LED Luminaires Research Articles

Energy conservation potential in highway illumination system: A Techno-Enviro-Economic study on retrofitting HPS with LED luminaires

Adequate and appropriate illumination across the highway isessential for safety. High-pressure sodium luminaires (HPS) are usually standard throughout Pakistan. However, with the advancements in illumination technologies and growing trend of energy efficiency, retrofitting of conventional HPS luminaires with light-emitting diode luminaires (LEDs) is becoming popular. Low energy consumption, high color rendering index (CRI), longer life span, and variety in correlated color temperature (CCT) make LED luminaires ideal for replacing inefficient HPS lights. The retrofitting of HPS with LED illumination system comes with a capital cost, and its feasibility depends on the energy conservation potential. This study presents a case of 4,014 HPS luminaires installed across an 85 km long highway in second highly populated city of Pakistan. A targeted energy audit of HPS illumination system was conducted and compared with the proposed LED system of equivalent illumination quality. The results indicate that by retrofitting the HPS luminaires, the energy consumption can be reduced by 60% and with 83.3% reduction in the apparent power. Furthermore, the proposed LED illumination system will significantly improve the power quality, light noise, energy losses, carbon footprint, and operational cost.

Intelligence system for monitoring and governing the energy efficiency of solar panels to power LED luminaires

Developed in this work are the principles for creation of a system to control and governing the energy efficiency of solar panels providing power supply for LED luminaires. Realization of these principles allows the most efficient using the electric power generated by solar panels, to save in a real-time scale the data about system functions as well as provide a complex analysis of these data. Optimization of using the electric energy generated by solar panels will enable to determine the maximum possible power in each specific moment and to automatically tune its consumption. The complex data obtained with this system can be further used for not only statistical fixation of the produced and consumed electric energy in fact but also for prediction of the energy amount that will be generated by these solar panels in future. The analysis of results will enable to optimize the area of solar panels and more exactly determine parameters of electronic components both for illumination systems and designing solar photoelectric stations of various purposes.

Short Free-Standing Pole LED Luminaire and Lens Design for Road Lighting

Road luminaries are required to provide the luminance specified in the standards according to the road characteristics. For this reason, the light from the light source should be directed according to the desired conditions. While the range of minimum average road surface luminance recommended for different classes of road are provided; at the same time, it is desirable to be economical. In this study, a freeform lens and LED luminaire design with high luminous efficacy, low glare and uniform luminance distribution with a height of 1.5 m and a distance of 7 m between poles were designed for M3 road standards. First of all, lens design was made by using optical and illumination design software. Also, lens manufacturing and luminaire production were made as a result of the success of the design simulation test. The success of the LED luminaire in providing CIE standards has been measured on the designed road. In addition, the advantages and disadvantages have been determined by comparing with High Pressure Sodium Vapor (HPS) lamps.

Effect of adaptive control on the LED street luminaire lifetime and on the lifecycle costs of a lighting installation

We report for the first time the effect of ageing due to adaptive control of lighting on the lifecycle costs of luminaire installations. Two types of LED street luminaire were aged (1) as the luminaire lit for 9 hours and then switched off for 3 hours and (2) under intensive ageing using adaptive control conditions mimicking presence of vehicles, where the luminaires were switched with 30-second interval between 100% and 20% power within the cycle of (1). The test continued for 32,000 hours. Luminaire lifetime was found to decrease by 10% due to the intensive adaptive control, which exaggerates the ageing as compared to real traffic conditions. We estimate that a realistic rate of dimming cycles would decrease the luminaire lifetime by 0–2%, increasing the lifecycle costs of a lighting installation by 0–0.7%. With a traffic-aware control system, capable of 50% energy saving in lighting, the lifecycle costs are estimated to reduce by 25% as compared to a similar LED luminaire installation without traffic-aware control, outweighing the costs due to the reduced lifetime. The smart controlling of lighting is considered as a useful way to meet future energy saving targets.

Design and Analysis of High-Efficient Driver Model for LED Luminaires

LED luminaires need a driver circuit for working properly. Most of the drivers have disadvantages such as losses during operation. This issue becomes more important while supplying with limited sources such as renewables. To overcome the problem, this study proposes a novel energy efficient driver for LED luminaires based on zero voltage switching (ZVS) single-ended primary inductance converter (SEPIC) technology. Driver and hence luminaires were designed to be fed from photovoltaic (PV) panels. In addition, an adaptive MPPT algorithm was developed to obtain optimum efficiency from supply system. SEPIC approach was preferred for MPPT application due to its advantages such as non-reversing polarity. This feature allows energy efficiency in corporation with ZVS. Proposed model was designed under PSIM platform with all components; PV panels, ZVS, SEPIC, and LED luminaires. A detailed analysis was performed by using system graphs under various operating conditions as different irradiance levels. Results show that proposed model is energy efficient and modular because of its low-volume structure. Therefore the model can lead smaller driver circuits with minimum losses.

