Light-emitting Diode Lighting Systems Research Articles

Advanced Design and Characterization of a Flat Panel Photobioreactor Equipped with a Customizable Light-Emitting Diode Lighting System

Advanced Design and Characterization of a Flat Panel Photobioreactor Equipped with a Customizable Light-Emitting Diode Lighting System

Application timing and duration of LED and HPS supplements differentially influence yield, nutrient bioaccumulation, and light use efficiency of greenhouse basil across seasons.

Three primary factors that impact plant growth and development are light quantity, quality, and duration. Commercial growers can manipulate these parameters using light-emitting diodes (LEDs) to optimize biomass yield and plant quality. There is significant potential to synergize supplemental lighting (SL) parameters with seasonal variation of ambient sunlight to optimize crop light use efficiency (LUE), which could increase biomass while reducing SL electricity costs. To determine the best lighting characteristics and durations for different crops, particularly for enhancing the yield and nutritional quality of high-value specialty crops produced in greenhouses during the winter, a thorough efficacy comparison of progressive incremental daily light integrals (DLIs) using LED and high-pressure sodium (HPS) sources is required. The purpose of this study was to compare the effects of differential application timing and DLIs of supplemental blue (B)/red (R) narrowband wavelengths from LED lighting systems and HPS lamps on greenhouse hydroponic basil (Ocimum basilicum var. 'Genovese') production. We assessed edible biomass, nutrient bioaccumulation, and LUE. Nine light treatments included: one non-supplemented natural light (NL) control, two end-of-day (EOD) HPS treatments applied for 6h and 12h, five EOD 20B/80R LED treatments applied for 3h, 6h, 9h, 12h, 18h, and one continuous LED treatment (24h). Each SL treatment provided 100 µmol·m-2·s-1. The DLI of the NL control averaged 9.9mol·m-2·d-1 during the growth period (ranging from 4 to 20mol·m-2·d-1). SL treatments and growing seasons significantly impacted biomass and nutrient bioaccumulation; some SL treatments had lower yields than the non-supplemented NL control. January growing season produced the lowest fresh mass (FM) and dry mass (DM) values compared to November, which had the highest. Mineral analyses revealed that both growing seasons and lighting types impacted macro and micronutrient accumulation. Additionally, the efficiency of each treatment in converting electrical energy into biomass varied greatly. EOD supplements using LED and HPS lighting systems both have merits for efficiently optimizing yield and nutrient accumulation in basil; however, biomass and nutrient tissue concentrations highly depend on seasonal variation in ambient sunlight in conjunction with a supplement's spectral quality, DLI, and application schedule.

Visual and melanopic performance of a tropical daylight-mimicking lighting: a case study in Thailand

This paper designed and developed a tropical daylight-mimicking lighting system based on photometric, radiometric and International Commission on Illumination (CIE) standard melanopic performances from natural lighting cycles in Thailand. Spectral power distribution (SPD) during daylight in summer and winter were recorded to create a dynamic artificial lighting system that best matches the natural daylight characteristics. Two set-ups light emitting diode (LED) (LED-A and LED-B) were screened, developed, validated and compared with different chromaticity layouts of the correlated color temperatures (CCTs) allocated on Planckian locus and later converted to x-y co-ordinates in a chromaticity diagram. Based on CCT and Duv deviations between two developed setups, LED-A could mimick circadian points on the chromaticity diagram better than LED-B did. CCT and Duv values of LED-A (dCCT=3.75% and dDuv=17.36%) can match closer to the daylight than those of LED-B (<span lang="EN-US">d</span>CCT=5.0 % and <span lang="EN-US">d</span>Duv=56.84%). For CIE-standard melanopic performances (melanopic efficacy of luminous radiation (mELR), melanopic equivalent daylight (D65) illuminance (mEDI) and melanopic daylight efficacy ratio (mDER)), LED-A is suitable to use indoor with averages of 1.16 W×lm-1, 236 lx and 0.84, respectively, while LED-B is good to use outdoor with averages of 1.53 W×lm<sup>-1</sup>, 266 lx and 1.06, respectively. The proposed design can be used as a guideline to establish a daylight-mimicking LED lighting system from actual measurement data.

