Nanofluidic osmotic generator enhanced by water-cooled thermal management of proton exchange membrane fuel cell stack

Proton exchange membrane fuel cells (PEMFCs) are a promising power generation technology owing to their high power density and zero emissions. However, a substantial portion of the input chemical energy is dissipated as low-grade waste heat during the stack operation, leading to inefficient overall energy utilization. Meanwhile, the salinity-gradient energy, which is widely available in natural water bodies, can be directly converted into electricity through a nanofluidic osmotic generator (NOG). Nevertheless, their large-scale application is constrained by their relatively low power density. This work proposes an NOG that utilizes thermal energy generated from a PEMFC stack through water-cooled thermal management. The hot water from the cooling plate is supplied to the dilute side of the NOG to enhance ion selective transport, realizing waste heat recovery for power generation enhancement. When the cooling water flow velocity is increased from 0.3 m·s⁻¹ to 0.9 m·s⁻¹, the maximum stack temperature decreases from 331.26 K to 311.12 K, while the thermal stress drops significantly from 23.87 MPa to 11.92 MPa. Utilizing hot water at 314.46 K, the NOG increases its maximum power density from 5.019 W·m⁻² at environmental temperature to 9.246 W·m⁻². Under thermal enhancement, adjusting the electrolyte solution pH to 11 raises the power density to 10.895 W·m⁻², and further increasing the ion concentration ratio to 100 yields an output power density of 15.065 W·m⁻². This integrated strategy provides a viable pathway for synergistically integrating thermal management and waste heat recovery in PEMFC systems to enhance nanofluidic osmotic energy conversion.