LED Luminaires Research Articles

MACHINE LEARNING MODEL FOR GLARE PREDICTION IN OFFICES WITH SIMPLE ARCHITECTURAL FEATURES

ABSTRACT Daylight glare index (DGI), daylight glare probability (DGP) and glare-sensation (GS) predictive models are the widely used glare indices for the assessment of occupant visual comfort in daylit spaces. This paper presents the development and implementation of Machine Learning models to predict these glare indices. The training and validation data sets were collected from sensors incorporated in the test room with motorized Venetian Blinds and dimmable LED luminaires. Predictor and response data were obtained from conventional sensors, digital cameras, and the EVALGLARE Software. The regression models predict DGI and DGP, whereas the classification model predicts GS. In addition to standard statistical error evaluation metrics, the hypothesis test assesses the performance of regression/classification models. The results reveal that Ensemble Tree (ET) models are highly accurate at predicting glare indices. The proposed technique attempts to simplify the existing traditional Glare Index(GI) estimation method. The combination of real-time daylight glare prediction and suitable window shading control increases occupant visual comfort. A high dynamic image-based system is employed to verify the measurements made using traditional sensors.

Low-Complexity Layered ACO-OFDM for Power-Efficient Visible Light Communications

Commercially available LED luminaires demand both low-complexity and high power efficiency from visible light communication (VLC) deployments. Layered asymmetrically clipped optical orthogonal frequency division multiplexing (LACO-OFDM) is attracting increasing interest due to the high spectral efficiency and high power efficiency. However, these advantages come at the price of high computational complexity at both transmitter and receiver. In this paper, we propose a low-complexity LACO-OFDM (L-LACO) to generating identical signals to conventional systems while employing a half-size IFFT/FFT and possessing low implementation complexity. The required number of real-valued multiplication operations and real-valued addition operations are quantified and compared to conventional LACO-OFDM. The saved power corresponding to the reduction in arithmetic operations is also estimated, which is shown to increase logarithmically with number of subcarriers, and to increase linearly with modulation bandwidth. Numerical results show that the proposed L-LACO requires about half the number of arithmetic operations as LACO-OFDM for both the transmitter and the receiver. The BER performance of L-LACO is estimated by Monte Carlo simulations under a VLC line-of-sight (LOS) channel and under a VLC dispersive channel that is shown to be identical to LACO-OFDM.

The impact of melanopic illuminance and CCT on spatial brightness perception of illuminated interiors and energy-saving implications

Modern interior lighting design pays increased attention to spatial brightness appearance of illuminated spaces. However, spatial brightness is affected by spectral power distributions (SPDs) of lighting in a manner that cannot be predicted based on the traditional photometric quantities such as illuminance and luminance. Understanding the other contributing factors of lighting spectra to spatial brightness is important for improving energy efficiency of lighting in built environment, especially in indoor spaces where natural ambient illumination by daylight is lacking and electric lighting is heavily relied on.In this work, the experiments of spatial brightness comparisons were performed in a windowless room equipped with spectrum-tunable LED luminaires that delivered indirect light to observers with individually controllable parameters at the eye-level, such as photopic illuminance, cyanopic illuminance, melanopic illuminance, and correlated color temperature (CCT). A method was developed to quantitatively compare spatial brightness between lighting scenes with different SPDs. The results showed that great differences in the effectiveness of spatial brightness exist among SPDs. Both melanopic illuminance and CCT make contributions to spatial brightness, but with different intensity-dependent behaviors. Furthermore, the M/P ratio (melanopic to photopic ratio) is likely to have a clear positive correlation with spatial brightness at a fixed photopic illuminance. The results of this study could help improve energy efficiency in indoor lighting.

Study on the Power Quality of LED Street Luminaires

The paper analyses the power-quality effects of connecting LED luminaires to street lighting installations. The power quality impact of LED luminaires and the implementation of smart control systems are discussed. Several power-quality measurements have been performed to determine the effect of connecting multiple LED luminaires to the electrical power network. Three LED street lighting systems were selected, each equipped only with LED luminaires of different power ratings and numbers, produced by different manufacturers. The measurements were performed at the lighting connection box, and the results are presented and discussed for each case.

