Re: What is the Future of LED\'s
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PeLu said:
It depends what you define as 'white' light, the CRI is not the best scale for it (as mentioned zillion times in other threads). Usually the theoretical maximum for white light and photopic vision is rated around 200lm/W.
When you remove the upper and lower parts of the spectrum you may get higher, but then you just can't see some colours correctly.
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That's true of course. While I think decreasing the efficiency from a theoretical 400 lm/W with a CRI of 80 to 320 lm/W with a CRI of 98 is worthwhile, I'm not so sure aiming for a CRI of 100 is worth the additional decrease in efficiency of close to 40% except for lighting intended for very critical work. Most people are hard pressed to tell the difference between a CRI of 90 and one of 100, let alone between 98 and 100. However, I definitely notice that lighting with a CRI of 80 seems lacking. I'm not so sure if 80 should be considered suitable for general lighting. For utility areas and streets it is certainly fine, but I think 95+ should be the goal for lighting in our homes, stores, and restaurants.
As for efficiency, who really knows where we'll end up and when. Efficiency isn't increasing as rapidly as first hoped, but then again with any new technology often the pace of development is often overestimated. As an aside, similar high hopes were held for thermoelectric refrigeration 40 years ago. I forgot the exact goal (it was several times higher than existing devices), but the researchers felt it would be reached within five years. Fourty years later we have devices which are only maybe 35% more efficient, and that is due mostly to manufacturing improvements. While I have little doubt we'll eventually have solid-state light sources close to 100% efficiency, the real question is will it be in ten years via a breakthrough or in fifty via slow process improvements? I also think the concept of a light source emitting at a single color will become obsolete long before then. We'll likely have lamps with emitters centered at several (three to five) frequencies. Using feedback you'll be able to make the lamp put out white light at any color temperature you desire, plus possibly almost any color of the rainbow.