System Level Exergy Assessment of Strategies Deployed for Solid Oxide Fuel Cell Stack Temperature Regulation and Thermal Gradient Reduction

Abstract

Several operational strategies for Solid Oxide Fuel Cell (SOFC) temperature regulation and temperature gradient minimization at cell scale have previously been assessed by the authors (Amiri et al., Ind. Eng. Chem. Res., 2016). The application of such strategies at system scale, however, requires a numerical linkage between the cell and system performance metrics allowing simultaneous evaluation of the dominant process interactions. The objective of this study is to analytically examine the effectiveness and applicability of the mentioned thermal management methods at system scale. To achieve this, a system level exergy analysis is presented by using a modelling platform in which a detailed 4-cell short stack module and the Balance-of-Plant (BoP) are integrated. Linkage between the system performance metrics and the stack internal temperature gradient is specifically emphasized. For this, the exergy intensive points (unit operations) are identified throughout the plant. Subsequently, the effective strategies that had been employed for the cell level thermal management proposed in our previous work (Amiri et al., Ind. Eng. Chem. Res., 2016) are examined at the system level capturing the effects on the state of BoP exergy intensive components. Moreover, fuel design is proposed and evaluated as a potential thermal management strategy. Combination of variety of measures including the exergy destruction rates, the electrical and thermal efficiencies, and the stack internal temperature gradient provides a comprehensive set of data contributing to the SOFC system thermal management.

Micro solid oxide fuel cell thermal dynamics: Incorporation of experimental measurements and model-based estimations for a multidimensional thermal analysis

“…10-20 %) in the SOFC operation. In previous works co-authors have quantitatively shown that the utilisation of oxygen-enriched air (OEA) can improve the SOFC's efficiency at cell [20] and system level [21] causing thermal behaviour concerns. The efficiency rise essentially occurs due to two reasons (i) the catalyst sites are more effectively occupied by reactants (ii) higher partial pressure of oxygen boosts the reversible OCV.…”

“…Amiri et al, developed a model to simulate a planar SOFC at both the stack and the system scales [20] with a focus on the SOFC thermal management. Most of the models used for SOFC thermal management are steady-state models [21]. Whilst they are extremely useful for capturing internal hotspots and nonuniformities in the steady-state operation of SOFC, the thermal dynamics are not taken into account.…”

SOFC Stack and System Modeling, Fault Diagnosis and Control

“…It was shown that anode gas recycling could be used strategically for managing the gradients within the stack, while also enhancing fuel utilisation and water management. The thermal management challenges and opportunities were further investigated in subsequent work [20,30] in which we sought further operation relevant strategies to improve the SOFC thermal homogeneity. This work resulted in novel opportunities such as enriched air utilisation and also combination of various approaches to achieve optimum results.…”

The Effect of Biogas Origin on the Electricity Production by Solid Oxide Fuel Cells

“…This analogy is attributed to the origin of biogas, i.e., by the biomass from which the biogas has been produced, while the operating conditions selected for the conversion of organic material to biogas are also important for the electricity produced [6]. In this context, several layouts of stand-alone power plants have been proposed, where a fuel cell is inevitably included [7][8][9]. In the present project, a thermodynamics-based model for the optimization of the operation of SOFC-based power plants is presented under specific assumptions (for details, see Section 2).…”