LED Street Research Articles

Impact of Dimming LED Street Luminaires on Power Quality

Impact of Dimming LED Street Luminaires on Power Quality

A Novel Strategy For Transformation Of Conventional Road Lighting To Smart Road Lighting

In recent years, smart road lighting (SRL) design and application researches has been increasing rapidly. However, SRL applications remain pilotproject and cannot become widespread sufficiently. Main reason for this is that, although the cost of production of LED luminaires is reduced, when existing road lighting systems are transformed to LED road lighting, existing electrical installations and lighting poles cannot be used. Increased investment costs due to electrical installation and poles renovation, decrease interest in SRL transformation. In this study, an innovative solution is developed to decrease the costs of the SRL. First, a new LED luminaire is designed, which can work without changing the installations and poles of the existing projects. Then a test road is created using DIALux software, and the newly designed lighting installation is compared with completely redesigned one and conventional road lighting. Thus, contributions are provided for spreading of the SRL transformation, using low cost SRL approach.

Effects of traffic-regulated street lighting on nocturnal insect abundance and bat activity

New technological developments modulate the light levels of LED street luminaires according to traffic volumes: light levels are increased given traffic and reduced in its absence. Such dimming of street lights reduces the level of artificial light at night (ALAN) and may thus contribute to mitigate light pollution. To quantify the impact of traffic-driven dimming of street lights on nocturnal insect abundance and bat activity in comparison to full light (i.e., dimming functions of luminaires switched off), we mounted 20 insect flight-interception traps and ten batloggers on street light poles along two dimmable street light sections. Insect abundance and bat activity were measured alternately with one week of full street lighting followed by a week with light levels modulated by traffic volumes. In total, 16 dimmed and 16 full-light days were investigated. Overall, traffic-driven dimming reduced light levels by 35%. Weather conditions (warm, dry nights) were the main drivers of insect abundance and bat activity, but traffic-driven dimming resulted in lower numbers of insects caught and reduced bat activity. Among insect groups, Heteroptera benefited most from dimming. For bats, urban exploiters (Pipistrellus spp.) benefited from increased availability of prey at brightly lit street lights, while less frequent species (Myotis spp.) did not benefit from street lighting. We conclude that street light dimming technology may contribute to mitigate negative effects of ALAN on nocturnal organisms, although the measure may not be efficient enough to support light-sensitive and threatened species.

The Feasibility and Environmental Impact of Sustainable Public Transportation: A PV Supplied Electric Bus Network

Limited fuel resources and the huge negative impact on the environment from using fossil fuels have led to an urgency to utilize the most energy efficient solutions for public transportation. Environmentally sustainable solutions can deliver the same benefits of traditional systems, but without the negative impacts. The Bus Rapid Transit Project of Amman (Amman BRT) is used as a case study. Proposed measures include using electric buses instead of diesel ones, and installing elevated photovoltaic systems above buses parking and routes, in addition to using LED street lighting. The feasibility study of applying the proposed measures on the Amman BRT project showed that only 7.1 years is needed to payback the incremental investment throughout this transformation. Capital expenditure (CAPEX) is higher than the baseline buses, while operational expenditure (OPEX) is much lower, resulting in a 32% lower total cost of ownership (TCO). In addition, greenhouse gas (GHG) emissions are reduced by 27,203.68 metric ton of CO2 per year and 408,055.26 metric tons for the 15-year lifetime of the project.

Susceptibility of LED street lamps to voltage dips

There is an ongoing transition from high-pressure sodium lamps to LED street lamps that offer higher efficiency, cost saving and better photometric performance. This transition could lead to unintended consequences such as light flicker and extinguishing in street lighting applications when they are exposed to voltage dips. The goal of this paper is to analyse the light intensity variation of various street lamps when they are exposed to voltage dips. Several performance metrics for quantifying immunity of lamps have been proposed. Values for these metrics are obtained by applying artificial voltage dips to lamps. For voltage dips with residual voltage above 38%, lamps are immune in terms of a short-term light flicker metric. For residual voltage above 25%, light intensity reduces but without extinguishing. Compared to an incandescent lamp and high-pressure sodium lamp, LED street lamps exhibit longer zero-light intensity duration. Most of the studied LED street lamps exhibit uncoordinated light intensity drops, i.e. longer or shifted, with respect to the applied voltage dip. Individual characteristics of LED street lamps require testing before installation to prevent unexpected consequences. Recommendations are given for standardisation committees to implement an assessment method for lighting equipment.

