# Where do you think we'll top out with this lumen thing?



## Dr. Tweedbucket (Oct 3, 2015)

:touche:

It would be cool if we can get to the point where we can start an actual fire with a flashlight beam, but don't know if we'll get that far


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## RickZ (Oct 3, 2015)

Dr. Tweedbucket said:


> :touche:
> 
> It would be cool if we can get to the point where we can start an actual fire with a flashlight beam, but don't know if we'll get that far



No it's been done, incandescent bulbs with 100 watts 2x18650 batteries and a good throwing reflector and you have over 280℉, well enough to light a fire with only 1,500 lumens.


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## RickZ (Oct 3, 2015)

Also, if you take a typical1,000 lumen flashlight LED, and hold it ten feet away, and use a magnifying glass about 5" from some paper, and it should be about 500℉, enough to light most kinds of paper.


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## Dr. Tweedbucket (Oct 3, 2015)

Holy crap!!:sick2:


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## StarHalo (Oct 3, 2015)

What is this "top out" you speak of? It sounds limiting..


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## P_A_S_1 (Oct 3, 2015)

RickZ said:


> Also, if you take a typical1,000 lumen flashlight LED, and hold it ten feet away, and use a magnifying glass about 5" from some paper, and it should be about 500℉, enough to light most kinds of paper.



Wonder how many will try this to see if it works..


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## richbuff (Oct 3, 2015)

I think that the upper limit for lumens for a flashlight with extended battery carrier/8 x 18650 in a size not much bigger than a TK75 will be about 35,000 lumens for the next two years, until new technology appears to get us past that.


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## Str8stroke (Oct 3, 2015)

How can we ever forget this goodness.
http://www.candlepowerforums.com/vb/showthread.php?368370-Fire


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## Illum (Oct 3, 2015)

considering that we have 4x18650 lights that tops out at over 6000 lumens I'm guessing no. lumens will top out only when the batteries necessary to power it for a practical period of time becomes too heavy.


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## MAD777 (Oct 4, 2015)

I think pushing past 20,000 lumens from leds is going to depend on heat management and being able to maintain reliability.


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## drmaxx (Oct 4, 2015)

Let's assume that we can get max. 75W (20 A draw) from one 18650 battery and 100% luminous efficacy then we can get a theoretical 75W *680 L/W = 51000 lumen per battery. Now lets slap some efficiency coefficients on that: Let's go for 10A draw = 50%, 80% for the electrical/electronic system and somewhere around 40% for the luminous efficacy then we end up at 8000 lumen for a flashlight with one 18650 battery. This would be my bet for a small flashlight in 5 years . That's still 25 W of heat to get rid of - but hey it's the future we are talking about.


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## ven (Oct 4, 2015)

MAD777 said:


> I think pushing past 20,000 lumens from leds is going to depend on heat management and being able to maintain reliability.




+1

Vinh has done the 21k in the tk75 which is astonishing..............

The hardest part is the HS side allowing decent run times.........that is the challenge other than HUGE mass..........

As for topping out............never imo, there will always be a demand for higher lumens,regardless of how short run times. As LED's become more advanced,even now with the xhp70 which is good for 5k, what will next year bring........7k or more. Then multi emitters ,potential is there...........just making it actually usable for longer than 30's at a time.

I think 3-4k is the magic number right now for high output and sustainability.........by that i mean for 5-10mins+ in larger lights like the x60 and in cool outdoor conditions the tk75 sized light. After that its cell life, even with 4 or 6 cells inside,sustaining over 4k lumens for much over 1hr is difficult without extra extensions. Well i guess thats not an issue if the higher lumen requirement is needed anyway...........

I thought last year we were getting close or peaking in lumen/output but this year with MKR and xhp70 lights, this has give me greater confidence for next year

I would like to see 4-5000mah 20-30a cells now in 18650 flavour..........maybe a way off on that one though!!!


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## bykfixer (Oct 4, 2015)

It's all about heat and battery.

Not long ago a flip cel phone with enough memory to hold 1500 numbers and a few dozen thumbnail size photos that gave you 2 hours of talk time was a marvelous thing. 

Now a phone with quad core processor, 16gb of ram that gets 4 hours of internet browsing is the norm.
Mainly thanks to battery tech and heat management (through efficiency). 

That's the future imo...the efficiency end. Way more light using the same (or less) power.


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## WalkIntoTheLight (Oct 4, 2015)

RickZ said:


> Also, if you take a typical1,000 lumen flashlight LED, and hold it ten feet away, and use a magnifying glass about 5" from some paper, and it should be about 500℉, enough to light most kinds of paper.



My BS detector went off, so I decided to try it. As expected, it just turns a nice reflector light into one of those cheap optic throwers with the square LED hot spot. Warm to the hand, but less warm than if you just held your hand closer to the flashlight without any magnifying glass.

IIRC, you can't magnify an image to be any hotter than what the surface temperature of the source object is. For example, you can't magnify the sun hotter than 5500C. I don't know what the surface temperature of an LED is, but probably not hot enough to burn paper.


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## Illum (Oct 4, 2015)

WalkIntoTheLight said:


> I don't know what the surface temperature of an LED is, but probably not hot enough to burn paper.



The infrared heat emitted from LEDs is negligible, it might be hot enough to burn paper provided the paper used possesses the ability to absorb ALL of the light produced by the LED, including the wavelengths of the visible spectrum. Because of this difference, LEDs cannot be compared to a 1000 lumen incandescent. 

Though someone from Germany did manage to scorch paper using MCEs and Fresnel...


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## scout24 (Oct 4, 2015)

Data sells a kit for firestarting using his Spy's...  See "Fire" thread in the Cool Fall subforum.


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## bykfixer (Oct 4, 2015)

Lets just discuss 101 ways the kiddys and kooks can start fires with flashlights in this thread, why don't we?


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## SemiMan (Oct 4, 2015)

-----


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## NoNotAgain (Oct 4, 2015)

WalkIntoTheLight said:


> IIRC, you can't magnify an image to be any hotter than what the surface temperature of the source object is. For example, you can't magnify the sun hotter than 5500C. I don't know what the surface temperature of an LED is, but probably not hot enough to burn paper.



Many years ago when I was researching ablative materials, I had samples heated to 6,000F using a solar furnace. The heat generated was almost instantaneous due to the focusing mechanism used.

This solar furnace was located in the Pyrenees mountains in France. I'd hate to have the job cleaning all of the mirrors. 

http://www.pyrenees-cerdagne.com/en/science-and-energy


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## bykfixer (Oct 4, 2015)

SemiMan said:


> LEDs are not processors. One has a hard physical limit, ones does not ... at least not yet.
> 
> What is likely to be the hard limit is optical transmissivity and the heat generated from such ..... magnetic/efield optics aside of course. Even if you get super efficient LEDs, the light has to pass through or reflect off something ... and we are still talking hand-held right?
> 
> ...





My point being that once upon a time (not long ago) a high efficiency 65 lumen incan ran for an hour on a pair of 3 volt batteries in sync. 

Now with a not so modern LED 220 lumens for a couple hours on a single aa is not a big deal...

Yeah I know LED's aren't processors...but who's to say LED is the final technology? 

Once upon a time the vinyl record was replaced with the 700 mb cd...but now the pinky nail sized memory card can do (last time I looked) 32 gb. 

Again...as technology changes there's no telling what's possible.
http://www.zdnet.com/article/goodbye-leds-hello-plastic-bulbs/
Fipels...


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## SemiMan (Oct 4, 2015)

Cause whether LEDs are the final technology or not really does not matter. There is a hard PHYSICAL limit on efficiency. It cannot be broken.


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## bykfixer (Oct 5, 2015)

O...ok


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## scout24 (Oct 5, 2015)

I think part of the equation is not just sheer brute output, but harnessing it into something other than a Mule type beam. Yeah, 7000 lumens of flood is a very useful thing for certain applications, if higher output is only available due to increased die sizes it is of limited use. Either reflector design needs to catch up, or bigger optics like Surefire's TIR system need to be developed. I agree with semiman in spirit, if efficiency were so easy to improve, we would still be enjoying yesterday's small dies with today's outputs... just food for thought.


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## more_vampires (Oct 6, 2015)

WalkIntoTheLight said:


> My BS detector went off, so I decided to try it. As expected, it just turns a nice reflector light into one of those cheap optic throwers with the square LED hot spot. Warm to the hand, but less warm than if you just held your hand closer to the flashlight without any magnifying glass.





WalkIntoTheLight said:


> IIRC, you can't magnify an image to be any hotter than what the surface temperature of the source object is. For example, you can't magnify the sun hotter than 5500C. I don't know what the surface temperature of an LED is, but probably not hot enough to burn paper.


Not quite. If you had a 1500 foot parabolic mirror, that hotspot is going to get quite a bit more than 5500c. With enough area of light concentrated, you can do interesting things.

A 3'x5' fresnel can melt pennies and crack cement with thermal shock techniques.

You're taking the light over an area and throwing into a tiny point.



Illum said:


> The infrared heat emitted from LEDs is negligible, it might be hot enough to burn paper provided the paper used possesses the ability to absorb ALL of the light produced by the LED, including the wavelengths of the visible spectrum. Because of this difference, LEDs cannot be compared to a 1000 lumen incandescent.
> Though someone from Germany did manage to scorch paper using MCEs and Fresnel...


In the above video, he is using "char cloth," a time honored firestarting technique. The process makes it dry and BLACK. Now it absorbs most wavelengths. Regular cloth won't take weak sparks, such as from quartz and pyrite. Those are some of the weakest sparks you can get, yet an expert can still light char cloth with them.

https://en.wikipedia.org/wiki/Char_cloth


> *Char cloth* (also called *charpaper*) is a swatch of fabric made from vegetable fiber (such as linen, cotton or jute) that has been converted via pyrolysis into a slow-burning fuel of very low ignition temperature. It is capable of being ignited by a single spark that can in turn be used to ignite a tinder bundle to start a fire.[1]​[2]​ It is sometimes manufactured at home for use as the initial tinder when cooking or camping and historically usually provided the "tinder" component of a tinderbox. It is often made by putting cloth into an almost airtight tin with a small hole in it, and cooking it in campfire coals until the smoking slows and the cloth is properly charred.
> 
> Charcloth ignites with even the smallest spark, and is therefore commonly used with a flint and steel.



99% of lighting a fire is "doing it right."



Str8stroke said:


> How can we ever forget this goodness.
> http://www.candlepowerforums.com/vb/showthread.php?368370-Fire



Oh yeah, FIRE! http://www.candlepowerforums.com/vb/showthread.php?368370-Fire


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## SemiMan (Oct 6, 2015)

WalkIntoTheLight said:


> IIRC, you can't magnify an image to be any hotter than what the surface temperature of the source object is. For example, you can't magnify the sun hotter than 5500C. I don't know what the surface temperature of an LED is, but probably not hot enough to burn paper.



You are completely misinterpreting Etendue. Temp has nothing to do with it. You cannot increase surface brightness by magnification.


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## more_vampires (Oct 6, 2015)

The surface brightness would be unchanged. The focus of the light over an area can be adjusted.

When focusing an LED, that's it and that's all you have. When focusing the sun, you can focus light from a larger and larger area.

This is the concept behind solar cookers. They don't work well at small sizes. Mine is about 5 feet I think. It boils in minutes.

An even larger dish would do it in seconds.


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## WalkIntoTheLight (Oct 6, 2015)

more_vampires said:


> The surface brightness would be unchanged. The focus of the light over an area can be adjusted.
> 
> When focusing an LED, that's it and that's all you have. When focusing the sun, you can focus light from a larger and larger area.
> 
> ...



Yes, but using a bigger magnifying glass just makes the hot-spot larger. You don't end up with a spot hotter than the sun; you just end up with more area that is really hot. So, you get a larger cooking area. Kind of like a large stove burner vs. a small stove burner. They're both just as hot, but the large burner will cook faster.

If you were to look through the magnifying glass at the sun, you'd see a larger sun with a larger magnifying glass. Both just as bright, but the larger one would cook your eye faster, as if you were "closer" to the sun.


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## more_vampires (Oct 6, 2015)

> Yes, but using a bigger magnifying glass just makes the hot-spot larger.


Not if you focus correctly? I burn stuff with fresnels and magnifying glasses all the time. Larger ones burn faster due to collection of more energy in a small spot.

Sometimes I focus in two stages, a page size fresnel focused by a secondary credit card fresnel. Proper focus gives you a higher concentration per surface area.

If you focused all of the light emitted by the sun into an area the size of your fist, it would have a higher temperature than the surface temp of the sun. It's energy per area.

Large stove eye vs small stove eye. For a situation where the surface temp is the same on both elements, the larger stove eye contains more heat as there is more material.

https://en.wikipedia.org/wiki/Heat_capacity#Table_of_specific_heat_capacities


> *Heat capacity* or *thermal capacity* is a measurable physical quantity equal to the ratio of the heat added to (or removed from) an object to the resulting temperature change.[1]​ The SI unit of heat capacity is joule per kelvin
> 
> 
> 
> ...



The large stove eye has a higher extensive heat capacity as it's dependent upon the quantity of substance.

This is sorta kinda like why larger magnifiers and huge parabolics burn and cook so well.


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## WalkIntoTheLight (Oct 6, 2015)

more_vampires said:


> Sometimes I focus in two stages, a page size fresnel focused by a secondary credit card fresnel. Proper focus gives you a higher concentration per surface area.



You can't get a higher concentration of light than the thing you are magnifying. All a magnifying glass does is magnify an image. Thus, a small bright sun, will look like a larger bright sun. Bigger magnifying glasses just make it an even bigger bright sun, but still with the same brightness as the original sun. i.e., You won't get a hotter spot than 5500 C, you'll just get a bigger one.

I suppose with a reflector setup, you could use many, many reflectors to cast many, many sun reflections on the same spot, thus making it brighter than the surface of the sun. I'm not sure about that one.


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## more_vampires (Oct 6, 2015)

> You can't get a higher concentration of light than the thing you are magnifying.


If that were true, then optics won't work. Solar concentrators wouldn't work, either.

https://en.wikipedia.org/wiki/Concentrated_solar_power


> *Concentrated solar power* (also called *concentrating solar power*, *concentrated solar thermal*, and *CSP*) systems generate solar power by using mirrors or lenses to concentrate a large area of sunlight, or solar thermal energy, onto a small area. Electricity is generated when the concentrated light is converted to heat, which drives a heat engine (usually a steam turbine) connected to an electrical power generator or powers a thermochemical reaction



When you get a lot of sunlight into a smaller area, awesome things happen.

The concentration of sunlight walking in the park on a fine summer day doesn't set your clothes on fire. By concentrating the sunlight from an area into a fine point, that very same sunlight now can set your clothes on fire.

Perhaps you are confusing total energy with energy per area? The sunlight hitting the surface area of that magnifying glass is the same quantity of sunlight that's in that fine point burning your pants. Consvervation of mass and energy is not broken.

It's in a higher concentration. There isn't more energy, it's just crammed into a smaller area now. Therefore, hotter.



> You won't get a hotter spot than 5500 C, you'll just get a bigger one.


I'd like to read a link on this.

https://en.wikipedia.org/wiki/Solar_power


> Commercial concentrated solar power plants were first developed in the 1980s. The 392 MW Ivanpah installation is the largest concentrating solar power plant in the world, located in the Mojave Desert of California.


