LED Lighting System Research Articles

Enhancing Leafy Greens’ Production: Nutrient Film Technique Systems and Automation in Container-Based Vertical Farming

Urban agriculture has emerged as a crucial strategy to address food security and sustainability challenges, particularly in densely populated areas. This study focused on enhancing leafy greens’ production, specifically lettuce (Lactuca sativa L.) and arugula or rocket (Eruca sativa L.), using Nutrient Film Technique (NFT) systems and automation in container-based vertical farming. The study utilized a 20-foot shipping container retrofitted to create a thermally insulated and automated growth environment equipped with energy-efficient LED lighting and precise climate control systems. The results demonstrated significant improvements in crop yields, with the NFT systems achieving productivity up to 11 times higher than traditional methods in protected horticulture. These systems enabled continuous cultivation cycles, responding to the high market demand for fresh local produce. Moreover, the integration of low-cost sensors and automation technologies, each costing under USD 300, ensured that the environmental conditions were consistently optimal, highlighting this approach’s economic feasibility and scalability. This low-cost framework aligns with industry standards for affordable technology, making it accessible for small- to medium-sized urban agriculture enterprises. This study underscores the potential of vertical farming as a sustainable solution for urban food production. It provides a model that can be replicated and scaled to meet the growing demand for healthy, locally grown vegetables.

A wide voltage range non‐isolated continuous input buck‐boost converter for optimal green energy harvesting in LED lighting systems

A wide voltage range non‐isolated continuous input buck‐boost converter for optimal green energy harvesting in LED lighting systems

Fun with electricity: A novel ballistics gelatin model with LED tracking for ultrasound needle guidance.

Use of ultrasound (US) for procedural needle guidance can improve success rates, safety, and accuracy. Often, training is performed on task trainers, which can be prohibitively expensive. Determining undesired needle placement is difficult when the needle is poorly visualized with US. Currently available simulation phantoms cannot provide real-time feedback on the location of needle placement. The primary objective was to develop and determine feasibility of a low-cost simulation phantom with an internal circuit and LED light system to determine when a needle contacts internal structures. We also aimed to determine whether its use was associated with increased comfort level. Emergency medicine (EM) residents (PGY-1 to PGY-3) performed in-plane and out-of-plane US needle guidance using homemade phantoms. Comfort levels were assessed by pre- and post intervention survey. Outcomes were measured on Likert scale (minimum = 1, maximum = 5). The primary outcome was change in confidence markers before and after the simulation task. Secondary outcomes were survey results of comparisons of these models to prior training experiences on simulators and humans. All EM residents (30) in our program were invited to participate. Twenty participants enrolled and completed the study. In the primary outcome, median comfort with out-of-plane and in-plane guidance increased after using the model but was more pronounced for out-of-plane guidance. On a posttest survey, residents rated the models overall very similar to prior experience on simulators (median 5/5 [IQR 4.0-5.0]) and moderately similar to humans (median 3/5 [IQR 3.0-4.0]). We created a low-cost ballistic gelatin phantom with an internal electric needle guidance system. Use of the phantom for training was associated with increased learner comfort with the procedure. Learners rated the characteristics of the phantom as similar to higher-cost commercial equipment and humans.

Light pollution from led lighting systems and ways of reducing its environmental consequences

Light pollution from led lighting systems and ways of reducing its environmental consequences

The Impact of Temporal Light Modulation on Psychological Responses Assessed by the Stroboscopic Visibility Measure

ABSTRACT With the advent of LED lighting systems, short-term psychological responses to temporal light modulation (TLM) in offices have attracted considerable research attention in recent years. The stroboscopic visibility measure (SVM) is a leading metric for predicting the visibility of stroboscopic effects, one of visual perception effects of TLM. However, research is lacking to link TLM with potential psychological responses using the SVM metric. In this study, 10 participants joined in the experiments under 6 SVM levels (SVM: ~0.060; ~0.500; ~1.000; ~1.500; ~2.500; ~3.868) finishing tasks of subjective general rating, moving objects observation, sustained attention visual task, visual fatigue scale and PANAS (Positive and Negative Affect Scales). This study found that the SVM metric significantly evaluated the impact of TLM on psychological responses related to lighting ambiance and the moving objects observation. As expected, the stroboscopic visibility and motion dispersion scores increased with increasing SVM levels in the observation of rotating disc, and detectable stroboscopic effects were found to have negative effects on visual and work performances. However, the results of sustained attention visual task indicated that the SVM metric performed poorly in predicting the effects of TLM related to the eye saccades. High SVM levels were associated with negative experiences of lighting coziness, cognition performance and stroboscopic perception during moving objects observation. The scores were close to the expected at ~ 1.000 but exhibited a non-linearly increase with higher SVM levels. This study contributes valuable data to the ongoing discussions on setting limits for allowable modulation in practical lighting applications.

