Anders Hoveland
Enlightened
- Joined
- Sep 1, 2012
- Messages
- 858
I don't think LEDs have a future, at least not in their current form.
While LEDs are ideal for many applications, general lighting is not one of them. I know this post is probably going to enrage many members here, since this forum is filled with LED enthusiasts. Do not get me wrong, LED is great for traffic lights and flashlights.
If you think about it, white LED light is mostly just an orangish phosphor with a specific blue frquency thrown in. It's not really white light.
No matter how enhanced white LEDs are, many people are still going to find them off because of that narrow deep blue frequency spike. The harshness of blue LED light is due to two things. First, the short wavelength, it is "hard" blue frequency light. This makes it appear a little purplish, but also makes it more difficult for the eye to focus on. In fact, the deep blue wavelength peak from white LEDs (465nm) is almost indigo (considered to start at 464 nm). The other problem is that the narrow concentration into a frequency spike makes it appear harsh rather than soft. Typically light sources are perceived as "softer" if they have a more smoothly distributed spectrum without any sharp spikes.
I think the reason we have not heard more complaints about the quality of LED light is simply the fact that so few consumers are actually using them. The people who have actually bought LED lighting for their homes at this time are probably not typical of the wider consumer base. Technology oriented people who just want the latest new technology in their home - typically men who are not too concerned about the quality of light, "environmentally conscious" consumers , most of whom were already using CFLs before they switched to LEDs, so they really have nothing to complain about in comparison. And most of the remainder are only using LED downlighting in their kitchens. This is not really the same as using LEDs in the rest of the house. Many people prefer "whiter" (more bluish) light in the kitchen, if you think about it, while many homes are using fluorescent lighting in their kitchen, few houses had fluorescent lighting anywhere else.
We will probably see LED replace more outdoor lighting applications, and be used more frequently in street lighting, but I do not think they are going to take over entirely. Some cities will switch to LED for the clean white colored light and low maintenance. But the fact is that many cities are discovering that LED street lighting is not all that it is claimed to be. It is can be more glareful to drivers (both because of the point-like light sources from a non-diffused LED array, and because of the deep blue frequency which is difficult to focus on) and often results in poorer useful illumination than the claimed equivalency ratings (the ambient light from the old streetlights contributes more to illumination than many realize, and the supposedly better scoptic index for blue LED can be misleading for fast moving objects). While many consider low pressure sodium to be ugly, it does at least have a warm glow without glare and is more comfortable to drive under. And besides, low pressure sodium has a similar efficiency to commercially available LED street lamps. While LEDs could be made with much lower CCT, I doubt this will be used for street lighting because of the sacrifice in efficiency. The latest technology of ceramic metal halide can offer higher CRI than standard LED.
But this post is not really about street lighting. I just do not think LEDs are really going to take over our homes. And I have doubts we will see LEDs replace fluorescent lighting in schools and offices any time soon.
I just think LED lighting is, in many ways, mostly just a big fad right now. LED technology has a long ways to go before it is ready for lighting our homes. As it is right now, the technology is essentially just a blue chip with orange phosphor. There needs to a new basic concept, and better phosphor compositions need to be developed. I especially think doped ZnS phosphors hold promise for more even frequency coverage in the blue part of the spectrum (or possibly blue halophosphate).
The lighting industry and government seem to be spending a lot of resources pushing a technology that in many ways simply is not ready to replace everything. And I think we also need to get away from the idea that quality of light needs to be sacrificed for the sake of efficiency. When it comes to indoor lighting, if there is a phosphor that has a moderately lower efficiency but gives better spectrum coverage, it should be used.
LED is not the only potential technology. All the research is currently focused on LED because it is seen as the most efficient and promising, but there are other potential technologies being neglected, ESL, sulfur plasma, and hybrid light sources, for example. And I think students and office workers would benefit far more if more attention was given to natural lighting and light tubes. There are far more potential efficiency gains to be made from better architectural design than LED lighting. Smart motion detector systems could save more energy than LEDs in most situations (though fluorescent does not work so well with motion activation, for several reasons).
