Solar Parabolic Trough Charcoal Oven

[Turtle]

Originally Posted by Nitack

...
For the actual design of the cooker I am still planning on utilizing the fresnel lens because I think there is merit to focused high energy and how much will actually make it into the chamber. My initial tests will use a cast iron dutch oven. It makes sense and is a very easy and readily available option.

Sounds good. I think you can gain some control over the temperature by moving the pot in or out of the focal plane. For example, if you have a focal length of 18" and the cross section of the 'beam' is 1" at that distance, if you move the pot closer you can increase the cross section and so distribute the beam over a larger area at a lower temp. Since you need only about 500º-600º F to make bio-char, I see no great advantage in heating the pot to 1000ºF+ at one small area. Does this make sense to you?

Originally Posted by Nitak

Eventually I would like to make larger batches though as well as capture the bio-oil condensate for use as a fuel source on non-sunny days when my fresnel will not work. Here is what I have so far.

connect a copper coil to one of the holes on top (seal the other one or create a release valve for the initial steam into the air), and have that lead to a second barrel for the collection of the bio-oil. The idea is to be able to produce charcoal while capturing the oil. Thoughts? Better designs? will this even work??

Mmmm...I have not heard/seen anyone say you can get an 'oil' from this process? The wood gas as I understood it is a 'gas', not a liquid. Do you have a source about collecting an oil?

[Nitack]

Originally Posted by Turtle

Mmmm...I have not heard/seen anyone say you can get an 'oil' from this process? The wood gas as I understood it is a 'gas', not a liquid. Do you have a source about collecting an oil?

Grow Your Own Oil, U.S.
http://www.nh.gov/oep/programs/energ...tyanalysis.pdf
ScienceDaily: Researchers Convert Farm Waste To Bio-oil

I think all three of these specifically talk about the "fast pyrolysis" process, as opposed to just plain pyrolysis we are doing, which is optimized for fluid or "bio-oil" output, but the byproduct is present in any charcoal production, just at differing degrees of concentration. While the process is happening it is in gaseous form because of the heat but will condense to liquid form at more normal temperatures.

The liquid actually has many components including some valuable ones if you can separate them out. Such as Acetic acid. But the Methanol, or wood alcohol, is liquid at room temperature and up to 68 degrees celceus, some where around 160 F.

"Wood Gas" is the name for the Carbon Monoxide, Hydrogen and Methane combination that is released by the process.

[Turtle]

Originally Posted by Nitack

Grow Your Own Oil, U.S.
http://www.nh.gov/oep/programs/energ...tyanalysis.pdf
ScienceDaily: Researchers Convert Farm Waste To Bio-oil

I think all three of these specifically talk about the "fast pyrolysis" process, as opposed to just plain pyrolysis we are doing, which is optimized for fluid or "bio-oil" output, but the byproduct is present in any charcoal production, just at differing degrees of concentration. While the process is happening it is in gaseous form because of the heat but will condense to liquid form at more normal temperatures.

The liquid actually has many components including some valuable ones if you can separate them out. Such as Acetic acid. But the Methanol, or wood alcohol, is liquid at room temperature and up to 68 degrees celceus, some where around 160 F.

"Wood Gas" is the name for the Carbon Monoxide, Hydrogen and Methane combination that is released by the process.

Sweet! I had completely missed that aspect. So copper coils...check. If you immerse your condensing coil in water you will need less pipe.

[Nitack]

Originally Posted by Turtle

Sweet! I had completely missed that aspect. So copper coils...check. If you immerse your condensing coil in water you will need less pipe.

Condensing coil in water will work for the process, having trouble with the visuals though (visual person) on how to do that and still have gravity drop the condensed material into my storage barrel.

Put the coil through the bottom of a bucket and then use bathroom caulk to seal it and fill bucket with water?

[Turtle]

Originally Posted by Nitack

Condensing coil in water will work for the process, having trouble with the visuals though (visual person) on how to do that and still have gravity drop the condensed material into my storage barrel.

Put the coil through the bottom of a bucket and then use bathroom caulk to seal it and fill bucket with water?

No need for a hole in the bucket; just partially submerge the coils in an open container of water. The condensate will come out on its own and/or settle in the coils. When the run is over and the system cools you can pour out whatever remains in the coil.

[Nitack]

I love the smiley face on the sun, nice touch.

[Turtle]

Originally Posted by Nitack

I love the smiley face on the sun, nice touch.

Danke schön. What now comes to mind is that the lens as I drew it is roughly the angle it needs to take and that this puts the focus on the top of the vessel. Perhaps we need a mirror below the pot and bounce the beam off to heat the pot's bottom? Freezter gave a link a while back to a large experimental solar oven and it described the use of heliostats -moveable mirrors - to bounce the sunlight onto the parabolic reflector. In your case, as the lens is moved to track the Sun the beam is focused on the mirror & then bounced to the receiver(pot)?