Design of powerful high-performance drivers for special-purpose LED lighting systems

This paper presents the results of the study of the parameters and characteristics of the developed high-performance electronic control circuits for special-purpose LED lighting systems based on a two-stage forward converter (driver) with an output power of more than 200 W. Operation of the developed driver in the output power range of 13 to 202 W and the supply voltage range of 160 to 250 V was investigated. The maximum efficiency of the developed power supply system at the voltage of 240 V and the output power of 140 W is 89.9%. For the chosen topology, further voltage increase may increase the efficiency, but lead to accelerated degradation of the driver components. The results of the experimental studies of the developed drivers showed the drivers efficiency in the range of 84 to 90% at a load of 52…202 W with a power factor above 0.97 and a nonlinear current distortion factor less than 23.4% over the entire studied range of supply voltages. The high efficiency of the developed driver in a wide range of output power suggests the possibility of using the driver in lighting systems that provide additional power supply to energy storage systems (batteries), including those ensuring operation in the absence of mains power supply.

Stand-Alone LED Lighting System Powered by PV and Battery: Electrical Overall Performance Analysis of a Case Study

Stand-Alone LED Lighting System Powered by PV and Battery: Electrical Overall Performance Analysis of a Case Study

Design of LED Lighting System with Improved Color Mixing Uniformity

Design of LED Lighting System with Improved Color Mixing Uniformity

Evaluation of Growth, Yield and Bioactive Compounds of Ethiopian Kale (Brassica carinata A. Braun) Microgreens under Different LED Light Spectra and Substrates

Microgreens are innovative vegetable products whose production and consumption are gaining popularity globally thanks to their recognized nutraceutical properties. To date, the effects of lighting conditions and growing substrate on the performances of Brassica carinata microgreens (indigenous to Africa) remain underexplored. The present study aimed at providing insights into the influence of different lighting treatments provided by LEDs, namely monochromatic blue (B), red (R), cool white (W) and a combination of three color diodes (B + R + W), and substrates (cocopeat, sand and cocopeat–sand mix (v/v) (1:1)) on the growth, yield and bioactive compounds of B. carinata microgreens. Seeds were germinated in dark chambers and cultivated in growth chambers equipped with LED lighting systems for 14 days under a fixed light intensity of 160 ± 2.5 µmol m−2 s−1 and photoperiod of 12 h d−1. The best performances were associated with the spectrum that combined B + R + W LEDs and with substrate resulting from the cocopeat–sand mix, including the highest yield (19.19 g plant−1), plant height (9.94 cm), leaf area (68.11 mm2) and canopy cover (55.9%). Enhanced carotenoid and flavonoid contents were obtained with B + R + W LEDs, while the B LED increased the total amount of chlorophyll (11,880 mg kg−1). For plants grown under B + R + W LEDs in cocopeat, high nitrate levels were observed. Our results demonstrate that substrate and light environment interact to influence the growth, yield and concentration of bioactive compounds of B. carinata microgreens.

Design and testing of a high-performance solar LED streetlight

This paper presents the development and validation of a high-performance solarpowered charging streetlight. Our controller incorporates various charging modes, including MPPT charging, constant current charging, and constant voltage charging, and the controller can automatically change the charging mode based on the battery level. The streetlight can achieve brightness adjustment through PWM adjustment. The controller turns off the streetlights once the battery voltage reaches the over-discharge protection voltage. However, turning off the streetlights inevitably results in a voltage rebound above the over-discharge protection voltage. Consequently, the streetlights enter a cycling pattern of illumination and extinguishment. We have addressed this issue by incorporating a voltage rise threshold in the controller program, effectively preventing the streetlights from cycling between illumination and extinguishment. The MCU (Micro Controller Unit) can output multiple sets of PWM waves, where each set can control the on/off state of an LED light group. Combining multiple LED groups enables the driving and control of high-power LED street lights. We designed and constructed two solar-powered LED lighting systems to demonstrate the practicality of our approach. Extensive long-term outdoor field tests validate the robust performance of our control system.

