Thermodynamic evaluation of a 5 kW kerosene-fueled PEMFC-based cogeneration system: Component-level and system-level analysis

Abstract

A 5 kW kerosene-fueled proton exchange membrane fuel cell-based cogeneration system consisting of a kerosene steam reforming reactor, pressure swing absorption, combustor, and heat collector is proposed for heating and power production. ASPEN Plus and MATLAB / Simulink jointed simulation models are used to establish an accurate model for the integrated system. Thermodynamic analysis in this study is classified into component-level analysis (parametric analysis) and system-level analysis (conventional and advanced exergy analysis). Parametric analysis reveals that increasing the H2 utilization ratio, improving the reformer pressure, and adding water separators contribute to the thermal efficiency of the integrated system. For example, as the H2 utilization ratio varies from 0.5 to 1.0, the thermal energy efficiency increases from 44.1 % to 47.4 % and the thermal exergy efficiency increases from 41.6 % to 44.7 %. Through system-level analysis, at a water/carbon ratio of 3.0, a reformer temperature of 750 °C, and an H2 utilization of 0.8, the thermal and exergy efficiencies of the system are 46.1 % and 43.4 %. Conventional exergy analysis indicates that fuel cell comprises 44.21 % of the total exergy destruction (9.315 kW), while advanced exergy analyses show that it has the highest avoidable-endogenous exergy destruction (3.567 kW). These exergy analyses suggest that fuel cell results in significant system exergy destruction and should be given priority for modification. Replacing a low-temperature fuel cell with a high-temperature fuel cell is a simple method to reduce the exergy destruction, reducing from 4.79 kW to 4.12 kW, approximately a 14 % reduction, and the exergy efficiency increases from 52.22 % to 55.95 %. The core of this work is to introduce a power and hydrogen generation system, evaluate its performance using an advanced thermodynamic method, and provide a solution to optimize the system.