On 27/03/2014 08:45, wrote:
On Thursday, March 27, 2014 2:54:18 AM UTC, Johny B Good wrote:

One thing I do know for a fact is that the mercury amalgam lamp is
less efficient than the straight mercury vapour lamp when each is run
at their optimum temperature. I'd overlooked the short tube effect on
efficacy so there's even less reason to disbelieve that a modern
linear tube and electronic fitting is the most efficient of all the
GLS lighting technologies to date.

Given further development of the LED lamp, notably more efficient
mass production as demand starts to increase to scale up mass
production to more economic levels, the price of such lamps will fall
to a level comparable to the equivilent of the 5 or 6 CFL lamps it
replaces. The efficiency needn't have to match or exceed a modern CFL
to succeed as a replacement since there are other benefits than just
the bare watts to lumens ratio involved in the TCO equation.
At the moment, most LED lamps are around 4 to 4 1/2 times more
efficient than a tungsten filament GLS lamp compared to a CFL's
efficiency figure of 5 times. An LED lamp isn't so far behind the CFL
and may yet match or even just exceed the efficiency of the CFL in the
not too distant future.

Folk have been saying that for decades, but it still hasnt happened. At some point it may, but not soon. CFL will continue to rule for years for GLS equivalents.

No they haven't been saying it for decades. High power LEDs are a
comparatively recent innovation they were indicator lamps originally.
CFL is essentially about to be phased out as LEDs have now won.

The latest consumer LED lamps are around 80lm/W for 8-10W bulbs which is
about comparable with fluorescents and *better* than most CFLs. There
are already 10W LEDs in production which at 100lm/W Cree XM-L would
trounce any fluorescent lamp.

Research grade white LEDs can now reach 250lm/W or more but their price
is still astronomical see for example Cree's recent announcement.

http://www.cree.com/News-and-Events/...00-LPW-fixture

This really is impressive because only the low pressure sodium vapour
lamp and the microwave pumped sulphur lamp are in that league.

As things stand, it's not the slightly lower efficacy compared to CFL
that's holding back the uptake of LED. It's the high price on GLS
lamps with barely adequate ratings that's the big turn off.

purchase price, premature failures, poor CCT & CRI, and inadequate power ratings. In short they're a bit of a niche product still.

The Philips and Samsung white LEDs do a pretty good imitation of
incandescent 3300K colour temperature. However, some of the cheap and
nasty LEDs have bad colour fringes and also cook their electronics.

The biggest problem for LED retrofit is getting the waste heat away from
the bulb since it all ends up as temperature rise with very little being
radiated away (and they die rather quickly at 100C or above).

The big problem for getting people to buy them is that people only see
the shelf price and forget about the true total cost of ownership
including the electricity used and replacement bulbs.

Same happens with loss leader sales of printers and mobile phones where
it is using of the "free/cheap" device that really costs the big money.

--
Regards,
Martin Brown