Redefining Sustainable Agriculture for the 21st Century by Vertical Farming

In the face of a rapidly growing global population, increasing urbanization, and the threats posed by climate change, traditional agricultural practices are becoming increasingly unsustainable. Vertical farming, a method of growing crops in vertically stacked layers within controlled environments, offers a promising solution to these challenges. This review paper explores the potential of vertical farming to redefine sustainable agriculture in the 21st century. It examines the key advantages of vertical farming, including efficient land use, reduced water consumption, year-round crop production, and reduced transportation costs. The paper also discusses the technological advancements that have made vertical farming feasible, such as LED lighting, hydroponic and aeroponic systems, and automation. Furthermore, it highlights the economic viability and potential for vertical farming to contribute to food security in urban areas. The review concludes by addressing the challenges and limitations of vertical farming and outlining future research directions to fully realize its potential as a sustainable agricultural practice.

Energy Performance Analysis of the Renovation Process in an Italian Cultural Heritage Building

Renovating buildings with cultural heritage significance is an important step toward achieving sustainability in our cities. The benefits are not only energy-related but also encompass social aspects that make these renovations a high apriority. The present work investigates the renovation process of a cultural heritage building in the Municipality of Trento in Italy, specifically focusing on achieving energy savings and renewable energy integration by implementing various renovation actions. These renovation actions include improvements to the building envelope, such as roof insulation and window replacements. Additionally, the renovation actions for active systems involve the installation of a ground-source heat pump for heating/cooling coupled with a borehole thermal energy storage system, which is an innovative technology for the renovation of cultural heritage buildings. The electrical systems of the building are upgraded through the addition of standard rooftop photovoltaics, innovative building-integrated photovoltaics (shingles), and the installation of an LED lighting system. The baseline and the renovation scenarios are studied using the dynamic simulation tool INTEMA.building, written in the programming language Modelica. This tool simulates both the building envelope and the energy systems with a high level of detail, using advanced control systems and adjustable time steps. According to the simulation analysis, the primary energy demand is reduced by 30.49%, the final energy demand by 36.74%, and the net electricity demand by 8.72%. Results from this study can be useful to interested stakeholders (e.g., building owners, architects, construction companies, public agents, and urban planners) dealing with the renovation of cultural heritage and protected buildings. Also, the results can be exploited for estimating energy savings by applying advanced renovation strategies for cultural heritage buildings.

Design of Arduino UNO based smart irrigation system for real time applications

The fundamental principle of the paper is that the soil moisture sensor obtains the moisture content level of the soil sample. The water pump is automatically activated if the moisture content is insufficient, which causes water to flow into the soil. The water pump is immediately turned off when the moisture content is high enough. Smart home, smart city, smart transportation, and smart farming are just a few of the new intelligent ideas that internet of things (IoT) includes. The goal of this method is to increase productivity and decrease manual labour among farmers. In this paper, we present a system for monitoring and regulating water flow that employs a soil moisture sensor to keep track of soil moisture content as well as the land’s water level to keep track of and regulate the amount of water supplied to the plant. The device also includes an automated led lighting system.

Thermal management of honeycomb heat sink filled with phase change material for smart lighting applications

Recently, thermal management of LEDs lamps has become increasingly essential due to the widespread integration of LEDs in smart lighting applications. In this work, we focus on the thermal analysis of convective heat transfer using a honeycomb heat sink designed for LEDs lamp cooling. Three different heat sink geometries were examined: an aluminum-filled honeycomb radiator, a hollow honeycomb radiator, and a hollow honeycomb radiator incorporating a phase change material (PCM) layer. The results obtained from numerical simulations using COMSOL Multiphysics® showed that the third heat sink geometry, when employed in short-duration lighting applications, led to a 25% reduction in temperature for a 20W power lamp. We also determined the optimal operational time, during which the temperature drop is maximum. Moreover, we observed that the integration of a PCM-filled honeycomb radiator in cyclic lighting applications (involving on/off cycles and high/low power settings) significantly mitigates temperature rise in the lamp by leveraging the PCM's heat storage capacity. This approach effectively prevents thermal shocks, ensures prolonged LEDs performance, and contributes to energy savings in the lighting sector. By addressing the thermal management challenges associated with LEDs lamps through innovative heat sink designs and the utilization of PCM, our research offers valuable insights for enhancing the overall performance and efficiency of LED lighting systems.

