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Author Topic: Which to build? Solar or DH Kiln  (Read 4233 times)

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Offline Glenn1

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Which to build? Solar or DH Kiln
« on: August 18, 2014, 08:46:35 PM »

Hello,

I have been reading many posts but this is my first post.  Over the weekend, I went to Virginia  and picked up 400 bf of 5/4 walnut.  It is beautiful wood and it looks to be over 95% heartwood.  This is my first attempt starting with green lumber.  According to the sawmill owner, the logs were cut a while ago and the ends were not sealed.  There is some checking but it looks manageable.  I realize that my use of AnchorSeal 2 is probably too late but I used it anyway.  It is now stickered and has a corrugated metal roof on to help protect against rain and too much sun.  I live amongst many trees so it should not be overly sunny.  I just hope that I can get enough air circulation.

I am conflicted to build a dehumidification kiln or a solar kiln on my property.  My initial thought was a DH kiln in my workshop (heated and air conditioned) but then I read about the chance of fire.  I found some plans on building a DH kiln in FWW using a dehumidifier and a humidifier.  I also found plans in American Woodworker using similar equipment.  I travel a couple of days each week but I thought my wife would monitor the amount of liquid that came from the unit.  I am also using a Lignomat DX/C with probes inserted into the wood on 12' cables. 

I was planning on a small kiln that would handle at most 400 bf.  I understand the downside of using a solar kiln in the winter but just don't know which style of kiln will give me the best chance of quality lumber.  I am doing this strictly for myself.  I'd rather not wait a full year to get the lumber down to 7-8% but I'm not trying to make a living on it either.  I am a hobbyist. 

Based on plans that I have been evaluating, it looks more difficult and more expensive to build a solar kiln. I am trying to keep my cost down since it will not be used for a business venture.   I am here to get any and all thoughts about my dilemma.  Thank you!
Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer

Offline WDH

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Re: Which to build? Solar or DH Kiln
« Reply #1 on: August 18, 2014, 09:24:26 PM »
I have the Nyle L53 and love it.  It is a little wood drying beast.
Woodmizer LT40HDD35, John Deere 2155, Kubota M5640SU, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

Offline Compensation

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Re: Which to build? Solar or DH Kiln
« Reply #2 on: August 18, 2014, 10:08:01 PM »
Welcome Glenn! I am just a novice to the kiln stuff, but what I learned after I built my solar kiln makes me even more happy that I built it. I found out that a solar kiln cannot drop below 6% I believe. You can store your dry lumber in there without problems. If set up with solar panels and batteries it's free to run and operate. They can kill all your plants when you try to use it as a greenhouse. :D There is an abundance of pros here that will help you like they did for me.
D4D caterpillar, lt10 Woodmizer, 8x12 solar kiln, enough Stihl's to make my garages smell like their factory :) Ohh and built Ford tough baby!

Offline Glenn1

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Re: Which to build? Solar or DH Kiln
« Reply #3 on: August 18, 2014, 10:14:31 PM »
I have the Nyle L53 and love it.  It is a little wood drying beast.

Are you using it strictly as a hobbyist or do you use it for income?  I worry that a Nyle may be more costly than I can justify for a couple of hundred bf per year. 
Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer

Offline mikeb1079

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Re: Which to build? Solar or DH Kiln
« Reply #4 on: August 18, 2014, 10:34:23 PM »
i think pineywoods built a solar kiln while also using a small dh as well, kind of a hybrid system if you will.  there's a couple of threads on it here i think, lemme look....

here's planman's version:

http://www.forestryforum.com/board/index.php/topic,50281.0.html

more related:

http://www.forestryforum.com/board/index.php/topic,68153.msg1066993.html#msg1066993
that's why you must play di drum...to blow the big guys mind!
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Offline Ianab

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Re: Which to build? Solar or DH Kiln
« Reply #5 on: August 19, 2014, 04:08:16 AM »
For the hobbyist I would think a solar unit would be the way to go.  Low cost, easy to operate, low maintenance etc.

