Indoor Illumination Level Research Articles

POLarizer-FENestration (POLFEN) a novel concept of a glazing technology to modulate daylighting and glare in buildings

A conceptual new window/glazing technology called POLarizer-FENestration (POLFEN) is presented. In 1935, Edwin Land's pioneering work on polarizers successfully developed a sheet polarizer that was used in various applications. Subsequently, polarizers were employed in windows to modulate daylight and reduce associated glare. Early prototype windows were circular in shape so that the polarizing filter could be rotated to modulate the daylight. However, compared to rectangular-shaped windows that are ubiquitous, circular windows are rare in buildings. Therefore, a new window/glazing technology, discussed in this paper, was developed that utilizes a polarizing film in a conventional rectangular or square window, arranged in the form of strips or a checker-grid over the window panes to modulate daylighting levels and control glare. In this new research, a working prototype of the glazing technology is developed and demonstrated including simulations using the Radiance daylighting simulation software. In the current work, two types of measurements were taken: photographs of the indoor luminous environment and illumination levels (Lux) at selective points on the work-plane both in a physical prototype as well as in the simulation model under two sky conditions: CIE clear sky with sun, and overcast sky. The results indicate that the new glazing technology resulting from this concept can effectively modulate daylighting levels, minimized associated glare to an acceptable level while maintaining a view to the outdoor environment. The technology can be classified as Variable Transmission Glazing (VTG), similar to Electrochromic (EC) glazing since it also offers a dynamic modulation of solar optical properties (Tvis).

Effects of latitude and building orientation in indoor-illuminance levels towards energy efficiency

As a matter of concern in sustainable buildings, daylight is studied to improve the balance between visual comfort for the occupants and energy consumption. This study analyzed the effects of latitude and orientation on the sunlight illuminance level within a northwest/southeast-oriented hypothetical house, with a wide-glassed façade, by integrating the BIM and BEM methodologies. The house was located in five different locations showing different latitudes: Búzios, Brazil; Capri, Italy; Punta Cana, Dominican Republic; Dubai, United Arab Emirates; and Sydney, Australia. Five different studies were carried out for each one of them by using the Autodesk REVIT energy-analysis tool named Lighting; they included sun-path analysis, calculation of daylight factor and daylight autonomy, and evaluation of daylight illuminance levels. It was found that a high amount of sunlight enters the house on its rear side, where are located the most occupied rooms, predominantly in the summer season, in the afternoon hours; however, 67% of the total house is below the 2% of daylight factor threshold. Withal, the rear-side rooms are the ones that satisfy most of the time with illumination levels above 300 lux, with maximum levels varying according to the season. This research contributes to associating BIM and BEM methodologies as an option to improve the design of energy-efficient buildings, being possible to consider further improvements to enhance the illuminance in the rooms, both for the early design stages and for future retrofit plans.

PO-04-214 VIDEO-BASED FACIAL DETECTION OF ATRIAL FIBRILLATION ACROSS HUMAN COMPLEXIONS

It has been posited that the Black vs. White disparity in stroke risk may be partly attributable to the relative underdetection of AF in Black compared with White patients. We propose a novel monitoring solution that could minimize the impact of the socio-economic disparities in access to remote monitoring solutions. We developed a video-based monitoring technology to detect AF without the need for a patient to adopt a dedicated wearable device. It is a low-cost software-only solution running on smartphones. It eliminates requirements for patient compliance with recording procedures since it passively monitors patients while they are using their smartphones for other purposes. The technology captures a pulsatile signal from patients' faces. Remote video-based cardiac monitoring measures the modulation of ambient light reflected from one’s face due to changes in blood volume (hemoglobin) in the upper layers of the skin. In addition to hemoglobin, melanin is also a chromophore of the human skin. Hence, we aim to measure the accuracy of the technology to measure heart rate (HR) and its performance to detect the presence of AF across the whole spectrum of human complexions. We enrolled patients with paroxysmal and persistent AF. We defined 3 complexion groups using the Fitzpatrick score: white (A), tanned and olive-color (B), brown and black (C). Measurements were conducted under 4 indoor illumination levels: 50, 100, 200, and 500 lux. For reference, we used a single-lead EKG. We used 25% of the cohort to train the technology. HR accuracy was assessed using the Bland-Altman method with paired replicate measures based on one-way repeated ANOVA. The detection performance was measured as average sensitivity (SENS) and specificity (SPEC) adjusted for repeated measures. We collected 7,042 recordings from 60 AF patients (67±10 yrs, 44 men). We enrolled 23, 26, and 11 patients in the complexion groups A, B, and C, respectively. In the validation, 87% of the recordings were conclusive. Overall SENS and SPEC were 96% and 92%. For an illumination >50 lux, the SENS and SPEC for the complexion groups were: [A: 99%,94%], [B: 91%,93%], [C: 96%,90%]. The mean HR measurement errors in reference to the EKGs were: [A: -2.0 bpm], [B: -0.2 bpm], and [C: 0.3 bpm] with limits of agreements <5 bpm (upper to lower bound intervals). The proposed monitoring technology enables an accurate measure of HR and the detection of AF across all human skin complexions and under indoor illumination.

