Modeling and analysis of rooftop solar potential in highland and lowland territories: Impact of mountainous topography

The spatial quantification of solar resources is necessary for the deployment of solar systems and must consider the local specificities of territories, such as complex topography in mountainous areas. This paper presents a methodology for obtaining solar cadastres, based on the Solar Energy on Building Envelopes (SEBE) model incorporated in QGIS and applied to French municipalities. The differences in solar potential between plain and mountain villages are analyzed through the simulation of 92 carefully selected villages located in these two types of regions. The distributions of annual rooftop irradiation per building are obtained for each studied village and approximated with a Johnson's SU density function. From this arises the definition of two statistical indicators: the mode and the spread at one-third maximum. Main results include a mean decrease in the mode of 189 kWh/m2 and a higher dispersion of 69 kWh/m2 between mountain and plain villages. Two physical indicators, the Sky View Index (SVI) and the Diffuse Fraction Index (DFI), are defined to explain these differences in the shape of the distributions. Higher cloud covers (high DFI) and the presence of distant shading effects (low SVI), caused by terrain relief, explains respectively the smaller modes and the higher dispersion observed in mountainous areas. SVI, DFI and latitude are fed to a multiple linear regression model, allowing the estimation of distributions with smaller computational costs than the developed methodology. Overall, this analysis demonstrates that the characteristics of mountainous environments greatly influence solar resources and should be considered in energy planning.