[Nitack]

The mirror was an inevitable addition to the setup that I have been thinking about a lot. Heat from the top down is obviously not efficient nor effective. I have run through a few scenarios using fluid radiator setups or putting rods of radiating metal straight through the container, but a mirror is the most likely candidate. My dilemma is how to reflect that light with out melting the material I am using, or in the case of a conventional household mirror, not having the glass crack and melt on me. These suckers can melt glass. I suppose if I chose the right distance before the focal point it would work.

One thought I had involved tipping the barrel at a 45 degree angle, using a mirror to hit the bottom, and piping all the exhaust gas and fumes through a pipe that let out right at the point where the light hit the barrel so that it would ignite the exhaust gas and provide additional heat. Thoughts?

YouTube - Broadcast Yourself.

[Turtle]

Originally Posted by Nitack

The mirror was an inevitable addition to the setup that I have been thinking about a lot. Heat from the top down is obviously not efficient nor effective.
... My dilemma is how to reflect that light with out melting the material I am using, or in the case of a conventional household mirror, not having the glass crack and melt on me. These suckers can melt glass. I suppose if I chose the right distance before the focal point it would work.

Yes, I think so. Same idea as I described above, that is the temp is lower the more out of focus you put the receiver or mirror.

Originally Posted by Nitak

One thought I had involved tipping the barrel at a 45 degree angle, using a mirror to hit the bottom, and piping all the exhaust gas and fumes through a pipe that let out right at the point where the light hit the barrel so that it would ignite the exhaust gas and provide additional heat. Thoughts?

YouTube - Broadcast Yourself.

I simply don't have the practical experience to say anything critical on the barrel idea. I would like to see a patent drawing or some-such of the wood-gas generators actually used in automobiles. Seen any of those? No need to reinvent something if we don't need to. We then just substitute the lens setup heatsource for the charcoal fire. I have a small Fresnel pocket magnifier I carry; I'm off to melt something with it.

[freeztar]

Originally Posted by Nitack

The mirror was an inevitable addition to the setup that I have been thinking about a lot. Heat from the top down is obviously not efficient nor effective. I have run through a few scenarios using fluid radiator setups or putting rods of radiating metal straight through the container, but a mirror is the most likely candidate. My dilemma is how to reflect that light with out melting the material I am using, or in the case of a conventional household mirror, not having the glass crack and melt on me. These suckers can melt glass. I suppose if I chose the right distance before the focal point it would work.

Here's some good info on mirrors:

Originally Posted by wiki

Telescopes and other precision instruments use front silvered or first surface mirrors, where the reflecting surface is placed on the front (or first) surface of the glass (this eliminates reflection from glass surface ordinary back mirrors have). Some of them use silver, but most are aluminum, which is more reflective at short wavelengths than silver. All of these coatings are easily damaged and require special handling. They reflect 90% to 95% of the incident light when new. The coatings are typically applied by vacuum deposition. A protective overcoat is usually applied before the mirror is removed from the vacuum, because the coating otherwise begins to corrode as soon as it is exposed to oxygen and humidity in the air. Front silvered mirrors have to be resurfaced occasionally to keep their quality.
...
For scientific optical work, dielectric mirrors are often used. These are glass (or sometimes other material) substrates on which one or more layers of dielectric material are deposited, to form an optical coating. By careful choice of the type and thickness of the dielectric layers, the range of wavelengths and amount of light reflected from the mirror can be specified. The best mirrors of this type can reflect >99.999% of the light (in a narrow range of wavelengths) which is incident on the mirror. Such mirrors are often used in lasers.

Mirror - Wikipedia, the free encyclopedia

The ideal mirror for this type of application should be extremely reflective. Any absorbing of heat is a temperature raise in the glass/mirror. But at low heat (with an unfocused 4' fresnel) any conventional mirror should suffice. Of course, it would be nice to use a dielectric mirror.

Originally Posted by Nitack

One thought I had involved tipping the barrel at a 45 degree angle, using a mirror to hit the bottom, and piping all the exhaust gas and fumes through a pipe that let out right at the point where the light hit the barrel so that it would ignite the exhaust gas and provide additional heat. Thoughts?

That's a possibility, but I prefer the mirror idea. If the bottom of the barrel can be heated (barrel perpendicular) with a mirror, then the heat will rise up through the rest of the material, all the way to the top. At 45 degrees, the topside surface area is much larger and more heat will be lost. This may not matter though, given the range of possible temperatures we are predicting. In that case, design the container around your distilling.

YouTube - Broadcast Yourself.

Cool!
I was watching those over the past weekend, with the same search term.
One thing that comes to mind while watching the vids at utube is safety. We should consider creating a "safety protocol" for handling these potentially dangerous apparatuses. For instance, tinted safety goggles should be a requirement for any experimenting done with fresnel lenses. I also think it's wise to keep fire retardant nearby on every occasion. If we do manage to delve into electricity generation, then more fail-safes are needed. I'm not directing this at anybody in particular (I'm not trying to be Mr. Mom ).
But nonetheless, it needs to be said for those that may be unfamiliar with the capabilities of the technology involved.

Of course, it seems to be just us three, so no impending liability concerns forseeable...