For a commercial operation it's not as clear cut. Then you need to be able to get your wood dry on some sort of reliable schedule. Waiting 4 months for the winter load to dry is a problem if you have clients waiting. For a hobby guy, no big deal.

Ian
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Offline jdtuttle

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Re: Which to build? Solar or DH Kiln
« Reply #6 on: August 19, 2014, 06:26:33 AM »
Take a look at Sauno DH kiln made by Logosol. Mine has an 800 BF chamber & does a good job for me. I'm building a 3000 BF Nyle now. If money isn't a problem start with a small Nyle.
Good Luck
Have a great day

Online GeneWengert-WoodDoc

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Re: Which to build? Solar or DH Kiln
« Reply #7 on: August 19, 2014, 08:50:10 PM »
For someone that needs to dry 5000 BF per year or less, the solar kiln is the way to go.  As you get larger, you are betting the business on whether the sun will shine.  Further, you will not get very much drying during the wintertime.  I favor the Virginia Tech design for simplicity and very low operating costs, with no casehardening stress and the low final MC that is desired for most hardwood lumber.  The key to the VT design is one square foot of collector (measured perpendicular to the sun at noon) per 10 BF of lumber.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline red oaks lumber

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Re: Which to build? Solar or DH Kiln
« Reply #8 on: August 19, 2014, 09:01:25 PM »
which ever setup you go with, fire threat in a dh is a non issue. i dont have a working knowledge of solar kilns but, i would think the initial start up costs would be alot less.
the experts think i do things wrong
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Offline YellowHammer

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Re: Which to build? Solar or DH Kiln
« Reply #9 on: August 19, 2014, 11:02:46 PM »
but just don't know which style of kiln will give me the best chance of quality lumber.
All three styles of kilns, whether solar, solar+DH, pure DH, will yield excellent, very high quality lumber.  I've used all three for a number of years and each has its advantages and disadvantageous.  The pure solar is more forgiving but doesn't sterilize consistently throughout the year, and can finish a load in a reasonable time in the summer, but is painfully slow the winter.  The solar+Homeowner DH can be a little more complicated and stressful to the lumber, but will easily finish air dried hardwood in 3 weeks or less.  The pure DH kiln like a Nyle will finish out an air dried load every 5-10 days depending on species.

I'd rather not wait a full year to get the lumber down to 7-8%
Air drying will only get you down so far based on your local seasonal conditions, no matter how long lumber is air dried.  You can do an internet search for what can be expected in your area.  Around here, in North Alabama, 12% is the norm.

Based on plans that I have been evaluating, it looks more difficult and more expensive to build a solar kiln.
Nah, in its most basic form, a solar kiln is just a small, well insulated shed with a couple fans and a slanted sunroof facing South.  ;D.  I built mine out of sawmill wood and Wal Mart box fans in a couple weekends, and I can pick it up with my forklift and move it wherever I want.  If I can build one, anyone can. Logs of very knowledgeable people here on the Forum who can help you out.

Good luck which ever method you choose. 
YH
 
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Offline pineywoods

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Re: Which to build? Solar or DH Kiln
« Reply #10 on: August 19, 2014, 11:50:28 PM »
YH covers  it nicely, it mostly depends on your needs..Sounds like for your operation, solar/dh of appropriate size would fill your needs. The pineywoods design is a bit different from textbook solar units, even dis-regarding the dehumidifier. It is the result of a lot of trial and error and a bit of heartache. Would you believe it can actually RAIN in a kiln? I have no doubt it could be improved. I'd like to see how well or if at all it would work with NO fans...
1995 Wood Mizer LT 40, Liquid cooled kawasaki,homebuilt hydraulics. Homebuilt solar dry kiln.  Woodmaster 718 planner, Kubota M4700 with homemade forks and winch, stihl  028, 029, Ms390
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Offline Glenn1

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Re: Which to build? Solar or DH Kiln
« Reply #11 on: August 20, 2014, 08:43:56 AM »



Thank you Professor Wengert, YellowHammer, WDH, Compensation, Ianab, Pineywoods, mikeb1079, jdtuttle, and Red Oaks Lumber.  From your posts and my low volume of lumber that is needed, I can see that I am being steered towards a solar unit.

