Okra (Abelmoschus esculentus) is a major vegetable crop whose year-round production can be enhanced under controlled environments with artificial lighting. Achieving a uniform photosynthetic photon flux density (PPFD) is critical to optimize plant growth and reduce variability in morphological and physiological responses. Although many studies have focused on optimizing LED fixture designs prior to fabrication, few have validated simulation methods using existing commercial LED modules. This study evaluates and optimizes PPFD distribution using commercial LED modules. A multi-objective genetic algorithm coupled with an analytical model was developed to determine the optimal module spacing (D) and mounting height (h) needed to reach a target average PPFD of 200 & micro;mol & centerdot;m(-2)& centerdot;s(-1) with at least 60% uniformity for two LED fixtures emitting at 660 nm (red) and 445 nm (blue). Simulated and measured PPFD distributions showed strong agreement, with relative errors ranging from 2.0% to 4.1%, well within acceptable limits for photometric modeling. These results demonstrate the robustness and generalizability of the proposed framework for predicting and optimizing PPFD distribution in horticultural lighting, providing a reliable tool to improve indoor cultivation of okra and other crops.

The IEC flicker observer model, or light flickermeter, is an algorithm whose purpose is to assess the severity of flicker produced by artificial lighting. Historically, it was developed by extraction from the voltage flickermeter, and it is thus based on experiments with incandescent lamps. This paper is one in a series of papers focused on verifying the light flickermeter performance for LED light sources. Flicker perceptibility (visibility) and irritability thresholds are measured in conditions taking into account peripheral vision. A new flicker irritability threshold measurement procedure is presented. The data are then compared to the thresholds indicated by the light flickermeter. The paper presents a detailed and complete verification of the flickermeter thresholds both in terms of the flicker severity measure (Pst) as well instantaneous flicker (Pinst) and brings a comprehensive understanding of what these two quantities actually represent.

This paper proposes a photometrically consistent real-time rendering pipeline for digital twins of street lighting systems, designed to bridge the gap between offline lighting simulation tools and interactive visualization environments. The approach integrates high-resolution illuminance data generated by Relux and DIALux into a real-time graphics engine, with the objective of preserving photometric fidelity while maintaining interactive performance. The proposed framework is demonstrated on a campus road section through a street lighting digital twin implemented in Unity. A modular rendering pipeline is introduced, including photometric data preprocessing, illuminance-grid interpolation, texture generation, and consistency checks between offline simulations and real-time outputs. Three real-time lighting modes are implemented and evaluated: an analytical cone-based spotlight model, a texture-masked cookie spotlight mode, and a full-resolution photometric sampling approach based on Unity's universal Render Pipeline (URP) Shader Graph. A static validation between Relux and DIALux confirms consistent photometric inputs, with mean absolute errors below 5%. Evaluation results show that richer photometric sampling improves agreement with the Relux reference: the Shader Graph mode achieves the best in-engine luxmeter validation (root mean square error (RMSE) 3.82 lx, Pearson correlation (Corr) 0.705) while sustaining real-time performance at approximately 140 frames per second (FPS). Overall, the proposed pipeline enables aligned and interactive street lighting digital twins suitable for simulation-driven visualization and evaluation.

The widespread use of domestic LED lamps raises concerns about harmonic current aggregation when multiple units operate in parallel. This study presents a regression-based method for predicting aggregate current waveforms of identical LED lamps. Measurements conducted in accordance with IEC 61000-4-30:2015 involved 1–24 parallel-connected units of a 12 W lamp under controlled conditions. Individual harmonics through the 40th order were assessed against IEC 61000-3-2 product limits, while components up to the 50th order were retained for PCC-oriented characterization of large-scale aggregation, consistent with IEEE 519-2022. Although the product limits were satisfied, measured THDI remained at 88.6–92%, dominated by the 3rd, 5th, and 7th harmonics. Within the measured range, per-harmonic regressions were evaluated using R2 and RMSE, while reconstructed time-domain waveforms produced NRMSE values of 5–10% relative to measured RMS current. Consistent phase angles indicated predominantly constructive aggregation. The model was then applied to an illustrative scenario of up to 100 identical lamps. Under unchanged lamp and supply conditions, the projection indicated a near-linear increase in RMS current, persistent THDI of approximately 90%, and continued dominance of low-order odd harmonics. Results beyond 24 lamps represent model-based extrapolation rather than experimental validation. The framework provides a baseline for harmonic current assessment in homogeneous LED installations.

