A method for estimating the geographical distribution of the available roof surface area for large-scale photovoltaic energy-potential evaluations

A rigorously founded assessment of the potential of renewable energies is essential for the development of energy policies and regulations. Usually, a hierarchy of potentials are calculated which gradually include restrictions for the use of a specific renewable resource. This paper deals with the estimation of the technical potential of roof-integrated photovoltaic systems. The most restrictive step when estimating this potential for large-scale territories is the estimation of the roof available area in existing buildings, for which no direct data exists. The methodology proposed in this paper allows to estimate the roof area available for solar applications and also quantify the error made in this estimation. It is based on easily accessible data (such as land uses and population and building densities) and on a statistically representative stratified-sample of vectorial GIS maps of urban areas. The main point in this sampling process is that the stratification is done based on a finite set of average building typologies which comprises every urban area in the region of study. An interesting characteristic emerging from the proposed methodology is its scalability and the possibility of being used from regional to continental scales. This methodology is applied in this work to Spain and a mean available area for photovoltaic equipment on roofs of 14.0±4.5m2/ca. with a confidence level of 95% is obtained. Additionally, results are given for the technical limit of production of roof-integrated photovoltaic energy.