A History of Lamp Technology by historyman


									History of Lamp Technology.

Compiled by Alastair Sherry.

The history of the light bulb can certainly be traced back to Messrs Swan & Edison,
but it is equally certain that they would not have made their respective leaps without
the benefit of Michael Faraday’s researches in to electricity. His discoveries in the
1830s of the electric motor and the dynamo allowed for the continuous supply of
usable currents of electricity to make usable light a viable option.

Although gas lighting predominated, and indeed continued until after the end of the
Second World War, the first appearance of electric lighting was around 1880 and
followed the Edison and Swan first usage of the incandescent lamp. These were very
crude devices as were the materials available to them. This resulted in efficacies of a
very low level (less than 5 lm/W) at a correspondingly high cost. In the main this
form of lighting was restricted to the very well off and to some commercial and retail
establishments. The 1920s had improved the lamp by the introduction of tungsten
filament and filling the bulb void with gas to increase the life of the filament by
reducing the tungsten evaporation.

Research at the turn of the century was ongoing into the area of gas- filled lamps, as it
was anticipated that the next generation of lamps would need improvements in the
areas of efficacy and longevity, but the restricting factor here was the lack of a
suitable current limiting device. Work continued for many years in this field and the
first commercial installation of low pressure sodium lamps was installed at Purley
Way, Croydon in 1932. Lamp efficacy was now increased to some 50 lm/W. In the
same year the High Pressure Mercury lamp saw its introduction as street lighting in
Wembley Middlesex with efficacies around 36 lm/W. It is interesting to note that
Philips had its headquarters in Croydon and The GEC (as it was then known) had its
offices in Wembley.

Though these advances were pushing forward barriers in technical development,
colour rendering was at a very poor level. The next development took place in the
United States and the low pressure mercury lamp (commonly known as the
fluorescent tube) was launched; this produced useful quantities of light with efficacies
around 30 lm/W. A great leap forward was made in 1942 with the discovery of the
halophosphate phosphors bringing greater stability in light output and further
increasing lumen output to around 55 lm/W. It is interesting to note that in the United
States they have until recently remained steadfast in their use of the 38mm diameter
lamp; Europe changed with much greater enthusiasm. It is likely that our much higher
energy costs played a major role in this. To this day it is still the norm to see the older
technologies in use in the majority of States.

 In 1973 the first of the fluorescent triphosphor lamps were developed; this produced
an increase of 50% in lumen output with the added advantages of extra life and the
birth of the technology that was to result in the compact fluorescent lamp. It was the
development of this range of lamps which heralded the possibility of making major
reductions in a huge variety of installations. Savings of the magnitude of 50% were
easily achieved and lighting design was given a new light source, significantly smaller
than anything that had been previously available. Commerce and industry fell over
themselves to use this lamp but the British public were not interested in this ugly new
light source. Indeed it must be said that for domestic use they were not cost effective,
as many manufacturers priced them at a level that was never going to encourage their
use. This, linked with virtually no acceptable domestic fittings, could have easily have
sounded their death with the public. It took several campaigns from groups such as
the Energy Saving Trust to get the slightest glimmer of interest. It was only when
some of the big d.i.y. operations started doing some serious deals with the
manufacturers that they started moving with the public.

The range of compact fluorescent lamps extends in many shapes ranging from 5 watt
to 58 watt, though it may well be felt by some that the enormous choice has led to
some confusion. In the main there are 3 main choices to make over and above the
choices necessary with a standard fluorescent type.. (i) Physical size of lamp required
to fit the luminaire. (ii) Whether standard wire wound or electronic ballast’s are to be
used. (iii) Whether retrofitting a version that has the control gear incorporated within
it. We are already experiencing a general downward trend in the pricing of this range
of lamps, and it is a strong possibility that this will copy a similar route that standard
fluorescent lamps did.

The advent of the electronic ballast for use with fluorescent and compact fluorescent
lamps should not be overlooked. There were several advantages in increasing the
frequency of modulation through the lamps. (i) Fluorescent lamps lost their “flicker”,
and this bought with it huge savings in labour as the incidence of headaches and
general debility caused by the 50 Hertz flicker in some of the longer fluorescent lamps
disappeared and with it absenteeism from work was reduced. There is an elimination
of the cause of many cases of epilepsy, as this form of flicker has been instrumental in
bringing out the complaint. In fact there is an instance that a Local Authority has done
a deal with its Facility Mangers that fluorescent tubes replaced in planned
maintenance are being re-cycled in local schools, a practice that in no way can be
condoned. (ii) Reductions in energy used to operate the lamp were made due to ballast
losses being reduced from some 15% down to about 2%. It was also possible that
lower wattage lamps could be manufactured offering further energy reductions. (iii)
Virtually all noise was eliminated from the control gear.

Tungsten Halogen lamps entered the market place about 1960 and made use of the
development of first using chlorine back in the 1880s then in 1933 the use of iodine
was advanced. This type of lighting was initially used mainly for floodlighting and
although the first lamps were 1000 watts, lower- powered versions soon followed and
are widely used around the world today.

