Miniature Solar Kilns

Very small solar kilns are indeed practicable, if you only need to dry small pieces of wood. December 31, 2012

Question
I'm a guitar builder, and very new to cutting up my own wood. I've been tossing around the idea of a very small kiln for some time now, and have yet to come across anything smaller than a storage shed.

It seems to me the principle should work on a smaller scale as well. For the guitars I build, I almost never need anything longer than three feet. I'm often frustrated when I have to buy 6bf of lumber for the 1-2bf I actually need.

I'd like to build a solar kiln that can be obscured by a privacy fence and potentially be transported at some future point. I'm thinking something around 4' tall, 8' long, and 4' deep, with dimensions adjusted for my latitude, which is 33 degrees north. Anybody ever heard of something like that? If not, can you imagine any reason it wouldn't work?

Forum Responses
(Sawing and Drying Forum)
From contributor S:
I have built large ones, but the smallest one I built used the glass out of an old storm door. It worked very well, and was no more than about 3'x6'x2' tall.

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From Professor Gene Wengert, forum technical advisor:
I built my first solar kiln in 1961. It was about 2' x 3' x 2' high. I built three and was testing one, two or three layers if clear plastic for a cover. You can make the kiln as small as you want, but keep the ratio of 10 bf to 1 sq ft of roof area. Of course, slope the roof, insulate walls and floor, and follow all the other design features.

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From the original questioner:
That's just what I needed to hear. Thanks.

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From contributor M:
I know you said you are going solar, but you reminded me of a school project I did with my youngest son for a science fair. We built a small kiln, 16" wide, 24" long and about 18" high. Just a frame with a 6 mil plastic covering and we heated the thing with a 150 watt light bulb and used a small desk fan (4") to circulate the air. It worked amazingly well. He did quite well, made up to the state finals.

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From the original questioner:
I actually thought about building something just like that. I'd be very interested to know what you used in terms of electronic components (fan/thermostat/whatever). When I was thinking of doing a light bulb kiln, I was actually thinking of it for interior use.

However, going solar has a few advantages for me, and the biggest of those is that I might be able to get away without running electricity to it at all, and just utilize small solar panels, since the fan won't be too big. I haven't looked too far into this yet, but it seems like it could work.

I'm thinking I can get away with doing this in a residential backyard (no HOA). I may even mount the sucker on wheels at some point if there's any need to emphasize that it's portable personal property. Also, at the size I'm considering, I think I can utilize shipping pallets for the frame and have minimal loss on plywood. I may even work up a modular design, since it doesn't have to be airtight.

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From Professor Gene Wengert, forum technical advisor:
Back in 1961 we had a solar kiln outside of Madison, WI that had fans that were driven or powered by a windmill. Today, I have seen several kilns using solar panels, but the high air flow needed for green lumber drying is hard to develop with solar panels unless many are used, which is expensive initially.

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From contributor M:
We went very basic, just the fan, light bulb and a thermometer. Since the unit was so small and had to be portable for my son to carry it to school and the other events, we had it either in the carport or sometimes in our house. Having it so close allowed us to watch the temp and make some adjustments. Remember, our goal was not to get the best quality of dried wood, but more to accumulate data and in general show the process of how wood is dried. As a comparison, we also dried wood in our oven at slightly higher temperatures, and showed comparable results in terms of checking and the amount of time required to drop the moisture content. We used mostly 4/4 wood in lengths of 18" to 22". While we got the wood to dry better than I would have initially guessed, it seems like a small kiln should certainly be doable for getting good results like you would need. A simple thermostat would have been a big help to control the temp in ours, but again we weren't that concerned with the actual temp.

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From the original questioner:
Okay, that helps. Sounds like I'm going to have to run power out there after all. Wind isn't going to be an option if I'm going to keep it out of the neighbors' view.

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From Professor Gene Wengert, forum technical advisor:
From a tax perspective, a kiln is a piece of depreciable equipment. A building code perspective says it is a structure.