Configuration of a Fuel Cell system. Clues to choose between a modular or single stack-based design

In renewable energy systems based on fuel cells, these can suffer deterioration derived from start-up/stop cycles, load changes or run-time operation. This paper analyses the viability of using a fuel cell system built from a high power single stack or from multiple low-medium power stacks under fixed or variable power operation in a renewable energy system which includes Solar Panels, Wind turbines, Polymer Electrolyte Fuel Cells, Batteries and Electrolyzer. The aim of this comparison is to improve the system efficiency. To get this target, technical and economical optimization parameters have been taken into account in order to improve the fuel cell system lifetime, reduce operation and maintenance costs guarantying the power balance, the hydrogen stock and keeping the restrictions of the batteries' state of charge. For this purpose, a simulator has been developed in order to test different configurations of the fuel cell system. The configurations analysed are (A)-a modular PEFC based on two 3.4 kW stacks working at 2 kW every stack, (B)-a single 6.8 kW stack working at 4 kW power, (C)-a single 6.8 kW stack working at variable power and (D)-a single 6.8 kW stack working at two fixed levels (2 kW or 4 kW) depending on the demand.