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High Efficiency White LEDs

Discussion in 'Lighting' started by JohnR66, May 29, 2007.

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  1. JohnR66

    JohnR66 Guest

    After trying a couple Cree XR-E based flashlights, I must say I'm impressed.
    I've heard way over 100 lumens per watt designs operating in the labs
    several months ago by various manufacturers, but nothing of late. Anyone got
    the inside scoop?

    As for the XR-E LEDs, I'm aware the efficiency drops due to operating die
    temps, but even so, the l/w figures seem to remain in the upper range of
    CFLs (50-70 range).

    John
     
  2. Cree was bragging about 131 lm/W from a low power LED, and
    last week at LS:11 Nichia was bragging about one over 150
    lm/W. However, these are all at a junction temp of 25C
    which cannot be achieved without a refrigerated heat sink,
    and they are not power devices, which are less efficient.
    In my mind, the more important question is what is the
    minimum guaranteed efficacy of a LED that a person can
    actually buy, measured at a junction temperature that can be
    achieved in a real application. Last time I checked, about
    6 months ago, the answer was "about 40 lm/W" and at a cost
    per lumen that was at least 10 times that of a CFL.

    BTW- I learned at LS:11 that the LED manufacturers are well
    aware that they could solve white LED color issues by using
    UV instead of blue LEDs as the pump, but they don't want to
    take the Stokes Shift hit to the efficacy.

    --
    Vic Roberts
    http://www.RobertsResearchInc.com
    To reply via e-mail:
    replace xxx with vdr in the Reply to: address
    or use e-mail address listed at the Web site.

    This information is provided for educational purposes only.
    It may not be used in any publication or posted on any Web
    site without written permission.
     
  3. JohnR66

    JohnR66 Guest

    The next few years should prove interesting. The current most efficient LEDs
    are ideal for portable lighting. They do have a ways to go for general
    lighting where price, CRIs and color temp are more of importance.
    John
     
  4. I agree that there are a number of applications where LEDs
    are an ideal light source. These include any type of
    colored indicator lamp, and low lumen directed light
    applications, such as flashlights and task lamps.

    However, data available from the US DOE states that 98% of
    the lighting energy in this country is used by high lumen
    white light sources. My primary interest is in energy
    conservation. LEDs will not reduce lighting energy
    consumption in the US until they are more efficient than
    linear fluorescent lamps and metal halide lamps and their
    cost per lumen has dropped to a level consistent with their
    efficacy and life advantage over these existing light
    sources.

    --
    Vic Roberts
    http://www.RobertsResearchInc.com
    To reply via e-mail:
    replace xxx with vdr in the Reply to: address
    or use e-mail address listed at the Web site.

    This information is provided for educational purposes only.
    It may not be used in any publication or posted on any Web
    site without written permission.
     
  5. TKM

    TKM Guest

    While I agree with Vic overall, there are some white light applications
    where the use of LEDs will result in energy savings now. I'm working with
    the Am. Lighting Association and several other groups to identify others.
    We're using "application efficiency" as the metric or, roughly, the watts
    required for suitable illumination of the task involved and we realize that
    such a a definition is subject to passionate interpretation.

    But, we think the use of easily-available state-of-the art LEDs for the
    following would result in energy savings: portable task lights, residential
    under-counter and in-furniture lights, step lights, and other outdoor and
    landscape lighting applications. I've just ordered the parts for an
    all-LED landscape lighting project, so check back in late July for a report.

    Terry McGowan
     
  6. Terry - I agree that the directional nature of LEDs should
    be taken into account and I should have included that in my
    statement about "more efficient". I do endorse
    "application efficacy" and agree that there are still
    multiple definitions for this metric - we even use different
    names :)

    As for the applications you mention, I agree they are all
    potentially good applications for LEDs, but fail to address
    those applications where we use 98% of lighting energy in
    the US.

    --
    Vic Roberts
    http://www.RobertsResearchInc.com
    To reply via e-mail:
    replace xxx with vdr in the Reply to: address
    or use e-mail address listed at the Web site.

    This information is provided for educational purposes only.
    It may not be used in any publication or posted on any Web
    site without written permission.
     
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