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Streetlights are not only a vital necessity for security and safety in a community but also provide a sense of well-being and progress. As streetlights consume so much energy that eats much of the budget of the community, there is a growing demand for the usage of energy-efficient lamps and to harness solar energy to power the streetlights. Energy efficiency however not only has to consider illumination brightness and power consumption but also optical safety appropriate for motorists roadways) and pedestrians (parks).

Streetlights are a vital necessities for security and safety in a community as well as a means to provide a sense of well-being and progress. As streetlights consume so much energy that consume a large portion of the budget of the community, there is a growing demand for the usage of energy-efficient lamps that harness solar energy to power themselves. Energy efficiency, illumination, power consumption are all important factors to consider when installing a system that meets optical safety standards for motorists (on roadways) and pedestrians (on walkways and in parks).

High-Pressure Gas Discharge (HPGD) lamps, utilizing mixed gases as their medium, are now economically feasible and can provide the required brightness for operation and safety. The lumen efficiency of the new HPGD lamp can reach an amazing 97.43 lumens per watt (Lm/W) with high color rendition index (CRI). (Tests are by the Taiwan Research and Testing Center, the most authoritative non-profit organization for streetlight testing and certification in Taiwan.).

Considering the vaunted long lifespan and low power consumption of LED lamps for various lighting applications, much research is being done to use LED lamps for streetlights. However, similar to the incandescent lamp, energy conversion of the LED lamp is 15% light and 85% heat. For high light intensities required for street lighting, heat dissipation poses a problem which may affect the LED lifespan. With a luminous efficiency of less than 60 Lm/W, present LED lamps cannot adequately illuminate a wide road surface from a tall post..

These are all excellent alternatives to mercury and sodium lamps, which are still widely used for street lamps, which a have a low CRI and luminous efficiencies, use more energy to run, and pose an environmental threat during their disposal.

COMPARISON CHART

Parameters HPGD LED Mercury Sodium Metal Hallide
Lumens/Watt Lm/W 90~97 37~60 30~50 40~65 50~60
K(Color Temperature) 3, 000 and 4, 200 3, 200~3, 400 90~97 2, 000~ 2, 500 3, 700~ 4, 200
Ra(Color Rendition Index) 80~90 90~97 40 20 65~70
LED Bulb 15, 000~20, 000 50, 000(?)heat management 90~97 20, 000 10~15, 000

As shown in the comparison chart, the HPGD lamp has a very high luminous efficiency of 97.43 Lm/W, high CRI, long lifespan, low heat generation, and is environment friendly. Aside from its outstanding features, the HPGD lamp consumes much less power. Compared to sodium/mercury lamps, some models can achieve up to 70% energy consumption MASCHINEN & TECHNIK.INC.reduction (e.g. a 35W HPGD can replace a 150W mercury or a 150W HPGD for 450W mercury). Presently, it costs comparably with sodium/mercury lamps but is expected to become cheaper in a few years due to economy of scale.

Specifications of Various Models
(High Pressure Gas Discharge Lamps)

Parameters MS-20A 20W MS-35A 35W MS-70A 70W MS-150A 150W
Lumens Efficiency 85 lm/W 97 lm/W 93 lm/W 97 lm/W
Color Temperature(K) 3, 000K 3, 000K 4, 200K 3, 000K
Color Rendition Index(Ra) 83Ra 86Ra 92Ra 85Ra
Total Luminous FLux(Lm) 1, 700 lm 3, 395 lm 6, 975 lm 14, 550 lm
Total System Flux with Reflector 6, 800 lm 13, 580 lm 27, 900 lm 58, 200 lm
Economic Life Span 12, 800 lm 12, 000hr 15, 000hr 12, 000hr
Lux 30 39 32 35
Height 3.5m 6m 8m 12m
Input Power DC 12V/AC220 DC 12V/AC220 AC220 AC220

For further power cost savings, the HPGD streetlights can be provided with solar power supply with commercial power as standby in case of prolonged sunless days. One controller with solar array and battery bank can handle up to 18 streetlights. Standards for street lighting, particularly for roadways, should be carefully studied and imposed. Poor roadway lighting such as usage of fluorescent lamps with low-frequency ballasts poses optical and safety hazards. Some countries are changing yellow (to white) lighting for tunnels to minimize the abrupt change in light intensity from bright sunlight in going into and out of a tunnel.