Author Topic: Random thought, controlled welding with sunlight? (Read 2475 times)

Derek · « **on:** January 15, 2007, 02:18:37 AM »

I have random thoughts a lot of the time. Sometimes they work out in real life, somethimes they dont. Here's a thought I had.....

Solar concentrators, or parabolic dishes use the ability to concentrated a lot of sunlight into a small space. This compression of all of the infra red into a small area creates a great deal of heat if it strikes anything thats not 100% reflective obviously. Unfortunately, the only way to use this energy is to put something right back into the path of the redirected and concentrated light. Esentially, you are just throwing the light back at the sun then.

Would it be possible to evolve such a thing that would combine parabolic dishes and fiber optic technology? If you could direct all of that light into a single fiber optic cable, you could then theoretically point the other end of that fiber optic cable at anything and the same intensity of light would emit from that end. Is this a realistic idea, or would the cable just melt, not transfer infra red, or what?

Norm · « **Reply #1 on:** January 14, 2007, 08:37:25 PM »

I'm not an expert but I think you would simply

melt the end of a fiber optic cable.

( :>) Norm.

nanotech · « **Reply #2 on:** January 14, 2007, 10:49:16 PM »

Having used a fibre optic light for precision soldering (think micro chips), I can tell you that fibre optic does NOT transfer heat in any way shape or form. We were concentrating the light from a 60W light incandescent light bulb down to an area the size of a pencil eraser, but there was absolutely NO heat at all. VERY handy when soldering under a microscope!!

So trying to get the infrared from the sunlight through fibre optic won't work.

Sorry to throw a damper on your idea.

Why not use mirrors (one at the focal point and one off the side) to direct the heat and light where you need it? Angle them at 45 degrees so they point sideways off the solar concentrator, then another to point it down to the work piece.

stop4stuff · « **Reply #3 on:** January 15, 2007, 12:52:27 AM »

Nanotech, solar heat can be transferred with fibre optics see Fibreoptics and sunlight, however as TDU in that discussion points out the ends of the fibre optics 'rapidly melted and charred'.

wooferhound · « **Reply #4 on:** January 15, 2007, 07:54:12 AM »

I work in the entertainment business and frequently use fiber optic effects. Any illuminator that is made to feed fiber cable, has a fan directed to cool the end of the fibers of the cable that is plugged into the lighting fixture.

But I sill wonder . . .

Can you melt metal using a large Parabolic Reflector without the Fiber Optic ?

stop4stuff · « **Reply #5 on:** January 15, 2007, 08:28:26 AM »

apparently so...

see; Frank Lussier's junkyard solar pages

http://www.junkyardsolar.com/page2.html

"I used a old heater core from a car, the heater melted."

Usually car heater cores are aluminium.

nanotech · « **Reply #6 on:** January 15, 2007, 09:00:35 AM »

I guess I should have mentioned that my experience was limited to one type of fibreoptics, huh?

TomW · « **Reply #7 on:** January 15, 2007, 10:31:16 AM »

woof;

I used to have a nice 18"X18" fresnel lense that could burn holes in an aluminum beer can and ignite 2X lumber in less time than it took you to realize it was happening.No idea where that went but haven't seen it in years probably reallocated as my Ex's property after the divorce. It could also get thin iron to get red hot and spall concrete.

Just one of those things I used to play with like dynamite and blasting caps. Luckily still have all my limbs and digits.

Cheers.

TomW

jimjjnn · « **Reply #8 on:** January 15, 2007, 10:53:41 AM »

I used to melt lead for bullet casting in the Summer with the 18"X18" Fresnel.

Couldn't do it in Fall or Winter cause the melting pot would not let lead get up to good pour temp. Aluminum cans are melted to about a 1-2" spot on walkway.

Gordy · « **Reply #9 on:** January 15, 2007, 10:56:42 AM »

I had stray thouhgt a couple years ago, about useing a sun tracking lens array and fiber optic cables for indoor lighting. I did alot of web surfing for info and materials. Several sites used 150 watt + bulbs as the light scorce. They needed to use glass or quarts ( I forget which ) rod, betwenn the light sorce and the end of the optic cable to prevent melting the end of the cable.

Gordy

asheets · « **Reply #10 on:** January 15, 2007, 11:05:37 AM »

Sunlight, unfortunately, has a huge amount of dispersion, but both single-mode and multi-mode fibre optic require low dispersion light (which must come from a laser or a laser LED). A concentrator, by itself, won't fix the dispersion issue -- but a nice ruby rod with a half-silvered end would (but, if you had THAT, you'd be 80% of the way to a real laser and wouldn't have to mess around with fibre optic cable).

