Solar kiln build

Fil-Dill · January 10, 2011, 08:33:11 PM

I would like to build a solar kiln and wood like it to hold 12-16' lumber. The problem is I won't always have the board footage to stay with the 1:10 ratio for board footage and collector area. Do I just cover part of the roof or should I make the first and last sheet of roofing tin instead of polycarbonate.

Larry · January 11, 2011, 03:39:59 PM

There is no really good answer for your question as every solar kiln I have seen is constructed differently. Different glazing, roof angle, insulation, and vents.

In general the first thing you need to do is monitor how fast your kiln is drying. If your exceeding the safe rate than slow down by covering up part of your glazing...at least that's what the book says. Oak is most susceptible to degrade because of drying to fast.

In my solar kiln I had R-20 walls, R-30 in the floor, and double glazing. I followed Gene Wengert's plan fairly close although I modified the size and only dried 10' or shorter. I dried partial oak loads and never had to slow down or cover the glazing. This was in north Missouri.

Fil-Dill · January 12, 2011, 08:29:48 AM

Larry, thanks for the help. I will get to building and see what I can learn about monitoring drying rate.

Fil-Dill · January 29, 2011, 08:49:34 PM

I am in central MO and was wondering if anyone has built there own fan controls using a thermstat and timer and also if a humidistat would be worth it.

flibob · January 29, 2011, 10:28:50 PM

I think it is the VA Tech solar kiln uses a photovoltaic with no controler hooked to 12v fans. They say the fans are only needed when the sun shines. It is a nice design and pretty straight forward. Do a google for solar kilns for the info.

pineywoods · January 29, 2011, 10:38:11 PM

On my kiln I just leave the fans running all the time. works fine.

Larry · January 30, 2011, 08:03:14 AM

I used a line voltage thermostat to turn the fans off and on. Worked great in the winter but not at all in the summer because the kiln stayed too hot.

A simple timer works well. You can leave the fans off if cloudy weather is forecast.

Bill Gaiche · January 30, 2011, 11:07:01 AM

Larry, do you have a kiln now? bg

Larry · January 30, 2011, 11:13:37 AM

I do not. Should have the new Nyle kiln up and running in a couple of months.

Bill Gaiche · January 30, 2011, 11:38:45 AM

Ok, thanks and good luck on the new kiln. bg

sawwood · January 31, 2011, 10:23:01 AM

We built a solar kiln but just use a timer to control the fans. Have a load of soft maple and sweet gum in it now. We used
green house platic for the glazing but may put platic on it this summer. Larry i have some red and white oak 5/4
to dry this summer, can i put 4/4 oak in with the 5/4 with out any trouble ? If ok where would you put the 4/4 oak, bottom
or top of the 5/4 ?

Lester

Larry · February 01, 2011, 05:58:14 AM

I dried red and white oak together all the time without problem. Never tried 5/4 with 4/4 but I think it would work ok, as not much thickness difference. Keep a close eye on the 5/4.

metalspinner · February 01, 2011, 07:04:20 AM

The fans in my kiln are controlled with a thermostat. They are attic fans with the thermostat integrated in the fan.

Air drying the lumber prior to placing in the kiln has yielded better lumber for me. But I do not try to control things very much once loaded. "Set it and forget it" is my motto. :

:D

flibob · February 01, 2011, 10:33:48 AM

Metalspinner,

What you say about your fans seems to support the Virginia Tech idea of a photo voltaic cell with no controler.
I want to build a solar kiln but have no power on site.

metalspinner · February 01, 2011, 01:10:40 PM

Your fans will only be running when they reach the upper temps (during the day). There may be some solar technology you can utilize for the small amount of power you need.