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Author Topic: Solar Kiln build  (Read 6083 times)

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Offline fishfighter

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Re: Solar Kiln build
« Reply #20 on: June 21, 2017, 11:53:58 am »
Looking good. ;D

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Re: Solar Kiln build
« Reply #21 on: June 21, 2017, 07:39:19 pm »
Looking good. ;D

Thanks...

I did not get enough done today to post any new pictures.
I'm putting up the inside plywood across the top inside.
It take so much time working around all the studs that its going slow.
I'm hoping tomorrow I will be done with that part.
Then come the itchy insulation. Uck...
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Re: Solar Kiln build
« Reply #22 on: June 21, 2017, 09:06:36 pm »
Just a though today as I was building this kiln...
I was wondering if I could use this thing to help heat my home in the winter. ?
What do you all think ?  Dry wood in the summer and heat my home in the winter...
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Offline GeneWengert-WoodDoc

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Re: Solar Kiln build
« Reply #23 on: June 21, 2017, 10:44:34 pm »
In the winter, due to low sun angle and short daylight. The solar input is low, so you might heat the air from 32 F outside to 60 F during the day, but then you would have to heat the air further before it goes into your home.  Further, your home is perhaps 10x more volume than the kiln.

What does it cost per day to heat your home?  In WI with natural gas we had a bill of $50 for the coldest months for gas.  If the kiln save $5 per month or maybe $30 per year, the cost of piping would probably be much more.

On the other hand, if you have a garage that is unseated, a little solar heat would make the garage feel more comfortable during the day.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline ljohnsaw

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Re: Solar Kiln build
« Reply #24 on: June 22, 2017, 02:03:23 am »
What does it cost per day to heat your home?  In WI with natural gas we had a bill of $50 for the coldest months for gas.  If the kiln save $5 per month or maybe $30 per year, the cost of piping would probably be much more.
Wow.  I know your winters are a lot colder - my cold months (50 day/32 night) heating (to 65) is $200-250/month for gas!
John Sawicky

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Re: Solar Kiln build
« Reply #25 on: June 22, 2017, 06:24:16 pm »
Insulation ...

 

 

More plywood...

 

 

 

 

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Offline GeneWengert-WoodDoc

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Re: Solar Kiln build
« Reply #26 on: June 23, 2017, 04:49:07 pm »
Maybe you gas usage includes hot water.  I was just talking heating.  Also our house was 2x6.  We paid around $0.50 per therm.  We also had a flat fee of $17 per month, which I did not include.  Of course, there is electric for the fan too.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline ljohnsaw

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Re: Solar Kiln build
« Reply #27 on: June 23, 2017, 07:42:32 pm »
Maybe you gas usage includes hot water.  I was just talking heating.  Also our house was 2x6. We paid around $0.05 per therm.  We also had a flat fee of $17 per month, which I did not include.  Of course, there is electric for the fan too.
Now that gives me a sick feeling in my stomach! ::)

I don't have a flat rate portion but my gas rate is $1.31/therm! >:(  My gas bill now (in the summer) is for running two tankless water heaters (so just on actual use) and a gas clothes dryer was 8 therms and is $11 for last month.
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Offline GeneWengert-WoodDoc

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Re: Solar Kiln build
« Reply #28 on: June 24, 2017, 11:10:21 am »
My error...$0.50 and not 0.05.   A typical house used 700 therms per year for heat or $350 per year for gas heat.
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: Solar Kiln build
« Reply #29 on: June 24, 2017, 11:15:19 am »
Question...

Looking at many plans on google I see that some people fan the air in from the bottom and out the top. Other people fan the air in from top and out the bottom. What do you thing is best?  I'm thinking in from the top so it pushes the hot air down through the wood and out the bottom. I'm thinking the other way would waste all the upper heat.

So what do you all think?
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Offline scsmith42

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Re: Solar Kiln build
« Reply #30 on: June 24, 2017, 11:59:09 am »
Question...

Looking at many plans on google I see that some people fan the air in from the bottom and out the top. Other people fan the air in from top and out the bottom. What do you thing is best?  I'm thinking in from the top so it pushes the hot air down through the wood and out the bottom. I'm thinking the other way would waste all the upper heat.

So what do you all think?

All 4 of my VT Design based solar kilns have vents located directly behind the fans, and a second set of vents located at the bottom of the doors on the discharge side of the stack.

