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Solar Heated Kiln

Started by GeneWengert-WoodDoc, May 20, 2016, 03:25:52 PM

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GeneWengert-WoodDoc

I just returned from teaching a class where we built 6 smaller version (footprint is 6x10 and capacity is 600 BF plus) of the VT solar kiln.  We also used a solar powered fan.  If you are near Indianapolis and want to see it, one kiln is at the Marc Adams school a few miles south of Indy.

Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

jrose1970

That looks like a great design.  Down the road one day, that is on my list to build a solar kiln.
HFE-36; International 424-37HP; McCullogh Pro 10-10

Savannahdan

I also need to build one.  Thanks for sharing the pic.
Husqvarna 3120XP, Makita DCS7901 Chainsaw, 30" & 56" Granberg Chain Saw Mill, Logosol M8 Farmers Mill

btulloh

Thanks for the pic.  I want to build a solar kiln but want to go smaller than the original VT design.  Maybe even smaller than this one.  300 bf more or less. 

One question (probably a dumb question . . .) - If you want to run a load less than what the collector is designed for, is it best to reduce the collector size?  Would that be species dependent?  I will probably want to run some smaller loads from time to time.  I've even thought about making a couple micro-kilns to dry 50 bf +/-.

Thanks again for posting this pic.

HM126

Glenn1

Doc,
Because I am drying thick stock and oak now, I will be building a kiln and your kiln posted here would be great.  Could you post dimensions, pictures, and information on the solar fans.  I will be putting it where there is no electricity.

Thanks in advance,
Glenn
(met you in Hickory)
Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer

GeneWengert-WoodDoc

The 10 BF to one square foot is for oak, 4/4 or 5/4.  More collector is good for some faster drying species.  Smaller is essential for thicker oak, etc.

Regarding this kiln, Marc Adams School of Woodworking has the number and size of all the pieces needed to 1/16", plus other supplies.  I am hoping, after their school slows down, we can maybe publish these specifics.  I will have lots of pix in an article in Sawmill & Woodlot soon.  Meanwhile, I will try to answer specific questions.

A key to this unit is how the walls and floor are tied together to make a strong structure indeed.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Tree Dan

Hi Gene, are the walls framed with 2x6 or 2x4s?
Also did you double wall the panels?

I would like to build a small kiln just like this.

Thanks

Wood Mizer LT40HD, Kubota KX71, New Holland LS150, Case TR270
6400 John Deere/with loader,General 20" planer, Stihl 880, Stihl 361, Dolmar 460, Husqvarna 50  and a few shovels,
60" and 30" Log Rite cant hooks, 2 home built Tree Spades, Homemade log splitter

GeneWengert-WoodDoc

2x6 floor.  2x4 walls.  Corrugated outer cover and sheet plastic(short life) inside.  For a few more bucks, you can get double-walled flat cover...good choice, but I was trying to control initial costs. Plans and sizes will be available soon...negotiation in process.ok?
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

CedarDude

Solar powered fans seem really overpriced. Any tips/sources for solar powered fans Dr. Wengert?

scsmith42

Looking good Gene.

I'm actually going the opposite way and building two large ones and an intermediate one. 

With my existing solar kiln (standard VT design) I had to sticker on 5' sticks in order to load the maximum amount of 5/4 oak.  Since I use 40" - 48" deep stacks in my Nyle, restickering was time consuming and inefficient. 

So, I modified the design slightly to allow me to put 2K board feet of oak into the large ones, based upon my standard 48" depth stacks.  To achieve this, I increased the width to 20', the door opening to 8', and added 38" to the bottom of the kiln on the short wall. 

The collector is 200 ft2 on two of them, and the third one is designed for 1,400 board feet with a 140 ft2 collector.

When I get done with these I'll have four solar kilns, one Nyle / Woodmizer L200, and a second L200 is on a pallet ready for installation.  The next construction project is a 40' x 80' air drying barn, then modifying the existing air drying barn to move the milling operation into, and then build some additional DH kiln chambers at the end of the new AD barn.