The 1960s saw the introduction of the metal halide lamp these were developed
independently both in Europe and the USA with a different make up of elements. In
both cases starting voltages in excess of 1400 volts were required with large and
heavy associated control gear having to be either part of the luminaire or within a
maximum distance of 2 meters from the lamp. The benefits of this lamp were a further
leap forward but there were various control restrictions associated with the lamp. In
the early days that the lamp became commercially available there were many
variations in lamp colour, even with lamps from the same batch. There were many
disappointments with this lamp and it was not until 1994 that this lamp could be used
without fear by means of an electronic ballast. In fact during the first 30 years of the
lamps history lamp reliability had always been a serious bone of contention. The main
or controlling feature of this lamp is current and it was the inability to totally control
the current that caused the wild fluctuations in colour rendering. Linked with this
problem was that of short lamp life. It was generally but incorrectly believed by many
lighting designers that this lamp had a life of around 6000 hours, but certainly in the
early days the many lamps seemed to be failing in the first 3000 hours. This was due
to slight changes in the operating voltage/current that gave the white lamp that
greenish tinge that predicted imminent failure. It may be that a vast number of these
so called failures were in fact the result of unstable voltage/current. Although up to 3
years ago the nominated voltage in the UK was 240 volts + 10 % -6%, it was a
working reality that supply voltage was sometimes in excess of the maximum.

The ceramic metal halide first introduced by Philips in 1994 and was one route by
which consistency of colour was returned. By 1999 both GE and Osram had working
alternatives and an increase in length of life to 9000 hours was being claimed. It could
be suggested that there is insufficient evidence for this to be considered certain yet.
Dimming has only recently been achieved with the metal halide lamp and with it an
increase in life to in excess of 10,000 hours, a consistency of colour and a serious
reduction of start up times; these can be in excess of 6 minutes.

In 1965 the high pressure sodium lamp was released bringing with it a jump in
efficacy to some 90 lm/W and colour rendering that gave the lamp may more uses.
The much warmer colour than metal halide or mercury made it a winner with external
lighting designers. In 1986 the sodium lamp took a step forward with the introduction
of White Sodium lamps, generically to be known as white SON. This was a very
much smaller version and allowed greater flexibility, and found great popularity with
designers in the retail sector

In 1966 the first dichroic extra low voltage lamps were released these lamps in the
main operated at 12 volts and gave luminaire manufacturers several decades in which
to design delivery systems that became “de rigeur”. It has to be said that they opened
up the next generation of lighting but unfortunately over the years became one of the
most misused lamps of this generation. People not only lighted alcoves and specific
features with them but it became the fashion to use them to light entire areas, nay it
has even been used to illuminate the entire groups of shops.

 I give two examples (i) Woolworth decided to develop a range of superstores, a well
known designer was bought in and in his enthusiasm he illuminated the entire shed
with low voltage M50 dichroic lamps. The Sunday Times Newspaper, which had just
launched a colour section did a full article on it. There were over 3000 lamps used in
the installation. It looked the very epitome of all that was chic. Three months later
over 2000 lamps had failed. The shed was closed down and fluorescent battens were
hung throughout the store.

(ii) Another well known group of over 260 shops relied totally on low voltage
lighting as its only source of lighting. After the initial refits air conditioning had to be
installed just to keep the shops at a comfortable working level. The level of
maintenance needed is high and overall it is expensive.
 Low voltage lighting offers the lighting designer probably his most useful tool due to
the precision of control with which this range of lamps allows. The introduction of the
electronic transformer allowed the addition of several new facilities. (i) The virtual
elimination of noise or hum particularly when lamps are dimmed. (ii) The often added
soft start option meant that lamp filaments were not subjected to previous pressures
and resulted in significantly longer life. (iii) Sizes of the electronic transformer were
further reduced allowing even greater flexibility. (iv) Electronic transformers emit
less heat .

Arriving at the present day we have the Induction lamp, Early reports however are
very good. Its exception length of life (some 60,000 hours) will ensure that it will
always be needed for those areas of difficult or dangerous access. It has an output of
some 65 lm/W, and internally works at relatively low temperatures, about 250’C. This
range all work at high frequency in excess of MHz. There are added advantages of no
apparent stroboscopic effects. Its control gear is electronic and if there are short falls
to this lamp it my be within the control box. This is not a low price alternative but the
superiority of performance will certainly justify this lamp type.

Fibre optics seemed at one time that it was going to overtake SELV systems in
popularity. Although a most effective system it was let down by the inability to match
the M50 dichroic lamp which had taken on the mantle of the industry standard. This
system works on the principal of a metal halide lamp within a “light box” and fibre
optic cable transmitting the light to a dichroic type emitter. It is still not possible to
get any more light than one would hope to get from a wide beam 35 watt Dichroic
lamp. It has the huge advantage of being safe, as there is no passage of electricity only
light, this makes for a superb underwater fitting at any depth. The losses in the cable
are insignificant and theoretically allow cables to be run for long distances with no
apparent diminution of light output, it can even go around corners. The only daunting
item is the very high price of the cable. An interesting system of dimming has been
much used in the past, it utilises a spinning disc with sections cut out. The light from
the metal halide lamp passes through this on its way to the cable, and speeding up or
slowing down the speed of revolution can achieve different levels of dimming. There
are nowadays more sophisticated systems of electronic dimming, but they are more
expensive, even if more effective. Several of the clearing banks have used fibre optics
at their banking tills, with the added advantage of negligible heat transfer, hence less
air conditioning yet more cost savings.

It may be that light emitting diode (LED) will take on the universal mantle. This lamp
was first used in traffic signals in 1995. We are all now familiar with them as
information signs on the UK motorway network. With energy savings around 60%
and extremely long life, there again is the added advantage of minimal heating.

The light bulb has come a long way since 1880. Development of new lamps will
arrive in quicker succession; they will become safer more energy efficient and more
adaptable than those of today. New sources will undoubtedly be utilised. Control
systems will be honed to greater degrees . In 20 years time I have no doubt that our
“new” technologies will appear “old hat.”

1) I.F.Davies and E.T.Glenny, Light Sources over 50 years,
The Lighting Journal, volume 39/ no 2 (1974).
2)CIBSE Code for interior Lighting. 1994, updated 1997
3) J. Gordon Cook. Lives to remember, Michael Faraday. 1963

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