Simulation Study on Factors to be Considered for Each Type of Indoor Luminaires and Light Sources when Converting to LEDs

As high-efficiency lighting has become mainstream, conversion of lighting equipment is under way, starting with government agencies. Existing fluorescent luminaires are being converted with LED luminaires. The main method used for conversion is to remove the fluorescent lamp (case 1) and replace it to a tubular LED lamp, and convert the luminaire itself with a LED panel luminaire (case 2). However, focusing only on energy efficiency, the existing luminous environment are not considered, such as illuminance, illuminance uniformity, and UGR. Therefore, the optical characteristics were measured using the actual luminaire used in the conversion. Simulations were performed comparing the luminous environment and power consumption before/after conversion. Case 1 had advantages in power consumption and UGR over case 2, and the illuminance was slightly reduced, but it met the criteria. These results confirmed that the conversion of lighting devices at least ensured the existing luminous environment.

A method of fast quality control inspection of loop heat pipe

The dynamic behaviour of loop heat pipe (LHP) changes with heat load and physical properties of LHP such as fluid charging, wick material, and tolerance in manufacture. The start-up phenomena of a LHP can be classified into four modes, according to the heat load Qin : failure mode, oscillating mode, overshoot mode, and normal mode. It is found that the operation mode is related to the rate of temperature rise in evaporator during initial transient performance using a step heating load. The abnormal high rate of temperature rise can be observed for LHP with failure, oscillating or overshoot mode performance. Based on this phenomenon, the normal-mode performance of LHP can be assured from a short transient test in about 80s using a step heat load, instead of using steady-state test (taking 1,800s). This transient test method has been applied in the quality inspection of commercial loop heat pipe in mass production. No LHP failure was found for more than 10 years for about 30,000 sets of street LED luminaires designed with LHP.

Investigations of Electrical and Optical Parameters of Some LED Luminaires—A Study Case

In the paper, the electrical and optical parameters of wirelessly controlled LED lamps of the Hue type are analysed. Features of this class of wirelessly controlled LED lamps given by the producer are described and a measuring setup for the electrical and optical parameters of the considered LED lamps is proposed. The results of measurements of the two investigated lamps with variable hue, based on RGB chips or emitted white light of different CCTs (correlated colour temperatures), are shown and discussed. Attention was given to the parameters characterising the influence of the tested LED lamp on such electric power quality indicators as PF (power factor) and THD (total harmonic distortion). Therefore, the influence of voltage supply and the selected value of power density of the emitted light on the THD and PF is analysed and discussed.

Lighting for Cultural and Heritage Site: An Innovative Approach for Lighting in the Distinct Pagoda-Style Architecture of Nepal

Nepal houses many traditional and cultural sites rich in historical cultural diversity. These sites are also economically important to the nation. These monuments show the culture and the living beliefs of the communities; hence, people from all over the world are attracted to such place to observe the beauty and to feel the spirit and the conservational perspectives behind these articulated edifices. In today’s context, artificial light is a basic necessity for human activities and has been used in various applications: one such application being night-time illumination of historical sites and monuments. Most of the historic monuments in Nepal were constructed during the 15th to 18th century and are designed to incorporate oil-based wick lamp as the light source. Recently with the availability of modern luminaires and lack of technical expertise and scientific approach, most of the historic sites are being filled up with uneven, exaggerated, and inappropriate illumination. This inappropriate illumination practice may lead to negative consequences that may create disturbance to human and the surrounding environment. Scope of this paper is to identify the special needs for illuminating cultural and heritage sites with Pagoda-style architecture and introduce a methodology for a case study in Nepal. As a first step, this paper analyzes lighting malpractices in the temples of Nepal at different geographical locations and cultural values. As a next step, a prototype LED luminaire that enhances the unique type of architecture of Nepalese heritage sites was built, installed, and demonstrated in one of the temples. The work presents the design process of the lighting system and the results of a new lighting installation. The study also discusses possible problems that may arise while designing lighting for cultural and heritage site and provides recommendations on considerations to be taken during the design.