Algorithms of Energy Efficient Control of LED Street Lighting Installations

A comparative analysis of existing street lighting installation (SLI) control algorithms has shown that modern implementation of energy-efficient control algorithms doesn’t take in account the requirements of regulatory documents to ensure the normative level of illumination of the road surface. Existing control algorithms based on deterministic methods, which does not provide a high level of energy efficiency in changing environmental conditions (weather, natural light) and uncertain initial data (traffic intensity). So, the work proposes to use the mathematical apparatus of artificial neural networks for the implementation of control algorithms with independent or united accounting of two input variables: natural luminosity and forecast of traffic intensity. The developed algorithms for energy-efficient control of the SLI are tested on a simulation model of a SLI control system created in the MATLAB software. The results of modeling are following: the implementation of the control algorithm allows to reduce energy consumption of the SLI by 35,9 % due to dimming of the light flux in hours with low traffic intensity, which confirms the energy-efficient functioning of the SLI, controlled by developed algorithm.

Analysis and implementation of soft‐switched bidirectional buck‐boost DC‐DC converter for solar PV‐fed LED street lighting systems

Analysis and implementation of soft‐switched bidirectional buck‐boost DC‐DC converter for solar PV‐fed LED street lighting systems

A Study on the Crime Prevention Effect of Improved Street Lighting

연구의 목적은 셉테드에 대한 관심의 증가로 향후 많은 예산의 투입이 예상되므로, 범죄예방이라는 근본적인 목표의 효과적인 달성을 위해 전략별 효과요인에 대한 검증을 순차적으로 입증함으로써 투입전략의 기능과 효과를 체계화하여 효율적인 활용방안을 모색하고자 하는 것이다. 연구 방법은 셉테드의 기본원리와 전략에 관한 이론적 문헌조사를 진행하였다. 연구대상지역인 서울시 K구의 2014년부터 2017년까지의 조명개선 목록을 자치단체의 협조로 수집하였으며, 관할경찰서 관내 2013년부터 2015년 까지 발생한 5대 범죄의 유형, 발생일시, 발생장소 등 개인정보를 제외한 분석항목을 중심으로 수집하였다. 분석방법은 조명개선사업이 추진된 구역과 주변의 조명개선사업이 추진되지 않은 구역의 위치, 규모 등을 고려하여 총 7개 의 구역을 분석대상지역으로 선정한 후 GIS 프로그램과 Odds Ratio 분석방법 을 활용하여 사업 전ㆍ후 5대 범죄 전체 발생건수의 변화와 범죄유형별 발생 건수의 변화를 차례로 분석하여, 실험구역과 통제구역 간의 발생건수 변화를 비교하였다. 연구결과는 첫째, 개선된 조명이 5대 범죄를 종합적으로 예방하는데 효과가 있었다. 둘째, 조명개선 사업은 절도범죄에 대해서는 매우 효과가 큰 것으로 확인되었고, 폭력은 미미하지만 효과를 인정할 수 있으나, 성폭력은 구역 별 발생건수가 적어 예방효과에 대한 판단을 유보하였다. 셋째, 구역별로는 총 7개의 구역 중 5개 구역에서 범죄예방효과가 있음을 확인하였다. 특히 GIS를 이용한 범죄위치분석에서 사업이전과 사업이후의 범죄발생위치 분포가 대상구역의 중심지에서 가장자리 또는 통제지역과의 경계부로 이동되는 것을 확인할 수 있었다.In consideration of increasing interests in CPTED and enormous resources expected to invest for such strategies, this study mainly analyzed the effectiveness of one type of crime prevention strategies, improved street LED lighting. In particular, this study examined more cost-effective strategies to achieve the fundamental goal of crime prevention and to find ways to utilize them efficiently. Methodologically, this study reviewed a volume of literature on the basic principles and strategies of the CPTED. Then, this study collected the list of improved lighting between 2014 to 2017 and crime data (homicide, robbery, sexual assault, theft, violent assault) between 2013 and 2015 in K District, Seoul. These datasets include locations, types, and date of each lighting and crime. Based on this information, this study obtained 7 target areas where the improved lighting was geographically concentrated and 7 control areas in the vicinity of target areas with similar sizes. Using the QGIS program and the odds ratio analysis method, this study examined the changes in the total number of crimes before and after the lighting improvement within the target and control area. This study found that improved lighting, in general, was effective in preventing the five major crimes altogether. Second, this study found differing effects of the improved lighting by different crime type and geographical area. For example, improved lighting was more effective for theft than violent assault. Also, the effect of improved lighting was found only within 5 target areas out of 7 areas. In more detail, this study found that distribution of crime became more concentrated in the edge or boundary of the target area, which indicates displacement of crime influenced by the improved lighting.

