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Augmenting Solar Kiln10/3
Hello – I read Dr. Wengert’s response on the forestry forum regarding the issue of adding a DH unit to a solar kiln, and pasted it below. The solar kiln was being used to dry red oak.
“Regarding the use of a DH unit, once the lumber is under 35% MC, there is not much stress relief due to high RH, and no additional stress created so faster drying for more hours per day can be used. However, in general, someone using a solar kiln is doing so because of the low cost and small quantities needed annually. That is, solar drying is ok for a hobbyist and maybe a very small business. Adding a DH unit will increase costs of operation and will dry faster. If adding a DH unit, it is likely more economically efficient to go 100% DH and forget about solar. Drying with a DH at high MC will create stress (casehardening) that may need to be relieved at the end of drying.”
For my project, time is of the essence to dry the 5 ˝” thick by 11 ˝ inch wide ponderosa boards currently in my solar kiln, so I’m looking to augment the kiln operation over the short term, whereas for future loads I’ll have time flexibility, making the solar only option viable. As October hits I’m seeing nighttime temps in the 20’s and 30’s.
The moisture content in my boards varies between 14 and 22 percent.
To dry my boards faster, should I add a DH unit or a heater, or both?
If I add a heater, is my moisture content low enough that I can just crank up the heat?
Any help is appreciated! Thanks - Dan
I suggest heat alone. There is no chance of increased casehardening at these low MCs. Crank up the heat, but be careful to avoid over drying.