Identifying the geographical potential of rooftop systems: Space competition and synergy

Urban areas face severe challenges in mitigating and adapting to climate change within limited space. One solution is to develop multifunctional rooftop systems, which use underexploited urban rooftop spaces. Two main options have been to add greenery by installing extensive green roofs (EGRs) or to generate renewable energy by installing photovoltaic panels (PVs). Recently, combining the two systems on one rooftop (EGR-PV) to harvest both benefits has gained attention. Not every rooftop is suitable for such installations, which makes it difficult to estimate the scale of space a city can expect from rooftops to add greenery, renewable energy, or both. This study presents a geographical potential model using building parameters, a building stock layer, and LiDAR data to simultaneously identify the potential for installing EGRs, PVs, and EGR-PVs on rooftops, highlighting the competition and synergy between EGRs and PVs at the building level. As an empirical illustration to support future multifunctional urban rooftop space planning, Amsterdam was used as a case study. The results show that 47 % of rooftops are suitable for EGRs, which could expand the current greenery space by 6 %, and 55 % are suitable for PVs which could sufficiently provide electricity to households by 2030. Moreover, competition exists for 3.2 %, whereas synergy exists for 42 % of the existing rooftops.