Sleep is overrated!   :D



 
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

xlogger

really adding on there Scott. Nice looking kilns. How are you doing your doors?
Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

scsmith42

Same as the standard VT design; 2x4 on 26" centers with plywood glued and nailed on the outside and a cable / turnbuckle setup on the inside.
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

YellowHammer

Scsmit42,
So it looks like you are doing something I've been considering, building multiple solar kilns optimized for hard to dry, long to dry species and cuts, where a DH kiln isn't always the best choice?  What is your primary targeted use for the solar kilns, your Quarter Sawn White Oak? 

Once I built my second DH kiln, I actually thought about decommissioning my solar kiln, but I still use it constantly, just for lumber that it seems to excel at.  For example, I just dried a nice load of walnut 9/4 live edge slabs at a rate significantly faster than air dried (although much slower than in a DH) and now I have a load of QSWO that just finished up and will go into the DH kiln to sterilize.  All at a much cheaper cost and less effort from me. 

The solar kiln is slow, but very useful, and although it can't dry fast enough to support my entire retail operation, it seems it can dry fast enough to support drying just one or two species or thicknesses that require a very low daily moisture loss.  At least that's whats been knocking me in the head, and looks it like you have come to the same conclusion some time ago and are gearing up?
I'm very interested in your strategy.

YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

scsmith42

YH, I plan to use the new solar kilns as needed to fill in voids in the production process. 

Certainly they will be slated for some 5/4 and 8/4 QSWO, but the other nice thing about them is that you can safely mix and match different species in the same kiln run (unlike with the DH). 

We get a regular amount of business doing custom kiln drying for local folks with 50 - 250 bd ft of lumber that had it milled elsewhere, and solar is a great option to dry the mixed loads.

I'll probably dedicate one of them to a load of 8/4 QSWO.  That stuff requires almost 4 months in the DH kiln, so if I block off 60% of the collector I can dry 2K bd ft at a whack.  Probably take the same amount of time as the DH kiln too.

I'm using spray foam insulation in these, and double pane panels for the solar collectors.  I'm hoping that this combination will extend their usefullness in the late fall and early spring.
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

Baron

I guess I'm a little confused. I've built a VA tech solar kiln and modified it to be loaded with a loader instead of by hand. I have three solar fans running all day and they turn off when the sun goes down. Overall I like the setup. I'm using a pin type moisture detector and the lumber is going into the kiln after a year of air drying at 11-14 % and is coming out at 6-7-% according to the meter.
The kiln runs at about 120 during the day  and cools by the next morn. Now here is where I'm mixed up: according to my metering the stacks are reaching 6-7% in about 5-7 days?  Can that be?  It seems too fast. The last load went in at 10-11% and came out in three long days (6-6.6%) can that be correct? Seems fast. I mean obviously it is allot lighter. But I read where oak is taking 4 weeks and so forth. May I assume that is green oak? 
Any advice.
Baron

GeneWengert-WoodDoc

You are perfect in drying time. Four weeks of good weather for 4/4 oak is for green with no pieces over 80% MC.  The VT kiln should dry at about 1-1/2 to 2% MC loss per day in the sunny summer day.

I would suggest that you consider going into the kiln sooner, rather than use such extensive air drying. Long air drying has a risk of some quality loss due to rain and sun. Of course an air drying shed is better than open air drying.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Baron

Yes i noticed the quality loss and after catching up I'll try to move up to kiln sooner.
I just couldn't beleive it was doing so well. Very easy to use.

Carson-saws

GeneWengert-WoodDoc....Looks fantastic!...Solar kiln..in my opinion...is the best way to go...I figure back in the day there we not to many "kotter kilns" around and they dried their wood with good ole Mother Nature.  What they didn't or couldn't wait to dry,  green building was essential. 
Let the Forest be salvation long before it needs to be

Baron

I like the kiln and especially the solar powered fans. I work alone and it take a long time to get around to everything. Thanks

Baron

I have a new nut to crack and I wonder if you good folks might have a solution. On the hottest of days here in PA the interior of the kiln don't quite reach 130°. I am not sure that bugs and diseases are killed at that temp and I certainly found out the hard way that resin isn't set. If I understand it correctly raising the temp at the end of a drying cycle to 143° or so for several hrs will both kill what needs to be killed and set sap to unacceptable wood working level. I added two 1500 watt heaters and it only raised the temp 9-10°. Am I trying to do too much, is my understanding leading me into an unnecessary direction? I want to provide that which people will appreciate and I don't think runny spruce or pine sap will be appreciated.
I'm wondering how high the temps get in your kilns.
The thought of adding a 6500 watt baseboard heater sounds plausible since I only need it for a day per load.

