Daylight Illuminance Research Articles

The incidence of smart windows in building energy saving and future climate projections

The ongoing climate crisis leads to develop smart communities with zero net emissions, and the Responsive Building Envelopes (RBEs) have a crucial role for the goal to be achieved. In this frame the smart windows are promising building envelope solution. With respect to conventional static windows, on one hand they could reduce the building thermal loads and therefore lead to an energy saving and to an improvement of the thermal comfort, on the other hand they could reduce the possible glare, improving the also the visual comfort. There are some smart windows based on widespread technologies and deepen investigated in the scientific literature, such as the electrochromic solution, but there are some others, such as liquid crystal devices, not really investigate, or characterized only by means of simulative analysis, often without calibrated models with experimental data. Thus, the present study aims to investigate, under experimental and numerical point of view, an electric-driven window with liquid crystal technology installed in a full-scale facility located in a Mediterranean climate. A calibrated numerical model is carried out and different windows control logics and future climate projections (to 2050s and 2080s) are analyzed. Among different control logics, the one depending on daylight illuminance level on the work plane shows the best performance, with a total energy saving (lighting and cooling) of -3% with respect a static window in clear state.

Parametric-Based Multi-Objective Optimization Workflow: Daylight and Energy Performance Study of Hospital Building in Algeria

Daylight is an important factor that significantly contributes to patients’ healing, with a reduction in the length of stay in the hospital. It can strongly affect energy consumption negatively or positively through lighting control strategies. Therefore, the case of healthcare buildings is very particular and sensitive, especially under extreme climate conditions as in hot and arid regions. The present study aims to determine a balance between daylight use and energy consumption through a parametric-based optimization of the external shading system in a typical hospital room in Biskra. This paper demonstrates how the implementation of parametric design with evolutionary algorithms is considered a reliable strategy to reach optimum solutions in building performance problems. The daylight performance is investigated based on multi-objective optimization to minimize the Energy Use Intensity “EUI”, while maximizing Spatial Daylight Autonomy “sDA” and Useful Daylight Illuminance “UDI”. A simulation model was developed via Grasshopper, which was employed with the use of Ladybug, Honeybee, and Octopus plug-ins. The results revealed that the adaptive facade system can improve indoor daylight levels and energy performance simultaneously compared to the conventional shading system. The presented framework may be used as a reference model, which can enhance opportunities to solve complex design problems in the early design stages and suggest recommendations for sustainable building design.

Energy Optimization for Fenestration Design: Evidence-Based Retrofitting Solution for Office Buildings in the UAE

With the prevalent use of large glazings, particularly in office buildings, offices receive an abundance of light and are among the largest consumers of electricity. Moreover, in an extreme hot arid climate such as in the UAE, achieving comfortable daylighting levels without increasing solar heat gain is a challenge, in which the window or fenestration design plays an essential role. This research adopts a case study of a higher education (HE) office building on the United Arab Emirates University (UAEU) campus, selected to investigate an evidence-based retrofitting solution for the west façade that can be applied in existing office buildings in the UAE in order to reduce cooling energy load as well as enhance indoor environmental quality. To achieve an evidence-based retrofitting solution, the research design built upon a comprehensive exploratory investigation that included indoor environmental quality physical monitoring and occupant satisfaction surveying. Model simulation was performed by means of DesignBuilder software to perform a single- and multiparameter sensitivity analysis for three key passive window design parameters, i.e., window-to-wall ratio, glazing type, and external shading, aimed towards minimizing annual cooling load and solar heat gain, while maintaining appropriate indoor daylight illuminance levels. The results highlight the importance of the window-to-wall ratio (WWR), as it is the single most significant parameter effecting total energy consumption and daylighting levels. The results recommend 20–30% WWR as the optimum range in the west façade. However, by utilizing high performance glazing types and external shading, equal energy savings can be achieved with a larger WWR. Double Low E tinted glazing and 0.4 projection shading overhang and side fin revealed a noteworthy reduction of energy use intensity of 14%. The study concludes with final retrofitting solutions and design recommendations that aim to contribute validated knowledge towards enhancing window performance in a hot arid climate to guide architects and stakeholders to apply a range of passive parameters towards reducing energy consumption and improving occupant comfort in office buildings.