In high-power lighting applications such as stadium or airport lighting, cooling is even more necessary when used in hot climates. Poor thermal management impacts their energy efficiency, but more importantly, their lifespan and reliability. Natural convection cooling has its limitations due to the weight and bulk of the heat sinks, making it necessary to develop active heat sinks. This work presents a comparative study conducted on two active cooling methods applied to a high-power LED lamp: forced convection using fans and ionic wind cooling. For each technique, energy consumption and efficiency were measured, analyzed, and compared under similar conditions and for the same thermal performance. The strengths and limitations of both methods applied to cooling LED lighting systems are also presented.

Light just seems ”natural” to us, as well as lighting when the ambient level is too low for our needs. This paper is about the Physic and Technologies behind light and lighting, together with a brief description of the Human perception mechanisms. It goes over norms and measurement systems, and summarizes a few of the influences of lighting on Humans, but also on Biotope.

This article presents an analysis of the degradation of high-power light-emitting diode (LED) modules used to grow okra indoors. Three growth chambers containing three LED lights with four LED modules were used to grow four okra plants each, with a blue-only treatment (B4), a red-only treatment (R4) and two reds and two blues alternating in a cycle every three days (R2B2). At the end of the experiment, we carried out the study on the experimental characterization of commercial red and blue LED modules from the same product range and manufacturer. In this work, we report that the use of red LED (660 nm) in culture causes a decrease in optical power (OP) and a variation in the spectrum emitted compared with the blue LED (445 nm), which was unaffected. We also describe a higher fixture growth efficiency (FGE) under (R4), followed by (R2B2) and (R4). These results show that blue LEDs are more efficient for biomass production and undergo less degradation.

Digital twins promise to revolutionize street lighting by combining high-fidelity simulations with interactive visualization. In this paper, we present a modular real-time rendering pipeline for street lighting digital twins, applied on a university campus. We export high-resolution illuminance maps from the lighting-simulation software Relux, then preprocess and stream them into Unity’s Universal Render Pipeline (URP). We implement and compare three lighting modes: 1) analytical “cone” spotlights as a simple baseline; 2) texture-masked “cookie” spotlights for additional spatial detail; and 3) a custom Shader Graph that samples full-resolution illuminance maps for photometric accuracy. Our results show that static simulation accuracy is preserved while interactive performance is maintained, despite challenges in data preprocessing, shader integration, and runtime optimization. By bridging offline simulation and real-time rendering, our workflow lays the foundation for fully interactive virtual reality applications in street lighting.

Okra (Abelmoschus esculentus) is a tropical vegetable with high nutritional and economic value. Rich in fiber, vitamins (C, K, and B9), and minerals (magnesium, potassium, calcium, and iron), it contributes to food security in many tropical regions. Global production is estimated at 11.5 million tons in 2023, 62% of which will come from India. Nigeria, Mali, Sudan, Pakistan, and Côte d’Ivoire are also among the major producers. Given its economic importance, optimizing its growth through controlled methods such as greenhouse cultivation and light-emitting diode (LED) lighting is a strategic challenge. Energy-efficient LED horticultural lighting offers promising prospects, but each plant variety reacts differently depending on the light spectrum, intensity, and duration of exposure (photoperiod). This study evaluated the effects of different LED spectra on okra’s flowering after 30 days of growth using B (blue, 445 nm) and R (red, 660 nm) LED lights and red-blue alternating in a three-day cycle (R3B3) by alternating the photoperiod from 14 to 10 h. Outdoor and greenhouse conditions served as controls. The results show that the R3B3 treatment improves germination in terms of both speed and percentage. However, plant growth (height, stem diameter, and leaf area) remains higher in the control group. R3B3 and red light stimulate leaf and node development. Flowering occurs earlier in the control group (51 days) and later under LED, particularly blue (73 days). Fruit diameter after petal fall was also larger in the control group. These results confirm the sensitivity of okra to photoperiod and light quality, and highlight the potential of spectral and photoperiod manipulation to regulate flowering in controlled-environment agriculture.

