Study On The Sky Luminance Distribution Model By Information Methods

Make full use of natural light, pursue ecosystem and sustainable development and save lighting power is most important for the energy gradually lacks now. The most important factor of the building makes use of natural light is the sky luminance distribution, so the main study of daylight is the law of sky luminance distribution.In this paper, base on the systematic analysis of the sky luminance distribution model developed by predecessors, studying the sky luminance distribution model by information methods, the sky luminance distribution model only related to the zenith luminance conversion factor. And the zenith luminance conversion factor only depends on solar altitude angle, not concerned in geographical. It has universal application. In other words, in theory we only need a region of data. This provides a new approach and new ideas for the study of distribution of sky luminance, and it will have a grate affect on the building daylighting design, building energy conservation, adequate and reasonable use of solar energy.From the atmosphere radiation theory, this paper draw the important conclusion that sky luminance root solar radiation in atmosphere scattering and absorption and impact of sky luminance is the dominant parameters of extinction coefficient (or optical thickness), the single-scattering albedo and the phase function for study the sky luminance distribution laid a theoretical foundation.Reference sky is used to minimize the sky types to represent the fantasticality real sky, and facilitate the daylighting design and calculation. The paper analysis the reference sky and real sky in the different climate conditions, and know the relationship between the real sky and the reference sky. Through analysis the atmospheric optical parametric which impact of sky luminance, the paper bring forward the atmosphere equivalent model assumptions, getting the mathematical expression of sky luminance model by information methods, gaining the various parameters characteristics of the expression and scope of the changes and trends under different weather conditions. This provides the basis and premise for sky classification and study sky luminance distribution by information methods.The paper use the multi-city and large-scale daylihting-Climate Observing test-data accumulated over the years, through the sky meteorological parameters study on the impact of sky luminance distribution, bring forward the sky classification standard of reference skies, that is, through the Gradually change the situation of surface conditions on the sun, the sky conditions (cloud cover) and the horizon to the zenith luminance, the paper divide the sky into six types. The classification method is helpful to observation and differences, and more accurate reflection of the sky type, avoiding the dim defect of general sky luminance standard classification existing CIE. This paper analysis that the references skies model adjustment coefficient a, b, c, d and e impact the sky luminance distribution by information methods, getting value range in different sky conditions and the foundation parameters study on the sky luminance model.This paper uses a new heuristic arithmetic to solve complex optimization problem—ant colony algorithm to study the sky luminance distribution model, ant colony algorithm have many advantages ,such as intelligent search, global optimization, robustness, distributed computing and easy to integrate with other methods. Through the ant colony algorithm optimization processes infection elements of the sky luminance, we get the coefficient value of the expressions of sky luminance relative distribution. At the same time we have also developed a set of convenient and practical sky luminance model calculation software, It can provide an intuitive and easy calculation.The paper also study the testing methods of digital camera measure sky luminance, through the digital camera with fisheye lens take photo sky hemisphere, using developed by ourselves image processing system extracting records from sky luminance data information. Through compared the actual measurement data and the calculated value of theoretical model gaining by information method, its error is lesser. This is undoubtedly very valuable for daylighting utilization and especially for daylighting design of high precision and standardization in theory and application.