Importance of nanochannels shape on blue energy generation in soft nanochannels

Abstract

Energy production is one of today's most pressing issues. Finding alternative energy sources has become one of the hottest research areas for scholars due to the limited use of fossil resources. Using water sources of different concentrations is one of the newest methods of energy production. Due to the energy of mixing fluids, two fluids of different concentrations on both sides of a nanochannel membrane can produce energy. Given the costs and restrictions of studying complex systems experimentally, simulation is required to investigate their behavior and determine the best states. As a result, using an energy production strategy, this work explores the effect of nanochannel shape on the ion transfer behavior. Asymmetric (bullet, trumpet, cigarette, hourglass, and hill) and symmetric (cylindrical) geometries were utilized. The effects of different geometries, soft layer density, and concentration ratio on energy production considering the effect of ion partitioning in soft surfaces was investigated. A finite element numerical computation approach was employed to solve the Poisson-Nernst-Planck and Navier-Stokes equations at steady-state. The best geometry at various concentration ratios to create the most performance were: cylindrical and cigarette for osmotic current, hourglass and trumpet for transmission number, hourglass and trumpet for diffusion potential, cylindrical for electrical conductivity, cylindrical and trumpet for power capacity, and hourglass and trumpet for energy conversion efficiency, respectively. In the case of considering the ion partitioning at a concentration ratio of CH/CL=1000for trumpet geometry, raising the soft layer's charge density from NPEL/NA=25to100mol/m3 boosted the maximum produced power by about 25 times, from 0.215pW to 5.35pW.