Assessing Passive and Active Solar Energy Resources in Cities Using 3D City Models

Abstract Many cities today are committed to increasing the energy efficiency of buildings and the fraction of renewables. However, quantitative data on urban energy performance are rarely available during the design stage of new towns or for rehabilitation scenarios of existing cities. Three dimensional city models based on the spatio-semantic data format CityGML offer powerful new methods for the quantitative evaluation of urban energy demand and costs, and simultaneously allow the simulation of renewable energy systems. Such a ‘semantically enriched’ models was used in this work for energy demand diagnostics, refurbishment forecast and renewable supply scenarios. A case study was done using this method in an existing urban quarter in Ludwigsburg/Germany. Based on its three dimensional representation, the photovoltaic potential has been calculated and compared with the electricity demand to establish the photovoltaic fraction. On the thermal side, the passive solar gains were simulated for each building in the city quarter to analyse the solar contribution for heating demand reduction. The simulations were validated with measured gas consumptions. Some rehabilitation scenarios have also been simulated. In such a moderately dense post-war district, the calculated energy savings potential reach in total 65%, equally distributed between heat savings following building envelope refurbishment, and electricity savings due to the installation of PV on the roofs.