Illuminating Engineering Society Of North America Research Articles

Improving Natural and Artificial Lighting in Coastal Architecture Classrooms: Insights and Applications

This research examines the natural and artificial lighting performance comparison in an architecture classroom at a university in southern Thailand and gives principles for enhancing lighting design. The sample for the study was classroom spaces. The efficacy of natural and artificial lighting was studied using static and dynamic models, and data were obtained using a 4 in 1 multi-function environmental meter at various times of the day. The current study adopted the IESNA (Illuminating Engineering Society of North America) and CIBSE (Chartered Institution of Building Services Engineers) lighting standards for the performance comparison analysis. The results showed that the natural light in the classrooms did not satisfy the standards for lighting levels. In contrast, the artificial lighting was more effective but raised some issues with uniformity and glare. The study offers recommendations for improving lighting effectiveness, maximizing natural light, reducing energy consumption, improving the uniformity of artificial illumination, addressing issues with various classroom lighting designs, and creating more comfortable and realistic learning environments.

Design and Development of a Visual Comfort Questionnaire (VCQ) for Employees in the Workplace

Background and Objectives: Visual comfort is an important and influential factor on safety, mental health, sleep quality, and musculoskeletal disorders of employees in the workplace. This study aimed to design and develop a questionnaire to assess the visual comfort of employees in the workplace.
 Methods: The study was performed on 101 participants (88 men and 13 women) in the food industry. First, the available lighting questionnaires in the field of lighting were reviewed, and a question bank was set up. Twenty questions were considered in two sections of natural and artificial lighting (10 questions in each section) based on the opinion of 10 experts in this field. The validity of the questionnaire was assessed using the content validity index (CVI) based on the comments of experts. To validate the questionnaire in the workplace, The lighting of employees' workstations was evaluated according to the Illuminating Engineering Society of North America (IESNA) standards and compared with the results of the questionnaire.
 Results: The Cronbach's alpha of natural and artificial lighting visual comfort questionnaire was 0.858 and 0.922, respectively. The total CVI of the questionnaire was 1. There was a significant positive relationship between the score of the visual comfort questionnaire and the workstations' illumination (P = 0.001). More than 97% of employees who had workstations with the desired lighting reported excellent levels of visual comfort.
 Conclusion: The visual comfort questionnaire had good and acceptable reliability and validity. This tool is recommended for the use of visual comfort asessments of employees in work environments given the fewer number of and simplicity of sentences.

In-Situ early anomaly detection and remaining useful lifetime prediction for high-power white LEDs with distance and entropy-based long short-term memory recurrent neural networks

High-power white light-emitting diodes (LEDs) have demonstrated superior efficiency and reliability compared to traditional white light sources. However, ensuring maximum performance for a prolonged lifetime use presents a significant challenge for manufacturers and end users, especially in safety–critical applications. Thus, identifying functional anomalies and predicting the remaining useful lifetime (RUL) is of enormous importance in the operational longevity of the device. To address such challenges, this study proposes a combination of distance-based Mahalanobis distance (MD), entropy generation rate (EGR), and deep learning models for improved anomaly detection and RUL prediction accuracy. Unlike conventional health indicators based on luminous flux data that are challenging to monitor relevant optical performance, the MD and EGR methods are employed to extract in-situ monitored thermal and electrical data as new health indicators. Long short-term memory recurrent neural networks (LSTM-RNN) and convolutional neural networks (CNN) are established to detect anomalies and predict the RUL. The accelerated degradation tests of 3 W high-power white LED have been conducted, and the online and offline collected experimental data are deployed for model development and performance evaluation. The performance of the proposed methods is compared against the Illuminating Engineering Society of North America (IESNA) TM-21 method. The results indicate that LSTM-RNN, when combined with either MD or EGR, can detect anomalies with significantly fewer data (70 %) than is typically required. Furthermore, a significant improvement in prediction accuracy in RUL prediction based on MD and EGR-constructed time series health indicators and employed with the LSTM-RNN model demonstrates the effectiveness of the proposed methods.

