Lightbulbs Can Last Centuries
And Why They Don't Make Them That Way
Longest-Burning Bulb On Record - 1 Century!
Easy Way to Make Bulbs Last For Centuries
Why It Does Not Pay To Do So.
What Does Pay Off!
The longest-lasting incandescent light bulb on record is at a fire station
in Livermore, California. It was installed on June 8 1901, was still
working on June 8 2001, was always on except for a time it was moved
and for any power failures affecting it, and as far as I know it is still
in use and working.
Details in the Centennial Bulb web
site.
Simply operate a light bulb at half its rated voltage. Get a 230V light
bulb from Europe and operate it in the USA at 120V. Believe me, that will
do the trick! Life expectancy is generally about inversely proportional to
voltage to the 12th power. At half voltage, a light bulb will last
something like 4,000 times its rated life expectancy - give or take.
Having the filament run at a lower temperature reduces the energy
efficiency of a light bulb. Even at usual operating temperatures for
750-1,000 hour lightbulbs, a tungsten filament produces about 93 percent
of its radiation in the infrared. That does not mean good efficiency at
producing visible light. With a lower filament temperature, the percentage
of radiation in the infrared increases and the percentage of radiation in
visible light decreases. A light bulb that is 6-7 percent efficient in
producing visible light at full voltage is only about 2 percent efficient
in producing visible light at half its rated voltage.
I consider it a safe bet that the Livermore "century bulb" is even less
than 2 percent efficient at converting electricity to visible light.
Since the cost of producing a given amount of light with incandescent
lamps is usually mostly the cost of electricity rather than the cost of
the light bulbs, it does not pay to make them last extremely long.
In many but not all places, compact fluorescent lamps pay off - both by
lasting longer than most incandescent lamps and by being generally 3 times
as energy-efficient.
Please read these pages so you can avoid some disappointments as well as
know where to get some of the better ones:
General Info by Sam Goldwasser.
Some Helpful Hints and Brand/Model-specific Test
Results.
In office buildings, schools and hospitals, non-compact fluorescents
(usually 4 feet long) are almost always used since these are more
efficient than smaller sizes. Due to economies of volume production,
4-foot bulbs don't cost more than smaller sizes.
One way to minimize lighting cost is to use a smaller number of higher
wattage light bulbs instead of a larger number of lower wattage
ones. Minimize the bulb count as much as possible without making light
distribution too uneven or exceeding the ratings of the fixture. (Many
fixtures have a 60 watt bulb wattage limit!) You spend less by buying and
replacing fewer bulbs. In addition, higher wattage bulbs tend to be more
efficient than lower wattage ones - for one thing, thicker filaments can
be operated at a slightly higher temperature for a given life expectancy.
For another, with reduced per-watt bulb costs, the cost of bulbs becomes
less important (compared to the cost of electricity) for higher wattages
so higher wattage bulbs are designed to run hotter and lower wattage bulbs
are designed to last longer (which makes them run less efficiently).
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Written by Don Klipstein.
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