Loss factor-based tandem power generation unit for ionic osmotic energy conversion

Ionic osmotic energy conversion harnesses salinity-gradient energy through selective ion transport in charged nanochannels. While existing studies primarily focus on high-performance single-unit materials, large-scale applications require integration of multiple units to enhance power output. However, strong nonlinear coupling among ion transport, charge accumulation, and interfacial processes prevents simple linear scaling of individual unit performance, with key parameters and their coupling mechanisms at the system level remaining poorly understood. In this study, a loss factor ( Lf ) is proposed to quantify power loss in tandem power generation units (T–PGU). Based on an equivalent circuit model, a quantitative relationship between Lf and the electrical signal ratios of individual units in T–PGU is established. System parameters are further classified into shared operating and channel-specific categories for investigating power output and energy loss under varying conditions through experiments and simulations. Results reveal a trade-off between maximum output power ( P max ) and Lf with concentration variations. Increasing temperature enhances P max with minimal impact on Lf , while KCl electrolytes significantly improve performance, reducing Lf to 4 × 10 −4 compared to NaCl and LiCl. Additionally, tuning nanochannels with lower current enables simultaneous improvement in power output and reduction in Lf . Based on these findings, an optimization strategy involving temperature elevation, electrolyte substitution, and surface charge matching with pH regulation is proposed and validated, achieving 283% increase in P max and 92.5% reduction in Lf . This work provides a theoretical and experimental foundation for system-level optimization and scalable design of ionic osmotic power generation.