Research Control Devices for LED Light Sources under Their Operating Conditions at Elevated Temperatures

The electrical and light characteristics of light-emitting diodes (LEDs), upon which modern lighting devices are constructed, are significantly influenced by ambient temperature. As the temperature rises, the luminous flux of LEDs diminishes, and the lifespan of LED devices also decreases. The control devices (drivers) used in LED lighting systems, built based on current stabilization schemes, do not effectively stabilize the luminous flux when the ambient temperature fluctuates between +15 to +60 °C. The luminous flux declines as the temperature increases, even if the current supplied to the LEDs remains constant. This paper presents a comparative analysis of LED lighting devices equipped with drivers featuring current stabilization and those with drivers employing voltage stabilization for operation in higher temperature conditions.

Impact of Information on Attitudes Regarding Greenhouse Lighting Externality Regulation

AbstractAs food producers face increasing costs, many greenhouse growers are turning to controlled environment agriculture. The use of light-emitting diode (LED) supplemental lighting systems may increase a producer’s profitability, but it also comes with a unique set of externalities. Using an online survey, we found that showing images of light pollution from supplemental LED lighting sources facilitated respondents to want more regulation with state government being the desired regulator. Several significant factors influenced survey respondents’ posttreatment preference outcomes for different levels of regulation and regulators including demographic characteristics as well as initial attitudes toward LED lighting systems before treatment.

Design of multi-spectral LED lighting system with high color uniformity for microscopic imaging

Multi-spectral imaging is commonly used in biomedical field to detect and recognize targets, which are in a low contrast with their background. Highly integrated multichannel light-emitting diode (LED) devices enable tuning the spectral contents of the illumination in an accurate and compact fashion, and hence make multi-spectral lighting more easily achievable even in a microscope. Besides the light source, the light mixing system is also a key to realize it. Existing light mixing devices available for multi-spectral LED lighting systems are both costly to manufacture and intricate in design, making them a challenging solution to create. This work proposes a design of multi-spectral lighting system for microscopic imaging, which can achieve a high uniformity in the effective area of illumination in terms of both the illuminance and chromaticity. Simulation results first demonstrate that the designed lighting system consisting of two rods, both containing a frosted emitting surface, managed to reduce the non-uniformity to less than 0.05 for both the illuminance and chromaticity. Experiments with a real prototype show highly uniformly illuminated microscopic images of tissue section samples. Moreover, the pathogenic fungi in the infected tissue section samples can be highlighted by the superposition of multi-spectral images. These experimental results indicate that the designed multi-spectral LED lighting system can improve the quality of microscopic imaging in terms of the illumination and image contrast.

Modeling on Monolithic Integration Structure of AlGaN/InGaN/GaN High Electron Mobility Transistors and LEDs: 2DEG Density and Radiative Recombination

The monolithic integration structure of the AlGaN/InGaN/GaN−based high electron mobility transistor (HEMT) and light−emitting diode (LED) is attractive in LED lighting and visible light communication (VLC) systems owing to the reduction in parasitic elements by removing metal interconnections. Due to the band−offset and polarization effect, inserting a certain thickness in the InGaN layer into the traditional AlGaN/GaN single heterostructure increases the density of 2DEG to nearly twice the original. At the same time, inserting the InGaN quantum well layer can also improve the luminous efficiency of LED. In this paper, the physical models of two−dimensional electron gas (2DEG) densities and the threshold voltage of AlGaN/InGaN/GaN HEMTs are established and verified with experimental results from the literature. According to the calculation results, the two−dimensional electron gas (2DEG) density in the AlGaN/InGaN/GaN HEMT is 1.47 × 1013 cm−2, and the two−dimensional hole gas (2DHG) density is 0.55 × 1013 cm−2, when Al% = 0.2, In% = 0.1, dAlGaN = 20 nm. In addition, a physical model for the radiative recombination rate in the monolithic integration structure of HEMT−LED is proposed. This work provides a design guideline for AlGaN/InGaN/GaN HEMT and its application in visible light communication systems.

