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Efficient Lighting

Discussion in 'Electronic Design' started by RST Engineering \(jw\), Sep 28, 2006.

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  1. Optics ain't my strong suit. I freely admit that. However, I have a 1000
    square foot single story steel shed I am lighting from photovoltaics and
    batteries/inverter. For a given amount of illumination per square squird of
    floor area, what is the most economical and efficient method of lighting?
    Plain old fluorescent fixtures? Compact fluorescent bulbs? Some other
    (relatively inexpensive) technology I'm not aware of? Are all fluorescent
    fixtures the same efficiency or are some designs/brands better than others?
    Same with compact fluorescents?

    I'd rather spend a little money to make the lighting efficient so that I can
    run the spectrum analyzer and sig gen a little longer from available power

  2. Joerg

    Joerg Guest

    Hello Jim,

    I recently converted much here to CFL after I found some that worked
    well and were cheap. Costco had a sweet deal (maybe still does) where
    utility subsidies brought the cost of 23W and 14W versions down to
    around a Dollar a piece. If you have a good reflector behind them they
    are really bright, especially the 23W versions which are claimed to
    produce the output of a 100W incandescent bulb (looks like they really
    do now). But mind that they produce EMI. Mostly conducted which you can
    muffle but also radiated which can't easily be filtered unless you place
    a mesh across the face. That mesh will be a dirt and spider web
    collector and can become a hazard.

    AFAIK you can eke out a wee bit more efficiency if you build your own
    inverters and then use larger fluorescent tubes. Plenty of circuits on
    the web.

    When it gets cold fluorescents need a long time to reach their target
    output. Meaning more than just a few minutes. When it gets really hot I
    had some of the industrial long tubes cycle off.
  3. Rich Grise

    Rich Grise Guest

    Put in some windows? Maybe skylights? :)

    Good Luck!
  4. For battery operation I'd sure be looking at compact fluorescent bulbs. El
    cheapo ones have crappy phosphors but I got some 15 watt for $1 ea at the
    local grocery store that are really high output.
  5. GregS

    GregS Guest

    Its obviously efficient to use as little light as possible, in small areas.
    That said, the compact florescents are pretty good but their light output
    is not going to equal a 4 foot fluorescent

    I just installed lights in my garage and used 10 4 foot bulbs, 3300 Lumens
    each at 40 watt each. I wasn't worring about efficiency, just light output.
    I must examine some lamps installed above my head. The are very much brighter
    than the other fluorescents around here. I wonder what the Lumens rating is?
    Well I just found out. Its less than I expected, but interesting. The GE Ecolux
    is a 32 watt and outputs 3000 Lumens. Its still looks
    superbright to me SPX41.

  6. It's all in the phosphors.
  7. You might want to ask this question over on

    If they are still speaking to us, that is. ;-)

    You might also want to give a few more details about what sort of
    lighting levels (or what kind of tasks will be performed) in this
    structure. Efficiency might be a factor of lighting levels, CRI, etc.
  8. Since we don't have the details that Paul has mentioned, I'm
    going to go out on a limb and generalize here.

    For general lighting it's hard to beat the efficacy of high
    quality 4-foot T8 (1 inch diameter) fluorescent lamps on
    quality electronic ballasts and mounted in high performance
    fixtures. Compact fluorescent lamps are less efficient than
    linear fluorescent lamps. Incandescent lamps are much less
    efficient. Metal halide lamps come close, but their have
    terrible lumen depreciation so their mean efficacy over life
    is worse than fluorescent lamps.

    My generalization falls apart if your application does not
    need uniform light levels. If you can use task lighting in
    critical areas and lower light levels in other areas then
    there may be better solutions.

    All linear fluorescent lamps are not equal and all ballasts
    and fixtures are not equal. The lap data provided by the
    "big three" can generally be assumed to be accurate so you
    can compare different T8 lamps so discover their minor

    Some people prefer T5 linear lamps, but they are no more
    efficient than T8 lamps of the same length when both are
    operated on electronic ballasts.

    If you are operating from DC power I would suggest
    purchasing ballasts designed to operate from your DC power
    source instead of using AC ballasts and a DC-to-AC
    converter, which will only waste power.

    I'm sure you will get other opinions.

    Vic Roberts
    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.
  9. JohnR66

    JohnR66 Guest

    It would be necessary to know the available power to give you a good answer.
    Fluorescent is the way to go, but you could limited to single 9 watt lamp to
    several multi tube 4' fixtures depending on available power and required
  10. Thanks for all the answers, and more thanks for all the questions. The
    "metal building" in question is an aircraft hangar that doubles as my
    airport electronics lab. I use the lab to validate and true up designs done
    for both my manufacturing company ( and my monthly
    magazine column designs (

    The lighting will be used for maintenance on the aircraft and general hangar
    lighting for the machine shop, the parts bins, and the like. Each
    electronics bench has its own individual two-tube fluorescent fixture that
    gives me very good lighting on a microscopic scale.

