LEDs are also expensive (at least compared to tungsten filaments), and up until very recently only came in red or (a bit later) green. Advances in semiconductor photonics recently made possible the creation of blue LEDs, which thanks to phosphorous, can be used to make white lights. Of course they're still no good for growing plants as narrow-band as they are. You will however notice we've started seeing LOTS of white-LED lighting solutions popping up since then.
As to this technology I see two limits: first, area (since the panels aren't any more efficient than the old ones, they can't get anything like that mythic "power America with a field in Arizona" energy flux) and second, materials. However I'm already pretty hopeful since the materials don't need to be ion-implanted into a crystaline matrix the way silicon dopants need to be.
Mmm, "recently" is a subjective word of course, but when I started looking at LED lighting about six years ago the hue of the lighting could be described as yellow-orange. Not great for home lighting in general. Then about three years ago I started seeing ads for LED lighting with a "moonlight" color - white with a bluish cast to it. It still wasn't great for home lighting, but it was a remarkable improvement, and I could definitely see using it for accent lights.
If the claims are to be believed (I've only been checking about every six months to see the current state of the art, so I can't verify the current crop personally) we have now achieved real white light LEDs. The problems that remain are butt-ugly designs (really guys, if you're going to compete with the light bulb don't make it uglier than a light bulb), training in LED light use (electricians tend to get shy when it comes to doing things that might get them sued, and contrary to what has been said LEDs for home lighting can get quite hot), and of course general resistance to change.
You'll notice they're replacing flashlights at a good clip these days, but I'm pretty sure that to get a 100W-incandescent-equivalent LED array you'd need, ah, a LOT of them, which would be expensive.
LEDs also suffer from the fact that they're natively DC and low voltage (as diodes, they tend to "clamp" at 0.7v per diode junction) but hey, guess what solar panels are?
Indeed, these are two technologies that could match up very well, although infrastructure issues (e.g. parallel AC and DC wiring) are non-trivial.
Just a note: the voltage can be modified by running them in series. A typical red LED runs at a voltage of 1.4V DC, but if you have a 24V DC supply, you can run 16 of them in series with a relatively small current-control resistor. Similarly, solar panels can be linked in series to get more voltage, which is good for distribution systems. (Resistive power transmission loss drops as voltage increases.)
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(no subject)
Date: 2007-12-22 05:02 pm (UTC)As to this technology I see two limits: first, area (since the panels aren't any more efficient than the old ones, they can't get anything like that mythic "power America with a field in Arizona" energy flux) and second, materials. However I'm already pretty hopeful since the materials don't need to be ion-implanted into a crystaline matrix the way silicon dopants need to be.
(no subject)
Date: 2007-12-22 09:34 pm (UTC)If the claims are to be believed (I've only been checking about every six months to see the current state of the art, so I can't verify the current crop personally) we have now achieved real white light LEDs. The problems that remain are butt-ugly designs (really guys, if you're going to compete with the light bulb don't make it uglier than a light bulb), training in LED light use (electricians tend to get shy when it comes to doing things that might get them sued, and contrary to what has been said LEDs for home lighting can get quite hot), and of course general resistance to change.
Lesse, links: There's a PDF here from an on-line magazine [LEDs] ... are important enough to have their own category within the Lighting For Tomorrow (LFT) contest.
Huh, it appears that white LEDs are not necessarily made by mixing red, green and blue LEDs anymore, if Wikipedia is to be believed.
(no subject)
Date: 2007-12-22 10:26 pm (UTC)LEDs also suffer from the fact that they're natively DC and low voltage (as diodes, they tend to "clamp" at 0.7v per diode junction) but hey, guess what solar panels are?
Natively DC and low voltage.
Because they're diodes TOO.
(no subject)
Date: 2007-12-24 06:56 pm (UTC)Just a note: the voltage can be modified by running them in series. A typical red LED runs at a voltage of 1.4V DC, but if you have a 24V DC supply, you can run 16 of them in series with a relatively small current-control resistor. Similarly, solar panels can be linked in series to get more voltage, which is good for distribution systems. (Resistive power transmission loss drops as voltage increases.)