Tunnel lighting calculation model based on bidirectional reflectance distribution function: Considering the dynamic changes in light transmittance in road tunnels

The current tunnel lighting calculation method does not completely consider the dynamic change in light transmittance in a tunnel and reflection characteristics of the tunnel sidewall. Thus, the measured and calculated values of road surface illuminance present a considerable difference, which seriously affects the tunnel lighting design and quality evaluation. To overcome this limitation, in this study, in addition to theoretical analysis and measured experiments, the changing trend in light attenuation is analyzed and a light attenuation model is established. Next, a bidirectional reflectance distribution function that can accurately reflect the reflection characteristics of tunnel sidewall is combined with the light attenuation model and calculation steps based on optical theory to construct a tunnel lighting calculation model considering light transmittance (TLCM-LT). Finally, theoretical calculation and actual measurement verification are conducted via an experimental tunnel simulation, and the results obtained using TLCM-LT are compared with the values calculated based on the Commission Internationale de l'éclairage (CIE), Illuminating Engineering Society of North America (IESNA), and Industry Standards of the People’s Republic of China (JTG) specifications. The results show that the average relative error of the TLCM-LT in a smoke-free environment is 1.31 %. In the presence of smoke, the average relative error of the model fluctuates in the range of 2.19–6.8 % with the change in light transmittance in the tunnel, which is significantly lower than the errors obtained based on the CIE, IESNA, and JTG specifications. Compared with a cement sidewall, the average increase rates in road surface illuminance and illuminance uniformity of the highly diffuse reflective sidewall are 23.21 and 3.65 %, respectively.

A novel tunnel lighting method aided by highly diffuse reflective materials on the sidewall: Theory and practice

Interior surfaces of tunnels can reflect light when a highly diffuse reflective material is used on the sidewalls. This study introduces a novel energy-saving method that uses the reflected light effectively. To validate the proposed method, the brightening effect of a highly diffuse reflective material is measured based on the bidirectional reflection distribution function (BRDF) of the sidewall materials. The BRDF specifies the reflective properties of the sidewall materials, and the incremental reflection is then quantified. The proposed method offers better computational certainty and sidewall material adaptability than those of existing methods. For different materials selected as test objects, the error between the calculated and measured values was controlled to be less than 5.35%. In addition, the relative error between the calculated and measured values, obtained using the proposed method, was 3.62% on average, and the corresponding errors obtained using China's lighting design rules and the Recommended Practice for Tunnel Lighting presented by the Illuminating Engineering Society of North America (IESNA) were 18.02% and 7.98%, respectively. Overall, the proposed method provides a theoretical basis to help realize the unification of tunnel lighting with safety, energy savings, and comfort.

Prognostics of radiation power degradation lifetime for ultraviolet light-emitting diodes using stochastic data-driven models

With their advantages of high efficiency, long lifetime, compact size and being free of mercury, ultraviolet light-emitting diodes (UV LEDs) are widely applied in disinfection and purification, photolithography, curing and biomedical devices. However, it is challenging to assess the reliability of UV LEDs based on the traditional life test or even the accelerated life test. In this paper, radiation power degradation modeling is proposed to estimate the lifetime of UV LEDs under both constant stress and step stress degradation tests. Stochastic data-driven predictions with both Gamma process and Wiener process methods are implemented, and the degradation mechanisms occurring under different aging conditions are also analyzed. The results show that, compared to least squares regression in the IESNA TM-21 industry standard recommended by the Illuminating Engineering Society of North America (IESNA), the proposed stochastic data-driven methods can predict the lifetime with high accuracy and narrow confidence intervals, which confirms that they provide more reliable information than the IESNA TM-21 standard with greater robustness.

Lighting system design according to different standards in office building: A technical and economic evaluations

Lighting system is an important sub-system in office buildings. A good design can contribute energy saving and visual comfort to occupants. This paper presents a comparison of lighting system design according to different standards: European Standard EN12464-1 and Malaysian Standard MS1525 in terms of average illuminance level and illuminance uniformity. In the design, the illuminance measurement is according to the Illuminating Engineering Society of North America (IESNA) and the European Standard EN12464-1. Three types of luminaires are considered which are: T8, T5 and light emitting diode (LED) lamps. The technical and economic evaluations are taken into account in this paper. The technical evaluations are considered the number of luminaires, average illuminance level and illuminance uniformity. The energy consumption (EC) and lighting energy numeric indicator (LENI) are considered according to the European Standard EN15193. Meanwhile, the economic evaluation involves billings and luminaires costs and billing savings. The case study is an office room and it is modelled and simulated using DIALux software. The results show that the design according to the European Standard EN12464-1 with uniformity based method that used T5 lamps had contributed to the highest number of luminaires and costs. Whereas, the design according to the Malaysian Standard MS1525 with illuminance level based method that used LED lamps had contributed to the lowest number of luminaires and costs. Thus it can provide the higher billing savings. It can be concluded the LED has great potential to replace T8 and T5 lamps.