Experimental Investigation on the Thermal Performances of a New Design of Pulsating Heat Pipe With Two Condensers

Abstract In this paper, for the first time, a novel design of pulsating heat pipe (PHP) with one evaporator and two condensers located on both sides of the evaporator at an angle to the horizon was proposed, manufactured, and experimentally investigated for the purpose of use in cooling systems for electronic devices operating in a tilted position. The PHP body is made of a copper capillary tube with an inner diameter of 1.5 mm. The working fluid is methanol. The number of turns is 4. The heating zone dimensions are 60 mm × 36 mm, and the cooling zone dimensions are 200 mm × 35 mm. The РНР condensers were cooled by aluminum radiators blown by two fans with an air flowrate of 5.2 m3 h–1. The launch of the РНР began with a power of 30 W at all positive tilt angles and in a horizontal position. The dependences of the temperature in the heating and cooling zones and the PHP thermal resistance both on the power input (from 30 W to 200 W) and on the orientation in space (at tilt angles of 0 deg, 15 deg, 30 deg, 60 deg, 90 deg) were obtained. It is shown that when the evaporator is located below the condensers, the РНР works stably. Moreover, in the power range from 120 W to 200 W, the tilt angle practically does not affect the thermal resistance of the PHP. A comparison of the thermal resistance of the developed РНР with known РНРs filled with methanol showed the high efficiency of the developed РНР: at power input from 120 W to 200 W, the thermal resistance was from 0.2 °С W–1 to 0.18 °С W–1. The developed РНР design is promising for use in air cooling systems, for instance, of radar transmit/receive modules and high-power LED lighting systems.

Spectral reflectance reconstruction based on wideband multi-illuminant imaging and a modified particle swarm optimization algorithm.

A method for spectral reflectance factor reconstruction based on wideband multi-illuminant imaging was proposed, using a programmable LED lighting system and modified Bare Bones Particle Swarm Optimization algorithms. From a set of 16 LEDs with different spectral power distributions, nine light sources with correlated color temperatures in the range of 1924 K - 15746 K, most of them daylight simulators, were generated. Samples from three color charts (X-Rite ColorChecker Digital SG, SCOCIE ScoColor paint chart, and SCOCIE ScoColor textile chart), were captured by a color industrial camera under the nine light sources, and used in sequence as training and/or testing colors. The spectral reconstruction models achieved under multi-illuminant imaging were trained and tested using the canonical Bare Bones Particle Swarm Optimization and its proposed modifications, along with six additional and commonly used algorithms. The impacts of different illuminants, illuminant combinations, algorithms, and training colors on reconstruction accuracy were studied comprehensively. The results indicated that training colors covering larger regions of color space give more accurate reconstructions of spectral reflectance factors, and combinations of two illuminants with a large difference of correlated color temperature achieve more than twice the accuracy of that under a single illuminant. Specifically, the average reconstruction error by the method proposed in this paper for patches from two color charts under A + D90 light sources was 0.94 and 1.08 CIEDE2000 color difference units. The results of the experiment also confirmed that some reconstruction algorithms are unsuitable for predicting spectral reflectance factors from multi-illuminant images due to the complexity of optimization problems and insufficient accuracy. The proposed reconstruction method has many advantages, such as being simple in operation, with no requirement of prior knowledge, and easy to implement in non-contact color measurement and color reproduction devices.

Thermal management of multiple LEDs for high-power lighting applications

Power LED lighting has suffered from substantial heat generated, leading to significant performance degradation. Consequently, achieving an optimal distribution of LEDs is essential to ensure high luminance efficiency. Implementing effective thermal treatment is important to prevent any potential degradation in the performance of the LED lighting system. Optimizing the arrangement of individual LEDs is a promising approach to mitigating heat accumulation issues. In this paper, we propose a reasonable approach to obtaining the optimal distribution of LED lighting systems under DC biasing and PWM operating conditions. The thermal analysis simulation was performed based on the theoretical assumption to evaluate the thermal distribution of a single LED. Thermal analysis was conducted on an LED lighting system with 20 LEDs, and the distance between LEDs ranged from 4 mm to 24 mm. The simulated analysis showed that the maximum temperature could be controlled from 65.1 ℃ to 58.7 ℃. We discussed the optimum arrangement of LEDs and how heat generated by an LED influences the system. In addition, the LED lighting was operated in PWM mode to mitigate the thermal issues. The relationship between luminance efficiency and operation condition is discussed. Thus, the luminance efficiency improved from 114.8 lm/W to 126.8 lm/W, and the thermal relaxation time was no longer than 0.013 s. The process of determining the optimal distance between LEDs was very effective in achieving an optimized power operating condition and LEDs distribution in the module for a compact volume and enhanced performance.

