Dynamic GIS-Based 3D Solar Simulation Framework for Assessing VIPV in Urban Public Transport using GTFS and Driving Cycles

Vehicle-Integrated Photovoltaics (VIPV) represent a promising pathway to reduce the energy demand of electric bus fleets, particularly in urban environments where charging infrastructure constraints and operational costs are critical. This paper introduces a dynamic GIS-based 3D solar simulation framework that integrates General Transit Feed Specification (GTFS) data with advanced irradiation modeling to quantify VIPV potential along real-world bus routes. The methodology combines Copernicus Atmosphere Monitoring Service (CAMS) solar radiation datasets with hemispherical beam-projection shadow casting on standardized CityGML 3D city models, enabling detailed assessment of direct, diffuse, and reflected solar components under complex urban shadowing conditions. To assess the net impact of VIPV integration, GTFS-derived driving cycles are processed in conjunction with vehicle powertrain and consumption models, calibrated against experimental measurements from a field campaign in Luxembourg. This combined workflow provides time-resolved estimates of photovoltaic generation, energy consumption, and resulting battery state-of-charge, allowing direct comparison between baseline and VIPV-equipped operations. In a case study of TICE Line 1 in Esch-sur-Alzette in Luxembourg, rooftop PV (3.5 kWp, PR = 75 %) covers 2.8–4.1 % of annual traction energy. Summer clear-sky operation reaches daily yields of about 3.9 kWh/kWp. This contribution avoids up to ~146 standard 20–80 % state-of-charge charging cycles per year (about 98 cycles under real-sky conditions) and offers simple payback of 7–10 years at current electricity tariffs. The open-data, standards-based workflow is transferable to other cities and provides a reproducible tool for assessing VIPV in public-transport electrification strategies.