Any comments appreciated.

Baron

SCSmith I thought of building a long version of this kiln onto a long foundation incorporating moveable interior walls. This would allow for the accommodation of multiple lengths in a more efficient manor. Nice set up you have there.

bkaimwood

Quote from: Baron on July 07, 2016, 09:41:13 AM
I have a new nut to crack and I wonder if you good folks might have a solution. On the hottest of days here in PA the interior of the kiln don't quite reach 130°. I am not sure that bugs and diseases are killed at that temp and I certainly found out the hard way that resin isn't set. If I understand it correctly raising the temp at the end of a drying cycle to 143° or so for several hrs will both kill what needs to be killed and set sap to unacceptable wood working level. I added two 1500 watt heaters and it only raised the temp 9-10°. Am I trying to do too much, is my understanding leading me into an unnecessary direction? I want to provide that which people will appreciate and I don't think runny spruce or pine sap will be appreciated.
I'm wondering how high the temps get in your kilns.
The thought of adding a 6500 watt baseboard heater sounds plausible since I only need it for a day per load.

Any comments appreciated.
If you want to set pitch, we have to START at 160...better to see even 170 or more...
bk

scsmith42

Quote from: Baron on July 07, 2016, 09:45:34 AM
SCSmith I thought of building a long version of this kiln onto a long foundation incorporating moveable interior walls. This would allow for the accommodation of multiple lengths in a more efficient manor. Nice set up you have there.

Thx.  Weather permitting, tomorrow we will install the rafters, paint them and get the glazing in place. 

The only benefit that I can see of a movable wall versus using fabric baffling (we use Tyvek housewrap and a staplegun to quickly baffle the kilns), is that a movable wall would allow you to effectively reduce the size of the collector area so that you could optimize the drying rate for your load.  It might be a bit challenging though getting it to quickly install around the fans.

I prefer though to simply load the kiln to the appropriate quantity for the size of the collector, and baffle it and keep things full width.  For us, time is money and the quicker that we can load and get going the better the bottom line.
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

GeneWengert-WoodDoc

The wood needs to reach 133 F throughout, so 150 F air temperature is a practical minimum. To set the pitch ( which means evaporating pitch molecules that would be liquid at 90 F or so), the air temperature is best at 160 F or hotter.

Is this what you need?
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

xlogger

Gene, how long at 160° +?
Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

GeneWengert-WoodDoc

The longer you are at 160 F, the more pitch that will be evaporated.  As it takes time for the vapor to move, thicker takes longer. Also, the hotter you go, the shorter the time.  So, 24 hours does pretty good for 1-1/2" thickness and thinner at 160 F for most species.  Real sappy wood takes longer.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Baron

I was thinking that the high temp should come at the end once the MC was where you wanted it (6% or so). If I have to go to 160° then perhaps it would be wiser to do it at the beginning or middle of the kiln cycle. Do you have suggestions on that as I don't want to have case hardening and so forth.
Also how do you suggest I get this solar kiln up to 160°?  I was thinking electric heaters ......

WDH

Ricky,

Not sure that the Nyle L53 Unit is designed for more than 155 degrees.  I saw that somewhere in the specs.  We need to call and ask Stan at Nyle.  That is why I run mine at 150 degrees at the end.  Not ideal, but I am sure that it still does a lot of good. 
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

xlogger

Quote from: WDH on July 09, 2016, 10:44:51 AM
Ricky,

Not sure that the Nyle L53 Unit is designed for more than 155 degrees.  I saw that somewhere in the specs.  We need to call and ask Stan at Nyle.  That is why I run mine at 150 degrees at the end.  Not ideal, but I am sure that it still does a lot of good. 
Talked to Stan today and ask him about this. He said only up to 160°, something about the wiring connections.
Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

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