This evening on Craigslist I found an ad which stated that someone was giving away a large projection TV for free. I just wrote them hoping that they will hold it for me so I can harvest whatever Fresnel lens may be contained in the thing. Good for solar cooking and concentrating sunlight whether a point lens (hopefully it is!) or a more diffused lens. But either way I ought to be able to focus the lens on a solar panel in order to gain more power. Has anyone here tried this? Now I don't want to ruin or melt my panel mind you!!! One has to be careful with Fresnel lenses because the right (or wrong ones depending on you outlook) will turn metal into a molten mess in a few moments and decimate plastic in seconds. Doesn't matter how much you paid for a padlock because it will drip to the ground quite rapidly when a Fresnel lens concentrates the power of the sun! There is a large amount of energy to be gained out there but to do it without damage when you have the right stuff available is not so easy to figure out. Steam engines could be powered as well as other sorts of engines as long as you didn't melt the metal in any given configuration in the process.

Anyway, as a side note unrelated to Fresnel lenses... has anyone any idea how to convert Americium found in smoke detectors into useable power without turning into the so called 'Radioactive Boy Scout'?

Rolland (Who's favorite books as a child were the Curious George books!)

 

(1) A Fresnel lens will not increase the amount of solar radiation reaching your solar panel (unless the area of the lens is larger than the area of the panel). The amount of solar energy on the panel is directly proportional to the area of the panel and the cosine of the angle of incidence from the sun to the panel.

(2) Don't, for goodness sake, ever mess around with the Americium in smoke detectors. Period. End of discussion.

 

(1) A Fresnel lens will not increase the amount of solar radiation reaching your solar panel. The amount of solar energy on the panel is directly proportional to the area of the panel and the cosine of the angle of incidence from the sun to the panel.

(2) Don't, for goodness sake, ever mess around with the Americium in smoke detectors. Period. End of discussion.

How about using a Fresnel lens only in the evening when the sun has diminished nearly below the horizon? The small panel I have is quite good in the shade and still registers (without a load despite charging a battery) at 16 volts+. In that instance it could be perhaps beneficial? I don't know.

As for Americium, I've got a sample or two in an enclosed compartment wondering what I could perhaps do with the samples. But you did say end of discussion so I'll leave it at that.

 

Three things:

1. Americium is radioactive
   
2. radioactivity is BAD for amateurs, like you and me
   
3. don't play with bad, radioactive things

learn more in wikipedia

 

Three things:

1. Americium is radioactive
   
2. radioactivity is BAD for amateurs, like you and me
   
3. don't play with bad, radioactive things

learn more in wikipedia

I read you. But unlike the pros right here in America or the pros over in Russia some time back or the pros over in Japan (with certain unforeseen earth and weather factors thrown into the mix) I haven't caused a meltdown... yet! Despite the fact that amateurs like you and I are being exposed to much more radioactive stuff caused by professionals at this moment (depending upon what coast you happen to live on) than whatever either of us could pull out of several old smoke detectors. That aside, despite my mostly 'green' experiments in relation to useful power I happen to be very conservative and for whatever it is worth I'm not nearly as radioactive as the so called Commander in Chief who sits in our White House right now. I'd rather Alan Keyes was sitting there but that is an entirely different subject.

 

Take your two Americium sources to a Hazardous Waste Disposal Depot and have them disposed of properly.

 

The power intensity of solar radiation at the equator can be over 1000 watts per square meter.

However a Fresnel lens will focus and concentrate the solar radiation to a greater intensity capable of damaging a photo-voltaic panel.

 

As already noted, a lens is only useful if it has a greater light-gathering area than the PV panel itself. The gain from any lens will be limited to the area ratio, less the losses of having the light pass through a lens. So a lens that is 3 times larger than the PV might, at best, boost panel output nearly 3X.

But there are losses. Several percentage points are lost just passing through the glass. Then there is the problem of geometry - getting all the light that went through the lens onto the panel. Next up is heat; the efficiency of the PV panel degrades with temperature, and of course it can be permanently damaged.