Design and Implementation of a Solar Tree Structure for Efficient LED Street Lighting

This paper shows the design of solar tree PV system for street lighting. In current days with enhancing the population and the energy demand, the Renewable Energy Source (RES) plays a major role and also, this energy could not cause any pollution and other natural hazards. The solar energy is more suitable one for this among other RES. India is a highly populated country, so the merit of such a solar energy that needs a very small space to produce energy efficiently. Flat or roof top mountings of PV systems are needed large land areas and problems in production of PV systems voltage due to partial shading of PV panels. Also, the scarcity of land is greatest problem in cities and particularly in urban areas in India. In order to overcome these harms, Solar Tree Structure Power Generation (STSPG) is developed. Hence, this article presents a design and fabrication of 120 Watts STSPG pilot plant for efficient LED street light application. The design structure of STSPG includes the support structure used to represent the leaves, the height, orientation and tilt angle of these leaves.

Light pollution affects space use and interaction of two small mammal species irrespective of personality

BackgroundArtificial light at night (ALAN) is one form of human-induced rapid environmental changes (HIREC) and is strongly interfering with natural dark–light cycles. Some personality types within a species might be better suited to cope with environmental change and therefore might be selected upon under ongoing urbanization.ResultsWe used LED street lamps in a large outdoor enclosure to experimentally investigate the effects of ALAN on activity patterns, movement and interaction of individuals of two species, the bank vole (Myodes glareolus) and the striped field mouse (Apodemus agrarius). We analyzed effects combined with individual boldness score. Both species reduced their activity budget during daylight hours. While under natural light conditions home ranges were larger during daylight than during nighttime, this difference vanished under ALAN. Conspecifics showed reduced home range overlap, proximity and activity synchrony when subjected to nighttime illumination. Changes in movement patterns in reaction to ALAN were not associated with differences in boldness score of individuals.ConclusionsOur results suggest that light pollution can lead to changes in movement patterns and individual interactions in small mammals. This could lead to fitness consequences on the population level.

Techno-economic viability of off-grid standalone PV-powered LED street lighting system in Lagos, Nigeria

The majority of the street lighting systems in Nigeria are predominantly composed of inefficient lighting fixtures powered either by the grid or diesel generators. Due to the epileptic nature of the grid and the fluctuations in diesel fuel pump prices, these methods for powering street lights are neither reliable nor sustainable. Use of energy-efficient lamps and photovoltaic (PV) panels has the tendency to reduce energy consumption and emissions. This study therefore presents a techno-economic analysis of deploying energy-efficient PV-powered street lighting systems using simple economic metrics. Environmental benefits of the proposed systems were also assessed by analyzing the reduction in CO2 emission as well as the equivalent of oil saved. Relative to the existing grid-powered metal halide system, installation of LED PV-powered street light reduced energy consumption by at least 80%, while the grid-powered LED configuration reduced energy consumption by 80%. Economic analysis shows that the simple payback period (SPP) for the LED PV-powered technology was less than three years, while that of the grid-powered LED system was less than two years. The LED PV-powered technology had the highest CO2 emission reduction of approximately 225 tonnes annually. Overall, street lighting using PV-powered and grid-powered LED is economically viable considering the payback time, net present value (NPV) and lifetime.