Post Occupancy Evaluation of the Luminous Environment in Algerian University Classrooms

The luminous environment is one of the most important physical parameters in a teaching space (classroom) due to its impact on the intellectual performance of students, their health and their behavior. The aim of this study is to evaluate the luminous environment in university classrooms located in Constantine, the main university hub of the East of Algeria. A Post Occupancy Evaluation (POE) based on the objective and subjective assessment was carried out at the Department of Psychology of Constantine 2 University in North and West facing classrooms. This study was conducted during the three periods: winter, spring and summer, under clear sky and overcast sky conditions. The objective variables measured by a luxmeter during each course session are: indoor illuminance levels (Ei) on work plan, vertical illuminance levels on boards (Ev), uniformity index (Uo) and outdoor illuminance levels (Ex). At the same time, students perception and satisfaction were reported by a longitudinal questionnaire (N=1221) using subjective scales. The objective assessment shows that the mean interior illuminance is dependent of the sky-type, and it varies with outdoor illuminance. We notice that illuminance levels in north classroom are below the recommended value especially under overcast sky. The illuminance levels in west facing classroom are excessive during the afternoon under clear sunny sky. However, students show a remarkable degree of adaptation to different light levels. They use controls to modify the light level at their work plans.

Illumination and Lighting Energy Use in an Office Room with a Horizontal Light Pipe: Field Study at a High Latitude

This paper describes a field study of the illumination and lighting energy use in a full-scale test office in a building located in southern Norway. Natural light is provided to the office via southwest-oriented windows and a horizontal light pipe (HLP) with a daylight entrance facing the south. The study is a full-scale field study, and it is a continuation of the recently published study addressing a scale model and a theoretical model. The novelty of this study is a custom-made reflector for the HLP’s daylight distribution to preserve the features of natural light noted as the primary human association with daylight. The main research aim was to determine if the daylighting level in the back of the office was improved as a consequence of the daylighting provision from the HLP compared to a reference situation without a HLP, as well as whether the lighting energy use for the electric lighting system that was supposed to provide the recommended light level was reduced. This study includes monitoring of the outdoor and indoor illuminance levels as well as the energy consumption of the luminaires throughout the study’s test period and a corresponding reference period. The recorded data were used to test hypothesis applying inferential statistical analyses. In conclusion, this paper reports an increased daylight level on the working area in the rear part of the office of approximately 200 to 300 lx during clear and sunny days at equinox. The increased daylight level on the working area near the window of approximately 50 lx was also recorded. These findings have important implications for energy balance in the Zero Energy Buildings (ZEB) and the ‘peak load’ for energy consumption.

