Could I build a giant magnifying glass? (And maybe incorporate it into a steam engine?)

Optics are fun, and so following that logic, scaled up optics should be even more fun. And so this leads us to: How do I build a giant magnifying glass?

The sun has a lot of power, and I want to harness that energy, and try out a few things, including the interesting prospect of using it to power a steam engine. (Heat up something, run water over it, and run the steam through a turbine).

Several methods have come to mind, including: acrylic, freezing some water in specially-shaped bowls, and sandwiching water (which has a slightly higher refractive index than ice) between two parabolic pieces of plastic. I'm personally concentrating on the last one, as it would be more permanent than the ice.

Just thought this up: freezing a lens, and then coating it with something immediately so that it will stay once it melts. What do we have that is clear, dries quickly, and readily available?

Does anybody else have experience with this?

UPDATE: Some relevant links...
An ideal result.
Parabolic mirrors are another possibility, but I'm still more interested in a lens.
Where a lot of this sprang from.
Indices of refraction. Is it Indices or Indexes?

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LuiP2 years ago

This is basically Daryl Holmans Magnifier engine he is trying to sell plans for for $47. He says he guarantees it to work but try and look for back-up to his claims on line and you will find dozens of his own websites touting how good this thing is. He probably gets paid for every click on the site so this is his real money maker, coaxing us to click on his sites looking for verification of how good his engine is before spending the $47. Anyone stupid enough to order his plans and pay $47 for plans that are already available on line is just gravy for him. Thats why he changed the name to magnifier engine from sterling engine. If you are going to research the effectiveness of this system, search sterling engine on line and not magnifier engine.

Qcks5 years ago
I have a question:

Are we trying to make a magnifying glass or are we trying to turn water into steam using solar energy?

IF we're making giant magnifying glasses, you can probably disregard 90% of what I'm about to say.

If you want to turn water into steam, parabolic mirrors coupled with black/dark absorption mediums would work better then magnifying glasses.

Here's why:

A magnifying glass, due to the smooth curve, captures a bunch of light, which gets refocused into a concentrated point.
The concentrated point can be used to heat things up and burn stuff, but any light that gets reflected is wasted.

If you place a black pipe filled with water above a concave mirror, you still have a bunch of light focused on a point, but the light gets 2 chances to heat up the water and thus heat up the pipe.
Further, you could combine this with a convex glass lens on top of the pipe that's ontop of the concave mirror, bringing in more light, and generally increasing the intensity of the heat generated.
abrown75 Qcks5 years ago
That does sound viable and is an extension on a similar idea I posted here:

My question is that while it does absorb more energy from the sun, I am wondering if it is really more efficient to extract useful work that way or through powering steam engines. I don't know the answer to that. Simply making a distinction between the two. Just because it's harnessing more energy from the sun, doesn't necessarily mean it is more efficient in providing useful work. An engineering question I guess.

What I would like to see is an investment website where a few like-minded individuals could get together and build such a thing.
smokeypwns5 years ago
what it sounds like you need is a big fresnel lens which you can get from one of those old projection TVs they will harness enough sun to melt a penny
y not? that zoundz cool
bashers5 years ago
I am developing a large lens to power a turbine.. it can be done.. i hope to join up with turbine manufacture to assist in development as i beleive solar power can be used in this far have you got?
wirkkalaj5 years ago
Hey Carbon. I've been tossing a similar idea around in my head for years. I think you should test the idea out on a small scale first. Large magnifying glasses are hard to come by without a lot of money. I'm hoping to finish a small scale prototype this weekend. I'm using a 6 inch magnifying glass to heat the water in an enclosed system (kind of like a pressure cooker) to steam, and using that steam to push a turbine in hopes of generating any amount of electricity. If the concept works, I'll want to make some alterations and then a larger scale model. In the future I'm hoping the system can be made to work perpetually. I'm thinking that after the steam pushes the turbine, the steam would then enter into some sort of condenser to be turned back into water where it would be heated again to start the process all over again. I'm just glad somebody else out there is thinking of things like this. I figure it can work If I can get the water hot enough. I've built successful solar ovens, but this will be a first.
Jezza Bear10 years ago
I know it is not a lens but my site has this (it was an old Instructable here before I deleted it)Solar Kettle.

I have burnt my fingers with this!

I think I have seen articles on Ice lenses, not very good I am afraid , very difficult to get the curve
carbon (author)  Jezza Bear10 years ago
Is it really that hard to get the right curve? I see it as just a matter of getting the right bowl-shaped thingy to put the water in.
Kiteman carbon10 years ago
It has to be a smooth curve.

I'd be more inclined to try fresnel lenses. You can buy quite large examples, but I have a couple (just over a foot across) that came off old OHPs since my school went digital. I'm just waiting for a lighter, sunny evening to try and set fire to something...
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