I built a 12.5' x 28' greenhouse to store and dry wood--working awesome.

[RobertNH]

Well then, I hope I did!

 

[RobertNH]

Here's a link to my experiments with drying: https://www.hearth.com/talk/threads/expeditided-wood-drying-solar-kiln.131537/page-2

All three work, just some better than others.
The Big Black Box shown was changed (and I show this) to a clear cover.
Made quite the difference.

The S&G (just a clear plastic over the pile) worked quite well!
For just the cost of plastic, very inexpensive way to go.

My Display Case (the Solar Kiln) works the best.

We just had a bad heavy snow storm and I've cleared some of the downed limbs and added them to the small kiln.
Largest piece being 5" round.
I'm curious how long it will take to get to 20%, especially with this being winter now and no more ambient temps being over 35*..
I read 90* in it just the other day!
So it still gets hot enough!

 

[solarguy2003]

Just a little fall update with some more data. The greenhouse/solar dryer continues to perform well. The wood rounds that have been cut and stacked outside all read 41-45%.

The four random splits that I checked on the east end (it's been split and stacked in the greenhouse 3-4 weeks read: 22, 23, 34, and 25%

The four random splits that I checked on the west end (it's been split and stacked in the greenhouse ~3 months read: 17, 23, 16 and 21%

The old stuff that I could still reach (been in there a year or so) read; 9, 11, 9 and 7%

All moisture readings done on a freshly split face across the grain with an inexpensive but verified (fairly) accurate 4 pin chinese moisture meter.

And the tomato plants and fig trees seem pretty happy too.

Since I had plants in the greenhouse this summer, I added a second cheap box fan to insure the plants didn't overheat. It worked, the plants never overheated. But it was also not as hot and steamy as last year with just one fan. The wood still seems to be drying nicely and next year I'm going back to one fan and see if the plants tolerate the additional heat ok. I'm sure there is some optimum ventilation rate that balances top temperature with rapid moisture removal.

 

[HisTreeNut]

I just read through the thread and that's impressive.
Has me thinking...

 

[BlueRidgeMark]

It's been interesting reading this thread and seeing the initial skepticism that was expressed. The science of this is undeniable, and not at all complicated.

I did something like this on a very small scale one year when I was short of dry wood. I just stacked a pallet with wood, and wrapped it in clear plastic food wrap, including the top. I used a 12" duct elbow as a vent in the top, and wrapped it into place. Pure convection. Within a couple of hours there were drops of condensation visible on the inside of the plastic. I got a pallet fully of nicely dry wood in a matter of a couple of months. I don't have a moisture meter to provide a number, but it sure burned well a few months after being wrapped up.

Now that I've seen the hoop kiln in all its glory, my wife is going to hate this forum. I have another project in my future!

 

[RobertNH]

Just a little fall update with some more data. The greenhouse/solar dryer continues to perform well. The wood rounds that have been cut and stacked outside all read 41-45%.

The four random splits that I checked on the east end (it's been split and stacked in the greenhouse 3-4 weeks read: 22, 23, 34, and 25%

The four random splits that I checked on the west end (it's been split and stacked in the greenhouse ~3 months read: 17, 23, 16 and 21%

The old stuff that I could still reach (been in there a year or so) read; 9, 11, 9 and 7%

All moisture readings done on a freshly split face across the grain with an inexpensive but verified (fairly) accurate 4 pin chinese moisture meter.

And the tomato plants and fig trees seem pretty happy too.

Since I had plants in the greenhouse this summer, I added a second cheap box fan to insure the plants didn't overheat. It worked, the plants never overheated. But it was also not as hot and steamy as last year with just one fan. The wood still seems to be drying nicely and next year I'm going back to one fan and see if the plants tolerate the additional heat ok. I'm sure there is some optimum ventilation rate that balances top temperature with rapid moisture removal.

Very well done!
The Solar Kiln (display box) gets the same results. Last time though I ran some larger splits than I usually do, just to see the results. Mid-High 20's in a month. This from a Red Oak I just took down the week previous.

If you have a decent sized gram scale (bought mine online for $15), try weighing a piece and compare your MR to the scale shown here.
http://www.engineeringtoolbox.com/weigt-wood-d_821.html

 

[Poindexter]

I dunno how many times I have read this thread and followed the links, but it's a lot.

