scholarly journals Determination of luminance distribution under tropical sky conditions

Vestnik MGSU ◽  
2019 ◽  
pp. 1096-1105
Author(s):  
Nguyen Thi Khanh Phuong
Keyword(s):  
Great Influence ◽  
Research Problem ◽  
Natural Illumination ◽  
The Real ◽  
Clear Sky ◽  
Luminance Distribution ◽  
High Solar Radiation ◽  
Sky Conditions ◽  
Sky Type ◽  
Overcast Sky

Introduction. Natural illumination calculations depend on the sky luminance distribution. The most often used diagram of sky luminance in handbooks and guidelines is the luminance distribution in the cloudy sky proposed by Moon and Spencer. This concept actually includes the tropical areas of Vietnam, where the overcast sky and clear sky does not typically occur. To improve the calculation of natural illumination, it is necessary to determine the luminance distribution in the real sky. Materials and methods. In solving the research problem, the real sky types for Hanoi were identified using the 15 international standard sky types with their descriptions by lighting climate, which is provided using the method by R. Kittler. The descriptions are derived from the data on diffuse horizontal illumination Dv, extraterrestrial horizontal illumination Ev and light turbidity coefficient Tv. For a specific sky type, the standard parameters were selected for calculating the luminance distribution of the real sky. Results. The obtained results show that the typical sky type of Hanoi is the partly cloudy sky, no gradation towards zenith, with slight bleaching towards the Sun (type VI). The sky types from October to December are partly cloudy with the obscured Sun (type IX) and partly cloudy with the more luminant circumsolar area (type X). The study shows that the state of cloud coverage has a great influence on the level of diffuse horizontal illumination and luminance distribution under tropical sky conditions. Conclusions. It is revealed that the typical sky type for Hanoi is neither overcast nor clear sky. A typical sky with statistic dominance of cirrus and stratus clouds under effect of high solar radiation of Vietnamese tropical climate gives a high level of diffuse horizontal illuminance. The results show that the difference in luminance distribution between the CIE standard overcast sky and Kittler’s intermediate sky can be resolved at the angles of sky point elevation above horizon γ is higher than 50° with the relative errors below 10 %. In other words, the luminance distribution β of the considered sky type is significant for a system of side natural illumination.

The use of horizontal sky illuminance to classify the CIE Standard General Skies

2016 ◽  
Vol 48 (8) ◽  
pp. 1034-1041 ◽  
Author(s):  
KA Alshaibani
Keyword(s):  
Low Latitude ◽  
Simple Task ◽  
Frequency Distributions ◽  
Clear Sky ◽  
Luminance Distribution ◽  
Long Period ◽  
The World ◽  
Sky Type ◽  
Overcast Sky

The CIE Standard General Skies defines the luminance distribution of skies into 15 types, from overcast sky to clear sky. Finding the frequency distributions of such skies is not a simple task, for two reasons. The first is the need for accurate luminance measurements over a long period of time. Such data are not available in many regions around the world. The second is the difficulty in obtaining accurate readings for the zenith luminance in low latitude climates. This paper presents a method in which the horizontal sky illuminance can be used to classify sky type.

scholarly journals Daylighting on the working plane in oriented attic rooms under overcast and clear sky

2014 ◽  
Vol 9 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Kristián Kondáš ◽  
Stanislav Darula
Keyword(s):  
Main Task ◽  
Distribution Modelling ◽  
Clear Sky ◽  
Luminance Distribution ◽  
New Criterion ◽  
Sky Conditions ◽  
Overcast Sky

AbstractThe evaluation of daylight conditions in building interiors is based on the Daylight Factor concept after current Slovak standards. Criteria and requirements determined in these standards consider the worst daylight exterior conditions which are described by CIE overcast sky model. The sky luminance distribution of overcast sky is centrical to the zenith, so independence of window orientation to cardinal points is characteristic in daylighting calculations. The sky luminance distribution modelling is one of the main task of the daylight source research more than 50 years. It is evident that also other types of sky conditions exist in nature. An introduction of a new criterion based on photometric variables, which also consider sunlight influence, is expected. This article represents a study of the influence of the interior orientation on distribution of daylighting in attic spaces under an overcast and clear sky

Evaluation of Illuminance of Rooms Oriented to Different Cardinal Points

2014 ◽  
Vol 1041 ◽  
pp. 390-394
Author(s):  
Stanislav Darula ◽  
Jitka Mohelníková
Keyword(s):  
Working Time ◽  
Direct Sunlight ◽  
Central European ◽  
Clear Sky ◽  
The Common ◽  
Sky Conditions ◽  
Overcast Sky

Daylighting levels in interiors are changed every day since sunrise to sunset in dependence on luminous exterior conditions. Indoors are illuminated by diffuse skylight prevailing time of the year in Central European counties while a lot of sunny situations occur mainly during transitional and summer periods. The later can produce overheating as well as glare or disturbing luminance due to excessive sunlight in the space close to windows. If interiors are designed with screened work places the influence of direct sunlight during working time has to be evaluated.The article will present results of computer daylight simulations in a side-lit office room oriented to cardinal points. The study is focused on daylighting evaluation of the room orientation influence on levels under clear sky conditions and compared with results achieved for the CIE overcast sky model. The calculations were run in software Daylight Visualizer 2.6.7. The daylight simulation show that applying the clear sky model for illumination of oriented rooms, the substantial different illuminances can be resulted compared to outputs from the common overcast sky daylight metrics.

