salinity difference
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2022 ◽  
Author(s):  
Qi Sun ◽  
Weipeng Xian ◽  
Xiuhui Zuo ◽  
Changjia Zhu ◽  
Qing Guo ◽  
...  

Abstract The development of efficient thermo-osmotic energy conversion devices has fascinated scientists and engineers for several decades in terms of satisfying the growing energy demand. The fabrication of ionic membranes with a high charge population is known to be a critical factor in the design of high-performance power generators for achieving high permselectivity and, consequently, high power extraction efficiency. Herein, we experimentally demonstrated that the thermo-osmotic energy conversion efficiency was improved by increasing the membrane charge density; however, this enhancement occurred only within a narrow window and subsequently exhibited a plateau over a threshold density. The complex interplay between pore−pore interactions and fluid structuration for ion transport across the upscaled nanoporous membranes helped explain the obtained results with the aid of numerical simulations. Consequently, the power generation efficiency of the multipore membrane deteriorated, deviating considerably from the case of simple linear extrapolation of the behavior of the single-pore counterparts. A plateau in the output electric power was observed at a moderate charge density, affording a value of 210 W m−2 at a 50-fold salinity difference with a temperature gradient of 40 K. This study has far-reaching implications for discerning an optimal range of membrane charge populations for augmenting the energy extraction, rather than intuitively focusing on achieving high densities.


Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5828
Author(s):  
Zhi Zou ◽  
Longcheng Liu ◽  
Shuo Meng ◽  
Xiaolei Bian ◽  
Yongmei Li

Capacitive energy extraction based on double layer expansion (CDLE) is a renewable method of harvesting energy from the salinity difference between seawater and freshwater. It is based on the change in properties of the electric double layer (EDL) formed at the electrode surface when the concentration of the solution is changed. Many theoretical models have been developed to describe the structural and thermodynamic properties of the EDL at equilibrium, e.g., the Gouy–Chapman–Stern (GCS), Modified Poisson–Boltzmann–Stern (MPBS), modified Donnan (mD) and improved modified Donnan (i-mD) models. To evaluate the applicability of these models, especially the rationality and the physical interpretation of the parameters that were used in these models, a series of single-pass and full-cycle experiments were performed. The experimental results were compared with the numerical simulations of different EDL models. The analysis suggested that, with optimized parameters, all the EDL models we examined can well explain the equilibrium charge–voltage relation of the single-pass experiment. The GCS and MPBS models involve, however, the use of physically unreasonable parameter values. By comparison, the i-mD model is the most recommended one because of its accuracy in the results and the meaning of the parameters. Nonetheless, the i-mD model alone failed to simulate the energy production of the full-cycle CDLE experiments. Future research regarding the i-mD model is required to understand the process of the CDLE technique better.


2021 ◽  
Vol 13 (15) ◽  
pp. 2995
Author(s):  
Frederick M. Bingham ◽  
Severine Fournier ◽  
Susannah Brodnitz ◽  
Karly Ulfsax ◽  
Hong Zhang

Sea surface salinity (SSS) satellite measurements are validated using in situ observations usually made by surfacing Argo floats. Validation statistics are computed using matched values of SSS from satellites and floats. This study explores how the matchup process is done using a high-resolution numerical ocean model, the MITgcm. One year of model output is sampled as if the Aquarius and Soil Moisture Active Passive (SMAP) satellites flew over it and Argo floats popped up into it. Statistical measures of mismatch between satellite and float are computed, RMS difference (RMSD) and bias. The bias is small, less than 0.002 in absolute value, but negative with float values being greater than satellites. RMSD is computed using an “all salinity difference” method that averages level 2 satellite observations within a given time and space window for comparison with Argo floats. RMSD values range from 0.08 to 0.18 depending on the space–time window and the satellite. This range gives an estimate of the representation error inherent in comparing single point Argo floats to area-average satellite values. The study has implications for future SSS satellite missions and the need to specify how errors are computed to gauge the total accuracy of retrieved SSS values.


