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Old 11-04-2011, 04:08 PM   #1
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Fresnel lens - cheap solar concentrator

Some time ago, when researching solar power contraptions, I ran across this video:


The video creator has a lot of good info (and more videos) available from their website:

http://greenpowerscience.com/

They also sell some, but I was able to score one for dirt cheap off of Craigslist. I found someone trying to offload a large Mitsubishi projection TV that wasn't working anymore for $25. I just took it apart and preserved the Fresnel lens that's inside.

After framing the lens in wood to keep it rigid, I can tell you that it works great. Much like what you see in the video, it will pretty much make a block of wood catch fire within seconds when placed at the focal point of the beam.

There are a lot of potential applications for the lens. Just a useful tool to have around IMO. Especially given that you can get one pretty cheap if you look around.
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Old 11-04-2011, 05:54 PM   #2
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Grind, grind the ideas go re solving the problem of getting fresh water from seawater...
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Old 11-08-2011, 10:35 AM   #3
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I purchased the business card and 7 X 10 sized lenses for backpacking gear. They weigh minimal amount and I have started with ease, many fires. The 7 X 10 will start a fire in 20 seconds. Weighs 23.6 grams.
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Old 11-08-2011, 10:57 AM   #4
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The large spot type ones like in the video supposedly can achieve enough power at the focal point to melt copper and several other metals.
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Old 11-11-2011, 02:58 PM   #5
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I've seen a rather simple solar power distiller, I'm going to have to make one just for fun (I have springs on my land, so for me it's a non-issue). All it is is a tray (black) with water in it. Over that you make a little triangular box, with the front (sloping) a piece of glass or plastic. Water evaps from the tray, then condenses on the front, drips down into another smaller tray, and that's it. Supposedly the area of say, one sliding glass door will handle one person's needs on average. You insulate the sides and back of the box, of course. In some cases I'd bet you could get rid of the supply tray, and just get water vapor out of the dirt. Where I live putting a tarp over something to keep it dry is often counter-productive due to that effect.
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