LED Systems Applications and LED Driver Topologies: A Review

High-power light-emitting diodes (LEDs) and high-brightness LEDs have revolutionized the lighting industry. The availability of cost-effective LEDs with high luminous flux, efficacy, and reliability has expanded their application to replace incandescent and fluorescent light sources. They have also enabled many new applications that were considered infeasible before, due to the inherent limitations of traditional sources of light. This survey provides a comprehensive overview of ac- and dc-supplied LED lighting systems and their applications, corresponding specifications and their similarities to/differences from regular power supplies. Restrictions imposed by LEDs characteristics, safety considerations, and dimmers are discussed. Also, LED driving approaches are categorized and their suitability for different applications is provided.

Portable and low-cost hologram verification module using a snapshot-based hyperspectral imaging algorithm

One of the challenges in differentiating a duplicate hologram from an original one is reflectivity. A slight change in lighting condition will completely change the reflection pattern exhibited by a hologram, and consequently, a standardized duplicate hologram detector has not yet been created. In this study, a portable and low-cost snapshot hyperspectral imaging (HSI) algorithm-based housing module for differentiating between original and duplicate holograms was proposed. The module consisted of a Raspberry Pi 4 processor, a Raspberry Pi camera, a display, and a light-emitting diode lighting system with a dimmer. A visible HSI algorithm that could convert an RGB image captured by the Raspberry Pi camera into a hyperspectral image was established. A specific region of interest was selected from the spectral image and mean gray value (MGV) and reflectivity were measured. Results suggested that shorter wavelengths are the most suitable for differentiating holograms when using MGV as the parameter for classification, while longer wavelengths are the most suitable when using reflectivity. The key features of this design include low cost, simplicity, lack of moving parts, and no requirement for an additional decoding key.

Integrated PV–BESS-Fed High Gain Converter for an LED Lighting System in a Commercial Building

The demand for electricity is rapidly growing and renewable energy sources such as solar, wind and tidal energy can compensate the demand to a substantial level. Among these, solar energy is abundant, scalable and is cheaper. The generated energy can be used in an efficient way if the DC output is directly supplied to the load instead of converting it to AC. Every electrical system is capable of operating in DC and, for example, energy efficient Light Emitting Diode (LED) lights have become popular as they provides more lumens with less power consumption and also can be directly operated from DC. LED lighting system in large commercial buildings has irradiance levels which vary sigificantly during operation. Extracting maximum power from the energy system and maintaining constant voltage output at different loads is another challenge. This paper proposes a solar Photo Voltaic (PV)-based energy system including Battery Energy Storage System (BESS) for supplying LED lamps to a commercial building through a modified high gain Luo converter. The Perturb and Observe control algorithm has been used for maximum power extraction from a PV cell whereas PI (Proportional Integral) controllers maintain constant output voltage from PV–BESS against different irradiance levels. To supply the desired voltages to the LED lighting system, a modified high gain Luo converter is designed. To make the output voltage constant at different load currents, PI and Sliding Mode Controllers (SMC) are designed with the help of the state-space average model. It is found that the sliding mode controller outperforms the PI controller in terms of behavior in the transient period and tracking capability. The system is simulated using MATLAB/Simulink®. The Sliding Mode Controller has a 95% less transient period and is 75% faster in tracking capability when compared to other controllers. The system could be incorporated with the PV source to obtain green energy.

Effect of LED lights on the in vitro growth of Pinus pseudostrobus Lindl., plants

Pinus pseudostrobus Lindl. is a species endemic to Mexico and is widely used in reforestation programmes, as it is highly adapted to poor, shallow, limestone soils and has high commercial importance. However, it is necessary to preserve this genetic material since it is in trouble due to high rates of deforestation, land use change, and forest fires, so it is necessary to have effective strategies to obtain good quality seedlings. Due to the properties of LED (light emitting diode) lamps used for illumination in the production of in vitro plants, the effects of two different lighting systems (LED and fluorescent) on an in vitro culture were analysed for the morphological characteristics of the growth and photosynthetic pigment content in P. pseudostrobus seedlings. The length and root size of the seedlings were affected by the type of illumination, where a red LED light was the most effective at 30 days of evaluation. However, a blue LED light was equally effective as a red LED light at 60 days of seedling development. On the other hand, the fluorescent light was better in terms of the number of needles in the first stage, but we found the blue LED light to be better in the second stage. For the photosynthetic pigment content, the highest values were found with the blue LED light. The results showed that the LED lighting system favours the growth, development, and photosynthetic pigment content of the species under study.