Influence of Different Illuminants on Spectrophotometric Tooth Color Determination

Statement of problem: The vast majority of studies address the comparison of visual and instrumental tooth color determination. Although, the lighting conditions of the environment may affect the clinical shade matching performance. This study evaluated if and how different light sources can influence the spectrophotometric determination of natural tooth color. Purpose: The purpose of this study was to evaluate the precision of the spectrophotometer in tooth shade determination under the influence of different illuminants. Material and method: Three examiners, determined the shade of an upper central incisor with Vitapan 3D-Master (VITA Zahnfabrik, Bad Säckingen, Germany) and with the spectrophotometer (Vita Easyshade V, Vita Zahnfabrik, Bad Säckingen, Germany). A special fabricated device with eight light sources, designed to offer reproductible lighting conditions, was used to determine the efficiency of instrumental color determination under different illuminants. Results: Natural light (300 lux) and dental unit light at full intensity (32500 lux) produced the less ∆Eab modification. Color coordinates determined in the presence of halogen light (1800 lux), neon ambient light (3000 lux), LED with cold light (21200 lux), halogen light with neon ambient light (23400 lux), both warm and cold LED simultaneously (36000 lux) and all eight light sources of the device (44000 lux), suffered a slight modification of ∆E ab, which does not exceed the acceptability and the perceptibility threshold. The illuminant that caused the biggest modifications in color coordinates was LED warm light (1940 lux) with a ∆Eab 5.804 ± 0.271, that exceeds the acceptability and perceptability threshold. Conclusions: LED warm light influences the instrumental tooth color determination and when used, can lead to errors in communication of the color to the dental laboratory, which can cause esthetic failure of a prosthetic restoration. The best illuminant for color determination is natural light, or illuminants that simulate lighting in daily living conditions. Clinical implications: Based on the spectrophotometric readings, it was demonstrated that tooth color shifts with the change in ambient lighting conditions. Therefore, color determination should be performed with natural daylight illumination.

Calculation of energy saving potential for lighting with DIALux evo

This short communication reports on the implementation and validation of the three-phase method for daylight calculations in the freely available software DIALux evo. Compared to the previous approach to daylight calculation in DIALux, the 3-phase method allows for a faster calculation of yearly daylight illuminance without sacrificing accuracy. DIALux is one of the most widespread software among electric lighting designers. By implementing simple, accurate, and fast analysis, this new version of DIALux makes daylight analysis easily available to electric lighting designers. This can unleash the potential of properly integrated daylighting and electric lighting design, for better and more efficient lighting projects.

Exposure to artificial light-at-night and cardiometabolic health: an urban perspective from the Catalan GCAT cohort study

BACKGROUND AND AIM It has been suggested that artificial light-at-night (ALAN) exposure may lead to metabolic disturbances through circadian misalignment and sleep disruption. The present study investigated associations between residential outdoor ALAN exposure and cardiometabolic risk factors and disease outcomes. METHODS We used data from 9,752 participants (59% women) in the Genomes for Life (GCAT) cohort study in Barcelona. Residential ALAN was assessed from images of the International Space Station with a 30m resolution. We estimated the visually relevant photopic illuminance and the metabolic and circadian-regulation relevant melanopic equivalent daylight (D65) illuminance, in lux. We examined cross-sectional associations between ALAN and cardiometabolic risk factors (obesity, glycaemia and hypertension). During a mean follow-up time of 2.5 years (SD 0.97) we prospectively assessed, in 5,743 participants, incident diseases (angina pectoris, myocardial infraction, stroke, diabetes, hypercholesterolemia and hypertension) ascertained through electronic health records. We adjusted our main models for demographic characteristics and further adjusted for greenness density and air pollution. RESULTS In cross-sectional analyses we found an association between photopic and melanopic Illuminances and hypertension, OR = 1.15 (95% CI 1.03-1.29) and 1.58 (1.08-2.32), per unit increase; associations remained stable after adjusting for other urban exposures. The association between illuminances and obesity was less consistent across adjustments. In incident analyses, photopic and melanopic illuminances were associated with hypercholesterolemia, OR = 1.94 (1.06-3.55) and OR = 1.30 (1.09-1.55), respectively. We had limited power, due to few incident cardiovascular events, and did not observe an association between ALAN and cardiovascular diseases nor diabetes. CONCLUSIONS The present study suggests an association between photopic and melanopic illuminance at night and risk of hypertension and hypercholesterolemia, key risk factors for cardiometabolic diseases. Results should be interpreted carefully since satellite-based ALAN assessment, even in high resolution, estimates individual exposure only partially. KEYWORDS Light-at-night, circadian misalignment, hypercholesterolemia, hypertension, cardiovascular, obesity

