Light-emitting diodes in street and roadway lighting – a case study involving mesopic effects

Abstract

The paper considers the justification for the application of light-emitting diode (LED) technology to urban lighting. The results suggest that LEDs are convenient for architectural lighting and deserve to be considered for use in ambient lighting. The recently developed Commission Internationale de l'Eclairage (CIE) mesopic system enabled the inclusion of mesopic effects into a comprehensive technoeconomic analysis, which dealt with efficiency, maintenance and financial aspects of the use of LEDs in street and roadway lighting. It is concluded that the average energy savings when using LED instead of high-pressure sodium (HPS) luminaires amount to 19-26% for single-sided, staggered and opposite layouts, although they are frequently negligible if mesopic effects are not included. The total costs of the LED lighting solutions, even including mesopic effects, are 1.36 to 6.44 times higher than those of the comparable HPS lighting solutions. Therefore, LEDs are questionable for street and roadway lighting.

Comparison of electronic and conventional ballasts used in roadway lighting

“…This is because HPS lamps are characterised by high luminous efficacy (up to 150 lm/W), long life (up to 20 000 hours) and low cost. 1,2 As gas-discharge light sources, HPS lamps require certain electric and/or electronic devices to be installed into the lamp electrical circuit. Such devices are known as control gear (ballast), which fulfils a lot of functions, the following ones being most important: -limits and stabilises the lamp current, -provides an ignition voltage for lamp starting, -increases power factor and -keeps the lamp voltage, current and power within the specified values independent of the variations of the mains supply voltage.…”

Digital control of low-frequency, small-wattage, high-intensity discharge lamps

“…Low-frequency square wave (LFSW) ballasts are widely used to drive HID lamps, because acoustic resonances in highfrequency electronic ballasts will likely cause device instability. [3][4][5][6][7] Typically, an analogue circuit is selected to control the traditional LFSW electronic driving circuit. The analogue control method needs to detect the lamp voltage and lamp current and, subsequently, analogue signal processing is conducted by following a lamp power control scheme.…”

Argentinean Experience in Highways Led Lighting

“…Table 2. Corrected photopic luminance, considering mesopic vision (reference S/P 0,65 -SAP-) -taken from (Kostic, 2013) Photopic Table 2 was built using the sodium spectrum as a reference, that is way for S/P = 0.65 the actual luminance (photopic luminance) is the same that the mesopic luminance shown in the table (shaded row in table 2). In order to give an example of the effect of the mesopic vision in a highway, we can consider an installation with cold white led (S/P 1.85).…”

“…Kostic (Kostic, 2013) quantifies the perceptive improvement by considering the eye sensitivity increase in mesopic vision. Table 2, taken from his publication, allows obtaining the equivalent mesopic luminance in a simple way for a certain photopic luminance (measurable), in function of the spectrum relationship scotopic-photopic of the source (relationship S/P).…”