Lens to produce parallel light rays

[shapiro]

I need to produce a lens which can produce a focus infinitely far away, effectively producing rays which are parallel to each other. However the tricky bit comes where:
-the light entering the lens comes from random angles (but only into the desired side)
-preferably the design would be scalable (up to 2m*0.5m)
-the height is not an issue (within reason)
-cost is not an issue
-ideally (this is asking for a bit) the light would leave reasonably evenly spread across the 2m * 0.5m base
-mirrors may be used

It doesn't need to be a design (or even a concept), an evaluation on whether such a system is possible. Should it be, I will pursue this further (and ask for more help?) Otherwise I can just drop it.

Thanks in advance

 

[MacGyverS2000]

I can do it with two lenses just using high school physics...

The question is, why?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[shapiro]

The aim is to gather ambient light (which will consist of light from the sun, light refracted in the atmosphere and light which has reflected off the ground (and potentially then the atmosphere)) and then be able to retrofit the lens to a photovoltaic panel. As the light rays will all be parallel, the angle at which they hit the panel may be chosen in order to maximise its efficiency.
How could this be done with school physics? I'm curious, particularly as school is a reasonably recent experience for me.

 

[drawoh]

shapiro,

If you want to collimate light that hits an optical element in a relatively small aperture, you need a negative lens. Since the apeture is small, you will not collect much light.

An alternate approach would be to install a large diffuser, and place your element behind that. Your detector will capture a small percentage of the incident light, but if your diffuser is large, you may wind up being more sensitive.

If you are serious about this, you should be talking to a qualified optical designer.

JHG

 

[IRstuff]

A> Please do not double post. You should have had the moderators move your entire thread here, if that was your desire.

B> Student posting is not allowed

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[MacGyverS2000]

The aim is to gather ambient light (which will consist of light from the sun, light refracted in the atmosphere and light which has reflected off the ground (and potentially then the atmosphere)) and then be able to retrofit the lens to a photovoltaic panel. As the light rays will all be parallel, the angle at which they hit the panel may be chosen in order to maximise its efficiency.
How could this be done with school physics? I'm curious, particularly as school is a reasonably recent experience for me.

Removing all of the extraneous information, the problem is straightforward in nature... collect all possible light and focus it onto a plane. Doesn't matter how it was created, doesn't matter how many bends it took to get to the lens.

The first thing that comes to mind for this is a plane of microlenses molded into the appropriate material. Multiple lens types can be created either by layering panels, or with some creative molding processes, made into a single panel. Nothing complicated in the idea, per se...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[imagitec]

Light from the sun is already collimated (rays parallel to each other).

Light refracted by the atmosphere that would be collected by even a 2m diameter lens would effectively be collimated.

Likewise, light reflected off the ground and then the atmosphere that reaches your lens would effectively be collimated.

Therefore, you don't need a lens. I'm not being facetious, but I don't have any more to go on that what you've said, and it sounds like you're trying to maximize the solar energy collected by a solar panel. You can't do much better than a flat panel (I think Solyandra used a kind of cylindrical collector, which increased the gain because the light passed through more than one surface).

Can you provide more guidance about what you're trying to accomplish?

Rob Campbell, PE

 

[MacGyverS2000]

Light from the sun is already collimated (rays parallel to each other).

Light refracted by the atmosphere that would be collected by even a 2m diameter lens would effectively be collimated.

Likewise, light reflected off the ground and then the atmosphere that reaches your lens would effectively be collimated.

Not that I don't think the OP is barking up the wrong tree, but your statements tingle my spidey-sense.

While light from the sun may be considered collimated by the time it reaches us, those rays are only perpendicular to a fixed-position panel only for a short time period. If the panel is ray angle sensitive, this will not do.

While atmosphere-reflected/refracted light from a specific point in the sky might be considered collimated, one cannot say the same about the light rays coming in from all directions.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[imagitec]

Again, based on the limited information provided, it seems the OP is trying to maximize the energy collected by a solar panel of finite size. Even if you had a magical, 2m hemispherical lens that collimated all the light that entered it, the vast majority of the energy would already be arriving at the solar panel collimated. Capturing and collimating the other light, if practical, would not significantly improve the output.

In my first post, I mentioned Solyandra, but didn't have the right understanding of their technology. Based on this page describing their approach -

http://www.solyndra.com/technology-products/cylindrical-module/

- one of the advantages of their cylindrical module is that it does a better job than a flat panel at collecting diffuse and relfected sunlight. And it seems like a much more practical approach than a lens made of unobtanium. Yet look at the graph - in their own literature - comparing the output of a flat versus cylindrical panel. I wouldn't consider that a slam dunk advantage, especially compared to relatively simple flat panels that are constantly coming down in price and going up in efficiency. It seems the market didn't either.

Rob

Rob Campbell, PE
Imagitec: Imagination - Expertise - Execution
imagitec.net

 

[imagitec]

While light from the sun may be considered collimated by the time it reaches us, those rays are only perpendicular to a fixed-position panel only for a short time period. If the panel is ray angle sensitive, this will not do.

Again, in terms of praticality, it would make much more sense to tilt the panel.

Rob Campbell, PE
Imagitec: Imagination - Expertise - Execution
imagitec.net

 

[MacGyverS2000]

Again, in terms of praticality, it would make much more sense to tilt the panel.

Agreed.




On that same token, a cylindrical panel would only have light rays perpendicular to it along one "slice", with the slice changing as the sun moves across it. Doesn't seem any more efficient than a similar-sized flat panel... the cylindrical panel will be mildly efficient throughout the day, whereas the flat panel will have peak efficiency at only one point in the day. Sounds like they're robbing Peter to pay Paul.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[IRstuff]

The OP has been lurking, but is remaining silent for whatever reason.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[MacGyverS2000]

Maybe hoping we'll give the answer he's looking for?

It's all academic at this point... no pun intended.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[IRstuff]

Or, the deadline for his homework has passed.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[lumenharold]

You can tell as an Admin? He hasn't been logged in since the 2nd. Bummer. Not many optical posts lately.

Harold
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