We can't generate greater than 5500C with 392 megawatts of juice?

https://en.wikipedia.org/wiki/National_Ignition_Facility


> The resulting inward directed compression is expected to compress the fuel in the center of the target to a density of about 1,000 g/cm3​ (or 1,000,000 kg/m3​);[26]​ for comparison, lead has a normal density of about 11 g/cm3​ (11,340 kg/m3​). The pressure is the equivalent of 300 billion atmospheres.[10]​ It is expected this will cause about 20 MJ of fusion energy to be released, resulting in a net fusion energy gain of about 15 (G=Fusion energy/UV laser energy).[25]
> ​


The US National Ignition Facility is working on a 500 terawatt laser in a single pulse of a few pico seconds. They take their time, slowly charging a 422 megajoule capacitor bank. Capacitor banks help concentrate the energy, the input certainly isn't as fierce as the output. The thing is time. The banks are fed with energy over time, concentrated to be more powerful than the input.

Same energy, just the rate of transfer is the key point.

I'm pretty sure the US NIF laser can top 5500C. It could even be solar powered, theoretically.


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## ForrestChump (Oct 6, 2015)

I think we may have already passed it.....

I mean 200 lumens in a preferred beam pattern covers just about anything....

I can see a need for more for _specific_ applications. But IMO for Joe Blow CPF... I find beam pattern has greatly influenced my decision over raw output.


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## WalkIntoTheLight (Oct 6, 2015)

more_vampires said:


> The concentration of sunlight walking in the park on a fine summer day doesn't set your clothes on fire. By concentrating the sunlight from an area into a fine point, that very same sunlight now can set your clothes on fire.



If you were 100 times closer to the sun, then that sunlight would set your clothes on fire. Which is all that a magnifying glass does: it enlarges the image, and makes it appear closer. It does not make the surface brightness of that object any more bright.



> Perhaps you are confusing total energy with energy per area? The sunlight hitting the surface area of that magnifying glass is the same quantity of sunlight that's in that fine point burning your pants. Consvervation of mass and energy is not broken.



I never said it wasn't. I'm saying that the small area of light on your pants has no more surface brightness than the sun.

You're not magnifying a point light source. The sun has an area; it has a surface brightness. The surface brightness remains constant. You _can not_ focus the sun into a point. It will always have an area, and that area will not have a greater brightness than the surface brightness of the sun.


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## more_vampires (Oct 6, 2015)

WalkIntoTheLight said:


> If you were 100 times closer to the sun, then that sunlight would set your clothes on fire. Which is all that a magnifying glass does: it enlarges the image, and makes it appear closer.


https://en.wikipedia.org/wiki/Fresnel_Imager


> A *Fresnel imager* is a proposed ultra-lightweight design for a space telescope that uses a Fresnel array as primary optics instead of a typical lens. It focuses light with a thin opaque foil sheet punched with specially shaped holes, thus focusing light on a certain point by using the phenomenon of diffraction. Such patterned sheets, called Fresnel zone plates, have long been used for focusing laser beams, but have so far not been used for astronomy. No optical material is involved in the focusing process as in traditional telescopes. Rather, the light collected by the Fresnel array is _*concentrated*_ on smaller classical optics (e.g. 1/20th of the array size), to form a final image.[1]​





> It does not make the surface brightness of that object any more bright.


We agree on this. Us using a magnifying glass on earth doesn't affect the sun's surface brightness. That's silly.

Magnifiers concentrate the sun's light. They do not make the sun bigger.  Don't point lenses at the sun. When concentrated, the brightness in that small area is brighter and hotter.

As you increase the area that catches the light and throw it into a smaller spot, the spot gets brighter.



> You're not magnifying a point light source. The sun has an area; it has a surface brightness. The surface brightness remains constant. You _can not_ focus the sun into a point. It will always have an area, and that area will not have a greater brightness than the surface brightness of the sun.


Always have an area, in real life? Yes. This area begins to approximate a point as your focusing improves.
https://en.wikipedia.org/wiki/Focal_length
Theoretically, you CAN focus light into a point spot. Look at the pics on the right side of the page in the focal length link. Is it easy? No, not really. Pulling this off means you now have perfectly focused concentration. A point has no dimensions. A real world magnifier focusing the sun will have an area, but as focus becomes perfect it approximates a point.

The smaller the dot, the hotter the dot. The heat of this dot increases as you collect more light. Using a 3 foot by 5 foot fresnel and a secondary (perhaps tertiary) lens to further refine the beam can do some crazy things. That's only 3x5'.

In the extreme, if you collected 100% of the sun's output and put it in a dot that size, it would indeed exceed the average surface temperature of the sun. Concentration.

http://www.solarcooker-at-cantinawest.com/best_solar_cooker_solar_burner.html
This 5 foot solar cooker is about like mine. It peaks at about 440C. That's only a 5 foot dish, a tiny tiny fraction of the sun's output. Simply make it bigger. And bigger. The more light you collect, the higher the temperature. There is no upper limit to the size of the reflector barring what can be built. The more perfect the focus, the smaller the spot, I've no doubt that 5500C/5778K can be exceeded.

The solar power industry isn't really going above 800C-1000C right now because they don't have to. They're using working fluids (molten salt, whatever) that have a temperature THEY want to operate with. Nothing stopping a big gigantic parabolic collector from vaporizing iron except we have no functional utility for that so they don't exist. 

:twothumbs*COOL LINK!!!*
http://www.tomsguide.com/us/sun-deathray-solar-furnace-focusing-mirror,news-9081.html


> *The sun-powered death ray generates over 6,300 degrees at its focal point.*


Note that the reflector for this isn't really all that BIG! A larger version can go even higher.

Shanghai Solar Metal Foundry:
https://shanghaimetalcorporation.wo...t-metal-an-efficient-metal-processing-method/

https://en.wikipedia.org/wiki/Dyson_sphere
A Dyson sphere is a bit of a thought experiment on capturing 100% of the sun's output. We can't build one, of course, but capturing 100% of a star's output and putting it into a small point seems to be what we're discussing for some reason. I guarantee you that spot would be hotter than the average surface temp of the sun as the energy is now concentrated. Energy density per area, with area approaching zero.

The larger the magnifier does not necessarily mean a larger hotspot. That means you have a crappier magnifier or haven't focused it correctly. Secondary lenses to further refine the main one are quite doable. 

I'm not saying my 8.5" x 11" page fresnel primary and credit card fresnel secondary yields hotter than the surface of the sun, nor is it 5500C. What I am saying is there are non-science-fiction ways that we can concentrate solar energy to exceed 5500c. I think the 500 terrawatt National Ignition Facility laser beats that a bit, we already have a solar facility that could power it with room left over.

500 TW of lumens? Dat's a lotta lumens.

Also: Melting steel with the sun
http://www.treehugger.com/clean-technology/melting-steel-with-only-the-sun-video.html


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## SemiMan (Oct 6, 2015)

more_vampires said:


> The surface brightness would be unchanged. The focus of the light over an area can be adjusted.
> 
> When focusing an LED, that's it and that's all you have. When focusing the sun, you can focus light from a larger and larger area.
> 
> ...



And you can never exceed the surface brightness or radiation level more accurately of the sun by using magnification.


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## SemiMan (Oct 6, 2015)

more_vampires said:


> If that were true, then optics won't work. Solar concentrators wouldn't work, either.



More_Vampires,

Please refrain from posting more until you thoroughly understand Etendue. You don't and hence you keep posting things that are not right.


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## agnelucio (Oct 6, 2015)

bykfixer said:


> Once upon a time the vinyl record was replaced with the 700 mb cd...but now the pinky nail sized memory card can do (last time I looked) 32 gb.



HEHEHEHEHE: http://www.cnet.com/uk/news/microdia-will-sell-a-1000-ish-512gb-microsd-come-july/


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## more_vampires (Oct 7, 2015)

SemiMan said:


> More_Vampires,
> 
> Please refrain from posting more until you thoroughly understand Etendue. You don't and hence you keep posting things that are not right.


I'm not afraid to be wrong and try to be a gentleman about it when someone points out a slip of the keyboard or mind. I apologize and correct myself. I think we are opposites. I try to learn as much as I can as a life choice. I will never stop trying to learn more and sharpen what I know. I don't care how much you insult me.

How then, did we achieve 6,300 degrees focusing the sun? There's a link to that above.

Please disprove it. We need more than "lol you're wrong."

Using primary and secondary optics/reflectors to focus the sun works. Ever tried it? How do telescope arrays work, then?

Also, drop the ad hominem and try explaining your position. That's how discussion works. You're being condescending and dismissive as usual. Half the time I've seen you post, you only belittle others and contribute nothing; you usually refuse to explain your position. Stop being 50% troll, you're one of the least friendly and helpful posters here. I feel sorry for you, Semiman. *You violate CPF Rule #4 on a regular basis.* I've seen you do this to others. Since this is the first time you've done it to me, instead of reporting you, I'll just call you out.

6,300 degrees, sir. Disprove it. I even cited a source, an actual science facility.

While you're at it, disprove the multi-collector Shanghai Solar Metal Foundry.

I await your intelligent and cogent reply, more than "lol stop posting."

Science, not dirty debate tricks, sir. How rude. You failed to make a single point.


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## markr6 (Oct 7, 2015)

Topped out? I believe we're already there. Lights that get too hot to hold after 3 minutes, 1 minute, 30 seconds! I'm more interested in long runtimes, form factor, quality, tint and beam type. Bragging about a 6000lm vs 5000lm light, which can hardly be see to the human eye and only max possible in the first 30 seconds (who cares?!?!?!?) doesn't do anything for me. Sure it gives modders something fun to play with, but for OEM lights, I don't care to see any monster hand warmers.


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## more_vampires (Oct 7, 2015)

> Topped out? I believe we're already there. Lights that get too hot to hold after 3 minutes, 1 minute, 30 seconds!


Awww man! Those are my favorite lights! I *enjoy* my 6 minute total runtime and having to turn the light off after 2 minutes because I'm working on first degree burns on my hands.

These are a few of my favorite things! 

I love runtime too, though.  I like you, Mark. You are friendly and funny, it's greatly appreciated. I enjoy reading your posts.


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## WalkIntoTheLight (Oct 7, 2015)

more_vampires said:


> How then, did we achieve 6,300 degrees focusing the sun? There's a link to that above.



First, that's 6300 F, or about 3500 C, which is still much less than the surface of the sun, which is 5500 C.

Second, they're using mirrors, probably a whole bunch of tiny reflective mirrors which overlap the rays at the focal point. I'm not sure if the same logic about surface brightness applies to many mirrors as it does to a single magnifying glass (someone can correct me on this).


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## more_vampires (Oct 7, 2015)

They can make the Solar Death Ray bigger, you know. AFAIK, we have no functional utility for that tech so it's just a science facility.

That's gotta be a massive ton of lumens. It vaporizes stuff as it is.

The Shanghai Solar has no need to vaporize metal, just melt it so it doesn't "go that high."

The could have made that one bigger as well.


> I'm not sure if the same logic about surface brightness applies to many mirrors as it does to a single magnifying glass (someone can correct me on this).


I think you're right, sir. I agree, someone please enlighten us if we're wrong. Wouldn't it be the summation of the arbitrary number of primaries used? Don't think the SSMF uses secondaries like the Solar Death Ray does.

What I'm really curious about is how many lumens in the SDR and the SSMF.

I really wonder where can we top out with that tech, even though there's no real use for scaling it that high (yet.)


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## scs (Oct 7, 2015)

Doesn't this clear things up? 
https://en.m.wikipedia.org/wiki/Luminance

Last paragraph under "Explanation."


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## scs (Oct 7, 2015)

scs said:


> Doesn't this clear things up?
> https://en.m.wikipedia.org/wiki/Luminance
> 
> Last paragraph under "Explanation."



MV is referring to illuminance or lux, which does increase, and WITTL is referring to luminance or surface brightness, which doesn't with "real passive optics."

The question is is the surface temperature of the Sun determined by the luminance of the Sun?


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## scs (Oct 7, 2015)

My intuition feels that temperature on the surface of the focused image should be a function of illuminance or lux on that surface., so my feeling is even with real passive optics, the temperature on the surface of the focused image can be higher than the surface temperature of the source.


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## more_vampires (Oct 7, 2015)

Thanks for a real post, SCS! We appreciate you! 



scs said:


> The question is is the surface temperature of the Sun determined by the luminance of the Sun?


http://www.astronomycafe.net/qadir/ask/a11354.html


> These estimates show that the emission of light at the surface can lag the production of light at the core by about 100,000 years or so.


I suppose the surface temp of the sun would be related to the time for photons to escape, how many are in there at once. I'd imagine that there are massive numbers of factors that make the surface temperature so.

https://en.wikipedia.org/wiki/Sunlight


> Direct sunlight has a luminous efficacy of about 93 lumens per watt of radiant flux, higher than most artificial lighting, including fluorescent. Multiplying the figure of 1050 watts per square metre by 93 lumens per watt indicates that bright sunlight provides an illuminance of approximately 98 000 lux (lumens per square meter) on a perpendicular surface at sea level. The illumination of a horizontal surface will be considerably less than this if the Sun is not very high in the sky. Averaged over a day, the highest amount of sunlight on a horizontal surface occurs in January at the South Pole (see insolation).


On earth, 98,000 lux? Wow, the sun's a pretty good flashlight!


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## Parrot Quack (Oct 7, 2015)

Just saying, have a "welder's" screen at the handy.


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## WarRaven (Oct 7, 2015)

Good read so far guys.
I used to be impressed by sunlight, then I got a Javelot.
It's just not the same anymore idk🔦

J/k, mostly☺


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## more_vampires (Oct 7, 2015)

Yah, WR. One day we'll look back and say "yeah that Sun used to be pretty good but check this out... *CLICK* AAAAAARRRRRRGH MY EYES!! IM ON FIRE!"



Can't wait.


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## scs (Oct 7, 2015)

more_vampires said:


> Thanks for a real post, SCS! We appreciate you!



Thank you guys for discussing interesting topics. They spark my curiosity and lead me to do some outside reading and learn something new.


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## SemiMan (Oct 7, 2015)

scs said:


> My intuition feels that temperature on the surface of the focused image should be a function of illuminance or lux on that surface., so my feeling is even with real passive optics, the temperature on the surface of the focused image can be higher than the surface temperature of the source.



First take temperature out of the equation, it is not a valid measure. The valid measure is surface brightness, or radiant energy per surface area as a rough measure. Temperature matters only if you are comparing black body radiators. 

The principle of Etendue shows that radiance cannot increase. 

Let's put this into LED perspective. No matter how big a reflector is on a flashlight, you will never have 0 beam divergence. There will always be some. You will never be able to focus it to something brighter than the surface of the LED either.

The same applies to the sun. You can't focus it to brighter than the sun, even with an infinite reflector.


To More_Vampires .. I am friendly to those that don't argue incessantly on thing they are not knowledgeable on, especially when many have pointed out their error. I was not unfriendly to you, but feel free to feel that way. Perhaps wander over to automotive in CPF and see how the mods treat people who continuous argue things they are wrong on.


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## more_vampires (Oct 7, 2015)

Virgil, Alaric and I get along quite well, thanks. Nice non-sequitur by the way. This is not the automotive lighting section, nor does it excuse rudeness. I said drop the dirty debate tricks. This is not about life-and-death automotive safety lighting, which is why those fine gentlemen get a little gruff sometimes. They are understandably tired of the same questions of something unsafe over and over and over again.



> The same applies to the sun. You can't focus it to brighter than the sun, even with an infinite reflector.


So let's put this in an LED perspective. If we had 1 million emitters focused on the same spot, wouldn't it be brighter than one? That's how multiple arrays work, your rudeness in telling me to shut up aside. This was my point in focusing the sun's energy hotter than surface temperature, you've seemed to miss that or else I wasn't clear about it. There's more than one tech other than ONE optic/reflector to focus a spot.

Stop breaking rule #4. Telling people to shut up is a violation of rule #4. Put me on your ignore list or don't login here if you can't stand discussion. I like talking with new people who don't know stuff. I enjoy interaction with the (mostly) very friendly and knowledgable people of CPF. I like talking to people who know more. That's how we learn by interaction.

