An assessment of roof-mounted PV capacity over a local region can be accurately calculated by established roof segmentation algorithms using high-resolution light detection and ranging (LiDAR) datasets. However, over larger city regions often only low-resolution LiDAR data is available where such algorithms prove unreliable for small rooftops. A methodology optimised for low-resolution LiDAR datasets is presented, where small and large buildings are considered separately. The roof segmentation algorithm for small buildings, which are typically residential properties, assigns a roof profile to each building from a catalogue of common profiles after identifying LiDAR points within the building footprint. Large buildings, such as warehouses, offer a more diverse range of roof profiles but geometric features are generally large, so a direct approach is taken to segmentation where each LiDAR point within the building footprint contributes a separate roof segment. The methodology is demonstrated by application to the city region of Leeds, UK. Validation by comparison to aerial photography indicates that the assignment of an appropriate roof profile to a small building is correct in 81% of cases.Keywords: PV capacity; PV output; LiDAR; Roof profile; Solar resource; City region
IntroductionPhotovoltaics (PV) are viewed as a key climate change mitigation technology. To achieve this potential will require the large scale installation of PV, either on rooftops or as ground mounted arrays [1]. Installing highly distributed PV within city environments, such as on building rooftops and facades, locates electricity generation close to electricity end use, reducing the requirement for modifications to the electricity distribution network and minimizing transmission losses. Roof mounted PV also avoids the cost and competition for land, and the possible social and environmental impacts associated with large arrays of ground mounted panels [2]. An accurate assessment of the potential roof-mounted PV capacity in city regions is an essential component for establishing regional and national carbon reduction policies and informing investment decisions [3]. However, such assessments are not straightforward because of the range in size, orientation, pitch, and geometric complexity typically found in roof profiles.Previously reported methods to calculate the potential PV capacity over a city region include image analysis of geometrically-corrected high-resolution aerial photography [4,5], statistical approaches based on correlations between building class, population, and roof profile [6][7][8], and roof profile reconstruction from light detection and ranging (LiDAR) point clouds [9][10][11][12][13][14][15][16][17][18][19][20].Methods that utilise LiDAR data usually employ an error-minimising plane-fitting algorithm that divides each roof in to an arbitrary set of planes, which are referred to as roof segments. While such methods report high accuracy for large geometrically simple roofs, such as warehouses, they invariably requir...