Boosting osmotic energy harvesting in conical nanoporous structure through parallel flow

Osmotic energy conversion in nanopores has attracted much attention for its green and sustainable advantages. However, in practical nanoporous membrane power generation systems, significant ionic concentration polarization (ICP) effect occurs, which impairs the output performance of power generation. To address this challenge, this work proposes a novel strategy of introducing parallel flow within conical nanoporous structure to mitigate ICP and enhance power generation performance. Research indicates that applying parallel flow on the low-concentration side can effectively mitigate ICP, and the maximum power improves with increasing flow velocity. The maximum power of the system exhibited a 3.35 times enhancement at a flow velocity of Uc = 0.04 m/s (parallel flow applied exclusively on the low-concentration side), compared to scenarios without parallel flow. This result clearly demonstrates the remarkable efficacy of parallel flow in boosting power generation performance. Notably, the application of parallel flow solely at the high-concentration side induces anomalous attenuation of maximum power with flow velocity. Moreover, under parallel flow conditions on the low-concentration side, increased velocity significantly enhances energy conversion efficiency at high concentration gradients. This enhancement reaches up to 316.83 times compared to scenarios without parallel flow. Conversely, at lower concentration gradients, reduced flow velocity is required to maintain performance gains. This work explores the combined effect of parallel flow and ionic concentration gradients in porous systems, which offers new insights for optimizing the design of salinity gradient power generation systems.