AC COB형 LED 가로등의 광학계 배광 패턴

This study attempted to design lights with Type II distribution suitable for LED street lights based on the regulations of street light distribution developed by the Illuminating Engineering Society of North America (IESNA). The shape of an asymmetric lens, different from that of a rotationally symmetric lens, cannot be generated using a simple mathematical formula. In the first trial, the outline of the lens was fixed and simulated to confirm the distribution type. Following ISENA regulations, some problems that occurred during simulations and repeating was be modified that process is how we detected errors. Through optical research and simulations, a lens conforming to the regulations of Type II very short, Type II short, and Type II medium distributions was developed. A prototype was developed using simulation data and it was subjected to distribution tests. The results show that it can compare with property of Type II distribution.

Research Study on Gained Energy Efficiency in a Commercial Setup by Replacing Conventional Lights with Modern Energy Saving Lights

Lighting accounts for roughly one-fifth of global electricity consumption. The energy consumption for buildings lighting system can reach 30% of the total consumption. The demand for energy is growing day by day with growth in population, revolution in life style, and change in technology. This growing demand led to energy crisis which is the biggest warning for economic stability for developing countries like Pakistan. From the last ten years, Pakistan is facing severe electrical energy shortfall and thus the problem of balancing Pakistan's power supply and the demand has remained in a stalemate position. This crisis has badly affected the everyday life, business and industry. Despite taking steps like resolving this issue through initiating a number of power plant projects, the country still faces a significant energy shortfall. Hence, in order to reduce the gap between electricity demand and supply, the need for efficient usage of available electric energy through opting for the modern, highly energy efficient devices/systems cannot be undermined. A possible way to reduce the electricity consumption, and thus the energy bill, is related to the substitution of the old lamps and control of the new ones. Significant energy conservations can be achieved by reducing energy depletion by artificial lighting which has potential of energy saving by using efficient lighting technologies. For this purpose, new performance lamps like LEDs are studied and developed. Light Emitting Diodes (LEDs) have recently entered the lighting market as an energy efficient alternative to traditional light sources such as incandescent and fluorescent bulbs. A case study is carried out for a commercial setup to compare the enactment, suitability, sustainability and economic effects of conventional and LED lights in a commercial setup. An innovative lighting scheme has been designed by using DIALux simulation software based on international standards of Illuminating Engineering Society of North America (IESNA).The conventional lights on the shop floor has been substituted with LED lights as per software design. After hardware installation, it is revealed that by implementing this lighting scheme there is 47% of energy savings and user satisfaction with financial savings of Rs. 55570 per year, having 1.368 years payback period that validates use of LEDs as per proposed lightning design for wide-ranging lighting solicitations

Design of asymmetric freeform lens for low glared LED street light with total internal reflection.

The study is focused on the asymmetric secondary freeform lens (ASFL) design for creating a low glared light-emitting diode (LED) street light. The lens is mounted on a chip on board (COB) LED as the new LED street light module to perform a non-axial symmetric light intensity distribution. The experimental results show that the street light can work without inclining lamps and reach Chinese National Standards (CNS) and Illuminating Engineering Society of North America (IESNA) standards at the same time.

Prognostic algorithms for L70 life prediction of solid state lighting

The life of light-emitting diodes (LEDs) is difficult to measure by traditional testing methods as they are not likely to fail completely. The Illuminating Engineering Society of North America (IESNA) uses a standard regression approach based on short-term collected lumen data to predict the L70 lifetime of LEDs. In this paper, a model-based prognostics method is employed to determine the life of luminaires using LEDs. Unscented Kalman filter and particle filter algorithms are used for degradation model parameter estimation. An analytical approach based on three statistical models (Weibull, normal, lognormal) is employed and a best fit is determined by the Akaike information criterion. The resulting L70 is compared with L70 derived from the IESNA approach to accurately determine the best prognostic method.

