Avaliação da relação entre eficiência energética e geração própria no ciclo de vida do edifício.

Abstract

The energy demand for use in buildings has one of the largest shares of total energy expenditure worldwide. In Brazil, it represents more than half the total consumption of electricity. In order to conserve natural resources, it is essential to avoid waste thus minimise energy consumption from non-renewable sources. This can be achieved by energy efficiency actions or by its generation through renewable sources, preferably at the own local of consumption. This work’s research problem refers to a search for the balance between these actions. How can one evaluate the best relation between them? The hypothesis explored in this research was that an energy evaluation over the entire life cycle of a building can answer this question by balancing the improvement of the building to avoid energy losses and to produce energy, coupled with the increase in embodied energy that these actions add to the building. The aim of the research was to propose an evaluative method that can be used for decisionmaking among them, targeting the equilibrium point. The adopted method consists in obtaining models of Brazilian single-family buildings and the values of embodied energy of the materials and systems that compose them; simulating operational consumption and onsite energy production; and in the variation of parameters in order to obtain the best relation between efficiency and generation. For this, only the photovoltaic solar source was considered. The models chosen represent a house with inefficient characteristics and another that could be classified as Passive House (PH). The results showed an estimated operational consumption of 59.7 kWh/(m2.a) and embodied energy of 42 kWh/(m2.a) for the inefficient model (model 1) without generation, totalling 101.7 kWh/(m2.a) in the life cycle of this model. Meanwhile, the PH model (model 2) showed 33.6 kWh/(m2.a) in operating consumption and 55 kWh/(m2.a) in embodied energy, totalling 88.6 kWh/(m2.a) in its life cycle. When owning photovoltaic generation, both models became net zero-energy buildings (NZEB), without occupying all the available area for the photovoltaic modules. Even with the increase in the embodied energy given by the better insulation of the envelope and the photovoltaic system, the energy produced by this system predominated and reduced the total consumption in the life cycle. These results show that the abundance of solar radiation incident in the Brazilian territory makes it possible to get NZEB status and even energy surplus in single-family houses in Brazil, even if bioclimatic principles are neglected. In spite of this, this work concluded that there is a need to combine energy efficiency with local generation, to avoid wasting natural resources, because other types of buildings, under different conditions, could not be as sustainable as the studied ones and therefore require the use of energy generated from non-renewable sources.