Assessing the Solar Resource in Forested Urban Environments: Results from the use of a Photographic-Computational Method

Abstract

The paper presents a method for the assessment of the permeability of tree crowns to solar radiation. It is based on the use of software for computational treatment of photographic images and was developed with the goal of counting on a tool that would allow to quantify the available solar radiation in vegetated urban environments. The method evaluates the effect of the direct, diffuse and reflected radiation filtered through the canopy, in a single value. The results obtained with the proposed method are compared with those yielded by field measurements and by the manual counting of dots on a dot mesh overlaid on blown-up photographic images. Finally, the results arrived at by the application of the method, in low and high density urban environments and for the different seasons of the year, are presented. The values obtained indicate that the availability of the solar resource in winter as conditioned by tree crown's, varies between 46.23% and 24.09% and the blocking of the same in summer fluctuates between 80.27% and 85.47% depending in either case, on the tree species, its phenological features and its development stage.