The Solar Kiln

Leveraging the power of the sun

What is it?

When we really built momentum in woodworking, we needed more material.  So we went to social media to find people who had trees cut down and were giving away "free firewood".  Multiple pickup truck loads stacked neatly in the driveway and milled into boards with chainsaws and bandsaws.  The next challenge was to dry it. Introduce the Solar Kiln

What did we learn?

The first thing we learned is that it takes ~1 year per inch of thickness to dry many species of wood.  We then learned about Equilibrium Moisture Content (EMC).  That is the relative amount of moisture in the wood, represented by a percentage of its weight.  Your target EMC for wood depends on the part of the world in which you live. If EMC is 7%-9% for your area, you will want to dry your wood until it reaches that.

Okay, that's easy, right?  Well, fresh cut wood could have 30% to 60% moisture content.  Depending on the time of year, relative humidity, and other factors, it could take a LONG time to air dry that wood.  So many millers and lumber yards have kilns.  These are machines that cycle heat and air around the wood to remove the moisture faster.  Not too fast, because that could cause checking and cracking in the wood.

But these machines can be expensive.  So a budding woodworker was not ready for that kind of investment.  So after much research, we learned about building a solar kiln.  This is essentially a box that uses sunlight, and the heat it generates, to dry the wood.  To move the air within the box, we added solar panels and about 8 small fans to move the air.

The result?  We could dry a full load of about 300 board feet of wood in about 2 to 6 weeks (depending on the season).  Plus, the natural heating and cooling cycles from the day gave the moisture time to escape and the wood to adapt with minimal to no warping, twisting, checking and cracking

In Closing…

It was such a great learning experience.  Although we've had to temporarily cease wood milling and drying operations ourselves (HOA), the kiln was a phenominal device while we had it. We dried stacks and stacks of Ash, Black Walnut, Cherry, Black Locust, Hackberry, White Oak, and other species in it with great success.  The kiln was traded to a budding woodworker for some really good Ash.  We are glad to see it continue operations, and thankful to the Lord for the learning experience!