Random thought for a solar kiln

[Crusarius]

So I had a very random thought on my way to work this morning. 

I want to build a solar kiln. 

I started wondering what would happen if I found a 6' diameter culvert pipe, painted it black and put vents and fans on each end of it. Then place it in a very sunny area.

Anybody have any thoughts how that may work? I would expect to be able to get some pretty high temperatures inside

If it doesn't work for drying wood maybe it will work for sterilizing?

[GeneWengert-WoodDoc]

You will get some heating, but the 50% of the pipe not exposed to sunlight will lose a lot of heat and so you will not have much heat for evaporation.  Also, the solar input will be the shadow that the pipe casts.  So the areas that are not getting perpendicularly close to perpendicular sunlight will also have a net lose of energy.

[Southside]

I think it will work great, for catching snakes..

[doc henderson]

could make and underground shooting range/storm shelter.  So if I understand gene correctly, you have to be able to put heat in, and insulate or trap the heat inside.  to sterilize you could use a outdoor wood furnace but would need to insulate.  then the question is, is this the size you want and is it easy to load and unload.  do you have the pipe already?  I respect and relate to wanting to use things you have access too.  Creative Idea.

[Crusarius]

It was more of a curiosity question. I do not have the pipe but I started thinking I could probably get an old decommissioned pipe from the highway garage and fit small loads in it.

I mostly was thinking sterilization tube because of all the horror stories I hear about ppl buying bug infested wood.

This morning I was thinking about it a little more. (I need a shorter drive to work) . But I could put the pipe up in the air and build a firebox and just run the exhaust from the fire box under the main pipe for supplemental heat.

The primary goal was sterilization, but then I got to thinking if I am going to sterilize it why wouldn't I also be able to use it to dry. I do wonder what kind of temperatures I could get in that pipe. Without supplemental heat.

What Gene says makes a ton of sense. anything that is not gaining in direct sun will be losing. That would definitely mess up the efficiency. I guess the trick would be proper orientation so the sun shoots down the length of the pipe.

[doc henderson]

You did say random thoughts.   .  I think it could work. in fact you could orient it at a 45° angle sticking up out of the ground.  the back half could be insulated, the front ( facing the sun)  could be flat black.  If it is galvanized, it would slow the degrade. It would naturally draft like a chimney. but how would you load and unload that bad boy.  If you get free pipe, and have the equipment to handle and move the pipe, then your COO may nix it cause it does not look nice in the yard.     could use sawdust as insulation if you can keep it dry.  I do not think the zinc oxide will get hot enough to give you "fume fever".

[WDH]

If you go the firebox route, and it does not do what you want it to do drying wood, you could always cook a hog in it, or several . 

[Crusarius]

If you go the firebox route, and it does not do what you want it to do drying wood, you could always cook a hog in it, or several .  

The trick is getting my co-workers to come down....  wait what kind of hogs are you talking about?

[Crusarius]

Doc, thats not a bad idea. would not be hard to put it on a swivel stand. Would almost look like a giant cannon.

have it like a teeter totter. hinged in the center, flip it flat to load then rotate it up and allow convection to do its thing. The water would drop to the bottom and warm moist air out the top.

[doc henderson]

could insulate with straw or even sand if you can keep it dry.  A reflector on the back side could warm the back.  If it could move with the sun could be efficient.  so the problem becomes making free stuff work may cost more and not work as well as just building a solar kiln with traditional frame construction.  It is fun to think about, and maybe the next new thing.  I eat bacon.

[Crusarius]

When all else fails I could launch pumpkins out of it in the fall

[Crusarius]

I wonder if ii does not work how much vacuum I could put into a pipe like that and not have it collapse. Would not be hard to turn it into a vacuum kiln.

[WDH]

When all else fails I could launch pumpkins out of it in the fall

Or one of your co-workers . 

[doc henderson]

I am not sure if you have been watching too many, or have not watched enough old James Bond Movies.  The problem with vacuum is getting a pump big enough and sealing leaks in a container that can open and close.  vacuum effectively lowers the boiling point (evaporation) of liquids like water.  so a combo of heat and vacuum would be great.  and maybe a rotating disc on the back side could slice bread.  

[Don P]

Vacuum and a decommissioned pipe, uh-huh
Flue wrapped... hmm this is sounding more like a charcoal retort, which will sterilize the wood.

[doc henderson]

ok, so you need two diameters of pipe to create and inner and outer core (sounds like Austin powers baby) and insulate the gap between with saw dust.  stand it on end and have a rod attached to a round plate on the bottom and wood can be loaded in the top.  use a forced air outside wood furnace to heat the inside and can vent moisture form the circulating air.  when done use a skid steer to pull out the plate or a basket with the wood.  If this works you will have to find a smaller person to imitate your every move and laugh when ever you do.    

[Crusarius]

doc, you crack me up  I already have a mini me. bet I can get him to copy me. He is in that stage.

Don, it'll be fine. What could really go wrong?

By decommissioned pipe I was thinking one that got damaged from the excavator while being moved. not old rotten one.

And from what I understand you would only need 7" of vacuum to lower the boiling point to an effective level.

[doc henderson]

Hey Cru.  (like gru from despicable me)  any vacuum will lower the bp or increase evaporation.  Vacuum just like air pressure can result in violent catastrophic failure.  Also the strength and integrity of the spiral corrugated pipe would be decreased by any bend or deformation of the structure.  Now I just sucked the air out of the room.     I assume you have an old ac refridge vacuum pump to try.  HF sell a vacuum pump that runs on compressed air.  Prob. not 100% duty cycle.  The trouble as eluded to is creating a door that will seal and not collapse under the vacuum if you can generate it.

[Crusarius]

never thought about an old refrigerator for a vacuum pump. Figured I would test the waters with the HF pump. Unless I could find a good price on a different one.

I am hoping with my fab and engineering skills I could make it stay round. 7" of vacuum is not that much. however the surface area it will be acting on is a concern. anywhere there are deformities in the pipe will definitely have to be addressed with additional support. It would be very easy to reinforce.

[Southside]

I think by the time you did all of that you could cobble up a solar kiln and not worry about if it's going to work and just how well it works.

Not to mention eliminating the chance that you end up on a no-fly list along with a line of black SUV's following you everywhere as some satellite picked up a WMD / ICBM being built in your backyard.