Gordy · « **Reply #11 on:** January 15, 2007, 11:06:07 AM »

Tom W,

Do you know any TV repair person's / guy's, I was told if you can find a junk projection TV, the screen you watch is a fresnel lens. Imagin the power of a 50" or larger lens.

Gordy

asheets · « **Reply #12 on:** January 15, 2007, 11:23:15 AM »

Thinking about this a little more, the term you need to look at is "coherency".

Gordy · « **Reply #13 on:** January 15, 2007, 11:52:33 AM »

Nanotech,

Sorry but the redirecting mirrors won't work either, unless maybe you were to do some compicated calculations and designs on the shapes of the reflecting mirrors. Remember that the light comming to the focal point is comming in at all differant angles, so as it hits the first redirecting mirror the light will start difusing. The same as if you just moved a target out away from the focal point. Unless you can find away to restructer the light at the focal point into a tight beam ( laser? ) I don't know much about lasers other than what I read as a kid about the first ruby laser, and that diferent wave lenghts afect different materials. Like the ones used to remove hair will pass through the skin with out damage, but burn the hair folical. Same for tatto removal, age spots, ect. So if you could find and place the proper wave lenght lens/filter at the focal point, then the mirrors or optic cable.

Gordy

stop4stuff · « **Reply #14 on:** January 15, 2007, 02:11:32 PM »

Gordy, I gotta stick up for nanotech now.

Sunlight comes to the earth from an average of 93 million miles away, the light 'rays' hitting the earth can be considered to be almost parallel so a few more meters (or 100s of meters) reflecting the light off a flat mirror to a parabolic dish isn't going to make any difference. The flat mirror (or as many mirrors as needed) can track the sun with the same equipiment as pv panel trackers. The main consideration is the correct offset for each mirror.

There was a project in Mexico (iirc) that used many (100s?) mirrors to reflect sunlight to a 'collecting' tower where the concentrated sunlight heated a block of ceramic material to a few thousand degrees celcius. The heat from the ceramic caused a thermal updraft inside the tower, the moving air ran a turbine providing elecricity... if I can find the link i post it here.

paul

stop4stuff · « **Reply #15 on:** January 16, 2007, 01:29:58 AM »

wow... i didn't find a specific link to the above, but there seems to be a whole load of other info out there under the heading of 'Concentrating Solar Power'

Google search link

http://ec.europa.eu/energy/res/sectors/csp_en.htm

Gordy · « **Reply #16 on:** January 16, 2007, 04:06:38 PM »

Paul,

I had to reread your post 4 times to make sence of it. You have taken what was writen and turned the process backwards. It was to colect sun light with the parabolic dish, then redirect mirrors at the focal point to the work. NOT the other way around. If he was to use an old C band dish, LOOK at one with a carpenter square held out at arms lenght. Line up the (^)corner of the square with the receive, and the edges of the square with the edges of the dish. You will see that it's not 90 degrees but close enough, for my demmo. Cut a peice of paper into a square, then cut it diagonaly to make 2 triangles. Place these 90* corners point to point, one will be light coming off the dish the other will be the projected light path. Now imagine you have a mirror at the focal point tilted to where you want the beam to hit, and move the light path paper to that area. WHAT did you get! A big spread out / unfocused spot.

Gordy

stop4stuff · « **Reply #17 on:** January 16, 2007, 05:39:17 PM »

lol...

sorry Gordy, my bad.

I was thinking logically, and hadn't read nanotech's illogical mirror setup properly.

Gordy you are correct, light reflected from the focal point of a parabolic mirror will diffuse.

paul

badmoonryzn · « **Reply #18 on:** January 16, 2007, 06:53:04 PM »

The Japanese have used fiber to move light into their buildings for years. They have a collector on the roof that tracks and directs the light into the fiber and they have them going to rooms inside the building to light them for free. The cost of the devices were quite high and I figured it might break even in 200 years or so. There are several people using it in the states now too.

badmoon

RP · « **Reply #19 on:** January 16, 2007, 08:33:40 PM »

Unless it's reflected from just past the focal point using a concave mirror similar to the orginal dish. Then you'd have nearly a "beam" of light (for some distance anyway). This would be good for a few seconds anyway until a piece of dust or other imperfection caused the smaller mirror to distort and then melt!

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Author Topic: Random thought, controlled welding with sunlight? (Read 2475 times)