Before coming to this site, my research took my to two articles pertaining to making a home made DH unit.  One was from FWW in issue #91 and the other was in an issue of American Woodworker published in 2002.  I am concerned about sterilizing the lumber since my projects will end up in my home.  Are there negatives to building a DH in this manner?  It uses a home DH unit (may last 1-2 years), a small heating unit (they used light bulbs) and a humidifying unit to condition the wood at the end of the process. I believe that it suggests a maximum temperature of 120 through most of the process although I could crank it up at the end for sterilization.  I have room in my shop to build a boxed unit and the shop has heat and an AC unit.

I am not questioning anyone's suggestions and I hope you know that I am very appreciative for  your comments.  If you could point out the negatives to building such a unit, I would be thankful.  Obviously, I do not want to chance a fire but I don't want bugs in my wood either. 

Thank you,
Glenn
Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer

Offline LeeB

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Re: Which to build? Solar or DH Kiln
« Reply #12 on: August 20, 2014, 08:53:21 AM »
I don't see why you couldn't dry it in a solar kiln and the steralize it in a hot box afterward, but then I have no experiance with a kiln.
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, JD 3032 tractor, JD 5410 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

Offline pineywoods

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Re: Which to build? Solar or DH Kiln
« Reply #13 on: August 20, 2014, 09:45:25 AM »
Glenn, with the pineywoods setup, not enough heat to sterilize is not a problem. We have documented 180 degrees more than a few times. The only downside I have seen in a few years of operation, is, it is possible to get some light case hardening, and LeroyC's melted the plastic blades on the fans.. ;D Be aware that trying to make a solar kiln behave like a conventional is an exersize in frustration. They are different.
1995 Wood Mizer LT 40, Liquid cooled kawasaki,homebuilt hydraulics. Homebuilt solar dry kiln.  Woodmaster 718 planner, Kubota M4700 with homemade forks and winch, stihl  028, 029, Ms390
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Offline Glenn1

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Re: Which to build? Solar or DH Kiln
« Reply #14 on: August 20, 2014, 04:15:12 PM »
Glenn, with the pineywoods setup, not enough heat to sterilize is not a problem. We have documented 180 degrees more than a few times. The only downside I have seen in a few years of operation, is, it is possible to get some light case hardening, and LeroyC's melted the plastic blades on the fans.. ;D Be aware that trying to make a solar kiln behave like a conventional is an exersize in frustration. They are different.

Can you tell me where I can get information on your pineywoods setup?  All I know is that it is basically a solar kiln with a DH unit.  I am sure that this is an  over simplification.  With the DH unit operational, do I run the risk of increased case hardening?
Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer

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Re: Which to build? Solar or DH Kiln
« Reply #15 on: August 22, 2014, 12:45:28 AM »
With any kiln, the temperature achieved depends on the energy input and the energy loss.  The greater the difference between these two numbers, the more energy available for heating.  The advantage of solar is that it is free after you have a collector. 

You can get a kiln hotter by increasing the solar collector size or by putting in energy from an outside source such as electricity, propane, etc.

You can get a kiln hotter by reducing heat losses through the walls and floor by using lots of insulation and maybe caulk.  You can reduce solar collector losses by using triple layer of clear material, by moving the black absorber further away, and by using a heat reflecting material such as glass.  You can reduce heat losses by reducing the amount of water to be evaporated...less wood in the kiln or air drying first.

