Solar Firewood Kiln?

[Ayatollah]

I'd like any opinions on this idea for a home built solar powered wood drier/kiln.

I have some insulated panels that were gleaned from a commercial refrigeration case to make a 13' long x 5' deep x 66" high box that would have a roof made of triple pane glass windows, also gleaned from a commercial refrigeration reach-in cooler. The sun would beat down through the top of the box and through the windows, trapping the heat in, and then I'd have some small 12 volt fans blowing in there powered by a small photovoltaic panel. Add a condensate drip pan that will drain away moisture that condenses on the windows, and I'm thinking that this will cure up the wood a whole bunch faster than normal. The walls on the box would be about 3.5 inches thick. Our summer temps can be in the high 90's to mid 100's, with spring and fall producing 80's.

 

[JHctRednek]

I tried to build a solar kiln super cheap with some pallets, black plastic, a box fan and some clear roofing. I don't know how well it worked but it sounds like yours would work alot better with all that insulation.

Check this out http://www.arboristsite.com/milling-saw-mills/212511.htm

Lots of great info, I tried the Virginia Tech style


Best of luck

 

[woodchuck357]

Having made several solar klins, all tempoary and for lumber, I think

ventilation during the heat cycle(sun shining) will take care of the moisture, solar powered fans used to move air around the stacks of wood should help. Close the vents at night. If you get condensed moisture on the glass panels increase ventilation.

I haven't been lucky enough to find materials as good as yours, but have had best results by making a separate heat panel with black painted corrugated metal roofing in a glass covered insulated box to heat the air then let it flow thru the wood filled box.

Burning brush, leaves or any scrap could also be used to heat air that may be directed to flow thru the wood box.

 

[imagineero]

Just make sure your fans are oriented to take the air out, not push it in. Mount them up as high as possible, all at one end of the box. Put inlets at the opposite end. The fans are there to suck the moisture out. Fresh air will come in by itself as needed, it doesn't need a fan to get in.

The way you stack the wood inside is also important. If there's no room for air to move through it, then it won't dry. Commercial guys heat the space, and use roll in/roll out systems for stacking.

Shaun

 

[mtfallsmikey]

A Homemade Solar Lumber Kiln - Do-It-Yourself - MOTHER EARTH NEWS

 

[Ayatollah]

ventilation during the heat cycle(sun shining) will take care of the moisture, solar powered fans used to move air around the stacks of wood should help. Close the vents at night. If you get condensed moisture on the glass panels increase ventilation.

I haven't been lucky enough to find materials as good as yours, but have had best results by making a separate heat panel with black painted corrugated metal roofing in a glass covered insulated box to heat the air then let it flow thru the wood filled box.

Burning brush, leaves or any scrap could also be used to heat air that may be directed to flow thru the wood box.

Doesn't the ventilation draw in new air and expel it, thereby evacuating your heat with it?. I thought having the moisure drain away would allow me to keep the temperature up by having a more sealed environment

 

[leon]

wood kiln

I'd like any opinions on this idea for a home built solar powered wood drier/kiln.

I have some insulated panels that were gleaned from a commercial refrigeration case to make a 13' long x 5' deep x 66" high box that would have a roof made of triple pane glass windows, also gleaned from a commercial refrigeration reach-in cooler. The sun would beat down through the top of the box and through the windows, trapping the heat in, and then I'd have some small 12 volt fans blowing in there powered by a small photovoltaic panel. Add a condensate drip pan that will drain away moisture that condenses on the windows, and I'm thinking that this will cure up the wood a whole bunch faster than normal. The walls on the box would be about 3.5 inches thick. Our summer temps can be in the high 90's to mid 100's, with spring and fall producing 80's.

Salaam Aleikuum Ayatollah,


The freezer fridge doors are double paned normally and they
will trap both and heat and moisture and you do not want that
so as Bucky Cat would say that Hoovers!!!

You will be better off simply making your frame and purchasing a
household dehumifier for a lot less work and money and making an
opening for the dehumidifier in the end and simply attaching a
garden hose to the bucket and running it at night to save money
on the electricity cost.

 

[woodchuck357]

The air is heated because warm air will hold more water

as the warmed air passes thru the stack of wood moisture is drawn from the wood into the air. Having a closed system that gets warmed would encourage mould and rot, not drying.

