Solar Parabolic Trough Charcoal Oven

[Nitack]

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 :hihi:).

But nonetheless, it needs to be said for those that may be unfamiliar with the capabilities of the technology involved.

I don't know about you, but once my big lens arrives I will be using welding gogles. No way no how I am going to blind myself with this project.

 

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

 

What are you talking about? We are the beginning of the movement! Viva la charcoalers! "Charcoal for the Climate" (CFC, maybe not such a great acronym)? "Charcoal Creation Initiative" (CCI, I could get behind that)? "Charcoal Changing the Climate Back" (CCCB, might be too long for an acronym)? Carbon Capture Through Charcoal (CCTC, eh)?

 

Until my lens comes I have nothing but time to come up with this stuff :hihi:

[DougF]

Make that four as I'm following this thread too,

I was planning to make one along with you but just last week the landlord put the property up for sale :) I guess it will have to wait till I can find a new place.

 

Back to topic.

the design you've worked out seems sound to me and should work nicely.

for the mirror could you use a old satellite dish coated in foil? just thinking.

[Nitack]

Make that four as I'm following this thread too,

I was planning to make one along with you but just last week the landlord put the property up for sale :) I guess it will have to wait till I can find a new place.

First of all Doug I am very happy you are here. More heads mean more solutions.

Back to topic.

the design you've worked out seems sound to me and should work nicely.

for the mirror could you use a old satellite dish coated in foil? just thinking.

 

I like the satellite dish idea because it might cut down on the amount of adjustments we would have to make to the lens angle during production. Its curve might help to naturally turn the light to the right direction as the sun moves. I think we will need something more reflective than aluminum though. Perhaps that stuff that some one suggested earlier in the thread.

[Nitack]

OK, American Science & Surplus: Incredible Stuff at Unbelievable Prices definitely does not get a good review from me. The lens I ordered from them took an ENTIRE WEEK to leave their warehouse. It shipped out last night, when I ordered it almost an exact week prior. It wasn't even a backorder thing, I actual called them and they said it was in their warehouse. I have a feeling that if I had not called it still would not have shipped out.

 

Their price was nice, haven't gotten the lens yet so can't attest to quality, but there service leaves much to be desired.

[Turtle]

... I like the satellite dish idea because it might cut down on the amount of adjustments we would have to make to the lens angle during production. Its curve might help to naturally turn the light to the right direction as the sun moves. ...

 

I don't think that is the case. The reflective parabolic dish is focusing the Sun's rays the same as the Fresnel. While the dish may require less frequent adjustment to maintain high temp at the focus, both setups require regular adjustment of their axis to the Sun for optimum output.

 

There is no advantage using a parabolic mirror vs. a flat mirror in the setup we described, with the Fresnel focsuing the rays and bouncing the beam off a horizontal mirror up to the receiver vessel bottom.

 

I have an idea for a tracking mechanism. :( Get the drive unit off of one of the Meade AutoStar (or similar) telescopes and attach your lens to it instead of the telescope. Potentially expensive, but you might find a used one. Just a thought. :) ;)

[freeztar]

I don't think that is the case. The reflective parabolic dish is focusing the Sun's rays the same as the Fresnel. While the dish may require less frequent adjustment to maintain high temp at the focus, both setups require regular adjustment of their axis to the Sun for optimum output.

 

There is no advantage using a parabolic mirror vs. a flat mirror in the setup we described, with the Fresnel focsuing the rays and bouncing the beam off a horizontal mirror up to the receiver vessel bottom.

 

I concur.

I have an idea for a tracking mechanism. :( Get the drive unit off of one of the Meade AutoStar (or similar) telescopes and attach your lens to it instead of the telescope. Potentially expensive, but you might find a used one. Just a thought. :) ;)

 

That would work probably, but sounds a bit expensive. I had an idea for a track system. Let me draw it up and I'll post it in a few.

[freeztar]

Here we go.

The major problem with this sytem is that the height of the fresnel stand and the coupling joining the fresnel to the stand must be adjustable to accomodate the sun's changing inclination. A crank could be rigged onto the track for moving the stand (something like curtains with rope and pulleys). There is probably a way to have the fresnel angle adjust as it is moved along the track, but I can't picture how right now. Thoughts?

[Nitack]

Sadly enough Freez, your artistic skills are better than mine. You have the right idea, but it would be difficult to impliment I think. First, the track is the hardest part for obvious reason. Also, we would need a tracker hooked up to the lens to change it's angle as well.

 

I have been thinking on this a lot over the past few weeks... wife says I have been talking about solar power and lenses in my sleep! The fresnel will be viable if it is attended, but for something more passive or less labor intensive Turtles parabolic design will end up as the way to go I think. I am still going to construct my Fresnel setup, but after that is demonstrated to be effective I think I am going to attempt to make the turtle setup work as well.

[freeztar]

In other news, I got my package of fresnel lenses the other day and hope to do some experimenting this weekend. This morning I took one out (8"x10") in the sun and burnt a hole through a green leaf in about 15 seconds. Not too bad, but I had hoped for more. I plan on using several at a time to turn up the heat. I bought an oven thermometer so I'll post some temperatures over the weekend. :)

[Nitack]

OH! picked up a dutch oven and oven thermometer today at lunch. Now I just need my lens (supposed to arrive tomorrow), and to build the frame and stand and I am ready to put theory to the test!

