Horizontal Illuminance Research Articles

The Influence of Selected Type of Daylight Device on Horizontal and Vertical Internal Illuminance

Daylighting is one of the key parameters of internal environment generation in buildings. This parameter determines creation of suitable conditions for visual activities in internal spaces and contributes to human well-being and comfort. Daylight is also the primary stimulus for synchronizing the human circadian photobiological system. Traditional parameters and criterions based explicitly on photopic vision have been critically re-evaluated and basic principles of circadian photometry have been developed in theoretical level. Nevertheless daylighting has often been neglected or left out from the main design proposals, which are usually just focused on covering basic needs for vision tasks represented barely by the illumination limits on working plane. Because the amount of light entering the eye is the most important for circadian entrainment, the illuminance recorded on a vertical plane, at eye level, is more significant for human biological system. This paper deals with the comparison of internal horizontal and vertical illuminance recorded in 3 models of room, inserted in simulation program Radiance and illuminated by three types of lighting devices, i.e. window, light-pipes and permanent supplementary artificial lighting represented by the combination of window and light-pipes. Achieved data also express the influence of a workplace position on the amount of illuminance entering the eye according to the direction of the incoming daylight from windows in side-lit room.

Research on the assessment indicators for crime prevention lighting in residential areas based on AHP and Entropy Weight

Lighting can affect the probability of crime. In order to establish safe and secure residential areas’ lighting environment, the elements for crime prevention are researched. Originally propose 14 assessment indicators of lighting environment which can be recognized subjectively and may influence crime rate. They are horizontal illuminance illuminance uniformity surround ratio vertical illuminance three-dimensional color rendering glare lamp pole height light pole distance lamp aesthetic lamp conciseness color temperata lamp distribution light source. The data came from residents in China. Through screening and giving weights by Analytic Hierarchy Process, there are 7 key assessment indicators left. Then give weights to the ultimate 7 key assessment indicators by Entropy Weight to verify their rank. The results show that 7 key assessment indicators have the same rank in contrast of the two methods. According to the crime prevention influence of the lighting environment, the sort is: vertical illuminance, horizontal illuminance, three-dimensional, color temperature, glare, uniformity of illuminance, color rendering.

Daylighting for Buildings: Influence of the Solar Eclipse on its Spectral Characteristics

Extraordinary occurrence of the solar eclipse offers opportunity to evaluate spectral characteristic changes and intensities of daylighting during its various phases. Changes of the daylight spectrum in positions: zenith and 45° above horizon with orientation of sensors opposite to sun position were measured. Changes of horizontal illuminance and luminance as well as changes of the correlated colour temperature in the range of the Planck curve were measured in Bratislava and evaluated. Paper presents results of experimental measurements and discusses in point of view of sunlight characteristic’s changes as source of daylighting.

Office Occupants’ Mood and Preference of Task Ambient Lighting in the Tropics

Office lighting is vital for energy savings and occupant’s visual comfort being. Energy efficient lighting has been studied extensively in the aspect of daylighting harvesting and task ambient lighting, predominantly in Temperate developed countries. However, the lack of evident on the effectiveness of low ambient task lighting in the Tropics has prompted this paper to investigate the practicality of such lighting design for the Tropics. This paper explores into the office occupant’s mood and preferences of low ambient daylight and usage of task light for the office in the Tropics. It also discusses the recorded work plane illumination level upon the usage of such lighting system. It studies the impact of such lighting design on people’s preference, work plane illumination for three office spaces with the different luminous environment. In regards to the source of ambient lighting, two offices harvest daylight, and another uses the conventional overhead lights in accordance with MS1525 recommendations. Three of the offices have 15 samples respectively and the workspace horizontal illuminance level is measured across a month. The results of before and after the provision of task light reveal that the acceptance for low ambient task lighting system and it is widely preferred. However, the task light is not necessary utilized as some people are adapted to do computer work under low ambient lighting (~50-150lux). It shows that people’s preference for work plane illuminance varies greatly. Many agree that they are in control with their personal lighting environment when an appropriate glare-free task light is being used. The paper recommends that office luminous measurement shall take other lighting parameters such as the vertical illuminance and luminance ratio into consideration for future research.

