EDUC Something for the BoB? Ultimate in solar power - Fresnel lens hot enough to make lava

[Aardaerimus]

Videos demonstrating the insane and accessible power of the sun - melting stone into lava, liquifying obsidian, easily melting steel and other metals.

The heating applications are nearly limitless.

You can start a wood fire nearly instantly, rapidly boil water for desalination, purification, or pressure where applicable.
You can smelt, cut, or work metal off-grid. You can cook food, melt sand into glass, melt down bottle glass, or just make super awesome artwork.
You can generate electricity with various engines (sterling, steam, etc).

I think that this would be awesome off-grid or in a survival situation.

 

[Witness]

That was interesting, thank you.

 

[sierra don]

Did not know that big screen TV's used fresnel lenses.......


A quick demonstration of the difference between a Spot Lens and a Linear Lens, both of which are used in big screen TVs. The punchline being spot lenses can do everything that a linear lens can, and much more. Much higher temperatures achieved with a spot lens.

http://www.youtube.com/watch?v=xExXjXm0YV0

 

[Dennis Olson]

They don't anymore. I think that was the old projection tv's.

 

[Richard]

why hasn't it amounted to some practical application then?

 

[tanstaafl]

There should be a warning label on Fresnel lenses that reads: "If you are a moron, do NOT play with this! We're not kidding ... just DON'T!"

 

[tanstaafl]

Forgot I had this in my wallet. I'm more of a fan of the tiny free-floating compass than the Fresnel lens, but the point is that there ARE products out there that already include a Fresnel lens.

 

[tanstaafl]

And a third comment ... I once was sorely tempted by an eBay auction for something very much like the OP picture. The auction text said the seller literally vaporized zinc pennies with it (not melted ... VAPORIZED). Which brings us back to my warning about how morons and Fresnel lens should NOT be mixed together.

 

[AzProtector]

They're pretty cool.
I'm doing an experiment this winter.
Build a small shed like structure, put a couple on each side focused on rock and dirt underneath it...the focus would be about 6 inches into the dirt/rock.

The idea is to heat the rock and dirt, and keep the "shed" warm.
It's a proof of concept kind of thing.
If it burns down, well, it's in the field waaaaaaay over there.

 

[tanstaafl]

Okay, fine, a FOURTH comment: On an Ebola-related thread there was talk about burning bodies that had died of Ebola (or any plague, really). I posted this from Wikipedia:

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Per Wikipedia, since presumably you'd want to "burn a body completely" if it had any kind of plague: "A traditional Hindu funeral pyre takes six hours and burns 500–600 kilograms (1,102–1,323 pounds) of wood to burn a body completely." (http://en.wikipedia.org/wiki/Funeral_pyre)

Anyone know what proportion of a cord of wood that amount of wood would be?

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Personally I rather liked the wood/wood/would juxtaposition (although I resisted including a woodchuck), but no one answered my question so I got off my mental backside, did a little research, and found this:

Question: How much does a cord of fire wood weigh?

Answer: Seasoned (dried) oak weighs about 4000 lbs. or two (2) tons.

http://wiki.answers.com/Q/How_much_does_a_cord_of_pinion_wood_weigh

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So I gather that it would take at LEAST 1/4 cord of wood PER BODY to be sure. How much firewood do most people keep around the average urbanized and suburbanized homes? Which brings us in a roundabout way back to Fresnel lenses and the possibility that you could use one or more of the big ones to cook plague bodies. I'm not entirely sure I'd want to hang around while it was happening, but do you suppose it could work?

 

[marymonde]

They don't anymore. I think that was the old projection tv's.

Right. My friend's husband looks for those projection tv's on craigslist. He has several of the lenses and they work like a charm.

 

[Dennis Olson]

Um, this ain't a Turd Whirled country (at least in a non-political sense - heh.) Crematoriums, not freakin firewood.

 

[tanstaafl]

Um, this ain't a Turd Whirled country (at least in a non-political sense - heh.) Crematoriums, not freakin firewood.

The discussion was about what you do on a personal level, not a community or national level. Or at least that was what I was talking about. So unless you have access to your own crematorium then you have to consider other options. I liked the post where someone said they were going to use the "D6 Caterpillar and big hole" approach, and I liked especially when someone else (apparently in all seriousness) replied that you should remember to call before you dig to check for buried utility lines -- I laughed visualizing Vincent Price in "The Last Man On Earth" waiting on the phone for someone to pick up ...

Something else I found on my little foray into researching funeral pyres:

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In the U.S., a group [Crestone End of Life Project] in Crestone, Colorado has done the research, obtained the necessary legal permissions and created a permanent cement pyre structure to perform around 12 “open-air cremations” a year. (Moreno, Ivan (31 January 2011). "Funeral Pyres An Option In Crestone". CBS Denver (Denver). Retrieved 4 May 2011. - http://denver.cbslocal.com/2011/01/31/funeral-pyres-an-option-in-crestone/)

tanstaalf comment: But this service is available only to locals ... no out-of-towners need apply.

 

[Doc1]

A common and inexpensive fresnel lens is the (roughly) 8.5"x11" page magnifiers sold in office supply stores. These are capable of developing tremendous heat for fire starting and metal heating. Folks who use any sort of magnifier for solar collection purposes really should wear eye protection in the form of welders googles for two reasons: The bright, concentrated light can damage your eyes and various items ranging from bits of concrete to metal and stones can pop or explode when exposed to high heat. You really don't want tiny bits of hot shrapnel flying into your eyes...especially in a survival situation!

Best regards
Doc

 

[FarmerJohn]

They're pretty cool.
I'm doing an experiment this winter.
Build a small shed like structure, put a couple on each side focused on rock and dirt underneath it...the focus would be about 6 inches into the dirt/rock.

The idea is to heat the rock and dirt, and keep the "shed" warm.
It's a proof of concept kind of thing.
If it burns down, well, it's in the field waaaaaaay over there.

You get the same amount of heat through ordinary glass but spread out evenly which makes it far simpler to use and not dangerous. Make sure that the sun hits something with high mass like barrels of water painted black and the heat will still be there at night when you need it the most.

Fresnel lenses (or regular convex lenses for that matter) are good at focusing the sun's energy on tiny areas. Tiny, but very dangerous because there's nothing to see until you put something into the hot spot; it had better not be your finger.

 

[meandk0610]

This tip is awesome! We got one of these lenses from my ex, who has a few for looking at his fish tanks (small shrimp) that he designs. We didn't know what they were called and never thought about the survival applications. It's the 8.5x11 size. Cool! I feel some small experiments with DD coming on!

 

[tanstaafl]

It did occur to me that any unattended Fresnel lens had better be equipped with a sun-tracking device, otherwise what you'll have is a mega-hot spot wandering around your target area as the Sun crosses the sky. Considering that the discussion is that these things can melt or burn (or vaporize) many things, a wandering mega-hot spot doesn't sound like a very good idea. I don't see it on the video still above, but the first thing I'd do is be damned sure I had some kind of shield on the Fresnel lens or the frame to block the sunlight.