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Thermoelectric energy conversion in complex fluids (2 propositions)

Contact: NAKAMAE Sawako, , sawako.nakamae@cea.fr, +33 1 69 08 75 38/93 07
Summary:
At SPHYNX, we propose two experimental internship opportunities on the thermoelectric energy conversion phenomena in ionic liquids and nanofluids. The positions are intended for M2 students, but highly motivated M1 students can also apply.
Possibility of continuation in PhD: Oui
Deadline for application:28/03/2023

Full description:
Thermoelectricity, a materials’ capability to convert heat in to electric energy has been known to exist in liquids for many decades. Unlike in solids, this conversion process liquids take several forms including the thermogalvanic reactions between the redox ions and the electrodes, the thermodiffusion of charged species and the temperature dependent formation of electrical double layer at the electrodes. The observed values of Seebeck coefficient (Se = - DV/DT, the ratio between the induced voltage and the applied temperature difference) are generally above 1 mV/K, an order of magnitude higher than those found in the solid counterpart.

At SPHYNX, we have two on-going research projects to understand and exploit the heat-to-electricity conversion mechanisms in such complex fluids.

1) Co-generation of heat & electricity using nanofluids (liquid suspensions of nanometer-sized additives) via hybrid solar-thermal collectors. In this project, we combine the Sun-light absorption and the thermo-electrodiffusion of nano-additives to simultaneously produce heat and electricity from the solar radiation1. A prototype device has been built (see figure) by our partner laboratory (National Optical Institute, INO, Firenze, Italy) and currently being tested at SPHYNX. For the nanofluids, we use maghemite (iron oxide, collaboration with Sorbonne U) nanoparticles in aqueous media known for their long-term stability, moderately elevated heat absorption capacity and improved thermoelectric efficiency2,3. The internship has for its short-term goal to benchmark the prototype feasibility by determining the extractable magnitude of heat generation, thermal gradient and the power-output as a function of the irradiation power and nanoparticle concentration. Upon its successful completion, the internship will be converted into a PhD thesis research project investigating the underlying laws of physics behind the solar radiation absorption (heat) and the thermoelectric potential and power generation and other associated phenomena in various types of nanofluids, as well as the development of larger and more evolved devices identifying the impact of cell geometry (including that of thermal insulator), fluid-flow patterns, etc.. (The candidate must apply for PhD scholarship).

2) Thermogalvanic energy conversion improvement in ionic liquids via by redox solvation and coordination chemistry. Room temperature ionic liquids (RTILs) are molten salts that are liquid below 100 °C and up to 200 – 400°C. Compared to classical liquids, they exhibit many favorable features such as high boiling points, low vapour pressure, high ionic conductivity and low thermal conductivity accompanied by higher Se values. The latter is believed to stem from a complex and strong ionic environment in the solvation/complexation layer surrounding the redox species unique to ionic liquids4,5. A clear understanding and the precise control of the speciation of metal ions and their impact on the structural entropy change of the solvation layer is a key to the rational design of future TEC liquids. The proposed internship is experimental, exploring first the relationship between the ionic constituents of the liquid (various RTILs and RTIL/solvent mixtures) the thermogalvanic effect of commercially available redox salts via Seebeck coefficient (voltage), impedance and power measurements. In the subsequent PhD period (funding available), the study will be extended to tackle the coordination chemistry of transition metal redox ions made with commonly available metals (Fe, Cu, etc), involving ), involving metal complexation studies, electrolysis, and spectral & electrochemical characterization methodologies (collaboration with IJCLab, UPSaclay).

In both projects, our long-term goal is to deepen the understanding of the bespoke compound thermoelectric phenomena in liquid media, and to demonstrate the application potential of complex thermoelectric liquids based on affordable, abundant and safe materials for thermal energy harvesting as an energy efficiency tool.

The ideal candidate will have strong background in Physics (thermodynamics) with some theoretical/practical notion of Chemistry (CPGE, undergraduate Physics/Chemistry double-major or Energy/Electrochemistry/Chemistry in Master 1/2). No numerical skills are necessary for these positions, however, basic data analysis skills are required. Hands on experience in the laboratory environment (glovebox handling, electronic hardware manipulation, etc.) is a plus.

Contact: Saco Nakamae 01 69 08 75 38, sawako.nakamae@cea.fr

References:

[1] Z. Liu et al., “Enhancement of solar energy collection with magnetic nanofluids,” Therm. Sci. & Eng. Prog., 8, 130 (2018).
[2] E. Sani, et al., “Multifunctional Magnetic Nanocolloids for Hybrid Solar-Thermoelectric Energy Harvesting,” Nanomaterials, 11(4), 1031; https://doi.org/10.3390/nano11041031 (2021).
[3] T. Salez et al., “Magnetic enhancement of Seebeck coefficient in ferrofluids,” Nanoscale Adv., 1, 2979 (2019).
[4] T. Salez “Effets thermoélectriques dans des liquides complexes: liquides ioniques et ferrofluides” Thèse de Doctorat, PSL Research University (2018)
[5] M. Beaughon « Thermoélectricité dans les solvants, liquides ioniques et ferrofluides » thèse de doctorat, l'université Paris-Saclay (2022)
Technics/methods used during the internship:
Voltage and current measurements Impedance measurements Data acquisition

Laboratory
Tutor of the internship

 

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