Solar Parabolic Trough Charcoal Oven

[Turtle]

Originally Posted by Ganoderma

I am very interested in this project and intend to experiment (the sun is a nice 20-40C year round here). but can someone please explain the math to me. I am, simply, stupid when it comes to math. and what exactly does "^" mean? sorry.

The caret, ^, is read 'raise to the power of', i.e. it denotes exponentiation. For example 4^2 is read 'four raised to the second power', or 'four squared.'

Originally Posted by Ganoderma

How would one get an airtight area and allow for full heat absorbtion. Glass seems good but liek said it will get black.

Large commercial power generation stations using troughs, surround the receiver tube with a Dewar tube. I would be curious myself to know what a glass blower would charge to make them.

Originally Posted by Ganoderma

... this makes me think of those 2 way mirrors you see in loony bins and jails. Could you use a sheet of glass with that see through mirror material? i realise the reflectivity is not great, but would it not still allow lots of heat through? or would it be like putting sunglasses on your trough

Yep; like sunglasses.

[Michaelangelica]

Here is design!
Metta Spencer's weblog: Two New Anti-Global Warming Inventions

[silverslith]

If you can supply your waste as a slurry you could use a heat exchanger setup to process the waste by supercritical gasification. All you need is a 300bar slurry pump.

It'd give you pure fertiliser out the other end and all the hydrocarbons and oxygen become gas to power your house.

Green Gas (SNG) Production by Supercritical Gasification of Biomass, from Energy research Centre of the Netherlands - Business White Papers, Webcasts and Case Studies - BNET.com

[Nitack]

So I know this thread may be totally dead, but I gots me some ideas...

First, I like the trough because it does not require adjustment, but perhaps adjustment is not needed if the design is right... Perhaps developing something that can completely encircle the target is best? maybe something a little larger like a trash can with the reflective materials surrounding it so that at what ever point the sun is at something is reflecting light. This would also present more surface area to absorb sunlight.

My second thought is the use of Magnifying glasses. An array of them, just as large as the surface area of what you are trying to heat, could be set up so that at what ever point the sun is at at least a few of the glasses are focusing the heat.

Finally, what about using the design of the solar furnace? After all, all we need to do is get it hot enough for long enough, if it were set up right that should not be a problem. A solar furnace type design could easily get above 600 degrees for an hour with no adjustment. Put it on a lazy suzan and you can track the sun manually. You could produce a garbage can amount of charcoal easily enough. Heck, even if you just set it up in the morning, and emptied it at night, throughout the day it would for a time get hot enough to do it itself...

Just some thoughts...

Also, what about a Fresnel lens? The things can melt asphalt, couldn't we get it a little less focused an heat a steel container to 600 degrees?

[freeztar]

Originally Posted by Nitack

Also, what about a Fresnel lens? The things can melt asphalt, couldn't we get it a little less focused an heat a steel container to 600 degrees?

When GAHD mentioned using AOL CDs, a fresnel reflector was my first thought.

The question becomes: Would a fresnel reflector dish at 48" produce more heat than Turtle's 48" parabolic trough?

[Nitack]

Much much more. I have been running this down online all day. A 3'x3' (forgive the lack of metric, I am from the USA) Fresnel can heat a 1/2" area to over 2000 F.

Now reduce it down a bit, what if you lined up three smaller ones, capable of heating to 500+ at their focus point each... spread three or four of them along the length of the pipe, make sure to have a one way valve to release steam and gas but otherwise sealed... Now little heat is lost, and the thing is getting intense heat at multiple points. Use a cast iron pipe and you can get multiple sections up to 1000 degrees, the interior should easily get to 500+. The intense heat will cause all of the oxygen to be pushed out or burned up durring a few bouts of combustion and you will have a lot of charcoal. You could even use this method with something like a cast iron stove. I really think it could work, and have ordered a couple Frisnel lenses online to test. Can't find the damn things anywhere local or I would be experimenting with this as soon as I got off of work.

[Turtle]

Originally Posted by Nitack

.... I really think it could work, and have ordered a couple Frisnel lenses online to test. Can't find the damn things anywhere local or I would be experimenting with this as soon as I got off of work.

Sounds like a plan. You might try an RV (Recreational Vehicle) dealer for the Fresnels as they sell them for people to put on their RV backwindows for an enlarged view.

[Nitack]

Originally Posted by freeztar

When GAHD mentioned using AOL CDs, a fresnel reflector was my first thought.

The question becomes: Would a fresnel reflector dish at 48" produce more heat than Turtle's 48" parabolic trough?

Who says you would not be able to use the parabolic at the same time? If you mounted the Frisnel lenses correctly and angled the parabolics right you could use both...

Also, to be considered, they both should have the same energy output for both a 48"^2 parabolic and a 48" squared frisnel... they are both focusing the energy of the sun over that space into one point. Same space = same energy. Although in the end I think the Frisnel will actually have a higher energy output. With the parabolic the pipe shades the relecting mirrors. The parabolic mirrors may be 48"^2, but given the curve, are they actually reflecting 48"^2 of sunlight or less? All the geometry here is frying my brain.

[Nitack]

Originally Posted by Turtle

Sounds like a plan. You might try an RV (Recreational Vehicle) dealer for the Fresnels as they sell them for people to put on their RV backwindows for an enlarged view.

Wouldn't the RV ones be specially designed not to focus heat given the fact that they are out in the sun?

[Turtle]

Originally Posted by Nitack

Wouldn't the RV ones be specially designed not to focus heat given the fact that they are out in the sun?

It's worth going to check out. I wouldn't be surprised if they come with a warning to keep combustibles away on the interior.

PS I'll find a source. Meantime, check out solar forge. >> Solar forge - Wikipedia, the free encyclopedia

PPS I think you can adapt your system to whatever the focal length of the Fresnel you have. Here is a supplier & list of different sizes & focal lengths.

Edmund Optics - Fresnel Lenses