I sent pencil sketches off to a local engineer today, I am going for a passive unit that doesn't need a fan. I hope to have good results about a year from now...

Thanks for the inspirational ground work.

 

[3fordasho]

I've been stacking wood on pallets to about 5.5' high and then wrapping with stretch netting. Holds it together well enough to move with the bobcat.
Last night I tried a little different version with stretch film, then netting (in case the sunlight degrades the film) and then a short scrap of 5" duct for a vent on top.

 

[Poindexter]

I've been stacking wood on pallets to about 5.5' high and then wrapping with stretch netting. Holds it together well enough to move with the bobcat.
Last night I tried a little different version with stretch film, then netting (in case the sunlight degrades the film) and then a short scrap of 5" duct for a vent on top.View attachment 164492

That will probably work pretty good for ya. Did you close the bottom, or have you got the pallet sitting on something that doesn't let groundwater through?

 

[solarguy2003]

I'm not sure I ever mentioned, the long axis of the greenhouse runs east/west for optimal exposure to the sun. It's not an absolute requirement, as greenhouses still work when the long axis is north/south, just not as much heat input.

 

[renewablejohn]

Bump, any updates on how long it is taking you to season fresh split wood down to below 20%?

Apologise if this bump was for me but I thought I had already answered the question at post 66. Anyway to repeat if you missed it it takes approx 3 months in summer for green wood 50-60% MC to be below 20% MC and approx 6 months over the winter period.

 

[renewablejohn]

I'm not sure I ever mentioned, the long axis of the greenhouse runs east/west for optimal exposure to the sun. It's not an absolute requirement, as greenhouses still work when the long axis is north/south, just not as much heat input.

I am actually on a very windy hill top site the prevailing wind is West to East so the spine of our tunnels are North to South allowing the prevailing wind to flow over the tunnels like an aircraft wing.

 

[solarguy2003]

Apologise if this bump was for me but I thought I had already answered the question at post 66. Anyway to repeat if you missed it it takes approx 3 months in summer for green wood 50-60% MC to be below 20% MC and approx 6 months over the winter period.

Yes, just to confirm, lots of the wood is below 20% in 4-6 weeks. Nothing takes longer than 6 months.

I just went out and split a few. The older stuff almost all reads 4-7% on the 4 pin chinese moisture meter. One piece at the old/dry end read 17%. ??? Meh...an outlier. data is data...

The newest stuff reads 16-18%. The newer stuff got split and put in the greenhouse in late september. It is currently being run in a somewhat compromise fashion. I still have tomatoes and fig trees at one end. So the windows are totally blocked, and I'm still watering them both. I get condensation on the plastic most nights.

If I were running it just for the firewood, I would still be opening the windows and turning on the fan on sunny days.

Despite that, it's still awesome.

 

[Rustyreel]

Yes, just to confirm, lots of the wood is below 20% in 4-6 weeks. Nothing takes longer than 6 months.

I just went out and split a few. The older stuff almost all reads 4-7% on the 4 pin chinese moisture meter. One piece at the old/dry end read 17%. ??? Meh...an outlier. data is data...

The newest stuff reads 16-18%. The newer stuff got split and put in the greenhouse in late september. It is currently being run in a somewhat compromise fashion. I still have tomatoes and fig trees at one end. So the windows are totally blocked, and I'm still watering them both. I get condensation on the plastic most nights.

If I were running it just for the firewood, I would still be opening the windows and turning on the fan on sunny days.

Despite that, it's still awesome.[/QUOT
Excellent. How well does it hold up to the snow load? I live in the snow belt along lake superior.

 

[solarguy2003]

The snow hasn't bothered it a bit. I have noticed several commercially available kits for quicky garages and the like, and the snow just trashes them in a heavy year. We get a fair amount of lake effect snow. I occasionally run the snowblower around it (maybe twice last winter) just so the snow has a place to shed better. I'm not sure it was even necessary. The cheap commercial units have a rib every 4 feet, and mine has a rib every 2 feet. Plus a big diagonal brace on every corner. No complaints so far.

 

[drz1050]

The windows in the ends: are they always open, or do you seal them up in cold weather to hold as much heat in as possible?

 

[solarguy2003]

Since I had fig trees and tomatoes, I would close it up any time it dropped below freezing. I got another 6 weeks out of the tomato plants.