Performance of Solar Control Films on Building Glazing: A Literature Review

Buildings with a high window-to-wall ratio tend to suffer from excessive solar gains/losses that usually result in high energy demand and discomfort for occupants. Solar control films (SCFs) are a passive solution with the potential to increase the performance of new or refurbished glazing they are applied to. This paper presents a comprehensive literature review of the performance of SCFs applied to glazing systems of buildings. Research studies with experimental, analytical and computer simulation approaches were gathered and analyzed, identifying glass and film systems, climatic conditions, energy savings and comfort performance. The research approaches and main findings of existing research studies were compared and discussed. The presence of SCFs significantly reduced indoor solar radiation and illuminance levels, particularly with reflective films applied to south-oriented glazing (northern hemisphere). Glazing systems with SCFs were reported to promote cooling energy savings compared with clear glazing in hot climates. Few studies have explored the visual and thermal comfort performance of SCFs, concluding that these films promote thermal comfort, and reduce excessive illuminance and potential glare. Furthermore, this paper helps to highlight areas of guidance for future studies on the topic.

Adjustable Internal Shading for Home Office Daylighting in Tropical Climates

Home-based workspaces have considerably increased all over the world. Besides, the recent outbreak of the COVID-19 disease forced many people to work from their homes. However, existing residential apartment buildings (ERABs) had been designed for accommodation but not for office works. Low-quality visual environments in ERABs, which have no shading controls on their windows, are evident in tropical climates with extremely high solar radiation. Thus, interior retrofit is significant to provide visual comfort for users in ERABs with low flexibility for modification of their facades. Different interior design variables were simulated by the Radiance-based program to analyse daylighting in a closed-plan room. Before the simulation experiments, field measurement of daylight was performed under a tropical sky to validate the results, and the findings revealed significant Pearson correlations. This paper showed that ERABs are confronting extremely high indoor daylight quantity, up to 10,228 lx, and low quality with intolerable glare. An adjustable model of internal shading, including an integrated Venetian blind with a horizontal light shelf and the window films, was proposed to improve quantitative and qualitative performances of daylighting in tropical regions. This dynamic model could be adjusted to various positions based on daylighting conditions in the buildings. By comparing the simulation results of this model with the base model, indoor illuminance levels could successfully reduce from 32% to 86%; Illuminance Uniformity Ratio (IUR) and Target Daylight Illuminance (TDI) significantly improved up to 180% and 300%, respectively; Daylight Glare Probability (DGP) and CIE Glare Index (CGI) changed from intolerable to imperceptible status. Accordingly, the proposed model can considerably improve daylight quantity and quality in the test room during different times. This study concludes that the dynamic model of internal shadings could provide efficient daylighting, by decreasing the extremely high indoor illuminance and glare in the ERABs in tropical climates.

Agile reactive navigation for a non‐holonomic mobile robot using a pixel processor array

This paper presents an agile reactive navigation strategy for driving a non-holonomic ground vehicle around a pre-set course of gates in a cluttered environment using a low-cost processor array sensor. This enables machine vision tasks to be performed directly upon the sensor's image plane, rather than using a separate general-purpose computer. The authors demonstrate a small ground vehicle running through or avoiding multiple gates at high speed using minimal computational resources. To achieve this, target tracking algorithms are developed for the Pixel Processing Array and captured images are then processed directly on the vision sensor acquiring target information for controlling the ground vehicle. The algorithm can run at up to 2000 fps outdoors and 200 fps at indoor illumination levels. Conducting image processing at the sensor level avoids the bottleneck of image transfer encountered in conventional sensors. The real-time performance of on-board image processing and robustness is validated through experiments. Experimental results demonstrate the algorithm's ability to enable a ground vehicle to navigate at an average speed of 2.20 m/s for passing through multiple gates and 3.88 m/s for a ‘slalom’ task in an environment featuring significant visual clutter.

In-Service Thermal and Luminous Performance Monitoring of a Refurbished Building with Solar Control Films on the Glazing System

The global increase in energy needs and environmental awareness for a more efficient energy use have boosted building rehabilitation to decrease energy consumption. The installation of solar control films (SCFs) in buildings with large glazing façades makes it possible to reduce excessive solar gains through the glazing. The main purpose of the work is to assess, with field experimental data, the thermal and luminous performances of double-glazing units with SCFs installed in office rooms, in Lisbon. An experimental campaign was carried out simultaneously in three adjacent offices: one with a highly reflective SCF (external installation), one with a reflective SCF (internal installation) and one without an SCF. The exterior SCF showed the best thermal performance with reductions in the peak indoor air temperature of up to 6.9 and 2.3 °C during the representative days of the heating and cooling periods, respectively, increasing thermal comfort mainly during the cooling period. The interior SCF had a poorer thermal performance since it contributed to solar radiation absorption that is then emitted as heat into the indoor environment, increasing the greenhouse effect of the office. The presence of SCFs reduced the indoor illuminance levels, having a positive impact on thermal comfort and glare reduction in the cooling period.

