Final Report Lot 9: Public street lighting - Amper

6.3.3 WLEDs lamps
Figure 37: Typical WLED
White-light emitting diode WLED lamps (Figure 37) are recently becoming available on the
market with increasing efficacy (e.g. 20 up to 40 lumen/W) and increasing lifetime as a result of
decades of semiconductor research and progress. In street lighting also amber LEDs could be
used that offer a higher efficacy (e.g. 40 lumen/W) but a lower colour rendering. Also
applications where efficient coloured light is required benefit nowadays from LEDs, e.g. traffic
and other signs (applications with a low power density). LEDs also have perfect dimming
capabilities far better than HID lamps which could be beneficial for street lighting where
dimming is required.
WLEDs that are nowadays on the market are Solid State Lighting (SSL) that rely on
semiconductor material. For this SSL technology efficacy and lifetime rapidly decrease with
ambient temperature. SSLs are primarily produced as discrete devices; they are mainly
available in low wattages (typical 1 to 5 Watt) and the main applications on the market
nowadays are small portable devices (e.g. back lighting in cell phones). They are also sold as
multiple LED packages for signalisation applications. In comparison to the same lumen output,
HID lamps are very compact and are available from 20 Watt and above; HID lamps therefore
actually have power levels that are more suited for street lighting.
The SSL dependence on solid state semiconductor material could keep the price relatively high
for these sources. LED semi-conductors are crystals comprised of combinations of typically
two or tree inorganic elements, such as gallium phosphide (GaP), gallium nitride (GaN),
gallium indium nitride (GaInN) or gallium indium phosphide (GaInP). The production of
semiconductor crystals can also require high amounts of energy and can increase the price. For
this reason photovoltaic panels are sometimes evaluated in energy pay-back times in years
(Peeters (2005)). Photovoltaic panels are mainly constructed out of silicon semiconductors. For
the LED semiconductor crystals, energy requirements for production are however unknown
nowadays, due to the high competition and intellectual property concerns. Also the LEDs make
use of rare raw materials (Ga and In) that are used in many other high tech applications (PV
panels, monitors, LCD displays with coatings of indium tin oxide) ('Only united are we strong:
supply problems await areas other than silicon', Photon International, July 2006). The world
annual indium production was estimated(2005) at 455 ton at 650 €/kg with about 6000 ton
global reserves only(US Geological Survey, Mineral Commodity Summaries, January 2006).
The indium price did rise with a factor 8 from 2002 to 2005. The world annual gallium
production was estimated in 2005 at 208 tons at 410 €:kg and the global reserve is more difficult
to estimate. Gallium occurs in very small concentrations in ores of other metals and is produced
as a byproduct (e.g. bauxite). Based on the world resource of bauxite the reserve exceeds 1
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