Techno-economic analysis of off-grid photovoltaic LED road lighting systems: A case study for northern, central and southern regions of Turkey

Street lighting is one of the sectors where off-grid energy systems are used, and in the past decade interest in these systems has increased due to recent developments occurred both in LED and PV technology. This paper presents a techno-economic analysis of off-grid PV LED road lighting systems for northern, central and southern regions of Turkey. Road lighting calculations are conducted using DIALux software for M4 and M5 road lighting classes to obtain optimal LED luminaires, pole sizes, and spacings. Among the obtained LED powers, load profiles are created using real lighting hours of operation of the selected regions. And then, the required PV-battery systems are optimized using HOMER software. Finally, sensitivity analysis is performed for future projections considering possible increases in electricity prices and decreases in component cost of the PV systems. The results showed that the levelized COE of the off-grid PV LED road lighting systems vary between 0.229 and 0.362 $/kWh for M4, and 0.254–0.359 $/kWh for M5 road lighting class, depending on the solar potential of the region. And, the total NPC of the entire lighting installation per km vary between 24296 and 29123 $ for M5, and 33225–44318 $ for M4 road lighting class. According to the results, the systems are infeasible under current conditions in Turkey. Nonetheless, they have the added benefits of contributing to the reduction of CO2 emissions. Moreover, future projections show that the systems can be feasible if the declining trend in PV system costs continues and electricity prices increase.

Techno-Economic Analysis of Off-Grid PV LED Road Lighting Systems for Antalya Province of Turkey

In this study, a techno-economic analysis of offgrid PV LED road lighting systems is made for Antalya province of Turkey. DIALux software is used for road lighting calculations and HOMER software is used in modelling, sizing, and optimization of the energy systems. Calculations are made to determine whether maximum or minimum pole spacing options for both twin-bracket central and opposite lighting arrangements provide the optimal system design for off-grid PV LED road lighting systems under the M3 lighting class in Antalya. The techno-economic analysis of the energy system in case of dimming LED luminaires after midnight is made. Since the payback periods of the systems are found to be above the system lifetime (20 years) with and without dimming, in addition to the current case, future projections, in which electricity unit prices increase and cost of PV system component and battery costs decrease, are examined.

Investigation of Thermal Performance of Cylindrical Heat Pipe Using Silver Nanofluid. Part I: Experimental Evaluation

Cylindrical heat pipes are widely used in various applications to transfer the heat effectively and efficiently. Besides parameters of heat pipe, its thermal performance mainly depends on the characteristics of working fluid also. Recently, various nanofluids have been considered as the most promising working fluid in different heat transfer applications. In the present paper thermal performance of cylindrical heat pipe using silver nanofluid as working fluid has been experimentally evaluated. Extensive experiments have been performed on cylindrical copper heat pipe having two-layer screen mesh filled with silver nanofluid in filling ratio of 40% with a vacuum of 10−3 torr. The thermal performance of heat pipe has been evaluated in terms of thermal resistance, thermal conductivity and overall heat transfer coefficient by varying parameters such as size of nanoparticle, concentration of nanoparticle, angle of inclination of heat pipe, heat load on heat pipe, average evaporator temperature and average condenser temperature to propose the best combination of parameters. The results indicate that the cylindrical heat pipe kept at 45° inclination angle and filled with silver nanofluid of 35 nm size of silver nanoparticle in 0.3% volume concentration yields higher thermal performance when it is operated at 120–140 W heat input. Thus, the cylindrical heat pipe under study is suitable for applications which require operation of heat pipe at some angles, such as cooling of high-wattage LED street lights.

Design of Solar-Powered LED Road Lighting System

Turkey is rich in terms of renewable energy sources and, therefore, is now encouraging the use of sustainable clean lighting systems in road applications. High pressure sodium lamp is the most widely used type in main roads, but other types of lamps such as mercury vapour lamps or metal halide lamps can be utilized for street lighting. Since it enables energy and money saving, LED light technology has replaced high pressure sodium lamps nowadays. Once solar power system (PV) is integrated with LED lamp for street lighting, the amount of saving and local impact might be enriched. LEDs used as light sources in road lighting luminaires with rising lumen values, decreasing junction temperature, higher colour rendering efficiency, longer lifetime have become more efficient than many light sources with the latest developments. Since the structure of the luminaires in which the LED light sources are used differs from that of the conventional light sources, the optical, thermal and electrical design of the LED luminaires must be considered differently. Thus, this study concentrates upon design considerations and the operating principle of solarpowered LED road lighting luminaire in details. Also, a simple solar panel system was designed and the economical values obtained at the end of 20 years were compared when using the ongrid system and the off-grid system.

