
Magnetic Property of Light May Lead to More Effective Solar Panels - mmcconnell1618
http://michigantoday.umich.edu/2011/04/story.php?id=7980&tr=y&auid=8154157
======
jws
[CORRECTIONS ABOUND! It isn't as bad as my first napkin suggests.]

Well done scientists[1]! Cue the engineers…

 _And it must be focused to an intensity of 10 million watts per square
centimeter. Sunlight isn't this intense on its own…_

Sunlight is about 1000watt/m^2. They are using 100 billion watts/m^2. That is,
you would need to concentrate sunlight to 100 million times to reach this
level.[2]

Put another way, if your fiber is about 1mm in diameter, you will need a
perfect[3] mirror array 10 meters in diameter to drive it[4]. [CORRECTED from
400 meters, thanks to _loup-vaillant_ ]

Wild speculation follows:

• This has got to be used in pulsed mode. 100 kilowatts down a 1mm optical
fiber is going to vaporize it if done for more than a tiny fraction of a
second. Are there the optical equivalent of super conductors that are suitable
for this?

• I went with a 1mm fiber because it "only" required a 10m mirror to drive it,
but at what voltage are we going to get 100 kilowatts of power out of a non-
conductor with a 1mm^2 cross section? Sounds like 50 zillion is the answer.

• Lets guess 10% efficiency, and the rest comes out as light at the end of the
fiber (so our fiber doesn't turn to plasma). Where are you going to point
that? I suppose into a light tight chamber contained in the molten salt loop
of a steam power plant would be a good start.

• Maybe this all works better at the nano scale. Heat dissipation is easier
since essentially all of the optical media can be in contact with heat sink.
The mirrors get smaller to achieve the required light density. There is a
shape, sort of stretched parabolic looking, that is a non-imaging optical
funnel which _might_ get your light all gathered to the same point, albeit
going in a variety of direction. The total power would be lower, lowering the
voltage required, letting you use sane power converters.

[1] And yet again, you have degraded the value of my undergraduate education
by falsifying my hard learned facts.

[2] I may well have lost a zero or more each way. It's early. Don't use these
calculations to place orders for mirrors.

[3] From 10+ meters away it is going to have to focus to a 1mm target.
[CORRECTED from 200+, it doesn't sound _so_ bad now]

[4] On proofreading I see I have a [4] footnote, in the text but no
corresponding note. It was probably vaporized by a poorly aimed fiber.

~~~
pedalpete
Aren't you missing a time variable?

I didn't go to University, and wasn't much for science in high-school, but
(using your figures) sunlight is 1000watts/m^2/second (or millisecond or
minute), isn't it?

If so, aren't your concerns about the size of the mirror, etc. imposing a
limitation, kinda like saying we can build a jet that will fly from NYC to San
Fran in 30 seconds, but we can't keep the people in one piece during the trip.
Therefore, we slow it down to a more humanly acceptable speed. With the volume
of sunlight hitting the planet, would we not be able to take only a portion of
that sunlight and concentrate it over time to get the same effect??

Of course, like an airplane, you need a minimum speed to create lift, and this
magnetic effect may have such a limiting speed/force(?).

Of course, I have no idea what I'm talking about, but you seem quite
knowledgable.

~~~
hugh3
_I didn't go to University, and wasn't much for science in high-school, but
(using your figures) sunlight is 1000watts/m^2/second (or millisecond or
minute), isn't it?_

No, sunlight is 1000 watts / m^2, or 1000 joules per square metre per second.
The Watt is a unit of power (ie energy over time).

~~~
jws
As a footnote, there is a pitfall here in the English language. The word
"over" might mean divided by, or it might mean "integrated across", which are,
in the case of constant power completely opposite meanings.

power is energy ÷ time (assuming the power is constant, and thinking of
horizontal lines for fractions you might say "power is energy over time")

energy is power × time (assuming the power is constant, but if you are
thinking "integration" you might say "energy is power over time")

The language can hurt the understanding.

------
Ripst
I work for a living doing research on solar cells.

I downloaded the technical paper and had a quick look. It would have taken me
days of hard study to understand what this undoubtedly clever people have
done, even though I have a PhD in physics. From how excited they seem to be
about their own work, I would guess its probably a very nice piece of
theoretical physics. But a few things are clear, from their own words:

\- They have not actually fabricated a solar cell, their most optimistic
expectation based on this technology is 10% efficiency. With efficiencies
bellow 14% you cant compete with other energy sources (you can not reach grid
parity), even if your solar cells are so cheap that they are free. That is
because the solar cell itself is only a fraction of the costs of solar energy.
Think of land, maintenance, support structures, cabling, power electronics,
and so on. That means that this concept, as it is, is useless for solar energy
production, just like "organic" and other fashionable solar cell technologies.
\- The effects they are talking about happen when light has an intensity, in
their own words "as low as 10^7 W/cm2" that is a hundred million times more
intense than the light from the sun. You need a big, expensive laser to
observe the effects they are talking about. \- This is just one more case of
people trying to spin their work as a revolution in solar energy, just because
it is fashionable and it gives you publicity and funding for your research.
They are probably fooling themselves in the first place, but that is no
excuse. This type of thing is terribly detrimental for all of us, as it takes
funding and attention from the solar cell technologies that actually work.
This is a shame for the people involved, and for the University of Michigan.
\- If you want to make a bet on solar cells, bet for III-V concentrator solar
cells. These are the most efficient ones, by far, (above 40%), and can be used
under optical concentration (up to a thousand suns) making the cost of the
cell itself almost irrelevant.