When operating a solar kiln, I tend to adjust the vent settings throughout the drying process.  With slow drying woods such as oak, at the beginning of the cycle I keep the vents closed.  There is enough leakage to allow some air exchanges w/o damaging the lumber by drying too quickly.  On the other hand, if I have a load of 4/4 pine in the kiln, then the vents will be open.

Vent position is also based upon the amount of lumber in the kiln.  If I have a half charge of a medium drying rate wood such as maple or walnut, the vents are closed.  If I have a full charge, then the vents may be cracked open a bit at the beginning of the kiln cycle.

Keeping the vents mostly closed also helps to increase the temperatures inside the kiln.  Drying at a higher RH%, higher temp allows you to dry faster but with less risk of damaging the lumber.  If you keep your vents fully open, the kiln will run at a lower temp, and with lower RH% inside, which will result in a longer drying time and potential damage to slow drying species of green lumber.
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Offline GeneWengert-WoodDoc

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Re: Solar Kiln build
« Reply #31 on: June 24, 2017, 01:38:54 pm »
Fans should blow southward across the collector space and then northward through the pile.  If you go the other way, you will bring in some fresh air at the bottom and it, with recirculated air, will go directly through the pile, and then pick up heat as it goes upward and then some of this freshly heated, drier air will be exhausted before it can do evaporation.

I agree with the comments on how to operate the vents.  In fact, with pine, you may even consider opening the main doors to increase venting, as it is high humidity that will be slowing drying the first day or two.
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: Solar Kiln build
« Reply #32 on: June 24, 2017, 02:04:11 pm »
I dont see vapour barrier on the inside. Just wondering.
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Re: Solar Kiln build
« Reply #33 on: June 24, 2017, 02:07:58 pm »
I dont see vapour barrier on the inside. Just wondering.
The vapor barrier is on one side of the insulation.
Do I need more ?
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Re: Solar Kiln build
« Reply #34 on: June 24, 2017, 02:14:03 pm »
I'm painting the inside with a 50/50 diesel & tar mix to get my flat black
For the inside walls.  I made a gazebo with this mix and it works great.
Within one or two weeks it's dry to the touch and it really protects the wood.
This should also help with the vapor barrier.  I have stoped working in it until
I finish making myself a metal break so I can alum cap some exposed wood parts on the kiln.
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Re: Solar Kiln build
« Reply #35 on: June 25, 2017, 01:15:04 am »
You just.need a vapour barrier on the inside to keep moisture from migratin in to the insulation. It also seals it up  from air leaks
The same as one would do for a house. But only the warm side gets it.
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Offline GeneWengert-WoodDoc

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Re: Solar Kiln build
« Reply #36 on: June 25, 2017, 09:03:27 am »
A plastic vapor barrier is better than using the insulation barrier, as the plastic "seals" the walls or floor better...unless someone puts a hole in it. 

Unlike a regular kiln where a leak in the vapor barrier means less insulation effectiveness due to wetting and then we can add a little more heat to offset this loss, in a solar kiln we do not have the option for more heat.  So, the solar kiln runs cooler with longer drying time with wet insulation.  With wood walls, decay is also a possibility.
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: Solar Kiln build
« Reply #37 on: June 25, 2017, 04:47:21 pm »
Not sure i would use tar on the inside. Hot day you brush up against it you will be tarred. Some were i read about a black paint that was good for obsorbing heat.
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Re: Solar Kiln build
« Reply #38 on: June 25, 2017, 05:41:52 pm »
Not sure i would use tar on the inside. Hot day you brush up against it you will be tarred. Some were i read about a black paint that was good for obsorbing heat.

Once you mix 50/50 with diesel fuel and it soaks in it does not come off.
It's one of the best wood treatments that I have ever found. After two weeks
it will be dry to the touch.
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Re: Solar Kiln build
« Reply #39 on: June 25, 2017, 06:02:46 pm »
I had to stop and build a tool. One tool I did not have was a metal break.
One part of the solar kiln was not getting covered by glass so I went to
the junkyard and found two rolls of gutter alum. I needed a way to make neat
right angle bends so this is what I came up with. The last picture is a small flat
chunk of plate steel that I made my first practice bends on. It works great.



 

 

 

 

 

 

 

 

 

Collector and builder of many things.
I have a
machine shop
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And a Weld shop
And now a saw mill
and a bunch of new forum friends.