No abstract

To compute energy demand based on the reference years hourly averages of external variables are often generated in the smooth form. On the other hand, daylight should be evaluated in a shorter interval because human eyes perceive light in the moment of its occurrence. This study shows alternative to the description of annual daylight conditions based on statistic characteristics mean and median to create Daylight Standard Reference Year for Bratislava. Both methods are presented as contribution to the development of daylighting engineering. Authors are interested in lighting engineering to ensure satisfactory luminous environment at workplaces and in buildings for housing and recreation. Good daylighting in interiors is also related to the reduction of electricity consumption for lighting. This paper presents method for generation of daylight standard reference year DSRY based on one minute data measured at CIE IDMP stations. This reference year can be applied for evaluation of daylighting in the specific locality.

The aim of this study is to present a comparison of daylight evaluation after requirements of Slovak standard STN 73 0580 and after the new CEN criterion 300 lux median diffuse horizontal illuminance in three rooms with different plans and different size of windows. Minimum values of illuminance in lux calculated on the border of the working plane were investigated. This study shows how this new CEN criterion influences the length of working plane and size of its part usable for performance of visual tasks.

Levels of daylighting in nature continually changing and their daily courses are different day to day. Effectiveness of daylight utilisation in buildings depends on exterior luminous conditions resulting from sunny and sunless situations. Generally, prevailing interiors are illuminated by diffuse skylight during year but sunny orientated rooms can be often exposed by direct sunlight. To describe these conditions the occurrence of sky luminance patterns and light attenuation properties of atmosphere expressed e.g. by luminous turbidity factor are needed. This paper presents the comparison and evaluation of occurrences of ISO/CIE General Standard Sky and luminous turbidity factor in two distant years on the base of measured instantaneous global and diffuse horizontal illuminance, global and diffuse horizontal irradiance and zenith luminance taken during 1995 a 2002 at ICA SAS in Bratislava. The different occurrences of luminous situations described by general standard sky types were found. Results of the luminous turbidity factor calculation show that various atmospheric pollutions during sunny situations can be expected.

To better utilize natural sources in the performance of buildings during whole year the availability of detail data in time and for specific location plays key role. Such data offers ground measurements or databases of satellite images. Establishment and operation of CIE IDMP ground stations is quite expensive and there are a few active stations on the ground at this time. To study of irradiance availability in specific locality the data describing relevant local radiative conditions are needed. For this reason the satellite images offer sufficient information. The first part of this paper is focused on short introduction to the remote sensing and the Heliosat method. In the second part are presented results of the solar irradiance availability on the horizontal plane and their time changes based on the processing satellite images. The illuminance and irradiance data obtained at ground CIE IDMP station in Bratislava were used to proposed verify model for estimation of the global illuminance from irradiance. Cities Bratislava and Brno are relative close with distance 130 km and similar daylight climate of Central European climatic zone, therefore can be assumed that data from CIE IDMP station Bratislava can represent relation between photometric and radiometric variables and daylighting changes in Brno.