Raghunathan Rengasamy

In power networks, where multiple fuel cell stacks are employed in a series-parallel configuration to deliver the required power, optimal sharing of the power demand between different stacks is an important problem. This is because the total current collectively produced by all the stacks is directly proportional to the fuel utilization, through stoichiometry. As a result, one would like to produce the required power while minimizing the total current produced. In this paper, an optimization formulation is proposed for this power distribution control problem. An algorithm that identifies the globally optimal solution for this problem is developed. Through an analysis of the KKT conditions, the solution to the optimization problem is decomposed into off-line and on-line computations. The on-line computations reduce to solving a nonlinear equation. For an application with a specific V–I function derived from data, we show that analytical solutions exist for on-line computations. We also discuss the wider applicability of the proposed approach for similar problems in other domains.

The limited availability of conventional energy carriers has increased the demand for renewable energy sources to cater to the ever increasing energy demand. The present chapter focusses on phosphoric acid fuel cells (PAFCs) detailing their working principles and application potential. The different materials used in PAFCs, including electrolyte, catalysts and bipolar plates and their importance in the ultimate performance are summarized. The degradation behavior due to acid leaching which affect several components of the cell is outlined. Researchers’ contributions towards early identification of degradation of catalyst and catalyst support in particular due to the presence of excess quantity of phosphoric acid, is also described. The importance of having anticorrosive coatings on bipolar plates is outlined in view of achieving life enhancement of the cell operation. Significant work has been carried out in PAFC modeling (1D–3D, steady state and dynamic models) and these are reviewed. The important design considerations during scale-up such as gasket selection and its arrangement, planarity of electrodes, fabrication method of membrane electrode assemblies (MEAs), thermal stress management etc. are described in detail. The chapter outlines various applications explored from power ratings of 20–500kW and also future requirements to be addressed in material as well as engineering issues.