106 TECHNOLOGY / STREET & AMENITY LIGHTING
RETROFIT SOLUTION PUTS LEDS IN HISTORICAL LANTERNS
In Regensburg, OSRAM Opto Semiconductors and Siemens have demonstrated that energy-saving LEDs
can provide authentic period-style lighting for a historical centre. The companies have developed a retrofit
solution which meets the requirements of a modern lighting system while preserving the atmosphere of a
world heritage site. The light sources being used are Golden Dragon Plus LEDs. Discreetly installed in the
luminaires prescribed by the Office for the Preservation of Historical Monuments, they target the precise spot
they are intended to illuminate, thus avoiding light pollution.
Regensburg has narrow alleys and many winding streets in a multitude of different lengths and widths. This
is why the intricately structured town needs luminaires which enhance its historical ambience. To ensure
consistently attractive lighting, the different colours of the buildings must be taken into account and the
kind of use, colour temperature and colour rendering index adjusted accordingly. The street lights must not
be dazzling in residential areas, for instance, nor should they spoil the romantic atmosphere of candle-lit
restaurants.
The light is fully directed to the exact place it is intended to illuminate: to the street, or also to the façade,
when it is used to highlight architectural features. And the desired level of illuminance and the light
distribution can be precisely adjusted by adapting the number, the optical devices and the dimming of the
LEDs. The LEDs have a colour temperature of 3500K and a colour rendering index of 80. A common optical
device combines the light from the individual LEDs into a single beam and accurately directs it towards the
desired target. As part of this project, the alleyways known as ‘Blaue Liliengasse’ and ‘Untere Bachgasse’
were fitted with new luminaires and some of the LEDs were selectively directed towards the façade. This
ensures that the lighting can be precisely tailored to the architecture.
The prototype luminaire permits the replacement of ordinary 90W mercury vapour lamps with LEDs. The
luminaire design is based on a cylinder. Manufactured by the Regensburg branch of Siemens, the prototype
can be fitted with different numbers of LEDs on either side as required to produce the desired lighting effect.
www.osram-os.com
a bulk replacement programme, how do begin to dominate the street lighting scene performance for LED street lighting and will
they dispose of the old lighting components? over the next decade but in my opinion its start to offer real alternatives to traditional
Many of them contain PCBs that all pull on adoption will be much slower than most LED street lighting fixtures.
scarce resources. companies predict mainly because: Bridgelux, a leader in LED arrays are about
• Outdated luminaires: Outdated • LED technology is relatively new and still to launch the BXRA-C4500 a compact LED
luminaires fitted with old gear, with no real unproven in the application. array that is ideal for LED street lighting
optical control and outdated light sources • Street lighting engineers will wait until applications having 4500 lumens output
are another cost issue. Out of a lamp there are proven advantages in real-life when operated at a case temperature of
population of 28 thousand in the Salford applications and not on datasheets. 60C. The new device has a nominal colour
area, 43% are Low Pressure Sodium with • There are significant financial constraints temperature of 5600K and a typical colour
many fitted with old control gear resulting on Local Authority budgets due to the rendering index of 65 all within an array of
in high energy usage, low illumination and economic recession with many predicting 50.3mm x 45.3mm.
no colour recognition. annual cuts of between 10 and 20% from the The latest Cree XP-G LEDs are also an
• Lack of investment: A few Local next budget. excellent technology for streetlighting
Authorities have cash to invest in new • Local Authorities have higher priorities applications as they use larger LED die
infrastructure, or turn to PFI projects to on their agenda such as education and enabling higher lumen outputs whilst
fund capital expenditure. However many social services which will pressurise residual maintaining LED efficacy. The latest XP-G
Local Authorities are under-funded with budgets notionally set aside for lighting. LEDs are capable of delivering 345 lumens
resources being diverted to frontline • Traditional light sources are very efficient at 1A and still achieving 105 lumens per
services such as education and social care. for the application and therefore there is watt efficiency.This has enabled Liaoyuan
These pressures usually mean that street less pressure to change the technology until Lighting, a Chinese lighting manufacturer,
lighting investment is vulnerable which LEDs offer a significant advantage. to create a street lamp system efficacy of
leads to structurally unsound stock. This is a • LED street light capital expenditure is two 98.3 lm/W in a 150-watt product.
national as well as a local problem. to three times more expensive than current There will also be a range of new high
• Stock condition and inventories: Local technology and the return on investment is power LED driver technologies specifically
Authorities should inspect their lighting still too long to make investment by Local for street lighting applications launched
columns to TR22 and be able to have a Authorities attractive. during 2010 that significantly improve
detailed age and condition profile. If not it • Although the lower power street lights lifetime characteristics and provide precise
will be very difficult for Local Authorities could be replaced by LED equivalents today power control, remote placement of drivers
to bid for funding to renew any ageing the majority of the traditional street lamps away from the LED arrays (resulting in
stock. Its vitally important therefore that will be more difficult to replace as LED easier maintenance access and low voltages
Local Authorities find the resources to keep technology has still to mature for higher up the lighting column) and intelligent
their inventories up to date not only for power applications. communication protocols. One such
stock condition but producing priority lists Having stated this there is a clear LED company is IST who are launching the iDrive
for schemes and for energy monitoring. advantage which is the rate of performance DSP range of drivers to improve the lifetime
Without this information Local Authorities increase for LED technologies is significantly of LED drivers by employing advanced
can’t carry out what if scenarios to higher than traditional lamps and LED digital signal processing to monitor voltage,
determine options for reducing energy and costs are decreasing at an equivalently current and total LED array power at up to
maintenance costs. phenomenal rate. Therefore, it is not a 100,000 times per second.
question of if LEDs will replace traditional
LED TECHNOLOGIES THAT WILL MAKE LED light sources, but when. CURRENT STUDIES OF LED STREET
STREET LIGHTS MORE ACCESSIBLE Some of the latest LED technologies LIGHTING
There is no doubt that LED technology will being introduced offer significant leaps in There have been several high profile
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