h a l f b a k e r yQuis custodiet the custard?
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I have recently read an article about the use of an array of parabolic mirrors to focus sunlight to a single point, this heat then powers a Sterling engine to generate electricity for your home. It's called Helios, but I can't find a good link.
I don't know if this would work or not, but after seeing
how reflective compact disks are I couldn't help but wonder if CD's could be held suspended by their outer rim and heated from underneath at the exact temperature needed to melt the plastic for a specific amount of time to create identical, (cheap) parabolic mirrors for use in the Helios array.
The parabolic mirrors need to track the sun across the sky and I figure that the hole in the CD's center would be as good a spot as any to place the sensor.
A quick question for those who understand optics; if a parabolic mirror reflects sunlight to a single point, would a ring of magnifying glasses focusing light onto a parabolic mirror generate more heat at the focal point than the mirror alone?
how CD's are made and work
http://www.mmsdirec...roducts/cd_how.html
[FarmerJohn, Oct 05 2004, last modified Oct 21 2004]
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I’ve recently heated CD’s in a microwave and an oven for use in art projects. In an oven at around 200 degrees Celsius the disc gets soft, a little wrinkled and stinks up the kitchen, but also 1 mm bubbles develop in the CD ruining the mirror effect. A microwave within 3 seconds causes sparks to crack the mirror surface of the disc into a miniature lightning pattern. |
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They run the risk of snapping. Rather violently, I must say. |
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For a focal point distant from the CD, the amount of curvature needed would be minimal. |
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I'm finding that 1/16 inch deflection gives a focal point 2 foot 3-9/16 inches distant from the CD. Or a 1/32 inch deflection gives a focal point 4 foot 7-1/8 inches distant. |
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[Farmer John] I wonder if the bubbling you describe is blistering caused by heating from above at the same time as beneath.
I like the idea of pulling them from the center to warp their shape, this would let you fiddle with the focal point. I think I'm going to play around with this.
Worst case scenario, I end up with a butt ugly flashlight. |
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As laugh_last said: No curvature needed. A large amount of CDs can be mounted on a structure forming a parabolic concentrator,
resulting in the desired effect.
The CD reflector material is cheap and readily available. But it is not designed to withstand the sun's UV radiation, which is a problem for all plastics.
The costs of the CDs is negligible, but the mounting structure will be somewhat expensive because the CDs are very small for this purpose. |
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In any case: If I build a prototype, i'll consider your advice.
The answer to your "quick question": No. You would loose power while the sun light passes the lenses, and the lenses are more expensive than the mirror (yielding the same concentrator effect). |
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