On the Performance of the Two-Diode Model for Photovoltaic Cells Under Indoor Artificial Lighting

Models of photovoltaic devices are an important tool for the estimation of their I-V characteristics. These characteristics, in turn, can be used to optimize production, compare devices, or predict the output power under different illumination conditions. Equivalent circuit models are the most common model types utilized. Although these models and the estimation of their parameters are thoroughly investigated, little is known about their performance under indoor illumination conditions. This, however, is essential for applications where photovoltaic devices are used indoors, such as for PV-powered sensors, wearables or Internet of Things devices. In this paper, a comprehensive and quantitative study of parameter estimation methods for the two-diode model is conducted, focusing particularly on the performance at indoor illumination levels. We reviewed and implemented a set of six common parameter estimation methods, and evaluate the performance of the estimated parameters on a typical photovoltaic module utilized in indoor scenarios. The results of this investigation demonstrate that there is a large performance variation between different parameter estimation methods, and that many methods have difficulties to estimate accurate parameters at low illumination conditions. Moreover, the majority of methods result in physically infeasible parameters, at least under some of the evaluated conditions. When applying physically motivated parameter scaling methods to these parameters, large estimation errors are observed, which limits the model’s applicability for power estimation purposes.

VLC Using 800-μm Diameter APD Receiver Integrated in Standard 0.35-μm BiCMOS Technology

The fully integrated 800 μm. diameter avalanche photodiode optical receiver is implemented in 0.35 μm BiCMOS technology without any process modifications. The integrated receiver reaches sensitivities of -33 dBm at 1 Gbit/s and -29.3 dBm at 2 Gbit/s. The reached sensitivities are well within the state-of-the-art of integrated avalanche photodiode receivers and can even be compared to a hybrid avalanche photodiode receiver comprised of high-performing commercial components. The performance of the designed receiver was verified in visible light communication experiments. The receiver could reach up to 16.5 m at 2 Gbit/s and 27 m at 1 Gbit/s of error free transmission distance using a 675-nm point laser source as transmitter. The common indoor illuminance levels up to 500 lux could be tolerated when pointed directly towards the receiver. High sensitivity and high speed make this integrated receiver suitable for future optical wireless communication systems, where due to its integrated nature the manufacturing cost can be lowered, and at the same time the design is compact in size and easy to assemble and scale. Furthermore, no optics is used in front of the receiver due to its large area resulting in a wide field of view.

Co-simulation and validation of the performance of a highly flexible parametric model of an external shading system

The article presents a validation study of a modelling approach implemented in a numerical script for external louvred shading systems based on an experimental analysis in a full-scale test facility. The model developed to abstract the system was entirely parametric and used co-simulation to predict the indoor air temperature and illuminance levels in two points of the test cell.The calibration of the model of the test facility was carried out using a combination of two methods: automated calibration based on multi-objective optimization with a genetic algorithm and manual calibration. In total, six different configurations of the external shading system with varying complexity were investigated to validate the script. Its performance was assessed using three metrics: the root mean square error, the coefficient of variation of the root mean square error, and the normalized mean bias error.The results showed that the thermal environment was simulated with consistent accuracy for all the cases investigated, predicting air temperatures with an error well within the tolerance of building performance simulation tools and the experimental uncertainty. The daylighting model satisfactorily captured the different dynamics of illuminance peaks and dips, replicating the variations between different configurations, but with a lower degree of accuracy than for the thermal simulations.