Nonvisual aspects of daylight in the built environment

This paper investigates melanopic equivalent daylight vertical and horizontal illuminances within an indoor space as a metric for the nonvisual effects of its lighting. The article is based on the findings of photobiological research and the recommendations of several institutions for the threshold values of melanopic illuminance at the eyes of users of indoor spaces, which is sufficient for the proper functioning of the circadian system. This study uses a computer workplace as an environment to investigate experimentally the applicability of melanopic daylight metrics for the practical evaluation of the circadian potential of the indoor daylight environment. The article points out a number of problems associated with the practical evaluation of vertical melanopic daylight illuminance in a specific space. The paper also outlines practical guidelines for designing facades and color treatment of building surfaces in terms of their circadian potential.

아랍 에미리트에 위치된 소규모 사무실 공간의 주광조도와 오버행 깊이의 상관성 분석

This study proposes the distribution of indoor daylight illuminance that changes according to the depth of the overhang applied to the office space in Dubai. The effect of overhang depth to indoor daylight illuminance in an office space located in Dubai region was predicted based on the simulation using the Radiance. Three depths of overhang were applied to the south-facing space under clear sky conditions and simulations were conducted on a hourly basis for three representative days of year. The linear relationship between overhang depth and indoor daylight illuminance were analyzed. The relationship between them were strong and prediction model for them were meaningful under a significance level of 0.05. In March and December, the daylight illuminance reduced as the depth of overhang increased. In June, the overhang depth has no effect on the indoor daylight illuminance.

Parametric Design and Spatial Optimization of East–West-Oriented Teaching Spaces in Shanghai

The goal of the current study was to determine the appropriate spatial shapes for classroom occupants while saving energy. The research used parametric design and Genetic Algorithm (GA) to achieve this. Four recognized performance indicators, Energy Use Intensity (EUI), Useful Daylight Illuminance (UDI), Daylight Factor (DF), and Daylight Autonomy (DA), were used as the evaluation indexes for the research. The tests took place in six east–west-oriented classrooms at Shanghai University, China. The methodology was based on four steps: (1) parametric 3D modeling by Rhino and Grasshopper; (2) using building performance simulation tools; (3) running algorithm optimization; (4) outputting the useful results. The results proved that the methodology worked successfully in reducing energy consumption: optimized classrooms could be reduced by 7.5~14.5%, and classrooms with east directions were generally 4.8~8.3% more efficient than west-facing ones. The indoor lighting environment was also significantly improved, being slightly better than north–south-oriented classrooms in terms of the UDI index (60~75%) and inferior (but still high) in terms of the DF (4.0~7.0%) and DA (60~80%) indexes. The conclusion can help save design time in the early design process of teaching spaces.

