Final Report Lot 9: Public street lighting - Amper

MH lamps can have a quite short lamp life compared to HPS lamps and can suffer from serious
lumen depreciation over lamp lifetime. Therefore these types of lamps are not commonly used
in street lighting but in sports lighting and floodlighting. Also the lamp colour is not stable over
lamp lifetime (more greenish) because metals start to react with the arc wall and diffuse from
the arc tube to the outer envelope. New developments for these quartz metal halide lamps are
still ongoing (see also below).
The first commercial available High Pressure Sodium (HPS) lamp appeared around 1965 on the
market. An important preliminary step in the development of this lamp took place between
1955 and 1957 when translucent, gas-tight polycrystalline alumina (PCA) was discovered; this
PCA material is a ceramic material composed of 99.9 % sintered Al2O3. This material was
required to withstand the highly reactive sodium at high temperature and high pressure.
Processing of this ceramic material is far more complicated compared to fused silica glass. The
production technology is therefore less proliferated compared to HPM or quartz MH lamps.
These lamps have, compared to other HID lamps: a high lamp efficacy (see Table 103),
acceptable colour rendition, long lamp life and high lamp lumen maintenance. Therefore they
are often used in street lighting.
About 1982 a substantial increase in lumen output was realized by enhancing the
xenon-pressure in the arc tube and so the ‘plus’ or ‘super’ lamps came on the market. The
cheeper standard lamps with lower efficacy stayed on the market. (This explains the lower
efficacy for some cases in 4.3.1.4, Table 62, Table 64 and Table 67.) Lamps with longer
lifetime (4 years) were introduced from 1996 on.
Other HPS types exist and are often a design compromise between colour rendering, lamp
efficacy and long life.
New developments are still ongoing.
In the mid 90s the first Ceramic Metal Halide lamps were commercialised. The use of a PCA
ceramic arc tube has greatly improved colour stability because the reaction of metal halides
with the arc tube and the diffusion of certain metal halides trough the arc tube could be reduced.
Another option to improve the colour stability of classic quartz MH lamps is to use a shroud or
a second quartz shelve around the discharge tube. These solutions came on the market recently.
The new MH lamps are actually often used for commercial indoor lighting as an
energy-efficient replacement for halogen (incandescent) lamps. Since a few years, there also
exists a version of this lamp type for outdoor (public) lighting, especially designed to replace an
HPS lamp in the same luminaire and working on the same ballast. All CMH lamps still have a
reduced lumen maintenance and lamp life compared to HPS lamps. New CMH lamp
developments are ongoing.
The production technology for quality HPS and MH lamps is sophisticated and new
developments can be expected in the near future. This can also be deducted from published
European patents related to HID lamps: 6 in 2006 (until October), 3 in 2005 and 3 in 2004.
Please note that these patents did not lead to a manufacturer monopoly probably due to a
cross-licensing policy in order to satisfy the requirement for a second source supplier by public
bodies.
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