No, gross majority of white LED's use blue (so called royal blue, 450nm) as a base. Both, emitter and conversion to yellow are more efficient that way.
I used to work as a SDH/DWDM admin.
In early 2000's, while my colleague screwed up a major firmware update on a STM1/4 ADM and I as senior (haha - I was in my 1st half of 20ies) admin had to drive up to site (since the affected node was unresponsive to management system). After many unsuccessful attempts to recover it, at about 3 am. I decided to hard reboot the node, which caused it to boot up from corrupt firmware bank (it had two of those); which in turn just erased all the configuration, including traffic connections (which is built very robust btw). Since the site was on a (relatively small) island and had only 2 ADM's at the time, I more or less cut off the entire communication with mainland. For morning, I had managed to get my colleagues to ferry me another, fully fitted ADM (our last resort backup scenario was to replace entire node) - but as it turned out, it was in a hurry fitted with cards with different firmware (entire network was in middle of upgrade process) which resulted in same kind of useless "brick" I had already at hand. Although it was very cool to fly ~200km/h to port and back in my sporty car, to pick up the spare (not many police on the island and I had a very good excuse). By the afternoon, my higher-up manager had mobilized a helicopter to personally deliver me fully functional ADM, which we promptly replaced and restored configuration from backup. I still have copy of the local newspapers front page, praising how our company heroically saved the day to restore connection with outer world.
At that time I was already able to make up excuses that would have made BOFH proud, which saved my ass.
To add to all those valid points; you have to consider voltage drop across wires as well. It will affect much more severly low voltage/high amp DC system than high voltage/low current AC.
Yet LEDs don't really compete with CFLs yet. The article does mention that even a 60W incandescent equivalent is just experimental in LEDs, though CFLs have brightnesses at all levels even far past equivalence to 100W incandescents. Meanwhile, LEDs still generally aren't as efficient as their equivalent brightness CFLs. And LEDs' extra inefficiency puts heat into rooms that then require extra cooling, which consumes more energy.
What are you talking about?
The efficacy of halogen light is about 20lm/W, CFL around 50-70 lm/W
The LEDs, depending of drive current (and make/model) 70-100 lm/W http://en.wikipedia.org/wiki/Luminous_efficacy
So there's no way the halogen and CFL are far better than LEDs.
In fact, the LEDs combined with special optics have the huge advantage over the halogen,CFL and high/low pressure sodium lamps because of the precicely controlled light pattern. Conventional luminaries have usually reflector, which directs the light about to right direction, with efficiency of 30-70%.
In streetlights with LEDs it would mean no "hotspots" under the streetlight pole but evenly distributed light where it's needed and no unwanted glare, light pollution and etc. The even distribution means less lumens needed from light source. What matters is the luminaire efficacy. http://www1.eere.energy.gov/buildings/ssl/comparing_leds.html
The 100W LED module from the original article is not very good for applications where the light distribution is crucial because there's no (good) optics for the large array of tightly packed emitters in one package. Similar situation as with gas discharge and fluorescent lamps where the light is not sourced from one point (LED die is usually around 1mm2 in size) but more like area. LEDs, such as Cree XR-E, XP-E and Philips Lumileds Rebel have huge selection of aftermarket optics available for different applications. The efficiency of the optics ranges usually around 80-95%.
Another matter is cooling of the LEDs. The 100W module definitely needs active cooling to dissipate the generated heat in order to maintain the die temperature below 70-80 degree in Celsius. Temperatures above that will damage the phosphorous coating and die which results in rapid degradation of light output.
The reddish light from high pressure lamps is not better for dark environments because of the spectrum. Human eye when adjusted to dark (scotopic vision) is most sensitive to 505nm light which is cyan. The photopic (daylight vision) peak sensitivity is 555nm (green).
Bullshit. This applies to very cheap LED's bought from China (or similar). Leading manufacturers like Cree, Lumileds and the rest claim 75% of lumen maintenance after 50'000 hours.
Only one kid DDOS'ed goverment and news sites and created that mayhem? Right.
So nobody bothers to mention that the student who was arrested had a Russian name - Dmitri Galushkevich ?
Sure he may have the citizenship but he's not really Estonian. Just offspring of an immigrant.
And he wasn't the only kid around here who helped to DDOS.
I wonder where they pull the 2,5G upper limit number? In fibre, the most important properties are attenuation (at specific wavelengths) and dispersion. Both properties determine basically, what's the distance you can shine the light through the cable. Current G... whatever standard fibres have quite specific attenuation: very low at 1500nm area and somewhat less lower at 1300nm. Respectively long-haul and short-haul. Rest of the waveleghts are basically unusable.
Using DWDM one can multiplex many wavelengths into a single pair of fibre, delivering hundreds of Gbits over long distances. This is where the dispersion comes into a play - different wavelengths travel at different speeds.
UMTS/HSDPA can easily hit 700kbps, as can CDMA2000 1x EV-DO. EDGE hits 180kbps on a good day. On a REALLY good day.
It all depends, how much PDH/SDH/SONET channels are given to the RBS. HSDPA can support 14Mbit as well, just be the man and transport 8xE1 to the base station controller; for EDGE, usually 3(6) 64Kbit channels are given per cell.
The answer for light pollution is LED streetlights: directional light, lumen efficacy already past fluorescent lamps, also possible to choose better wavelength to aid scotopic vision Pat Mullins has some articles about the subject.
Slashdot Mirror
No, gross majority of white LED's use blue (so called royal blue, 450nm) as a base. Both, emitter and conversion to yellow are more efficient that way.