Street lighting digital twins (DTs) promise interactive optimization of urban illumination. This paper evaluates the photometric fidelity of a Unity-based DT by cross-checking Relux and DIALux simulations against perceptually relevant, in-situ HDR measurements. First, we implement an in-engine virtual luxmeter in Unity URP to sample and validate Relux-generated illuminance maps. We then validate the digital twin at two complementary levels: (i) a quantitative illuminance validation against Relux simulations using MAE and RMSE, and (ii) a perceptual comparison with in-situ HDR luminance measurements reported in the literature. The results demonstrate that real-time rendering engines, when combined with measurement-oriented sampling and calibration, can support validation-oriented digital twins rather than purely visual representations.

This work presents a digital twin approach of the thermal modelling of LED lamps; the objective is to improve the energy efficiency and the real time monitoring. The model of the LED lamps is developed using COMSOL Multiphysics to simulate the junction temperature and the heat dissipation under different external conditions. For the real time monitoring, we will use a raspberry pi along with a temperature sensor and a light sensor to continuously track the external parameters through a MQTT platform and update our model in real time. The real time simulated junction temperature is then displayed on a Home Automation System dashboard.

The IEC flicker observer model, or light flickermeter, is an algorithm whose purpose is to assess the severity of flicker produced by artificial lighting. Historically, it was developed by extraction from the voltage flickermeter, and it is thus based on experiments with incandescent lamps. This paper is one in a series of papers focused on verifying the light flickermeter performance for LED light sources. Flicker visibility threshold is measured in conditions taking into account peripheral vision. The data are then compared to the thresholds indicated by the light flickermeter.

LEDs are widely used and cover all possible applications of artificial lighting, both for low power in domestic lighting and for very high power such as stadium or airport lighting. In the case of high-power lighting, thermal management is a crucial element because it seriously affects energy efficiency but above all the life of the light source. Several cooling techniques exist (heat pipe, fan, etc.) but the use of ionic winds for cooling LEDs has many interesting advantages (no moving mechanical parts, high energy efficiency, etc.). This study provides a numerical analysis of this innovative cooling technology using ionic wind, by comparing two possible configurations: point-to-plane and line or wire-to-plane. The results present the cooling efficiencies associated with the two cases studied.

An analytical method for evaluating the photosynthetic photon flux density (PPFD) distribution was developed using relationships between the quantities and units of electromagnetic radiation used in radiometry and photometry for horticultural lighting. We have adapted our settings specifically for growing okra under artificial lighting. We proposed a realistic analytical method to determine the number of LEDs needed, based on the desired PPFD. Firstly, the emission wavelengths and the radiant flux value of the LED modules suitable for growing Okra were determined by modeling the ideal spectrum. Then, considering each LED as an imperfect Lambertian emitter, the PPFD distribution was calculated from the photosynthetic photon intensity distribution (PPID) curves. Finally, the simulation is carried out using MATLAB software. The results show that the uniformity of the PPFD is significantly affected by the spacing D between the LED modules and the height of the luminaire relative to the work surface. The analysis method presented here can be usefully applied in the design of LED lighting for horticulture to other similar crops.

LED lighting occupies all sectors including high power ones. The most efficient systems today reach nearly 30% and it is necessary to evacuate the 70% of thermal losses to protect the LEDs and allow them to have a long life. Among the alternatives to natural convection cooling, two main forced convection modes are presented: by fan or by ionic wind. This work presents a comparative study of the thermal performances of three cooling methods applied to an LED heat sink: natural convection, ionic wind cooling and forced convection using a fan. Experiments were conducted at different LED power levels, using Schlieren imaging to visualize thermal flows and MATLAB for thermal image analysis. The results show that while the fan offers the best thermal performances, the ionic wind stands out for its quiet operation and compact design. This study highlights the importance of selecting the appropriate cooling method based on the specific requirements of each application.

The co-integration of antennas with lighting sources appears as an effective way to distribute broadband networks closer to users, lowering interference and transmitted power, as well as to reduce energy consumption in future lighting systems. We here present an original contribution to the implementation of transparent and invisible antennas with OLED light sources. To validate the proposed approach, the honeycomb mesh technique was used, and an optical transparency of 75.4% was reached. The transparent mesh antenna was compared with the non-transparent full-metal antenna in terms of radio-electrical parameters. Our prototype was designed using copper films deposited on a glass substrate. The simulation results of the S-parameters and the radiation patterns were validated against measurements performed in an anechoic chamber. The directivity and gain obtained were 6.67 dBi and 4.86 dBi at 5.16GHz, respectively. To study the effect of antenna integration with OLEDs, optical and photometric characterizations with and without the antenna were measured, and the colorimetric parameters were then treated using the IES TM-30-18 standard.