The VT design will achieve 50 F above outside when the lumber is fairly dry.  When really dry or when no lumber is in the kiln or when the fans are off, the temperature near the roof will exceed 200 F on a sunny, warm day.

You can also consider having a cover for the clear solar collector, so you can cover the kiln's main heat loss item on a cloudy day or cold day when losses can exceed energy input.  This is especially helpful when there is an outside source of heat or is a DH unit.

With a DH unit, the electric costs can be large.  Check the current draw of the compressor and its fan.  If your electric bill has a total cost of $.20 per kW, a 110v. unit with 8 amp draw, running 20 hours day will use 0.88 kW or $ 0.18 and hour.  Then x 20 hours is $3.60 a day.  This is true if the unit is for lumber drying, a basement, or other use.

Regarding the AW kiln, I was involved with this kiln.  It does present a fire danger, as it does not have safety controls or features found in other kilns, such as a DH.  The light bulbs are really hot.  I suggest that putting it in your shop or home is not the best idea.  There are a fair number of house fires reported from small DH units that fail, overheat, etc.  The small units are not that safe especially in a small kiln chamber.

Note that if you air dry first, then casehardening stress will not be an issue in a solar, solar-DH, or straight DH kiln.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

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Re: Which to build? Solar or DH Kiln
« Reply #16 on: August 22, 2014, 02:11:47 AM »
Gene,
Would case hardening be an issue if you solar dried first and then used a 'hot box' simular to the AWW idea for a final sterilizing?
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, JD 3032 tractor, JD 5410 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

Offline Glenn1

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Re: Which to build? Solar or DH Kiln
« Reply #17 on: August 22, 2014, 10:38:14 AM »
Dr, Wengert,

I have been looking at the VT solar kiln and I am not able to see black absorber that you mentioned.    In an earlier post, I read that it should be wood that is painted black.  Can you give me a little more detail on that piece of wood.  Can it just be plywood and how far should it be set back from the collector? 

I also found a smaller version online at this site:  http://www.americanwoodworker.com/blogs/projects/archive/2009/09/29/solar-kiln.aspx

In this article, the gentleman speaks about downsizing the VT kiln that you designed.  Again, I can not see any wood mounted below the corrugated roofing material. 

When you speak about a triple layer of clear material to enhance the heating process, would corrugated
roofing material be acceptable?  Can the 3 units be put directly on top of each other or do I need some airspace?

Your thoughts would be greatly appreciated.  Thank you
Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer

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Re: Which to build? Solar or DH Kiln
« Reply #18 on: August 22, 2014, 11:22:15 AM »
Glenn, go here http://www.forestryforum.com/board/index.php/topic,50281.0.html

Lots of pics and good write-up. Some additional tidbits

The transparent roof glazing needs to be transparent to infra-red radiation, in    other words greenhouse quality.
The actual collector is old corrugated metal roofing painted flat black and fastened to the bottom of the rafters
Leave a 6 inch gap at the top and bottom of the collector, in other words the collector is a foot shorter than the glazing. Otherwise, you will probably melt your plastic glazing.
Shut off the dh unit during the day, most of them will have a high temp shutdown somewhere around 100 degrees. residential Dh units don't work very well at high temps.
Yes, the interior of the kiln will cool down at night. Downside to that is extended drying time. Upside is cool down allows the wood to stabilize, fewer defects. The efficiency of the dh goes up dramatically as the temp drops.
Don't get hung up on optimizing everything. Every specification is a compromise, it ain't exactly rocket science  ;D 
1995 Wood Mizer LT 40, Liquid cooled kawasaki,homebuilt hydraulics. Homebuilt solar dry kiln.  Woodmaster 718 planner, Kubota M4700 with homemade forks and winch, stihl  028, 029, Ms390
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Offline Glenn1

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Re: Which to build? Solar or DH Kiln
« Reply #19 on: August 22, 2014, 11:40:30 AM »
I gotcha.....thanks for your suggestions.     :D
Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer


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