Preserving High‐Q Lattice Plasmon Resonances for Poor Spatial Coherence of Light: Application in Enhanced Second Harmonic Generation

AbstractSurface lattice plasmon resonances (SLPR) in periodic arrays of metal nanostructures can feature a narrow spectral linewidth in case of the spectral overlap between the localized plasmons and Rayleigh anomalies. However, because of strong angular dispersion in experimental realizations, the excitation of SLPR requires collimated light, which has high spatial coherence. Here, excellent quality (Q)‐factor preservation in 1D all‐metallic nanograting metasurfaces due to the unique angular dispersion is reported. A high Q‐factor around 400 is obtained even when poor collimation, a numerical aperture (NA) objective with NA = 0.4, is employed for focusing the excitation light. With the advantages of highly focused excitation and high Q‐factor of the SLPR, a strong enhancement of second harmonic generation is realized from the proposed metasurface integrated with a few‐layers of GaSe flake. The results demonstrate that a 1D all‐metallic nanograting metasurface can overcome the demand for collimated light for the SLP resonances and manipulate focused light beams. The avenue of research proposed in this paper can open the door for the use of plasmonic metamaterials with SLPRs in many practical applications involving poorly coherent light sources, like the optoelectronic devices utilizing solar and daylight illuminations.

The optimization of louvers shading devices and room orientation under three different sky conditions

This paper presents parametric and multi-objective optimization (MOO) approach in optimizing daylight and energy consumption by incorporating louvres shading devices depicting three different sky conditions: Birmingham, UK, Jakarta, Indonesia, and Sydney, Australia. The study aims to observe the best louvre design configuration for each given context. The proposed optimization system iterates the logic of the louvre shading device as the dynamic design parameters such as overhang, blade size, spacing, and blade rotation, together with the room orientation to achieve maximum useful daylight illuminance (UDI) and the shading aperture while simultaneously reduces energy consumption. A total of 8509 simulations for three cities have been run and distributed for the purpose of this research. The results of MOO stated an improvement in UDI for Birmingham, Jakarta, and Sydney of 80%, 146.26%, and 79.48%, and cooling energy consumption of 28%, 3.26%, and 2.99% respectively.

Multi-objective optimization of energy, visual, and thermal performance for building envelopes in China's hot summer and cold winter climate zone

The building envelope design parameters including windows, apertures, shading, and materials have a significant interactive impact on the performance of a building. However, few studies simultaneously optimize these parameters to determine the trade-off solutions between energy consumption, indoor daylighting, and thermal comfort. This study presents a multi-objective optimization (MOO) framework evaluating Useful Daylight Illuminance (UDI), Energy Use Intensity (EUI), and Thermal Discomfort time Percentage (TDP) with a wide range of parameters to investigate the interactive relationships between multiple building design and performance parameters. The openable-window-area-ratio (OWR), window-wall-ratio (WWR), solar-heat-gain-coefficient (SHGC), louver depth, and wall thickness are integrated into the optimization process. Taking a building in the Hot Summer and Cold Winter Zone as an example, the results show that a large south-openable-window-area-ratio (OWRs), south-window-to-wall-ratio (WWRs), SHGC, and wall-thickness with a small north-window-wall-ratio (WWRn) and louver depth are most suitable for improving energy performance without sacrificing thermal and visual comfort. The trade-off solution represents noticeable improvements by 18%, 48.4%, and 2.5%, respectively, compared with the initial solution in EUI, TDP for the transition seasons, and UDI. The outcomes help the architects to obtain an optimal solution for the design, refurbishment, and renovation of building envelopes in the HSCW zone towards the construction of sustainable cities.

Application of artificial neural networks in horizontal luminous efficacy modeling

Harnessing daylight for energy-efficient designs requires the availability of daylight illuminance data. In the absence of measured daylight data, deriving daylight using the luminous efficacy model is an alternative. This paper presents an approach for modeling diffuse and global luminous efficacies using accessible measured climatic data. The methodology explored machine learning, sensitivity analysis and empirical modeling approaches. Twelve (12) luminous efficacy models were proposed. These models consisted of six artificial neural networks (ANN) and six empirical models. All models also cover the all-sky, overcast and non-overcast sky conditions. The intent of using ANN lies in the need for more accurate daylight predictions and its ease in explaining complex relationships between complex atmospheric variables. Findings from the study show that diffuse fraction is crucial in global and diffuse luminous efficacy modeling. Furthermore, the performance of all models was statistically assessed, and the results show that all twelve proposed models could offer acceptable predictions of daylight. In particular, the ANN models outperformed the empirical models.

