The influence of latitude and sky conditions on daylight harvesting in buildings

Abstract

The potential of daylight harvesting is related to the building location. However, climatic zonings adopted by energy efficiency programs focus only on the thermal performance, neglecting important variables of the buildings’ luminous performance. This paper aims to investigate the relationship between the angle of solar incidence, the annual occurrence of clear sky, and the annual lighting energy consumption when daylight harvesting is practiced. The lighting consumption of a square floor space, orientated in the cardinal directions, was simulated for 20 Brazilian cities. The frequency of the 15 CIE sky types was determined for each city using weather files and the angle of solar incidence was calculated for each hour of the year. The analysis comprised graphical exploration, Pearson's correlation, and multiple regression. The sensitivity of the consumption to the other two variables could be perceived in the hourly but not the annual analysis. The correlation between annual consumption and latitude was more robust for the intertropical range, with increased consumption moving south, and varied significantly for each orientation. It was concluded that, although relevant, the variables are not representative of variations in annual lighting consumption for application in climate zoning.