A comprehensive detailed formula for LED degradation and lifetime estimation leading to reduce CO2 emissions

Recently as global warming and (green-house gases) GHG emissions topics have become hot, many countries have pledged for decreasing their carbon footprint in a reasonable time. Since a substantial part of carbon footprint is coupled with electric energy consumption and in turn, a considerable part of consumed electrical energy around the world is related to the lighting, as energy efficient light sources LEDs have attracted notices to themselves. According to long lasting LEDs as semiconductor light sources, they face a great amount of lumen depreciation during their lifetime. Since, besides environmental impact, economic aspects are also of great interest for users, it is important to be able to anticipate the LEDs lifetime as exact as possible. This enables users not only to select the correct LED luminaires by cost-benefit analysis, but also to schedule for renewing them in the right time. As mentioned in former researches LEDs can show better lumen maintenance than what is estimated by prevalent TM 21 standard method. This paper proposes a comprehensive detailed formula for finding LEDs’ more accurate lifetime. The novelty of the research methodology is breaking up the LED to its major parts and by finding each part degradation model and combining them, coming up with the ultimate accurate formula. The proposed formula anticipates longer lifetime than what estimated by TM 21 method especially for low currents and temperatures stresses. Also, constant lumen output drivers (CLOs) are designed based on proposed comprehensive formula and TM 21 lumen maintenance projection method and their efficacies are compared. According to lower lumen depreciation anticipation, less energy delivery to LED for compensating depreciation is needed for CLOs designed based on proposed formula. By less energy consumption, using proposed comprehensive formula can lead to less CO 2 emissions.

Is it possible to achieve quality lighting without considering the photometry of the pavements?

In this study, the photometry of a wide range of conventional and innovative pavements used in urban and interurban areas was characterised with a laboratory gonioreflectometer, both in new condition and after 30 months of natural ageing. An extreme diversity of behaviour with respect to light reflection has been demonstrated, both over time and between pavements. Various lighting studies have been carried out for cases of renewal of lighting installation with the installation of LED luminaires on poles in place. The calculations have shown that the use of typical CIE r-tables almost systematically leads to non-compliance with the EN 13201 standard, particularly in terms of uniformity. On the other hand, taking into account in the calculations, the photometry of the pavement in its stabilised state makes it possible both to respect the challenges of lighting safety and to achieve significant energy savings. As measurements of pavement photometry are rarely carried out, an alternative is to set up a database of urban pavements, which is one of the achievements of this research.

Contrasting effects of street light shapes and LED color temperatures on nocturnal insects and bats

Street lights are important light sources that contribute to artificial light at night (ALAN). To date, ecological impacts of individual LED properties (color temperature, dimmability) have been studied, while interactions between light properties or aspects of luminaire design have not been addressed. However, the design of luminaires can influence ALAN impacts as the shape determines the spatial distribution of light and its visibility in the environment. This may cause amplifying or mitigating effects. We assessed the relative individual and interacting effects of two LED luminaire designs and three LED color temperatures (1750 K, 3000 K, 4000 K) on nocturnal insect abundance, bat foraging and feeding activity. We considered a standard LED luminaire shape with focused light emission and a luminaire shape with a diffusor to scatter the light spatially, leading to increased visibility of the light in the environment. During 104 nights, we trapped 51263 nocturnal insects of which 97% were caught at lights and 3% at dark sites. For bats, up to 44.8% fewer acoustic signals were recorded at dark sites. We caught 31% insects at LEDs with1750 K, 34% and 35% at 3000 K and 4000 K, respectively. Thus, color temperatures of 1750 K proved less detrimental than 3000/4000 K. Effects of luminaire shape led to an increase (16%) of trapped insects for luminaires with diffusors compared to the standard shape. In addition, luminaires with diffusors amplified the effects of LED color (+12% insects at 1750 K/3000 K; +25.6% at 4000 K). In contrast, bat foraging activity was independent of the light treatments while bat feeding activity was increased by 21.5% at standard luminaire shapes. Likely, intense straylight at diffused lights negatively affects the target-focused echolocation by deterring the bats. We concluded that ecological impacts of luminaire shape are an important, yet underestimated variable in light-pollution impact research.