Daylighting Performance of Solar Control Films for Hospital Buildings in a Mediterranean Climate

One of the main retrofitting strategies in warm climates is the reduction of the effects of solar radiation. Cooling loads, and in turn, cooling consumption, can be reduced through the implementation of reflective materials such as solar control films. However, these devices may also negatively affect daylight illuminance conditions and the electric consumption of artificial lighting systems. In a hospital building, it is crucial to meet daylighting requirements as well as indoor illuminance levels and visibility from the inside, as these have a significant impact on health outcomes. The aim of this paper is to evaluate the influence on natural illuminance conditions of a solar control film installed on the windows of a public hospital building in a Mediterranean climate. To this end, a hospital room, with and without solar film, was monitored for a whole year. A descriptive statistical analysis was conducted on the use of artificial lighting, illuminance levels and rolling shutter aperture levels, as well as an analysis of natural illuminance and electric consumption of the artificial lighting system. The addition of a solar control film to the external surface of the window, in combination with the user-controlled rolling shutter aperture levels, has reduced the electric consumption of the artificial lighting system by 12.2%. Likewise, the solar control film has increased the percentage of annual hours with natural illuminance levels by 100–300 lux.

Daylight luminous environment with prismatic film glazing in deep depth manufacture buildings

In this paper, indoor illuminance distributions with a microstructured prismatic film glazing in a deep depth manufacture space were measured. The measured illuminance data with the prismatic film glazing were compared to Radiance simulation results with a conventional glazing. This study shows that using prismatic film glazing at side windows can improve indoor illuminance levels and illuminance uniformity for inner spaces. The technology can work effectively for deep depth manufacture spaces under a clear sky but less effective under an overcast sky for improving illuminance levels and illuminance uniformity. Luminance image and glare metrics were also compared between the prismatic film glazing and conventional glazing. The angle-dependent transmittance properties of light-scattering for the prismatic films with direct sunlight present a different luminance pattern from the conventional glazing with higher peak luminance values but smaller peak luminance areas. In general, the simulated glare metrics with the prismatic film glazing presented lower DGP and DGI glare index than those with the conventional glazing. The time and orientation which may cause high glare metrics and possible discomfort glare with the prismatic film glazing in the deep depth manufacture space are also discussed.

Joint data transmission and dimming control optimization for MIMO–VLC systems with channel-adaptive spatial constellation design

In the field of indoor wireless communications, visible light communications (VLCs) have attracted great attention for synergistically providing both illumination and data transmission. Meanwhile, multiple-input multiple-output (MIMO) technique has been applied in VLC systems to boost data rate by utilizing spatial resources. However, different geometrical locations of transceivers provide distinct optical channels which may effect the performance of the conventional MIMO–VLC techniques severely. In this paper, we propose the channel-adaptive spatial constellation (CASC) design for the MIMO–VLC systems by fully taking advantage of the channel state information (CSI), where the optimal transmitted signal constellation can be constructed via maximizing the minimum Euclidean distance (MED) of the received signal constellation. Meanwhile, the practical lighting constraints are taken into consideration with the non-linearity characteristic of light-emitting diode (LED) and the dimming requirements to maintain a specific indoor illumination level. Finally, simulations results indicate that the proposed CASC design can achieve significant improvement of error performance compared with the conventional MIMO–VLC schemes.

Comparative investigation on building energy performance of double skin façade (DSF) with interior or exterior slat blinds

