The recent advent of high quality, realistic 3D city models is creating new possibilities for analyses and visualisations of solar irradiance and photovoltaic (PV) potential at an urban level. A 3D city model of Newcastle (UK) is used to demonstrate potential applications for locating solar panels (i.e. which surfaces within the model), and positioning them (i.e. where on a given surface). After geometrically validating the model, a 3D PV assessment tool is developed for locating suitable surfaces, which accounts for 3D geometric properties (surface area, slope, aspect), clear-sky solar irradiance estimates, and annual PV estimates. Optimal sub-sections of a selected surface are then identified using 3D shadow detection analyses. Outputs include a daily animation of the shadows cast across the surface each hour, and a static image displaying mean non-shaded percentage patterns on the surface.