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Earth Power Science Technology

Let There Be Light: Germans Switch on 'Largest Artificial Sun' (theguardian.com) 123

German scientists are switching on "the world's largest artificial sun" in the hope that intense light sources can be used to generate climate-friendly fuel. From a report: The Synlight experiment in Julich, about 19 miles west of Cologne, consists 149 souped-up film projector spotlights and produces light about 10,000 times the intensity of natural sunlight on Earth. When all the lamps are swivelled to concentrate light on a single spot, the instrument can generate temperatures of around 3,500C -- around two to three times the temperature of a blast furnace. "If you went in the room when it was switched on, you'd burn directly," said Prof Bernard Hoffschmidt, a research director at the German Aerospace Center, where the experiment is housed in a protective radiation chamber. The aim of the experiment is to come up with the optimal setup for concentrating natural sunlight to power a reaction to produce hydrogen fuel.
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Let There Be Light: Germans Switch on 'Largest Artificial Sun'

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  • by Anonymous Coward

    ... And you have the first solar powered sun!

  • by volodymyrbiryuk ( 4780959 ) on Thursday March 23, 2017 @11:24AM (#54095557)
    "Hey Helmut I bet you can't last longer in there without sunscreen than on that beach in Spain last year." Helmut: "Hold mein bier."
    • Y'all have it all wrong though. There is no equivalent to the American, semi-inebriated uttering "hold my beer" ("beer", when referring to the stuff made in the USA, should be in air quotes) in German, and for the following reasons:
      * German beer is still proper beer full of natural goodness, not so dissimilar to that effervescent multivitamin some people like to pop into a glass of water and drink daily for good health. Only better tasting and more effective.
      * Germans grow up on beer. They drink it at bre

      • Of course Germans have to consume copious amounts of beer. It's far too light. There's this little country to the northwest of Germany which has real beer. AND a sense of humour. But no Mezger unfortunately. No I don't mean your name, it's without a T.

      • When I was in Ireland, all the Germans were drinking Budweiser.
      • Also, if some humor-deficient mensch claims that Germans have no sense of humor [...]

        I know Germans have a sense of humour. I've seen 7 Zwerge.

  • This experiment is the stuff of middle school dreams, But the hydrogen fuel stuff is on the surface of the moon; which is cheaper? Build this really fun contraption, or send a drone to the moon to get a bucket of the fuel stuff from the surface, bring it back home, then refine it on earth?
    • Re: (Score:2, Informative)

      by Anonymous Coward

      Another inane comment from the peanut gallery. While there is Hydrogen on the surface of the moon are you mistaking this with Helium-3? Otherwise your question makes no sense as if you want to refine hydrogen today the cheapest way to do it has nothing to do with space.

  • by tinkerton ( 199273 ) on Thursday March 23, 2017 @11:36AM (#54095661)

    That's a lot really. What kind of lights are these?

    The summary obfuscates this but whatever the amount of incandescent bulbs you are focusing on the same spot, you cannot get a temperature that is higher than the filament in the bulb (the black box temperature of the bulb). And 3500 is a lot for an incandescent bulb.
    Maybe it's another kind of lighting then. Like a combination of different LEDs.

    • Another example: it's not possible to use mirrors to concentrate sunlight so that it can heat something up to more than 5500 degrees.

      • Wouldn't that only be true if you were trying to focus the heat from a single lamp filament? When there are more than one you can aim the light at the target from all angles and you aren't focusing light down to a point, you are adding more and more light to all the points being lit up.
        • How are multiple lamp filaments any different than one large filament?
          • by Gr8Apes ( 679165 )
            It's radiation being reflected and focused - multiple filaments can produce more of it for a given price than one larger filament. It's also easier to create the reflectors for smaller filaments, plus the source becomes more linear or point in form.
    • Likely arc lamps
      • Ah, I just looked it up and Xenon arc lamps can reach a color temperature of 6200K . So that's indeed a candidate.

    • That's a lot really. What kind of lights are these?

      The summary obfuscates this but whatever the amount of incandescent bulbs you are focusing on the same spot, you cannot get a temperature that is higher than the filament in the bulb (the black box temperature of the bulb). And 3500 is a lot for an incandescent bulb.
      Maybe it's another kind of lighting then. Like a combination of different LEDs.

      Okay. I will bite: Why not? You add energy from multiple lamps. Light superpositions and photons excites what they hit if they are absorbed, because they can't really do anything else. The maximum possible temperature at the focal point, shouldn't have anything to do with the original material.

      • by ThePyro ( 645161 )

        I had the same question. It seems to me that the only limiting factors would be total power (shouldn't it scale linearly with the number of bulbs?) vs. the rate at which heat is removed from the target location via thermal radiation or convection.

        I suppose you'd also have to consider what happens when your target vaporizes, since you'd no longer have a solid object at the focal point to absorb the radiation.

        • I had the same question. It seems to me that the only limiting factors would be total power (shouldn't it scale linearly with the number of bulbs?) vs. the rate at which heat is removed from the target location via thermal radiation or convection.

