Solar Parabolic Trough Charcoal Oven

[Nitack]

Originally Posted by freeztar

This is something my friend and I have pondered in depth. We like the simplicity of the aeolipile. I can't seem to find efficiency numbers on it now, but it is quite efficient with super heated steam IIRC.

I also like the super heated steam option, but the corrosion issue was something I was thinking about. Are you familiar with any non-corrosive liquides with a boiling point in the 150-200 range? Trying to increase the efficiency by reducing the amount of energy required to vaporize while negating corrosion. I thought of Methanol and Ethanol. They are both easy enough to come by. Methanol is actually produced in charcoal making. The question is will they corrode the system? I liked a system I read out using just a automobile water pump and an alternator because the parts are already mass produced and produce AC current so it does not have to be converted from DC.

[freeztar]

Originally Posted by Nitack

I also like the super heated steam option, but the corrosion issue was something I was thinking about. Are you familiar with any non-corrosive liquides with a boiling point in the 150-200 range? Trying to increase the efficiency by reducing the amount of energy required to vaporize while negating corrosion. I thought of Methanol and Ethanol. They are both easy enough to come by. Methanol is actually produced in charcoal making. The question is will they corrode the system? I liked a system I read out using just a automobile water pump and an alternator because the parts are already mass produced and produce AC current so it does not have to be converted from DC.

I'm not familiar with the corrossion issues. Perhaps the surface of the container could be coated with something to give it longevity, or maybe sacrificial annodes could be employed.
Perhaps a chemist will happen along and suggest some other methods...

Do you have a link for the water pump/alternator setup? It sounds promising.

[Nitack]

Here is an article on some MIT kids already working on this idea. I like the approach of the girl who wants to use a tesla turbine as opposed to the water pump but having a hard time finding a tesla turbine. If I could construct it the cost would go down considerably.

Technology Review: How To Build a Solar Generator

[Turtle]

Originally Posted by Nitak

We also saw that even though Turtle was able to focus the energy of his parabolic trough, it did not capture enough heat to carbonize his materials. We don't know if it was an issue of energy loss or not enough reflecting area. This will ensure that we can capture enough energy to heat it up to 500+.

We certainly do know. The trough was too small and the receiver needed insulating. Making the trough larger and insulating the receiver would have given me the temps I wanted. While we discussed ways to insulate the receiver tube, the preferred method is a Dewar tube. (using smaller diameter pipe for the receiver would reduce heat loss too and so raise the temp.)

Originally Posted by freeztar

I get the impression that Turtle thinks the area needed to be increased, but I'll let him speak to this.

OK I'll try this again. I was suggesting that a larger volume receiver in the trough is possible because the area of focus is larger. With a larger volume the process may take longer per

Originally Posted by Nitak

Whether you are reflecting the energy using a parabola or concentrating using a lens the amount of energy you start with is absolutely the same per area squared

but you don't have to change out the receiver contents as often.

Originally Posted by Nitak

...Trying to increase the efficiency by reducing the amount of energy required to vaporize while negating corrosion. I thought of Methanol and Ethanol....

Sounds like an invitation to disaster. Commercial solar trough reflectors use a synthetic oil as I recall. >> http://www.nrel.gov/docs/legosti/fy98/22589.pdf

Originally Posted by Freeztar

So it seems possible still[bending tube into parabola], but requires more connection points to be winched down. Now where can I find some cheap wenches...

I would suggest drawing out a full scale parabola on papaer and using it as a pattern to make a wooden form, and then clamp your tubes to the wooden form while you secure it to that shape.

[Turtle]

Originally Posted by Nitack

... I liked a system I read out using just a automobile water pump and an alternator because the parts are already mass produced and produce AC current so it does not have to be converted from DC.

This is a bit misconstrued. Auto alternators are AC generators, but they contain a diode array that delivers DC at around 12 volts. The reason we don't have DC generators in autos anymore is because they increase/decrease their voltage as the engine speeds or slows. In the old days before alternators, driving a night road was a nighmare because as you slowed down, the headlights dimmed making visibility even worse.

But I digress. Here's a link >>Automotive alternator : AC CIRCUITS

[Nitack]

Originally Posted by Turtle

But I digress. Here's a link >>Automotive alternator : AC CIRCUITS

So if I understood that page correctly, and I think I did, the alternator would not work because it requires a power supply in order to create the electromagnet first in order to work. It can not create electricity just by spinning, it must first be hooked up to an electrical source. So instead a permanent magnet generator would be needed and then would have to go through an inverter to be converted to AC power...

Very interesting, although this is all very ahead of where I am at considering I am still waiting on my damn lenses... the waiting explains all my time to be posting.

[freeztar]

Originally Posted by Nitack

So if I understood that page correctly, and I think I did, the alternator would not work because it requires a power supply in order to create the electromagnet first in order to work. It can not create electricity just by spinning, it must first be hooked up to an electrical source. So instead a permanent magnet generator would be needed and then would have to go through an inverter to be converted to AC power...

I could be wrong, but if it is hooked up to a car battery, then everything should be ok. In a car, the battery fires the spark plug which turns the engine. Once the engine is going, it supplies the alternator with power, which charges the battery. I think I have that right...Turtle, can you confirm or deny please?
I'm certainly on shaky ground when talking about cars and especially electricity. Time to do some wiki reading I suppose.

[Nitack]

in that case, it may work in a grid tie in system, but that is a far way down the line from where we are at this moment. Considering I am still waiting for my damn lenses. I still don't know if this will even work for charcoal, which is my main purpose at the moment.

[freeztar]

Originally Posted by Nitack

I still don't know if this will even work for charcoal, which is my main purpose at the moment.

It will work, it's just a matter of tweaking the system until we get the right temperature and heat spread. What size lenses did you order and where did you order them from?

[Nitack]

Originally Posted by freeztar

It will work, it's just a matter of tweaking the system until we get the right temperature and heat spread. What size lenses did you order and where did you order them from?

For preliminary testing I ordered two 70"^2 lenses from <a href="http://kensolar.com/tek9.asp?pg=products&specific=jnnqiml8" target=blank>Ken Solar</a>. I was not going to spend too much on a huge lens before I do my testing. Once the testing is done and a larger lens is needed I am hoping to find one on either ebay or at a junkyard from a rear projection TV. If I can not find one either way then I shell out and go through Edmund Optics. But I think I should be able to find one on ebay easy enough, there are normally a few listed.