We're supposed to work together towards the truth. Note I'm not insulting you, merely pointing out you're breaking the rules whether you realize it or not. Maybe you don't realize exactly what it is you're typing? Oh well, I let you know. It's only fair.

Now, drop it and let's get back to the brightest lights possible.


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## SemiMan (Oct 7, 2015)

more_vampires said:


> Virgil, Alaric and I get along quite well, thanks.
> 
> 
> So let's put this in an LED perspective. If we had 1 million emitters focused on the same spot, wouldn't it be brighter than one? That's how multiple arrays work, your rudeness in telling me to shut up aside.
> ...




If those emitters were placed side by side (no gap) on a flat plate, or were placed side by side (no gap) on a spherical surface, then no, you could not focus them on a spot that was brighter than any given emitter .... again, read about Etendue.

Feel free to put me on ignore More_Vampires and perhaps there is a moderator position open on CPF. This is not really a discussion. You are positing false information, I am correcting it so that others do not acquire wrong information. Others have also pointed out your inaccurate position as well. You keep arguing that position. Others may think you are right. You are not. Hence why I don't ignore you, cause I consider accurate information on CPF important as people use this website as a resource.


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## WarRaven (Oct 7, 2015)

Is point of the sun that, its not putting out power in just one spot, its measured in one spot but radiates 360 degrees.
If focused into a spot, all of it, it should be pretty darn intense.
It's putting out that power we scope in our thoughts on a given area, when the originating source is pointing at just a degrees fraction at any one point naturally.


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## more_vampires (Oct 7, 2015)

WR, this is my thinking as well. Perhaps I'm wrong. Harnessing a sizeable fraction of the Sun's energy! Wow, that would be fascinating.


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## WarRaven (Oct 7, 2015)

I'm pretty loose in my grammar so I try to avoid threads as interesting as this so not to enflame others.

Mutli emitters are never flat unless in flood type of lights, that is bizarre to suggest that.
Or emitters may be flat, but reflectors are far from it.


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## more_vampires (Oct 7, 2015)

One thing I know for sure is the human race has a history of making the impossible possible.

In the 90s, if you told someone about the 15,000+ lumen multi emitter LED lights we have now they probably wouldn't believe you.

The XHP70 quad is really something else!


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## WarRaven (Oct 7, 2015)

On, I get the idea of flat emitters mentioned I guess, basically wafer mates of the XHP line.
OK, now a million wafer mates or four, focused.


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## scs (Oct 7, 2015)

SemiMan said:


> First take temperature out of the equation, it is not a valid measure. The valid measure is surface brightness, or radiant energy per surface area as a rough measure. Temperature matters only if you are comparing black body radiators.
> 
> The principle of Etendue shows that radiance cannot increase.
> 
> ...



SemiMan, thanks for elaborating. Please let me know if and why the following questions are flawed:

Is it possible to determine the average illuminance (lux) in an area on the surface of the die?
Is it possible to determine the peak illuminance within that area?
Is it possible to determine the max illuminance on the surface of the die?
Are you saying that the beam from that die cannot be focused by any simple reflector so that the illuminance at some point along that beam is higher than the max illuminance at the surface of the die?

Thanks.

Again, I'm talking about illuminance. When you say "bright," are you referring to illuminance as well, or to luminance or something else?


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## WalkIntoTheLight (Oct 7, 2015)

SemiMan said:


> If those emitters were placed side by side (no gap) on a flat plate, or were placed side by side (no gap) on a spherical surface, then no, you could not focus them on a spot that was brighter than any given emitter .... again, read about Etendue.



Okay, that's interesting to know. I wasn't sure if one could build a multiple reflector setup to focus a bunch of reflections all on one spot, and end up with something that's brighter than the original surface area. (I know you can't do it with a refractor optic.) So, you can't do it with LEDs, but could you do it with the sun? i.e., if Archimedes made a "death ray" by focusing a million mirrors on a ship, would that death-spot have a higher illumination than the surface of the sun?

I'm guessing no, but I'm still not sure.


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## Bullzeyebill (Oct 7, 2015)

Gentlemen, please get along and do not disparage each other. Criticize the post, not the poster. Follow Rule 4.

Bill


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## jmwking (Oct 7, 2015)

Physics 101: A magnifying lens takes the light collected on its surface area and focus it into a smaller area. The sun gives us (practically speaking) parallel light beams when they hit the earth (93MM:8000 miles in the tropics). Any surface area that can collect those photons and focus them into a smaller point increases the point energy while simultaneously reducing energy in the surrounding area below the lens. That's what magnifying lenses do. An imaginary, big enough magnifying lens would vaporize the surface of the Earth. A sufficiently bigger one would vaporize the Earth. (Our Sun is a hot sucker! A few billion years from now, we're toast!)

Magnifying lenses are additive - they magnify. If we had a 200,000 square mile lens and focused all the sun's light into a smallish point, anything that moved through it would be plasma. If we could collect that energy - with current solar panel designs - and distribute it, we'd be able to power the whole world. 

Hell, a curved building in England melts cars parked with an unfortunate focal point.

The problem gets more complicated when the light rays aren't parallel. A parabolic curve of LED emitters focused on a lens which is then focused onto a small area could generate lots of heat - plenty enough to start a fire.

-jk


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## SemiMan (Oct 7, 2015)

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## SemiMan (Oct 7, 2015)

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## ElectronGuru (Oct 7, 2015)

Illum said:


> The infrared heat emitted from LEDs is negligible, it might be hot enough to burn paper provided the paper used possesses the ability to absorb ALL of the light produced by the LED, including the wavelengths of the visible spectrum.



We've found brute force to be fairly effective:


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## SemiMan (Oct 7, 2015)

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## SemiMan (Oct 7, 2015)

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## SemiMan (Oct 7, 2015)

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## WarRaven (Oct 7, 2015)

I'm liking the new trend in this thread.
Informative, thank you.👍


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## RickZ (Oct 8, 2015)

WalkIntoTheLight said:


> My BS detector went off, so I decided to try it. As expected, it just turns a nice reflector light into one of those cheap optic throwers with the square LED hot spot. Warm to the hand, but less warm than if you just held your hand closer to the flashlight without any magnifying glass.
> 
> IIRC, you can't magnify an image to be any hotter than what the surface temperature of the source object is. For example, you can't magnify the sun hotter than 5500C. I don't know what the surface temperature of an LED is, but probably not hot enough to burn paper.



I don't know how you tried it, or what physics teacher you had, but with a powerful enough magnification you can get 1,000 lumens of some flashlights to hot enough to light paper, I've done it. In fact, even 350 lumens. Magnifying light has nothing to do with heat or the temperature of the source (which is usually over 100℃ which is 200℉ hot enough for the flashpoint of kindling,) it has to do with light(photons) and the electronic temperature it drives when it hits an atom. Enough light (lumens) and enough magnification and things can light on fire. Either, 
1) your magnifying glass was very reflective and the point was not small enough
2) your flashlight was not continuously burning at the full 1,000 lumens or more (better be a spotlight too)
3) your flashlight is giving off less infrared than normal LEDs, a sign of high quality and a late design.
4) the point of focus was not dense enough
5) the paper was flat against something absorbing the heat, or had a higher flashpoint etc.
6) ambient room temperature and air etc. Caused cooling.
7) other effects I can't speak for
8) two or three combined of extremely low quantity each together were enough to throw it off.
9) oh yes and angle. Angle is huge. Must be lined up exactly which us far harder than it sounds.

I'm not a babysitter though. Correct above and if you live over 5,000 feet in altitude and have lower than %20 humidity it should work. There might be videos online to help you understand that magnifying light to get high temps has nothing to do with heat of the object magnified.


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## RickZ (Oct 8, 2015)

jmwking said:


> Physics 101: A magnifying lens takes the light collected on its surface area and focus it into a smaller area. The sun gives us (practically speaking) parallel light beams when they hit the earth (93MM:8000 miles in the tropics). Any surface area that can collect those photons and focus them into a smaller point increases the point energy while simultaneously reducing energy in the surrounding area below the lens. That's what magnifying lenses do. An imaginary, big enough magnifying lens would vaporize the surface of the Earth. A sufficiently bigger one would vaporize the Earth. (Our Sun is a hot sucker! A few billion years from now, we're toast!)
> 
> Magnifying lenses are additive - they magnify. If we had a 200,000 square mile lens and focused all the sun's light into a smallish point, anything that moved through it would be plasma. If we could collect that energy - with current solar panel designs - and distribute it, we'd be able to power the whole world.
> 
> ...



Thank you. Sounds like someone went to high school or even college physics.

Magnifying glasses do something cute. They magnify. Get the point small enough (and make sure the magnifying glass is inches from the thing you are tying to light, as the flashlight will be over 10' away, you can't do this holding things in your hands btw, and the angle of the light must be perfect as the magnifying glass is, best to test the experiment by using a magnifying glass to burn the object you are trying to light using the actual sun first as a control) and, use a large, reflector based spotlight, and at 1075 lumens it should light. I used a coast light with 1075 lumens, pencil beam.


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## WalkIntoTheLight (Oct 8, 2015)

RickZ said:


> I don't know how you tried it, or what physics teacher you had, but with a powerful enough magnification you can get 1,000 lumens of some flashlights to hot enough to light paper, I've done it. In fact, even 350 lumens. Magnifying light has nothing to do with heat or the temperature of the source (which is usually over 100℃ which is 200℉ hot enough for the flashpoint of kindling,) it has to do with light(photons) and the electronic temperature it drives when it hits an atom. Enough light (lumens) and enough magnification and things can light on fire. Either,
> 1) your magnifying glass was very reflective and the point was not small enough
> 2) your flashlight was not continuously burning at the full 1,000 lumens or more (better be a spotlight too)
> 3) your flashlight is giving off less infrared than normal LEDs, a sign of high quality and a late design.
> ...



As Semiman pointed out, my logic was flawed because LEDs are not a blackbody source. I was thinking that you couldn't get something hotter than the LED, because you can't do that with the sun (which is a blackbody source).

So, with LEDs, I'm willing to accept that you could burn paper. Though, I'd have to actually see someone do that.


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## more_vampires (Oct 8, 2015)

I agree, Bill. Let's bring back that CPF-friendly that makes this place wonderful.



> I wasn't sure if one could build a multiple reflector setup to focus a bunch of reflections all on one spot,


AFAIK, that's exactly how the Solar Death Ray and the Shanghai Solar Metal Foundry work. Multiple collectors, all feeding the crucible. It's why I posted those links.

The reactive collectors in the SSMF are absolutely amazing, anyone seen the pics? Worth a look. They are tuneable variable shape and sun-tracking. Amazing. They can "go flat" and turn away to "turn off" the melting.

Mythbusters did a bit on the Archimedes Death Ray, IIRC they ended up saying "can't be done." It's kind of amusing that a metal foundry pulled it off. I think the key was tunable large reflector arrays versus a lot of flat reflectors.


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## WalkIntoTheLight (Oct 8, 2015)

more_vampires said:


> AFAIK, that's exactly how the Solar Death Ray and the Shanghai Solar Metal Foundry work. Multiple collectors, all feeding the crucible. It's why I posted those links.



Yes, but you implied that the hot spot was hotter than the surface of the sun. It isn't. You can't build a solar death ray that gets hotter than 5500 C (10000 F).

I never said you couldn't make a really hot focal point, I just said you can't make it hotter than the sun's surface illumination.


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## more_vampires (Oct 8, 2015)

> Yes, but you implied that the hot spot was hotter than the surface of the sun.


Afaik, enough energy collected is enough energy collected. It seems to me that with an arbitrary number of multiple arrays, an aribitrary amount of energy can be collected within limits of land mass and other limits such as manufacturing, power transmission and such.

Sorry if that didn't come out correctly. Not a pocket magnifier. We agree.

I am talking about a combination of technologies, not a simple reflector. I've already stated this SEVERAL times.

What I was trying to say is that both of those facilities (SDR and SSMH) *could* have been bigger, with more energy collected from a larger area with more of the multiple direct array tech that we're playing with right now. I'm sure there's an upper limit on the number of arrays due to logistics, line of sight, terrain, and such, but that shouldn't affect the theory... right? The foundry has no need to vaporize metal so they didn't go for the hottest they could get. It's on relatively flat ground, to increase the direct arrays would likely require a bowl-shaped field around the crucible. The variable temp control they have now is within working tolerances so the engineers said "good enough" and filed their vouchers.

Yes, a single reflector/optic has limits, direct solar arrays have distance and positioning limits. *When the energy is collected as electricity as an intermediary, as in the case of the huge multi megawatt solar facilities,* my point was more than 5500 degrees could indeed be devloped as the focusing distance and positioning limits of the direct solar arrays go away. Using electricity as an intermediary path would bypass a lot of technical issues and problems facing the limits of direct solar heating. That's what I meant to say before we got sidetracked. Sadly, a lot of our bulk collectors are only running maybe 20-40% efficiency right now AFAIK. We make up for it in numbers at this time and cost per unit.

There's literally hundreds of gigawatts worth of solar facilities world wide at this moment. With that kind of energy, how could we not break 5500 degrees? That's another thing I was trying to express, though I guess I didn't do as well as I normally do. A megawatt is a megawatt and they do what they do, regardless of solar origin or not.

There's more than one way to skin a cat and more than one solar technology. I'm sorry if we got hung up on single optic/reflector which wasn't what I was really talking about to start with. Sorry for any confusion that may have caused. Multiple arrays, and multiple arrays with energy storage was really what I was driving at. 



> You can't build a solar death ray that gets hotter than 5500 C (10000 F).


This is why I gave the US National Ignition Facility as an example, it could indeed be powered by energy harvested from the sun. I wasn't saying that it IS solar powered, but could easily be due to electricity being electricity and megawatts are megawatts. You're not powering that thing with a 3x5' fresnel lens. We are on the same page on that, no problem there.

The Large Hadron Collider also comes to mind, I read that their highest temp to date was in the trillions of degrees. Multi megawatt solar could run that as well, we'd just have to hook up the cables so to speak. When you leverage the power grid, it doesn't matter WHERE the power was generated or by what technology. We could use the Sun to run that thing. AFAIK, that thing isn't solar ATM, but could be. That was the point I was trying to make. I wasn't trying to imply the US NIF or the LHC were solar, but that they COULD be and this alone takes us past 5500 degrees.

I think the secret of human technology is to leverage more than one technique at the same time and build upon the body of technology that exists.

I think the big side track was me not properly conveying this: that I was trying to speak of the breadth of solar that's out there right now, from molten salt thermal storage to potential energy water tower storage, to heat device (turbine electric generation and metal foundry,) to direct electricity conversion (photovoltaic.) Solar's come a long long way in a very short time. I think it's exciting. Efficiency is improving, but our bulk collection is still languishing in low efficiencies. The high efficiency stuff is really expensive per watt and it goes on satellites and such where price is basically no object.

Pretty sure I kept saying there was more than one solar tech, sorry for any confusion. Come on guys, you know we can exceed 5500 degrees with solar technologies. You're just not going to do it with a pocket magnifying glass, more like a solar farm. How can 3 gigawatts fail? Those are the gigawatts we're looking for.

https://en.wikipedia.org/wiki/Solar_power_by_country
142 GIGAWATTS worldwide in 2013! Take that, 1.21 gigawatts! 
178 GW in 2014! It's going crazy!

When I was a kid, I never would have thought we'd have a direct focus solar metal foundry outside of sci-fi. That's simply amazing.

Did I do better than time? Hope so. Hate the thread got hung up on junk. Let's get back to the awesome!


