Electrokinetic Analysis of Energy Harvest from Natural Salt Gradients in Nanochannels

Abstract

The Gibbs free energy released during the mixing of river and sea water has been illustrated as a promising source of clean and renewable energy. Reverse electrodialysis (RED) is one major strategy to gain electrical power from this natural salinity, and recently by utilizing nanochannels a novel mode of this approach has shown improved power density and energy converting efficiency. In this work, we carry out an electrokinetic analysis of the work extracted from RED in the nanochannels. First, we outline the exclusion potential effect induced by the inhomogeneous distribution of extra-counterions along the channel axis. This effect is unique in nanochannel RED and how to optimize it for energy harvesting is the central topic of this work. We then discuss two important indexes of performance, which are the output power density and the energy converting efficiency, and their dependence on the nanochannel parameters such as channel material and geometry. In order to yield maximized output electrical power, we propose a device design by stepwise usage of the saline bias, and the lengths of the nanochannels are optimized to achieve the best trade-off between the input thermal power and the energy converting efficiency.

A Filter Paper‐Based Nanogenerator via Water‐Drop Flow

“…Various energies have been harvested using many kinds of nanogenerators, such as triboelectric nanogenerators, PENGs, thermal–electric nanogenerators, and photoelectric nanogenerators . In addition, the as‐harvested energy has various resources, such as wind, heat energy, solar power, vibration, mechanical energy, electromagnetic waves, chemical energy, and water energy …”

“…[10][11][12][13] Various energies have been harvested using many kinds of nanogenerators, [4] such as triboelectric nanogenerators, [13] PENGs, [14] thermal-electric nanogenerators, [15] and photoelectric nanogenerators. [16] In addition, the as-harvested energy has various resources, such as wind, [17][18][19] heat energy, [20,21] solar power, [22] vibration, [23,24] mechanical energy, [25] electromagnetic waves, [26] chemical energy, [27] and water energy. [11,28,29] Therein, the nanogengerator induced from water-flow [30][31][32][33][34] and water evaporation [29,35] is a majority part of the water energy nanogenerator.…”

Enhancing the efficiency of energy harvesting from salt gradient with ion-selective nanochannel

“…The saturation is mainly due to the presence of surface charges on the nanochannel [30,31]. The predicted channel conductance (red line), taking into account the contribution of the surface charge density ( ), is given by the spacecharge model as demonstrated in our previous works:[32] ℎ = ∫ 1 ( + Λ + + − Λ − ) 0 Page 6 of 16 AUTHOR SUBMITTED MANUSCRIPT -NANO-120591.R1 A c c e p t e d M a n u s c r i p t 7 / 16…”

“…However, the surface charge density decreses due to the decrease of C trans , leading to the decreased ion selectivity by surface effect, eventually result in the decrease of V oc when the concentration gradient reached 1000fold. [32,33,35,43] Meanwhile, the resistance of the nanochannel On the other hand, it will greatly undermines the transmembrane concentration difference across nanochannels when decreasing the channel length and thus reduce the ion selectivity of nanochannel. [26,28,44] These two competing factors result in a moderate length (715nm) of nanochannel would make a good balance between in the resistance and the ion selectivity of nanochannel, and then lead to a high output power density.…”

Transport and surface charge density of univalent ion of polyvinyl chloride-based barium tungstate ion-exchange composite membrane for industrial separation of waste water

“…In the present study, a new inorganic ion-exchange composite membrane of PVC, mixed with barium tungstate (BT), was prepared. Various electrochemical parameters such as membrane potential, transport number, mobility ratio and surface charge density have been optimized by using TMS method even these methods are classical but still proving its strong results [23,24] and Nernst equation to check the validity of the membrane for the separation of various industrial processes. Among these parameters, the surface charge density was most important and dominant parameter because it was used for controlling the membrane phenomena [25–32].…”