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Power Hardware Science

Solar Breakthrough Could Provide Power Without Solar Cells 223

Posted by Soulskill
from the bright-ideas dept.
An anonymous reader tips a University of Michigan news release about the creation of what's being called an "optical battery" that could lead to the use of solar power without traditional solar cells (abstract). Quoting: "Light has electric and magnetic components. Until now, scientists thought the effects of the magnetic field were so weak that they could be ignored. What Rand and his colleagues found is that at the right intensity, when light is traveling through a material that does not conduct electricity, the light field can generate magnetic effects that are 100 million times stronger than previously expected. Under these circumstances, the magnetic effects develop strength equivalent to a strong electric effect. 'This could lead to a new kind of solar cell without semiconductors and without absorption to produce charge separation,' Rand said. 'In solar cells, the light goes into a material, gets absorbed and creates heat. Here, we expect to have a very low heat load. Instead of the light being absorbed, energy is stored in the magnetic moment. Intense magnetization can be induced by intense light and then it is ultimately capable of providing a capacitive power source.'"
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Solar Breakthrough Could Provide Power Without Solar Cells

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  • So how long until this becomes practical on a personal scale? I really want to see someone's ipod solar edition get stuck to a metal guardrail until the sun goes down.
    • So how long until this becomes practical on a personal scale?

      You must be new here.

    • by Asic Eng (193332)

      So how long until this becomes practical on a personal scale?

      Nobody knows, potentially never. It's just basic research, and it could be very interesting just for it's own sake. However they need to package it somehow, to give people an idea how basic research fits into overall scientific and technological progress. It does fit there, and of course we constantly get advances which were rest on basic research done 30 years ago.

      However if you want to use something now - you can just ignore this news. On t

  • by Itesh (1901146) on Friday April 15, 2011 @02:27PM (#35831378)
    I gotta wear shades!
  • by Geoffrey.landis (926948) on Friday April 15, 2011 @02:28PM (#35831392) Homepage

    The press office at U. Michigan has gone a long way from what they actually did to what they are speculating might be theoretically be possible. What they actually did was to predict a theoretical effect which has not yet been demonstrated. The press office then suggests that if you concentrate sunlight by a factor of a hundred million-- about seven hundred times higher than the theoretical concentration limit-- that this as-yet-unidentified material might be able to convert the light into electricity.
    This is a bit speculative. They've predicted an interesting theoretical effect. Let's keep it at that, which is a nice piece of work, and leave the speculation to science fiction writers (like me).

    • Re: (Score:2, Interesting)

      by Anonymous Coward

      You're right that the concentration factor is about 100 million times (from ~1000W/m^2 sunlight at the Earth's surface), which is crazy high, but I wasn't aware there was a theoretical concentration limit. Where did you get that from and what's the rationale for it?

      • by Geoffrey.landis (926948) on Friday April 15, 2011 @03:46PM (#35832256) Homepage

        I wasn't aware there was a theoretical concentration limit. Where did you get that from and what's the rationale for it?

        The theoretical concentration limit is straightforward-- it comes from the fact that the sun has a non-zero solid angle. Basically, a concentrator works by increasing the fraction of the sky that's filled by the sun, and the best you can do is to make the light come from the whole sky. (Well, there's also a factor of n, the refractive index).

        The book Solar Electricity by T. Markvart gives a calculation (page 237-- it's available on googlebooks)

        • by sznupi (719324)
          How one avoids instant vaporisation of any real world "cell" or ionization of most non-perfect vacuums, with such fluxes, would be in itself an... interesting dilemma.
      • by Mt._Honkey (514673) on Friday April 15, 2011 @04:09PM (#35832578)

        There's a theorem in imaging that says you cannot focus a light source to create a beam any more intense then at the surface of what is emitting the light. A consequence of this is that you cannot heat something to hotter than the surface temperature of the sun by concentrating sunlight in any way, even if you had a lens the size of the solar system. The spot size that you get will just keep getting bigger.

        Incidentally if you were able to do this it would violate the 2nd law of thermodynamics, because you would be moving energy from a cooler object to a warmer one without doing any work, thus decreasing the total entropy of the universe.

        • There's a theorem in imaging that says you cannot focus a light source to create a beam any more intense then at the surface of what is emitting the light. A consequence of this is that you cannot heat something to hotter than the surface temperature of the sun by concentrating sunlight in any way, even if you had a lens the size of the solar system. The spot size that you get will just keep getting bigger.

          That's true, but it only applies to imaging optics. Non-imaging optics, hyperbolic concentrators being one of the commoner cases, are not subject to this limitation. If I'm remembering right -- it's been about 25 years -- there was pioneering work done at the University of Chicago in the late 80's using hyperbolic concentrators to achieve concentrations considerably above those of the surface of the sun. This doesn't violate the Second Law because you only get the amount of light that falls into the collect

        • by Kim0 (106623)

          Making sun light hotter than the Sun is possible by using a concentrator with a high index of refraction, such as sapphire.
          This is allowed by the 2nd law of thermodynamics because light is reflected, spread, and lost outside the concentrated zone, thus increasing the total entropy.

          Kim0+

    • by Thud457 (234763)
      First that vague press report on the purportedly revolutionary (no pun intended) wave disk engine [slashdot.org] from Michigan state, now this. Did some sort of pronouncement go out that Michigan universities need to flog green technology to overcome the abject failure of Detroit ?
  • Wait, what? (Score:5, Funny)

    by pushing-robot (1037830) on Friday April 15, 2011 @02:30PM (#35831408)

    Electromagnetism consists of equal parts electricity and magnetism?

    You mean... That fool Maxwell was right?

    • by mevets (322601)

      What happens to EM radiation if you remove the M? My physics is zero; I kinda get photon-electron pinball game, but if you bleed the magnetic power away, what happens to rest of it?

