This paper describes a project for the integration of mini-hydro renewable energy in the trolleybus traction lines and in the electric battery operated mini-buses. Given the nearby hydropower resource of the Mondego river, a study was carried out in order to assess the technical and economical feasibility of hydropower production at an already existing multi-purpose mobile dam-bridge, located in Coimbra, Portugal, where a very low head run-of-river small-hydropower plant can be installed. As the main civil works have already been done, the hydropower installation costs are significantly reduced because the investment mainly resumes to hydro-mechanical, hydro-electrical and electrical equipment, with expected low hydraulic structure impact, as well as minimum environmental and visual impacts. The optimization of the hydroelectric production takes into account the seasonal water supply demands for agricultural, municipal and industrial use, the water discharges from the upstream reservoir system of Aguieira–Raiva–Fronhas, the very low head turbines state of the art technology, the physical constraints of the structure and the special feed-in tariff for renewable power plants. The small-hydropower plant, coupled with the electric public urban transportation fleet, will contribute to a sustainable clean mobility concept, reducing electric grid transportation losses by decentralized production and reducing greenhouse gases emissions, contributing to urban air quality improvement and to the Kyoto Protocol fulfillment.