Design of an innovative hydrogen ecosystem integrating renewable energy options with wastewater management for a sustainable city

• The proposed system produces electricity, hydrogen, and hot water from wastewater and solar energy. • The system produces 13.66 MW electricity, 0.07 kg/s H 2 , and dual thermal streams for heating applications. • The designed system operates at 38.88 % energy and 31.36 % exergy efficiencies. • Hydrogen is liquefied and stored to fuel ships and boats at the port station in Toronto. This study introduces a newly designed hybrid multigeneration system that integrates anaerobic digestion, solar photovoltaic panels, and bioelectrochemical cells to convert wastewater into electricity, hydrogen and domestic hot water in order to achieve sustainable cities. The system is designed to potentially consider the Ashbridges Bay Wastewater Treatment Plant in Toronto, using both solar and biogas resources for energy production. Key system components include a steam Rankine cycle, an organic Rankine cycle, and a microbial fuel cell-microbial electrolysis cell unit, which together support simultaneous waste treatment and clean energy generation. The designed system has an overall energy efficiency of 38.88 % and exergy efficiency of 31.36 %. The system achieves a net electrical output of 13.66 MW, while producing 0.07 kg/s of hydrogen and two streams of thermal energy at different temperatures to meet residential and industrial demands. The generated hydrogen is then liquefied and stored at a nearby refueling station located at the Toronto port, where it is utilized to fuel marine vessels such as boats and ships. The parametric studies demonstrate that boiler efficiency, biogas yield, and reference temperature significantly affect system performance. The proposed configuration offers a scalable solution for integrating renewable energy with wastewater treatment and hydrogen infrastructure for sustainable urban applications.