Solar cadaster as a decision support tool for sustainable energy management in urban areas ::from the state of Geneva to the cross-border agglomeration

The development of solar energy is particular relevant in cities that consume the major part of energy demand. Dense areas limit the incoming sunlight and the deployment of urban solar power plants. Therefore, it is essential to make available tools that model the solar energy accessibility in the urban fabric. Today‘s availability of 3D information about cities offers the possibility for such modelling, involving a whole procedure from data acquisition from Airborne Laser Scanning (ALS), also called Light Detection and Ranging (LiDAR), to the environmental analysis through the image processing of digital urban models. Building roofs, but also potential usable surfaces like car-port or highways roofs and walls are considered for potential energy production. Vertical or building facades, which are particularly interesting for the production of solar energy during the winter months, are becoming more and more promising through the improvement of solar panel efficiency and the innovative concepts of Nearly Zero Energy Buildings (nZEB) and Building Integrated PhotoVoltaics (BiPV) concepts. However, facade modelling for solar analysis is not as explored as for roofs, since it requires much more complex tools based on 3D GIS data. In this framework, the paper introduces a tool for assessing solar radiation and energy production on building rooftops and vertical facades of the inner-city. This integrated tool is based on the use of LiDAR, 2D and 3D cadastral data. The paper first presents the methodological background of the tool, its application in Geneva (solar cadaster available through a Web-based interface customized for the public). Then, it discusses about the opportunities and constraints for making the tool useful for the different stakeholder and practitioners involved in urban, energy and building planning