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## WalkIntoTheLight (Oct 8, 2015)

Well, if all you're saying is that we can use solar power to make electricity that we then use to power devices capable of temperatures higher than 5500 C, then solar power is just a red herring. We can do that with any energy source.


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## more_vampires (Oct 8, 2015)

There, done editing. Hope I didn't mess up again! Thoughts on solar? We can certainly jump back into LED and the wonderland that it is.

Moore's Law for LED? Perhaps?
https://en.wikipedia.org/wiki/Moore's_law


> *Moore's law* (/mɔərz.ˈlɔː/) is the observation that the number of transistors in a dense integrated circuit doubles approximately every two years. The observation is named after Gordon E. Moore, the co-founder of Intel and Fairchild Semiconductor, whose 1965 paper described a doubling every year in the number of components per integrated circuit,[note 1]​ and projected this rate of growth would continue for at least another decade.[2]​ In 1975,[3]​ looking forward to the next decade,[4]​ he revised the forecast to doubling every two years.[5]​[6]​[7]​



We're starting to do this with the multi die packages like XHP70 and such. What would the outputs be if the emitters in a package started doubling every 2 years with each individual maintaining the same output, yet getting smaller? Crazy. I know emitter efficiency is nowhere near doubling every 2 years, we're lucky to get 7-9% in a year. Still awesome. Perhaps we can break the peak theoretical efficiency and output before we reach the currently announced limits? That's exactly what we did with computer technology.

"We can't do that."
"The engineers just did 10x that."
"Oh, guess we can..."



WalkIntoTheLight said:


> Well, if all you're saying is that we can use solar power to make electricity that we then use to power devices capable of temperatures higher than 5500 C, then solar power is just a red herring. We can do that with any energy source.


My thoughts exactly, sir. Energy is energy and solar is solar. There's only one kind of electron (not counting antiparticles,) AFAIK.

We were talking about doing it with the sun and AFAIK, it's possible with the right combo of techniques. I love science and technology. I can't know enough, not possible.


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## SemiMan (Oct 8, 2015)

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## SemiMan (Oct 8, 2015)

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## WalkIntoTheLight (Oct 8, 2015)

more_vampires said:


> We're starting to do this with the multi die packages like XHP70 and such. What would the outputs be if the emitters in a package started doubling every 2 years with each individual maintaining the same output, yet getting smaller? Crazy. I know emitter efficiency is nowhere near doubling every 2 years, we're lucky to get 7-9% in a year. Still awesome. Perhaps we can break the peak theoretical efficiency and output before we reach the currently announced limits? That's exactly what we did with computer technology.



Nobody's going to break theoretical limits. IIRC, that's somewhere around 650 lumens/watt, with a green light source that our eyes are most sensitive to (thus achieving the highest lumens). If we can only get 650 lumens out of a watt, that's all we're ever going to get.

White light is quite a bit lower than 650 lumens/watt. I think it's somewhere in the 400's. Because our eyes are less sensitive to the other spectral colours in white light, so less lumens.

You might be able to genetically engineer better eyes for humans, that are more sensitive to light. I'm not sure if that changes the definition of a lumen, but regardless it's not going to get more light out of a watt.


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## more_vampires (Oct 8, 2015)

SemiMan said:


> As long as we are clear, no matter one reflector or 10 billion mirrors, you will never surpass 5500K. No matter logistics , placement, or anything else its not going to happen. This is laws of physics stuff not engineering.



Did you even read post #74? You didn't did you. Here is the salient point you keep missing and go on saying stuff that's not correct from the standpoint of what I said. This is getting old.



> Using electricity as an intermediary path would bypass a lot of technical issues and problems facing the limits of direct solar heating. That's what I meant to say before we got sidetracked.



Do you realize that I'm saying we can run a plasma arc welder at 20,000C at a bit less than 4000watts from electricity generated by photovoltaic?

Electricity generated by solar is not somehow weaker than other electricity. Electrons are electrons. You keep talking about limits, I keep talking about bypassing them. You keep ignoring my explaination of a combination of technologies. That's the salient point you're ignoring. From your words, you don't seem to understand what 178 gigawatts can do.

Please stop intentionally misconstruing my words. It's really getting old. You're not reading and you're running your keyboard instead.


WalkIntoTheLight said:


> Nobody's going to break theoretical limits. IIRC, that's somewhere around 650 lumens/watt, with a green light source that our eyes are most sensitive to (thus achieving the highest lumens). If we can only get 650 lumens out of a watt, that's all we're ever going to get.
> 
> White light is quite a bit lower than 650 lumens/watt. I think it's somewhere in the 400's. Because our eyes are less sensitive to the other spectral colours in white light, so less lumens.
> 
> You might be able to genetically engineer better eyes for humans, that are more sensitive to light. I'm not sure if that changes the definition of a lumen, but regardless it's not going to get more light out of a watt.



WITL, I think you're polite, intelligent, educated, and imaginative. I like that. You're a great conversation partner. Glad we had a chance to chat a bit. You rock. :thumbsup: I think you're one of the best of CPF!

So at 650 lumens/watt something like the Oveready Triple Wasp at 21 watts would be 13,650 lumens in a pocket light.  I think I could live with that but would be sad if we could find no other way to push the envelope aside from simply adding more emitters and upping the wattage that way.

Your thoughts on genetic engineering to improve eyesight are fascinating to me. 200 years ago, we didn't have television never mind computers. So much tech has come to fruition in the past 20 years, things unimaginable before.

Maybe it might become common place? Today, we're fixing people's eyes with lasers (Lasik) and if you'd never heard about it before it sounds crazy.

I think acclimation to new tech is going to become an increasing issue in the next 20 years. Cybernetic implants are already here and it makes some people nervous. Cyber eyes and suddenly we only need 10 lumens? 
Cyber eye lenses here, augmented vision:http://gajitz.com/bionic-vision-cybernetic-lenses-with-heads-up-display/

https://en.wikipedia.org/wiki/Visual_prosthesis#Ongoing_projects 
Wow! 13 ongoing bionic eye projects, retinal implants... this is like science fiction, but becoming reality.


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## SemiMan (Oct 8, 2015)

more_vampires, I am not trying to put words into your mouth as you may imply, but have reached a conclusion on what you believed to be true, and based on post #74, may still believe to be true. I am not sure how I could misconstrue what you have posted either? Please let me recap:

--------------------------------------------------------------------

In response to WalkIntoTheLight saying you can't focus the sun hotter than 5500C .....



more_vampires said:


> Not quite. If you had a 1500 foot parabolic mirror, that hotspot is going to get quite a bit more than 5500c. With enough area of light concentrated, you can do interesting things.



In response to semiman saying you can't increase surface brightness ...


more_vampires said:


> The surface brightness would be unchanged. The focus of the light over an area can be adjusted.
> 
> When focusing an LED, that's it and that's all you have. When focusing the sun, you can focus light from a larger and larger area.



In response to Walkintothelight saying if you get a bigger magnifying lens to concentrate the sun, you just get a bigger spot, not a brighter/hotter one ...


more_vampires said:


> Not if you focus correctly? I burn stuff with fresnels and magnifying glasses all the time. Larger ones burn faster due to collection of more energy in a small spot.



In response to Walkintothelight saying you can't get a higher concentration of light than the thing you are magnifying .....


more_vampires said:


> If that were true, then optics won't work. Solar concentrators wouldn't work, either.
> 
> Theoretically, you CAN focus light into a point spot. Look at the pics on the right side of the page in the focal length link. Is it easy? No, not really. Pulling this off means you now have perfectly focused concentration. A point has no dimensions. A real world magnifier focusing the sun will have an area, but as focus becomes perfect it approximates a point.
> 
> ...



Ah ... no, somewhat no, and no. You cannot theoretically focus light into a point spot. You cannot using an optical solar collector/concentrator (which was being discussed), exceed the average surface temperature of the sun.




more_vampires said:


> So let's put this in an LED perspective. If we had 1 million emitters focused on the same spot, wouldn't it be brighter than one? That's how multiple arrays work, your rudeness in telling me to shut up aside. This was my point in focusing the sun's energy hotter than surface temperature, you've seemed to miss that or else I wasn't clear about it. There's more than one tech other than ONE optic/reflector to focus a spot.



Again wrong. It does not matter how many reflectors you use, what shape, size they are, etc. It's not going to be brighter than the sun at the focal point. If those 1 million emitters are on a flat plane (or curved like the sun), then no, you care not going to be able to concentrate them to brighter than one LED.


Post 74:


more_vampires said:


> Afaik, enough energy collected is enough energy collected. It seems to me that with an arbitrary number of multiple arrays, an aribitrary amount of energy can be collected within limits of land mass and other limits such as manufacturing, power transmission and such.
> 
> Sorry if that didn't come out correctly. Not a pocket magnifier. We agree.
> 
> ...


..... Excuse if I would confuse this to be you still implying that using optical means, which is all the SDR and SSMH use, could achieve a higher temp than the surface of the sun ... because they could not.


I read post 74. I also read all the other posts, and at least 6 times you said that using purely optical concentration, reflection, etc. (And not conversion to an intermediary method, like electricity), that it would be possible to achieve a spot temperature higher than the sun. 

It would not be possible.

Conversion to an intermediary, i.e. electricity, is, to use WalkIntoTheLight's wording, "A red herring". I feel you are in error saying I am putting words into your mouth, based purely on the items I have copied from your posts. I tried my best to not remove the context of your statements and hence I did not copy other phrases where concentration to higher than the suns surface temp was implied.

Semiman


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## SemiMan (Oct 8, 2015)

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## jmwking (Oct 8, 2015)

SemiMan said:


> No matter how many mirrors you used, the spot would not have a higher illumination. Imagine those mirrors were infinitely small, and you have an infinitely large number of them. What you have is just a really big reflector and Etendue still applies.
> 
> Semiman



I think you need to go back and study Etendue. Collecting from a point source, you can't collect more than the emitter throws from a point. Not too hard. 

An led emitter (a smallish square - perhaps .25 or .1 cm^2 in my experience) throws a dissipating square of light. Intercept it, focus it down to something smaller than that .25 or .1 cm^2 and we'll have a more energetic focal point. The sun throws a lot. Focus it down, and we'll have a _whole lot _of energy! 

-jk


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## mattheww50 (Oct 8, 2015)

I don't buy the 5500K limit for sunlight for a second. It is all about energy density. You can calculate the likely temperature from the energy being radiated assuming the object you are heating is roughly equivalent to a black body. It admittedly gets very difficult to achieve such high temperatures because the energy radiated by the black body goes up as T^4. The Stephan-Boltzmann Law tells you the temperature for a given amount of energy per unit area. 

See http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html#c1

As long as the amount of energy you can bring to bear isn't limited, neither is the temperature. There are other limits that come into play. Light is an electromagnetic wave, and if you make the energy density high enough, you exceed the dielectric strength of the medium (usually air), in which case you create a plasma. If you apply enough energy you can achieve temperatures far far higher than 5500k. At some point the black body has to be in equilibrium, i.e. energy radiated = energy absorbed. Every time I double the energy applied to the target, the temperature will go up about 19%. As long as I can keep finding ways to increase the energy delivered per unit area, the temperature will continue to increase.


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## SemiMan (Oct 8, 2015)

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## SemiMan (Oct 8, 2015)

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## RWT1405 (Oct 8, 2015)

Many won't be happy until they have the brightest light they can have, even if it only lasts 1 second and burns their hands off. Of course, most of these people use their lights as toys, not tools, but so be it.

For me I'm more worried about run time, beam pattern, etc., then to have a play toy, for nothing more then trying to show that "mine, is bigger then yours".


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## jmwking (Oct 8, 2015)

SemiMan said:


> It is not me who needs to understand Etendue. You can't focus a single LED or flat array of LEDs to something smaller than the LED AND have a spot brighter than the surface of said LED. Saying that you can does not make it so.
> 
> The sun is not a point source. It is spherical. You also can't focus to greater than the surface brightness. You can never focus is to beyond about 5500k since the suns emission is very close to a blackbody.



OK. As you like...


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## SemiMan (Oct 8, 2015)

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## SemiMan (Oct 8, 2015)

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## magellan (Oct 8, 2015)

SemiMan said:


> I would like it if Etendue did not exist ... but it does. If it did not, I could have a nice handheld 2,000 lumen flashlight with a nice 1" beam that never diverged. I can't though .... and the reason is Etendue. The scale is different from collecting the light of the sun, but the principles are not.
> 
> I have linked a very good article on Etendue that I have shared with others in the past to get them over this knowledge hump. Apologies I could not find it earlier, but it's internet is rather slow several miles over the Pacific.



I read the Wood article. Good stuff and I'm still digesting some of the details.

Correct me if I'm wrong (I'm not a physicist), but the technical details of Etendue aside, it seems obvious that you can't get more energy out of a system, whether optical, electrical, or mechanical, than you put in because of system losses. Again this is just basically the second law as you pointed out. You don't even have to understand Etendue. Otherwise we'd have things like perpetual motion machines, and we don't, and is why an optical system however sophisticated can't exceed the sun. Put another way, using a typical optical system, which is just using passive transmission (not talking about photomultipliers here), you can't get photons more energetic than the original source. This just seems like common sense and basic physics. Have I gotten anything wrong?


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## SemiMan (Oct 8, 2015)

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## magellan (Oct 8, 2015)

Okay, thanks, I will do that. But I noted the Wood article mentioned transmission losses. Is this not as important then?


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## WarRaven (Oct 9, 2015)

Good read still.
So not more, but near equal to source is possible?


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## CelticCross74 (Oct 9, 2015)

true 1000 lumen lights that we have today are more than enough to provide ample lighting for nearly any situation. The difference in the future say ten years from now will be cell technology and LED emitter tech. Both will advance steadily I predict 2016 to be a huge year for 18650 technology. Ten years from now I see 1000 lumen lights still being a standard yet will be capable of several hours to a day or more of maintaining highest output. LED tech ten years from now will be pretty nuts. Ultra tiny LED's that crank a couple thousand lumens and just do not get above a certain low temp.

I see LED lights that smoke HID lights. I see car headlights featuring high output LED's rather than any kind of bulb.


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## SemiMan (Oct 9, 2015)

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## WarRaven (Oct 9, 2015)

SemiMan said:


> Correct.


Remotely yet, ftw!
We're 93 million miles away, an AU!!!

With this swimming pool full of mirrors, we can make anything that sits on the lifeguards perch into plasma!


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## Overclocker (Oct 9, 2015)

CelticCross74 said:


> true 1000 lumen lights that we have today are more than enough to provide ample lighting for nearly any situation.



640k ought to be enough for anybody, right?


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## Rick NJ (Oct 9, 2015)

SemiMan said:


> As long as we are clear, no matter one reflector or 10 billion mirrors, you will never surpass 5500K. No matter logistics , placement, or anything else its not going to happen. This is laws of physics stuff not engineering.
> 
> 
> The same applies to lumens/watt. Hard limit that will not be exceeded, period .... Laws of thermodynamics, not engineering and not remotely related to chip density/computers, not at all.







SemiMan said:


> It's really more about conservation of entropy ... That or just simple geometry. It's not about controlling total energy more about the concentration of in an optical system.
> 
> I would suggest Googling a few more simple articles and try to find one that looks at the geometry as it will seem more obvious.



I don't get it, SemiMan, I am not agreeing with what you are saying.

I think first we should clarify if we talking theoretical or are we talking in practice. In your statement: "no matter one reflector or 10 billion mirrors, you will never surpass 5500K. No matter logistics , placement, or anything else its not going to happen. This is laws of physics stuff", I infer from that you are talking pure *theoretical*.

If you are talking pure *theoretical*, then *which Law(s) of Physics introduced that 5500K or 6000K limit?* Etendue applies to how the light spread based on the geometric arrangement of the sun and earth, *second law* of thermodynamic (entropy) doesn't matter at all in this evaluation since I will arrive at the same result with or without consideration to entropy.