Contradiction Analysis and Solution in the R&D of High-Power Solar LED Street Lamp Controller

As being restricted by factors such as cost, efficiency and size, the development of high-power solar LED street light controller is faced with plenty of difficulties. In case that a structure of two independent DC/DC is applied as the main circuit, it has to face problems such as large size and high cost; in case of applying the bidirectional BUCK/BOOST circuit, it requires change-over switches to control the solar panel and LED light. As being restricted by withstanding voltage, on-resistance and cost, a PMOS device cannot be used as the change-over switch of solar panel and LED light. However, when being used as a change-over switch, an NMOS device must apply the low-side mode under which the negative ends of the mentioned three parts are cut off. In the condition of applying the low-side mode, a differential circuit must be used to detect the voltage of the solar panel. Furthermore, in order to make sure batteries can still be regularly charged after wearing out in daylight, the controller must be supplied with power through a dual power supply circuit that can obtain power from both the solar panel and the battery. The demander has a requirement on extremely low standby power consumption of the product, and thus it is necessary to minimize the circuit that is live while working in standby mode. Methods: The bidirectional BUCK/BOOST circuit structure is applied to the main circuit to realize a higher change-over efficiency while giving considerations to both cost and size. The NMOS device, model IRFB4410ZPBF, with a price of about three yuan, is used as the switching device, and the low-side mode is applied, that is the switches inserted in between negative end of the solar panel or LED light and that of the DC/DC circuit. The low-cost rail-to-rail operational amplifier LM358 is used to form a differential amplification circuit for detecting the voltage of the solar panel. A XL1509-12E1 chip that only costs 0.88 yuan/pc is selected as the main change-over chip for the power supply, which has realized the highly-efficient and low-cost change-over of the power supply. A dual power supply circuit and a step-down protective circuit are designed for the XL1509-12E1 change-over chip. By comparing solar panel voltage with battery voltage, the solar panel booting circuit is realized. Only when solar panel voltage is higher than battery voltage, does the system program start to power it up for running, so that the outage of most of the circuits of the system under standby mode does not consume energy. Furthermore, the solar panel voltage detecting circuit, the solar panel booting circuit and several return difference functions are corrected during system debugging. Results: The circuit board of the entire controller features small size, low cost and high efficiency. It measures about 100*62*18mm in size, costs about 60 yuan, and the charge/discharge change-over efficiency reaches up to over 95%. The controller has many functions: it is capable of operating within a large scope, in which, solar panel voltage is subject to 15~50V, LED light voltage is subject to 15~60V, battery voltage is subject to 10~35V and battery-end charge/discharge current is 10A; it is capable of adapting to monocrystalline silicon/multicrystalline silicon/thin-film and many other kinds of solar panels, as well as lithium/lead-acid and many other kinds of batteries; it is capable of detecting the conversion of day and night, automatically controlling charging and discharging and automatically making adaptive adjustment according to seasonal variations; the current to be consumed during standby will be maintained below 3mA, and thus the power consumption is extremely low. Conclusion: By selecting the bidirectional BUCK/BOOST circuit structure, applying low-side mode for switching of solar panel and LED light, using a differential circuit to detect solar panel voltage, using a low-cost DC/DC chip to realize power supply change-over, designing a dual power supply circuit, introducing solar panel booting circuit and other hardware design, as well as MPPT algorithm, state recognition and control, return difference control and other software design, a solar LED street light control product featuring small size, low cost, high efficiency and multiple functions is successfully developed.