Advanced passive control technologies attract a great deal of attention by architects and engineers as a way of achieving both high indoor environmental quality and energy efficient buildings. This study investigates the thermal and daylighting effects of a double skin façade (DSF) system with interior and exterior blinds. A buffer type DSF and slat type blinds are used for this comparative study. To investigate thermal and daylighting effects of three passive control models, evaluation of annual heating, cooling, and lighting loads is conducted using a widely-accepted whole building energy modeling program, EnergyPlus. A simulated DSF model is developed using the air-flow network (AFN) model in EnergyPlus and calibrated against measured data from an experimental DSF facility installed to an office building in Daejeon, South Korea. After a proper calibration of the simulated DSF model, the impact of blinds in the cavity of the DSF is also evaluated by adopting a slat blind model in EnergyPlus. For exterior and interior blind models, the simulated DSF model is modified by removing a DSF box and adding slat blinds at inner and outer surfaces of the windows. A Radiance-based daylighting simulation program, Daysim, is used to evaluate daylighting aspects of blinds and lighting controls within an office building with simulated DSF, interior blind, and exterior blind models. Generated lighting and blind raise/lower control schedules from Daysim are used as input values in EnergyPlus for annual thermal and lighting load calculations. In addition, the impact of natural ventilation to reduce trapped hot air within the cavity of the DSF box is considered in this study during a cooling period only for the DSF model. Results indicate that the simulated DSF model can save up to 40%, 2%, and 5% for heating, cooling, and total loads, respectively, when compared to the baseline (i.e., no passive technologies) without any blinds or controls. With the combination of the daylight-based dimming control based on the indoor illuminance levels and the blind raise/lower control, the simulated DSF and the exterior blind models could potentially reduce the building thermal loads and lighting energy consumption by around 27–52%., respectively.

Daylight illuminance with prismatic film glazing in a factory building

Prismatic film glazing has the potential to improve indoor illuminance levels and uniformity. Indoor illuminance distributions with prismatic film glazing in a manufacture building were measured. The measured illuminance data with prismatic film glazing were compared to Radiance simulation results with conventional glazing. This study shows that using prismatic film glazing at side windows can improve indoor illuminance levels and illuminance uniformity for inner spaces. The technology can work effectively for large depth spaces under sunny sky but only has slightly better performance under overcast sky.

DAYLIGHT CHARACTERISATION OF CLASSROOMS IN HERITAGE SCHOOL BUILDINGS

This paper studies the daylight characteristics in selected high schools that are located in heritage-listed buildings. Heritage buildings were selected in this research due the problematic condition regarding the indoor illumination level after being adaptively reused. Based on the previous research, lighting in educational institution is a critical factor because poor lighting not only isdetrimental to the occupants’ visual comfort but also might lead to visual fatigue. To achieve the objectives of this paper, daylight level measurements and observation were conducted. The results show that the daylight that penetrates into the classrooms were below the standard due to many obstructions founded in both schools. Artificial lightings were used as a supplementary during thewhole school hours since the daylight was not uniformly distributed. Thus it can be concluded that the inappropriate adaptive reusing heritage building indoor is significantly affecting the indoor light level and might lead to visual discomfort issues for students. The research findings as well as the suggestions have been delivered to the school management to overcome the issues founded.

DAYLIGHT CHARACTERISATION OF CLASSROOMS IN HERITAGE SCHOOL BUILDINGS

This paper studies the daylight characteristics in selected high schools that are located in heritage-listed buildings. Heritage buildings were selected in this research due the problematic condition regarding the indoor illumination level after being adaptively reused. Based on the previous research, lighting in educational institution is a critical factor because poor lighting not only isdetrimental to the occupants’ visual comfort but also might lead to visual fatigue. To achieve the objectives of this paper, daylight level measurements and observation were conducted. The results show that the daylight that penetrates into the classrooms were below the standard due to many obstructions founded in both schools. Artificial lightings were used as a supplementary during thewhole school hours since the daylight was not uniformly distributed. Thus it can be concluded that the inappropriate adaptive reusing heritage building indoor is significantly affecting the indoor light level and might lead to visual discomfort issues for students. The research findings as well as the suggestions have been delivered to the school management to overcome the issues founded.

LED Lights With Hidden Intensity-Modulated Blue Channels Aiming for Enhanced Subconscious Visual Responses.

A new form of light-emitting diode (LED) light suitable for general illumination is proposed to enhance subconscious, nonimage-forming visual responses, which are essential to our well-being. Pulsing light has been shown to reduce photoreceptor adaptation and elicit stronger subconscious visual responses at an indoor illumination level. Using the silent substitution technique, a melanopsin-selective flicker can be added into white light. A linear optimization algorithm was developed to suppress any perceivable fluctuation of light intensity and colors of illuminated objects. Two examples of lights are given to illustrate the potential applications of the proposed multi-LED light for general illumination and therapeutic purposes.