While LEDs are ideal for many applications, general lighting is not one of them. I know this post is probably going to enrage many members here, since this forum is filled with LED enthusiasts. Do not get me wrong, LED is great for traffic lights and flashlights.
If you think about it, white LED light is mostly just an orangish phosphor with a specific blue frquency thrown in. It's not really white light.
No matter how enhanced white LEDs are, many people are still going to find them off because of that narrow deep blue frequency spike. The harshness of blue LED light is due to two things. First, the short wavelength, it is "hard" blue frequency light. This makes it appear a little purplish, but also makes it more difficult for the eye to focus on. In fact, the deep blue wavelength peak from white LEDs (465nm) is almost indigo (considered to start at 464 nm). The other problem is that the narrow concentration into a frequency spike makes it appear harsh rather than soft. Typically light sources are perceived as "softer" if they have a more smoothly distributed spectrum without any sharp spikes.
I think the reason we have not heard more complaints about the quality of LED light is simply the fact that so few consumers are actually using them. The people who have actually bought LED lighting for their homes at this time are probably not typical of the wider consumer base. Technology oriented people who just want the latest new technology in their home - typically men who are not too concerned about the quality of light, "environmentally conscious" consumers , most of whom were already using CFLs before they switched to LEDs, so they really have nothing to complain about in comparison. And most of the remainder are only using LED downlighting in their kitchens. This is not really the same as using LEDs in the rest of the house. Many people prefer "whiter" (more bluish) light in the kitchen, if you think about it, while many homes are using fluorescent lighting in their kitchen, few houses had fluorescent lighting anywhere else.
We will probably see LED replace more outdoor lighting applications, and be used more frequently in street lighting, but I do not think they are going to take over entirely. Some cities will switch to LED for the clean white colored light and low maintenance. But the fact is that many cities are discovering that LED street lighting is not all that it is claimed to be. It is can be more glareful to drivers (both because of the point-like light sources from a non-diffused LED array, and because of the deep blue frequency which is difficult to focus on) and often results in poorer useful illumination than the claimed equivalency ratings (the ambient light from the old streetlights contributes more to illumination than many realize, and the supposedly better scoptic index for blue LED can be misleading for fast moving objects). While many consider low pressure sodium to be ugly, it does at least have a warm glow without glare and is more comfortable to drive under. And besides, low pressure sodium has a similar efficiency to commercially available LED street lamps. While LEDs could be made with much lower CCT, I doubt this will be used for street lighting because of the sacrifice in efficiency. The latest technology of ceramic metal halide can offer higher CRI than standard LED.
But this post is not really about street lighting. I just do not think LEDs are really going to take over our homes. And I have doubts we will see LEDs replace fluorescent lighting in schools and offices any time soon.
I just think LED lighting is, in many ways, mostly just a big fad right now. LED technology has a long ways to go before it is ready for lighting our homes. As it is right now, the technology is essentially just a blue chip with orange phosphor. There needs to a new basic concept, and better phosphor compositions need to be developed. I especially think doped ZnS phosphors hold promise for more even frequency coverage in the blue part of the spectrum (or possibly blue halophosphate).
The lighting industry and government seem to be spending a lot of resources pushing a technology that in many ways simply is not ready to replace everything. And I think we also need to get away from the idea that quality of light needs to be sacrificed for the sake of efficiency. When it comes to indoor lighting, if there is a phosphor that has a moderately lower efficiency but gives better spectrum coverage, it should be used.
LED is not the only potential technology. All the research is currently focused on LED because it is seen as the most efficient and promising, but there are other potential technologies being neglected, ESL, sulfur plasma, and hybrid light sources, for example. And I think students and office workers would benefit far more if more attention was given to natural lighting and light tubes. There are far more potential efficiency gains to be made from better architectural design than LED lighting. Smart motion detector systems could save more energy than LEDs in most situations (though fluorescent does not work so well with motion activation, for several reasons).
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