Voltage distortion in LED street lighting installations

The paper considers two power quality issues: voltage distortion and voltage drop along the pole lines of different LED street (road) lighting installations. The research includes three parts: (1) development of a novel model and the corresponding software for calculating voltage harmonics in the three-phase LED street lighting installations, where the load is nonsymmetrical and nonlinear. The model is based on the application of symmetrical components and the impedance per phase model. (2) Experiments on two sections of a pilot street lighting installation, one with 6 poles with neutral white and the other with 5 poles with warm white LED luminaires (the former were with conventional, and the latter with improved drivers regarding harmonic emissions). Their results were used to define harmonic characteristics of the LED luminaires and validate the model. (3) The developed software was applied to four typical street (road) lighting installations, two with a single-sided and two with a central pole layout. The major outcome was the determination of the maximum permissible number of the LED luminaires which can be connected to the feeding cable without exceeding any of the limits related to voltage drop, total voltage harmonic distortion and individual voltage harmonics in either the full or reduced street lighting regimes.

Melanopic Limits of Metamer Spectral Optimisation in Multi-Channel Smart Lighting Systems

Modern indoor lighting faces the challenge of finding an appropriate balance between energy consumption, legal requirements, visual performance, and the circadian effectiveness of a spectrum. Multi-channel LED luminaires have the option of keeping image-forming metrics steady while varying the melanopic radiance through metamer spectra for non-visual purposes. Here, we propose the theoretical concept of an automated smart lighting system that is designed to satisfy the user’s visual preference through neural networks while triggering the non-visual pathway via metamers. To quantify the melanopic limits of metamers at a steady chromaticity point, we have used 561 chromaticity coordinates along the Planckian locus (2700 K to 7443 K, ±Duv 0 to 0.048) as optimisation targets and generated the spectra by using a 6-channel, 8-channel, and 11-channel LED combination at three different luminance levels. We have found that in a best-case scenario, the melanopic radiance can be varied up to 65% while keeping the chromaticity coordinates constant (Δu′v′≤7.05×10−5) by using metamer spectra. The highest melanopic metamer contrast can be reached near the Planckian locus between 3292 and 4717 K within a Duv range of −0.009 to 0.006. Additionally, we publish over 1.2 million optimised spectra generated by multichannel LED luminaires as an open-source dataset along with this work.

Accelerated Testing Based Lifetime Performance Evaluation of LEDs in LED Luminaire Systems

LED luminaires have taken over other traditional lighting solutions in all possible lighting applications due to advances such as high lifetime, power efficiency, adaptability in size, shape, and different color generations. The reliability of the LED luminaire as a system was determined by the lifetime performance of the driver electronics. The advancements in power electronics led to more reliable components and products. The LED luminaire’s reliability is determined by the light output and color appearance quality, and quantity. The importance of single LEDs performance in the LED luminaires is most recently realized and needs to be explored. The manuscript presents the analyses of the lumen output and Duv based life estimation, the variations in color appearance in terms of xy chromaticity, and spectral power distribution of two luminaires having same electrical and optical specifications employing different type of LEDs subjected to different accelerated operating conditions. The results identify the predominant failure indicators for lumen and color changes, and show that LED physics & device packaging also play a significant role in the reliability study of an LED luminaire. The results of the manuscript are helpful for LED luminaire manufacturers to enhance the lifetime of LED luminaires by suitable moderation in the LED package design in terms of lumen output and color quality maintenance as per specific application requirements.

