Light Emitting Diode Street Lamp Research Articles

Shedding light on the effects of LED streetlamps on trees in urban areas: Friends or foes?

Streetlamp illumination disturbs the natural physiological processes and circadian rhythms of living organisms, including photosynthesizing “citizens”. The light-emitting diode (LED) technology has replaced high-pressure sodium lamps. Therefore, the effects of LED streetlamps on urban trees need to be elucidated as these new lamps have a different light spectrum (with a peak in the blue and red regions of the spectrum, i.e., highly efficient wavebands for photosynthesis) compared to older technologies. To address the above-mentioned issue, two widely utilised tree species in the urban environment, including Platanus × acerifolia (P) and Tilia platyphyllos (T), were grown with or without the effect of LED streetlamps using two realistic illumination intensities (300 and 700 μmol m−2 s−1). Gas exchanges and biochemical features (starch, soluble sugar, and chlorophyll content) of illuminated vs non-illuminated trees were compared during the whole vegetative season. Our results showed that both tree species were strongly influenced by LED streetlamps at physiological and biochemical levels. Specifically, the mature leaves of P and T streetlamp-illuminated trees had a lower CO2 assimilation rate at dawn and had higher chlorophyll content, with lower starch content than controls. Our results showed that the differences between the effects of the two selected light intensities on the physiochemical attributes of P and T trees were not statistically significant, suggesting the absence of a dose-dependent effect. The most significant difference between T and P trees concerning the LED-triggered species-specific effect was that the delay in winter dormancy occurred only in P individuals. This study provided insights into the extent of LED streetlamp disturbance on trees. Our findings might raise awareness of the necessity to provide less impacting solutions to improve the wellness of trees in the urban environment.

Design and Implementation of Ferroresonant Transformer for LED Driver Systems

This paper presents the design and implementation of the 60-Hz ferroresonant transformer (FRT) for the light emitting diode (LED) street lamp to achieve high-frequency (HF) noise attenuation and ac-line voltage clamping. The HF transformer (HFT) used in the LED driver system for the outdoor LED street lamps cannot effectively suppress the surge current to avoid damage to the LED street lamp. However, instead of the HFT, the low-frequency transformer (LFT) can be applied to protect the LED street lamps from the surge current. The LFT has a higher turns number, which provides larger leakage inductances and parasitic capacitances that effectively suppress and shunt the surge current. With the magnetic shunt, a 60-Hz FRT is proposed to effectively regulate the ac-line voltage to not overstress the LED street lamp systems as compared with the conventional LFT. When the ac-line voltage is higher than the rated voltage, the additional magnetic flux generated from the primary-side winding flows through the magnetic shunt but not the secondary-side winding. The rated output voltage of the secondary side can be sustained to achieve ac-line voltage clamping. A prototype of the LED street lamp with a 60-Hz FRT has been designed and implemented to verify the feasibility of the HF noise attenuation and ac-line voltage clamping.

Cooling of High-Power LED Lamp Using a Commercial Paraffin Wax

Commercial paraffin wax used by Bolsius Nederland B.V. for manufacturing various kinds of candles was applied as a phase-change material (PCM) for cooling a 28 W high-power light emitting diode (LED) panel during its operation. The main problem arising during operation of an LED is thermal management. According to the manufacturer’s datasheet specifications (BioSolution Ltd. www.biosolution.pl), the operating temperature range for the LED street lamp UL28W is (-30~{^{circ }}hbox {C}) to (+40~{^{circ }}hbox {C}). The object of the present study was an LED panel containing 28 pieces of high-power 1W LEDs connected in series (4 LEDs in each of the 7 rows) mounted on an aluminum plate of dimensions 80 mm by 135 mm. The tested aluminum plate was placed in a block made of aluminum with a hollow compartment containing Bolsius paraffin wax of density 914~hbox {kg}cdot hbox {m}^{-3} at room temperature. Temperatures were recorded using K-type thermocouples at selected locations of the tested LED panel for several values of the power supplied to it, while utilizing PCM and without it. As the manufacturer of Bolsius wax candles does not provide any data on the thermal properties of the material used, it was necessary to carry out micro-calorimetric research. Thermophysical properties of the paraffin wax such as the apparent specific heat, enthalpy of phase transition and temperature of phase change transition during heating and cooling were determined using the Netzsch DSC 214 Polyma. The Netzsch TG 209F3 Tarsus was used for TG/DTG measurements. DSC investigations revealed the following thermal transitions taking place during the first heating: solid–solid transition (onset 30.4~{^{circ }}hbox {C}, peak at 40.9~{^{circ }}hbox {C}), solid–liquid transition (onset 47.7~{^{circ }}hbox {C}, peak at 54.9~{^{circ }}hbox {C}, end at 58.3~{^{circ }}hbox {C}), latent heat of energy storage 201~hbox {J}cdot hbox {g}^{-1}, apparent specific heat corresponding to peak at 41.5~{^{circ }}hbox {C}(5.498~hbox {J}cdot hbox {g}^{-1}cdot hbox {K}^{-1}). DTG investigations revealed that the decomposition of paraffin wax is a two-step process. At 283~{^{circ }}hbox {C} there was observed a slightly slower decomposition (9.43,%cdot hbox {min}^{-1}) than that at 323~{^{circ }}hbox {C} (12.5,%cdot hbox {min}^{-1}). The experimental results obtained upon cooling the high-power LED lamp during its operation can be applied to verify results of numerical modeling of the heat transfer problems with phase-change transitions. An attempt at modeling such a problem based on 1D fixed grid with variable time step approach was undertaken in this work.

