Distribution of beam solar radiation in buildings. Effect on heating demand

This paper presents a geometrical method to evaluate sunspot position and area through a window on each wall of a parallelepiped room. This method provides fast calculations because the formulas are explicit. Then simulations were made with and without sunspot calculation. Four cases were tested: Sunspots calculated at each time step with the previous geometrical method. All the direct solar radiation on the floor. 60% of the beam solar radiation on the floor. Constant distribution coefficients calculated in a simple preliminary simulation. It appears that the heating demand for the second and the third cases is not well estimated. It therefore seems to be important to precisely calculate the direct solar radiation distribution in low-consumption buildings. If sunspots cannot be computed at each time step, the fourth case shows that when it is well evaluated, using constant coefficients only slightly change the heating demand.