Estimating rooftop capacity for PV: Are we asking the right question?

Precise estimation of solar energy potential on pitched roofs is crucial for modelling photovoltaic (PV) installation scenarios. However, there is no national database of building characteristics in the UK. This paper begins by reviewing and testing a range of existing techniques for identifying roof characteristics. These all attempt to estimate roof area with varying degrees of accuracy. Rather than attempting to achieve this, a method is developed which assesses each roof to discover whether it is suitable for PV installation. That is, its properties should allow the installation of at least a minimum size photovoltaic system. This contribution provides a tool to assess PV potential on city-wide scales. It develops a pixel-based approach to estimation of solar energy potential over pitched roofs. This is achieved by a combination of publicly available building outline maps and LiDAR (Light Detection and Ranging) data. These are analysed by using a simple statistical technique within a Geographical Information Systems (GIS) environment. The accuracy of the new method is known, following validation against a large housing database. The method is mathematically simple. It is suitable for estimating rooftop capacity of mixed housing type developments.