Thermal performance investigation of position function circuit board used in automotive exterior rear lighting

In this research, both numerically and experimentally, the thermal efficiency of a Printed Circuit Board (PCB) with two Light Emitting Diode (LED) chips was examined. The two LED lighting systems, which are single-cell LEDs, including PCB and copper plates, were manufactured, and tested under laboratory conditions to achieve this goal. The three-dimensional Computational Fluid Dynamics (CFD) model with natural convection effects prepared using the FloEFD software package to predict PCB surface temperature distributions. The goal was to perform comprehensive circuit board simulation and validate the numerical model built in this study using the experimental data during the studies. From the results, we can easily claim that higher temperature gradients are calculated and predicted near the LED chip because of heat generation. Data paths have played an essential role in the LED circuit board's temperature distribution. High-temperature variations are observed at short distances around the LED when the experimental and simulation results are compared. Temperature changes are minimized as they travel away from the LED chip. It is found that the error rate is below 5 percent overall between the experimental and simulation results. The numerical results were in proper alignment with numerical data obtained from the three-dimensional (3D) CFD model. Given thermal efficiency and using such models, this model can design and analyze Automotive Lighting Systems.

On-Line Diagnostics of Electrolytic Capacitors in Fault-Tolerant LED Lighting Systems

As technology advances, the utilization of lighting systems based on light-emitting diode (LED) technology is becoming increasingly essential, given its benefits in terms of efficiency, reliability, and lifespan. Unfortunately, the power electronic components required to drive LEDs are unable to compete with LED devices in terms of lifetime. Aluminum electrolytic capacitor (AEC) failures represent the root cause of power electronic equipment breakdown, mainly through both aging and temperature effects. This highlights the importance of designing robust power converter architectures and control methods that allow the evaluation of the condition of electrolytic capacitors while maintaining the performance of converter controllers, even in the presence of capacitor failure. On this basis, this work proposes a novel condition-monitoring system for the diagnosis of capacitor faults on a fault-tolerant LED driver, which is able to deal with the specific architecture and low ratings of the most recent LED lighting systems. The fault-detection task applies the short time least square Prony’s (STLSP) approach to perform an online estimation of the ESR and C parameters, allowing the continuous evaluation of the electrolytic capacitor’s condition and, as a result, the prevention of total system failure. With regard to capacitor failure, the experimental results suggest that the condition-monitoring task is extremely effective, even when considering a limited number of data samples.

A Multi-Analytical Approach for Studying the Effect of New LED Lighting Systems on Modern Paints: Chemical Stability Investigations.

This study aims to investigate the chemical stability of some modern paint samples exposed to a new Light Emitting Diode (LED)-lighting system and a halogen lamp by using micro-attenuated total reflectance of Fourier transform infrared spectroscopy (µ-ATR-FTIR), µ-Raman, pyrolysis—gas chromatography/mass spectrometry (Py-GC/MS), and thermally assisted hydrolysis and methylation of GC/MS (THM-GC/MS). Those investigations were performed before and after the exposure of the samples to lightings for 1250, 2400, 3300, and 5000 h. The results obtained with µ-Raman spectroscopy show the high stability of the selected inorganic pigments after the exposure to the lighting systems; while similar to the UV/Vis/NIR results reported in a previous study, µ-ATR-FTIR and THM-GC/MS results evidence greater chemical changes occurring principally on the linseed oil binder-based mock-ups among the acrylic and alkyd-based samples. Moreover, principal component analyses (PCA) and hierarchical cluster analyses (HCA) of THM-GC/MS results highlight that those changes were mostly dependent on the exposure time and on the type of pigment, while being independent of the lighting system used. Finally, semi-quantitative µ-ATR-FTIR results show slight pigment enrichment at the paint surface due to the auto and photo-oxidative degradation of the linseed oil binder.

