Liquid Thermoelectrics: Review of Recent And Limited New Data of Thermogalvanic Cell Experiments

Gunawan, Andrey; Lin, Chao Han; Buttry, Daniel A.; Mújica, Vladimiro; Taylor, Robert A.; Prasher, Ravi; Phelan, Patrick E.

doi:10.1080/15567265.2013.776149

Cited by 149 publications

(122 citation statements)

References 19 publications

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“…[1][2][3][4][5] Complementary to the solid thermoelectric technologies, liquid-based thermoelectrochemical cells, or simply, thermocells are attracting increasing attention as a cheap and scalable alternative. [6][7][8][9] Thermocells produce an electrical current through redox reactions when two electrodes are maintained at different temperatures. To enhance the thermocell performance (e.g., higher thermoelectric coefficient and larger electrical conductivity) various improvements are made through electrode materials, redox-couples, and electrolyte types, as well as the natural convection of liquids and the diffusion of dissolved ionic species.…”

Section: Introductionmentioning

confidence: 99%

Can charged colloidal particles increase the thermoelectric energy conversion efficiency?

Salez

Huang

Rietjens

et al. 2017

Phys. Chem. Chem. Phys.

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a Currently, liquid thermocells are receiving increasing attention as an inexpensive alternative to conventional solid-state thermoelectrics for low-grade waste heat recovery applications. Here we present a novel path to increase the Seebeck coefficient of liquid thermoelectric materials using charged colloidal suspensions; namely, ionically stabilized magnetic nanoparticles (ferrofluids) dispersed in aqueous potassium ferro-/ferricyanide electrolytes. The dependency of thermoelectric potential on experimental parameters such as nanoparticle concentration and types of solute ions (lithium citrate and tetrabutylammonium citrate) is examined to reveal the relative contributions from the thermogalvanic potential of redox couples and the entropy of transfer of nanoparticles and ions. The results show that under specific ionic conditions, the inclusion of magnetic nanoparticles can lead to an enhancement of the ferrofluid's initial Seebeck coefficient by 15% (at a nanoparticle volume fraction of B1%). Based on these observations, some practical directions are given on which ionic and colloidal parameters to adjust for improving the Seebeck coefficients of liquid thermoelectric materials.

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Section: Introductionmentioning

confidence: 99%

Can charged colloidal particles increase the thermoelectric energy conversion efficiency?

Salez

Huang

Rietjens

et al. 2017

Phys. Chem. Chem. Phys.

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“…Despite recent progress, however, the figure of merit (ZT) of thermoelectrics is limited to 2 at high temperatures and 1.5 below 100°C 10,11 . Seebeck effect in electrochemical system is also investigated for thermal energy harvesting in similar architectures as a TE device, but the efficiency achieved is usually lower than 0.5% below 100°C since the thermopower is limited by poor ionic conductivity of electrolyte, which is more than three orders of magnitude smaller than the electronic conductivity in state-of-the-art TE materials [12][13][14][15] . An alternative approach of electrochemical system for thermal energy harvesting is to explore thermodynamic cycle as in thermomechanical engines.…”

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confidence: 99%

An electrochemical system for efficiently harvesting low-grade heat energy

et al. 2014

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Efficient and low-cost thermal energy-harvesting systems are needed to utilize the tremendous low-grade heat sources. Although thermoelectric devices are attractive, its efficiency is limited by the relatively low figure-of-merit and low-temperature differential. An alternative approach is to explore thermodynamic cycles. Thermogalvanic effect, the dependence of electrode potential on temperature, can construct such cycles. In one cycle, an electrochemical cell is charged at a temperature and then discharged at a different temperature with higher cell voltage, thereby converting heat to electricity. Here we report an electrochemical system using a copper hexacyanoferrate cathode and a Cu/Cu 2 þ anode to convert heat into electricity. The electrode materials have low polarization, high charge capacity, moderate temperature coefficients and low specific heat. These features lead to a high heat-to-electricity energy conversion efficiency of 5.7% when cycled between 10 and 60°C, opening a promising way to utilize low-grade heat.

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“…4B). When no heat recuperation is used (η HR = 0), which simplifies the design, efficiency is 0.68% and 0.52% for 0-and 10-mV overpotential, respectively, and it is about threefold that of thermogalvanic cells (22,23). Moreover, we have shown before that heat recuperation efficiency (η HR ) in 50-70% can be readily achieved, and even higher efficiency is possible (9).…”

mentioning

confidence: 89%

Charging-free electrochemical system for harvesting low-grade thermal energy

Yang

Lee

Ghasemi

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

225

120

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Efficient and low-cost systems are needed to harvest the tremendous amount of energy stored in low-grade heat sources (<100°C). Thermally regenerative electrochemical cycle (TREC) is an attractive approach which uses the temperature dependence of electrochemical cell voltage to construct a thermodynamic cycle for direct heat-to-electricity conversion. By varying temperature, an electrochemical cell is charged at a lower voltage than discharge, converting thermal energy to electricity. Most TREC systems still require external electricity for charging, which complicates system designs and limits their applications. Here, we demonstrate a charging-free TREC consisting of an inexpensive soluble Fe(CN) 6 3−/4− redox pair and solid Prussian blue particles as active materials for the two electrodes. In this system, the spontaneous directions of the full-cell reaction are opposite at low and high temperatures. Therefore, the two electrochemical processes at both low and high temperatures in a cycle are discharge. Heatto-electricity conversion efficiency of 2.0% can be reached for the TREC operating between 20 and 60°C. This charging-free TREC system may have potential application for harvesting low-grade heat from the environment, especially in remote areas.waste heat harvesting | Prussian blue analog | nanomaterials | batteries A vast amount of low-grade heat (<100°C) exists in industrial processes, environment, solar-thermal, and geothermal energy (1-3). It is generally difficult to convert such low-temperature thermal energy into electricity due to the distributed nature of heat sources and low-temperature differential. Different technologies, such as solid-state thermoelectric energy conversion (4-7) and organic Rankine cycles (1, 8), are being actively pursued but face their own challenges in efficiency, cost, and system complexity. Recently, a new thermally regenerative electrochemical cycle (TREC) based on a copper hexacyanoferrate (CuHCF) cathode and a Cu/Cu 2+ anode was demonstrated by us for harvesting lowgrade heat (9). A high efficiency of 5.7% was achieved when the cell was operated between 10 and 60°C assuming a heat recuperation efficiency of 50% (9). TREC uses reversible electrochemical reactions to construct a thermodynamic cycle, and it is based on the temperature dependence of cell voltage (9-12). For a reversible fullcell reaction A+B → C+D (discharge), the temperature coefficient α is defined aswhere E is the full-cell voltage, T is the temperature, n is the number of electrons transferred in the reaction, and F is Faraday's constant. ΔG and ΔS are the partial molar Gibbs free energy and partial molar entropy change in full-cell reaction (12-14). To convert heat to electricity, the electrochemical cell is discharged from A+B to C+D at T 1 and recharged at a different temperature T 2 with lower voltage (Fig. 1 A and B). Consequently electricity is generated as the difference between the discharged and charged energy. The net electricity originates from heat absorbed in electrochemical reactions at th...

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Liquid Thermoelectrics: Review of Recent And Limited New Data of Thermogalvanic Cell Experiments

Cited by 149 publications

References 19 publications

Can charged colloidal particles increase the thermoelectric energy conversion efficiency?

Can charged colloidal particles increase the thermoelectric energy conversion efficiency?

An electrochemical system for efficiently harvesting low-grade heat energy

Charging-free electrochemical system for harvesting low-grade thermal energy

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