Otimização multiobjetivo de um projeto de retrofit para melhorar o desempenho térmico e energético de um edifício público

Abstract

Final energy consumption by the buildings sector accounted for about a third of global consumption in 2020, with existing buildings (built more than ten years ago) being a significant portion, as they represent more than two-thirds of the entire building stock. Considering the importance of reducing the energy impact of existing buildings, this work carried out a multi-objective optimization study for a retrofit project of a public building. The analysis was performed through computer simulation using the EnergyPlus program, for thermoenergetic analysis, and the jEPlus+EA program, which uses the NSGA-II genetic algorithm for multi-objective optimization. The objectives of the problem were to minimize the energy consumption and the thermal discomfort of the occupants of the building. The design variables were: type of roof, type of external wall, type of external glass, window-to-wall ratio, solar absorptance of the roof, solar absorptance of the external wall, night ventilation, night ventilation setpoint and cooling set point. The optimization reaches a set of 51 optimal solutions that, compared to the base case, presented a potential for 19.58% of energy consumption reduction and up to 20.87% of thermal discomfort reduction. Among the optimal solutions, a single solution was selected, which showed an energy consumption reduction of 19.51% and an increase in thermal discomfort of 2.03%, compared to the base case. The highlighted design variables in the optimal solutions, occurring in an absolute or almost absolute way, were the lowest window-to-wall ratio of 0.45, the lowest solar absorptance of the roof of 0.2 and the type of external glass with the lowest solar heat gain coefficient. For some design variables, it was possible to observe a direct relationship with thermal discomfort, namely: night ventilation, night ventilation setpoint and cooling setpoint. Multi-objective optimization proved to be a suitable tool for analysis that helps decision-making in cases of a building retrofit. Through it, it was possible to observe the behavior of design variables, thus allowing attention to variables that matter more than others.