La spettroscopia d'impedenza elettrochimica come strumento di diagnostica predittiva per celle e stacks ad ossidi solidi (SOFC)

Responsabili di progetto

Sabrina Presto, Daria Evgenieva Vladikova

Accordo

BULGARIA - BAS - Bulgarian Academy of Sciences

Bando

CNR-BAS 2016-2018

Dipartimento

Scienze chimiche e tecnologie dei materiali

Area tematica

Scienze chimiche e tecnologie dei materiali

Stato del progetto

Nuovo

Proposta di ricerca

More than 20 years planar SOFC are continuously demonstrating big potential for improvements of the technology, exhibiting an impressive evolution in terms of material properties and reliability. However, more efforts are still needed for additional enhancement of performance, durability, reliability and costs. In this aspect an important target is the better understanding of degradation and lifetime fundamentals, which is closely related to the development of sophisticated testing techniques [1-5]. Since long term testing is required, wise solutions, based on the combination of accelerated testing strategies and degradation modeling are welcome. The expected impact is improvement of cells and stacks performance. In principle stacking has been considered a crucial point due to the accumulated losses in performance and durability on one hand and to the necessity of stacking in order to answer the power demands on the other hand. During the last two decades SOFC stacks with power outputs of typically several kilowatts have been manufactured to operate at temperatures ranging between 700 and 850 °C with various fuels (methane, natural gas, hydrogen) [6, 7]. A critical issue is the interface metal interconnect - active cell components. The reliability and durability of stacks is evaluated in terms of Degradation Rate (DR) and probability of failure (PF). Despite the achieved improvements in the cells, further PF and DR decrease is required in combination with market acceptable production costs.
The proposed collaboration aims at introducing innovative testing procedures based on Electrochemical Impedance Spectroscopy (EIS), which ensure early detection of different degradation phenomena taking place at cell and stack level.
The development of protocols for predictive diagnostic measurements would enable extension of SOFC devices lifetime by application of recovery actions before the real failure and would therefore represent a real breakthrough for the development of this technology.
Recently, an European Project named ENDURANCE was started with the support of the FCH- JU, which includes both the Bulgarian and the Italian team. The joint research proposed here would benefit from availability of real systems prepared in the frame of Endurance for application of diagnostic protocols and could also produce results easily exploitable in that context.
A number of different samples simulating critical parts or interfaces of cells and stacks will be analyzed by EIS under realistic conditions in order to find most important degradation
phenomena and consequent deviations in the impedance response.
A new approach called Intensive Active Tests and Analyses (IATA) will be explored. The IATA combines modulation of conditioning parameters with multi-parameters measurement and statistical analysis, complemented with EIS. The modulation of load current provides for a continuous measurement of the internal resistance and the volt-ampere characteristics of the samples. The gases modulation provides for separate assessment of anode and cathode performances together with an early identification of leakages. The precise separation of the cell's elements performance is achieved by EIS at variable work points (vwpEIS).

[1] C. Comminges, Q. X. Fu, M. Zahid, N. Y. Steiner, and O. Bucheli, "Monitoring the degradation of a solid oxide fuel cell stack during 10,000h via electrochemical impedance spectroscopy," Electrochim. Acta, vol. 59, pp. 367-375, Jan. 2012.
[2] M. S. Sohal, J. E. O'Brien, C. M. Stoots, V. I. Sharma, B. Yildiz, and A. Virkar, "Degradation Issues in Solid Oxide Cells During High Temperature Electrolysis," J. Fuel Cell Sci. Technol., vol. 9, no. 1, p. 011017, Feb. 2012.
[3] D. Larrain, J. Van herle, and D. Favrat, "Simulation of SOFC stack and repeat elements including interconnect degradation and anode reoxidation risk," J. Power Sources, vol. 161, no. 1, pp. 392-403, Oct. 2006.
[4] A. Nakajo, F. Mueller, J. Brouwer, J. Van, and D. Favrat, "Progressive activation of degradation processes in solid oxide fuel cells stacks/: Part I/: Lifetime extension by optimisation of the operating conditions," J. Power Sources, vol. 216, pp. 449-463, 2012.
[5] L. G. J. de Haart, J. Mougin, O. Posdziech, J. Kiviaho, and N. H. Menzler, "Stack Degradation in Dependence of Operation Parameters; the Real-SOFC Sensitivity Analysis," Fuel Cells, vol. 9, no. 6, pp. 794-804, Dec. 2009.
[6] R. J. Kee, H. Zhu, and D. G. Goodwin, "Solid-oxide fuel cells with hydrocarbon fuels," Proc. Combust. Inst., vol. 30, no. 2, pp. 2379-2404, Jan. 2005.
[7] Y. Zhao, C. Xia, L. Jia, Z. Wang, H. Li, J. Yu, and Y. Li, "Recent progress on solid oxide fuel cell: Lowering temperature and utilizing non-hydrogen fuels," Int. J. Hydrogen Energy, pp. 1-20, Aug. 2013.

keywords: SOFC degradation, predictive diagnostic, EIS

Obiettivi della ricerca

The application for a joint research project in the frame of 2016-2018 BAS-CNR collaboration aims at:
(i) development of an innovative diagnostic method for high temperature fuel cell, which would extend the lifetime of SOFC stacks; in particular a number of different samples simulating critical parts or interfaces of cells and stacks will be analyzed by EIS under realistic conditions in order to find most important degradation phenomena and consequent deviations in the impedance response. Moreover a new approach called Intensive Active Tests and Analyses (IATA) will be developed. The IATA combines modulation of conditioning parameters with multi-parameters measurement and statistical analysis, complemented with EIS.
(ii) common education and training of junior scientists (Ph.D. students and Post. Docs),
(iii) preparation of proposal(s) in FP8 "Horizon 2020". The topic of this proposal corresponds to the four priorities of the Program.

Ultimo aggiornamento: 25/04/2024