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  • Can an OHP's Fresnel lens be used to concentrate Solar Power ?

    Discussion in 'The main mechanical design forum' started by srijith, Mar 15, 2012.

    1. srijith

      srijith Member

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      Can an OHP's Fresnel lens be used to concentrate Solar Power ? If so, can this power be used to run a (brass-cylinder) sterling engine?

      Has anyone used an OHP's lens before for a similar purpose ?

      What happens if a second OHP-Fresnel lens is brought into the path of light, does the intensity increase?

      And what if I use a convex lens in between two Fresnel lenses, can that help?
       
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    3. Dana

      Dana Well-Known Member

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      What is an OHP?

      Certainly a Fresnel lens can be used to concentrate solar power, and running a Stirling (not sterling) engine is a good application for solar power.

      Adding additional lenses won't add any additional intensity; the power available is a function of the area of the largest lens that the light hits first. Additional lenses may be useful to change the focal length of the system or the light distribution, or possibly to concentrate the available energy into a higher intensity over a smaller area, but they won't add energy.
       
    4. srijith

      srijith Member

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      By OHP I meant Over Head Projector. OHPs also use these Fresnel lenses. Thanks for the info. and your time. :)
       
    5. Dana

      Dana Well-Known Member

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      Ah, gotcha. Good idea... with computer projectors becoming ubiquitous nowadays, there are probably a lot of OHP's being thrown away, available for parts.
       
    6. srijith

      srijith Member

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      Thats exactly what I am trying to do. So far, its pretty much a failure. :(
       
    7. Dana

      Dana Well-Known Member

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      Hmmm... I'm not familiar with the optics of an OHP, never having considered it. Are you sure that the Fresnel lens is equivalent to a simple convex lens? That's what you need to concentrate sunlight, but an OHP with a tubular bulb would [I think] use a cylindrical Fresnel lens to collimate the light... if you tried to use such a lens to focus sunlight it would focus it into a line, not a point. The Fresnel may not even be a simple cylindrical reflector; it could instead be specially designed to work with whatever shaped reflector is around the bulb.

      The focusing lens on the top of the projector will indeed be a simple complex lens, but of course it's a lot smaller.
       
    8. srijith

      srijith Member

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      Yes the fresnel lens is equivalent to a simple convex lens, checked it out. And both the simple convex lens and the fresnel lens focus light into a point, not a line.
       
    9. Dana

      Dana Well-Known Member

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      So you said "it's pretty much a failure"; what exactly is happening?
       
    10. srijith

      srijith Member

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      Unable to generate enough heat to expand the gas in the cylinder. Am stuck at that, there are no fresnel lens manufacturers in India or they don't manufacture the size I want. :|
       
    11. Dana

      Dana Well-Known Member

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      Perhaps a parabolic mirror instead of a lens?
       

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