Thermal conduction characteristics of silicone composites including ultrasonic-treated graphite

The microstructural change of graphite was studied after ultrasonic treatment of the graphite. When the graphite solution was treated with varying ultrasonic power and time, the microstructure changed gradually, and accordingly, the thermal conductivity characteristics of the composite containing the as-treated graphite was also different with each other. Thermal conductivity showed the best result in the silicone composite containing graphite prepared under the optimum condition of ultrasonic treatment, and the thermal conductivity of the composite improved proportionally along with the particle size of graphite. When the silicone composite was prepared by using a mixture of inorganic oxides and graphite rather than graphite alone, the thermal conductivity of the silicone composite was further increased. A silicone composite containing graphite was used for LED (light emitting diode) lighting system as a thermal interface material (TIM), and the temperature elevation due to heat generated, while the lighting was actually operated, was analyzed.

The effect of new LED lighting systems on the colour of modern paints

This research focuses on the investigation of the effect of a new light emitting diode (LED)-lighting system which reproduces indoor museum conditions, on some self-made art paint colours (acrylic-, alkyd-, and linseed oil-based paints) often used in modern-contemporary art. A halogen lamp representing a traditional light source for museum lighting was also considered. Lighting-set-up and lighting optimization parameters were considered while Ultraviolet/Visible/Near Infrared (UV/Vis/NIR) spectrophotometry was used for investigating the colour change of the paint samples. Univariate analyses allowed determining the highest effect of the lighting systems on the linseed oil binder and ultramarine blue PB29 mixture upon ageing, according to the highest total colour change ΔE*ab. In a more specific and detailed way, variance analyses not only demonstrated the strong correlation between the type of binder and pigment used for the paint samples with the colour variation, but also showed that the short-wavelength blue LEDs influenced the change along the yellow–blue b* axis of the yellow and blue samples, whereas the halogen lamp mostly had an impact towards the red–green a* axis of mostly the green specimens.

Influence of the Advancement in the LED Lighting Technologies on the Optimum Windows-to-Wall Ratio of Jordanians Residential Buildings

Based on recent developments and the predicted future advancement of lighting technologies, researchers are now questioning the extent to which daylight is effective in lowering the overall energy consumption of buildings. As light-emitting diode (LED) luminaires are highly energy efficient, the amount of power consumed for lighting purposes can be reduced, even in situations where the lighting system is at its full power. It has already been demonstrated that LED-lighting technologies can facilitate significant energy savings through minimizing window size (the main source of heat loss in buildings), and there is considerable potential for developing the LEDs’ source efficacy and lighting-product efficiency to ultimately achieve levels of efficacy of approximately 350 lumens per Watt (lm/W). For building designs to be sustainable in the future, it is critical that the windows-to-wall ratio (WWR) is optimized to minimize both heating and cooling loads, as well as the total energy consumed by the building for lighting, according to the efficiency of the LED, while still maintaining a suitable lighting level for occupants. This research examines the influence of the WWR on the total amount of energy consumed by standard buildings in Jordan using various LED luminaires (existing and projected efficiencies). DesignBuilder software was utilized to analyze the effect of LED-technology development on optimizing the WWR for a typical residential structure in Jordan. The research presents beneficial recommendations with respect to optimizing the WWR for primary decision-makers in the design of residential buildings with enhanced energy efficiency, considering the losses and gains associated with solar heat and light to capitalize on solar energy with no adverse impacts by windows size. The outcomes suggest a WWR of 17% could be achieved by typical residential buildings in Jordan that have extremely efficient LED lighting systems (350 lm/W), which is more than 50% less than the existing level of 40% recommended by multiple standards. Additionally, this study highlighted that when the efficiency of LED technologies increases, the energy demand of the building will be reduced because of lower energy usage combined with heat gain resulting from the LED efficiency.

