With rising popularity of microscale thermophoresis for the characterisation of protein-ligand binding reactions and possible applications in microfluidic devices, there is a growing interest in ...considering thermodiffusion in the context of life sciences. But although the understanding of thermodiffusion in non-polar mixtures has grown rapidly in recent years, predictions for associated mixtures like aqueous solutions remain challenging. This review aims to give an overview of the literature on thermodiffusion in aqueous systems, show the difficulties in theoretical description that arise from the non-ideal behaviour of water-mixtures, and highlight the relevance of thermodiffusion in a biological context. We find that the thermodiffusion in aqueous systems is dominated by contributions from heat of transfer, hydrogen bond interactions and charge effects. However, the separation of these effects is often difficult, especially in case of biological systems where a systematic exclusion of contributions may not be feasible.
Ionic thermoelectrics is a recently developed topic in materials science. The thermodiffusion of ions can generate potentials that is orders of magnitude larger than traditional thermoelectric ...materials, which enables unique applications.
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The tremendous amount of wasted heat from solar radiation and industry dissipation has motivated the development of thermoelectric concepts that directly convert heat into electricity. The main challenge in practical applications for thermoelectrics is the high cost from both materials and manufacturing. Recently, breakthrough progresses in ionic thermoelectrics open up new possibilities to charge energy storage devices when submitted to a temperature gradient. The charging voltage is internally from the ionic Seebeck effect of the electrolyte between two electrodes. Hence electrolytes with high thermoelectric figure of merit are classified as ionic thermoelectric materials. Most ionic thermoelectric materials are composed of abundant elements, and they can generate hundreds of times larger thermal voltage than that of electronic materials. This emerging thermoelectric category brings new hope to fabricate low cost and large area heat-to-energy conversion devices, and triggers a renewed interest for ionic thermodiffusion. In this review, we summarize the state of the art in the new field of ionic thermoelectrics, from the driving force of the ionic thermodiffusion to material and application developments. We present a general map of ionic thermoelectric materials, discuss the unique characters of each type of the reported electrolytes, and propose potential optimization and future topics of ionic thermoelectrics.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Synopsis: thermodiffusion in nanoporous media is an important fundamental process in many environmental and technical applications from desalination to nuclear waste storage.
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...Understanding of thermal effects on ion transport in porous media is very important for environmental applications. The movement of ions along a temperature gradient is named thermophoresis or thermodiffusion. In nanoporous media, where the interaction of ions with solid–liquid interfaces has a significant influence on their migration, the theoretical understanding of thermodiffusion is still incomplete. Herein, we present experimental results for the thermodiffusion of cations in saturated nanoporous silica by the through-diffusion method. Both the experimental data and theoretical analysis indicate that the temperature-induced polarization of surface charges strongly influences ionic transport. Stated simply, the electric field in a liquid electrolyte confined in nanopores changes when the applied temperature gradients are altered, thereby affecting the motion of the nanoconfined ionic species. By applying an external temperature field, the gradient of the surface charge density leads to the charged aqueous species exhibiting strong temperature gradient-dependent electrophoretic mobility. When the thickness of the electrical double layer is comparable to the size of the nanopores, the theory used herein indicates that this kind of nonisothermal ionic mobility is up to one order of magnitude larger than classical thermophoretic mobility. This study improves the understanding of the underlying mechanisms that govern the transport of ions in nanoporous media, which could set the stage for diffusional metamaterials induced by specific thermal fields.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The Soret effect describes diffusive motion that originates from a temperature gradient. It is observed in mixtures of gases, liquids and even solids. Although there is a formal phenomenological ...description based on linear nonequilibrium thermodynamics, the Soret effect is a multicause phenomenon and there is no univocal microscopic picture. After a brief historical overview and an outline of the fundamental thermodynamic concepts, this review focuses on thermodiffusion in binary and ternary liquid mixtures. The most important experimental techniques used nowadays are introduced. Then, a modern development in studying thermal diffusion, the discovery of both integral and specific additivity laws, is discussed. The former relate to the general behavior of the substances in a temperature field according to their thermophobicities, which prove to be pure component properties. The thermophobicities allow for a convenient classification of the phenomenon, a simple interpretation and a proper estimation and prediction of the thermodiffusion parameters. The specific laws relate to the additivity of the particular contributions. Among the latter, we discuss the isotopic Soret effect and the so-called chemical contribution. From the theoretical side, there are kinetic and thermodynamic theories, and the nature of the driving forces of thermodiffusion can be either of volume or surface type. Besides analytical models, computer simulations become increasingly important. Polymer solutions are special as they represent highly asymmetric molecular systems with a molar mass-independent thermophoretic mobility. Its origin is still under debate, and draining and non-draining models are presently discussed. Finally, some discussion is devoted to ternary mixtures, which only recently have been investigated in more detail.
Hydrovoltaic Generators
In article number 2400529, Shaochun Tang and co‐workers reported a lotus‐inspired interfacial evaporation‐driven hydrovoltaic generator for efficient generation of water vapor ...and electricity from seawater. The freshwater‐electricity cogeneration integrated system can harvest a record‐breaking voltage reaching 105 V and a high freshwater harvesting rate up to 2.0 L m−2 h−1 in a well‐lit outdoor area.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
6.
