Search

Shaded areas of windows, solar thermal collectors or photovoltaic modules are of major importance for the calculation of solar heating- and cooling-loads of buildings as well as for the determination of thermal or electrical output of corresponding solar equipment. SOMBRERO, a PC-program written in Turbo-Pascal, calculates the GSC (geometrical shading coefficient), the proportion of shaded area of an arbitrarily oriented surface surrounded by shading elements as a function of time and location. Shading elements are treated as polygons (not necessarily rectangles) located in a plane and can be combined to bodies such as buildings or trees. They may also represent overhangs and side-wings of the building under consideration. Elements which are far away from the receiver area are treated as horizontal shading profiles. The reduction of (isotropic) diffuse radiation caused by different kinds of obstacles is calculated by means of view-factors. Calculated results of the GSC are stored in ASCII-format and can be used as an input for dynamic solar system simulation programs. This is demonstrated in two illustrative examples showing the coupling of SOMBRERO with SUNCODE and TRNSYS in order to calculate the effects of shading on passive solar heating and passive cooling, respectively.

For detailed mapping of global radiation received at ground the Heliosat method of Ecole Nationale Superieure des Mines de Paris, Sophia-Antipolis (France), is applied. Preliminary results of a validation for Germany are presented. Precision of Heliosat insolation estimates is assessed by comparison of monthly averaged hourly and daily sums and of weekly sums acquired in August 1994 and February 1995 with pyranometric measurements from 4 stations of the German Weather Service (DWD). The predictions RMS error amounts to 7% of the observed August 1994 monthly averaged daily global irradiation of 4285 Wh/[m.sup.2] and to 15% of the observed February 1995 monthly averaged daily global irradiation of 1297 Wh/[m.sup.2]. The error of the estimation of monthly averaged hourly global irradiation is less than 100 Wh/[m.sup.2]. These values are within the limits of what has been reported hitherto.