 

[leon]

wood kilns

as the warmed air passes thru the stack of wood moisture is drawn from the wood into the air. Having a closed system that gets warmed would encourage mould and rot, not drying.

========================================================

Unfortunately you are mistaken in this regard, dehumidification kilns used to dry very expensive dimensional lumber work in this manner as this is the preferred method of drying expensive hardwoods and it will work for plain firewood as long as the box is sealed. If the firewood was split into thin slabs it would dry even faster as more of the grain is exposed.

 

[zogger]

Your design will work fine. In the greenhouse here, with drop down sides, in the summer at 90 degrees with the fans NOT running,(48 inch fans....) it will peg the thermostat at 120 within *minutes*. I dont know how hot it really gets, just a lot more than 120. Like when the power goes out. You really cant hang out in there long, too dangerous. I can handle about five minutes tops. If there are hotter places in the tropics, my sweaty hat is off to the guys who can live there.

With at least one big fan running, we can keep it a little under 100 in the summer, and that is somewhat tolerable early in the morning. enough to do the chores in there. The plants love it!

I imagine your box will go well over 200 degrees, and the direct PV powered fan, just a modest exhaust one, is perfect, sun up and hot in there, air gets exhausted, night time, less heat, no fan. Not needed then either, it will dry fine during the day.

I think it would work perfect.


edit: I meant thermometer, not thermostat.

 

[woodchuck357]

Sorry, I thought we were talking about drying firewood without spending big

Not expensive exotic lumber.:cool2:

 

[Ayatollah]

Not expensive exotic lumber.:cool2:

I think the principles involved are the same though. and yes, I want to keep it cheap. That's why I'm using materials I would otherwise pay to dump. Got those dual and triple pane windows coming out my ears, and the 12 volt fans came from several bakery cases I trashed out. The 12 foot long drip/drain pan was in a top mounted evap coil from a frozen food case. The walls were the backs and bottoms of a 12 foot freezer also. With any luck I'll only be spending on some nails, screws and associated hardware.

You know, I acquired several heat exchangers from another project I did, and saved them from the scrap yard run because I keep thinking there's the makin's of some sort of wood fired water heater in there somewhere. :msp_smile: But first we have to dry the wood......

 

[Ayatollah]

Salaam Aleikuum Ayatollah,


The freezer fridge doors are double paned normally and they
will trap both and heat and moisture and you do not want that
so as Bucky Cat would say that Hoovers!!!

You will be better off simply making your frame and purchasing a
household dehumifier for a lot less work and money and making an
opening for the dehumidifier in the end and simply attaching a
garden hose to the bucket and running it at night to save money
on the electricity cost.

Half the incentive for doing this at all is making it from stuff you have, get for free, and/or runs for free...or at most runs off of firewood :cool2:
The dehumidifier costs a bit to buy, makes the project beholden to the utility company, and requires an electrical line, which requires a permit, which requires an inspector to come snooping around. 12 volt fans with a solar panel is kinda like...self-contained.

Salaam Aleikuum Ayatollah

Alaykum As-Salaam

 

[Ayatollah]

Your design will work fine. In the greenhouse here, with drop down sides, in the summer at 90 degrees with the fans NOT running,(48 inch fans....) it will peg the thermostat at 120 within *minutes*. I dont know how hot it really gets, just a lot more than 120. Like when the power goes out. You really cant hang out in there long, too dangerous. I can handle about five minutes tops. If there are hotter places in the tropics, my sweaty hat is off to the guys who can live there.

With at least one big fan running, we can keep it a little under 100 in the summer, and that is somewhat tolerable early in the morning. enough to do the chores in there. The plants love it!

I imagine your box will go well over 200 degrees, and the direct PV powered fan, just a modest exhaust one, is perfect, sun up and hot in there, air gets exhausted, night time, less heat, no fan. Not needed then either, it will dry fine during the day.

I think it would work perfect.


edit: I meant thermometer, not thermostat.

I was wondering what temperatures to expect. 200 degrees would be right nice. Should drive the bugs out of the woodwork too. Bricks on the bottom to help retain heat too?