A Model for the Angular Distribution of Sky Radiance

1980 ◽  
Vol 102 (3) ◽  
pp. 196-202 ◽  
Author(s):  
F. C. Hooper ◽  
A. P. Brunger
Keyword(s):  
Continuous Distribution ◽  
Total Solar Radiation ◽  
Diffuse Component ◽  
Clear Sky ◽  
Solar Radiation Incident ◽  
The Mean ◽  
Rms Error ◽  
Sky Radiance ◽  
Sky Conditions ◽  
Overcast Sky

A flexible mathematical model is introduced which describes the radiance of the dome of the sky under various conditions. This three-component continuous distribution (TCCD) model is compounded by the superposition of three separate terms, isotropic, circumsolar and horizon-brightening factors, each representing the contribution of a distinguishable sky characteristic. In use, a particular sky condition is characterized by the values of the coefficients of each of these three terms, defining the distribution of the total diffuse component. The TCCD model has been demonstrated to fit both the normalized clear sky data and the normalized overcast sky data with an RMS error of about ten percent of the mean overall sky radiance. By extension the model could describe variable or partly clouded sky conditions. The model will permit improvement in the prediction of the total solar radiation incident upon a surface of given tilt and orientation, such as that of a solar collector.

scholarly journals A Simple Method for the Assessment of the Cloud Cover State in High-Latitude Regions by a Ground-Based Digital Camera

2006 ◽  
Vol 23 (3) ◽  
pp. 437-447 ◽  
Author(s):  
M. P. Souza-Echer ◽  
E. B. Pereira ◽  
L. S. Bins ◽  
M. A. R. Andrade
Keyword(s):  
A Priori ◽  
Digital Camera ◽  
Correlation Coefficients ◽  
Visible Range ◽  
Direct Sunlight ◽  
Simple Method ◽  
Charge Coupled Device ◽  
Clear Sky ◽  
Sky Conditions ◽  
Overcast Sky

Abstract This work describes the development of a simple method of field estimating the sky cloud coverage percentage for several applications at the Brazilian Antarctic Station, Ferraz (62°05′S, 58°23.5′W). The database of this method was acquired by a digital color camera in the visible range of the spectrum. A new algorithm was developed to classify each pixel according to a criteria decision process. The information on the pixel contamination by clouds was obtained from the saturation component of the intensity, hue, and saturation space (IHS). For simplicity, the images were acquired with a limited field of view of 36° pointing to the camera’s zenith to prevent direct sunlight from reaching the internal charge-coupled device (CCD) on the camera. For a priori–classified clear-sky images, the accuracy of the method was superior to 94%. For overcast-sky conditions, the corresponding accuracy was larger than 99%. A comparison test was performed with two human observers and our method. The results for the 29 images collected for several time of days during 50 days in 1999 summer were compared to visual observations of these same digital images by two trained field meteorologists. Correlation coefficients between human observers and the automatic method ranged from 0.84 for clear-sky conditions, and the lowest was 0.09 for undefined-sky conditions.

Aesthetic perception of a small office with different daylighting systems

2017 ◽  
Vol 27 (9) ◽  
pp. 1187-1202 ◽  
Author(s):  
Claudia Moscoso ◽  
Barbara Matusiak
Keyword(s):  
Aesthetic Experience ◽  
Semantic Differential ◽  
Aesthetic Perception ◽  
Significant Interaction Effect ◽  
Clear Sky ◽  
Single Side ◽  
The Aesthetic ◽  
Sky Conditions ◽  
Overcast Sky

The quality of a lit environment cannot be deduced solely from the quantity of light. Therefore, daylighting studies should not only be focused on the usage of lighting metrics but should also consider the aesthetic experience. This paper examines the influence of daylighting systems on the aesthetic perception of a small office. One single side lit office was equipped with four different daylighting systems (white blinds, high-reflecting blinds, hybrid light shelf and mirror light shelf) under two sky conditions (clear sky and overcast sky). In total, eight stimuli were captured and presented via stereoscopic images. Fifty participants evaluated the images using the semantic differential scale to rate nine architectural quality attributes. The results from MANOVA indicated that both the daylighting systems and the type of sky had an effect on the aesthetic attributes, and that the significant interaction effect suggested that the aesthetic perception of a daylighting system depends on the type of sky. Subsequent statistical findings showed that the high-reflecting blinds comprised the daylighting system that scored highest in nearly all attributes under both clear and overcast sky conditions.

scholarly journals The influence of sun-protective devices on natural Light distribution in premises

2019 ◽  
Vol 110 ◽  
pp. 01070
Author(s):  
Sergey Stetsky ◽  
Kira Larionova
Keyword(s):  
Climatic Conditions ◽  
Climate Control ◽  
New Approach ◽  
Clear Sky ◽  
Protective Devices ◽  
First Case ◽  
Lighting Environment ◽  
Indoor Lighting ◽  
Sky Conditions ◽  
Overcast Sky