          I suppose you'd also have to consider what happens when your target vaporizes, since you'd no longer have a solid object at the focal point to absorb the radiation.

          That is also the only way a relation to the filament material would make sense. If the target is made of the exact same material, it would vaporize at the maximum temperature of the filament. But why would it be the same material?

      • by lorinc ( 2470890 )

        Because when you mix 2 things at temperature T, it doesn't make a thing at temperature 2T. Don't mistake temperature for energy.

        • Because when you mix 2 things at temperature T, it doesn't make a thing at temperature 2T. Don't mistake temperature for energy.

          ?? What are you smoking?

          Of course it isn't. But if you add two accelerations to eachother you get twice the acceleration. The stable temperature is based on where the acceleration and deacceleration of temperature meet (how much is added and how much is lost). When you add more, that balance changes upwards.

        • Because when you mix 2 things at temperature T, it doesn't make a thing at temperature 2T. Don't mistake temperature for energy.

          Wait, wait, wait.. Are you guys thinking about is a physical connected heat transfer? Then yes, adding two sources at 1000C will not get the temperature above 1000C (you need an active heat source and insolution for that). But this isn't a physical heat transfer. It is an energy transfer over light, and this case the new matterial unconnected to the old can have different material and different insulation. Using physical connected heat logic makes no sense here.

        • Because when you mix 2 things at temperature T, it doesn't make a thing at temperature 2T. Don't mistake temperature for energy.

          It depends on what kind of "mixing" you allow. You could have an array of 1000K lamps shining on solar panels, then combine the solar panel outputs to drive a small 2000K lamp. Certainly there would be a lot of energy loss in this system, but the temperature would increase to 2T.

          So without specifying the constraints on the collection system, you can't say that a 2T increase

      • Re: (Score:2, Informative)

        by Anonymous Coward

        xkcd explains it well: https://what-if.xkcd.com/145/

        • Good one. I didn't know where to start , apart from oneliners that would show that I at least knew the reason but that would be no help for anyone who didn't.

          • But that is the light from one sun. The way I understood that "what-if" was the process has to work in reverse. The focused light at the point has to be traceable back to where the light came from. But when you shine two light bulbs at a sheet of paper, you are not using lens to focus one bulb, you have two of them on top of each other. If you stand in front of two infrared heaters you will get warmer than if in front of one of them. But they aren't trying to make their heat hotter than their source by magn
        • Re: (Score:2, Informative)

          by Anonymous Coward

          To sum it up, quoting from that link: Lenses and mirrors work for free; they don't take any energy to operate. If you could use lenses and mirrors to make heat flow from the Sun to a spot on the ground that's hotter than the Sun, you'd be making heat flow from a colder place to a hotter place without expending energy. The second law of thermodynamics says you can't do that. If you could, you could make a perpetual motion machine.

          • I would add then that the second law forbids this because...
            In your closed system you could have a little pipe going back from the hot place to the colder place and attach an engine to it that converts the heat to electricity that leaves your closed system through a pair of wires Because we know how to do that very well, creating electricity when heat is transferred from a hot to a cold place. That is what all steam turbines and fuel based engines do. That would mean you could make free electricity.

        • I'm still confused. The XKCD cartoon shows a single source - the Moon, Sun, etc. But what they are doing here has 149 sources of energy. So if you had a binary sun (hypothetically identical suns) with two lenses, each focusing on a single spot - wouldn't that be 2x the temp? Isn't that a better example of what they are doing? And if you get things hot enough, could you start fusion which would then release vast amounts energy?

          • The xkcd cartoon is a good source but it may require multiple readings. It also shows a figure that is almost completely surrounded by sun and explains that it cannot get any hotter than the sun that way. The person can can hold a large magnifying glass it will make no difference at all.

          • by ThePyro ( 645161 )

            Does the following alternative explanation hold water?

            As your target object gets warmer, it radiates more and more of that energy into its surroundings. The energy loss to radiation actually grows much faster than the temperature of the object. According to the Stefan-Boltzmann Law [gsu.edu], the net loss of energy is proportional to (T^4 - Tc^4), where T is your target's temperature and Tc is the temperature of its surroundings. So as the target approaches the temperature of the lights it begins to give up energy

        • This is just another in an example of XKCD falling down on explaining to me. I don't get the thermodynamics argument at all. My model is that I can take photons and put them where I want to by having a demon move around a mirror and shot them all at one spot (kind of like Maxwell's demon, but this one has a mirror). Yes, this creates a super hot spot, but it didn't use any energy that didn't already exist. It just put it all in one place.

          • To answer my own question, the reason is that the amount of energy that can be captured is based on the temperature differences. So, if you could increase the temperature difference you could make energy.

            As for the demon, just like Maxwell's, it would decrease entropy and, in doing so, increase the amount of energy available.

    • Re:3500 degrees (Score:5, Informative)

      by BenBoy ( 615230 ) on Thursday March 23, 2017 @01:08PM (#54096507)

      you cannot get a temperature that is higher than the filament in the bulb

      ... as explained here: Fire from Moonlight [xkcd.com]

    • by dmatos ( 232892 )

      A bit of digging found another article [torontosun.com] that lists the type of lamp used.