Now I just leave it closed up.

Last year (no plants) I left them open and we got a little snow blow in and drift in through the windows.


It's such a treat to park the wheelbarrow outside the door and not have to fart around with tarp and dig stuff out of the snow.

Once we get one more row of firewood inside, we can push the wheelbarrow right inside to load up.

 

[drz1050]

I like this thing a lot, and might try to copy you in the springtime here.. have to just figure out a place to put it first.

What type of wood were your figures based from? Oak? Maple? Pine?

 

[solarguy2003]

It was a mixed lot of everything. I have 7 acres and there's an oil pipeline in my pasture. They replaced it and had to cut down about 80 good sized trees as part of that process. It was all mixed hardwoods, the most common species being maple. After spending a lot of tedious work getting it all in writing that they were to chip everything smaller than one inch (and nothing else), and stack all the logs in a pile in a certain place...I came home to a pile of chipped mulch the size of my house. All of it. I was soooooo mad.

So anyway, they had to replace my hardwood trees/log and brought in a truckload of stuff which turned out to have a little bit of everything. Quite a bit of oak, -pine-, -fir-, some of that stuff that smells like urine when you split it (cottonwood maybe), some shirt that dulled my freshly sharpened chain in two smoking cuts., maple, etc etc etc.

I was so sick of them screwing up, I just told them to go away and stay away.


There...got it off my chest.

 

[neverbilly]

It was a mixed lot of everything. I have 7 acres and there's an oil pipeline in my pasture. They replaced it and had to cut down about 80 good sized trees as part of that process. It was all mixed hardwoods, the most common species being maple. After spending a lot of tedious work getting it all in writing that they were to chip everything smaller than one inch (and nothing else), and stack all the logs in a pile in a certain place...I came home to a pile of chipped mulch the size of my house. All of it. I was soooooo mad.

So anyway, they had to replace my hardwood trees/log and brought in a truckload of stuff which turned out to have a little bit of everything. Quite a bit of oak, -pine-, -fir-, some of that stuff that smells like urine when you split it (cottonwood maybe), some shirt that dulled my freshly sharpened chain in two smoking cuts., maple, etc etc etc.

I was so sick of them screwing up, I just told them to go away and stay away.


There...got it off my chest.

Did your contract provide for 'liquidated damages' in the event of a screwup? Meaning that a dollar amount they would pay, agreed beforehand? Whatever... they should be contractually liable for the screwup. Meaning, they should replace your wood with like kind, or pay you. I know that was disappointing and disheartening. The supervisor is a bonehead.

 

[solarguy2003]

Did your contract provide for 'liquidated damages' in the event of a screwup? Meaning that a dollar amount they would pay, agreed beforehand? Whatever... they should be contractually liable for the screwup. Meaning, they should replace your wood with like kind, or pay you. I know that was disappointing and disheartening. The supervisor is a bonehead.

Yes, I got some extra money out of the deal. That did make me feel somewhat better. I never thought to include a clause that gave me financial remuneration for them pissing me off. And I now have a lifetime supply of mulch, which I can actually use...eventually.

 

[Kristen]

I now have a lifetime supply of mulch, which I can actually use...eventually.

Is the pile generating heat - enough that you could harvest that heat perhaps?

 

[solarguy2003]

Is the pile generating heat - enough that you could harvest that heat perhaps?

Short answer, no. That surprised me.

Longer answer, they put the pile in the wrong place (where I would get stuck driving across the disturbed wet swampy spots). So I made them move it. When they did that, they mixed a bunch of dirt in with it. That's the only reason I can think of that it didn't heat up.

 

[solarguy2003]

Spring update on the solar heated firewood dryer. Still working awesome. Over the winter, I kept everything closed, since we got some snow drifting in through the open windows last winter. We had no snow inside, which is a plus, but the wood didn't stay -as- dry as the previous winter with ventilation. Various pieces measured from 12-16% mc, which is still fine.

I also added a second "window" (a hole that I can open or close) on both ends, so now a door and two "windows" on each end. With two box fans. The additional ventilation was to reduce the daytime highs to make the tomatoes and tomatillos and fig trees happier, not necessarily to make the firewood happier. Next year I'm building a second one for exclusive use by the plants. When we put the fresh green firewood in this year, I'll see what double the ventilation, but at reduced temperatures does.