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Abstract The problem of optimal power management for uncertain off-grid hybrid systems is studied in this paper. A suitable parametrization of the energy sources and sinks is used to obtain a graphical representation of the feasible set along with a direct observation of the solution and its piecewise description. The proposed approach pretends to clarify how the optimal solution migrates from the use of one source to another as the solar radiation changes and how the dynamic response of the sources restrict the feasible set. A power generation system (PGS) is used to study the limitations that the sun power variability and the parametric uncertainty impose on the optimality; being the PGS constituted by photovoltaic (PV) panels, a fuel cell (FC), an electrolyzer (E) and a battery bank. A simple optimal Power Management Strategy (PMS) is proposed as a result of the analysis and its performance is illustrated in a telecom facility for three different locations in Mexico. Results are shown indicating the viability of the strategy for highly variable environments. Highlights • A graphical approach for optimal power management is proposed. • A parametrization is used to allow simplification of the optimization problem. • The case of parameter uncertainty in the power hybrid system is analyzed. • Results demonstrate that optimal operation is possible in presence of uncertainty. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the limitations that impose the presence of uncertainty in the design of optimal energy management strategies (EMSs) for fuel cell (FC) hybrid electric vehicles. Using an electric powertrain constituted by a hydrogen FC and a battery bank, the fuel consumption minimization problem is analyzed in the presence of parametric uncertainty. The conditions that ensure that the nominal optimization problem matches the solution of the real (unknown) optimization problem are clearly stated. By observing that the uncertainty will limit the feasible solutions of the minimization consumption problem, supervisory control constituted by heuristic rules is proposed to face such limitations, resulting in a mixed optimal–heuristic EMS. The effect of the powertrain design, driving cycle, and initial conditions in the proposed strategy is discussed. Numerical simulations provide evidence of the advantages and features of the supervisory control strategy. [ABSTRACT FROM PUBLISHER]

Abstract: In this paper, the geometry and operation of membraneless laminar flow-based fuel-cells (LFFC) is analyzed. Three different fuel cell geometries are studied, these are: the conventional rectangular cell, a cylindrical cell and a star shaped cell. The geometries are derived from the principle of design of increasing the effective area of cathode while conserving the same volume-to-length ratio. Since the mixing and depletion widths are major factors that determine the cell performance, maximum Reynolds and Péclet numbers as well as fuel utilization are considered as variables of comparison. Furthermore, electrical characteristics as current density and total extracted current have been considered as well. Using finite element simulations, it is shown that for a HCOOH−O2 cell, improved fuel utilization of 89% and 68.2% can be obtained with star and cylindrical geometries respectively, in comparison to conventional rectangular geometry (42.4%). Moreover, the total extracted current is also improved, reaching percentages greater than 1200% and 400% for the star and cylindrical designs respectively. It is shown that moving liquid–liquid interface, it is possible to further increase the current density of the designs and therefore the total extracted current. [Copyright &y& Elsevier]

In this study, a robust current switching control of converters is proposed. It is proved that the controller is able to guarantee global current regulation, as well as the maximum voltage and current ripple, simultaneously. Such features make it ideal for implementing power-management strategies and to be used along fuel cells. The control scheme is shown to be robust against model uncertainty and since it is based on the piece-continuous model instead of average models, it is suitable for operation under a wide range of conditions. Moreover, its complexity does not increase with the number of cells. Experimental evidence of the advantages and features of the proposed control is presented in a two-cell boost converter. [ABSTRACT FROM AUTHOR]