DOE sensitivity analysis of urban morphology factors regarding solar irradiation on buildings envelope in the Brazilian tropical context

Tathiane Martins, Luc Adolphe, Leopoldo Bastos (ENSA Toulouse, PROARQ-UFRJ Brazil)

CHALLENGE - This paper addresses the two-fold sustainable energy challenge of tropical cities: the major potential in harnessing solar energy as renewable resource for local electricity production and the energy demand due to the undesirable solar heat gains in buildings. The case study is based on the tropical Brazilian city of Maceió. Since urban densification process produces great impact on the solar irradiation balance, especially on buildings envelopes, it is important to characterize the magnitude of this impact according to main morphologic and climatic parameters. 

SOLUTION - This study uses the reduced factorial DOE method with a Simplified Radiosity Algorithm (SRA), to evaluate the irradiation availability on building envelope, considering a large sample of contrasted urban geometry scenarios. A set of energy-related morphological parameters are assessed: floor area ratio, plot ratio, mean aspect, shape factor, verticality, contiguity, albedo, etc. Results indicate significant impact of the mean aspect, the buildings setbacks and the surface equivalent albedo. Establishing high values of mean aspect may result in a reduction of 130kWh/m2 year of solar irradiation on roofs and 146kWh/m2 year on West façade, while the increasing on the plot ratio may only reach a gain of 26kWh/m2 year on the irradiation of roofs.

BENEFITS - This study on the sensitivity of the main morphological factors gives important information about their contribution on the building responses. The tests created hierarchical factors for solar energy potential on roofs and solar control over vertical facades. To conduct the methodology, two softwares were coupled: Citysim, for the dynamic simulations of the solar irradiation availability of urban models, and modeFRONTIER, for the DOE analysis.