Whereas, in my view, the *first law of thermodynamics (conservation of energy) is the critical one here*.

Let's get away from the word "magnifying glass" and use the more precise term *convex lens*. Mirror or lens doesn't matter. A concave mirror will do the exact same thing as a convex lens. A convex lens focus parallel light rays perpendicular to the lens to a point one focal length away from the lens. Lets agree that it is not a mathematical point but a point of some dimension. Lets just say the "point" is very very small - say 1mm^2, and the lens is say 314mm^2 (diameter of 20mm).

So, this 20mm lens collects the light falling on its area of 314mm^2, and focus it on 1mm^2. That is collecting at earth distance the energy of the sun falling on 314mm^2 and putting it onto 1mm^2. *How much temperature would increase from that energy* depends entirely on how the point's surface deals with that energy. If it convert just some of those energy to heat, then, the temperature rises.

By adding another mirror/lens at a new location (ie:different position from first lens), I am collecting the sun's photo energy falling where this new lens is, and focus that energy to the same 1mm^2 surface area. By the *first law of thermodynamics*, energy is conserved. So, I just added that energy from the new lens to that 1mm^2. Given more and more mirrors/lens, I added more and more energy to that point (again by the first law of thermodynamics). In theory, *given enough lens (and unlimited locations to put them), I can collect all the energy from the visible side of the sun* and focus all of them on 1mm^2. In this case, as I add more and more energy to that one point, the *upper limit of the temperature that point can reach is at the vaporization of surface/point* - if I focus it on water, it vaporize at 100C, so I sure as hack cannot get 101C at that surface. Surely water will reflect much of the photo energy away, but the lost to reflection can be compensated by increasing the number of lens each at different locations (ie:collect more energy to compensate for energy reflected away).

Lets just say I pick a material that vaporizes at 8000K, and that material I pick is able to convert 50% of the energy to heat and the rest reflected away. I surely can pump enough energy into that 1mm^2 enough to raise it to 8000K. What laws of physics can stop me from doing it when my upper limit is all of the visible side of the sun?

And staying on talking theoretical, since Etendue was brought into the discussion already, the optics can certain compensate for the geometry (angle of rays). Even light from a square die doesn't matter if the limit on emitter count and lens count are high enough.

My physics was a long time ago. Just the other day on this forum, I posted something I arrived at based on the "latent heat of water melting" I had in my mind. I was reminded my number was wrong: 1/1000 what it should be (mixed up Joule v KJoule in my mind). So, I do not rule out that some Physics have left me, after all, I got my master degree in Physics way back when Jimmy Carter was President. So it was a long long long time ago.

That said, I can't figure out "no matter one reflector or 10 billion mirrors, you will never surpass 5500K. No matter logistics , placement, or anything else its not going to happen. This is laws of physics stuff".

Enlighten me, which laws of physics are you citing?

Thanks
Rick


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## magellan (Oct 9, 2015)

Okay, now I'm really confused. LOL

It sounds like you're saying if enough radiant energy is converted to heat you can increase the temperature over that of the original source, in this case the sun.

It also sounds you're saying this depends on the nature of the surface and not just the optical system involved?


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## WarRaven (Oct 9, 2015)

Intense thread, my mind is spinning.
I love CPF!☺


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## more_vampires (Oct 9, 2015)

magellan said:


> Okay, now I'm really confused. LOL
> 
> It sounds like you're saying if enough radiant energy is converted to heat you can increase the temperature over that of the original source, in this case the sun.
> 
> It also sounds you're saying this depends on the nature of the surface and not just the optical system involved?



https://en.wikipedia.org/wiki/Reflectance

Also, there's quite a bit more to solar power than just optics. You could make an entire hobby out of just studying that.

Many cheap solar water heating designs amount to little more than a container or some pipes spray painted black and exposed to sunlight.

Like this:
https://www.northamericansolarstores.com/solar-thermal/

A lot of their designs are based on a absorbing outer layer and a reflective inner layer. I have one of their travel solar water boilers. Takes 8-20 minutes to do 2-3 cups of water, pretty awesome. The stock device comes with a plug with a hole in it for a steam line in case you wanted to distill your own water in the field. If you used the energy of the steam to generate electricity or used a peltier device to convert the heat to electricty and store it in the appropriate mechanism, we could theoretically run an arc welder and break 20000 degrees C *eventually*. Such a small device would take a massively long time to develop that kind of power, but that's what I'm getting at. That's the fallacy being presented thus far.

There are a great many, many solar devices of many, many designs all over the place worldwide in distributed networks. Power to the grid, use the power, you're burning the sun's energy.

WRT a system as I describe, there is no temperature or energy limit. It's as much as we can build out, design improvements notwithstanding. Anything less and you're using the wrong combination of technology and banging your head repeatedly on the same statements that don't really apply if you look at the big picture.

I'm more interested in the techniques of progress, not people saying "you can't do that!!" Focusing on the limited case of one component of a complex system and one instance of a device makes you blind to the forest of technology and expansive solar farms allowing us to vaporize zirconium oxide if we so choose.

It's like cutting down the tallest tree in the forest with..... *a red herring! *


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## SemiMan (Oct 9, 2015)

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## SemiMan (Oct 9, 2015)

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## SemiMan (Oct 9, 2015)

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## TEEJ (Oct 9, 2015)

I think that based upon the above thread posts, I could interpret this all to mean I could use falling water to exceed the temperature of the sun....by using the falling water to spin a wheel to generate electricity, and use the electricity to make a plasma, etc.



I did notice some confusion as to where the a fore mentioned 6k temp limit came from, and, the context was the surface temperature of the sun...meaning that (ONLY) if the SUN were the source, IT'S temperature was the limiting factor. Some posts indicated that they though the ~ 6k was a universal limit, and didn't realize the context was only applicable if that were the source's temperature.

There also seems to be some confusion between the difference in temperature, and ability to heat.

IE: A small area with more intense heat, may heat something larger _less well_ than a cooler, but larger surface area, source. A laser beam dot, on a pot of water, vs the same pot on a conductive burner, etc.

So, if you take a magnifying glass for example, which, when popping ants, etc, is NOT used to MAGNIFY the sun, its used to make the sun a teenier dot on the ant...as the focus point affects the effect.

IE: Move the lens in/out, and you can either GET a larger picture of the sun, or, a smaller one. If the sunlight striking the surface of the lens is concentrated into a small enough dot, on the unfortunate ant, the ant pops.

When you pop the ant, the temperature is not equal to the heat of the sun...no matter how hard to work to get the focus just right. You might be able to concentrate the BTU of the light that hit the lens though, into a smaller surface area you focus on...and that's what you're popping the ant with.

By making the area the sunlight strikes larger, you have more BTU to work with...but that's BTU, not temperature per se.

If you gather enough BTU, using optics, you can melt steel, etc...as that can be a lot of potential heat energy....hence solar foundries, etc, working.

I have a suspicion that there was an early disconnect on the Celsius and Fahrenheit units of measurement, and the fact that some data was in one, and some in the other units, was missed by at least one member....based upon the way the numbers were used.


If we combine the ideas presented, in summary:

The source IS a limiting factor for the temperature...whatever the source is. 

The total heating energy CAN be concentrated by gathering sunlight from a larger area, but, the larger quantity of heat will not be at a higher TEMPERATURE than the original source being focused.

If the energy is CONVERTED to electricity for example, sure, now we are not focusing, we are using electricity, and the equations and rules that apply to electricity, not light, come into play.


Does that help?


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## more_vampires (Oct 9, 2015)

TEEJ said:


> I think that based upon the above thread posts, I could interpret this all to mean I could use falling water to exceed the temperature of the sun....by using the falling water to spin a wheel to generate electricity, and use the electricity to make a plasma, etc.


Love ya TEEJ! Remember, never said how long it would take! :laughing:


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## SemiMan (Oct 9, 2015)

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## SemiMan (Oct 9, 2015)

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## Rick NJ (Oct 9, 2015)

magellan said:


> Okay, now I'm really confused. LOL
> 
> It sounds like you're saying if enough radiant energy is converted to heat you can increase the temperature over that of the original source, in this case the sun.
> 
> It also sounds you're saying this depends on the nature of the surface and not just the optical system involved?



re: "*It sounds like you're saying if enough radiant energy is converted to heat you can increase the temperature over that of the original source, in this case the sun.*"
*
Absolutely*. First law of thermodynamic dictate that energy is conserved - meaning energy cannot disappear. It can be converted into other forms of energy such as chemical energy (as in photosynthesis), electrical, so on. It can also be converted into matter E=mc2​.
So, as you dump more and more energy into that spot, the energy has to go somewhere such as emitting particles it creates - particles can be another photon in which case it would be emitting light. The energy that didn't go anywhere will heat up the material.

re: "*It also sounds you're saying this depends on the nature of the surface and not just the optical system involved?*"
*
Absolutely*. In fact, your optical system controls how much light (energy) is delivered to the spot, the material of the spot controls what it does with that light energy.
== A solar-panel absorbs some of the energy and turned it into electrical energy.
== A leaf on a tree during photosynthesis absorbed some of the sun light and convert it into chemical energy and stored the energy it as ATP.
== A white-painted road would reflect much of that energy away.
== A black surface road will absorb much of that energy and converts it into heat.
== A theoretical black body would absorb everything and turn it into heat.

But, the temperature will not exceed that of the vaporization temperature (smoke-point if you are dealing with cooking oil). At that point, your surface vaporized away and the photons has a clear path going beyond your collection point and keeps going. You have nothing left at that location to have a temperature on it - this is the same question as "now that your water in the pot boiled away, what is the temperature of the water in the pot?" You can of course contain the water in a bottle. The pressure will increase the boiling point temperature. The higher the pressure you apply, the higher the boiling point temperature. You can keep increasing until the pressure breaks the bottle.

Hope that made it clearer.

Rick


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## SemiMan (Oct 9, 2015)

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## Rick NJ (Oct 9, 2015)

SemiMan said:


> The problem with your argument is it is ALL ASSUMPTIONS about what you "can" do, but not based on the reality of what can be done, whether either theoretically or practically.
> 
> Here is the thing, you can't keep adding lenses and keep stacking them onto the same 1mm spot such that the intensity keeps increasing. It can't be done. There is no physical arrangement of the lenses such that you can actually accomplish this. You keep trying to focus a non point source into a point source with higher intensity with no other argument than you think it can be done. That is not an argument. Read some articles on Etendue, look at the geometry, and hopefully the concept will become obvious.



re: "*Here is the thing, you can't keep adding lenses and keep stacking them onto the same 1mm spot such that the intensity keeps increasing. It can't be done. *"

Why not? What physical law prevents me from doing it? It is all a matter of optics and arrangement. If a limit is imposed (such as all the lens must be of the same diameter and/or no mirrors can be used), then it is the nature of the selected optics but not a limit from a physical law.

A thought experiment using a "half sphere mirror" with a diameter say 10 solar diameter will clearly collect half the sun's light energy if that half-sphere mirror is placed close enough to the sun. You will loose some light as you need another mirror to direct that focused beam into a collector. Both "the other mirror" and the collector will block a portion of that light. But that lost is not relevant as clearly you don't need 1/2 the sun's energy to reach 8000K. The high energy collider reaches more than a million degree every time it is used without needing 1/2 the sun's energy.

So, you can replace that "half-sphere" with an array of mirrors and lens to focus that on to one spot. You can in fact make an array around the sun and put the upper limit to total capture of solar energy as in the Dyson Sphere.

The *first law of thermodynamics* said I can keep adding, and that is more proven than your "It can't be done" unless you cite more than what you have cited so far. So you have to pull on something stronger.

Sorry, I am unenlightened just yet.

Rick


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## Rick NJ (Oct 9, 2015)

SemiMan said:


> I think this just further confuses the issue.
> ...
> ...
> 1) Using purely optical concentration/reflection/refraction, and no conversion to other energy forms, whether it be electrical, chemical, or otherwise, you cannot, using the sun as a source deliver onto a surface, more than 67megawatts per square meter. It does not matter how big the reflector, or how many mirrors, it cannot be done.
> ...



SemiMan,

I accept that the arrangement of the optics will not be a cake walk, but it is surely permitted under all the applicable physical law - unless I overlooked some other applicable one. 

You need to cited another physical law why "it cannot be done." The first law of thermodynamic said I can add the energy delivered to the spot. The rules of arithmetic show me how they are added. So until then, I take the "laws of thermodynamic" as valid.

Rick


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## SemiMan (Oct 9, 2015)

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## SemiMan (Oct 9, 2015)

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## Rick NJ (Oct 9, 2015)

SemiMan said:


> If you refuse to learn about Etendue and to learn about Etendue and entropy limits and how they apply to the 2nd law of thermodynamics, then there is nothing I can do for you. I linked to a very good paper that described the basics in a very good way for what can be considered a complex topic. This is CPF, not a physics text book. It is not "me" who is saying it cannot be done, it is everyone who is knowledgeable in this subject area. I suggested a Google that I believe returns about 10,000 links. By those who work in this area, this is a well known limit, but that's okay, people keep trying to make perpetual motion machines all the time....
> ...
> ...



So what if I cannot do a perfect 100% efficient transfer. The amount of energy I need to heat 1mm*1mm (of some material) to 8000K is miniscule compared to the output of the sun. So second law of thermodynamic is not relevant here.




SemiMan said:


> ...
> ...
> As you add the power from all these mirrors, the amount you add gets less and less, no matter 100 mirrors or a billion. Eventually you will reach an asymptote on your target surface of delivered power per unit area, and it will never exceed the emitted power per unit area of the sun.
> 
> ...



As said above, the amount of energy I need is miniscule compared to the output of the sun. So I don't need it to reach 1. One ppm (part per million) of the sun's output is more than enough to raise any earthly material 1mm*1mm*1mm from absolute zero to 8000K many times over.

* *

After both undergraduate and graduate courses in thermodynamics, I have a reasonable understanding of 2nd law of thermodynamics. I wasn't looking for your help to understand thermodynamics. I had plenty of help when I was studying physics in college and graduate school as a physics major. So, instead of seeking your help to understand, I was hoping you can cite something that I overlooked.

You would be right in saying "I cannot collect more energy than the sun emit", but you are wrong in saying "I cannot concentrate that energy to increase the energy density beyond the sun's energy density."

That said, until you cite something other than the laws that doesn't apply, I will rely on the first law of thermodynamics and say "you sure as hell can add them".

However, I have an open mind...

Rick


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## magellan (Oct 9, 2015)

more_vampires said:


> https://en.wikipedia.org/wiki/Reflectance
> 
> Also, there's quite a bit more to solar power than just optics. You could make an entire hobby out of just studying that.
> 
> ...



Yes, it's very interesting. I know what you mean about the solar stuff as I've looked into it a bit myself. Also a friend is a technician at a peaker plant who has attended classes at the Ivanpah facility and he's been good enough to explain much of its operation to me.

It turns out the facility, although technologically impressive in some ways, isn't really viable economically. They're basically the most expensive plant in California by cost per kilowatt hour. If it weren't for all the laws giving them deductions and energy credits for being solar it couldn't survive.


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## Rick NJ (Oct 9, 2015)

SemiMan said:


> So you take the first law and ignore the 2nd law of thermodynamics?



*Speaking from the experience* of having teach college physics as a Teaching Assistant (graduate school students in physics paid to teach intro level physics), *this question deserves an independent answer*.

Yes, in this case, I should *ignore the second law* of thermodynamics. It is a matter of scale. Second law of thermodynamic basically said I cannot have perfect efficiency and Etendue basically said I cannot collect all the lights. They don't matter because I don't need that much. I need a very very very small percentage of the total output of the sun, so not being able to collect 100% here doesn't matter.

