# Solar kiln



## DTrain (Jan 22, 2013)

Any one try something like this before for their cord wood?  Solar kiln for speeding up seasoning.  Sorry can't attach pic with iPad.
Pic: http://wnyhardwoods.wordpress.com/2010/02/03/solar-kiln-first-loading/kiln1/
http://sbio.vt.edu/about/extension/vtsolar_kiln/


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## bmblank (Jan 22, 2013)

My dad and his friend built a solar kiln for my hardwood flooring (red oak, from my dads land). Got it down between 6 and 9%. I was considering building my woodshed in a somewhat similar fashion. I was sorta thinking something in the passive solar heat kinda way. But no experience in it yet.


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## DTrain (Jan 22, 2013)

I have to build a wood shed this summer.  I think I might give'r a go.


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## bmblank (Jan 22, 2013)

Take plenty of pics. I'll be building one shortly also.


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## bmblank (Jan 22, 2013)

A shed, not necessarily a kiln.


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## lukem (Jan 22, 2013)

My dad has a solar kiln.  Basically a shed roofed and sided with clear plastic.  Works good for boards.  Not sure about cord wood.


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## swagler85 (Jan 22, 2013)

DT if you buy the app tapatalk you can post pics. I put it off for a long time but tried it and I love the app. Well worth the small expense and it works with most all forums.


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## renewablejohn (Jan 23, 2013)

We have commercial solar kilns drying upto 250 m3 of split logs at a time. Normally takes 3-6 moths to get logs below 20% moisture content.


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## renewablejohn (Jan 23, 2013)

We have commercial solar kilns drying upto 250 m3 of split logs at a time. Normally takes 3-6 months to get logs below 20% moisture content.


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## DTrain (Jan 23, 2013)

renewablejohn said:


> We have commercial solar kilns drying upto 250 m3 of split logs at a time. Normally takes 3-6 months to get logs below 20% moisture content.


What do you think if was cut and split to stove size sticks?  Less time I would think.


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## Jon1270 (Jan 23, 2013)

I doubt a home solar kiln for firewood would be a good use of resources.  It would speed things up, but also require extra handling of the wood since it's unlikely to be big enough to hold your whole winter's supply.  Might be nice for the first year or two if you have no other way to get dry wood, but after that it would be pointless; by then you could have achieved the same thing by just letting it dry out in the sun and wind.  So to make sense I think it would need to pay for itself -- the engineering time, the materials, the labor -- in the first 2 years.  That seems improbable.


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## Dune (Jan 23, 2013)

Jon1270 said:


> I doubt a home solar kiln for firewood would be a good use of resources. It would speed things up, but also require extra handling of the wood since it's unlikely to be big enough to hold your whole winter's supply. Might be nice for the first year or two if you have no other way to get dry wood, but after that it would be pointless; by then you could have achieved the same thing by just letting it dry out in the sun and wind. So to make sense I think it would need to pay for itself -- the engineering time, the materials, the labor -- in the first 2 years. That seems improbable.


 
A  solar firewood kiln can be as simple as a framework with clear plastic stretched over it. The key is that the plastic not touch the wood at any point and that the plastic not reach to the ground.


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## Jon1270 (Jan 23, 2013)

Dune said:


> A solar firewood kiln can be as simple as a framework with clear plastic stretched over it.


 
Would be far less effective than the sort of kiln linked to upthread, but certainly cheaper and it might help a bit.  I doubt it would make a dramatic difference in drying time.

My familiarity with wood drying is more oriented towards lumber rather than firewood, but the general problem is that any enclosure reduces ventilation to some degree, so an effective kiln has to balance ventilation and temperature gain against each other so that the relative humidity ends up lower rather than higher.  Some designs work, and some don't.


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## Dune (Jan 23, 2013)

Jon1270 said:


> Would be far less effective than the sort of kiln linked to upthread, but certainly cheaper and it might help a bit. I doubt it would make a dramatic difference in drying time.
> 
> My familiarity with wood drying is more oriented towards lumber rather than firewood, but the general problem is that any enclosure reduces ventilation to some degree, so an effective kiln has to balance ventilation and temperature gain against each other so that the relative humidity ends up lower rather than higher. Some designs work, and some don't.


 
The idea is to remove moisture, not ventilate. The heat created by the tent caused moisture to vaporize, then condense on the plastic and drip away.
These simple kilns, promoted by Mother Earth News since the seventies have been known to reduce seasoning time to as little as five months.


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## Jon1270 (Jan 23, 2013)

Ah, letting moisture fall away as liquid rather than vapor.  Neat idea.  Anyone have a link to one of the Mother Earth news articles on this?


