A conceptual model of a high-efficiency, stand-alone power unit based on a fuel cell stack with an integrated auto-thermal ethanol reformer

An integrated configuration of a fuel cell and an auto-thermal ethanol reformer has been studied conceptually for high temperature (HT) and low temperature (LT) polymer electrolyte membrane fuel cells (PEMFCs) for a 5 kW, stand-alone power unit. It is found that the integrated reformer–HT fuel cell system can operate in an auto-thermal mode using a Co–Fe/Zn catalyst to reform aqueous ethanol at 500 °C to produce hydrogen with about 3% of CO which is tolerable for an HT-PEMFC operating at 200 °C. A simulation model developed for the integrated reformer–HT-PEMFC system shows that significant amount of excess heat is available at 700 °C. Using this excess heat, an integrated reformer–HT–LT-PEMFC power unit is designed which produces 15 kW of electrical power at an overall efficiency of 41% and a thermal efficiency of 80%. Since it has an integrated aqueous ethanol reformer, the fuel for the power unit can be stored in liquid form which makes it ideal for stand-alone power unit applications.