Solar Parabolic Trough Charcoal Oven

[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]

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]

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. :hihi:

 

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]

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]

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. :shrug:

[Nitack]

OK, weather man says i will have at least a few hours of full and clear sun tomorrow! Firing up the lens and going to do my initial tests. It is about time!

 

I will have my camera and will take copious amounts of pictures for you guys.

[freeztar]

Awesome! :shrug:

 

A video I saw on Youtube had a guy who put a sunglass lens over the end of his camcorder to lower the light intensity. You might want to consider similar measures.

 

I also saw another youtube video (can't post a link right now as I'm at work) where the guy used the fresnel lens to power a small stirling engine. He eventually got it working but it would not move from a dead stop, he had to give it an initial push. I think the name was "greenpowerenergy" or something similar.

[freeztar]

Ok, I found some good links on the web:

 

Here's some very encouraging info:

Halfbakery: Home Solar Charcoal Distiller

 

Here's an idea for a solar tracker (make sure to look at the pics):

Halfbakery: sun tracker

[DougF]

pretty cool link I like the sun tracker pictures but I have a concern about the position of the gears IE: being right in the focal point, but with some modifications this concept should work, Question: what dia. pot are you planing on using. due to the fact you would want the tracking gear twice the size of your pot IMHO.

 

 

 

 

xaviergisz's photos. Get free image hosting at ImageCave.com - free image hosting at ImageCave.com

[freeztar]

pretty cool link I like the sun tracker pictures but I have a concern about the position of the gears IE: being right in the focal point, but with some modifications this concept should work, Question: what dia. pot are you planing on using. due to the fact you would want the tracking gear twice the size of your pot IMHO.

 

xaviergisz's photos. Get free image hosting at ImageCave.com - free image hosting at ImageCave.com

 

I'm confused, do you mean pot as in container, or pot as in potentiometer?

[DougF]

freeztar

I'm confused' date=' do you mean pot as in container, or pot as in potentiometer? [/quote']

 

Well Nitack said he was going to use a dutch oven (pot) and the way this tracker is designed to rotate around the focal point and said (pot) is to be placed in said focal point from what I can see there seems to be Little or no room for said (pot). :shrug:

[Nitack]

OK boys, first day of testing has produced good news and bad news. Good news first!

 

I was able to melt a pile of pennies instantly! The zinc melted, the copper got mushy. Means we got up to well past 800 degrees (melting point of zinc), and by how fast the zinc melted I am guessing some where in the low to mid thousands, my oven thermomedter was not up to the task of measuring that bad boy.

 

Bad news, my frame was just not up to the task. Using two independent A-frames left me with a serious lack of stability and the frame collapsed more than once. I also tried to be slick and attach my two legs with a hinge so I could fold the whole thing up for ease of movement, which left it near impossible to keep standing up as well. Revisions are needed, but the concept is solid I am sure now. Changing out the hinges for real brackets and will be using some spare wood to run footers across from one A-frame to the other on each end.

 

Results were that the dutch oven did get past 300 degrees, but I could not keep the light on there long enough to get a good test, bout 20 minutes was the most I could keep it focused. Hopefully I will get some more testing in tomorrow though and can have some positive results by the end of the weekend. Later!

[GREENPOWERSCIENCE]

Hi,

 

I have several years of experience with huge Fresnel lenses and other stuff that the Green energy movement uses. I have the youtube videos mentioned above GREENPOWERSCIENCE Look at photos on my website and you can see how we built stands (same name). If you have any questions, we may have answers that can save you mucho time and I would be happy to share. In regards to Pennies, a spot Fresnel lens will melt a single penny (98% zinc) in 4 seconds and a pile on under a min. One note, in 2006, the federal gov. passed a bill making it illegal to melt currency due to the rising costs of alloys. They fear people will melt and sell as scrap. You can buy zinc ingots from local places. Try and buy small 1 oz. blocks as 1 pound or greater is hard to melt due to the metal loosing heat from its mass. I have melted 2 pounds before from 1 oz. blocks in a crucible using the sun and a lens. Do not set lens at full power or you will burn the zinc and get this nasty crust. I takes a bit longer but you end up with a nice molten pool.

[freeztar]

Greenpowerscience,

I'm curious as to your assessment of how feasible our efforts are to create charcoal using a fresnel. Do you think it is possible to heat a dutch oven to 700 degrees F in order to create charcoal through pyrolysis?

[Nitack]

No go on the dutch oven as of now. I was able to once again heat it up to 300, but not much higher.

 

Part of the problem I think is that the heat is at best coming from the side and not from the bottom. Much more energy has to be put into the equation because of this. Another problem is just having to every ten minutes or so adjust the lens, and compete with clouds. Perhaps it could be made to work using some sort of heat sink. I was considering something like coiling a copper pipe around the dutch oven and filling it with oil or something else that efficiently transfers heat. Another thought was to perhaps bury the dutch oven in the ground up to the lid. dirt is a super insulator and may allow the oven to retain more heat and hit the temperatures we are looking for. Only problem is that once again, heat would be coming from the top.

[GREENPOWERSCIENCE]

One large spot Fresnel lens 30" x 40"or larger would easily convert a small portion in a small oven/pipe 4" or smaller. The problem with Fresnel energy is heat dissipation. Because you are outside any heat captured is lost very quickly. Even a 1-2 mph breeze can cause a fast temperature drop. I am sure you have figured this out by now but insulation and limited wind exposure would help a lot. (I am working on a cheap evacuated tube-container process that can take Fresnel heat), with that, one lens would bake a lot of material.

 

I have heated the bottom of a pot before by bouncing the beam off of a glass mirror. 10 " below the pot. This exposed the mirror to a much weaker focal point preventing the mirror from getting damaged and placing about 90% of the beam energy directly on the bottom of the pot (10% loss due to mirror). This works best as heating the top of a pot or vessel does nothing for what is inside unless it is a liquid with no air space (direct contact). It also allows for top insulation where most heat is lost.

 

I will try and post a youtube video today of several mirrors directing sun into one Fresnel. We discovered that mirrors the same size as the lens produces a beam with 80-90% of the heat as direct sunlight. Nothing special until you add 2 mirrors 160%, 3 mirrors 240% etc. You cannot get all the beams to focus on one spot this way (which you would not want anyway unless you trying to obliterate something), but you can get them very close. I have a video with 6 mirrors and 6 spots which I thick would be close enough to fit on one oven or pipe. NOTE: mirror quality makes a big difference.

 

Trough vs. Fresnel. My personal experience is that Troughs are great for long stretches of water but not so good for higher heat unless you have an optically correct reflector $$$$$$$$$$$$$. Fresnel lenses are cheap in comparison. I will also post a simple way to make a Fresnel reflector. Nothing special and very simple but it woks. Cheaper than a parabolic mirror though not nearly strong (only 400-600 ? F)