A hydrogen supply system utilizing PEMFC exhaust heat and modular metal hydride tanks for hydrogen-powered bicycles

A compact hydrogen supply system for thermally integrating metal hydride (MH) tanks with a proton exchange membrane fuel cell (PEMFC) for a hydrogen-powered electric-assist bicycle (H-bike) is proposed. The system recovers the exhaust heat generated by the PEMFC to sustain hydrogen desorption and improve the system's energy efficiency. The results demonstrate that the split-tank strategy decreases thermal and pressure gradients and enhances heat transfer and hydrogen release. The honeycomb tank configuration further improves hydrogen desorption by promoting uniform airflow distribution around each tank, thereby improving exhaust heat utilization from the PEMFC. It employs a layer-adjustable configuration, facilitating the flexible adaptation of MH cartridge quantities to meet hydrogen demand and prevailing road conditions in urban areas. Under a PEMFC power output of 215 W, the system maintains a stable hydrogen flow rate for over 30 min, with a heat recovery efficiency of 22.62 %. Furthermore, increasing the number of MH cartridge layers significantly improves the thermal utilization of the system, achieving a utilization efficiency of 39.90 % with two layers. These findings confirm the feasibility and scalability of the proposed system for H-bike, highlighting its potential as a decentralized hydrogen supply solution for lightweight mobility and urban transportation applications. • A PEMFC–MH hydrogen supply system designed for hydrogen-powered bicycles (H-bike). • Exhaust heat of PEMFC is recovered via split-tank and honeycomb MH configurations. • The split-tank strategy reduces thermal/pressure gradients, thereby improving desorption uniformity. • A honeycomb arrangement enhances exhaust heat utilization and improves system energy efficiency. • A two-layer MH design achieves a 39.90 % thermal utilization efficiency at a 215 W PEMFC output.