The properties of a mix of spectra, like typically produced by the association of colored LEDs, are described by a few indicators taking into account the Human visual perception. Smart lighting systems will f.i. offer control in terms of level (illumination) and Correlated Color Temperature. This paper is about illustrating the various relationships between those indicators for a mix of red, green, and blue LEDs. It also emphasizes on implementing the optimization procedure to maximize the lamp utility and checking the validity of the computed operating points. The influence of a few degrees of freedom will also be evaluated numerically.

Light pollution, a growing ecological concern, significantly impacts moths, which are crucial for pollination and biodiversity. This study compares artificial and natural light using the Daylight Similarity Index (DSI) and Moonlight Similarity Index (MSI). Spectral data from LED lamps and natural sources were weighted by the visual responses of three moth species. Maximum similarity was found at Correlated Color Temperature (CCT) between 3000–4000 K, which could be perceived as the most similar to natural light by insects. The findings suggest visual perception mechanisms are related to family rather than lifestyle, recommending further research with UV-inclusive light and other light characteristics.

This paper investigates the feasibility of non-battery energy storage systems for isolated street lighting, focusing on mechanical storage technologies such as gravity storage, compressed air energy storage, and flywheels. As the global shift toward renewable energy accelerates, the challenge of intermittency in sources like solar and wind becomes increasingly significant. Traditional batteries, while widely used, present limitations in cost, lifespan, and environmental impact. Mechanical storage systems offer promising alternatives, with potential for greater sustainability and efficiency. Through a detailed analysis and comparison of investment costs, this study evaluates the practicality and effectiveness of these non-battery solutions in providing reliable energy storage for a sustainable future.

In 2019, Indonesia’s electricity consumption exceeded 278 TWH, or about 1.08 MWh/capita. This value shows a considerable increase in electricity consumption which has doubled in just a decade. Previous studies have shown that the proportion of electricity consumption used for lighting needs is correlated to the country’s GDP. This is generally around 20 to 50% of electricity production but can go up to 86% in the case of Tanzania. Indonesia is the 4th country in the world in terms of population and its lighting market as well as its lighting-related energy consumption has a strong impact on several levels: societal, environmental but also economic and energy. Having a knowledge of the lamps used by the Indonesian people is therefore particularly interesting and important, in particular in the context which presents a great societal diversity but also in a context of energy saving. Indonesia is an archipelagic country made up of 5 large islands and over 17,000 small islands with widely varying levels of population density. This island geography leads Indonesia to face challenges in the distribution and production of electrical energy, which affects the use of lamps in various types of regions. The overview of this study was done by collecting data from various sources, especially BPS (Biro Pusat Statistik/Statistic Center Bureau of Indonesia), CLASP (an NGO for clean energy), the Ministry of Energy and Mineral Resources of Indonesia (ESDM), PLN (Indonesian Electrical Company), etc. The data obtained from these sources provides several descriptions of general lighting conditions in Indonesia viewed from several angles, such as growth of lamp market, use of lamp types, percentage of use of lamps with energy saving (ESL), etc. Considering that Indonesia has various regional characteristics, in this study, the survey of a total of 394 respondents was conducted on the use of lamps by creating regional categories based on electrical conditions, power consumption, and electricity per capita, among others. The categories of areas observed fall into 5 types based on their population and geography: large cities, small towns, rural/village areas, islands and remote areas. The results of compiling data from these various sources show that the types of lamps used by Indonesians follow the lighting trend in the world. The use of LED lamps has a utilization percentage of around 52%, much higher than other types of lamps such as CFL, fluorescent or incandescent. Based on the survey conducted, it is known that the widely used LED power is between 1 and 10 watts with a usage time of 8 to 12 h per day. In the next few years, it is estimated that the use of LEDs in Indonesia will increase as the government has prepared various regulations and policies related to energy saving, one of which relates to lighting.