Predicting long-term lumen maintenance life of LED light sources using a particle filter-based prognostic approach

Lumen degradation is a common failure mode in LED light sources. Lumen maintenance life, defined as the time when the maintained percentages of the initial light output fall below a failure threshold, is a key characteristic for assessing the reliability of LED light sources. Owing to the long lifetime and high reliability of LED lights sources, it is challenging to estimate the lumen maintenance life for LED light sources using traditional life testing that records failure data. This paper describes a particle filter-based (PF-based) prognostic approach based on both Sequential Monte Carlo (SMC) and Bayesian techniques to predict the lumen maintenance life of LED light sources. The lumen maintenance degradation data collected from an accelerated degradation test was used to demonstrate the prediction algorithm and methodology of the proposed PF approach. Its feasibility and prediction accuracy were then validated and compared with the TM-21 standard method that was created by the Illuminating Engineering Society of North America (IESNA). Finally, a robustness study was also conducted to analyze the initialization of parameters impacting the prediction accuracy and the uncertainties of the proposed PF method. The results show that, compared to the TM-21 method, the PF approach achieves better prediction performance, with an error of less than 5% in predicting the long-term lumen maintenance life of LED light sources.

New Sights of Light-up in Tokyo I : Tokyo Gate Bridge(Illumination Until Now and in Future～ : Tokyo Branch)

Tokyo Gate Bridge, nicknamed Dinosaur Bridge because of its shape, opened to traffic on February 12, 2012. A light-up was held on April 25 of the same year. Symbolic lighting was designed to enhance the peculiar form of this bridge that serves as a new gateway to Tokyo. Various committees executed detailed examinations for this major public structure; maritime experts carried out studies to prevent interference with shipping; bridge design and construction experts were consulted. Overall planning and design took nine years to complete. As a result, each truss is lit individually; light dispersion from color LEDs on the sides of the bridge is tightly controlled; bridge footings and the underside of the span are attractively lit. In particular, colors of LEDs used to light the sides are changed each month to give a seasonal feel; every hour on the hour light variations give the impression of waves; thus the overall lighting is dynamic. In consideration of the environment and energy conservation, solar power is used for about 40 percent of the scenic lighting. In autumn 2013, the lighting design of Tokyo Gate Bridge received the Award of Excellence from Illuminating Engineering Society of North America (IESNA).

LED램프와 메탈램프가 도로조명환경에 미치는 특성 비교평가

The problems of light pollution first became an issue in the 1970s when astronomers identified the degradation of the night sky due to the increase in lighting associated with development and growth. As more impacts to the environment by lighting have been identified, many attempts have been made for reducing light pollutions. To prevent light pollution and increase energy efficiency, Seoul Metropolitan Government(SMG) replaced metal halide road lighting to LED luminaire in four arterial highway in Seoul. The present study compared the lighting characteristics of metal halide and LED luminaire in terms of Korea Standard for road lighting(KS A 3701) and BUG rating from Illuminating Engineering Society of North America(IESNA). The results showed that LED luminaire increased road surface luminance up to 2 times in average compared to the metal halide environment. Also, LED luminaire reduced the glare value by 2 times and luminous flux over 50% than the metal halide luminaire. In comparison with the BUG ratings, LED luminaire rated 1 degree lower for the backlight ratings and 3-4 degrees lower for the uplight ratings. The measured values testified that the LED luminaire is effective for roadway lighting and light pollution reduction.

Field and Software Evaluation of Illuminance from LED Luminaires for Roadway Applications

Field measurements and lighting analysis software were used to conduct an evaluation of the illuminance of LED roadway luminaires. Three sets of recently developed LEDs and one set of high-pressure sodium luminaires were installed in the field, and data were collected separately for each luminaire according to Illuminating Engineering Society of North America (IESNA) LM-50-99. Photometric characteristics provided by the manufacturers of the luminaires were used to assess their performance with AGi32 lighting analysis software, and the results were compared with the field illuminance data. Results showed that field illuminance was sometimes lower than the illuminance indicated by the software; these differences varied in both magnitude and location, depending on the LED luminaire. Multiplicative factors to describe the differences were estimated and ranged from 0.96 (relatively small) to 0.57 (relatively large). Larger differences were located near the light poles and at the middle and third points of the span. These findings suggest that quick checks can be performed by taking illuminance measurements at key points along the span to provide an approximation of the differences between field and software data. Discrepancies between software and field data may be very important in the selection of luminaires for a given road and pedestrian conflict classification, as the field illuminance may not reach minimum levels required by public agencies. This point is illustrated with an example that uses minimum requirements from the Illinois Department of Transportation. Full sets of repeated field data points for state-of-the-art LED roadway luminaires, collected according to IESNA LM-50-99, are presented.

