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

[magellan]

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".

The sun or an LED will "emit" a set amount of power per unit area in a somewhat defined distribution pattern. For the sun, that is a about 67 megawatts per per square meter in a roughly spherical distribution. For an LED, that is up to say 2-3 megawatts per square meter in a roughly lambertian distribution.

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.

2) IF you could create a Perfect optical system, and IF you could create a Perfect Single Sided black body, then the maximum temperature of that black body would be limited to the surface temperature of the sun, or 5500K approximately. A perfect black body will absorb everything and turn it into heat. AND everything that is hot radiates! Once that black body reached the same temperature as the sun, or 5500K, it will radiate as much power as it is being bombarded with and stop increasing in temperature!

Semiman ..... moonlighting as junior physics man.

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.

 

[leon2245]

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

Courtesy: semi man.

 

[xzel87]

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.

 

[magellan]

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.

 

[Rick NJ]

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.

 

[SemiMan]

-----

 

[SemiMan]

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.

 

[beaconterraone]

We've got quite a ways to go:

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

 

[magellan]

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.

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.

 

[magellan]

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.

 

[mattheww50]

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?

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.

 

[magellan]

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?

 

[WalkIntoTheLight]

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.

 

[WalkIntoTheLight]

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.

 

[mattheww50]

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.

 

[SemiMan]

-----

 

[magellan]

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.

 

[Rick NJ]

...
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

 

[WalkIntoTheLight]

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.

 

[FRITZHID]

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.