13 posts • joined Wednesday 12th October 2011 02:29 GMT
These features are much smaller than the wavelength of light. Therefore they do not reflect it so much as scatter it. When they do their job correctly, they scatter the light forward into the solar cell beneath them. The Earth's atmosphere scatters light, some wavelengths more than others; that's why the sky looks blue. Nanoparticles from something like smoke can scatter more red light and make spectacular sunsets
A normal silicon solar cell will look shiny. If you look at something like this it will not be shiny. For years high performance infrared sensors/detectors have been coated with nanomaterials such as "gold black" that reflect so little they look black to the naked eye. In that case the coating can absorb the IR and it is detected as heat. In the case of solar cells, they do not want the layer to absorb, simply to reduce reflections.
Gold and silver were probably used initially because they are relatively inert to many chemical processes, making process development less restrictive and more flexible. Once proof of concept has been demonstrated, one can try to use a cheaper material.
It was all explained here
I wish I could find it, but probably 5 or 6 years ago The Register had a story where a graph of temperature data was shown and the authors broke it up into a slow gradual increase on top of which was a sin wave.
The gradual increase was attributed to the CO2 increase, though it was not fast enough to result in "we must act now" horror stories.
The cyclical wave was due to some major ocean current cycle. It properly showed the decrease in temperature back when Newsweek ran the historic "Global Cooling" cover story. It showed the increase in the '90's which was (ignorantly) extrapolated into the "hockey stick" predictions of the global warming cult. It showed the level period we are now experiencing, where the downward part of the cycle is balancing the long term upward trend. It also predicted temperatures would start to rise again around 2020 when the sin wave turns back up.
If anyone can locate that story, it should be reprinted.
Not a problem
I doubt anyone in the area will be on visual flight rules. Airline flights will be on instruments, even in clear skies. Official approach patterns guarantee that, even in fog, you aren't going to hit anything if you stay on the path, so it doesn't matter if the building is invisible or not.
If the Doctor is going to be Female
They might as well go all the way and use Francine Dee.
What is going on is...
You need to conserve both energy and momentum. When an electron and hole combine, the energy is usually emitted as a photon (light) in an LED.
However, a photon has very little momentum compared to what the electron and hole had. That's why only SOME semiconductors are good at emitting light--the ones with what is called a "direct bandgap" where it's possible for the electrons and holes to combine with a small net momentum.
An "indirect bandgap" material, such as silicon, has the low point of the conduction band (where the electron is) offset in momentum space from the high point of the valence band (where the hole is). If their recombination energy is given up as a photon, momentum can't be conserved. So the energy is usually given off as a PHONON, which is a vibration of the crystal lattice (i.e. heat) which can conserve both energy and momentum.
If, instead of exciting the lattice of atoms or emitting light, the energy is used to excite a free electron to carry away the energy and momentum, that's an Auger recombination. In general "Auger" refers to events involving multiple electrons. At high power, LEDs have plenty of excess electrons in the depletion region (the junction of the diode where recombination takes place) so it's more likely one of them will be nearby to accept the energy given up.
Re: Prosecution would be proof of idiocy..
On the other hand, how much effort would the police spend tracking someone down if you told them you think maybe, when you left the door open, someone might have looked in at your wallpaper, but you can't really prove it.
Ocean Acidification is not as Arguable as "Global Warming"
There is a leap of faith in the Global Warming Disaster chain: You can start with a measurable fact (more CO2 is being put into the atmosphere) and a related fact (CO2 is a "greenhouse gas" i.e. it absorbs infrared radiation). The leap comes from the models and what they predict will happen to the climate if CO2 continues to increase. As the years go by, more and more flaws are found in the models and the runaway global warming is not happening. Maybe it will get warmer, eventually, but it takes a leap of faith to get from there to the runaway disaster scenario right now. And I'm not so sure a little warming wouldn't have some upside as well as some downside. It might even prevent the next ice age.
Ocean Acidification does not require that same leap. It is easy to show, in a lab, that CO2 in the atmosphere is absorbed by seawater. You can also show that CO2 in the seawater changes the pH, and that the change in the pH affects sea life that makes shells for itself. End of story. No predictions of runaway or catastrophic droughts or hurricanes or melting glaciers. Simply that increasing CO2 in the ocean will have a downside for a section of the ecosystem.
You can also measure the pH around the oceans (I know this because I worked on the sensors they use to do so) and see the effect on various organisms. So far this takes no models at all. Details of what may happen in the future oceans may not be precise, but there is no large leap of faith involved to see the chain of events.
While I don't take Global Warming seriously (certainly not the wild claims of the eco-lobby) I will say that Ocean Acidification is real and measurable without fudging data or arguing over tree rings.
I was wandering around Shenzhen one day at the end of a trip all over China and met a woman who, along with her husband (both ex-pats), owned a factory there. She told me that name brand products manufactured for export were not allowed to be sold in China. What her company had to do was ship them to Hong Kong, then import them back. Then they could be sold locally.
Perhaps some of the equipment having labels applied in the smaller places were simply "extra" ones that were sold, unbranded, to avoid having to do the export/import dance.
Check the Daily Beast
The liberal Daily Beast reports on a broadband project backed by a frequent Obama White House visitor and donor that has Pentagon officials concerned over potential military GPS interference. The Obama FCC took the lead in intervening on the donor, billionaire hedge fund manager Philip Falcone’s, behalf and granting his company called “LightSquared” one of those coveted Obama waivers from existing law. Then Obama officials reportedly pressured a general to alter his testimony about the company’s impact on military satellite transmissions.
In a nutshell:
The four-star Air Force general who oversees U.S. Space Command walked into a highly secured room on Capitol Hill a week ago to give a classified briefing to lawmakers and staff, and dropped a surprise. Pressed by members, Gen. William Shelton said the White House tried to pressure him to change his testimony to make it more favorable to a company tied to a large Democratic donor.
The episode—confirmed by The Daily Beast in interviews with administration officials and the chairman of a congressional oversight committee—is the latest in a string of incidents that have given Republicans sudden fodder for questions about whether the Obama administration is politically interfering in routine government matters that affect donors or fundraisers. Already, the FBI and a House committee are investigating a federal loan guarantee to a now failed solar firm called Solyndra that is tied to a large Obama fundraiser.
Now the Pentagon has been raising concerns about a new wireless project by a satellite broadband company in Virginia called LightSquared, whose majority owner is an investment fund run by Democratic donor Philip Falcone. Gen. Shelton was originally scheduled to testify Aug. 3 to a House committee that the project would interfere with the military’s sensitive Global Positioning Satellite capabilities, which control automated driving directions and missile targeting, among other things.
According to officials familiar with the situation, Shelton’s prepared testimony was leaked in advance to the company. And the White House asked the general to alter the testimony to add two points: that the general supported the White House policy to add more broadband for commercial use; and that the Pentagon would try to resolve the questions around LightSquared with testing in just 90 days. Shelton chafed at the intervention, which seemed to soften the Pentagon’s position and might be viewed as helping the company as it tries to get the project launched, the officials said.
An Obama Donor
The major backer of Lightsquared was a big Obama donor. Letting him buy bandwidth for billions below cost (because it was sold as space only) and then getting the FCC to make it ground based was payback. They even pressured a General to testify it wouldn't interfere with GPS. The General refused and blew the lid off the scam.
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