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.

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.

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

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.

Clear sky solar illuminance using visual band irradiance

2014 ◽  
Vol 25 (3) ◽  
pp. 11-19
Author(s):  
A. Nurick
Keyword(s):  
Experimental Data ◽  
Wavelength Range ◽  
Atmospheric Aerosols ◽  
Rayleigh Scattering ◽  
Ground Level ◽  
Climatic Conditions ◽  
Visible Range ◽  
Full Spectrum ◽  
Clear Sky ◽  
Sky Conditions

Solar illuminance may be quantified by applying relevant efficacy functions to available full spectrum ground irradiance. Alternatively, illuminance may be determined by applying the Photopic function to ground level irradiance spectra obtained from the terrestrial irradiance spectrum adjusted using relevant atmospheric absorption and scattering coefficients. The Photopic function has finite values in the wavelength range of 400 nm to 700 nm and is concentrated around a mean wavelength of 555 nm with irradiance at wavelengths close to 555 nm contributing to the major portion of illuminance. Calculation of ground level direct, diffuse and hence global illuminance is simplified as absorption of irradiance in the atmosphere by water vapour and uniformly mixed gases is negligible and may be ignored. It is shown that due to the small variations in the overall irradiance over wavelengths in the visible bandwidth combined with the concentration effect of the Photopic function in this wavelength range illuminance may be calculated, with good accuracy, using constant extinction functions for both direct and diffuse illuminance. Due to the concentration of illuminance by the Photopic function global illuminance data were also correlated with a simplified description of illuminance attenuation through the atmosphere based on the Beer-Lambert-Bouger Law using a single constant effective extinction coefficient which accounts for all extinction processes under clear sky conditions over the visible range of wavelengths. Constants used in extinction functions for solar irradiance due atmospheric aerosols were obtained by fitting experimental data to analytical descriptions of atmospheric extinction while published constants were used for ozone and Rayleigh scattering. The analytical descriptions of global illuminance with solar elevation were compared with experimental data collected at Johannesburg over both summer and winter clear sky conditions. Correlations of measured and calculated global illuminance data for the method based on extinction of various atmospheric components was 4.47 % and 4.49 % for the method based on the Beer-Lambert-Bouger Law, both normalised using the terrestrial illuminance constant. While measurements were made at a specific site in Gauteng, the methods used to correlate the data are general and location independent but local climatic conditions may need to be taken into account to quantify the extinction coefficients for specific areas.

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 Radiation Exchange at Greenhouse Tilted Surfaces under All-Sky Conditions

2021 ◽  
Author(s):  
Erick K. Ronoh
Keyword(s):  
Thermal Radiation ◽  
Thermal Environment ◽  
Shortwave Radiation ◽  
Material Surface ◽  
Climate Control ◽  
Surface Design ◽  
Clear Sky ◽  
Radiation Exchange ◽  
Surface Inclination ◽  
Sky Conditions

Greenhouses generally exhibit a greater degree of thermal radiation interaction with the surroundings than other buildings. A number of greenhouse thermal environment analyses have handled the thermal radiation exchange in different ways. Thermal radiation exchange at greenhouse surfaces is of great interest for energy balance. It dominates the heat transfer mechanisms especially between the cover material surface and the surrounding atmosphere. At these surfaces, the usual factors of interest are local temperatures and energy fluxes. The greenhouse surfaces are inclined and oriented in various ways and thus can influence the radiation exchange. The scope of this work is determination of the thermal radiation exchange models as well as effects of surface inclination and orientation on the radiation exchange between greenhouse surfaces and sky. Apart from the surface design and the thermal properties of the cover, the key meteorological parameters influencing longwave and shortwave radiation models were considered in detail. For the purpose of evaluating surface inclination and orientation effects, four identical thermal boxes were developed to simulate the roof and wall greenhouse surfaces. The surface temperatures and atmospheric parameters were noted under all-sky conditions (clear-sky and overcast). Differences in terms of surface-to-air temperature differences at the exposed roof and wall surfaces as influenced by surface inclination and orientation are discussed in this work. Overall, the findings of this work form a basis for decisions on greenhouse design improvements and climate control interventions in the horticultural industry.

Evaluation of net shortwave radiation over China with a regional climate model

2020 ◽  
Vol 80 (2) ◽  
pp. 147-163
Author(s):  
X Liu ◽  
Y Kang ◽  
Q Liu ◽  
Z Guo ◽  
Y Chen ◽  
...  
Keyword(s):  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Radiant Energy ◽  
Energy System ◽  
Radiation Budget ◽  
Shortwave Radiation ◽  
Monsoon Region ◽  
Clear Sky ◽  
Sky Conditions

The regional climate model RegCM version 4.6, developed by the European Centre for Medium-Range Weather Forecasts Reanalysis, was used to simulate the radiation budget over China. Clouds and the Earth’s Radiant Energy System (CERES) satellite data were utilized to evaluate the simulation results based on 4 radiative components: net shortwave (NSW) radiation at the surface of the earth and top of the atmosphere (TOA) under all-sky and clear-sky conditions. The performance of the model for low-value areas of NSW was superior to that for high-value areas. NSW at the surface and TOA under all-sky conditions was significantly underestimated; the spatial distribution of the bias was negative in the north and positive in the south, bounded by 25°N for the annual and seasonal averaged difference maps. Compared with the all-sky condition, the simulation effect under clear-sky conditions was significantly better, which indicates that the cloud fraction is the key factor affecting the accuracy of the simulation. In particular, the bias of the TOA NSW under the clear-sky condition was <±10 W m-2 in the eastern areas. The performance of the model was better over the eastern monsoon region in winter and autumn for surface NSW under clear-sky conditions, which may be related to different levels of air pollution during each season. Among the 3 areas, the regional average biases overall were largest (negative) over the Qinghai-Tibet alpine region and smallest over the eastern monsoon region.

Sign in / Sign up

Export Citation Format

Share Document