The Optical Design of a LED-Reflector Module in Road Illumination

In recent years, there has been a trend towards energy-efficient, long-lasting, environmentally friendly, and technology-compatible LED road luminaires. In this study, the optical design and analysis of the LED road luminaire model for the M1 and M2 illumination classes roads, which are the roads with the highest importance, have been carried out. In the research, the unique reflector design was made using SolidWorks 3D design software. XLamp CXA1520 LED light source by Cree company was preferred during the design. 21 LEDs were placed on the reflector at the ideal distance and LED luminaire model was created in LightTools illumination design software. A simulation study was performed for the LED luminaire model created on LightTools software and the distribution curve of luminous intensity was obtained. At the same time, the EULUMDAT (.ldt) file, which is required for road illumination analysis, was produced with LightTools software. The obtained .ldt file was transferred to DIALux illumination calculation program and simulated for M1 and M2 class roads. Illumination parameters obtained from DIALux analysis have been optimized by comparing them with the road illumination criteria accepted by International Commission on Illumination (CIE). It has been observed that the designed LED luminaire model significantly meets the M1 and M2 class road illumination criteria defined by CIE. In the study, it was also discussed what changes can be made in the optical material to meet all criteria.

Radiation Colour Non-Uniformity Accounting in the LED Luminaires Production and Operation

Applied aspects of accounting for the colour non-uniformity of the radiation of LED luminaries (LL), as their technical and operational characteristics, are considered. At the same time, the features of the perception of colour non-uniformity, created by LL in the observer’s field of view on the object, during their long-term operation at different radiation angles in space and on the surface, are shown. The need for a standard that regulates the methodology for assessing colour non-uniformity and the corresponding criteria is indicated. The necessity of including the colour non-uniformity of the radiation of LL in the list of controlled characteristics during the production and operation of these products is shown.

A Tunable LED Daylight Luminaire for Textile and Printing Light Booth Application with Optimum LEDs

Color quality testing in the light booth is one of the essential requirements of manufacturing industries. Due to conventional daylight simulators incompetence, there is a need for improvise of light sources used in these booths. Also, solid-state lighting advancements has given a breakthrough for provisioning a light source that is energy efficient, long life, tunable, providing stable and modifiable illuminance. This research work focusses on the optimal design of a polychromatic LED luminaire, mimicking D50, D65 and D75 daylight spectrum with CRI > 90 and average illuminance 2000 lx. A multi-objective algorithmic approach towards LED selection has publicized daylight simulations feasibility with seven emitter combinations of red–green-blue-amber-lime-white (5070 K and 6570 K). The proximity of chromaticity coordinates of the test lamp with reference illuminant ascertains the quality of the designed luminaire. Further, the test lamps spectral fit and illumination consistency in the light booth ensure its suitability for color quality testing chambers.

Comparison of energy efficiency and costs related to conventional and LED road lighting installations

Comparison of conventional (usually high-pressure sodium (HPS)) and LED luminaires in street/road lighting is not often based on photometrically equivalent lighting solutions and/or correct economic analysis, which may lead to either overestimation or underestimation of savings of any kind. Therefore, this paper presents a correct methodology for the determination of actual energy efficiency and cost indicators in street/road lighting. Both neutral white (NW) and warm white (WW) LEDs, all relevant street/road lighting classes and pole layouts were considered. Analyzing optimal lighting solutions, characterized by the lowest installed power, it was shown that when considering mesopic effects the average energy savings achieved comparing LED (NW and WW) with HPS lighting solutions amounted to 41–62% and 29–59%, respectively, while the ratio between the total costs of the comparable LED (NW and WW) and HPS lighting solutions belonged to the ranges 0.59–1.26 and 0.61–1.14, respectively. An expanded sensitivity analysis of the costs, carried out considering not only the usually taken discount and electricity cost rates, but also the LED package lifetime, showed that the last only slightly influences the total costs. The effects of the use of more efficient LED packages expected in the near future were also analyzed.

Environmental and social life cycle assessments of an industrial LED lighting product

It is necessary to assess a product's sustainability from both environmental and social perspectives. However, combined environmental and social performance assessments have not been given enough attention. This paper presents a combined Environmental Life Cycle Assessment (E-LCA) and Social Life Cycle Assessment (S-LCA) of an industrial LED luminaire through its life cycle. The LCA screening studies were conducted in line with ISO 14044 and United Nations Guidelines for E-LCA and S-LCA with Ecoinvent and PSILCA databases. The study analysed the key potential risks as well as the interrelation between E-LCA and S-LCA results, in which the production of LED driver, LED panel, and electricity consumption were identified as the hotspot processes to both environmental and social impacts. Four social issues were identified, namely ‘association and bargaining rights’, ‘sanitation coverage’, ‘public sector corruption’ and ‘pollution’. LED driver and panels are responsible for 78% and 20% of the environmental impacts respectively in the production phase. Electricity accounts for an average of 51% of environmental impacts. The process also made the key contribution to the ‘social responsibility along the supply chain’ (52%), ‘industrial water depletion’ (84%) and ‘contribution to environmental load’ (63%) risks. Meanwhile, in the category ‘contribution to economic development’, 18% positive social impacts were identified. Based on the results obtained, recommendations were derived for the development of sustainable LED lighting products and services with a trade-off between the environmental impact and the socio-economic benefits. According to the literature review, this research is the first attempt to assess a combined environmental and social performance in industrial LED lighting products and provides a valuable contribution to knowledge for future research in this area.

