Solar Kiln Conditions And Variables - Automated Approach

[Pepe_Silvia]

Since I have basically finished the construction of my solar kiln, I'm going to move on to automation and data collection.

The plan is to have the following measurements:

• Temperature Inside Kiln (2 locations)
• Temperature Outside Kiln
• Humidity Inside Kiln (2 locations)
• Humidity Outside Kiln
• Ambient Light Sensors Inside Kiln
• Probes In Sample Wood To Measure Resistance/MC

There will also be a relay to control the two fans, which will be ~1400 CFM apiece gable mount fans.

After some perusal of the forum, I've found that there are two conditions I should be using to determine when the fans should be running.

• 20 degree or greater difference between inside and outside (Cold Weather Solar in Drying and Processing)
• RH inside kiln is sufficiently high (Green House Solar Kiln in Drying and Processing)

Can someone quantify what 'too low' is in the context of humidity inside the kiln?  What should my trigger point be to turn the fans on?

Any other measurements I should be taking?

[GeneWengert-WoodDoc]

"Too low" depends on species

[Pepe_Silvia]

Is there a reference where I could look it up and set it depending on what species I'm drying?  Or is that something I'm going to have to learn on my own?

[tmrayner]

Did you ever get anywhere with this idea?  I was contemplating the same thing but haven't built the kiln yet.  Was hoping to add solar panel to power fans and supply supplemental heat in the morning when there is light but temps are not high enough to run the fans. 

[doc henderson]

If it is too dry, you will get more degrade as the gradient from core to surface in greater.  many traditional kilns determine the RH by the wet bulb/dry bulb difference.  you can take those differences and convert to RH in the tables.  NHLA has several of Dr. Wengert's webinars.  He also wrote the book drying hardwood lumber (on line)  Most wet wood would need up around say 85% RH early on.