2021 ◽  
Author(s):  
Frederick Bingham ◽  
Severine Fournier ◽  
Susannah Brodnitz ◽  
Karly Ulfsax ◽  
Hong Zhang

Sea surface salinity (SSS) satellite measurements are validated using in situ observations 8 usually made by surfacing Argo floats. Validation statistics are computed using matched values of 9 SSS from satellites and floats. This study explores how the matchup process is done using a high- 10 resolution numerical ocean model, the MITgcm. One year of model output is sampled as if the 11 Aquarius and Soil Moisture Active Passive (SMAP) satellites flew over it and Argo floats popped 12 up into it. Statistical measures of mismatch between satellite and float are computed, RMS difference 13 (RMSD) and bias. The bias is small, less than 0.002 in absolute value, but negative with float values 14 being greater than satellites. RMSD is computed using an “all salinity difference” method that av- 15 erages level 2 satellite observations within a given time and space window for comparison with 16 Argo floats. RMSD values range from 0.08 to 0.18 depending on the space-time window and the 17 satellite. This range gives an estimate of the representation error inherent in comparing single point 18 Argo floats to area-average satellite values. The study has implications for future SSS satellite mis- 19 sions and the need to specify how errors are computed to gauge the total accuracy of retrieved SSS 20 values.


Energy ◽  
2021 ◽  
pp. 121055
Author(s):  
Tri Quang Bui ◽  
Ole-Petter Magnussen ◽  
Vinh Duy Cao ◽  
Wei Wang ◽  
Anna-Lena Kjøniksen ◽  
...  

Author(s):  
Johan Nilsson ◽  
David Ferreira ◽  
Tapio Schneider ◽  
Robert C. J. Wills

AbstractThe high Atlantic surface salinity has sometimes been interpreted as a signature of the Atlantic Meridional Overturning Circulation and an associated salt advection feedback. Here, the role of oceanic and atmospheric processes for creating the surface salinity difference between the Atlantic and Indo–Pacific is examined using observations and a conceptual model. In each basin, zonally averaged data are represented in diagrams relating net evaporation (Ẽ) and surface salinity (S). The data-pair curves in the Ẽ – S plane share common features in both basins. However, the slopes of the curves are generally smaller in the Atlantic than in the Indo–Pacific, indicating a weaker sensitivity of the Atlantic surface salinity to net evaporation variations. To interpret these observations, a conceptual advective-diffusive model of the upper-ocean salinity is constructed. Notably, the Ẽ – S relations can be qualitatively reproduced with only meridional diffusive salt transport. In this limit, the inter-basin difference in salinity is caused by the spatial structure of net evaporation, which in the Indo–Pacific oceans contains lower meridional wavenumbers that are weakly damped by the diffusive transport. The observed Atlantic Ẽ – S relationship at the surface reveals no clear influence of northward advection associated with the meridional overturning circulation; however a signature of northward advection emerges in the relationship when the salinity is vertically averaged over the upper kilometer. The results indicate that the zonal-mean near-surface salinity is shaped primarily by the spatial pattern of net evaporation and the diffusive meridional salt transport due to wind-driven gyres and mesoscale ocean eddies, rather than by salt advection within the meridional overturning circulation.


2020 ◽  
Vol 20 (6) ◽  
pp. 3242-3248
Author(s):  
Cheng-Ta Chiang ◽  
Tsung-Yuan Chen ◽  
Yi-Ting Wu

2020 ◽  
Vol 6 (11) ◽  
pp. eaax5015
Author(s):  
Matteo Alberghini ◽  
Matteo Morciano ◽  
Matteo Fasano ◽  
Fabio Bertiglia ◽  
Vito Fernicola ◽  
...  

Space cooling in buildings is anticipated to rise because of an increasing thermal comfort demand worldwide, and this calls for cost-effective and sustainable cooling technologies. We present a proof-of-concept multistage device, where a net cooling capacity and a temperature difference are demonstrated as long as two water solutions at disparate salinity are maintained. Each stage is made of two hydrophilic layers separated by a hydrophobic membrane. An imbalance in water activity in the two layers naturally causes a non-isothermal vapor flux across the membrane without requiring any mechanical ancillaries. One prototype of the device developed a specific cooling capacity of up to 170 W m−2 at a vanishing temperature difference, considering a 3.1 mol/kg calcium chloride solution. To provide perspective, if successfully up-scaled, this concept may help satisfy at least partially the cooling needs in hot, humid regions with naturally available salinity gradients.


2020 ◽  
Vol 453 ◽  
pp. 227840
Author(s):  
G.R. Iglesias ◽  
S. Ahualli ◽  
A.V. Delgado ◽  
P.M. Arenas-Fernández ◽  
M.M. Fernández

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