Re: Ball park lighting figures?

From: Don Klipstein (don_at_manx.misty.com)
Date: 12/06/04 

Date: Mon, 6 Dec 2004 01:27:28 +0000 (UTC)

In article <pxCrd.7290$6W2.398449@phobos.telenet-ops.be>, CWatters wrote:
>I know there are a lot of variables but could someone point me to ball park
>figures for various lighting technologies?
>
>For example manufacturers (optimistically?) claim an 11W flourescent lamp
>produces about the same amount of light as a 60W incandescent.

  Roughly, roughly, a compact fluorescent lamp produces as much light as
an incandescent lamp of 3-4 times as much wattage. Good compact
fluorescents normally produce 4 times as much light as good incandescents,
except compact fluorescents can be dimmed by non-ideal temperatures, heat
buildup in fixtures, etc.
  Another thing - if you put a compact fluorescent in a fixture designed
for an incandescent, the light may not be distributed in a less favorable
manner than that of the incandescent.

  Please check out my compact fluorescent stuff at:

http://www.misty.com/~don/cfx.html

  "Standard" fluorescents of the more usual "shades of white", especially
the 4 foot T8 (1 inch diameter) ones, are a little more efficient than
compact fluorescents.

  One more thing: Fluorescent lamps and incandescent lamps can vary
significantly in efficiency with manufacturer and model due to various
issues of design and quality.

  For example, in the USA a "standard" 100 watt incandescent lamp by one
of the "Big Three" makers produces 1710 lumens, sometimes claimed as high
as 1730 or 1750. I see off-brand 100 watt incandescents in packages
claiming as low as 1100 lumens, claimed life expectancy not exceeding that
of longer-life "Big Three" 100W lamps claimed over 1600 lumens, and I
don't only see such junkers in dollar stores.

  Compact fluorescents with magnetic ballasts are usually less efficient
than ones with electronic ballasts and they also have quality issues.

  Non-compact fluorescents also suffer from ballast issues. Also, ones
with color rendering index higher than 86 or so have less photometric
output than most usual ones with rated color rendering index in the range
of 53 to 86.

>What about LED lamps that are now becoming available? How do they compare?
>Would a 4.5W output LED be bright enough for use as a ceiling mounted
>downlighter in a kitchen etc

  The best available white LEDs have typical overall luminous efficacy
around 1.5 to 2 times that of most home-illumination-purpose
incandescents, assuming you have no losses in any ballast/driver
circuitry.

  There are some problems:

1. LEDs are extremely expensive for their light output. 5 watt LEDs cost
quite a few $$. I just checked out Quickar Electronics, which is a place
to get just one or a few, and I just saw a price for a 5 watt white one at
about $30.
  Time for that to be paid back by electricity savings over a 15 watt
incandescent, assuming electricity cost of 10 cents per KWH (roughly the
USA national average): 30,000 operating hours. Don't forget the cost of
the ballast or driver circuitry even if you can get a better price on the
LED.

1a. White LEDs do not last forever. Higher figures that I do not know
to be dishonest or wrong for claimed life expectancy are 50,000 hours. It
is easy to get a fraction of that. The main problem is that the usual
white LEDs have a phosphor that wears out during use. This will
exacerbate the economic disadvantage of using LEDs of late 2004
state-of-the-art over more usual light sources for home lighting.

2. As Vic Roberts (someone else who you may run into when the subject is
illumination with LEDs) likes to point out, LEDs have another issue:
  They vary considerably in light output from one piece to another, even
of the same part number. They also vary a little in voltage drop at a
given current, often and maybe usually without much positive correlation
in light output at a given current. The best minimum guaranteed overall
luminous efficacy for a higher power white LED that I have heard of so far
is about 16.6 lumens per watt, which is just a little higher than that of
most but not all common incandescents. And this requires a rather
optimistic thermal assumption of a heatsink being at 25 degrees C and no
losses in the ballast/driver circuit.

  LEDs do have their place already in more specialized lighting
applications such as flashlights and traffic signals. To see how LEDs get
ahead in those applications, please check out this page of mine:

http://www.misty.com/~don/lede.html

>Anyone know of some good sources for LED based lamps for use in buildings?

  - Don Klipstein (don@misty.com, http://www.misty.com/~don/index.html)

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