Innovative Energy-Recovery Unit for the LED-Lighting System of Heavy-Duty Vehicles

In this work, the development of an energy recovery control unit to be incorporated in the light-emitting diodes (LEDs) lighting systems of heavy-duty vehicles is presented. This innovative industrial product adopts modern power electronics technology to improve existing trucks’ LED lighting system by eliminating the so far inevitable power consumption by the conventional central control unit of the majority of these vehicles, which is obligatory for the uninterruptable operation of their lighting system. The main idea of this innovative product is its capability to virtually increase the lighting system power consumption without actually consuming this amount of energy, thus facilitating the central control unit requirements regarding these vehicles in an energy-conscious way. Under this light, a mature power converter’s topology is employed to draw the proper amounts of power from the vehicle’s batteries supply, to the level that the central control unit recognizes, and return this energy back to the batteries. The tests results of the developed industrial product highlight the energy saving potential of the proposed energy recovery scheme, while the Life Cycle Cost Analysis (LCCA) results confirm its techno-economical and environmental profit for the truck applications under study.

Comprehensive survey and critical evaluation of the performance of state-of-the-art LED drivers for lighting systems

The adoption of light-emitting diodes (LEDs) for lighting applications is becoming increasingly relevant as this recent technology is advancing. Given the recent uptake of LED lighting technologies for distinctive end-uses, the research community has also committed to the development of an ever-increasing range of power electronic converters that are suitable for yielding maximum quality lighting, high efficiency, and long lifetimes. As one of the most recent and promising technologies of the moment, it is vital to fully understand the performance and merits of each state-of-the-art LED lighting technology. Accordingly, this paper compiles essential information about a broad range of state-of-the-art LED lighting systems, aiming to compare their performances in terms of efficiency. Based on the comparative analysis, the main merits and drawbacks of each LED lighting system architecture are obtained. Then, a detailed evaluation of the performance of a particular LED lighting system and the corresponding control strategy is developed, thereby enabling a clear view of the evolution of the performance of the system as a function of parameters like supply voltage and number of driver channels.

The effect of low light levels on postural stability in older adults with age-related macular degeneration.

To investigate the effect of low light levels on postural stability in older adults with and without age-related macular degeneration (AMD). Participants included 28 older adults [14 with AMD (mean age ± S.D., 83.4±6.7years) and 14 controls with normal vision (74.6±3.3years)]. Postural stability was assessed with eyes open on both a firm and foam surface under four lighting conditions in a randomised order: photopic (~436lux, vertically at the eye), sudden reduction to mesopic (~436 to ~1lux), adapted mesopic (~1lux) and adapted mesopic with a light emitting diode (LED) door frame lighting system (~1.3lux), using the root mean square (RMS) of the centre of pressure measures derived from an electronic force plate in the anterior-posterior (AP) and medio-lateral (ML) directions. Visual function was assessed binocularly (visual acuity, contrast sensitivity and visual fields), physical function was assessed using standardised measures (sit-to-stand, grip strength and the timed walk test) and self-reported difficulties under low light levels were recorded using the Low Luminance Questionnaire. Data were analysed using linear mixed models. For all participants, low light levels significantly increased postural sway on the foam surface in the AP (p=0.01) but not ML (p=0.80) direction, but had no effect on postural stability on the firm surface. On the foam surface, while AP-RMS sway was significantly greater in the sudden (p<0.001) and adapted (p=0.02) mesopic compared to the photopic condition, sway for the adapted mesopic with the LED lighting system was not significantly different to the photopic condition (p=0.20). On the foam surface, AP-RMS (p=0.02) and ML-RMS (p<0.001) sway were significantly greater in the AMD compared to the control group. None of the measures of visual function was significantly associated with AP- or ML-RMS sway. On the foam surface, low light levels significantly reduced postural stability in older adults with and without AMD, and postural stability was significantly reduced for the AMD group compared to controls, regardless of light level. Importantly, the LED lighting system reduced sway under mesopic conditions, which was not significantly greater than that measured under photopic conditions in either group. These findings have important implications for enhancing the visual environment for older adults with and without AMD to improve postural stability and reduce the risk of falls in low lighting environments.