Yes, in this case, I should *take the first law* of thermodynamics. I am considering "making a larger one" by collecting many small ones. So here it is applicable to consider a rule on if I can add them, or not.

Rick


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## Rick NJ (Oct 9, 2015)

TEEJ said:


> ...
> I did notice some confusion as to where the a fore mentioned 6k temp limit came from, and, the context was the surface temperature of the sun...meaning that (ONLY) if the SUN were the source, IT'S temperature was the limiting factor. Some posts indicated that they though the ~ 6k was a universal limit, and didn't realize the context was only applicable if that were the source's temperature.
> 
> There also seems to be some confusion between the difference in temperature, and ability to heat.
> ...





SemiMan said:


> Except one only talks temperature when talking a black body radiator as the source. Radiant "brightness, luminosity" where all wavelengths emitted would be more accurate and universally applicable. An LED has a low surface temperature, but there is enough radiation for 2000-2500 kelvin spot temperature in a perfect system.
> 
> I don't think anyone was taking 5500 or 6000K out of context of the sun as the source.
> 
> I would not use BTU as the measure, as it's a measure of energy, and we are really talking about power (that said, I am pretty sure I used energy in this thread when I really should have used power).



*Bare in mind, color-temperature is not heat-temperature. *Color temperature is merely a mean to quantify the light's color. Another way is to quantify it by wave length.

Color temperature of moon light is about 4000K. At 4000K heat-temperature, even gold will melt. The color temperature of 4000K means the color of the light matches the color of the light from the theoretical black body heated to 4000K.

The surface temperature of the sun is about 5800K, but you don't have to heat something to 5800K temperature to get 5800K color light. Direct overhead sun light is about 5600K, daylight/overcast is about 6500K color temperature. The sun certainly didn't heat up or cool down based on if we have overcast sky above us.

Likewise, a 5000K led means the light has the color of the theoretical black body heated to 5000K temperature. It doesn't mean that the emitter (or any part of it) is at 5000K temperature.


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## magellan (Oct 9, 2015)

Guys, it seems there's a disconnect here which SemiMan has pointed out. I don't pretend to understand all the physics, but I've followed the discussion here, and the learned posts by all the participants, and have absorbed a good deal of it. Maybe someday I'll understand the rest of it. But my understanding, and even whether anybody else here understands or accepts his explanations are really beside the point, because SemiMan has pointed out that this isn't his opinion; it's standard knowledge or accepted science in optics by the experts who say it can't be done, and he's pointed out that there are dozens of articles out there on it if anyone is interested that will explain it. 

I'm no physicist, so I could be wrong, but I was a scientist in another complex area once, and I know that if you don't know and understand the standard literature in an area then you're really not even qualified to have an opinion about it until you do. The debate here, however interesting and learned, is irrelevant. If he's right about the experts' opinion, which I have no reason to doubt, then people need to step back, read the articles, and then come back to the discussion armed with this new knowledge and see if they still feel the same way.

Just my two cents and others mileage may vary. But this is how things were done when I was in academia and people were discussing science. Maybe things are different now, but I don't see as that would be an improvement.


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## magellan (Oct 10, 2015)

SemiMan said:


> I think this just further confuses the issue.
> 
> Let's take heat, temperature, even energy out of the equation and use the following terms, "Emitted power per unit area", and "Delivered power per unit area".
> 
> ...



This is sorta where i was today thinking thru this issue. I recall reading years ago that the sun puts out about 10,000 horsepower per square yard of surface area. However, the sun is 93 million miles away, and the inverse square law is going to kill you here. Standing on the surface of the earth, no collector of any size is going to allow you to exceed what is emitted from the sun's surface at the bottom of the photosphere. Not even if you built a Dyson sphere and captured all the energy that way. Again, this just seems common sense to me, notwithstanding the fact that there are some things about Etendue I'm still digesting.


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## leon2245 (Oct 10, 2015)

Lol everyone may collect their participation awards now; thread wrecked.

Courtesy: semi man.


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## xzel87 (Oct 10, 2015)

Turned out pretty complicated I would say. Regardless of the physics and facts posted, I don't think it's gonna top out soon. Back in the Middle Ages who would've thought mankind could go to space?. Maybe 500 years later from today we'd be shooting lights from our fingers.


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## magellan (Oct 10, 2015)

xzel87 said:


> Turned out pretty complicated I would say. Regardless of the physics and facts posted, I don't think it's gonna top out soon. Back in the Middle Ages who would've thought mankind could go to space?. Maybe 500 years later from today we'd be shooting lights from our fingers.



God, I hope not. That would make all the money I've spent on flashlights superfluous.


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## Rick NJ (Oct 10, 2015)

magellan said:


> Guys, it seems there's a disconnect here which SemiMan has pointed out. I don't pretend to understand all the physics, but I've followed the discussion here, and the learned posts by all the participants, and have absorbed a good deal of it. Maybe someday I'll understand the rest of it. But my understanding, and even whether anybody else here understands or accepts his explanations are really beside the point, because SemiMan has pointed out that this isn't his opinion; it's standard knowledge or accepted science in optics by the experts who say it can't be done, and he's pointed out that there are dozens of articles out there on it if anyone is interested that will explain it. ...
> ...



re: "Guys, it seems there's a disconnect here which SemiMan has pointed out...because SemiMan has pointed out that this isn't his opinion; it's standard knowledge or accepted science in optics by the experts who say it can't be done..."

I reviewed what he pointed out, and concluded that what he pointed out are not relevant to this situation. The net net of what he pointed out is that you cannot collect 100% of the light, and you cannot collect at 100% efficiency. He then used that to support "it cannot be done".

I need a mere 0.00000000000001%. So, not being able to get 100% does not matter here. So, it cannot be used to support his conclusion "it cannot be done."

*As I say, I am open-minded. There could be things I overlooked.* Until another physical law is cited (other than "can't get 100%"), or point out what I might have overlooked. *His conclusion of "cannot be done" is not supported by actual applicable law*.

Rick

Footnote:
Details of why is what he pointed out not relevant?
Some numbers first:
== The total output of the sun reaching earth is *170,000,000,000,000,000 joules/second*.
== To heat a gram of *water up one degree is around 4 joule*.
== Liquid sodium is often use for reactor transer. It takes *<2 joule *for 1gm of sodium to heat up 1C.
== So, to heat up 1gram of something like sodium by 8000K takes *less than 16,000joule*.
== remember, the collection point is small. I was using 1mm*1mm for discussion.
That I cannot collecting 100% of *170,000,000,000,000,000 joules* hardly matters when I all need is *16,000 joules* per gram.

I need a mere 0.00000000000001%. So, not being able to get 100% does not matter here.

Since what he cited are true but not relevant. So his is using "cant get 100%" to say "so it cannot be done" therefore is invalid.


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## SemiMan (Oct 10, 2015)

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## SemiMan (Oct 10, 2015)

xzel87 said:


> Turned out pretty complicated I would say. Regardless of the physics and facts posted, I don't think it's gonna top out soon. Back in the Middle Ages who would've thought mankind could go to space?. Maybe 500 years later from today we'd be shooting lights from our fingers.



Nah, we will all live in the matrix and have whatever virtual flashlight we desire.


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## beaconterraone (Oct 10, 2015)

We've got quite a ways to go:

https://www.youtube.com/watch?v=EvI_FYarYIY


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## magellan (Oct 10, 2015)

Rick NJ said:


> re: "Guys, it seems there's a disconnect here which SemiMan has pointed out...because SemiMan has pointed out that this isn't his opinion; it's standard knowledge or accepted science in optics by the experts who say it can't be done..."
> 
> I reviewed what he pointed out, and concluded that what he pointed out are not relevant to this situation. The net net of what he pointed out is that you cannot collect 100% of the light, and you cannot collect at 100% efficiency. He then used that to support "it cannot be done".
> 
> ...



Okay, that's great stuff, and I've learned a lot from both of your posts, but if Etendue is considered standard then you're going against well accepted opinion. Correct me if I'm wrong, but he has stated this is a well understood issue, Etendue is applicable, and that he's not saying anything different from that.

Is there a optical physicist in the house? LOL

I read Nobel Laureate Max Born's book on optics years ago but I'm a little rusty.


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## magellan (Oct 10, 2015)

Okay, all this discussion of optics has reminded me of an old problem, and maybe the learned experts here can help me. Apologizing in advance for going off topic, but it is a problem in optics which we have been discussing here.

I used to have an interest in photography and photographic lens design, and some years ago I was reading a journal article on the problem of color correction and color balance in lenses. I believe this was a standard 50mm four element design, so nothing unusual. The author pointed out that if you take the Laplace transform of the spatial frequency response of the lens system, that it turns out that the lower spatial frequencies rather than the higher spatial frequencies are more important in correcting chromatic aberrations, which doesn't make any sense to me at all, since the higher spatial frequencies are associated with greater resolution than the lower spatial frequencies, and as far as I knew, you always want higher resolution in a lens system. (Note we are using the Laplace transform into the time domain here rather than Fourier analysis in the frequency domain). However, higher resolution doesn't seem to be associated with color accuracy. As I said, this makes no sense to me, so if there's a physicist here with some understanding of this kind of optics I was wondering if they could explain why this is.


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## mattheww50 (Oct 10, 2015)

TEEJ said:


> I think that based upon the above thread posts, I could interpret this all to mean I could use falling water to exceed the temperature of the sun....by using the falling water to spin a wheel to generate electricity, and use the electricity to make a plasma, etc.
> 
> 
> 
> ...


There is a rather gaping hole in your argument. If it was true, then exercises like trying to ignite deuterium pellets to get them to fuse in Helium would be impossible (National laser ignition facility at Livermore CA). The temperatures required are far higher than are normally attainable on earth and clearly do no exist within the laser itself. It can be done however by combining multiple optical systems, each of which can deliver power. While each optical system has limitations, by using multiple optical systems and multiple energy sources, you can in fact place far more energy on the target than any single energy source has. As long as you can find ways to apply more energy per unit area, Stephan-Boltzmann will tell you how hot you can make things. So while a single optical system may not be able to exceed the energy density on the surface of the sun, multiple optical systems can each provide roughly the same energy density, and Stephan-Boltzmann says the only limitation on the temperature is how much energy you can bring to bear.


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## magellan (Oct 10, 2015)

mattheww50 said:


> There is a rather gaping hole in your argument. If it was true, then exercises like trying to ignite deuterium pellets to get them to fuse in Helium would be impossible (National laser ignition facility at Livermore CA). The temperatures required are far higher than are normally attainable on earth and clearly do no exist within the laser itself. It can be done however by combining multiple optical systems, each of which can deliver power. While each optical system has limitations, by using multiple optical systems and multiple energy sources, you can in fact place far more energy on the target than any single energy source has. As long as you can find ways to apply more energy per unit area, Stephan-Boltzmann will tell you how hot you can make things. So while a single optical system may not be able to exceed the energy density on the surface of the sun, multiple optical systems can each provide roughly the same energy density, and Stephan-Boltzmann says the only limitation on the temperature is how much energy you can bring to bear.



Okay, in that case there should be examples in the lab where higher temperatures than the original source were achieved using optical means?


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## WalkIntoTheLight (Oct 10, 2015)

Rick NJ said:


> You would be right in saying "I cannot collect more energy than the sun emit", but you are wrong in saying "I cannot concentrate that energy to increase the energy density beyond the sun's energy density."
> 
> That said, until you cite something other than the laws that doesn't apply, I will rely on the first law of thermodynamics and say "you sure as hell can add them".




Saying it's so, doesn't make it so.

Scientific consensus is that you can not exceed the energy density of the sun using optical methods. So, if you've somehow come up with an amazing way to do it, then it's up to you to prove it or cite peer-reviewed scientific evidence for it.

And while you're at it, please post your plans for free energy or a perpetual energy machine. Because that's exactly the kind of pseudoscience where this thread has gone.


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## WalkIntoTheLight (Oct 10, 2015)

mattheww50 said:


> There is a rather gaping hole in your argument. If it was true, then exercises like trying to ignite deuterium pellets to get them to fuse in Helium would be impossible (National laser ignition facility at Livermore CA). The temperatures required are far higher than are normally attainable on earth and clearly do no exist within the laser itself.



That's completely different. They're using multiple lasers, and projecting them onto a common point. They are not using a single emitter source, such as the sun, and optically trying to somehow project it down to a point hotter than the surface of the sun.


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## mattheww50 (Oct 10, 2015)

There is absolutely no difference between multiple lasers and multiple optical systems focusing the energy. Suppose I take two optical systems on opposite sides of the solar system and focus them to a single point on earth. The Sun is a single emitter isn't it? Is that really any different that using two different laser systems? For that matter I can place multiple optical systems in orbits each of which see's a different portion of the sun, the luminous energy on the solar surface is claimed to be about 67MW/ M^2.
If I can focus the beam from different non-overlapping portions of the sun, I have a 67MW energy from several more or less independent sources that i can focus. The bottom line is the limitations are for single optical systems. If you can collect energy from different optical systems and then combine them, all bets are off. The more optical systems I can make line up, the more energy I can focus,and Stephan-Boltzmann says as long as i can increase the input power, the temperature is going to go up.


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## SemiMan (Oct 10, 2015)

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## magellan (Oct 10, 2015)

I've read a few of the articles at this point and it is making more sense.

Some things in optics don't seem to make intuitive sense, such as the lens design problem I mentioned where the lower spatial frequencies were more important than the higher ones in correcting chromatic aberration.


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## Rick NJ (Oct 10, 2015)

magellan said:


> ...
> Is there a optical physicist in the house? LOL
> ...



Actually, it is not the optical side that I challenged the assessment. It is the energy side. The optical side is fine, it applies. That however does not extend to the energy side. In truth, a material scientist will be good bit more useful for this discussion than an optical physicist.

That is why I draw the line very clearly in one of my replies, *the optics controls the amount of light collected*. The *material on which the light hits controls what the max temperature (or color of light it re-emit, or energy absort...)*. So, the collection point may not be brighter, but it sure can be hotter.

There is also *a confusion by some* that direct overhead sunlight being ~5600K color temperature and mixed that up with heat-temperature of ~5600K. Yes *they happened to be the same but they don't have to be the same*. (Not to say anyone here did the mix up). On another thread, I pointed out that cloudy/overcast day is actually about 6500-6800K, the sun did not get hotter because we have overcast sky. *Focusing more light will not change the color of the light*, so the color-temperature remains the same but the heat-temperature would rise.

I think looking at this as an optical problem, and possible mix up between color-temperature and heat-temperature caused much of the confusion.

That said, I eager awaits someone pointing out things I might have overlooked... After all, my physics is old... long long time ago...

Rick


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## WalkIntoTheLight (Oct 10, 2015)

Rick NJ said:


> That is why I draw the line very clearly in one of my replies, *the optics controls the amount of light collected*. The *material on which the light hits controls what the max temperature (or color of light it re-emit, or energy absort...)*. So, the collection point may not be brighter, but it sure can be hotter.



I don't think so, unless there's a chemical reaction taking place on the material you're heating. Anything hotter than 5500 degrees will just be radiated away. You can't put more heat into a substance than what you're heating it with.



> There is also *a confusion by some* that direct overhead sunlight being ~5600K color temperature and mixed that up with heat-temperature of ~5600K. Yes *they happened to be the same but they don't have to be the same*.



The sun, being very close to a blackbody source, has the same surface temperature and color temperature (because that's how it's defined). But, yes, we're talking about the surface temperature of it, if it's unclear. More precisely, I suppose we're talking about the surface radiance, or energy density, or something like that. But, I think we know more-or-less what we're talking about.


