Slashdot Mirror
Research Promises Full-Spectrum Solar Cell
nphillips writes "As is being here reported here, a serendipitous discovery was made that a single system of alloys incorporating indium, gallium, and nitrogen can convert virtually the full spectrum of sunlight -- from the near infrared to the far ultraviolet -- to electrical current. For if solar cells can be made with this alloy, they promise to be rugged, relatively inexpensive -- and the most efficient ever created. Solar cells so efficient and so relatively cheap could revolutionize the use of solar power not just in space but on Earth."
vaporware!
and I quote
"In MBE the components are deposited as pure gases in high vacuum at moderate temperatures under clean conditions."
Further
"If it works, the cost should be on the same order of magnitude as traffic lights," Walukiewicz says. "Maybe less." Solar cells so efficient and so relatively cheap could revolutionize the use of solar power not just in space but on Earth."
-- The morphemes of your disquisition are ascertainable, but they have eschewed an ambit of transpicuous exposition.
As I understand it, UV light hits the earth at all hours.
Does anyone know how much UV hits the earth during the night?
Almost none. Virtually all of the light that strikes Earth comes from the sun.
As another poster pointed out, you may be confusing this with the mid-IR glow that warm objects (including the ground and the air) give off. The amounts of energy involved are very low, and room-temperature thermal IR is difficult to convert to electricity efficiently.
Any solar power scheme (and so any photovoltaic scheme) has to have enough storage capacity to power the load overnight. Ideally, it should be able to provide power for several days, in case of cloud cover/rain/whatever. This is why most home-powering schemes involve large battery arrays. A city-powering solar plant would probably use fuel cells (energy density is much higher, and there are off-the-shelf models of power-plant scale already available and in use).
For utility/residential applications, efficiency isn't very important since there's LOTS of roof area... you can use relatively inefficient technology. What really matters is $/Watt. How much do I have to spend to generate energy equivalent my house's usage?
~gb
The article noted that current-best solar cells are about 25% efficient, vs. 30% max. theoretical. How many percent more efficient are you figuring on the new solar cells being if space-made (vs. Earth-made)?
Check out the $billions$ that the dinky space station costs just to keep up. Ditto launch costs for your raw materials & totally unproven zero-grav solar cell factory equipment.
Now spread the extra costs of space-made solar cells out over the number of cells that you think will actually pass QC & reentry. Where do you see the high-volume market willing to pay the $HUGE$ price premium for a few percent better efficiency?
As gbell notes further down, efficiency doesn't mean too much, especially competing against fossil fuels. Cost per watt (call it financial efficiency) is what really matters.
It's easy to make up & spread cool- and credible-sounding stuff. Finding & checking hard facts is hard work.
I don't know if that's the same story or not, but I was remembering one where two scientists invent a full-spectrum solar cell, and the only way they can get it into the world without getting themselves murdered first, is to publish the specs openly and then collect royalties.
:)
Heinlein - he da man!
As an aside, a much more feasible way of vastly reducing our dependency on fossil fuels would be to switch everything feasible over to biodiesel. A lot less pollution, too, as well as better fuel efficiency than gasoline engines, plus the engines are simpler and last longer than gasoline engines (no spark system - diesel engines ignite during the compression process - no spark plugs, etc. needed).
Do a Google search for 'biodiesel' and enlighten yourself.
What the article doesn't happen to mention is that InAs (Indium Arsenide) was believed to have a bandgap around 1.6eV (not sure the exact number) and it's now known to be somewhere in the range of ~0.6eV. The article also don't mention phosphide compounds, which are far bigger in research and industry right now.
Fact is, nitrides are bastards to grow. You have to use gas-sources (instead of solid sources that most MBE-ers prefer). There's also no current way to make a nitride-based substrate, which means growing (typically) on sapphire or other lattice mis-matched substrates (GaAs, InP, etc). These lead to HUGE dislocation densities that greatly impact performace.
Now, that doesn't mean this can't be done. And in fact, magic is being done all the time in the world of research. But nitrides aren't going to be realized for some time. Not at least until other technologies pan out first (phosphides and the like). Those are cheaper to grow and allow for much lower defect densities.
Just so you folk's know I'm not just talking out of my ars--do some research and look up some papers. Authors to look for are Steve Ringel (OSU), Gene Fitzgerald (MIT), John Carlin (OSU), Sumitomo (Japan, somewhere), and by-far Yamaguchi (Toyota Technological Institute). Read up on these folks' work and those around them--they know space-based photovoltaics better than most, and very, very, very, very few are working with nitrides right now. Not that it's not going to eventually happen--but until defect densities get low enough, there's simply no way to make a good solar cell (read up on the previous authors' works if you want the theoretical calculations as to why).
Long, cute, or funny Sigs are just another form of over compensation, used by geeks, nerdz, etc.