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Front. Built Environ. | doi: 10.3389/fbuil.2018.00014

Solar energy potential assessment on rooftops and facades in large built environments based on LiDAR data, image processing and cloud computing. Methodological background, application and validation in Geneva (solar cadaster)

  • 1Institute for Landscaping Architecture Construction and Territory (inPACT), High School of Landscape Engineering and Architecture, University of Applied Sciences Western Switzerland, Switzerland
  • 2F.A. Forel, International University in Geneva, Switzerland
  • 3Architecture and Urban Studies, Fondazione Politecnico di Milano, Italy
  • 4INstitut d'ingénierie Informatique et des Télécommunications (inIT), High School of Landscape Engineering and Architecture, University of Applied Sciences Western Switzerland, Switzerland
  • 5Institute of System Engineering, HES-SO Valais-Wallis, Switzerland

The paper presents the core methodology for assessing solar radiation and energy production on building rooftops and vertical facades (still rarely considered) of the inner-city. This integrated tool is based on the use of LiDAR, 2D and 3D cadastral data. Together with solar radiation and astronomical models it calculates the global irradiance for a set of points located on roofs, ground and facades. Although the tool takes simultaneously roofs, ground and facades, different methods of shadow casting are applied. Shadow casting on rooftops is based on image processing techniques. On the other hand, the assessment on facade involves first to create and interpolate points along the facades and then to implement a point-by-point shadow casting routine. The paper is structured in five parts: (i) state of the art on the use of 3D GIS and automated processes in assessing solar radiation in the built environment, (ii) overview on the methodological framework used in the paper, (iii) detailed presentation of the method proposed for solar modelling and shadow casting, in particular by introducing an innovative approach for modelling the Sky View Factor (SVF), (iv) demonstration of the solar model introduced in this paper through applications in Geneva’s building roofs (solar cadaster) and facades, (v) validation of the solar model in some Geneva’s spots, focusing especially on two distinct comparisons: solar model versus fisheye catchments on partially inclined surfaces (roof component); solar model versus photovoltaic simulation tool PVSyst on vertical surfaces (facades).
Concerning the roof component, validation results emphasize global sensitivity related to the density of light sources on the sky vault to model the SVF. The low dense sky model with 145 light sources gives satisfying results, especially when processing solar cadasters in large urban areas, thus allowing to save computation time. In the case of building facades, introducing weighting factor in SVF calculation leads to outputs close to those obtained by PVSyst. Such good validation results make the proposed model a reliable tool to: (i) automatically process solar cadaster on building rooftops and facades at large urban scales, (ii) support solar energy planning and energy transition policies.

Keywords: Keywords: Urban solar cadaster, Shadow casting, Sky View Factor, Energy Management, 3D-Urban digital models, Cloud computing

Received: 19 Nov 2017; Accepted: 22 Feb 2018.

Edited by:

Vahid Nik, Lund University, Sweden

Reviewed by:

Graziano Salvalai, Politecnico di Milano, Italy
Silvia Coccolo, École Polytechnique Fédérale de Lausanne, Switzerland  

Copyright: © 2018 Desthieux, Carneiro, Ineichen, Morello, Boulmier, Abdennadher, Dervey and Ellert. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Gilles Desthieux, GD., High School of Landscape Engineering and Architecture, University of Applied Sciences Western Switzerland, Institute for Landscaping Architecture Construction and Territory (inPACT), Geneva, Switzerland,