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## FRITZHID (Oct 10, 2015)

The basic application is taking X ft² of solar energy and using any and/or all means available to direct that said energy to a very small point, much smaller then the collected area AND/OR the emitted area, hence CONCENTRATING said energy by a factor of magnitude. This is a very common practice. Used every day in many many applications.
I.E. a 5kw Mitsubishi co2 laser has an initial beam diameter of approx 3" (that would be the original emitting surface area) and using active beam correction mirrors AND lens(s), this is concentrated down to a point that is smaller than a human hair, at a relative surface "brightness" that is WELL over the original beams. This applies to solar power as well.
"Can you use optics to take X amount of solar energy and concentrate it down to a point that exceeds the original emitted surfaces output?" The answer is simply yes, you can. It's done every day. From cutting metal to delicate eye surgery.


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## TEEJ (Oct 10, 2015)

I don't think that's true.

The eye surgeon to use that example, has a laser...and that laser has a emitter temperature.

The QUESTION has been whether you can OPTICALLY (With a lens system) make your "dot" form that laser hotter than the original laser's source.

So, yes, you can take the temp of the sun (Yes, the 6k was a reference to the degrees C as apposed to degrees F used earlier), and use lots of concentrators...but the point semiman was making is that the LENS part is not able to make the dot hotter.

All the larger collection points are doing is contributing to the power (I used BTU as I was using a burner vs laser as a cook top analogy).

So, more energy, absolutely.

But if you are saying that a series of lenses, the way a magnifying glass lets you pop an ant even though the ambient temp is only 75º F, by allowing the sunlight that hit the glass to be concentrated into a smaller dot...no, it can be a hell of a lot HOTTER than ambient for sure...but, there's no way to LENS the energy to a hotter temp than the original source.


All of the counter arguments have really been talking about the energy being converted by non-optical/lens-based methods...and then talking about the total energy.


Semiman's example about the unit area, I thought was applicable.

If the sun is emitting X energy per square meter or whatever...on its surface...and, we wait patiently for that to take the 8 minutes or whatever to reach us, and then collect a lot of area of it, sure, we can take the larger area, concentrate it into a smaller area, and get a nifty ant popper.

The ant will not be popped at the temperature it WOULD HAVE been popped at if on the surface of the sun, it will be popped at a cooler temperature than that.

So, Semi is NOT saying that you can't collect from enough of an AREA to get a sheet load of heat energy, and, that you can't then concentrate that into a SMALLER area to magnify it...

...just that the limit of that magnification, using lenses, is the original temperature. (NOT energy, temperature)


You don't need the temp of the sun to melt through most metals, a few thousand degrees typically cuts it.




So, as lumens ≠ temperature, I think the lumens thing has a way to go yet.


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## magellan (Oct 10, 2015)

Rick NJ said:


> Actually, it is not the optical side that I challenged the assessment. It is the energy side. The optical side is fine, it applies. That however does not extend to the energy side. In truth, a material scientist will be good bit more useful for this discussion than an optical physicist.
> 
> That is why I draw the line very clearly in one of my replies, *the optics controls the amount of light collected*. The *material on which the light hits controls what the max temperature (or color of light it re-emit, or energy absort...)*. So, the collection point may not be brighter, but it sure can be hotter.
> 
> ...



Yes. Well, that is apparently the crux of the matter. The optics seem to be saying one thing and you seem to be saying another. I think the next logical step would be if anyone knows of an example where an optical system has produced a higher temperature than the original source. Do you know if this has been done? If what you're saying is possible then surely someone would have done it by now. Otherwise we simply have a plausible seeming argument, or perhaps an intriguing theory, with no demonstrable result. As someone once said of the Nobel Prize, you don't get it for having a beautiful theory; you get it for being right--the history of science being littered with beautiful theories killed by ugly little facts. 

Also, I do not understand your statement that a materials scientist would be more relevant at this point than an optics expert. Aren't we in fact discussing what's possible with an optical system? And whether or not such a system could do what you and others have claimed? I don't disagree that you might be able to trigger a reaction that is hotter in some material, but that is separate from the question of whether purely with optics you could generate a higher temperature than the original source. We're not talking about lighting magnesium with a match here.

As a matter of fact, although I'm not much of an optics expert, I do know something about materials science, and I know of nothing that would support such a claim unless as I said you're speaking of a reaction that is separate from the beam itself. I don't claim to be a world class expert in the subject, though, so if you do know something about it, I'm willing to listen. Otherwise this just seems like a red herring. I was with you up till now, but you just lost me.


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## Rick NJ (Oct 10, 2015)

WalkIntoTheLight said:


> I don't think so, unless there's a chemical reaction taking place on the material you're heating. Anything hotter than 5500 degrees will just be radiated away. You can't put more heat into a substance than what you're heating it with.



I think we agree on the optical part. How the material deal with the photon is the key point here. The photon itself doesn't have a temperature. It is just a bundle of energy of certain amount. Once the photon hits the material, it ceased being an optical problem.

An electron in an atom can absorb a quantum (a photon of that amount of energy) and move to the next level. It could then re-emit a photon with that energy and drop back down a quantum level. Another common scenario is, before re-emitting and drop back down, it could absorb yet another quantum of energy and move up again. So when it re-emit a photon, that single photon can consist of the first and the second quantum. It will be emitting higher energy photon than it absorb.

So how the material deals with the energy it absorb is the key that controls how much it would heat up. So far, I can't think of a physical law that prevents it from heating up till vaporization. It sure would be nice if there is a material science guy here. Optical guy (as proposed earlier) is nice, but we are not arguing about that.



WalkIntoTheLight said:


> The sun, being very close to a blackbody source, has the same surface temperature and color temperature (because that's how it's defined). But, yes, we're talking about the surface temperature of it, if it's unclear. More precisely, I suppose we're talking about the surface radiance, or energy density, or something like that. But, I think we know more-or-less what we're talking about.



We are in agreement, we are talking about the energy density at the collection point. But the word temperature is in color temperature as well as in temperature (of heat). I can discern some confusion there from some of the posts here.


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## Rick NJ (Oct 10, 2015)

magellan said:


> ...I think the next logical step would be if anyone knows of an example where an optical system has produced a higher temperature than the original source. Do you know if this has been done?
> ...



Yes. I have read articles about solar arrays creating >10,000C at collection point. But they are from news magazines and not science magazines so they lack the scientific details.

We do need an expert in the field. Some here are emphatic about it cannot be done. I have reasonable education in science, and I cannot see any physical law stopping it from happening. 1st law of thermodynamics said the energy will conserve, so it must. If you dump more and more energy into it, it's energy density must increase unless radiated away some how. Until someone can cite some physical law(s) to the contrary, or points out specific laws that forces the material to radiate all energy over X...

So, as I said, I am open minded...


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## magellan (Oct 10, 2015)

Okay, very good. I'm open minded as well, but I thought we were discussing what could be done intrinsically with optics alone. If we're all in agreement about that I think that is all SemiMan was saying. Now the discussion has moved onto what seems clearly to be a separate issue where the material science could be relevant, and where weird quantum phenomena could create strange effects. I just want to make sure we're not muddying the waters before settling what I thought was the original point of the discussion.


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## Rick NJ (Oct 10, 2015)

magellan said:


> Okay, very good. I'm open minded as well, but I thought we were discussing what could be done intrinsically with optics alone. If we're all in agreement about that I think that is all SemiMan was saying. Now the discussion has moved onto what seems clearly to be a separate issue where the material science could be relevant, and where weird quantum phenomena could create strange effects. I just want to make sure we're not muddying the waters before settling what I thought was the original point of the discussion.



On pure optical, I have no disagreement. I did get that we are talking pure optical.


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## magellan (Oct 10, 2015)

Rick NJ said:


> Yes. I have read articles about solar arrays creating >10,000C at collection point. But they are from news magazines and not science magazines so they lack the scientific details.
> 
> We do need an expert in the field. Some here are emphatic about it cannot be done. I have reasonable education in science, and I cannot see any physical law stopping it from happening. 1st law of thermodynamics said the energy will conserve, so it must. If you dump more and more energy into it, it's energy density must increase unless radiated away some how. Until someone can cite some physical law(s) to the contrary, or points out specific laws that forces the material to radiate all energy over X...
> 
> So, as I said, I am open minded...



Yowser, 10,000C? Excuse me if this seems a dumb question, but what material are they using for a collector? Right now the material with the highest melting point is a hafnium, nitrogen, carbon compound at over 7400 degrees F or about 4100 degrees C.


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## jmwking (Oct 10, 2015)

Interesting solar panel paper:

http://arxiv.org/ftp/arxiv/papers/1207/1207.3893.pdf


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## magellan (Oct 10, 2015)

I'm reading it. Yes, very interesting. 

They talk about a cell reaching the temperature of the sun; however no photovoltaic energy conversion occurs at this temperature.

Yeah, that's because your solar panel just vaporized. LOL


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## leon2245 (Oct 11, 2015)

Paging Dr. Semi, Dr. Semi you have a telephone call at the front desk.


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## delus (Oct 11, 2015)

*Making Pig Fat into a Laser*



xzel87 said:


> Maybe 500 years later from today we'd be shooting lights from our fingers.



500 years is too long.

Making Pig Fat into a Laser
Researchers have created self-contained cellular biolasers. http://www.technologyreview.com/news/539696/making-pig-fat-into-a-laser/


More seriously, we've got a long, long way to go before lumens top out in a handheld device.

Battery design is getting ultra-mega research money in all corners of the planet. A huge breakthrough in the near future is not likely, but if there is one it will probably involve... Nano.

Nano tech is still a relatively new field and many avenues of research remain undiscovered.. Any number of advancements could be made as researchers are under pressure to bring commercially viable products out of the lab.
We've seen quantum tunneling composite in flashlights already. 
Quantum dots added to LED's may be something we see very soon. http://www.ece.utoronto.ca/news/engineered-hybrid-crystal-opens-new-frontiers-for-high-efficiency-lighting/ 

Lasers can be more efficient than LED. Some kind of scattering lens, or a huge number of micro-lasers could be a breakthrough, and suddenly we're throwing LEDs away. I'm no laser scientist, but I don't see why something like this is not being done already.

My point is... !!! SCIENCE !!!!


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## WalkIntoTheLight (Oct 11, 2015)

magellan said:


> Yowser, 10,000C? Excuse me if this seems a dumb question, but what material are they using for a collector? Right now the material with the highest melting point is a hafnium, nitrogen, carbon compound at over 7400 degrees F or about 4100 degrees C.



I think you're dealing with plasma at that temperature.

In any case, I'd have to see a peer-reviewed paper in a scientific journal before I believe someone has broken the laws of physics/optics.


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## SemiMan (Oct 11, 2015)

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## SemiMan (Oct 11, 2015)

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## SemiMan (Oct 11, 2015)

*Re: Making Pig Fat into a Laser*

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## SemiMan (Oct 11, 2015)

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## SemiMan (Oct 11, 2015)

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## magellan (Oct 11, 2015)

"Here is the thing ... the optics cannot compensate for the geometry, angle of rays such that the intensity increases ... outside of the optic (more on that in another post). If those emitters are all placed on a flat plane or outwards curving, then whether one emitter or 10 million emitters, they still have a a whole, a set Etendue and adding more LEDs does not decrease the Etendue, it remains essentially the same."

Having delved into this a bit further with other articles, and reread many of your posts, I now get this pretty well at this point I think. The problem is it's not intuitively obvious. Or at least it's not intuitively obvious to me, but then I don't claim to be a Stud McMuffin when it comes to the physics. But I'm at least literate on the subject and I can learn. So I've learned a bit. This seems to be the sticking point for most other people, too, though, but it's the kicker. And if you don't get it you're just going to keep going unproductively down the same wrong path.

I want to thank you for all the time and effort you've put into this. You have more patience than I. I'm primarily a neurobiologist and brain scientist and sometime biophysicist by training, and you wouldn't believe the nonsense you see otherwise highly intelligent people spouting about the brain and the mind's capabilities, including such giants as Roger Penrose who should know better. But that's a whole different story and I don't want to go too far off topic. But if people like him can go wrong I suppose anybody can.


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## SemiMan (Oct 11, 2015)

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## WalkIntoTheLight (Oct 11, 2015)

SemiMan said:


> 1) It is quite theoretically possibly to create an LED that can be concentrated to beyond the surface brightness of the LED. After all, a solid state laser is in some ways a special case of an LED. IF you could create an LED with 0 emission angle, i.e. pretty much a laser, then there is no theoretical limit to the concentration. Most current LEDs approximate a lambertian source, but practically are not. The ones with domes are closer, domeless tend to be wider angle. As the emission angle is <(2 * pi) steradians, i.e. the maximum for a single sided emitter, in theory, there is a degree of freedom while maintaining Etendue and hence there is the potential to concentrate an LED to a high target surface brightness.



That's interesting. I guess a laser diode is a good example of this?

But, is it possible to do this with ordinary LEDs used in flashlights, such as a standard XM-L2? In other words, bring the topic way back to the original source of (mis)information, could you focus an LED flashlight to get a brighter hot-spot than the LED surface brightness? i.e., light paper on fire, etc.

I thought the answer was no, but now you're starting to confuse me.


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## SemiMan (Oct 11, 2015)

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## magellan (Oct 11, 2015)

"3) In my posts, you will notice that I said you cannot project an increased surface intensity onto a target, than the surface intensity of the sun, using the sun as the source of course. That is true. However, there is a special case where you can have a higher intensity in the beam than what is present at the suns surface. That is within an optical element with a higher index of refraction than what exists at the exit of the source. So, within a lens element itself, you can exceed the surface intensity of the sun. If you immersed a target within that optical element, it will experience an intensity higher than that are the surface of the sun."

I was wondering about this in the case of some very specialized lens systems I know about. Applied Materials uses them to make their chip etching machines. They are guaranteed to have zero optical distortions, which I still find mind boggling, but anyway, they are used by companies like Intel, the big chip making giant, for etching computer chips. Since they are etching micron size channels, obviously they have to be very accurate. Anyway, these lens systems are made by Hasselblad I believe and are used in these chip etching machines, which can cost in the tens of millions of dollars. They have up to 18 elements and are engineered by ray tracing methods since there is no analytical solution to a lens system that complex, and just the lenses cost over a million dollars apiece. That was 20 years ago before I retired. Anyway, the only reason I know about these is that I used to work in the semiconductor industry. Possibly something like that could do what you are suggesting.


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## SemiMan (Oct 11, 2015)

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## magellan (Oct 11, 2015)

Correct. In my day those weren't around yet. But the technology has of course improved.


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## Rick NJ (Oct 11, 2015)

magellan said:


> Yowser, 10,000C? Excuse me if this seems a dumb question, but what material are they using for a collector? Right now the material with the highest melting point is a hafnium, nitrogen, carbon compound at over 7400 degrees F or about 4100 degrees C.



It was in the news and not science magazine or scientific paper. So I have no idea. Most news site writers are not exactly PhD's. They report the stuff as "oh-wow".

I just took mental notes "that's interesting" because I was wondering not what the material was, but how it was measured, if it was projected or actual. But not interesting enough for me to dig further.

Rick


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## 2000xlt (Oct 11, 2015)

well BMW has developed laser headlights on their i8,,Now that technology would be something pretty damn awesome in a flashlight


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## idleprocess (Oct 11, 2015)

2000xlt said:


> well BMW has developed laser headlights on their i8,,Now that technology would be something pretty damn awesome in a flashlight


I gather that laser diodes are poised to see some big jumps in efficiency that may have them rivaling LED technology in terms of efficiency in another decade or so.