 

[zogger]

I think the principles involved are the same though. and yes, I want to keep it cheap. That's why I'm using materials I would otherwise pay to dump. Got those dual and triple pane windows coming out my ears, and the 12 volt fans came from several bakery cases I trashed out. The 12 foot long drip/drain pan was in a top mounted evap coil from a frozen food case. The walls were the backs and bottoms of a 12 foot freezer also. With any luck I'll only be spending on some nails, screws and associated hardware.

You know, I acquired several heat exchangers from another project I did, and saved them from the scrap yard run because I keep thinking there's the makin's of some sort of wood fired water heater in there somewhere. :msp_smile: But first we have to dry the wood......

Nice project, take lotsa pics!

I was thinking of a similar scrounged materials device, solar hot water heater. Scrounge old fridge, old hot water heater with a steel tank, not the fiberglass ones.. Some glass, like your glass doors.

The fridge (or old chest freezer) is an insulated box, the steel tank goes in there, the whole inside and the tank painted high temp flat black. Glass goes where the door used to be. Angle to aim at the sun. Use it as the preheater for your regular hot water heater, the plumbing should be easy, already there on the tank to screw into. You could do two of them in series, a preheater for this first one, and this pre preheater just has many feet/loops of (whatever might work, copper I guess, maybe some synthetic) pipe in there.

 

[leon]

I was wondering what temperatures to expect. 200 degrees would be right nice. Should drive the bugs out of the woodwork too. Bricks on the bottom to help retain heat too?

Ayatolla,

There is no reason you cannot use a household dehumidifier
and keep it on the down low using an extension cord, a timer and the night rate.

The Debugging temperature is 165-180 degrees for at least 4-8 hours
using forced air drying.


As far a bricks go you want to use firebrick which absorbs more heat and insulates and sheds heat slowly. OH and dont buy the half bricks as they will crack.


Salaam

 

[Gavman]

Wouldn't it be awesome if you could make moonshine from the moisture in drying firewood

 

[zogger]

Wouldn't it be awesome if you could make moonshine from the moisture in drying firewood

I would imagine you could make some decent ethanol product from maple sap. Maple brandy??

Anyway, wood moisture. This is one of those projects I have thought about and not done, but a kiln here with the hot moist exhaust air blowing into the greenhouse in the winter would be slick.

 

[Bushbow]

***"Half the incentive for doing this at all is making it from stuff you have, get for free, and/or runs for free...or at most runs off of firewood
The dehumidifier costs a bit to buy, makes the project beholden to the utility company, and requires an electrical line, which requires a permit, which requires an inspector to come snooping around. 12 volt fans with a solar panel is kinda like...self-contained."***

I love me a project and even more so - a project where I get the materials for free so please keep us posted on the progress with lots of pics. Also, if you don't have one, get a MM so you can post the change in moisture over time.

Now if this is just for fun or to experiment or need based on limited firewood storage space I see the value but realistically it seems like a limited use project when considering the amount of wood needed to heat a home for a typical season. I just do not see the value vs. volume in a kiln and would rather be spending that time cutting, splitting and stacking more wood so that I am 3-4-5yrs ahead of the game and just let Ma Nature do the job.

Regardless, I am totally intrigued and look forward to updates with moisture levels and timelines for said amount of wood.

Have fun.

 

[Ayatollah]

Nice project, take lotsa pics!

I was thinking of a similar scrounged materials device, solar hot water heater. Scrounge old fridge, old hot water heater with a steel tank, not the fiberglass ones.. Some glass, like your glass doors.

The fridge (or old chest freezer) is an insulated box, the steel tank goes in there, the whole inside and the tank painted high temp flat black. Glass goes where the door used to be. Angle to aim at the sun. Use it as the preheater for your regular hot water heater, the plumbing should be easy, already there on the tank to screw into. You could do two of them in series, a preheater for this first one, and this pre preheater just has many feet/loops of (whatever might work, copper I guess, maybe some synthetic) pipe in there.

As I recall, a company called solahart sold a unit like that. It had an upper tank, and lower tube device thereby creating a thermosiphon. That might be a better layout for you. A flat panel collector made from capillary tubes from the freezer section of the old refrig, and a water heater tank above it.
By the way, I know this was a long time ago, but I remember reading that the color elm leaf green was a better collector of heat than was black.