The Effect of Colored Surfaces and Tinted Window Glazing on Daylight Spectral Characteristics and Illuminance Levels in Deep Space Rooms and its Evaluation for Human Visual and Biological Response

Examination, design and control of internal light conditions in permanently occupied spaces belong to important actual architectural issues. Especially in offices, workplaces can be often situated far from window. As the new medical facts were emerging during last decade, the significance of the non-visual human response on light, also known as circadian efficiency of light has been rising [1]. Biological stimulation of light depends on quantitative and qualitative properties of light, which penetrates directly into the human eye in contrast to visual stimulation depending more on the amount of the light reflected from the observed surfaces. Inappropriate selection of spectral filter in windows or internal coloured surfaces may significantly decrease potential light biological stimulation and may reflects in higher rate of Sick Building Syndrome (SBS) occurrence, which is connected to Seasonal Affective Disorders (SAD). The paper describes two experiments done in real conditions, focused on the effect of internal coloured surfaces and the influence of tinted glazing on daylight spectral characteristics in three deep space model rooms exposed only to natural daylight. Deeper positions with sensor`s orientation toward window and side wall were selected. The position of sensor representing the eye of sitting person and especially its orientation regarding to window proved noticeable different rate of biological stimulation`s efficiency in comparison with same level of horizontal illuminance on working area.

Variability in dynamic daylight simulation in clear sky conditions according to selected weather file: Satellite data and land-based station data

While the use of satellite weather files is a possibility in regions without terrestrial stations, it is necessary to consider their impact on daylight simulations. This paper aims to verify the variability of dynamic daylight simulation results according to the weather file used. This study compares the results of daylight simulations in learning spaces using different weather files (land-based station data and satellite data). This work is divided into three main stages: comparative analysis of climatic databases; comparative analysis of annual outside horizontal illuminance; analysis of dynamic daylight performance metrics. Annual calculated dynamic daylight metric indicates variations of up to 13% under the different weather files analysed. This is a relevant topic since the accurate prediction of daylight levels for indoor environments guides daylighting design.

Lighting Energy Saving with Light Pipe in Farm Animal Production

The Swedish animal production sector has potential for saving electric lighting of €4-9 million per year using efficient daylight utilisation. To demonstrate this, two light pipe systems, Velux® (house 1) and Solatube® (house 2), are installed in two identical pig houses to determine if the required light intensity, daylight autonomy (DA), and reduced electricity use for illumination can be achieved. In each house, three light sensors continuously measure the indoor daylight relative to an outdoor sensor. If the horizontal illuminance at pig height decreases below 40 lux between 08.00 and 16.00 hours, an automatic control system activates the lights, and electricity use is measured.. The daylight factor (DF) and DA are determined for each house, based on annual climate data. The mean annual DA of 48% and 55% is achieved for house 1 and house 2, respectively. Light pipes in house 2 have delivered significantly more DA than those in house 1. The most common illuminance range between 0 and 160 lux is recorded in both houses, corresponding to approximately 82% and 83% of daylight time for house 1 and house 2, respectively. Further, the daylighting system for house 2 has produced a uniform DF distribution between 0.05 and 0.59. The results demonstrate that considerable electric energy savings can be achieved in the animal production sector using light pipes. Saving 50% of electric lighting would correspond to 36 GWh or 2520 t CO2 per year for Sweden, but currently the energy savings are not making the investment profitable. (Less)

Daylighting Contribution for Energy Saving in a Historical Building

The purpose of this study is assessing the reliability of the software DIALux 4.12 for daylighting design, comparing experimental data with simulation results; the comparison was performed for an office.The daylight illuminance distribution inside the room, the external zenith luminance and the external horizontal diffuse illuminance were measured during the weeks from January 19th to February 20th; the data gathered were further reduced to match conditions related to the CIE sky type #12 (CIE Standard Clear Sky, low luminance turbidity) and finally the comparison was carried in terms of daylight illuminance distribution and relative percentage error.