The article observes the new approach to a lighting environment in premises of civil buildings in hot and sunny climatic conditions. Under such conditions, the use of sun-protective devices (SPD) of different types and geometrics becomes traditional way of passive climate control in interiors. However, the authors determined, that the most traditional types of external SPD (such as canopies or awnings) have a different effect on indoor lighting environment due to the conditions of external natural illumination under overcast sky vault or clear sky conditions. In the first case, the stationary SPD act as shadowing elements, which block the light flows from the CIE standard overcast sky. In the second case, which corresponds to a clear sky sunny conditions, such SPD block the solar radiation, decreasing overheating and reflect sun beams to an interior, increasing the value of daylight factor (DF) at least in the furthest from windows areas of a premise. The proposed solutions allow reducing electric power consumption in buildings.

An Analysis of Nonovercast Sky Luminance Models Against Hong Kong Data

2006 ◽  
Vol 129 (4) ◽  
pp. 486-493 ◽  
Author(s):  
Danny H. W. Li ◽  
Chris C. S. Lau
Keyword(s):  
Hong Kong ◽  
Modern Architecture ◽  
Distribution Model ◽  
Position Change ◽  
Clear Sky ◽  
Luminance Distribution ◽  
Artificial Neural Network Ann ◽  
The Tropics ◽  
Sky Conditions ◽  
Solar Position

Daylighting is an important issue in modern architecture that has been characterized by the use of curtain walls in buildings. Nonovercast skies, including clear and partly cloudy days, are essential because they may occur more frequently for places such as in equatorial regions and the tropics. Better understanding of nonovercast sky luminance distribution is vital to estimate the dynamic variation in daylight illuminance as sky condition and solar position change. This paper presents the work on the evaluation of six clear sky and three partly cloudy sky models against three-year (1999–2001) measured Hong Kong sky luminance data. The general features and characteristics for the models were described and assessed. The nonovercast sky conditions were identified using the ratio of zenith luminance (Lz) to diffuse illuminance (Dv) and the ratio of global illuminance (Gv) to the extraterrestrial illuminance (Ev). Subsequent interpretations of the clear skies into high and low turbid types were conducted in conjunction with the cloud cover (CLD) and the luminous turbidity (Tv), and partly cloudy skies were further subdivided into thin and thick cloud modes using sunshine hour (SH) and global irradiance (GSI). A statistical analysis of the models revealed that the Gusev model (i.e., CIE (Internal Commission on Illumination) polluted sky No. 13) and the model by Chen et al. (1999, “Luminance Distribution Model of Intermediate Skies,” Zhaom Ing Gong Chen Xuebao, 10(1), pp. 59–63 (in Chinese)) developed using artificial neural network (ANN) theory with the measured data in Chongqing, China (29.6degN and 106.5degE) showed the best predictions for sky luminance at this location under the clear and partly cloudy sky conditions, respectively.

scholarly journals Local short-term variability in solar irradiance

2016 ◽  
Vol 16 (10) ◽  
pp. 6365-6379 ◽  
Author(s):  
Gerald M. Lohmann ◽  
Adam H. Monahan ◽  
Detlev Heinemann
Keyword(s):  
Power Systems ◽  
Classification Scheme ◽  
Grid Integration ◽  
Short Term ◽  
Clear Sky ◽  
Smoothing Effects ◽  
Sensor Density ◽  
Sky Conditions ◽  
Sky Type ◽  
Field Variability

Abstract. Characterizing spatiotemporal irradiance variability is important for the successful grid integration of increasing numbers of photovoltaic (PV) power systems. Using 1 Hz data recorded by as many as 99 pyranometers during the HD(CP)2 Observational Prototype Experiment (HOPE), we analyze field variability of clear-sky index k* (i.e., irradiance normalized to clear-sky conditions) and sub-minute k* increments (i.e., changes over specified intervals of time) for distances between tens of meters and about 10 km. By means of a simple classification scheme based on k* statistics, we identify overcast, clear, and mixed sky conditions, and demonstrate that the last of these is the most potentially problematic in terms of short-term PV power fluctuations. Under mixed conditions, the probability of relatively strong k* increments of ±0.5 is approximately twice as high compared to increment statistics computed without conditioning by sky type. Additionally, spatial autocorrelation structures of k* increment fields differ considerably between sky types. While the profiles for overcast and clear skies mostly resemble the predictions of a simple model published by Hoff and Perez (2012), this is not the case for mixed conditions. As a proxy for the smoothing effects of distributed PV, we finally show that spatial averaging mitigates variability in k* less effectively than variability in k* increments, for a spatial sensor density of 2 km−2.

Overcast sky conditions and luminance distribution in Hong Kong

2004 ◽  
Vol 39 (1) ◽  
pp. 101-108 ◽  
Author(s):  
Danny H.W. Li ◽  
Chris C.S. Lau ◽  
Joseph C. Lam
Keyword(s):  
Hong Kong ◽  
Luminance Distribution ◽  
Sky Conditions ◽  
Overcast Sky
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