      They're xenon short-arc lamps.

  • by Anonymous Coward

    Krauts experimenting to build ultra high temperature ovens. Does that sounds like a good idea?

  • Am I the only one looking at the pics of this thing and being reminded of crazy ass phat sound systems from ridiculous music videos of the '90s?

  • I'll bet the Germans have bagged all the best (artificial) sunbeds as well.

  • "If you went in the room when it was switched on, you'd burn directly,"

    No kidding!
    • by Anonymous Coward

      Yes, best to stand a bit off to the side so that you only burn indirectly.

      • by fisted ( 2295862 )

        Ist just how ze krauts talk. "directly" (direkt) is used in the meaning of 'immediately' here.

  • I almost thought that pesky Germans managed to get a positive q fusion reactor

    • Re: (Score:3, Insightful)

      by Tablizer ( 95088 )

      I know this is not fusion, but on that note, If Europe gets fusion to a practical level, it would be a yuuuuge embarrassment to the US, comparable to losing the space race. Plus, Europe will probably charge us for related patents, or at least they should: they shouldered most of the cost while we collectively denied global warming and bowed down to the Oil Gods.

      • by balbeir ( 557475 )
        Defunding the Department of Energy pretty much guarantees that the USA will lose that race.
        • by Tablizer ( 95088 )

          Mr. Perry will hopefully forget to cut his own Dept., if the debates were any indication.

  • by PPH ( 736903 )

    optimal setup for concentrating natural sunlight

    But it's not. Sunlight is for all intents and purposes collimated due to the extreme distance of its source. While these lamps can be "swivelled (sp?) to concentrate light on a single spot", that will tell you little about the setup applicable for use with sunlight.

    • Re:Nope (Score:4, Informative)

      by Carewolf ( 581105 ) on Thursday March 23, 2017 @12:40PM (#54096215) Homepage

      optimal setup for concentrating natural sunlight

      But it's not. Sunlight is for all intents and purposes collimated due to the extreme distance of its source. While these lamps can be "swivelled (sp?) to concentrate light on a single spot", that will tell you little about the setup applicable for use with sunlight.

      Have you heard about mirrors? And mirrors on swivels?

      See also Solar power towers [wikipedia.org]

    • by Nemyst ( 1383049 )
      A parabolic reflective dish can focus collimated light into a single point. It's been around for millennia.
      • by PPH ( 736903 )

        A parabolic reflective dish

        A single parabolic dish can. But a bunch of them "swivelled to concentrate light on a single spot" in no way emulates solar radiation at the earth's surface.

        I'm assuming that, as TFS says "The aim of the experiment is to come up with the optimal setup for concentrating natural sunlight". Well, a bunch of small parabolic dishes aimed at a single point is nothing like the typical reflector setup of a solar power tower. They are usually a bunch of flat mirrors that approximate a single parabola only over a la

    • by Anonymous Coward

      Sunlight is for all intents and purposes collimated due to the extreme distance of its source.

      Except it is huge! It covers about 1/2 a degree in the sky so its light is poorly columned.

      While these lamps can be "swivelled (sp?) to concentrate light on a single spot", that will tell you little about the setup applicable for use with sunlight.

      Another arm chair scientist on Slashdot. When you build a sunlight concentrator the light comes in from many angles, just like with these lamps. They aren't trying to test a concontrator, they are trying to simulate one, so they can test what is done (making H2) with the light.

  • If they could just get solar panels with 101% efficiency!

    • by Tablizer ( 95088 )

      If they could just get solar panels with 101% efficiency!

      Excellent: hookem up to an EM-drive, and we be trekkin', baby!

  • Now what were the parasites in ST TOS that could only be killed with strong sunlight? Spock had the extra eyelids, then Bones figured out only UV was needed.
  • And they're using zip ties? And they don't melt? Maybe I'm misunderstanding the suggestion that I would instantly burn walking into this room but I'm fairly sure zip ties burn at a lower temperature than I do.
  • Can I use this to power my solar panels at night?

  • Haha! Stoopid German scientists trying to come up with carbon-neutral fuel, even though climate change is big chinese hoax! Much easier to frack more oil out of the ground!

    Them German scientists pretty stoopid, huh?

  • Wouldn't it be cheaper just to play with magnifying glasses and the real sun? After all, won't the real sun will be used to produce hydrogen? Ahh.. Maybe they had some extra electricity from all those solar cells they have, and had nothing better to do with it.
    • Can't we mine the hydrogen from the sun? It's such a waste to fuse that hydrogen, transport the resulting energy to the Earth - an extremely minute proportion of which reaches Earth as visible or infrared light, the rest is wasted by being radiated isotropically to space - then use the light to break up water and make hydrogen again.

  • It reminds me of solar furnaces (like this one https://en.wikipedia.org/wiki/... [wikipedia.org]). Quite funingly the temperature and light intensity are similar.
  • A local newspaper has posted some interesting photos here [aachener-zeitung.de]

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