Thermoelectric Energy Conversion in Nanochannels Filled with Ionic Liquids
Creators: name: Sarma, Rajkumar
name: Hardt, Steffen
Publisher: name: Zenodo
Year: 2022
Subjects: energy harvesting
green energy
seebeck effect
h2020
EU funded
waste heat
waste heat recovery
nanofluidics
electrochemistry
nanochannels
thermoelectric devices
electric double layer
ionic liquids
thermovoltage generation

description: TRANSLATE researcher Dr. Rajkumar Sama presented this work in the 75th Annual Meeting of the Division of Fluid Dynamics (APS 2022).

Abstract:

In the past few years, thermoelectric energy conversion in electrolyte-filled nanochannels has received increasing attention. The thermovoltage created with corresponding devices often exceeds that of solid-state thermoelectric devices. Usually, significant thermovoltages can only be generated in the case of overlapping electric double layers (EDLs) from opposing channel walls. Ionic liquids (ILs) can be regarded as molten salts and are fundamentally promising electrolytes because of their high density of primary charge carriers. For ILs, the standard scheme of computing the EDL thickness results in values in the range of Angstroms, which precludes EDL overlap for all practical purposes. However, recent experimental results [1] indicate that the effective charge carriers in confined ILs are actually pseudoparticles, i.e. clusters of many primary charge carriers that can partially dissociate in a thermally activated process. Based on the coupled Poisson-Nernst-Planck, Navier-Stokes and heat transport equations, we study thermovoltage generation in an IL-filled nanochannel with different temperatures applied to the two ends of the channel. In that context, the number density of effective charge carries is obtained from an Arrhenius equation. Next to the numerical model, we have developed an analytical model based on the long-wavelength approximation. The results indicate that for the same degree of EDL overlap, the thermovoltage obtained with ILs is significantly higher than that obtained with aqueous electrolytes, by about a factor of five at a wall zeta potential of 25 mV. The predictions of the analytical model agree very well with the numerical results. In total, our theoretical studies indicate that confined ILs bear a significant potential for thermoelectric energy conversion.

 

[1] Gebbie, M. A., Dobbs, H. A., Valtiner, M. Israelachvili, J. N. Long-range electrostatic screening in ionic liquids, PNAS, 2015, 112, 7432–7437.

The authors acknowledge funding by the TRANSLATE project of the European Commission, grant agreement ID: 964251
description: TRANSLATE is a €3.4 million EU-funded research project that aims to develop a new nanofluidic platform technology to effectively convert waste heat to electricity. This technology has the potential to improve the energy efficiency of many devices and systems, and provide a radically new zero-emission power source. The TRANSLATE project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement number 964251, for the action of 'The Recycling of waste heat through the Application of Nanofluidic ChannelS: Advances in the Conversion of Thermal to Electrical energy'. More information can be be found on the TRANSLATE project website: https://translate-energy.eu/