Solar Parabolic Trough Charcoal Oven

[Michaelangelica]

So,
a confession
I only check into this thread from time to time to see if you are winning or loosing
So are you? (winning or loosing)

[freeztar]

Originally Posted by GREENPOWERSCIENCE

Anyone Try This

I'd like to, but I'm curious about the pressure release valve you describe. Can you describe it in more depth?

[freeztar]

Originally Posted by Michaelangelica

So,
a confession
I only check into this thread from time to time to see if you are winning or loosing
So are you? (winning or loosing)

What do you mean Mic?
In order to be winning or losing, one must be competing, yet that is not happening here.

As far as a progress report, I'm still waiting to build my stand. I've been saving for a circular saw, but keep hitting monetary setbacks. I will definitely post my results when I get some.

[davidgmills]

Having made both a solar furnace many years ago and having made my own charcoal, here is my two cents based on experience.

Way back in the early sixties when I was in the eighth grade I won a science fair by making a solar furnace out of cheap materials, and it worked great. I bought six six- inch concave mirrors and twelve three-inch mirrors and affixed them to a two by two sheet of plywood. I used bent paper clips held to the front of the board by screws to hold the mirrors in place and screws through the back of the board to the backside of the mirror as focusing devices.

This is genuine eighth grade technology.

Did this thing ever get hot! Focal length was approximately 18 inches away and the light was focused on an area about the size of a quarter. On a sunny day, black paper would start to burn in three seconds! White paper in about 30 seconds. In a flask darkened with soot, I could boil water in about two minutes. Not bad for something that probably didn't cost fifteen bucks (1963 dollars) to make.

The problem with the solar oven design is that it will not get hot enough. You need a solar furnace design which concentrates the light on a very small spot. You either need lenses or concave mirrors for the job.

Now here is what many of you seem to be missing since you have not made charcoal. Early on I made several posts about making my own charcoal. I used a two and a half gallon popcorn can with a lid. After a few trials, I figured out the best method. Put a few leaves and twigs in the bottom of the can, light them, get a good fire going, then slowly fill the can up with fist sized lumps of wood. Add the lump sized wood slowly enough to make sure the flames die out, all the while making sure the fire continues to stay smoldering. Put on the lid and allow just enough of a crack to make sure the fire continues to smolder. Two hours later you have charcoal.

In this process, I maybe wasted five percent of my fuel to get the fire started good enough to where it would continue to smolder without completely dying out.

All you need a solar furnace for or a solar oven for is to get the wood hot enough so that it begins the process. Once the process is going, no further heat input is necessary. All the solar oven or solar furnace will really do is be the match that gets the fire started. And a box of matches is probably a lot cheaper than concave mirrors or lenses.

[GREENPOWERSCIENCE]

OH BOY,

You seem to have missed the idea entirely. Anyone can make charcoal with an open flame. Burn wood drop in water. THE POINT of this Forum is "pyrolysis" look it up on Wiki. Charcoal with no oxygen.

[davidgmills]

GreenPowerScience: Are you talking to me? If you are, maybe you have never made charcoal. I have. All charcoal is made with reduced or almost no oxygen. It is oxygen starved by definition. When you make charcoal in a can or drum, you put a lid on it. But no charcoal will be made in a zero oxygen environment. It needs some air to smolder. And it needs a means of driving off water, gas and oils. The water, gas and oil have to go somewhere. You can drive them off and capture them but you still have to drive them off.

[Michaelangelica]

Originally Posted by freeztar

What do you mean Mic?
In order to be winning or losing, one must be competing, yet that is not happening here.

As far as a progress report, I'm still waiting to build my stand. I've been saving for a circular saw, but keep hitting monetary setbacks. I will definitely post my results when I get some.

Sorry,
I am the guy who just bought himself a $3 Chinese saw and a$4 Chinese hammer.
I am interested in your progress as I think the idea is very worth-wile but being a DIY clutz I can't help
But I see applications of the idea, not only in making tera preta charcoal from biomass, but also in saving 3rd world trees (from cooking fires), water desalination and power generation.
I wonder if the "Stoves" list group would have any inspiration?

[freeztar]

I just finished making my stand an hour ago and have the lens in place. Unfortunately it was sunset when I finished, so no testing today. I'll do my first trial on Tuesday if weather permits. It will be late-day sun, but it will just be a trial run anyways...until next weekend.

I also painted two different sized pipes black (similar to Turtle's idea for his parabolic trough). I will load these up with local organic material when I do my testing.

I tried to snap a pic of the lens and stand, but my camera batteries were dead (charging now). It's nothing pretty to look at really, as it's a little lopsided and the wood bows quite a bit, but it works.

[silverslith]

The idea of utilising the energy content of waste or grown biomass that is based on hydrogen oxidation and retaining the carbon for other uses is great. Carbon is the most useful atom for structural purposes and producing only h2o from our storable/transportable energy systems would be terrific. A no-o2 high temp enviroment is needed for this. The solar furnace is a good system to engineer such a device. To maximise the efficiency heat exchangers are necessary to avoid wasting the thermal energy applied to the processed hydrocarbon/carbohydrate mass. The system should extract the heat of the hot charcoal going out and use it to preheat the raw material coming in before the solar section. The fluid circulated as an energy carrier in this loop would preferably be an inert gas. A lower temp system is possible using supercritical h20, ethanol, methanol. Ethanol may be the best one, giving you a system with under 300degC temp for good reduction emphasised, catalysed decomposition, and a liquid working fluid in liquid phase under achievable pressure. You could either store the mainly h2, some ch4 and co gas for later use or drive a turbine. Converted auto turbos would work well with suitable high speed alternator design. The charcoal would come out as a slurry.

[davidgmills]

I don't get it. Apparently posters on this thread do not appreaciate the problem because people apparently have never made charcaol.

I repeat, making charcaol does not take any kind of sustained external heat.

Last weekend, I bought a 30 gallon galvanized trash can with a lid. I needed to get rid of four or five boxes of out-of-date legal files which I usually send to the land fill. I decided to see if I could make charcoal out of these files.

I did and it worked great. It took one match. There was never a flame for more than about 30 seconds before I put it out. (Today I started another trash can full and never had a flame at all. All I did was get the paper smoldering to begin with.

Once it gets smoldering, I put the lid on the can leaving a crack of about an inch. Later I damper it to almost no crack. In fact, last week the can simmered for three days with the lid fully on allowing almost no air for three days. Somehow managed to smolder that long once the trash can got hot (I also added some large rocks to retain some heat). I thought I might have to punch holes in the lid or sides of the can. Even this was not necessary.

All one would need to do is have a method for capturing the water vapor and gas and oils as they burn off. External heat just is not necessary once the wood or paper or biomass starts to smolder. It could be started with a spark from a spark plug or with a magnifying glass.

By the way, the paper made excellent stock and I guess because it was dried out I was able to make a much higher percentage of charcoal than I have been able to do with wood. I probably only lost 40% in volume whereas with wood I usually have about a 70% loss in volume.

The great thing about paper -- no pulverizing problem. I worked this paper charcaol into my garden today and treated about 50 cubic feet of clay with approximately 25 gallons of charcoal. Here in Memphis we have clay very similar to what I have seen of Amazonian clay -- a yellow / tan clay. Made 50 square feet of terra preta a shovel depth (12 inches) deep. Dumped shovels of clay in the trash can, then diced the clay into small chunks with the shovel. The charcaol readily sicks ot the clay. Shoveled the terra preta back in the garden then added new chunks of clay and repeated the process.

Very easy for the family gardener.