Led lamp driver modelling

Currently, there is an increase in the use and production of energy-saving lamps of various types – fluorescent and LED ones. However, it has been found that the use of technologies that have proven themselves in the creation of luminescent sources for LED light sources is ineffective. The use of traditional secondary optics for LED luminaires makes it difficult to create an effective heat sink from LEDs, while the durability of LEDs significantly depends on the heat sink. Another important issue when designing LED luminaires is choosing the right driver. The power consumption of LEDs from the primary network depends on the efficiency of the driver used. The choice of the type of driver also determines the amount of heat that should be removed from its elements. A significant factor influencing the choice of a driver is also the possibility of its operation in conjunction with a voltage regulator – a dimmer, in order to control the illumination. It is also necessary to take into account the IEC recommendations that require manufacturers to use active power factor correctors for devices with switching power supplies and / or electronic ballast with a power of 20 watts or more. Therefore, there is a task of developing a highly efficient driver for use in LED luminaires. In the process of reviewing modern drivers, a driver based on the LT3799 microcircuit from Linear Technology was selected for further research, which is distinguished by high efficiency, working with a large number of produced LEDs, has a built-in active power factor corrector, and allows the use of dimmers. The inclusion of the driver chip recommended by the manufacturer was applied, with the addition of noise suppressing components. The galvanic isolation of the power supply circuits of the LED matrix is provided. Next, the analysis of the characteristics of the selected circuit design solution is carried out using computer simulation. LTSpice EDA was chosen as a modeling tool, which is distinguished by its versatility, ease of use and high reliability of results in comparison with similar software products. The modes of operation are analyzed depending on the requirements for the pulsation of the emitting matrix, the operation of the power factor corrector, and the suppression of interference into the industrial network from the operation of the source is estimated. Various options for the development of the circuitry implementation of the driver based on the LT3799 microcircuit and the operating modes of the most heavily loaded elements are analyzed: an inductor, a key transistor, a damper circuit, a diode in the power supply circuit of an LED matrix. Optimal values of circuit components and parameters of winding elements were selected. It is shown that due to the operation of the power factor corrector, the shape of the current consumption from a sinusoidal voltage source is also almost sinusoidal, which leads to an almost active nature of the load. The modes of operation of the LED matrix for the nominal supply voltage and for the reduced one (with a dimmer) are considered. Methods of implementation of a soft start of an LED matrix are described. Based on the results of the work, conclusions are drawn that summarize the expediency of using the developed driver for an LED device based on the LT3799 microcircuit.

Metabolic Variations in Grass C. dactylon and Selection of Optimal LEDs for the Horticulture Luminaire Using LM Algorithm

Healing of various ailments using herbal medicines is gaining much interest. Plants classified as grasses, specifically Cynodon dactylon , are an appreciated group of monocots used in many herbal remedies. In this work, C. dactylon , is grown naturally and also under market available LED Luminaires with different lighting conditions. Until 2010, most of the plants are grown under conventional lamps that are not spectrally tunable. Cynodon dactylon , the grass is grown under two different light spectrum, two light levels and three photoperiods (9hours, 12 hours, 15 hours) to extend our experiential knowledge. The biomass accumulation was the highest when grown under a lower RB ratio-12-hour- $163\mu $ mol/s, and phenolic content was the highest at 92.8 mg/g wt Gallic Acid Equivalents under combined light source at 15-hour photoperiod. A spectrally tunable LED light source with an optimal quantity of LEDs saves cost, space and energy. Considering the light parameters from the light sources used for growing C. dactylon , Levenberg–Marquardt (LM) algorithm is implemented to select an optimal LED quantity that composes the light source. The algorithm simulates the given target spectrum with minimum fitness error. The method applied to model LEDs, its validation against the practical LED spectrum, spectrum matching and computation of Luminous flux, Photosynthetic Photon Flux and efficacy are also presented. Many spectrums are simulated to validate the performance of the algorithm. A solution of optimal LEDs for three Photosynthetic Photon Flux (PPF) levels with LEDs is derived, and it is observed that the number of LEDs increased with PPF.

Study of the Statistical Relationships of LED Luminaires Characteristics

Study of the Statistical Relationships of LED Luminaires Characteristics

Research of the photobiological safety of led lamps and luminaires for general lighting

The paper analyzes the methods of assessing the photobiological safety of LED light sources according to international standards. It provides information on test equipment for determining the spectral composition of radiation and photometric parameters on the basis of which LED products are classified by risk groups of blue light. LED lamps and luminaires for general lighting in various spheres including household, public and office premises, outdoor lighting, etc. are studied. The level of danger of blue light is assessed at a distance at which the illuminance of 500 lux is formed, as well as at a distance of 200 mm (the most unfavorable conditions) according to the recommendations of international standards IEC 62471, IEC/TR 62471-2 and IEC/TR 62778. The results of the study of certain industrial samples of LED lamps and luminaires available on the Ukrainian market are presented.It is shown that the vast majority of LED products for general lighting have photometric parameters that do not exceed the group of insignificant risk RG1. All studied lamps in which low-power LEDs and bulbs with light scattering coating are used belong to the general group RG0 (no risk). Luminaires with low-power and medium-power LEDs, that have diffuse light diffusers, also correspond to the risk group RG0. Only luminaires with bright small-sized LEDs that don’t have the light diffusers (angular size less than 11 mrad) exceed the limits of the RG1 low-risk group. The number of such lamps does not exceed 10% of the studied products. At a distance at which an illumination of 500 lux is formed, the danger of blue light does not exceed the RG1 group. When the photobiological safety of blue light was measured from a distance of 200 mm, part of the luminaires with RG0 were moved to the group RG1, and luminaires from the group RG1 were moved to the group RG2. For luminaires belonging to the group RG2, the limit distances at which the luminaires still belong to the group RG1 were calculated.It was noted that a set of test equipment for determining the spectral composition of radiation and photometric parameters, as well as the software used to process the measurement results, significantly increases the productivity of assessing the photobiological safety of LED products. It was proposed that regulatory documents and catalogs for LED lamps and luminaires should declare the maximum luminance of these lamps.