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## ScotO (Jan 23, 2013)

Dune said:


> The idea is to remove moisture, not ventilate. The heat created by the tent caused moisture to vaporize, then condense on the plastic and drip away.
> These simple kilns, promoted by Mother Earth News since the seventies have been known to reduce seasoning time to as little as five months.



I plan on building my shed similar to this.  I'll still season it two years uncovered, and load I into the "shiln" (kiln/shed) in Tue summer prior to using it.  That should make it absolutely PRIMO for the stoves.  Hoping to attempt the build this summer.   Don't worry, I'll take plenty of pics and document the whole project.


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## gerry100 (Jan 23, 2013)

I've got a basic open front shed with a sloped metal roof but...

If I were doing it over again I might consider replacing the metal with translucent fiber glass panels expecting that it would get much hotter in the summer. the open front may negate much of the advantage however.


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## Augie (Jan 23, 2013)

Here is a link to an article from Cornell summarizing a study of this very fact. They say that in 3 months 8inch splits and rounds are below 20% moisture content. I will probably tent up 4 full cords this summer in an attempt to speed the process. As Im a new burner I am trying to build up my supply of seasoned wood. By tenting 4 cords I should have enough seasoned for the following winter. Of the 4 I was thinking of tenting some oak in an attempt to shorten the seasoning from 3 years to 2 maybe and then Ill be set for the future. 

Looks pretty easy Air in from the bottom and a small vent at the top. priced it out based on my situation looks like it will cost $40 for the four cords for cheap plastic and I have enough scrap lumber to fab up the frame. $40 for 4 seasoned full cord is pretty cheap IMHO.


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## DTrain (Jan 23, 2013)

Nice, I like to see the ideas flowing! Just when I thought Jon1270 had whizzed in my corn flakes, I see the book is not closed on this idea.  Thanks for adding your two cents every one!

That would be a sight seeing that water condense.  Just like those survival shows to get fresh water in the desert.  Would the surface of the plastic require a point of condensation to aid in condensing?


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## Augie (Jan 23, 2013)

Nope just the high peak to collect the moisture and space for it to fall but not touch the wood. I have seen people using kilns for drying wood utilizing solar attic vent fans to move air. this is a careful balance though. you want temps high enough to keep moisture moving out of the wood and enough air movement to clear the moist air. Im guessing that you can get most species dry in a summer,(IE Maple, ASh, Pine, Beech, Elm, Walnut, Aspen, Dogwood) but im hesitant to call oak until I try it.


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## Jon1270 (Jan 23, 2013)

DTrain said:


> Just when I thought Jon1270 had whizzed in my corn flakes...


 

Aww, I would never do that.  I might try to dissuade you from whizzing in your own corn flakes.

Thanks for the link to that Cornell document, Augie.  It's a shame Mr.(?) Stone didn't set up a control group for his test.


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## Jon1270 (Jan 23, 2013)

On reflection, it could be that kilns meant for drying long pieces of lumber down to 6-8% MC without creating defects like case hardening and checking need to maintain some combination of higher / more consistent / more controllable temperatures and humidity levels, thus the electric fans and insulation that go into those arrangements. Firewood doesn't need to meet the same specs,  so something simpler might very well suffice.

If only such a kiln worked in the shade...


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## bmblank (Jan 23, 2013)

It will work in the shade... You just need a whole lot of heat lamps pointed at it 24/7. :-D


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## DTrain (Jan 23, 2013)

Jon1270 said:


> Aww, I would never do that.  I might try to dissuade you from whizzing in your own corn flakes.
> 
> Thanks for the link to that Cornell document, Augie.  It's a shame Mr.(?) Stone didn't set up a control group for his test.



Well you did a little, but I know it was coming from a good place!


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## Jon1270 (Jan 23, 2013)

Sorry.  It was an accident.


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## DTrain (Jan 23, 2013)

Jon1270 said:


> Sorry.  It was an accident.



No no not like that.  All your points made lots of sense. I had my hopes up about the idea.  I guess it would have been better if I said you did me a favor and whacked me with the reality stick.  But I was trying to be funny.  My bad.


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## ScotO (Jan 23, 2013)

Jon1270 said:


> On reflection, it could be that kilns meant for drying long pieces of lumber down to 6-8% MC without creating defects like case hardening and checking need to maintain some combination of higher / more consistent / more controllable temperatures and humidity levels, thus the electric fans and insulation that go into those arrangements. Firewood doesn't need to meet the same specs, so something simpler might very well suffice.
> 
> If only such a kiln worked in the shade...


