Effect of Sky Discretization for Shading Device Calculation on Building Energy Performance Simulations

Ismael R. Maestre, Juan Luis Foncubierta Blázquez, Francisco Javier González Gallero and J. Daniel Mena Baladés
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Ismael R. Maestre: Escuela Politécnica Superior de Algeciras, University of Cadiz, 11202 Cadiz, Spain
Juan Luis Foncubierta Blázquez: Escuela Politécnica Superior de Algeciras, University of Cadiz, 11202 Cadiz, Spain
Francisco Javier González Gallero: Escuela Politécnica Superior de Algeciras, University of Cadiz, 11202 Cadiz, Spain
J. Daniel Mena Baladés: Escuela Politécnica Superior de Algeciras, University of Cadiz, 11202 Cadiz, Spain

Energies, 2020, vol. 13, issue 6, 1-14

Abstract: The calculation of sunlit surfaces in a building has always been a relevant aspect in building energy simulation programs. Due to the high computational cost, some programs use algorithms for shading calculation for certain solar positions after discretization of hemispherical sky. The influence of the level of discretization on the estimation of incident direct radiation on building surfaces, as well as on the required computational times, are studied in this work. The direct solar energy on a window for a year, with simulation time steps of five minutes, has been simulated by using an algorithm based on Projection and Clipping Methods. A total of 6144 simulations have been carried out, varying window sizes, window orientations, typologies of shading devices, latitudes and discretization levels of the hemispherical sky. In terms of annual incident solar energy, the results show that maximum error values are about 5% for a low level of angular discretization. Errors up to 22% in hourly incident solar energy have been estimated for some of the configurations analysed. Furthermore, a great number of configurations show errors of shading factor on a window of up to 30%, which could be most relevant in studies of natural lighting. The study also shows that the improvement achieved by the most accurate discretization level implies an increase in computational cost of about 30 times.

Keywords: shading calculations; sky discretization; building energy simulation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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