Radiometric Boundary Condition Models for Building Performance Simulation: An Empirical Assessment

Designand operation of buildings in view of optimal thermal and visual performance can benefit from deployment of appropriate simulation tools. Specifically, the design and configuration of building-integrated renewable energy systems (solar-thermal collectors and photovoltaic panels) can be effectively supported via reliable computation of incident solar radiation. Toward this end, advanced building energy and lighting simulation programs typically use high-resolution sky models. In this contest, the present contribution addresses the reliability of these models based on long-term high-resolution data collected at the observatory of the Department of Building Physics and Building Ecology at the Vienna University of Technology, Austria. This observatory is equipped with radiometric and photometric sensors to measure global and diffuses horizontal irradiance and illuminance, global vertical irradiance and illuminance of the four cardinal orientations, as well as sky radiance and luminance values for discrete sky patches. To evaluate the performance of two widely used sky models, we compared simulated and measured vertical irradiance values as well as patch radiance values. The statistical appraisal of the comparison points to limits in the predictive accuracy of both models.

Optimization of facade design based on the impact of interior obstructions to daylighting

Overcrowding in the perimeter zone is an inevitable issue in residential rooms with limited space. Obstructions, such as furniture and household items, may block the existing windows, and therefore affect interior daylight conditions. A facade design approach is needed that simultaneously takes into account daylighting and the volume of usable space for obstructions in the perimeter zone of such rooms. This study simulates daylight distributions in a typical small residential room with obstructions in front of windows. The simulation consists of two parts. First, the effects on horizontal illuminances caused by different positions and shapes of obstructions are examined under an overcast sky. Second, the maximum usable space volumes for obstructions of 51 optimized facade configurations are calculated in terms of four window-to-wall ratios (WWRs). The results of this study show that optimizing the forms of facade design can increase the usable interior space volume and meet the daylighting requirements of Chinese standards for small residential rooms. Additionally, by using the optimized facade forms, a facade with a WWR value of 50% provides the maximum usable space for obstructions. Based on the above results, this paper presents two matrices that can help architects in selecting the appropriate fenestration methods and confirming the size of usable space and allocation for residents.

Verification of simple illuminance based measures for indication of discomfort glare from windows

Modern office buildings are often designed with highly glazed facades, with an intention of being sufficiently day lit. However, extensive daylight supply has its backside, as glare might be a considerable concern. From a building design perspective it is important to be able to make reasonable predictions of discomfort glare from windows already in the early design stage when decisions regarding the façade are taken. This study focus on verifying if simple illuminance based measures like vertical illuminance at eye level or horizontal illuminance at the desk are correlated with the perceived glare reported by 44 test subjects in a repeated measure design occupant survey and if the reported glare corresponds with the predictions from the simple Daylight Glare Probability (DGPs) model. Large individual variations were seen in the occupants' assessment of glare in the present study. Yet, the results confirm that there is a statistically significant correlation between both vertical eye illuminance and horizontal illuminance at the desk and the occupants' perception of glare in a perimeter zone office environment, which is promising evidence towards utilizing such simple measures for indication of discomfort glare in early building design. Further, the observed response indicate that the participants in the present study were more tolerant to low illuminance levels and more sensitive to high illuminance levels than the DGPs model would predict. More and larger studies are needed to confirm or enfeeble this latter finding.

Data regression on sphere for luminance map creation from sky scanner measurements

Sky luminance distribution acquired by a whole-sky scanner has well-known constraints in resolution because of the restricted field of view and limited number of measured sky elements. The interpolating methods on measured data can significantly reduce the uncertainties of the scanners to create more accurate sky luminance maps depending on the mathematical approach. The general lack of many regressions is their low adaptability to significant sky luminance changes, e.g. on the cloud edges or near the sun disk. Three regression methods like inverse distance to a power, smoothing splines on the sphere and hybrid adaptive splines were tested on real skies measured with a self-made portable spectral sky scanner. Data regressions are compared and verified by the luxmeter in terms of calculated diffuse horizontal illuminance.