~~~
dimitar
From my not-still-incomplete engineering education I came to understand that
"solar panels" are huge photodiodes.

Doesn't sound exiting at all. I get to the point of having a PhD like you, I
guess nothing will excite me on the mass media when it comes to technology.

------
loup-vaillant
> _The university is pursuing patent protection for the intellectual property_

They make a discovery that may significantly benefit all humanity, then they
ensure it won't spread as fast as possible. Besides, I wonder who fund the
research so the university can claim property on new knowledge. (I'm not
accusing the university specifically here, they may have little choice given
the current system. Nevertheless, this sucks.)

~~~
pedalpete
From my understanding, they can't patent the physics, and that is the real
discovery here.

They have potentially hit on a way to create energy from a previously unknown
or ignored phenomenon, but just like you can't patent gravity, you can't
patent this.

Now that people are paying attention to this phenomenon, lots more research
will go into the best way of capturing it. Sure all those will likely be
patented as well, but there is nothing (in theory) stopping you from
developing your own way of capturing this energy and making it freely
available to the world.

~~~
anamax
> They have potentially hit on a way to create energy from a previously
> unknown or ignored phenomenon, but just like you can't patent gravity, you
> can't patent this.

Not so fast. While you can't patent gravity, you can patent using gravity to
do things (subject to novelty and obviousness).

That's how Feynmann ended up with a patent on nuclear submarines. You can't
patent radioactivity or heating things with radioactivity, but you can patent
using heat from radioactivity to do specific things.

------
edoloughlin
And a million pseudo-science/crack-cure marketers fire up their word
processors...

------
shr30
This begs the question, if you can magnetically polarize light, can you bend a
beam of light with a strong enough magnetic field? and if so, there is
tremendous potential beyond just energy storage.

~~~
icegreentea
This discovery doesn't have to do with magnets 'polarizing' light. Rather it's
using light's magnetic component to setup a charge separation. You also can't
"steer" light by polarizing it. Polarization is just the 'angle' that EM makes
with its direction of travel. Polarizing light just means selecting which
angle you want your light to have.

~~~
jws
I recommend a look at "circular polarization" for anyone that thought they
understood polarization as the direction the light vibrates.

Take two pair of Real-3d glasses from the movie theater and try the different
orientations (including front-front, front-back permutations). The
vertical/horizontal model will not explain your observations. Hence, I know
about circular polarization and had a confusing pre-movie experience at Iron
Man 2.

~~~
ChuckMcM
I missed the first 3 or 4 minutes of Avatar because I was playing with the
glasses and a laser pen pointer :-)

On one level I agree with you that this seems, at least initially, as tidy bit
of theoretical physics. Most people 'get' that light is an electromagnetic
wave, and of course Maxwell tied the two together quite elegantly.

The clever bits will be these two:

1) Is there a material, either natural or 'meta' in which the structure can
convert a fraction of the light passing through it into a magnetic field. If
so, and the light is modulated, you can induce a current in a conductor. Could
be useful, could be a parlor trick.

2) Can you run it backwards? Which is to say if you generate a magnetic field
of the proper type and orientation in the presence of such a material, can you
convert the magnetic field into light? If so what frequency? What coherence?
Does this paper provide the foundation for a LAAMR (Light Amplification by
Amplified Magnetic Resonance) (no, its not a pun on 'lamer' :-)

I expect if you can create the latter you could probably get a Nobel prize (or
at least share it).

Am I the only one who enjoys finding out we're wrong about some long held
scientific beliefs (in this case the magnetic influence of light)

------
sachinag
Meta comment: it's kind of awesome to see more umich.edu links on HN lately.
Would there be interest in an Ann Arbor meetup, say early May, after Funded by
Night?

~~~
ahi
see: <http://www.a2techevents.com/>

A2 New Tech is relatively well attended by the hacker news crowd. Their
monthly meeting is tonight:
[http://www.a2newtech.org/events/16678437/?eventId=16678437&#...</a>