      [ps. sorry if my tourettes addled puppy chimes in, he seems to have lost his way home and soiled himself]

      • You can't have E without M. Magnetism just comes from relativistic effects on electricity. Take a look at http://en.wikipedia.org/wiki/Relativistic_electromagnetism [wikipedia.org] for an example.

        • by JSBiff (87824)

          Isn't a static electric charge an example of E without M?

          I know you can't have a magentic field without an electric field, but is that really a two-way relationship?

          • Re:Wait, what? (Score:4, Informative)

            by pclminion (145572) on Friday April 15, 2011 @04:19PM (#35832708)

            Isn't a static electric charge an example of E without M?

            What is a static charge? I can choose a reference frame where the charge is in motion, and thus produces a magnetic field. If you look carefully at the fundamental equations of electromagnetism, you see things like "the force on the charge is proportional to the velocity of the charge," and "the induced magnetic field is proportional to the rate of change of magnetic flux."

            Both of these statements immediately imply the question in whose reference frame are we to measure the velocity of the charge or the rate of change of magnetic flux? In one frame to another the velocity is different, as is the rate of change of flux. But no matter what reference frame you pick, the particle does the same thing. This means that the electrical force and magnetic force are actually the same force, but they appear to be different when you choose some particular reference frame in which to measure them. You could have chosen a frame in which both fields took on different values, yet the net effect on the particle is the same.

            It is relativity which causes the apparent splitting of the one unified force (electromagnetism) into two different forces (electricity and magnetism). You cannot have one without the other, or rather, you can have as much or as little of one as you want, depending what frame you measure in.

            They are the same and can't be separated.

            • by pclminion (145572)

              "the induced magnetic field is proportional to the rate of change of magnetic flux."

              Quoting myself there... Obviously, what I meant to say is the induced electric field, not the induced magnetic field.

          • by CCarrot (1562079)

            I know you can't have a magentic field without an electric field, but is that really a two-way relationship?

            Actually, you can't. A magnetic field induces an electric field across conductive elements proportional to its strength and the conductors' position relative to the magnetic field (and the right hand rule, of course). It's the basis for many measurement tools.

            The reason you don't constantly get zapped by the earth's magnetic field is that a) it's pretty weak, and b) you're not that great a conductor (sorry if I dashed some dreams there)

            If you were silly enough to hug a strong enough electromagnet, you cou

            • by CCarrot (1562079)

              Bah, should uncross my eyes before replying. Didn't see the "can't", thought you said "can". Sorry, my bad!

        • by mevets (322601)

          The article implies that the 100Million times stronger magnetic field is where the power is tapped from; thus it would have to weaken the field. What happens to the light?

          • by pclminion (145572)

            The article implies that the 100Million times stronger magnetic field is where the power is tapped from; thus it would have to weaken the field. What happens to the light?

            It ceases to exist. There is no law of "conservation of light." It's okay for light to disappear.

  • by 0123456 (636235) on Friday April 15, 2011 @02:30PM (#35831416)

    If you have 10 million watts per square centimetre of light focussed on something there are far more efficient ways to convert it into useful power.

    • by gr8_phk (621180)

      If you have 10 million watts per square centimetre of light focussed on something there are far more efficient ways to convert it into useful power.

      Yeah, the something will suddenly be a high temperature gas suitable for boiling water or even blowing itself through a turbine.

    • by slinches (1540051)

      Yes, like igniting a fuel pellet in a fusion reactor.

  • So do we now have to ask "Solar cells - How the f*ck do they work??"

  • by mark-t (151149) <markt@@@lynx...bc...ca> on Friday April 15, 2011 @02:34PM (#35831480) Journal
    This is still all theoretical, and to the best of my understanding has not been verified by actual working prototypes.

    I'm really surprised that the article didn't mention "5 years" as a time scale for when this will be viable, since that's the typical duration mentioned in these sort of articles --- far enough in the future that most will have forgotten about it by the time we get there, but near enough to still feel like it's worth anticipating (in other words, the perfect length of time for a project that needs funding to continue, but may never actually produce desired results).

  • Sure it's all great now, but what happens when we run out of sunlight?

  • OMG, OMG. So who found this thing? John Galt?
  • This looks like some really promising work. I still want to crush your football team on the gridiron, though. 3 Cheers for U of M Physics! 3 Cheers for Rich Rodriguez!

  • This is what patents are for. Not that getting money from you clicking on my button.
  • At 10% effeciency I'm not understanding the appeal.

    The light has to be concentrated which means tracking electronics, hardware, mirrors, maintenance..etc.

    You can get about 30% effeciency today by pointing concentrated solar energy at a stirling engine.

    The effect itself is more intersting to me than the possible use in solar energy.

    • by scorp1us (235526)

      It is the simplicity. Both manufacturing and maintenance. Current solar panels top out at 19% efficiency, but take a whole host of environmentally bad chemicals and processes to make. Then they degrade over time. This suggests common glass could power the world.

      You approach 30% on a sterling engine, with a perfect source and sync. But you have moving components that will wear out and need maintenance.

      Basically, imagine a piece of glass with integrated lens with wires on it - solid state, reliable, durable,

  • or it didn't happen. A working prototype is fine too.
  • ...how long before we never hear about this one again?

  • All hail our decepticon overlords!
  • ..It can be implemented main-stream, for less cost and be more efficient that current processes.  Until then this is all just intellectual masturbation.
  • You can do the same thing by smearing a thin layer of ripe banana on graphite-coated paper. Nearly .5 watts per square meter.
    All you need is paper, a fat pencil and a bunch of ripe bananas.

  • And create a moving magnetic field over coils wound around the medium. Instant power.

  • Let's build more nukes!

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