Constructing a Solar Kiln

As you know, we harvest and mill our own trees on our farm in Oklahoma.  And in the last five years, we have planted over 6,000 new trees to replenish this amazing resource and to look after the well-being of the earth. 

And we are pretty proud of the solar kiln we use to dry all of our lumber.  If you want a little more info about the different types of kilns, check out our blog post Types of Kilns.  We built our kiln almost entirely from material that was leftover from a construction site and was going to be taken to a landfill.  It always feels good to find a use for materials that were just going to go to waste!  The construction process took place over the course of eleven months.  It took this long because we built it during vacation time that we took from our normal jobs.  In total, there were about 21 build days involved with taking this project from start to finish.

To start out with, we needed to find the perfect location to build our kiln.  The key here is ensuring that there is enough sun exposure for your kiln.  Being that we are in the northern hemisphere, we needed to construct a kiln with the clear portion of the roof facing south.  We considered a couple of spots, but quickly it became obvious that the best option would be to build on a concrete pad that Grandpa had poured a long time ago, some 50 years or so in the past.  Also, there was some metal piping that was already a part of this concrete pad that we could implement as part of the framework for a kiln.  Originally, Grandpa had designed this space to house pigs.  This idea never came to fruition, however. Shortly after he started working on this project, the pig market changed drastically and it became very difficult to compete on price with the large pig farms. 

So for years, the concrete pad just held random junk really. But here we are years later, giving new life and purpose to this project that Grandpa started. 

First step is cleaning up all of the stuff.

Next step is sweeping!

To build the framework, we used pipe ties to attach the timber framing to the metal pipes that were already a part of the concrete pad.  This step seems simple enough, but it took several days to accomplish.

Once we had the framing done, we reused some old tin to wrap the outside of the kiln.  We had made the decision to load the kiln from the side, so we left that side open so that we could add the doors later on.

The next step was to put the roof on.  The top of our kiln has two sections with a “step” in the middle.  The step was designed to give us the space we need to add fans so that we could get good air flow throughout the kiln.  Air flow is very important when drying lumber because it ensures that the wood can dry more evenly.  One side of the kiln has a normal tin roof, while the other side has clear acrylic to allow the sun to warm up the air inside.

The next order of business was constructing some doors.  The doors are somewhat interesting because they are different heights.  This is due to the height of some of the existing pipe that we used to build the framework.

Then we added some particle board to the inside walls of the kiln to provide some insulation.  This particle board had sat inside of a barn on the farm for years – so it felt great to find a use for it.

Next, we created the wall portion of the step in the roof which all the fans would be attached to.  This part was particularly fun because we had several different sizes of fans so we had to size the openings appropriately so that we could mount the fans and they would be able to draw air from outside.  It was another great example of us reusing materials too!  A local electronic component distribution company was scrapping all these fans because they had cosmetic damage.  But they still worked just fine so we were more than happy to put them to use instead of them being thrown away!

Then of course, we positioned all the fans and mounted them to the kiln – leaving the wires accessible for future electric work.

Then there were a few minor things left to do – insulate the seams of the kiln with spray foam, add a turnbuckle to the door, install some screens where air is allowed to escape the kiln through the eaves at the back, install a miniature awning above the fans on the outside to prevent rain from getting on them, amongst a few other things.

At this point it felt like we were so close to finishing, but the actual finish line was continuing to evade us.  Of course, we carried on and built a framework on the outside of the kiln so that we could install the solar panels and then got those things installed. Personally, it was my first time using or installing solar panels on a project so that made it extra exciting! Harnessing the power of the sun is a very cool feeling - keeping it green with no unwanted byproducts or waste.

Then we wired everything up, connecting the fans to the solar panels through a small hole in the side of the kiln.

Our project was finally complete!  It was a big dream we had and building something of this magnitude was not a small undertaking for a little family working during our vacation time.  It is definitely an accomplishment that we are more than satisfied with.  To read some about how the solar kiln actually dries freshly cut lumber, check out our blog post The Art of Wood Drying: Using Our Solar Kiln.