Analysis on energy efficiency and optimality of LED and photovoltaic based street lighting system

This study evaluates the optimality and energy efficiency of Light Emitting Diode (LED) and Photovoltaic based street lighting systems as a part of energy conservation. This evaluation is based on the detailed review carried out through a country wide street lamp survey. Since LEDs are becoming increasingly competitive due to their rapidly increasing efficiencies and decreasing cost, this research assessed the LED fixtures which have the capability of achieving 50% to 70% energy saving potential compared to the existing established technologies based street lamps available in the country. As a case study, illumination levels were examined at two neighboring traffic junctions in the Capital City, from Bambalapitiya junction to Kollupitiya junction. Two kinds of measurements were taken and average luminance levels were analysed for all measured points in the traffic lanes. It was found that same lighting performance could be achieved by replacing 250W HPS (High Pressure Sodium) by 150W HPS and further it was verified the same results while having 62% energy saving by replacing 250WHPS lamps with 111W LED through a simulation with Lighting Reality TM software. This change would easily meet the minimum recommended level of 7.5 Lux and average luminance of 0.5 cd/m 2 as per British Standards. Even though solar powered street lighting systems need high capital outlay, it will be one of the most appropriate energy solutions for a country like Sri Lanka. Incentive program development by the government may further encourage LED street lamp and solar powered system development adoptions. This study also recommends that any such incentive program should include performance standards that consider warranty, efficacy and other important criteria as the next steps. ENGINEER, Vol. 48, No.01, pp. 11-20, 2015

Design of Polygon Prism Optical Lens for LED Street Lamps

High-power light emitting diode (LED) develops greatly owing to its high energy efficiency, high color rendering and long life. However, it is important to design a secondary optical lens for the LED lamps to obtain a good output efficiency and light distribution pattern. The purpose of the secondary optical design for light emitting diode (LED) illumination is to rearrange the luminous flux output of LED and then achieve the desired luminous intensity distribution. In this paper, a polygon prism lens for street lamps was designed and the desired illumination was achieved. The design procedure of the polygon prism lens is presented. The simulation of the street lamps is implemented using Tracepro 7.0. The results show that the polygon prism lens can distribute the luminous flux accurately and reasonably. The luminous flux can be saved as much as possible and a rectangular distribution of luminous flux is attained.

Temperature estimation of high-power light emitting diode street lamp by a multi-chip analytical solution

Light emitting diodes (LEDs) are now widely used in many fields including traffic lights, vehicle backlights and liquid crystal display (LCD) displays because of their long life, good illumination efficiency and low energy consumption. At present, LEDs are increasingly replacing the traditional lighting and are being used in general illumination such as the street lamp. For the high-power LED street lamps, good light extraction is the most important thing, but low junction temperature of the LED modules is also critical for achieving a long lifetime and a high optical efficiency. Actually, there have been many reports about early failures of street lamps, called dead lamps that have been regarded as a barrier in the public and administration acceptance of LED street lamps. Therefore temperature estimation is always a crucial issue for LED product development. A multi-chip spreading thermal resistance model was applied to estimate the temperature distribution of LED street lamp. The experiment was first done to obtain temperatures of several locations in a prototype LED street lamp. Then the multi-chip spreading resistance model was established to calculate the full temperature distribution. Comparison between the model calculation and experimental measurement showed a good agreement, which demonstrates that the present model can be used in engineering design to estimate the temperature distribution of high-power LED street lamps.

Optical analysis of an 80-W light-emitting-diode street lamp

Optical analysis is critical to the evaluation of a light-emitting diode (LED) street lamp, especially when the lamp is still in its early stage of development and applications and when optimization is needed for making use of unique characteristics of LEDs. In this study, optical analysis of an 80-W LED street lamp was conducted. Experimental research on such a lamp was first undertaken. The results demonstrated that the average illumination was about 8.25 lx and the total uniformity was 0.364 for a 20-m-long and 10-m-wide test area at a height of 8 m, which is acceptable for the current standard for a submain road. Numerical simulation was also conducted; the feasibility of the numerical model was proven by comparison of the simulations with the experimental data, which will be used for future optimization study and other novel designs of the optical system of street lamps. Through the simulations and the corresponding analysis, it was found that the tested 80-W LED street lamp had reasonable performance in average illumination, but multiple shadows existed, which would need to be removed in future designs. Improvements are suggested to reduce the number of optical elements, to reduce the lamp's volume, and to enhance the illumination performance. Two design methods for LED street lamps are summarized, based on the optical analysis.

Thermal analysis of an 80 W light-emitting diode street lamp

Light-emitting diode (LED) street lamps rely heavily on successful thermal management, which strongly affects the optical extraction and the reliability/durability of the LED lamp. A thermal analysis of an 80 W LED street lamp was done. Sixteen thermocouples were used to measure the temperatures at 16 different positions of the street lamp. The results demonstrated that the temperature of the frame and the heat sink of the 80 W LED street lamp remained stable at about 42degC after several hours of lighting at a room temperature of 11degC, and the bulk material resistance of the heat sink could be neglected. Numerical simulation was also used to analyse the temperature distribution of the lamp. The reliability of the numerical model was proven by a comparison of simulation results with the experimental data. Through simulations and the corresponding analyses it was found that the tested 80 W LED street lamp would have poor reliability at an environment temperature of 45degC.