Relationship between Roadway Illuminance Level and Nighttime Rural Intersection Safety

Almost all existing research about intersection lighting indicates that the presence of lighting reduces nighttime crashes. This study aimed to quantify the effect of lighting level and lighting quality on the night-to-day (ND) crash ratios at rural intersections. Illuminance measurements were collected from 99 lighted and unlighted rural intersections in Virginia. The measurements were then combined with the crash data, obtained from the Virginia Department of Transportation, for each of the intersections. A negative binomial regression was used to model the crash and lighting data. Results indicated that lighting level (average horizontal illuminance) significantly affected the ND crash ratios at rural intersections. A 1 lux (lx) increase in the average horizontal illuminance at all rural intersections in Virginia corresponded to a 7% decrease in the ND crash ratio. For the lighted intersections, a 1 lx increase in average horizontal illuminance corresponded to a 9% decrease in the ND crash ratio. The largest decrease in the ND crash ratio was for unlighted intersections, where a 1 lx increase in the average horizontal illuminance corresponded to a 21% decrease. Stop-controlled intersections had smaller ND crash ratios than signalized intersections. Intersections with a posted speed limit of less than or equal to 40 mph had lower ND crash ratios than intersections with a posted speed limit of greater than 40 mph. Each of the results is discussed with respect to the impacts of the lighting measurements on nighttime driving safety and overall visibility.

Effects of Different Security Lamps on Pedestrians Subjective Responses of Luminous Environment in a Residential Street

Outdated security lights installed in residential district are vulnerable to safety, cause light pollution, and consume excessive energy. To solve these problems, the City of Seoul launched the Luminous Environment Improvement Project that changes a light source of residential security lights from sodium lamps to LED lamps as the Light Pollution Prevention Law Based on Artificial Lighting was enforced. Little study has been devoted to change on luminous environment and perception resulting from replacement of security lights in residential districts. Therefore, the purpose of this research is to analyze change in pedestrian perception and improved LED effects after high pressure sodium lamps were replaced by LED lamps in the existing residential districts. For pedestrian perception, questionnaire assessment was used to assess perceived danger, visual accessibility, perceived natural colour of objects, and perceived light ambience. In addition, illuminance and luminance on roads were physically measured to determine LED effects. Comparative analysis was done between sodium lamps and LED lamps were on lighting environments by measuring road surface horizontal illumination and luminance, elements of which are defined in KS A 3701 Lighting for Roads and KS C 7658 LED Luminaries for Road and Street Lighting (Korean Industrial Standards). The questionnaire assessment was analyzed with SPSS Ver.21 to evaluate internal consistency on the questionnaire and mean difference of each item among survey groups for lighting environment of sodium lamps and LED lamps. As a result, LED lamps, compared with sodium lamps, were more than three times higher in horizontal illumination and more than double the average luminance. Statistically significant difference was also demonstrated in perceived danger, visual accessibility, perceived natural colour of objects, and perceived light ambience. Given the positively improved lighting environment with LED lamps better than existing sodium lamps, revealed from the survey results, it is considered that LED lamps will set up road luminous environment with enhanced safety and visibility for pedestrians in residential areas with high number of pedes

On the relation between zenith sky brightness and horizontal illuminance

On the relation between zenith sky brightness and horizontal illuminance

Lighting performance and electrical energy consumption of a virtual window prototype