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## 2000xlt (Oct 11, 2015)

if you have not seen the article,,iirc each headlight had 3 diodes..

http://wot.motortrend.com/bmw-shows...lights-and-dynamic-lightspot-work-126103.html


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## magellan (Oct 11, 2015)

I just reread your post. You said it has to be within the lens itself and so anything exiting can't exceed the intensity of the original source. And even within the lens, it can't exceed the temperature of the source? Is that right?


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## SemiMan (Oct 11, 2015)

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## magellan (Oct 12, 2015)

Okay, thanks.


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## bykfixer (Oct 14, 2015)

New technology is just over the horizon. 

If/when it becomes economially feasible, we'll see it in our homes, cars and yes flashlights...

But right now the initial offerings are about as exciting as DOS.


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## SemiMan (Oct 14, 2015)

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## bykfixer (Oct 15, 2015)

It's easy to find that answer on the internet.


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## SemiMan (Oct 15, 2015)

I can only take that as mythical tech as nothing near feasible is going to make much of a difference in LEDs or batteries and nothing alternate to LED either.


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## more_vampires (Oct 15, 2015)

The problem with cool new tech is that a maker is going to need a financial reason to implement it.

It's like the solar panels on satellites. They rock, but the price point dictates that there's not going to be a build-out of a terrestrial field of these any time soon. Instead, the price point of output per unit is considered.


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## SemiMan (Oct 15, 2015)

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## more_vampires (Oct 15, 2015)

SemiMan said:


> No, but they find "interesting" economical implementations, i.e. the solar cells used in concentrator arrays are as efficient *as anything ever made.*



...yet.  Tech is a moving target.


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## bykfixer (Oct 15, 2015)

SemiMan said:


> I can only take that as mythical tech as nothing near feasible is going to make much of a difference in LEDs or batteries and nothing alternate to LED either.



It's real. It's in production. I've spoken about 2 of them here at cpf.

But like Bic vs Scripto, or VHS vs Beta, Mac vs Windows, the market will shake things out.


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## more_vampires (Oct 15, 2015)

bykfixer said:


> It's real. It's in production. I've spoken about 2 of them here at cpf.
> 
> But like Bic vs Scripto, or VHS vs Beta, Mac vs Windows, the market will shake things out.


Wasn't there a report a year or two ago of an LED emitter tech being developed that harvested some of its energy from ambient heat?

There was a lot of hooplah and argument concerning the violation of Conservation of Matter and Energy as I recall. However, something as simple as that could shake up the whole lumens per watt WRT energy from the battery. The idea was more like adding an auxiliary energy source "booster" to the circuit.

If XXX lumens/watt is the end and that's it, then all we must do is harness the watts from somewhere other than the battery. Or supercapacitor, whatever it is we'll be using 20 years from now. 

Lumens from heat isn't so crazy. We have thermoelectric devices as it stands. Rather than run a Peltier thermoelectric device as active cooling, we'd basically wire it to feed the energy harvested from heat differential back to the LED. A regenerative system, similar in concept to things like regenerative braking. The limit in the LED case is the heat that's there.

Presto! We just beat another limit. Too bad that I suspect that LED heat tech is a long, long way out if it ever shows up at all.


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## bykfixer (Oct 15, 2015)

Not being a rocket scientist, as best as I can tell the LED is here to stay, it's just where the energy is derived from. 
So with all things being equal it seems that same output is being explored with a lot less energy required. 

Say 100 watt bulb illumination with 1/2 the energy required of the current LED technology. Or as little as a third of the watts to drive a bulb (if you were) as the cfl or led could be available at your local big box store as soon as next year.

But what I was getting at in general was that when those emitters can be had for say...$6-8 each or say a 6 pack for $20...that's when it'll become as viable to flashlights as the LED was back when folks had a choice between a typical 6p or the new LED model.

And that's when all you wiz-kids will figure out how to drive those new techs to their max and end up with a lot more lumens...then when heat becomes an issue...you know it will then too...maybe by then the heat output will be part of the energy source.

In addition flexible emitter strips are also just around the corner. Can you imagine someone like Vihn with an LED emitter that can be shaped?

A Vihn tweaked flexible emitter with a McCliesch reflector?

And when Mr. Malkoff sinks his teeth into it...

No telling what the US military is working on that we don't know about. Something tells me they aren't spending most of their time in the space station growing zero gravity tomatoes or playing poker all day...


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## more_vampires (Oct 15, 2015)

> In addition flexible emitter strips are also just around the corner. Can you imagine someone like Vihn with an LED emitter that can be shaped?



A "reflector" that also emits light in addition to the main emitter? Yes, please! How the heck are we going to shape that beam? Don't care, we'll figure it out somehow!

Parabolic emitters! Now *there* is an idea!


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## bykfixer (Oct 15, 2015)

Geez, ya talk about TIR....


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## SemiMan (Oct 15, 2015)

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## bykfixer (Oct 15, 2015)

^^ what?

You lost me about 4 sentences in.

Re-read it 9-10 times...

Guess I won't bother reading on the internet anymore...cause they're all wrong I suppose. 

Lighten up bro. 
Life is short.


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## SemiMan (Oct 16, 2015)

bykfixer said:


> Guess I won't bother reading on the internet anymore...cause they're all wrong I suppose.
> 
> Lighten up bro.
> Life is short.



... When you are reading a poorly informed tech writers summary of a highly technical article ... then yes, they are often wrong. If you don't have the knowledge to read between the lines, then the interpretation of the interpretation may be even worse.

Life IS short. Hence I choose not to waste other's time with less than factual information.


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## bykfixer (Oct 16, 2015)

O ok...


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## MrJino (Oct 23, 2015)

I'm guessing there will be a day when LED is old technology...


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## Dr. Tweedbucket (Oct 24, 2015)

MrJino said:


> I'm guessing there will be a day when LED is old technology...



Right, just like incandescent is to LED.

Maybe a new technology will surface that we didn't ever consider before ....OR a LED with a feedback loop that uses it's own output power to drive the input harder and add to the output and/or partially recharge the power source!!! Then the name Turbo would really mean something!!


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## SemiMan (Oct 24, 2015)

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## more_vampires (Oct 26, 2015)

HID: ~55% efficiency. (give or take)

LEP: ~90% efficiency.

https://en.wikipedia.org/wiki/Plasma_lamp


> High intensity discharge lamps have typical luminaire efficiencies of 55%, and fluorescent lamps of 70%. Plasma lamps typically have luminaire efficiencies exceeding 90%.



http://straylightoptical.com/light-emitting-plasma-vs-led/2011/05


> Light Emitting Plasma™ and Light Emitting Diode (LED) provide similar reliability and lifetime. Directionality of LED light is good. Properly balanced high-end LED fixtures are beginning to achieve satisfactory CRI and color temperatures, although this comes at a significant premium. Lumen density of LED’s is still low compared with Plasma. It still takes about *100 typical high lumen LEDs to produce similar lumen output to 1 Plasma source.* This high component count combined with high thermal sensitivity which requires large heat sinks yields fixtures which are typically larger, heavier, and more expensive than a Plasma fixture for the same lumen output. LED does have the advantage of instantaneous turn on. LED is a good fit for lower lumen applications such residential indoor and accent lighting, but not high lumen applications.
> 
> Click here to find out how the superior output and efficiency of LEP is implemented in applications like area lighting, roadway lighting, and industrial lighting.



Lumens, man. Lumens.


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## lightlover (Oct 26, 2015)

MrJino said:


> I'm guessing there will be a day when LED is old technology...



MrJino,
Look back on this topic in 10 years time! 
In 20 years time! 

I won't be here then, but - look to the future .. . .

EDIT: I can look back 25 years - sad!


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## idleprocess (Oct 26, 2015)

more_vampires said:


> HID: ~55% efficiency. (give or take)
> 
> LEP: ~90% efficiency.
> 
> https://en.wikipedia.org/wiki/Plasma_lamp


I believe the takeaway there is _*luminaire* efficiency_, not _light source *electrical* efficiency_.


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## SemiMan (Oct 26, 2015)

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## more_vampires (Oct 27, 2015)

idleprocess said:


> I believe the takeaway there is _*luminaire* efficiency_, not _light source *electrical* efficiency_.


Just mentioning tech other than LED, some had mentioned it... on topic. 



SemiMan said:


> Fixture efficiency has nothing to do with source efficiency. Fixture efficiency is how much of the source lumens make it out of the fixture.
> 
> Most of what you quoted on LEP is old, and somewhat inaccurate except you can do a lot of light from a single LEP source. Unfortunately most every promise of LED has not come true and LED has just steamrolled it.
> 
> Semiman


The topic of the thread is max lumens. Even HID can scale higher than LED from a single source.

Anyway, if it's old then go edit the wiki.  That's what wikis are for. 

Also: http://www.brightlightsystems.com/BLP1000.html
Show me the single 46,000 lumen LED emitter, I must have one.  Here's a 46,000 lumen LEP.


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## search_and_rescue (Sep 17, 2021)

Well, it's nearing the last quarter of 2021. Last night I was comparing the Nitecore TM38 Lite to the Acebeam K75. At first the CREE XHP 35 HI appeared very intense. Then I turned on the Luminous SBT-90.2 and the thing made the CREE appear weak. How did Luminus do it?

On another note, the far future of the Earth may not be all bad. In one billion years, the Solar Luminosity will increase at least 10%. For us Flashaholics, that's fantastic! That is the ultimate flashlight. Even if predictions are way off, only good news can result. I mean that perhaps in only one million years the Solar Luminosity will increase by 15%, and the predictions were wrong. That would be the ultimate flashlight! Our own Sun is nothing to shake a stick at!


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## thermal guy (Sep 17, 2021)

I might get some slack here but I think we are already brighter then we need to be. And honestly a light that puts out 15-20k for 15 seconds till it overheats is just for bragging rights. Give me 1-2 thousand that lasts for a few hours and that’s all I’d ever need. Much more reliable as well.


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## search_and_rescue (Sep 17, 2021)

thermal guy said:


> I might get some slack here but I think we are already brighter then we need to be. And honestly a light that puts out 15-20k for 15 seconds till it overheats is just for bragging rights. Give me 1-2 thousand that lasts for a few hours and that’s all I’d ever need. Much more reliable as well.


Thermal Guy I think you may be quite right. I had a Summer deal to acquire the newest LEP. The thing tested 1.8Mcd and 502 ANSI lumens. It lights up a palm tree 300 meters away brighter than the MF05. The LEP uses only a single 21700 cell and is a pleasure to hold in the hand. It barely gets warm too. So I think you are right and I know what you mean. If we had LEP tech projecting 2 X 502 ANSI lumens onto the same target 2 X 1.8Mcd; indeed that is plenty of brightness! I’m with you!


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## richbuff (Sep 17, 2021)

For me, this lumens thing will top out at three MS18 ganged, one gang in each hand, 600,000 lumens. 

I can run a large light on low mode for super duper runtime, or I can run a small light on max mode for maximum performance to size ratio, but with low runtime. Or I can run a medium size light on medium mode.
Size, power, runtime. I pick the two I like and then I have no complaints about the third one. Mostly I like low runtime, and the most power per given size. So far, I do not own a large size light with a single XP-G2 emitter. But, if I were a runtime connoisseur, I certainly would. More than one. A lot of large lights with lots of battery capacity, with a single teensy weensy itty bitty tiny emitter on top. But no, not me, so far. Only lights that have low mode, medium mode, normal mode and mega peta exa Turbo mode that is capable of a brief blaze of illumination glory, then time to refuel. I use low mode as a practical tool. I use turbo to make life exciting. And/or to briefly brightly illuminate a large area, then quickly throttle back when the small target is identified.


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## 3_gun (Sep 17, 2021)

As a technical exercise I doubt we will ever see an end of the hunt for more lumens. That's not a bad thing unless it causes other development to not be done. We are very close to or at that point. 

Two thousand lumens will clearly light distances well beyond what we can see in any detail. Yes there are cases where that kind of light is very much needed but those situations are specialize & uncommon for most in daily life. But lumens sell & marketing drives sales & sales influences development and repeat.

Just about every light I've bought in the last six weeks has an upper lumen level that is meaningfully unsustainable. The light that ended my search for a new EDC did so more with the UI & beam pattern than peak lumen levels. Turbo (4600L claimed) isn't even in the normal rotation of light levels, it can only be reached with a shortcut. And the run times of the two lower light levels (not including ML) were also bigger selling points for me than the peak lumens. But of course everyone & I do mean everyone wants to see turbo. 

I use my light for CC, work & safety. It's a tool not a hobby or toy. Truth is I have more than one EDC. I take the one that's suited for the day I expect to have plus a margin to handle things I don't expect. They are; Olight i5T, Fenix LD12, Klarus SP10 and Acebeam E70. My "bedroom slippers" EDC is a Sofirn S11c. It has found itself clipped on my T-shirt, sweat shirt, sweat pants, etc pretty much with me anytime I'm wearing slippers. Only the E70 exceeds 1k/L in any meaningful way, all have useful run times into double digits (hrs).

The chase of LUMENS has long since pass by me & my needs


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## search_and_rescue (Sep 18, 2021)

Yes, Sir. I would recommend the Streamlight 4AA Lux flashlight to anyone needing an actual tool. Several years back my wife’s car door had issues. At night in a large CVS pkg lot. I showed up with my Surefire M6LT and it was way too bright to look at what was wrong with her car door.

However, the Wonderful policeman drove up to us (I guess the only good thing about my 900 lumens was it signaled to a passing policeman). You know what flashlight he used AND figured out and fixed my wife’s problem car door? He was using a 99 cent 9 LED clicky light! It was exactly the amount of light needed!


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## DaveTheDude (Sep 18, 2021)

3_gun said:


> As a technical exercise I doubt we will ever see an end of the hunt for more lumens....
> Two thousand lumens will clearly light distances well beyond what we can see in any detail. Yes there are cases where that kind of light is very much needed but those situations are specialize & uncommon for most in daily life.


I'd like to expand on a point 3-guns made in passing (quoted above).

Engineers can develop lights that will blind you if misused. I'm of the opinion that it is the human visual system that will ultimately set practical limits on lumen output in commercially available lights, mostly because folks won't spend money on lights that don't meet their needs. (This last bit will not apply to CPF members. 😁)

A light that can deliver 1000 lumens as measured at a target a mile distant does not mean that your visual acuity is sharp enough to see the thing being illuminated. You may be able to detect the object's _presence_ at that distance, but your vision isn't naturally sharp enough to make out the details. (If your purpose however is to deliver HE rounds downrange, please disregard this comment.)

I suspect that the commercial market will arrive at a general consensus as to a practical limits on lumens. At that point I predict the focus will be on making these high-power lights into small pocket rockets, and on improving battery performance.

As for CPF members, there will always be enthusiasts who will appreciate exotic materials, and the highest possible grade of emitter and electronics, to support customer products and producers. 

My 2¢.


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## Olumin (Sep 18, 2021)

It depends on application oc. Everyday portable indoor/urban illumination = 5 - 500 lm 99% of time. Outdoor illumination = <1000 lm. Search & rescue / military / Defensive >1000 lm. Of cause there are exceptions but thats the rule. I would not want a search- or defensive light will less then 1000 lumens. Brighter will always be required for specialized applications, but for general portable lighting, we have reached peak practical brightness years ago. Modern lights can maintain over 1000 lumen quite effectively, even on a single cell. When choosing the correct beam profile for the task required, this level of light will almost always suffice (*i.e*. not using flood light to spot things in the distance, not using thrower for lighting up a warehouse). 

Practical maximum lumäns for sustained brightness on 2x cr123 or single 18650 = 500lm. Above that high drain 21700 up to 1000lm. Anything brighter = multi cell, huge, heat sinking, active cooling for only little increase in runtime on high lumen modes. HID will not need cooling but is less energy efficient and power throwers are still big, good for professional usage & military. LEP = maximum throw but no usable spill = very limited use case.


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