Unified model of radiance patterns under arbitrary sky conditions

Kocifaj, Miroslav

doi:10.1016/j.solener.2015.02.019

Cited by 32 publications

(10 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The light guide can be fully characterized by its optical properties and boundary conditions, such as the light field entering the pipe at its upper interface. The latter can be predicted from the UniSky Simulator which is designed to model radiance patterns under arbitrary sky conditions [20].…”

Section: Theoretical Frameworkmentioning

confidence: 99%

See 1 more Smart Citation

An Accurate Prediction of Daylight Pipe Harvesting of Interior Space

Kómar

Kocifaj

2019

Applied Sciences

Self Cite

View full text Add to dashboard Cite

Featured Application: The results of this research are useful in correct assessment of daylighting quality in the interiors respecting the typical instability of sky states. The computations we have performed allow for designing the optimum energy-saving solutions for light-pipe systems. Abstract:The performance of a light guide under arbitrary meteorological conditions is difficult to predict numerically because none of the present methods can account for the random configuration of clouds. Although, partly cloudy skies typically occur very frequently in many regions over the globe, the effects of cloud sizes, distributions, or altitudes on the luminous effectiveness of a light guide remain virtually unknown. The physical installation of light guides does not allow for a controlled experiment in which a single parameter can be varied within a defined range, while holding all other parameters constant. Numerical modeling is the only practical way to provide deep insights on the role of a specific property, such as cloud coverage, and its importance relative to all others (e.g., atmospheric turbidity). We have developed a unique solution through linking the UniSky simulator and HOLIGILM (hollow light guide interior illumination method) tool, while providing for the first time a powerful method that can provide accurate predictions and understanding of the fundamental differences of light guide behaviors under homogeneous and inhomogeneous sky states. The use of homogeneous skies in low-accuracy empirical models often results in overestimated/underestimated effectiveness of some light-guide systems. The model we have developed can predict complex optical signatures that are normally impossible to reproduce using up-to date empirical models (e.g., the illuminance patterns due to isolated clouds or clouds traversing across the sky). The optical efficiency, average cosine and working-place illuminance are analyzed and compared in order to demonstrate the model capabilities.

show abstract

Section: Theoretical Frameworkmentioning

confidence: 99%

“…Based on the aforementioned theoretical approaches, the UniSky tool [20] has been linked to the HOLIGILM tool [25]. The UniSky solution provides the zenith-normalized spectral sky radiance or luminance distributions, accepting the optical properties of a local atmosphere.…”

Section: The Variety Of Effects the Broken Cloud Arrays Could Have Onmentioning

confidence: 99%

An Accurate Prediction of Daylight Pipe Harvesting of Interior Space

Kómar

Kocifaj

2019

Applied Sciences

Self Cite

View full text Add to dashboard Cite

show abstract

“…The sky radiance distribution can be obtained accurately using atmospheric radiative transfer models (Liang and Lewis, 1996;Kocifaj, 2009;Kocifaj, 2012;Kocifaj, 2015). These models are based on the total optical thickness of the atmosphere, the scattering ability of atmospheric layers and also the reflectance of underlying surface.…”

Section: Radiative Transfer Modelsmentioning

confidence: 99%

“…Indeed, in a cloudless atmosphere, the intensity contribution of multiple scattered light decreases rapidly and no more than three scatterings are usually considered. Under cloudy conditions, the effect of multiple scattered light can however be significant and splitting the relative luminance in two functions might produce high errors (Adamson, 1975;Kocifaj, 2015). Nevertheless, since the objective of this work is rather to attenuate the clear-sky background dependence upon zenith angle and Sun position than to estimate the clear-sky image perfectly, it is not senseless to consider only the first scattering order and use the separation variable strategy.…”

Section: Empirical Modelsmentioning

confidence: 99%

Modelling the clear-sky intensity distribution using a sky imager

et al. 2015

View full text Add to dashboard Cite

International audienceThis paper introduces a new empirical formulation of the clear-sky intensity distribution based on images acquired with a sky imager developed at the PROMES-CNRS laboratory (Perpignan, France). Both the formulation and image processing methodology are detailed and stand for key steps in the development of a high quality cloud detection algorithm. The work presented in this paper is a part of a research project which aims at improving solar plant control procedures using direct normal irradiance forecasts under various sky conditions at short-term horizon (5-30 min) and high spatial resolution (∼1 km 2). Modeling the clear-sky intensity distribution in real time allows clear-sky images to be generated. These clear-sky images can then be used to remove the clear-sky background anisotropy on images and so improve cloud detection algorithms significantly. Cloud detection is essential in short-term solar resource forecasting. The new formulation is especially designed for improving performance of the existing models in the circumsolar area. When tested over more than 2200 clear-sky images, corresponding to a solar zenith angle spanning from 24 • to 85 • , the new formulation outperforms a standard approach based on the All-Weather model (Perez et al., 1993) by 15% on the whole sky and more than 20% in the circumsolar area. Application of the methodology for the real-time cloud detection purpose is discussed at the end of the paper

show abstract

“…Averaged luminance distribution also suffers from loss of information on daily dynamics of luminance amplitudes. The latter can be important, e.g., for clouds accumulating in a sky quadrant opposite to the azimuthal position of the sun [7]. These clouds appear exceedingly bright compared to clear sky surrounding which luminance is reduced because of weak backscattering from realistically shaped aerosols.…”

Section: Introductionmentioning

confidence: 99%

Variability of Diffuse Daylight Due to the Diversity of Cloud Arrays

Petržala

Kocifaj

2021

Applied Sciences

Self Cite

View full text Add to dashboard Cite

Illuminance modeling that allows us to mimic or even replicate the dynamics of daylight changes is increasingly becoming a challenge for the development of more accurate prediction systems of natural light availability in building interiors or variations of insolation at arbitrarily oriented façades. We demonstrate that illuminance amplitude due to random cloud arrangement can vary over a wide range even when other atmospheric parameters remain unchanged. It follows from our systematic numerical modeling that diffuse illuminance predictions can be significantly improved by incorporating cloud coverage, mean cloud size, and cloud base altitude into daylight models. We show that any model of homogeneous luminance patterns would fail in modeling the illuminance amplitudes we can expect on horizontal and vertical planes under partial cloud coverage with individual clouds distributed randomly. However, these situations occur with high frequency in most of regions worldwide, thus the modeling results we obtained here are of high relevance to daylight modeling and solar energy systems as well.

show abstract

Unified model of radiance patterns under arbitrary sky conditions

Cited by 32 publications

References 30 publications

An Accurate Prediction of Daylight Pipe Harvesting of Interior Space

An Accurate Prediction of Daylight Pipe Harvesting of Interior Space

Modelling the clear-sky intensity distribution using a sky imager

Variability of Diffuse Daylight Due to the Diversity of Cloud Arrays

Contact Info

Product

Resources

About