video Off the shelf parabolic mirror from a beauty supply cosmetic mirror
This is a high quality second surface long Focal Length parabolic mirror is from the cosmetic section. The greater the "x" magnification factor the mirror has (ex. x4 or x8) the SHORTER THE FOCAL LENGTH. The x-factor does not equal more power for solar. Shorter focal lengths make objects appear larger when used for reflective imaging. The power is 100% determined by the optical quality and the size of the mirror. Concentrated solar "concentrates sunlight" it DOES NOT "amplify sunlight". This is 100% true for page magnifying Fresnel Lenses too. Longer focal lengths allow for greater flexibility of heat away from the mirrors surface. x factors of 4x or 8x are generally too short for reasonable solar applications.
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Denger
says:
Aug 24, 2012. 7:20 AMReply
Impressive demo with the wooden board. It was difficult to tell from the video what was happening with the glass and steel, other than just heating up. Would I be correct in saying that the heat concentration reached the point where lead will melt? That might have been a better example than the steel.
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GREENPOWERSCIENCE (author)
in reply to Aug 25, 2012. 5:42 AMReplyThank you, the metal and glass had too much mass to mirror ratio to melt. This will zap a zinc penny. Not as quickly as a larger mirror or Fresnel Lens but it does work. This demo was also used to illustrate the dangers of leaving shaving/cosmetic mirrors on a counter by a window with the rising or setting sun.
Denger
in reply to Aug 25, 2012. 2:10 PMReply
That makes sense, however to this viewer your objective was unclear. I thought you were trying to demonstrate using a parabolic mirror for various (heating/fire-building/melting) applications. Thanks for the Instructable.
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