Thermal Analysis In Fixed, Flowed And Airless Environment For Cooling In Led Luminaires

In this study, a simulation study was conducted for the loss of efficiency caused by the heat emitted by the LED chips. The temperature change of LED luminaire was analysed for three different scenarios using finite element method. Due to the increase in the internal temperature of the luminaire and due to the air effect inside the LED luminaires, failure of the LEDs has been tried to be prevented. For this purpose, a passive cooling method was proposed in the simulation environment. So, in high power LED luminaires, the high heat emitted by the LED chips is reduced to low heat by an air flow method. In this way, efficiency in LED outputs has been achieved.

Energy-Saving Led Lighting System With Parallel Power Supply By Photovoltaic Modules And By Network

The current state of LED lighting systems with parallel power supply by photovoltaic modules and central power supply network is analysed. The approach to implementation of parallel operation of LED luminaire powered by two sources of power is presented. It is simple, cheap and highly reliable as compared to the existing solutions. Based on this approach, four diagrams are developed which are applicable correspondingly to lighting applications and characteristics of photovoltaic modules and power consumers. The first and the second diagrams contain minimal quantity of transformers, but a number of operational constraints shall be taken into account when using them. The third diagram contains standard transformers and implies minimal number of various constraints, which makes it an optimal solution for the low-power lighting system being designed. The fourth diagram is expensive due to utilisation of equipment with automatic maximum power point tracking (the MPPT technology); it provides maximum possible energy efficiency of the lighting systems but the advantages of the MPPT technology apply only to high-power systems. It is preferable to use such objects where lighting is mostly required during daytime as consumers of such systems (shopping malls, underground passages, storage facilities, poultry farms, etc.). A positive aspect is increase in reliability of consumer power supply since power supply of LED luminaires will be also provided by an additional source. The proposed approach leads to reduction of power consumption for LED lighting, saving of fossil energy sources and therefore to ecologisation of the environment.

Analysis Of Failure Detection And Visibility Criteria In Pantograph-catenary Interaction

The main purpose of new studies investigating pantograph catenary interaction in electric rail systems is to detect malfunctions. In the pantograph catenary interaction studies, cameras with non-contact error detection methods are used extensively in the literature. However, none of these studies analyse lighting conditions that improve visual function for cameras. The main subject of this study is to increase the visibility of cameras used in railway systems. In this context, adequate illuminance of the test environment is one of the most important parameters that affect the failure detection success. With optimal lighting, the rate of fault detection increases. For this purpose, a camera, and a LED luminaire 18 W was placed on a wagon, one of the electric rail system elements. This study considered CIE140–2019 (2nd edition) standards. Thanks to the lighting made, it is easier for cameras to detect faults in the electric trains on the move. As a result, in scientific studies, especially in rail systems, the lighting of mobile test environments, such as pantograph-catenary, should be optimal. In environments where visibility conditions improve, the rate of fault detection increases.

Electro-optical characteristics of an innovative LED luminaire with an LED matrix cooling system based on heat pipes

Widespread use of energy-saving LED lighting systems powered by renewable energy sources, solar energy in particular, will contribute to the improvement of global ecology. One of the structural elements of such lighting systems is LED luminaire. The authors of this article perform a first ever experimental study of electro-optical characteristics of the basic version of a compact high-power LED luminaire for indoor use. The particular feature of this lighting device is that its cooling system for the LED light source is based on heat pipes and concentric cooling rings. Such design allows ensuring the required cooling efficiency of the LED matrix. The revealed trends in optical and electrical parameters during temperature stabilization indicate that the proposed cooling system is highly efficient in maintaining normal thermal conditions of LED light sources with a power of up to 140.7 W and a luminous flux of up to 15083 lm. The results on determining spatial distribution of luminous flux of these luminaires indicate that they may be used for lighting large rooms with high ceilings. Scaling the basic modular design version of the cooling system allows increasing the power of the LED light source up to 600 W.