The Forestry Forum

General Forestry => Drying and Processing => Topic started by: kkcomp on March 22, 2024, 06:55:50 AM

Title: And yet another solar kiln question
Post by: kkcomp on March 22, 2024, 06:55:50 AM
Getting ready to assemble myself a solar kiln. Well my wife was asking about it and had a question that I just couldn't answer. Over time we somewhere or somehow have collected several large mirrors like those in a bathroom. Her question was wouldn't it work better if you put the mirrors on the back wall and directed that sunlight to the wood? (Maybe she just wants to get rid of them) I of course wonder about too much heat, effort vs gain or breaking the mirrors loading and unloading. Still under the premise of happy wife happy life I figured I would see if anyone had thoughts about the idea. 
Title: Re: And yet another solar kiln question
Post by: Oth on March 22, 2024, 07:03:17 AM
You want to absorb all the energy of the sun, not reflect it. Paint em black and they'll do great   :wink_2:

Title: Re: And yet another solar kiln question
Post by: YellowHammer on March 22, 2024, 07:13:49 AM
Yes, but a good question nonetheless.  You want the energy of the sun to heat the kiln atmosphere to control its temperature by impacting solar collectors, but not to direct the energy onto the surface of the wood which will result in localized surface heating, deformation and cracking.  Similar to putting a stack of wood out in the summer sun, which will ruin the top surface of the boards.

 
Title: Re: And yet another solar kiln question
Post by: kkcomp on March 22, 2024, 07:38:41 AM
Quote from: YellowHammer on March 22, 2024, 07:13:49 AMYes, but a good question nonetheless.  You want the energy of the sun to heat the kiln atmosphere to control its temperature by impacting solar collectors, but not to direct the energy onto the surface of the wood which will result in localized surface heating, deformation and cracking.  Similar to putting a stack of wood out in the summer sun, which will ruin the top surface of the boards.

 
So essentially you want to bake the wood not fry it? I think that's an explanation she can relate to.
Title: Re: And yet another solar kiln question
Post by: doc henderson on March 22, 2024, 09:56:46 AM
If you could position the mirrors to reflect sunlight/heat from the outside that otherwise would not go into the kiln.  Lots of discussion around having a kiln that can move and remain oriented directly at the sun, rather than being optimized to the sun at about noon.  I am sure there are mechanisms to change the angle of the mirrors and focus sunlight into the kiln throughout the day as the sun moves.  you could prob find a position and angle that would get more energy in the kiln in the am and pm when the sun is shining on the ends of the kiln and less of a direct shot into the front (south facing glaze).  many great engineering puzzles to be sought after... if you like puzzles. ffsmiley   many of us do.  ffcool   you can work on efficiency.  a mirror redirects light but does not amplify it.  same with a lens like a magnifying glass.  energy is neither created nor destroyed, so the heat generated by the sunlight entering the kiln is what it is.  efficiency however can make use of all of it.  look at LED energy requirement to make light compared to incandescent.  bringing in more light can be complex, or as simple as making a larger glaze area.  good insulation and seals will make your kiln more efficient.  Maybe put the mirrors in the kiln, so you can straighten your hair before you go in the house.   :wink_2:
Title: Re: And yet another solar kiln question
Post by: reride82 on March 22, 2024, 05:11:38 PM
Like Doc says, I would set the mirrors up on the outside of the kiln to redirect more sunshine into the kiln. Think satellite dish design to help collect more sunshine and direct it to the collector, or like the gals in the 70s-90s using reflective surfaces to get more sun to tan faster ffcheesy