Building My Solar Dry Kiln
Written by on January 14, 2017
INTRODUCTION
Being able to kiln dry your OWN lumber is a major benefit to a woodworker. This is especially true since many custom projects require species not available at box stores. Also, owning a kiln allows the furniture builder to use locally sourced lumber from logs which many times, are left to rot where they fall. Owning your own kiln is a necessity if you are fortunate enough to own your own sawmill. The potential projects can then become limitless with this powerful combination.
I only became aware of portable bandsaw mills about 10 years ago after moving into the country while visiting a friend of mine named Jimmy. His son had bought him one and had it shipped in a large crate to him. Assembly was definitely required! It took him over a month to get the thing set up. After I saw the thing in action, I knew I had to have one. If only I had one 30 years ago, I would have built many times the projects I’ve done!
Using rough sawn lumber that has not been kiln dried for indoor use is a BIG no no. It is necessary to have your lumber stock in the 6%-8% range of moisture content for the lumber to remain stable, and not move too much which can destroy a joint. Also, the bug larvae present in air dried stock cannot be tolerated. It is necessary to heat the wood in order to achieve a temperature over 135 degrees Fahrenheit to kill the larvae. Moisture meters are available on the internet, and all woodworkers should have one to check their project lumber. This design heats up well over that temperature, and will pull out the moisture present in new rough sawn stock which can run up to 50%! The dry kiln will be a life saver to any serious woodworker who takes the time to build one.
About 7 years ago after finding a used Norwood Lumbermate 2000 in Mississippi a fellow had bought to saw logs knocked over from Katrina, Jimmy and I went down with a long trailer and brought it to my home in Louisiana. It soon became apparent that I needed a dry kiln in order to use the lumber for furniture. I had a buddy who lives near me named Wayne who has helped me along the way when things go south. He is a great friend, and someone I’ve grown to admire and turn to for all types of advice and help. He worked at the height of the NASA space program on computers in Huntsville, Alabama, and helped take us to the moon. His ability to figure out things mechanical is a trait that I hope to have rub off on me! I fall a bit short, but I’m STILL paying attention.
Anyway, he and a friend of his named Leroy, have figured out a solar dry kiln design that rivals many today. The system is basically a collector panel plenum which heats up with the sun’s rays. The air is circulated through the lumber stacks by a couple of simple fans. Additionally, a dehumidifier is added inside to collect the moisture drawn from the wood. There is no other heat source but the sun, and temperatures can reach in excess of 180 degrees Fahrenheit. It works extremely well here in the south. I built it about 5′ wide and a little over 17′ long in order to be able to fit 16′ boards into it. I also added a trailer hitch attachment in order to move it, although it has sat in place the entire time! I hope to move it to a different location soon though.
There are five access doors across the front. The two end doors are hinged, and the three center sections are removable. I just lean them onto the opened end doors as I’m loading and unloading lumber. Here’s a picture of the front of my kiln. You can see the extension cord plugged into a connecting receptacle on the end:
And a picture of the rear:
And here’s a picture of it with a load of walnut I recently dried for my brother’s new home. You can see the dehumidifier on top of the stack, as well as the two fans that blow down from above:
Here’s an overview video I made a while back:
The main idea here is that the sun heats the metal that has been painted black inside the plenum area between the rafters. If you’ve ever grabbed a black handrail that has been exposed to the sun, you know how hot it gets. That’s why the metal is painted black and facing up to the sun. The upper plastic roof panels trap the heat which then rises to the top attic, and is recirculated down into the lumber stacks by the fans.
I’ve used it for about five years now, and have never had any problems with it. The only thing that happened once was a major hail storm that went through. I had to replace the top plastic panels after that. I believe it cost me around $150.00 for the materials. Since all the boards cost me nothing but some time on my sawmill, as I recall, the materials I had to buy were around $450.00. That’s it! So, let me show you how I built my baby.