Influence of evening light exposure on polysomnographically assessed night-time sleep: A systematic review with meta-analysis

Evening exposure to electric light can acutely suppress melatonin levels and adversely affect subsequent sleep. We conducted a systematic review with meta-analysis investigating the influence of evening illuminance levels on polysomnographically (PSG)-assessed sleep. We also explored how melanopsin (expressed in melanopic equivalent daylight illuminance (EDI) affects human sleep features. We included polysomnographic laboratory sleep studies with healthy humans for effects of illuminance and exposure duration, for pre-sleep exposures between 6:00 p.m. to 1:00 a.m. From 440 identified articles, 114 met eligibility criteria for screening, and 21 also reported type of light source/spectral characteristics, with 12 identified as eligible for review. Meta-analysis showed evening light affects sleep latency, sleep efficiency and slow wave sleep, with overall effect sizes (95% confidence interval) of 0.69 (−0.50; 1.88), 0.34 (−0.13; 0.82) and −0.61 (−1.85; 0.62), respectively. Estimated melanopic EDI in the range of 100–1000 lx yielded clear dose–response relationships for sleep latency and sleep efficiency, but not for slow wave sleep. Whilst illuminance and duration indicated no apparent effects for a single evening light exposure on PSG-assessed sleep latency, sleep efficiency and slow wave sleep, we observed evidence for a relationship between light exposure and sleep effects based on melanopic EDI. Hence, melanopic EDI may provide a robust predictor of non-visual responses on human sleep.

Charge collection efficiency study on neutron-irradiated planar silicon carbide diodes via UV-TCT

The material properties of silicon-carbide (SiC) make it a promising candidate for application as a particle detector at high beam rates. In comparison to silicon (Si), the increase in charge carrier saturation velocity and breakdown voltage allows for high intrinsic time resolution while mitigating pile-ups. A larger bandgap and higher atomic displacement threshold energy suppresses dark current and potentially improves radiation hardness, respectively. In addition to the lower susceptibility to temperature variations, it allows the operation of irradiated devices at room temperature and daylight illumination. Although already known for several decades, recent developments in industrial power electronics made SiC more accessible as a potential particle detector. Repeatability, large amplitudes and timing possibilities of signal pulses produced by the ultraviolet transient current technique (UV-TCT) allow for precise performance comparison of differing samples, while efficiently monitoring the influence of alternating external conditions. We present measurement results on the performance of neutron irradiated 4HSiC p-on-n planar diodes using such a setup. Dark current levels remain in the nA range for all fluences (5×1014neq/cm2−1×1016neq/cm2), while charge collection efficiency decreases with irradiation fluence, partially compensated when operating samples at reverse voltage conditions far above full depletion.

Comparison of Daylight Performance in Three Different Sky Conditions for Various Window Shading Types

Building sector contributes 40% of total energy consumption. In line with this, passive design strategy should be taken as an essential consideration to bring occupants comfort both thermally and visually. Besides, related to human health, one of the factors that the designer is encouraged to fulfill is the proportional amount of daylight that penetrates the building’s room. The passive strategy to optimize the daylight performance can be approached both from the building orientation and the shading system. This paper will computationally compare the different shading systems from vertical and horizontal louver, perforated metal sheets, and expanded metal shading, aiming to investigate the desirable shading-related design solution for the given condition. The simulated room is virtually situated in three different sun positions: Birmingham, United Kingdom, Jakarta, Indonesia, and Sydney, Australia. The metrics used in this experiment are Useful Daylight Illuminance (UDI). The Rhinoceros and Grasshopper were used to model the intended simulated room, while Ladybug and Honeybee were used to undergo environmental analysis. The results show that the vertical louver LV performs better in the three regions than the rest three compared shading. The experiment results are expected to give an overview which of which is fit for the situation.

