Urban geometry and electrical energy consumption in a tropical city

Urban heat islands have significant influence on cities’ energy consumption, however, there are only relatively few studies dealing with their relationship. There is not only a reduction on heating energy consumption, but also an increase on cooling load of buildings related to the spatial distribution of the urban heat island. Taking into account those relevant points of the urban thermal environment, a research project named CEU (which in Portuguese stands for “Consumo de Energia Urbano”, or Urban Energy Consumption) is being undertaken at the State University of São Paulo in Bauru, Brazil. The CEU Project studies the relevance of urban geometry on the electric energy consumption of medium sized cities, seeking the identification of efficient patterns of urban energy consumption for urban planning proposals. In this approach the urban geometry is described by the sky view factor of urban canyons. Barely studied for Brazilian cities, the relationship between sky view factors values and electrical energy consumption is the very core of this research. In order to allow the determination of sky view factors, the first step on the CEU Project was to develop a tool to work on a GIS environment. That tool called 3DSkyView is an algorithm to work with ArcView GIS 3.2. Allowing an easy and quick way of calculating and representing sky view factors, the 3DSkyView extension was applied for determining the urban geometry of some urban canyons in the city of Bauru, São Paulo, Brazil. Twenty measuring points were taken into account. The urban canyons studied varied its sky view factors value in a range from 60 to 88%. The electrical energy consumption of buildings within those canyons was collected. The data collected represented the monthly electrical energy consumption in the immediate vicinity of 20 measuring points. This information was cross -examined with the sky view factors values, allowing a spatial overview of the urban geometry influence on the energy consumption. The first results show that urban canyons presenting sky view factors larger than 70%, which means open urban canyons, appear to have an average of 20% more electrical energy consumption than those canyons with lower sky view factors, which varied from a range of 60 to 70%.The very first conclusion revealed that sun exposition related to open canyons in tropical climates can represent higher energy demand due to the use of air conditioning for cooling the environment or any kind of electrical appliance used to achieve indoor thermal comfort. On the other hand, lower sky view factors (less than 70%), which means that buildings are more shadowed, can reduce energy consumption. It is here although important to highlight that urban canyons with sky view factors lower than 60% were not studied. A more detailed data collection is to be carried out in the near future.