 They most definately DO need balanced moisture to dry lumber.  The point of a kiln when drying wood for lumber is to remove the INNER moisture with heat, but keeping the air very humid so the OUTER wood doesn't dry out too fast.  Most solar kilns I've seen that were designed for lumber had a big pan of water on the floor of the kiln to help keep the humidity high.  You wouldn't want that in a firewood kiln.

I like the idea of drawing the vapor up and letting it 'run' off of the inside of the ceiling to the outer wall, where it could drip away......I'm definately going to do this to my shed in some form or another, when I get around to building it.


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## Blue2ndaries (Jan 25, 2013)

Scotty Overkill said:


> "shiln" (kiln/shed)


Nice...you need to trademark that Scotty!  



Scotty Overkill said:


> ...Don't worry, I'll take plenty of pics and document the whole project.


 
Gotta uphold the namesake...Overkill!


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## area_man (Aug 29, 2014)

What happened with the solar kilns?  Did anybody have success with that method?  Would it help to have a condenser in the kiln to take the moisture out of the air during the day?


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## Woody Stover (Aug 29, 2014)

area_man said:


> Would it help to have a condenser in the kiln to take the moisture out of the air during the day?


If you've got some type of passive ventilation, that should be good enough. I guess the question is, how much? Trial and error would answer that.


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## Jon1270 (Aug 29, 2014)

Such a condenser would otherwise be called a dehumidifier, and yes, it could help, but dehumidifiers are expensive to run, and the liquid condensed in a lumber kiln tends to be rather corrosive so you need a specialty dehumidifier designed for lumber kilns, which is also expensive.


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## maple1 (Aug 29, 2014)

Is there a 'Whatever happened to..?' thread on the site anywhere?

Like, in this case, Scotty Overkill? Used to be a solid poster - I see other names in other posts that get bumped up too that I kind of had forgotten about until seeing the name again.

EDIT: Guess the forum software edited out the name I typed...


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## Dune (Aug 29, 2014)

area_man said:


> What happened with the solar kilns?  Did anybody have success with that method?  Would it help to have a condenser in the kiln to take the moisture out of the air during the day?



They have always worked since they first designed. 
If you are uncertain, research solar lumber kiln. The design is simple enough. 
An even simpler temporary (and inexpensive) fire wood kiln can be constructed to reduce seasoning time by 60% or so. 
If you can't find reference to it, I will detail it out here (again).


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## Dune (Aug 29, 2014)

Augie said:


> Here is a link to an article from Cornell summarizing a study of this very fact. They say that in 3 months 8inch splits and rounds are below 20% moisture content. I will probably tent up 4 full cords this summer in an attempt to speed the process. As Im a new burner I am trying to build up my supply of seasoned wood. By tenting 4 cords I should have enough seasoned for the following winter. Of the 4 I was thinking of tenting some oak in an attempt to shorten the seasoning from 3 years to 2 maybe and then Ill be set for the future.
> 
> Looks pretty easy Air in from the bottom and a small vent at the top. priced it out based on my situation looks like it will cost $40 for the four cords for cheap plastic and I have enough scrap lumber to fab up the frame. $40 for 4 seasoned full cord is pretty cheap IMHO.


Vent at the top is counter productive; you will be venting heat. Moisture condenses and exits as water. 
Important factors of construction;

1. Plastic must not touch the wood at any point.
2. Plastic must not touch the earth.


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## paul bunion (Aug 29, 2014)

I have been playing with a small scale one this year.  One row on a half width pallet.    Minimal ventilation and maximum heat gain seems to be the key as others pointed out above.  I started out with an open pallet bottom.     Not till I put plastic on the pallet was I able to achieve elevated temperatures in the lower reaches of my kiln.   My top and sides are fully enclosed with no purposeful venting other than it isn't sealed tight.   You certainly do not need active ventilation.   If you gap your lid like the Cornell design you will make little more than a solar powered convection current pulling cooler air up through.   I  do note that the Cornell study completely lacks any measurement of its effectiveness.  It just says after 3 months the sample elm was bone dry and burnt freely which is rather short on facts.    The Alaska/Fairbanks kiln is also flawed in that they allowed a large area for ventilation and did not try to maximize heat gain.


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## BSH1F (Sep 1, 2014)

i dropped a white oak in april this year, split and stacked on skids by may 1st. i wrapped it in 6 mil clear plastic and only had the bottom foot exposed, on aug. 1st i lifted the plastic to only cover the top. today i pulled 5 pieces from different parts and have between 19%-24% moister. this is only my first full summer to mess around with the solar drying, by next summer i will build a structure.


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