Solar Lumber Drier - Part 5

[jteneyck]

The drier is done and ready to load with lumber and give it a go.  



The solar panels are mounted on the lower corners of the front of the drier, at least for now.  Here's a picture of the back showing the vents with their sliding doors.  Hinged doors might keep the weather out better so what you see might change.  



After I insulated the inside with fiberglass, I installed a plastic vapor barrier, then put up 1/2" plywood sheathing.  I painted it with two coats of black paint, mostly because that's what ever article says you should do.  The heat transfer engineer in me says there's not enough mass in that plywood to store much heat but I needed to paint it with something so black it is.  

Inside the kiln there are two 12V radiator fans, wired directly to the solar panels.  They are installed in a panel hanging from the ridge beam, directly in line with the upper air vents.  
When the sun shines the fans run; when it doesn't they don't.  Each fan has a flow of over 1500 cfm when running at full speed (bright sunshine).  The fans will blow air down the sloped front wall, then it will flow throught the lumber stack and to the back of the kiln.  There will be a curtain hanging from the fan panel to seal off the wood stack, forcing the air to go through the stack.  




 
Time to load the drier with some AD wood and give it go.  I'm starting with AD wood because it will be nearly impossible to damage it and I'll gain some insight on how to control the kiln.  

John

[jteneyck]

A friend came by this afternoon and we loaded two racks of AD ash into the kiln, something around 900 bf I'm guessing.  Here's a photo of the load with the black plastic curtain hanging from the fan shroud to the top of the stack.  

The plastic creates enough of a seal to force air down the glazing to the front of the stack, then through the stack to recirculate back to the fans.  I found an Accurite temp/humidity unit at my local Lowes that has a 300 ft range for the remote.  I wasn't sure if it actually would work, but so far it is; the drier is about 200 ft from my house.  The unit has a max/min feature as well which should be helpful in tracking the peaks and valleys of temp. and RH from day to day.  
The wood was milled last Fall and had a starting MC of 14% with my pin meter.  It shouldn't take long to dry if the weather stays like it has been with lots of sunny days.  Anyone care to hazard a guess?  I'm thinking 14 days to get down to 7%.  
John

[efmrrt]

John,

Looks good. What's the foot print of the building? Do you have enough glass view for the size? What plans did you use?

I do like the addition of the solar panels. Just curious as I'm building mine now.

[jteneyck]

John,

Looks good.  What's the foot print of the building? Do you have enough glass view for the size? What plans did you use?

I do like the addition of the solar panels. Just curious as I'm building mine now.

The building is 12' x 8' with 96 ft^2 of glazing at 45° on the S. side.  The kiln will hold about 1000 BF of lumber so it's in good proportion with the glazing at 10 BF / 1 ft^2.  I used the basic design from an old issue of Wood Magazine.  You can find it online w/ no problems.  I modified the design slightly to use 6'8" doors by changing the N. roof to 30° instead of 45°, and I also extended it about a foot to provide weather protection of for the vents.  

If you have grid power available for your kiln I would go that route.  I used solar panels only because I have no grid power where the kiln is and it was cheaper to go the solar route than dig a trench and run power out there.  

John

[Stwood_]

Common practice in the industry is to put your end sticker under the very end of the board.
Helps with end checking.....

[jteneyck]

Common practice in the industry is to put your end sticker under the very end of the board.
Helps with end checking.....

You are right and I try to do that when stacking green lumber.  But I haven't found it to matter with AD lumber, which is what I loaded into the kiln.   

John

[Stwood_]

Missouri-Pacific lumber, not to far from here, specializes in walnut.
They air dry for 6 months, then kiln dry. All stickers are at the end of the boards both times.
But.,,,unlike you and me, they have a auto sticker and stacker machine.

[ianab]

Looking good, and yes, if wood is "air dry" then the stickers at the end isn't really a thing,  It can help with green wood as it slows the drying from the end grain a little. But it wood has air dried down under 20%, it's hard to mess up, and the solar dryer will pull it down to ~8% easily enough.