DIYbanter - View Single Post - Sale of Incandescent Bulbs to End on Tuesday?

Andrew Gabriel

In article ,
(Richard Tobin) writes:
In article ,
Andrew Gabriel wrote:

But in any case you can still buy the 30%-less-power halogen
bulbs in the traditional format. I can't see any reason not
to use them.

They're also nearly 30% dimmer.

I have been replacing the 60W candle bulbs in a 3-bulb fitting with
the 42W halogen bulbs. They're noticably brighter than the old ones.
If course, the old ones are... old, but I don't think traditional bulbs
deteriorate that much.

They do actually. As the filament evaporates, the inside of the
bulb slowly darkens. Furthermore, as the filament evaporates,
its resistance increases, current drops, and power drops, so
you get two effects significantly dimming a filament lamp as it
ages. You may be replacing a frosted lamp with a clear one, and
clear ones are more efficient. The etched frosted lamps we used
to use lose around 2% of the light in the frosting. Due to the
hazards of handling the hydrofluoric acid used for the etching,
pearl lamps are now mostly frosted with an internal powder
coating, and this is less efficient (I don't have a figure though).
Many decorative lamps such as golf balls and candles have painted
coatings, and these are much less efficient, often losing some
20% or more of the light output verses the clear equivalent.

Halogen lamps can be built to be more efficient than non-
halogen filament lamps, or last longer, or some combination
between on a sliding scale. In nearly all consumer lamp products,
halogens are designed for longer life because people won't pay a
price premium for halogen lamps which only have the same
expected life as a non-halogen filament lamp costing a fraction
of the purchase price.

The other problem is that mains filament lamps (halogen and
non-halogen) get less efficient as you build them at lower
power ratings, and that weighs in against these reduced power
replacement lamps.

Philips built some GLS retrofits which use a low voltage
halogen capsule and small switched mode power supply in the
lamp base, similarly to CFL control gear. Those do deliver
real energy usage savings because the low voltage halogen is
so much more efficient than mains voltage filaments. I forget
the exact figures, but something like a 20W version was
equivalent to a 40 or 50W conventional lamp. Problem with
these was that a) you can't go higher than about 20W because
the heat will fry the integral switched mode power supply,
and b) the cost of these was so high, that even taking the
energy cost reduction into account, you are still well out
of pocket. There's also only a very tiny market for people who
care about their energy usage enough to spend extra on lamps,
but who insist on using filament lamps for general lighting.

--
Andrew Gabriel
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