Multi-Channel LED Luminaires: An Object-Oriented Approach for Retail Lighting Based on the SOR Framework

In this paper, a method to find the optimum spectrum for the illumination of objects in a retail environment is presented. A variety of familiar objects are illuminated with a number of illuminants of a predefined Correlated Color Temperature (CCT) of 3000 K, strategically selected from the entire range of metamers, which can be generated by the multi-channel luminaire under test. The solution space has been derived by solving basic colorimetric equations using a brute force method. In a paired comparison experiment, observers had to select the most “attractive” appearance for the presented objects. The results illustrate that objects may indeed appear more attractive for a statistically meaningful number of observers under a particular lighting condition. Assuming attractiveness of an object as a stimulus in the SOR framework, this approach facilitates the generation and the selection of the “optimum” spectrum based on the goals of the stakeholders in retail lighting applications.

Beam controlled lighting design: An approach towards optimization of road lighting design

LED based street lighting has been introduced everywhere for energy saving aspect. The Optical Control of LED is very much possible with change of beam angles. This beam-angle based switching of LED based street lighting installations is a new area to be explored. Global research says LED is an energy saving light source. But during low or off traffic hours, portion of LED arrays of a luminaires may be switched on/off on the basis of beam-angle. The light level is reduced. The ‘beam-angle switching’definitely ensures energy saving, but the investigation of the human performance under this condition is also necessary. There is no such evidence available in favour of the effectiveness of ‘beam-angle switching’ on human performance. In this paper an experimentation based studies have been conducted to identify the driver’s response during the object detection under different lighting conditions as PRO, COUNTER and FULL GLOW of a LED luminaire. The visibility study has been carried out in a simulated road to prove the effectiveness of this beam-angle based switching from the human performance as well as energy saving point of view.

Artificial Skylight A Novel Photovoltaic Approach For Daylight Harvesting

Daylight harvesting is an apparent way of utilizing green energy in modern buildings which leads to sustainable development. In modern days, a huge amount of energy is consumed for lighting applications. So, in this article, we approached a novel photovoltaicbased daylighting system that can replicate the sunlight into an electric light inside a room. In general, this task is dependent on a photovoltaic cell and its maximum power point tracking for maximum energy conversion/extraction (daylight to electricity). So, we have developed a unique algorithm for this task which will lead to a maximum extraction of current based on the daylight condition outside. The MPPT algorithm is controlled by a microcontroller and the output light from the system is proportionate replication of the daylight available outside the room. The microcontroller controls the boost converter duty cycle for maximum power extraction. This article consists of detailed circuit diagrams and algorithm used for this whole system. This system is capable of lighting up a series of LED luminaires from a single photovoltaic cell.

The current state of energy efficiency and light quality of led products

The article presents the results of the energy efficiency study and light quality of LED illuminators (lamps) for general lighting, in particular colorimetric parameters, light flux modulation and photobiological safety. It is shown that two-base LED lamps with G13 base and luminaires for outdoor lighting have achieved energy efficiency class A++. LED lamps with E27 base and indoor lighting fixtures with light diffusers have a light output 25–35% lower and correspond to energy efficiency classes A+, A, B. Correlated color temperature (FTA) of indoor lighting fixtures is mainly in the range of 3000–4500 K, and the total color rendering index Ra – in the range of 71–86 units. The deviation of chromaticity from nominal values can reach 7+ degrees of McAdam ellipses (7+ standard deviations of SDCM comparison color). The angular non-uniformity of color in luminaires with diffuse light diffusers does not exceed 3 SDCM, and for luminaires without light diffusers and with lens optics - can exceed 7+ SDCM.
 It is shown that LED luminaires for indoor lighting have a mainly safe level of flicker and visibility of the stroboscopic effect. In the frequency range up to 80 Hz, the flicker level, which is observed with a probability of 50% lower than incandescent lamps with a power of 60 watts. In the frequency range up to 3000 Hz, the modulation depth corresponds to a level that does not create adverse biological effects.
 LED lamps and illuminators for general lighting entering the lighting market do not exceed the parameters of the insignificant risk danger group of blue light RG1. Lamps and illuminators using diffuse light diffusers belong to the general group RG0 (no risk).
 Conclusions are made on energy efficiency and light quality of LED lamps.