Design of thermo-chromic glazing windows considering energy consumption and visual comfort for cellular offices

Optical behavior of thermo-chromic glazings can be modulated with changing temperature based on phase transmission of embedded pigments. Such pigmented glazings can be used in residential or office windows to alter visible and solar transmittance of the window, based on environmental conditions. This study focuses on numerical design of thermo-chromic glazings with V O2 pigments used in office buildings so that energy consumption can be minimized, while considering visual comfort. Optical properties of pigmented glazing depends on pigment radius, volume fraction and glazing thickness. In this study, two main design variables that are pigment radius and volume fraction are examined by applying parametric analysis for a constant glazing thickness that is identical to a standard ordinary glass. The radiative transfer through glazings are solved using four flux method to predict the optical properties of the glazings. The optimum thermo-chromic glazings are identified and energy efficiency along with resulting daylight illuminance are compared with that of an ordinary double glazing for several geographical locations. It is observed that thermo-chromic windows for office buildings have significant energy saving potential which can lead decreases in energy consumption from 17% for cold climates to 42% for hot climates.

Impact of Different Shading Devices on Daylight Performance and Visual Comfort of A Four Opening Sides' Reading Room In Rasht

Daylighting has become an essential feature in libraries since it can boost productivity, well-being, and energy savings. It is crucial to prevent discomfort glare irritation while maintaining the quality of view, and daylight demands. This study compares four different shading systems on all fronts of a reading room. Shading devices include a Perforated Solar Screen (PSS), besides three Venetian Blinds typologies (exterior, interior, and exterior integrated with overhangs) are generated considering various parameters. The 60-min time step for an entire year is used to find out the worst dates for glare analysis in different positions for Rasht, Iran. The findings of Daylight Autonomy (DA), Useful Daylight Illuminance (UDI), Daylight Glare Probability (DGP), and Quality of View (QV) depict that PSS is ineffective at glare reduction but is adequate for annual metrics and view quality. Moreover, Venetian Blinds in every three typologies are sufficient to deal with glare problems on most dates, despite differences in their characteristics being reported. Annual metrics and Quality of View in these cases, depending on variables, are changeable.

Photocatalytic performance of N–TiO2@SiO2 composite obtained under gliding arc plasma processing at atmospheric pressure

Photocatalysis is becoming ubiquitous in the chemical industry because of its positive impact on the cost of operations. Nevertheless, a good photocatalyst must meet the properties of good reactivity, high selectivity, long-term stability, low toxicity, and cost-effectiveness but should also promote a photo-generated charge carriers separation. In this work, a homemade supported catalyst is obtained through low-temperature plasma exposure of the precursor TiCl3/glass powder to promote better handling, high particle dispersion, and easy recovery. Because such a plasma is a strongly oxidative medium containing mainly radicals (•OH and NO•), the mixture exposition induces the formation of N–TiO2 nanoparticles immobilized in-situ onto the glass matrix to form a photo-active hetero-structure that improves the charge carriers separation overcoming the rapid recombination drawback. The resulting material was characterized by XRD, FTIR, and SEM techniques. The resilient stability after 5 successive cycles, makes this composite a promising alternative photocatalyst for various applications. The photocatalytic degradation yields reached 52, 72, 60, and 80% within 1 h of plasma irradiation and 45, 43, 22, and 25% after 6 h of daylight illumination, respectively for Rhodamine 6G, Floxina B, Ceftriaxone, and Ampicillin. The discrepancy in degradation yields is more related to the intrinsic chemical structure of each contaminant.

The Effect of Smart Colored Windows on Visual Performance of Buildings

The photochromic coating is a promising smart technology that provides different optical properties in response to daylight variations. The application of photochromic coatings with various colors/shades on window glass is one of the current research approaches for finding better energy saving techniques. The aim of this study was to develop a series of photochromic coatings for window glass and measure the impact of such smart technologies on occupants’ visual comfort. This paper examines the visual performance of building facades that utilize windows with different photochromic-coated glass. The visual performance data of three window types coated with nine different photochromic color shades were considered and compared to determine the best photochromic shades and window types that provide optimum visual metrics for the inside of the building. The results show that compared to no-coating glass, both the Daylight Glare Probability and the Useful Daylight Illuminance could be improved by using multi-color coatings that contain equal or different color proportions for photochromic window glass. From an energy-saving point of view, the results indicate that the windows coated with photochromic materials provide a better alternative to the no-coating window products.