A systems approach for stand -alone residential fuel cell power system design

Polymer Electrolyte Membrane Fuel Cells (PEMFCs) show great promise in portable, automotive, and stationary applications. PEMFCs have reached the test and demonstration phase in automotive and power markets today. Our research is focused on a stand-alone residential PEMFC power system that provides electricity needs of a residential house. A systems approach is introduced for both sizing of the overall fuel cell power system and for the design of power inverter.;Although the fuel cell stack itself will deliver the demanded power as long as the required flow rates are established, real fuel cell systems have delay characteristics to a transient condition due to mechanical components in the system. The required flows for an increase in power demand cannot be provided instantaneously. When the grid is not present, the details of the load profile would also be important in overall system sizing and must be taken into account. A stochastic sizing methodology is developed that considers both fuel cell system dynamics and residential load dynamics in overall system sizing for the stand-alone residential fuel cell power system.;Although due consideration is given to the fuel cell system characteristics such as low fuel cell voltage level and slow response of the fuel cell system in the design of power conditioning unit, no consideration is given to the demand characteristics for the power inverter design in stand-alone operations. Analysis of the measured daily load profile revealed that the load demand stays low most of the time during a day. Therefore, the power inverter, designed for peak power requirement, would be operating at light loads where its efficiency is lower. A new power inverter design that employs parallel switch combinations such as IGBT-IGBT and IGBT-MOSFET is proposed to improve light load efficiencies. It has been shown that when a MOSFET is used as a low power switch, the light load efficiency can be improved and considerable savings can be achieved for the stand-alone residential fuel cell power system.