Proposing a Method Reducing UGR Calculations for LED Luminaires with Diffusers in Indoor Applications

This paper studies discomfort glare in indoor LED lighting systems and proposes a method reducing UGR calculations. There are several methods for expressing discomfort glare, among which the unified glare rating (UGR) method is one of the most popular. It is safe to indicate that the UGR method was introduced before LED lighting became popular in indoor applications. Thus, the UGR method is not versatile currently. In this paper, key limitations of the UGR method are discussed. A method for reducing UGR calculations based on UGR tables for both LED luminaires with diffusers (uniform luminous intensity distribution) and with lenses is proposed. The method is mathematically discussed and its applicability for luminaires is discussed. Also, the luminaires are put through a test and the results from the tests are presented and the feasibility of the method separately from mathematical proofs is examined. The proof and case studies both indicate that the method can be used accurately for luminaires with diffusers. They also illustrate that the accuracy of applying the proposed method to the LED luminaires with lenses is not satisfactory. Simulations are carried out using DIALux lighting design software.

Super powerful LED luminaires with a high color rendering index for lighting systems with combined electric power supply

Considered in this paper are development and creation of high-power LED luminaires with high light efficiency and color rendering index (CRI). As light sources, there used are 6 powerful LED СОВ (Chip-on-Board) modules CreeCXA 2550, the radiation of which contains quasi-chromatic peaks in the spectral range 600…650 nm. It allows to provide CRI values higher than 92. Features of the improved compact construction of the luminaire with indicated COB modules have been presented. To ensure normal thermal regimes of LED COB modules, a small cooling system based on heat pipes has been created, the optimal dimensions of the structural elements of which have been determined by computer simulation. The results of modeling and experimental studies have shown that the developed and manufactured passive cooling system of LED COB modules provides operation temperature modes (up to 85 °C) of light-emitting crystals at the total electric power of COB modules up to 290 W and allows using the luminaires of this type in the systems of continuous artificial illumination with combined power supply. The efficiency of the developed cooling system at some angles to the horizon expands the scope of applying the illumination device.

CALCULATION AND EXPERIMENTAL STUDIES OF THE LIGHTING TECHNICAL CHARACTERISTICS OF THE LED MODULE

The article describes the characteristics of LED modules made using the Chip-on-Board technology. An overview of LED modules from different manufacturers is carried out. Variants of using differently oriented mounting of flat mirror surfaces and their influence on the lighting characteristics of LED modules have been investigated. Theoretical research and modeling of the LED module and differently oriented mirror surfaces in the TracePro software package have been carried out. The development of universal LED luminaires is one of the urgent tasks of lighting engineering. The market for LED light sources is rapidly improving, more efficient sources appear, therefore the creation of modern lamps based on various optical systems is a popular direction in the development of electronics. Secondary optics options for the COB module and simulation results in TracePro are presented.

Computer Vision-Based Localization With Visible Light Communications

Visible light positioning and computer vision-based localization have the potential to be cost-effective technologies for accurate indoor localization. However, the feasibility of existing methods in this domain is limited. In this paper, a novel visible light communication (VLC)-assisted perspective-four-line algorithm (V-P4L) is proposed for practical indoor localization. The basic idea of V-P4L is to jointly use VLC and computer vision techniques to achieve high localization accuracy regardless of LED height differences. In particular, the space-domain information is first exploited to estimate the orientation and coordinate information of a single rectangular LED luminaire in the camera coordinate system based on plane geometry theory and solid geometry theory. Then, by using time-domain information transmitted by VLC and the estimated luminaire information, the proposed V-P4L can estimate the position and pose of the camera using single-view geometry theory and the linear least square (LLS) method. To further mitigate the effect of height differences among LEDs on localization accuracy, a correction algorithm based on the LLS method and a simple optimization method is proposed. Due to the combination of time- and space-domain information, V-P4L can achieve accurate localization using a single luminaire without limitation on the correspondences between the features and their projections in conventional perspective-n-line (PnL) algorithms. Simulation results show that the position error caused by the proposed V-P4L algorithm is always less than 15 cm and the orientation error is always less than 4° using popular indoor luminaires. Experimental results with real hardware show that the average position error is less than 3 cm under both similar and different heights for the LEDs.