that wasn't super pricey, we ended up finding some agricultural mesh (I think it was shade cloth or bird net for orchards) that was made of polyethelene, which is regarded as food safe. We modified it slightly to make the back legs removable for easier loading into the back of a pickup. Not sure if you mean smaller than that but that's what I have for ya.
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I'd suggest looking at the Walk Radiant solar drier. I think the height of the unit (front to back) is critical but you could narrow it up as much as you want. It could very likely stand up in your coat closet tucked away to the side. Here's a LINK. And here's my build.
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I built my wife a dehydrator several years ago after the huge disappointment with buying the commercial dehydrators.
I used a double glazed window and made a cheap frame/box for it to sit on, the box has several holes in it along the lower edge and
along the top edge. These holes are covered with pieces of mosquito netting to allow air flow but keep out the bugs.
Only upgrade I've thought of for the next one is a solar powered fan for better air flow.
The hight temps created kills everything. I have seen temps in the range if 150 deg.
The window was bought at a habitat for humanity store for $25 and the frame/box was a few $ in scrap wood.
Small is fine. To save $ i would start with a used window (or window pane) and build to its size. When i built mine it cost $42 (new) for 2 29" x 29" pcs of single strength glass. It shocked me a little.
Small works fine. Once upon a time I made a solar dehydrator that measured approx. 2'x2'x2'. I used a small glass window, some wood to frame the window, and a metal cabinet. I made it for a client in a couple hours and she was very happy with it.
I made a small scale solar dehydrator out of cardboard. It may not be as efficient as one made from wood and properly sealed, but it works.... I haven't tried anything more ambitious than herbs and flowers, so I don't know if it is powerful enough to dry berries and other fruit. Also, I suspect that fruit would likely stick to the cheesecloth, so I'd have to think up some new trays to use before drying fruit.
Just as a note, I found that the chimney draws better when it is pushed down a bit more than is seen in the pictures.
As you can see from the unpainted pictures, the size is about 2 1/2 feet tall with legs. You can use the tissue boxes for scale to see the size of the rest.
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