Ionic thermoelectric supercapacitors Zhao, D; Wang, H; Khan, Z U ...
Energy & environmental science,
01/2016, Volume:
9, Issue:
4
Journal Article
Peer reviewed
Open access
Temperature gradients are generated by the sun and a vast array of technologies and can induce molecular concentration gradients in solutions via thermodiffusion (Soret effect). For ions, this leads ...to a thermovoltage that is determined by the thermal gradient Delta T across the electrolyte, together with the ionic Seebeck coefficient alpha i. So far, redox-free electrolytes have been poorly explored in thermoelectric applications due to a lack of strategies to harvest the energy from the Soret effect. Here, we report the conversion of heat into stored charge via a remarkably strong ionic Soret effect in a polymeric electrolyte (Seebeck coefficients as high as alpha i = 10 mV K-1). The ionic thermoelectric supercapacitor (ITESC) is charged under a temperature gradient. After the temperature gradient is removed, the stored electrical energy can be delivered to an external circuit. This new means to harvest energy is particularly suitable for intermittent heat sources like the sun. We show that the stored electrical energy of the ITESC is proportional to ( Delta T alpha i)2. The resulting ITESC can convert and store several thousand times more energy compared with a traditional thermoelectric generator connected in series with a supercapacitor.
Ever since the discovery of the Soret effect, numerous experimental and theoretical works have been accomplished to understand the phenomena in terms of scientific interpretation. There is published ...review articles existed focusing in different aspects of Soret effect such as, experimental techniques, theoretical approaches, and combination of both theoretical and experimental approaches. However, most of the articles focused on recent or short era only. It is essential for the novice researchers to have historical or chronological database of the works already done by others. In the contemporary study, a historical database of experimental and theoretical works has been offered. Major challenges, limitations, and technical hitches of performing experiments on ground (earth) condition has been selected, and cautiously deliberated. Contemporary experimental works performed in microgravity environment have been incorporated. All of the experimental methodologies and theoretical models have been addressed briefly. However, because of its popularity remarkable attention has been focused on the experiments with optical techniques, and theoretical models based on non-equilibrium thermodynamics.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The theoretical approach for mathematical modeling of the evaporative convection in a multiphase system with interface based on the use of an exact solution of governing equations is discussed. The ...mathematical model builds on the “diffusive” laws of the transfer of matter, momentum and energy and includes the interface boundary conditions formulated with respect to the conservation laws. The carried out compatibility analysis of the equations concludes that there are three classes of exact solutions of the system under consideration. One of the possible solutions is circumstantially studied in the framework of the evaporative convection problem in a bilayer liquid – gas system, where both phases are the binary mixtures. The convection-diffusion equations are used to govern the transfer of one selected component and its vapor in the liquid and gas layers, respectively. The thermodiffusion effect is taken into account additionally for more precise description of heat transfer processes. The impact of this effect on the concentration and thermal characteristics as well as on the mass evaporation flow rate is investigated. It is shown that the utilized solution can describe convective regimes appearing on a working area of a long plane channel under thermal load distributed with respect to longitudinal coordinate by means of quadratic law. The solution correctly predicts hydrodynamical, temperature and concentration parameters of convective flows arising in the bilayer system. Basic characteristics calculated by this solution are feasible when the system is slightly deviated from the thermodynamic equilibrium state, and mass transfer through the interface is weak.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We have measured diffusion, thermodiffusion and Soret coefficients of a dilute solution of polystyrene in toluene by means of the transient holographic grating technique of thermal diffusion forced ...Rayleigh scattering over a temperature range from 10 to 50 °C. The results show a systematic deviation from optical beam deflection measurements over a narrower temperature interval of the order of ten percent but the identical temperature dependence. A comparison with previous measurements from our laboratory, new control measurements and literature data does not lead to a clear conclusion about the correct values. From the diffusion coefficient a temperature independent hydrodynamic radius is obtained. Both the Soret coefficient and the viscosity-scaled thermodiffusion coefficient ηDT, for which a universal value has been reported in the case of asymmetric systems with large solute entities, decrease with temperature.
•The diffusion and thermodiffusion coefficients of polystyrene in toluene both increase with temperature.•The Soret coefficient of polystyrene in toluene decreases with temperature.•There is a systematic small deviation between optical beam deflection and transient holographic grating experiments.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this paper we consider a laminated beam system with thermodiffusion effects with two kinds of boundary conditions, in which the mass diffusion introduces a new critical thickness in addition to ...the conventional critical thickness of thermoelastic damping. By using the method of semigroup, we prove the system is global well posed. The polynomial stability is established by using frequency domain method if the wave speeds are nonequal. We also establish exponential decay of energy under the assumption of equal wave speeds. At last, we present some numerical experiments to illustrate our theoretical results. The result is new and is the first time when the stabilization of the laminated beam system with thermodiffusion effects is obtained.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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