The daylit area – Correlating architectural student assessments with current and emerging daylight availability metrics

This paper proposes a method for testing current and emerging daylight availability metrics such as daylighting factor, daylight autonomy, useful daylight illuminance and LEED 3.0 requirements against building occupant assessments of a daylit space. During spring 2011 the method was tested as a classroom exercise by 60 architectural students enrolled in two graduate-level building science courses in the 2nd floor studio space of le Corbusier’s Carpenter Center in Cambridge, MA, USA. The results from this test yielded that the Lighting Measurement protocol for Spatial Daylight Autonomy, that is current being developed by the Illuminating Engineering Society of North America (IESNA) daylighting metrics committee, reproduced the student assessments of the daylit area in the space more reliably than the other tested daylight availability metrics. These findings are preliminary and still need to be validated and refined in other spaces. Apart from providing valuable data points for scientific experiments, the method also has substantial educational value as a teaching exercise for architectural students to develop an intuitive understanding of contemporary daylight performance metrics, as well as a feeling of how their personal lighting preferences compare to these metrics.

Analysis and Design of a New Roof Monitor for Day and Night Illumination of a Large Volume Room

The Illuminating Engineering Society of North America (IESNA) Lighting Handbook recommends illuminance criteria for specific applications to raise the ``minimum standard of care'' required of lighting design to meet human, economic environmental, and architectural concerns. Specific criteria for daylighting of auditoriums (i.e., large rooms) focus on the importance of daylighting integration, control and flexibility, illuminance levels, light distribution, color appearance, and glare. A new skylight design for day and night illumination of a large volume room is proposed. The feasibility of this unique design uses clerestory windows, also known as a roof monitor, and an outdoor lighting array. The design illuminates a room 100-feet wide, 100-feet long, and 75-feet high, located at 40°-north latitude. Comparisons have been made to flat skylight wells for the same volume. The demonstrated design meets lighting criteria that satisfy IESNA standards for day and night to play basketball, a task that requires low contrast and involves small sized objects, like a basketball. The design has been tested with AGI32 software created by Lighting Analysts, Inc of Littleton, Colorado. Results show the new skylight meets IESNA criteria F (for tasks like basketball) during the daytime with an assist by external lighting as the setting sun reduces the daylight.

Measurement of Pavement Surface Reflectance for a Balloon Lighting System

Nighttime construction offers many advantages to the public and to state agencies. Under these conditions, traffic is minimal and construction operations can be conducted effectively and quickly. In addition, cooler temperatures are favorable for the equipment and the material being installed. Despite these advantages, controlling glare is a critical and important issue in adequately lighting highway work zones. One of the controlling parameters in glare calculation is the pavement luminance, which is a quantitative measure of the surface brightness. Pavement luminance is based on predefined parameters known as r values provided by the Illuminating Engineering Society of North America (IESNA) for four standard pavement surfaces in the r tables. With the recent introduction of balloon lighting system for construction applications, the objective of this study was to measure pavement reflectance characteristics for this system in the laboratory and to compare the results to the standard r tables. For this purpose, a laboratory experimental setup was developed. On average, measured r values were 20% greater than the IESNA standard values for concrete surfaces (R1), 84% greater for R2 standard surfaces, and 95% greater for R3 standard surfaces. An analysis of variance statistical analysis indicated that the differences between the measured r values and standard r tables were not significant for concrete surfaces but were statistically significant for asphalt road surfaces. This was attributed to the weathering of the road samples used in this study, to the shorter towers used with balloon lights, and to major changes in asphalt construction practices and mix ingredients in the past 30 years. Recommendations based on the results of this study are presented.

VCP and UGR Glare Evaluation Systems: A Look Back and a Way Forward

We review the discomfort glare evaluation systems of the Illuminating Engineering Society of North America (IESNA), Visual Comfort Probability (VCP), and that of the International Commission on Illumination (CIE), Unified Glare Rating (UGR), as they apply to interior electric lighting. We provide an overview of the history and research behind them and an extensive bibliography.The current IESNA Handbook states that the VCP is very limited in applicability to modern lighting systems, and was validated for lensed fluorescent systems only. The CIE's UGR system has been shown to be a good predictor of human responses for lensed fluorescent systems. Recently, the CIE has proposed extensions to the UGR discomfort glare model, which are applicable to most modern lighting systems, including small, large, and complex systems. We provide a review of these extensions and the research behind them. There are many similarities between VCP and UGR and only minor differences, and so we recommend that research be undertaken to validate the UGR's extensions to small, large, and complex systems.