Long-Term Monitoring Campaign of LED Street Lighting Systems: Focus on Photometric Performances, Maintenance and Energy Savings

The renovation of public lighting installations by replacing the traditional systems with LED technologies and introducing smart lighting control systems is a policy widely adopted to contain energy consumption and expenditure. Additionally, the long-term monitoring of the depreciation of the new lighting systems is a crucial issue. The aim of this study is to report the results of in-field measurements of new LED lighting systems in the city of Turin (Italy). A method was defined to assess: (i) energy performance (through data from the remote-control system); (ii) photometric performance (through in-field measurement campaigns); and (iii) depreciation of the photometric performance over a period of approximately 5 years. Results demonstrated that the new LED systems allow us to achieve an average energy saving of 51% compared to the ex-ante condition, improving the photometric performances and compiling the standard requirements by lowering the over-illumination levels. Moreover, the measured depreciation of the LED systems over time was compared with the predicted depreciation, estimated based on the calculation method proposed in Standards BS 5489-1:2020 and ISO/CIE TS 22012:2019. The results obtained showed that the measured depreciation of the photometric performance was closer to the predicted depreciation trend according to BS 5489-1:2020 (variations between 0% and 4%), while greater variations (between 17% and 23%) emerged considering the ISO/CIE TS 22012:2019.

The effect of osmotic stress, lighting spectrum and temperature on growth and gene expression related to anthocyanin biosynthetic pathway in wild strawberry (Fragaria vesca L.) in vitro

ABSTRACT The goal of this research was to evaluate the effect of light, temperature, sucrose and PEG on the growth of Fragaria vesca in vitro and the expression of regulatory Myb10, WD40 and enzyme-coding genes CHI, CHS, DFR, EGL, F3H and UFGT, which are essential for anthocyanin biosynthesis. We observed plants’ response to osmotic stress, the decrease in growth and microshoot weight. A change in the expression of the investigated genes was evident under the suboptimal concentration of sucrose. The addition of PEG to the medium caused a decrease in microshoot weight and gene expression. Blue + red lights of the LED lighting system significantly affected microshoot growth in vitro. Red and blue + red + UV lights slightly reduced microshoot weight and caused a reddish colour of petioles, which indicate increased anthocyanin synthesis. Moreover, most of the studied genes’ expression tended to increase when shoots were exposed to blue, blue + red and blue + red + UV lights. A temperature of 15°C (vs 22°C) significantly reduced the mean fresh weight of microshoots while increasing CHI and CHS gene expression and decreasing WD40 gene expression. Exposure to a higher temperature (30°C) induced the vitrification of microshoots, although the fresh weight did not differ from that of the control. Gene expression also depended on the duration of exposure. In the case of CHS, gene expression remained the same or increased after exposure for 1 week and then decreased after exposure for 4 weeks.

ENHANCING WHITE OYSTER MUSHROOM CULTIVATION THROUGH LIGHT STIMULATION USING WHITE LED

This study aims to investigate the impact of different illumination durations on the yield of white oyster mushrooms cultivated in a controlled environment mushroom chamber, with a focus on the advantages of LED lighting over conventional lighting methods. The experiment considered various time exposures: 3, 6, 9, 12, 15, and 24 hours per day, while fluorescent light exposure for 12 hours per day served as the control group. Parameters such as mushroom weight, pileus diameter, stipe diameter, and stipe length were measured. Results indicated that the most significant fruiting bodies in terms of pileus diameter (105.76 mm) and stipe diameter (15.26 mm) were observed with a 15-hour illumination exposure. Conversely, the 12-hour exposure using fluorescent lamps resulted in the smallest pileus diameter, averaging 79.70 mm. Notably, a 3-hour exposure demonstrated the most substantial impact on yield, resulting in 182.4 g over two harvest cycles. In conclusion, treating white oyster mushrooms with white LED lighting can enhance productivity. This is primarily due to the excessive heat and higher light intensity generated by fluorescent lights, which can inhibit growth during the fruiting development stage. Therefore, adopting white LED lighting systems offers greater control over the ideal light intensity required for optimal mushroom growth.