Ever wonder why you never see lenses in commercial solar panel installations? Yeah, that's why. Mirrors are rarely but occasionally used. Less loss, not so inexpensive, and light.

By the way, the fresnel lens in a projection TV is quite small, no more than an inch or two as I recall.

 

Actually they're pretty big..

 

Ah, that's a different technology than I'm familiar with. Thanks.

Are those big panel lenses common in projection TVs? I see those on the curb fairly often. I might grab one next time.

 

Take your two Americium sources to a Hazardous Waste Disposal Depot and have them disposed of properly.

Ok, I'll consider it MrChips. Probably nothing I could do with them anyway armed with little more than curiosity coupled with my limited knowledge.

 

Actually they're pretty big..

I've seen this video before. Great introduction in relation to what certain Fresnel lenses can and can't do!

 

Ah, that's a different technology than I'm familiar with. Thanks.

Are those big panel lenses common in projection TVs? I see those on the curb fairly often. I might grab one next time.

I got mine form one. The screen is 3 layers of different types of lenses , one fresnel, one cloudy, and the last is clear. All are some sort of plastic. The projector guns have some good magnifying lenses on them as well.

 

Three things:

1. Americium is radioactive
   
2. radioactivity is BAD for amateurs, like you and me
   
3. don't play with bad, radioactive things

learn more in wikipedia

should i not grind my thoriated tungtens? the radiation (alpha + gamma) from smoke detectors is considered about zero, and is far below background radiation. granted, i dont see a reason to mess with the stuff w/o good reason, but i dont see any danger from one smoke detector. pile up a few million detectors that have this stuff and then maybe should wear a dose ring or something.

 

an alpha emitter will cause no harm. the radiation is to weak to penetrate a sheet of paper. If a small amount gets into your lungs or enters the body through a cut, it will cause horrible cell and DNA damage. There is no safe way for a hobbiest to handle the stuff. You won't know you have been exposed until the cancer is bad enough to send you to a doctor.

 

should i not grind my thoriated tungtens? the radiation (alpha + gamma) from smoke detectors is considered about zero, and is far below background radiation. granted, i dont see a reason to mess with the stuff w/o good reason, but i dont see any danger from one smoke detector. pile up a few million detectors that have this stuff and then maybe should wear a dose ring or something.

You may be right and maybe I exaggerated a bit... I'm just worried that a case like this one might repeat itself...

 

I think these posts are getting crossed up

 

"Anyway, as a side note unrelated to Fresnel lenses... has anyone any idea how to convert Americium found in smoke detectors into useable power without turning into the so called 'Radioactive Boy Scout'?"

Taking a Watt as a useable amount of power; you'd have to extract the material from 31 million smoke detectors to get a watt of power, according to Wikipedia's numbers:

... a common type of smoke detector uses 241Am
The amount of americium in a typical new smoke detector is 1 microcurie (37 kBq) or 0.28 microgram.
power yield is 114.7 mW/g for 241Am
114.7 mW/g * 0.00000028 g = 0.000032116 mW, which is 0.000000032116 Watts per detector

Inverting that number, the number of detectors needed to produce one Watt: 31,137,128.

 

Can't you just burn ants like a "normal" person? ;-)

 

Can't you just burn ants like a "normal" person? ;-)

Define normal! LOL! But that being said I'd never intentionally burn ants because they are just trying to live like the rest of us in the struggle for survival, despite the fact that they can be annoying at times. We probably annoy the hell out of them as well from time to time. Don't get me wrong. I'm not one of those green guys with a tax agenda hidden behind the scenes like Al Gore! I still believe in the freedoms our founders set forth in documents people nowadays considered 'antiquated'.

But anyway, the sun was shining quite bright yesterday and I remembered that I had purchased several book magnifiers (fresnel lenses) from a dollar store some time back and decided to test one out in order to figure out whether it would be a good spot lens or a more diffused lens. Turns out that for a dollar you can buy a decent (albeit small scale) spot lens and when I placed a piece of wood beneath it... well, within 20 seconds or so I had flame and coals!