    As to "how much power is available", the answer is that I've got a 3 kW
    gasoline generator that kicks in when the voltage drops below a critical
    level on the 12 volt batteries being charged by the solar panels. The
    answer is that I'm limited to something below 3 kW over the long haul, but
    could give you 5 kW on a short term basis.

    Now, since the consensus seems to be that a fluorescent fixture with 4'
    bulbs is the most efficient, how do you select the fixture. I understand
    that the bulbs themselves have a lumen/watt rating on them, but how do you
    determine the efficiency of the ballast/fixture itself?

  11. Robert Baer

    Robert Baer Guest

    ....and get the windows from Gates...
  12. Richard

    Richard Guest

    Just pick up a two bulb fixture with a large reflector and an electronic
    ballast and then pick up a pair of 25 watt bulbs in place of typical 32 watt
    bulbs. If you are going with 2 two bulb fixtures better to get a 4 bulb
    ballast and wire the two fixtures together with that one ballast rather than
    use two ballasts. You might even consicer single bulb fixtures if you can
    find them with a large reflector and use a two or four bulb ballist and up
    to four fixtures connected together. There are even 17 watt bulbs out there
    if you can find them.

  13. JohnR66

    JohnR66 Guest

    NOT recommended. You just can't install any wattage fluorescent tube in any
    fixture even if it fits. The voltage and current characteristics of the
    ballast is designed for a particular bulb.
  14. JohnR66

    JohnR66 Guest

    When speaking of available power. How much is available for lighting? Lets
    say you supply 3 kw continuous. What is the maximum load your equipment puts
    on the supply. Subtract that from the total and this is what is left for
    lighting. Wouldn't hurt to give it a 20% cushion.
    You probably should have an electronic engineer evaluate your situation. You
    might have to deal with power factor correction to get the best out of your

    Electronic ballasts will give an edge in efficiency. If the building is
    close to a square in shape, I can see four 8' tube fixtures (two bulbs per
    fixture) in two rows across the ceiling if it is sufficiently high. It would
    use under 1 kw.

  15. TKM

    TKM Guest

    Agree. If the lamp type is listed on the ballast label, then that lamp is
    O.K. to use. If the lamp is not listed, check the ballast manufacturer's
    web site and the ballast listing. The ballast manufacturer wants to make
    that ballast as widely used as possible, so if the lamp is not listed for
    use on a particular ballast, there is a reason.

    Terry McGowan
  16. 8-foot fluorescent lamps are slightly more efficient than
    4-foot lamps of the same type. I suggested 4-foot lamps
    because they are almost as efficient as 8-foot lamps, are
    much more convenient, are available in a greater variety of
    types and colors and may be less expensive.

    To find the most efficient ballast you will need information
    that is available on the ballast data sheet and may also be
    printed on the ballast labels. To compare the efficiency of
    various ballasts for the same type and number of lamps,
    compute the Ballast Efficiency Factor (BEF). The BEF is the
    Ballast Factor (BF) divided by the ballast input power. You
    can only compare the BEF for ballasts designed to operate
    the SAME TYPE AND NUMBER OF LAMPS. Also, if any ballast
    under consideration operates more than one type of lamp,
    remember to use the BF and input power for the same type and
    number of lamps when you compare ballasts.

    If you decided to use a DC-input ballast, as I suggested to
    eliminate the additional losses of an DC-to-AC converter,
    then your ballast choices will be limited.

    I normally don't work with fixtures, but you can also find
    fixture efficiency data on fixture data sheets. I would not
    choose 'any" fixture, as has been suggested.

    Vic Roberts
    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.
  17. 25-watt lamps will reduce power consumption, but will also
    reduce light levels. For a new installation designed for a
    specific light level it is not clear that 25-watt lamps
    provide either the most efficient or most economical

    Vic Roberts
    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.
  18. My experience is that in compact fluorescents, lousy phosphors are only
    or almost only used in ones available at dollar stores, or of brands
    usually found at dollar stores.

    - Don Klipstein ()
  19. That's about 100 lumens per watt.
    The best white light LEDs can do about half that, which is worth
    considering for small lights eg bench spotlights etc.
  20. RickR

    RickR Guest

    We should keep in mind just how much difference there is between some
    of these options. In many cases we could be talking about fractions of
    a percent, that could be easily overwhelmed by other factors.

    Assuming that $$ are not unlimited you may soon find a region of
    vanishing returns.

    It is not well understood by the general public how the temp of the
    bulb wall effects output and therefore efficiency. In a metal walled
    structure I would look *very* closely at that.

    For maximum efficiency you must start with how the light is distributed
    over the area of interest. Then (for fluorescent) the lamp and ballast
    as a pair! Then move to the fixture construction.

    Furthermore you are using a 12VDC source and the options in ballast are
    quite limited.

    Richard Reid, LC
    Luminous Views
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