[freeztar]

Sadly enough Freez, your artistic skills are better than mine. You have the right idea, but it would be difficult to impliment I think. First, the track is the hardest part for obvious reason.

 

The track could be constructed fairly easily and cheaply using pvc pipe. It can be bolted to the ground, bent along the sun arc, and a slit cut into the top. The stand would sit in the slit and be attached to a ball bearing that would move inside the pipe. Two legs would touch the ground on either side of the pipe with wheels, for support.

Also, we would need a tracker hooked up to the lens to change it's angle as well.

 

Yes, a major challenge...;)

 

I have been thinking on this a lot over the past few weeks... wife says I have been talking about solar power and lenses in my sleep! The fresnel will be viable if it is attended, but for something more passive or less labor intensive Turtles parabolic design will end up as the way to go I think. I am still going to construct my Fresnel setup, but after that is demonstrated to be effective I think I am going to attempt to make the turtle setup work as well.

 

The trough certainly requires a little less maintenance, but you would need a rather large trough to get the temperatures necessary. If a 4 foot trough gets to around 200 degrees, then how big of a trough would we need to get to 700 degrees? :)

[Nitack]

In other news, I got my package of fresnel lenses the other day and hope to do some experimenting this weekend. This morning I took one out (8"x10") in the sun and burnt a hole through a green leaf in about 15 seconds. Not too bad, but I had hoped for more. I plan on using several at a time to turn up the heat. I bought an oven thermometer so I'll post some temperatures over the weekend. :)

 

What is your method for focusing several at once onto the same spot? Just wondering if you are going to use mirrors?

 

!! Just had a thought... What happens when you take light tubes, Light tube - Wikipedia, the free encyclopedia, funnel the light all to point at your point of heat, and at the end are Fresnel lenses? I wonder if you could make a number of these into an actual viable solar furnace... imagine the application potential if you could get a number of these all channelling light to the same spot?

[freeztar]

What is your method for focusing several at once onto the same spot? Just wondering if you are going to use mirrors?

 

I might have to use mirrors, but I'm going to try and angle them slightly to point to the same spot. I will lose some solar energy on the fresnel surface by angling them, but it should still provide an ample amount of additional heat. We will see...

!! Just had a thought... What happens when you take light tubes, Light tube - Wikipedia, the free encyclopedia, funnel the light all to point at your point of heat, and at the end are Fresnel lenses? I wonder if you could make a number of these into an actual viable solar furnace... imagine the application potential if you could get a number of these all channelling light to the same spot?

 

You get the award for the coolest idea of the day. ;)

Upon first thought, it seems that this would work. The question is, how much solar energy actually makes it through the tube?

If the tubes were flexible, then their inputs could track the sun and no mirrors would be needed.

 

Now, where does one find a light tube? :)

[Nitack]

You get the award for the coolest idea of the day. ;)

Upon first thought, it seems that this would work. The question is, how much solar energy actually makes it through the tube?

If the tubes were flexible, then their inputs could track the sun and no mirrors would be needed.

 

Now, where does one find a light tube? :)

 

Light tubes can be found at Home Depot, sold as indoor skylight type options.

 

I do believe they lose some of their energy in the funneling process. However, considering you could funnel the light from a 3'x3' Fresnel into here, and then refocus it at the end by a smaller and closer fresnel, and could do this with MANY tubes, means the energy output could be huge. The only concern at that point would be melting the fresnel lense at the very end. It would not be at the focal point of the larger fresnell, but condensing 3'x3' of light down to 1'x1' or smaller could still be above the tolerance of the acrylic.

[freeztar]

Good points. I plan on testing several lenses in series this weekend, so I'll let you know of any melting problems I encounter. I'm hoping that the unfocused beam from the first lens will not be enough to melt the second in series, but some experimentation will prove it for sure. I have 22 lenses, so I'm not afraid to melt a few in the name of science. :)

[Nitack]

I have 22 lenses, so I'm not afraid to melt a few in the name of science. ;)

 

:) Holly crap, you don't do anything half-a$$ed.

 

I don't know where I read it, but seem to remember something about the heat at which the lenses start losing clarity (not sure about melting) and distortions ruin the focal power is in the high 100's, like around 180.

 

There is a different kind of fresnel that might work well with this application. The ones we are working with the light comes in straight and then is redirected to all intersect at a certain point. There other kind is a defuser, where light comes in straight and is then scattered. the scattering one can be used in reverse though, which is how the rear car things work to provide a larger field of vision. So it will grab light from many angles, and then kick it out down the tube straight... right to our waiting focusing fresnel. Just a thought.

[Turtle]

...

The trough certainly requires a little less maintenance, but you would need a rather large trough to get the temperatures necessary. If a 4 foot trough gets to around 200 degrees, then how big of a trough would we need to get to 700 degrees? ;)

 

I'm thinking in the 12 to 16 foot range using the same uninsulated 4" galvanized pipe receiver as the 4 foot experimental model I built. For the reflector material I would use thin aluminum sheets and polish them by hand with an auto polisher and either rubbing compound or jeweler's rouge. I would make the supports as I did for the experimental model but use plywood and paint it. I would orient the axis of the receiver pipe along an East/West line, and adjust the axis of the parabola to a few degrees below the Sun's daily zenith. If I wanted more capacity, I would make identical modules and hook them end to end. For charcoal production, it would be a load-it-n'-leave-it operation. :)