Numerical Study of Multi-Factor Coupling Effects on Energy Conversion Performance of Nanofluidic Reverse Electrodialysis

Based on the rapid advancements in nanomaterials and nanotechnology, the Nanofluidic Reverse Electrodialysis (NRED) has attracted significant attention as an innovative and promising energy conversion strategy for extracting sustainable and clean energy from the salinity gradient energy. However, the scarcity of research investigating the intricate multi-factor coupling effects on the energy conversion performance, especially the trade-offs between ion selectivity and mass transfer in nanochannels, of NRED poses a great challenge to achieving breakthroughs in energy conversion processes. This numerical study innovatively investigates the multi-factor coupling effect of three critical operational factors, including the nanochannel configuration, the temperature field, and the concentration difference, on the energy conversion processes of NRED. In this work, a dimensionless amplitude parameter s is introduced to emulate the randomly varied wall configuration of nanochannels that inherently occur in practical applications, thereby enhancing the realism and applicability of our analysis. Numerical results reveal that the application of a temperature gradient, which is oriented in opposition to the concentration gradient, enhances the ion transportation and selectivity simultaneously, leading to an enhancement in both output power and energy conversion efficiency. Additionally, the increased fluctuation of the nanochannel wall from s = 0 to s = 0.08 improves ion selectivity yet raises ion transport resistance, resulting in an enhancement in output power and energy conversion efficiency but a slight reduction in current. Furthermore, with increasing the concentration ratio c_H /c_L from 10 to 1000, either within a fixed temperature field or at a constant dimensionless amplitude, the maximum power consistently attains its optimal value at a concentration ratio of 100 but the cation transfer number experiences a monotonic decrease across this entire range of concentration ratios. Finally, upon modifying the operational parameters from the baseline condition of s = 0, c_H /c_L = 10, and ΔT = 0 K to the targeted condition of s = 0.08, c_H /c_L = 50, and ΔT = 25 K, there is a concerted improvement observed in the open-circuit potential, short-circuit current, and maximum power, with respective increments of 8.86%, 204.97%, and 232.01%, but a reduction in cation transfer number with a notable decrease of 15.37%.