This article discusses the design and evaluation of a virtual window prototype, built using arrays of LED tiles to simulate the light as well as the view of a window. Arrays of white light LED fixtures with adjustable colour temperatures were incorporated to provide direct light into the test room. Lighting performance was evaluated by measuring horizontal illuminance on the workplane, vertical illuminance on the observer’s eye plane, and luminance perceived by the observer at four vertical points. For estimating the electrical energy consumption, real-time power consumption of the entire system was measured, and three daily usage profile scenarios and two annual modes were considered. In addition, five locations were chosen to represent various climate types. The results show that under the maximum setting, the average workplane illuminance was 239lx for the test room used, whereas discomfort glare at the observer’s positions was classified as imperceptible. Patches of direct light on the side walls could be created as an intended effect from installing the direct light source arrays. Variation of average annual space availability within a given location as a function of usage profile is found to be very small; the values are however sensitive to the chosen criterion of workplane illuminance. Based on the designated daily usage profiles and annual modes, the normalised, total annual electrical energy consumption in all climate types is on average within the range of 0.63–0.79, relative to the total electrical energy consumed by the prototype when it constantly displays the maximum intensity setting.

Application of Perez Daylight Efficacy Model for Kolkata

The availability of daylight on any plane of a building and the passive heat gain due to the corresponding incident solar radiation is correlated by daylight luminous efficacy. The present study was carried out to evaluate daylight efficacy on exterior horizontal plane for Kolkata using Perez Model an established analytical model and Indian measured solar radiation database. The analytical model was selected according to the sky conditions throughout the year. The estimated efficacy models were used to predict horizontal global and diffuse illuminances. The predicted global and diffuse illuminance was validated with the measured illuminance values using standard statistical tools. The estimated Root Mean Square Deviation (RMSD) and Mean Bias Deviation (MBD) between experimental and simulated values of illuminance are +7 % and ±4.5 % respectively. An analytical model of luminous efficacy for Kolkata was also developed from the measured values. From the study, it has been found that diffuse luminous efficacy varies from 114–138 lm/W whereas global luminous efficacy varies from 98–112 lm/W in a year. It is also observed that sky clearness index and diffuse irradiance ratio have significant effect on the variations of luminous efficacy in different seasons.

Smooth energy mappings for freeform lens design

A method of smooth energy mappings for uniform rectangular-shaped illumination is proposed. The adequacy of the proposed method is demonstrated by ray-tracing simulation. The method can be used for horizontal clear-cut illumination to comply with the ECE regulations for auto fog light and 15°-tilt for headlamp.

The Research Search For The Least Beneficial Overcast Sky And Progress In Defining Its Luminance Gradation Function

Abstract Recently illuminance levels under ISO/CIE homogeneous standard sky types were characterised in their relative terms after ISO/CIE (2004, 2003) standardised as normalised by the luminance in the zenith. Sky luminance and horizontal illuminance based on the gradation and scattering indicatrix functions, including the extreme overcast cases frequently encountered in nature, were recently determined in absolute physical units of luminance in kilocandles per meter square and of illuminance in kilolux. The historical search to find energy and visibility critical sky luminance distributions shows a progression of steps in studying the worst or critical overcast situations. That progression has enabled the determination and evaluation of interior illuminance for comparison of the merits of dual daylighting and artificial lighting under established criteria for comfortable visibility.

Lighting Trend for Indian Cricket Stadiums

Good lighting is fundamental to the success of any sporting event. Regardless of whether a sport is played indoor or outdoor be it a leisure activity or a world championship, at nighttime or in daylight, live telecast on TV or not - the primary demand for lighting remains the same. A consistent level of evenly spread illuminance across the full field of play is essential. Again the objects of observation (ball, puck, etc) move fast against a background of non uniform luminance, their angular sizes vary in a wide range, and the players, referees (who are observers of the objects) move in random directions. The direction of play is also important. According to these Groups, Classes and direction of play of different types of sports have different guidelines of lighting which are specified in CIE and IESNA. It is important that appropriate type and quality of lighting is used for three fundamental reasons. The reasons are to ensure the safety of the players and other people involved in the game; to provide better viewing for the spectators; to ensure that the significant amount of money spent on the installation has been utilized. The Inter- National Cricket Council (ICC) has its individual standards for cricket stadium lighting. The Board of Cricket Control in India (BCCI) follows those standards for cricket stadium lighting in India. These standards include lighting parameters, like Horizontal and Vertical Illumination, Uniformity, Glare Rating for cricket stadiums.