LED street lighting has an increasingly widespread usage. There is a reason for that and it lies in the state-of-the-art technology that it uses and the advantages of this technology over alternative types of lighting.
Street lighting is a key element of modern urban and rural infrastructure. Historically, there is evidence of systemic street lighting dating back to the 4th century BC in some cities of Ancient Greece. The modern concept of illuminating cities in order to reduce crime and improve people’s movement/transportation at night emerged in Western Europe in the 16th century. During the 17th century, a number of cities already had well-developed candle lantern street lighting systems. The evolution of street lighting then went through the use of various liquid fuels, the most widely used of which was gas. This was the case until electricity was introduced.
Let there be light
Incandescent light bulbs dominated the street lighting market for many years. However, they were gradually replaced by the much more efficient HID (high-intensity discharge) lamps that are still used nowadays. There are three main types of HID lamps: mercury-vapor, metal-halide and sodium-vapor lamps.
Mercury-vapor lamps emit white light, have a relatively low luminous efficacy of up to 70 lm/W, and a lifetime of approximately 16,000 hours. In the 1990’s these lamps were widely used in Bulgaria’s street lighting. Due to their low efficiency they were replaced by the two other types of gas-discharge lamps and eventually banned from use in the EU’s public sector with a directive in 2006.
Metal-halide lamps have a similar design, but are more efficient: up to 90 lm/W. However, their lifetime is shorter: approximately 10,000 hours. These lamps emit white light and their characteristic trait is excellent color rendition.
Sodium-vapor lamps offer the best performance among HID lamps. They have an efficiency of approximately 140 lm/W and a lifetime of up to 24,000 hours, which is excellent. However, they have a major drawback – their light is deep yellow to orange, which is not the best option when it comes to street lighting.
Fixtures with fluorescent lamps are also used for street and public area lighting. However, the limited luminous flux of these lamps prevents them from being universally used, despite their high energy efficiency.
After the amazing success of LED lamps in home lighting over the last few years, it’s time to look at public area lighting, street lights in particular. The excellent efficiency of diode lamps, the opportunity for different types of light, the long service life, and last but not least – compact dimensions, are serious arguments in the fight for superiority with HID lamps. Modern LED lighting fixtures designed for street or public area lighting have excellent features, an attractive design, a high energy efficiency and low weight. Compared to their main rival in the competition for the “Best street lighting” prize, i.e. sodium-vapor lamps, LED lights have some serious advantages:
- LED lamps do not release heat and do not heat up, which makes them much more fire-resistant than high-intensity discharge lamps.
- It is much easier to direct the light of LED fixtures, thus reducing scattering and light pollution.
- Light from LED fixtures may vary in the range from warm white to cold white while the light from sodium-vapor lamps is always yellow.
- Diode lamps light up at a full brightness instantly while all HID lamps need some time to heat up once switched on.
- Low energy consumption allows LED fixtures to be combined with compact solar panels. Thus, they become even more cost- and energy-efficient street lighting.