A Small Solar Kiln

Report and photos of a small, just-finished solar kiln. November 8, 2007

First, want to say thanks to the contributors on this board that helped with all the information to build a solar kiln. Using two solar powered fans for circulation, you can see the collectors mounted inside to help keep them from getting damaged. Kiln is 4'x8' and the entire bottom half of the back is covered by two doors that open so I can load wood on a pallet with a Bobcat. Pallet size is 6'6"x30" and circulation seems good so far. First charge is red oak, 13% MC when it went in 3 weeks ago, about 9% now. Temperatures have been as high as 125 degrees, but we're now starting to get some warmer weather, so hoping for a few days above 130 degrees to make sure any bugs are dead. As you can see, the kiln is built on skids, so it can be moved with the Bobcat and loaded on a trailer. Only for hobby use, but wanted it self contained so that's why I went with the solar fans - they were about $180 each including the panels. Collector is two layers of clear, fiberglass panels. Total cost was about $900 here in N. VA. Thanks again to all who post and provide this great resource.

Click here for higher quality, full size image

Forum Responses
(Sawing and Drying Forum)
From contributor T:
Nice job. Thanks for posting the picture so we can see it. What are you going to load it with next?

From the original questioner:
I have enough red and white oak cut for at least 2 and maybe 3 more charges (about 300 bf per charge?). I've recently cut some cherry and locust that I'll air dry a few months, so probably have all I can use for this summer. Guess I'll leave a charge in through the winter as well. It might not dry a lot, but it will be out of the elements...?

Good news is I'll have more than I have time to use this winter when I do most of my woodworking - shop is heated, but not cooled. I also plan to move the fan solar panels more to the center for the next charge, as this should give them a bit longer run time as they are partially shaded by the sides.

From contributor J:

Nice job on the kiln. I'd love to know your source for the solar fans. Let us know how the oak turns out when it's finished drying.

From the original questioner:
The fans I used are from Home Depot. They are attic gable fans. I think they were about a 12" fan.

From contributor Y:
Nice job. It appears from the image that that the photovoltaics (PVs) are mounted inside the kiln. If that is true, then you will experience significantly decreased output. They like to be cool. You will get a much better output if you can mount them outside. Another source of DC fans is radiator fans from salvage yards.

From the original questioner:
Thanks for the information. I was going to move the panels anyway, so went ahead this morning and moved them outside the kiln. Cloudy here today, so may not see much difference, but thanks again for the feedback.

From Professor Gene Wengert, forum technical advisor:
Looks great. If you use some of the incoming solar energy to make electricity, then it will not be available for heat, and your kiln will be slower and less effective. So having the electric panels outside and separate from the roof collector is desirable.

From the original questioner:
Wanted to pass along an update. About two weeks ago, did some measurements and had an average of 8.9% MC for 10 readings. Yesterday, checked again and at 7.5% for 10 readings so all in all, looks like it's working well. Will probably pull this load out next weekend if the MC doesn't appear to be getting any lower. Have another load ready to go, so no downtime for a while!