Drivers’ Preference for the Color of LED Street Lighting

The purpose of this paper was to initiate broad research aimed to establish the preferred color of light of LEDs from a driver's point of view. Two street lighting installations (one with 3000 K and the other with 4000 K LEDs) were evaluated both objectively and subjectively. The objective evaluation, realized using a CCD camera, included detection of small targets and pedestrians. A slight advantage was identified for the 3000 K lighting installation regarding both types of target. As for subjective evaluation (realized through a questionnaire), the task of the participants (drivers) was to choose the more appropriate between the two lighting installations regarding six lighting parameters, as well as the overall visibility. The 3000 K LED installation was evaluated as a better solution for most analyzed parameters, as well as for the overall visibility. However, only the results regarding the color of the light (in favor of the 3000 K LEDs) and the detection of small light-colored obstacles (in favor of 4000 K LEDs) were convincing, which was confirmed by the statistical analysis. Due to the obtained mild preference for the 3000 K LEDs and several limitations/challenges of the conducted surveys, it was concluded that additional research is needed in order to decide on the preferred color of light of LEDs from a driver's perspective.

Warm white versus neutral white LED street lighting: Pedestrians' impressions

The subjective impressions of pedestrians are necessary in order to decide on the appropriate colour of light to be used for street lighting. Therefore, a pilot project aimed to compare subjective evaluations of the sidewalk illumination under two street lighting installations, realised by LEDs of 3000 K (warm white) and 4000 K (neutral white), was recently conducted in Belgrade. Both installations had comparable sidewalk illuminances as well as other relevant photometric parameters. The evaluation was done through a questionnaire. A group of 139 (61 male and 78 female) respondents, all of them university students, was asked to grade both lighting installations for the sidewalk light intensity, the appearance of human faces, the colour of light and the colour rendering as well as the overall impression. According to the median values, the 3000 K LED installation was considered better than the 4000 K installation for all aspects assessed as well as the overall impression. Although the survey results convincingly showed a preference for 3000 K LEDs for this comparison, additional research is needed using a more representative sample of people and a wider range of locations before a definite conclusion can be reached.

A comparative study of 2-D and 3-D conjugate natural convection from a vertical rectangular fin array with multilayered base subjected to distributed high heat flux

This paper presents a comparative numerical study of 2-D and 3-D steady, laminar conjugate natural convection heat transfer from a vertical rectangular aluminium fin array subjected to a distributed high heat flux related to the cooling of a 105 W LED street lighting luminaire. The effect of radiation is also considered in the aforementioned models. The 2-D model uses the Stream function-Vorticity-Temperature approach. The finite-difference methodology is used to discretize the governing equations. The discretization method in the 3-D model is finite-volume. The solution algorithm is SIMPLE (Semi-Implicit Method for Pressure-linked Equations). A detailed parametric study based on a realistic lamp data is conducted to observe the effect of heat flux, fin spacing, fin height, fin width, fin thickness and fin material (aluminium, brass, copper, mild steel) on the fluid (air) velocity and temperature distributions, heat transfer and LED junction temperature. A novel finding of this work is the revelation of asymmetric flow and thermal fields in the successive channels of the fin array, as predicted by the 3-D model. In contrast with the existing studies in which fin base is treated as isothermal, an optimal fin spacing is found to exist corresponding to the maximum heat transfer coefficient in the present study. The difference between 2-D and 3-D model-predicted average heat transfer coefficients increases with increase in fin height to fin spacing ratio. The contribution of radiation heat transfer is about 8–14% of the total heat transfer in the range of dimensions of the fin array considered in this work. A penalty function based optimization study is carried out to maximize the average heat transfer coefficient while maintaining the LEDs below the safe limit of 353 K. Finally, correlations for predicting the average heat transfer coefficient in the vertical rectangular fin array heat sink, and the maximum LED temperature as a function of luminaire wattage and geometric parameters of the fin array have been presented.

Catadioptric freeform optical system design for LED off-axis road illumination applications.

The aim of this paper is to develop a new composite structure of catadioptric optical system containing both freeform refractive surface and freeform total internal reflective (TIR) surface for LED road illumination applications. The role of freeform refractive part is to generate the shifted general rectangular illumination pattern to optimally match the shape of the road surface. The application of TIR mechanism is aimed to control the stray light in the sidewalk direction of the road luminaire and maximize the efficient energy efficiency. In this paper, we use the "double pole" ray mapping technique to design the refractive optical surface and the θ-φ coordinate ray mapping technique to derive the freeform TIR surface. The simulation shows that the novel catadioptric design has relatively high collection efficiency, thus high average illuminance level inside the effective illumination area. This lens also has good control of stray light on the backside of the road luminaire.