I used to work as a SDH/DWDM admin. In early 2000's, while my colleague screwed up a major firmware update on a STM1/4 ADM and I as senior (haha - I was in my 1st half of 20ies) admin had to drive up to site (since the affected node was unresponsive to management system). After many unsuccessful attempts to recover it, at about 3 am. I decided to hard reboot the node, which caused it to boot up from corrupt firmware bank (it had two of those); which in turn just erased all the configuration, including traffic connections (which is built very robust btw). Since the site was on a (relatively small) island and had only 2 ADM's at the time, I more or less cut off the entire communication with mainland. For morning, I had managed to get my colleagues to ferry me another, fully fitted ADM (our last resort backup scenario was to replace entire node) - but as it turned out, it was in a hurry fitted with cards with different firmware (entire network was in middle of upgrade process) which resulted in same kind of useless "brick" I had already at hand. Although it was very cool to fly ~200km/h to port and back in my sporty car, to pick up the spare (not many police on the island and I had a very good excuse). By the afternoon, my higher-up manager had mobilized a helicopter to personally deliver me fully functional ADM, which we promptly replaced and restored configuration from backup. I still have copy of the local newspapers front page, praising how our company heroically saved the day to restore connection with outer world.
At that time I was already able to make up excuses that would have made BOFH proud, which saved my ass.
To add to all those valid points; you have to consider voltage drop across wires as well. It will affect much more severly low voltage/high amp DC system than high voltage/low current AC.
Yet LEDs don't really compete with CFLs yet. The article does mention that even a 60W incandescent equivalent is just experimental in LEDs, though CFLs have brightnesses at all levels even far past equivalence to 100W incandescents. Meanwhile, LEDs still generally aren't as efficient as their equivalent brightness CFLs. And LEDs' extra inefficiency puts heat into rooms that then require extra cooling, which consumes more energy.
Do you have any numbers to back your claims?
Considering only lightsource efficacy, LED's have passed CFL quite while ago: http://en.wikipedia.org/wiki/Luminous_efficacy
What are you talking about?
.
The efficacy of halogen light is about 20lm/W, CFL around 50-70 lm/W
The LEDs, depending of drive current (and make/model) 70-100 lm/W
http://en.wikipedia.org/wiki/Luminous_efficacy
So there's no way the halogen and CFL are far better than LEDs.
In fact, the LEDs combined with special optics have the huge advantage over the halogen,CFL and high/low pressure sodium lamps because of the precicely controlled light pattern. Conventional luminaries have usually reflector, which directs the light about to right direction, with efficiency of 30-70%
In streetlights with LEDs it would mean no "hotspots" under the streetlight pole but evenly distributed light where it's needed and no unwanted glare, light pollution and etc. The even distribution means less lumens needed from light source. What matters is the luminaire efficacy.
http://www1.eere.energy.gov/buildings/ssl/comparing_leds.html
The 100W LED module from the original article is not very good for applications where the light distribution is crucial because there's no (good) optics for the large array of tightly packed emitters in one package. Similar situation as with gas discharge and fluorescent lamps where the light is not sourced from one point (LED die is usually around 1mm2 in size) but more like area. LEDs, such as Cree XR-E, XP-E and Philips Lumileds Rebel have huge selection of aftermarket optics available for different applications. The efficiency of the optics ranges usually around 80-95%.
Another matter is cooling of the LEDs. The 100W module definitely needs active cooling to dissipate the generated heat in order to maintain the die temperature below 70-80 degree in Celsius. Temperatures above that will damage the phosphorous coating and die which results in rapid degradation of light output.
The reddish light from high pressure lamps is not better for dark environments because of the spectrum. Human eye when adjusted to dark (scotopic vision) is most sensitive to 505nm light which is cyan. The photopic (daylight vision) peak sensitivity is 555nm (green).
Bullshit. This applies to very cheap LED's bought from China (or similar). Leading manufacturers like Cree, Lumileds and the rest claim 75% of lumen maintenance after 50'000 hours.
Only one kid DDOS'ed goverment and news sites and created that mayhem? Right. So nobody bothers to mention that the student who was arrested had a Russian name - Dmitri Galushkevich ? Sure he may have the citizenship but he's not really Estonian. Just offspring of an immigrant. And he wasn't the only kid around here who helped to DDOS.
So, in 2018, the "Blue Screen of Death" will get totally new meaning ;)
I wonder where they pull the 2,5G upper limit number? In fibre, the most important properties are attenuation (at specific wavelengths) and dispersion. Both properties determine basically, what's the distance you can shine the light through the cable. Current G... whatever standard fibres have quite specific attenuation: very low at 1500nm area and somewhat less lower at 1300nm. Respectively long-haul and short-haul. Rest of the waveleghts are basically unusable.
Using DWDM one can multiplex many wavelengths into a single pair of fibre, delivering hundreds of Gbits over long distances. This is where the dispersion comes into a play - different wavelengths travel at different speeds.
So, I guess next target who probably gets shot at sight is Leah Buechley with her LED tanktop or e-textile kit.
The answer for light pollution is LED streetlights: directional light, lumen efficacy already past fluorescent lamps, also possible to choose better wavelength to aid scotopic vision
Pat Mullins has some articles about the subject.
Or blow it up by flipping some wrong switch...
http://www.eetimes.com/news/latest/technology/sho
better now?
OLED's are nice for displays, but not enough lumen/watt efficiency for general illumination.w Article.jhtml?articleID=181503227/
LED's are improving much faster - 100Lm/W from Nichia to hit market soon:
http://www.eetimes.com/news/latest/technology/sho