Solar Parabolic Trough Charcoal Oven

[freeztar]

Got it.

So what about height to achieve focal point?
I would imagine we do not want to be sticking our hands in front of the lens adjusting the height of the stand where the dutch oven will sit. It seems a lot safer to be able to adjust the height of the lens.

What were your plans for this and do you have any ideas on how your rig can be built to allow height adjustments?

[Nitack]

Well the dutch oven is about six inches tall itself, so my idea was for starters to place it on a couple bricks to get some hight. We don't want the focus directly on the oven, but with a little high the light should be spread enough to be in the right range. Extensive testing will be needed to get exact hight and temperature ratios.

As for adjusting the frame, I considered that. At the moment this is just a cheap way to get a proof of concept using the two by fours. For a more adjustable frame I was thinking of using steel angle iron because it already has evenly graduated holes and it would just be a matter of where you inserted the screws. You could adjust that according to your application.

[freeztar]

Or what about a springed-hinge instead of a brace?
Or you could put peg holes along the sides of the 2x4's and use dowels and a notched rod to hold the A-frame?

Just brainstorming....gotta go now, I'll check back later tonight...

[Nitack]

New A-frame design. Still very simple/cheap to construct, but gives more ability to control the hight of the focal point. Still using two 2x4s because I want the stability that the four inches provides, but now they will be joined up in a flush manner with one overlapping the other. Then I will be attaching an angle iron to each A-frame in the manner of my drawing. Since those already have holes drilled in it gives me perfect adjustment heights. Just move the lens to a higher or lower hole.

Credit goes to Freeztar because his dowel and hole concept gave me the idea.

[freeztar]

That looks like a much better design!
It will probably still require that you hold it when tilted though. Have you thought of a way around this?

Last night, I was waiting for an ebay auction to end on a 48" fresnel that was only 30 minutes from my house. I was very excited about it as it would have been cheap without shipping (it sold for $70). Of course, my internet connection went down 30 minutes before the auction end and is still down AFAIK (I'll find out when I get home in about 30 minutes from now).

But nonetheless, I tread on...unfaltered...

Did you ever find a better thermometer Nitack? If so, where did you get it?

[Nitack]

Originally Posted by freeztar

That looks like a much better design!
It will probably still require that you hold it when tilted though. Have you thought of a way around this?

Because I am now using angle iron it will be very easy to just use a wing nut to tighten it into place.

[freeztar]

Originally Posted by Nitack

Because I am now using angle iron it will be very easy to just use a wing nut to tighten it into place.

Of course!

Then it's about as prefect as we could ask for: cheap, easy, light and portable.

On the thermometer, I did some snooping on ebay and wiki and came to the conclusion that we need either a high-temp cooking thermometer that can be placed inside the dutch oven (DO) amongst yard waste and yield a read-out quickly, or a non-contact IR thermometer that can hopefully read the temp of the char material (lid off) through the ambient heat coming from the DO.

Hopefully we can char and not worry so much about temperature, but eventually it would be beneficial to have an exact method to achieve desired results. I'm obviously very optimistic.

[Nitack]

Originally Posted by freeztar

On the thermometer, I did some snooping on ebay and wiki and came to the conclusion that we need either a high-temp cooking thermometer that can be placed inside the dutch oven (DO) amongst yard waste and yield a read-out quickly, or a non-contact IR thermometer that can hopefully read the temp of the char material (lid off) through the ambient heat coming from the DO.

Hopefully we can char and not worry so much about temperature, but eventually it would be beneficial to have an exact method to achieve desired results. I'm obviously very optimistic.

OK. So I understand the need in any scientific endeavor for accurate measurement. For now, since the immediate goal is to break the 450 F threshold required for charcoal production, I will basically place an oven thermometer rated to go up to 600 F inside the dutch oven, let the light shine down for 20 or so minutes (my approximation of what it will take to get up to or near the required temperature), then unfocus the lense, and pull the lid off to see what the thermometer says. Low tech, but right now I am just trying to confirm proof of concept.

Once I move up to the barrel design we discussed it will be easy to get one of those industrial thermometers that are used to measure a chambers temperature. And those will go well into the range we need.

I am also thinking about a way to make charcoal production a matter of minutes and not hours. My thought was to get back to Turtles pipe method, although I am having trouble figuring out how to continuously feed the pipe with out allowing copious amounts of oxygen in... For that matter, I also don't know how to have the charcoal extracted so that it does not allow oxygen ether.

Perhaps it could be done using a longer pipe and grinding all your organic material into a pulp or dust that is pushed through. you give plenty of buffer room on either end so that either the pulp or the charcoal acts to block the rush of oxygen in... Diagram coming soon.

[Nitack]

Ok, here might be the more efficient refined model. Forgive the basic and non technical nature, but you get the gist. I think Turtle was on the right track originally using a pipe because super-heating a confined space will cause the process to go much faster I think. It is less of a "set it and leave it" design, but much more efficient in output I think would be possible.

[freeztar]

Originally Posted by Nitack

Ok, here might be the more efficient refined model. Forgive the basic and non technical nature, but you get the gist. I think Turtle was on the right track originally using a pipe because super-heating a confined space will cause the process to go much faster I think. It is less of a "set it and leave it" design, but much more efficient in output I think would be possible.

The only issue I see is that the plunger will need to compress and decompress air (assuming that the system is virtually air tight). Perhaps putting some small holes in the top of the feeding chamber would allow enough air to allow the plunger to move freely.