Thermo-economic analysis of PEM fuel cell fuelled with biomethane obtained from human waste by computer simulation

Abstract

Fuel cells, especially Proton Exchange Membrane (PEMFC) is considered as perfect alternative energy source that can either replace or complement existing energy source which is fossil fuel. However, the technology is still at developmental stage due to the lack of availability of fuel sources that is safe and economical. This study, therefore focused on thermo-economic analysis of PEMFC fuelled with biogas from human waste. To achieve the purpose of this study, thermoeconomic analysis was used to analyse PEMFC designed to generate 1.45 MW of electricity from domestic human waste. The stages involved are biogas generation, hydrogen production and fuel cell application. The processes were modelled using Aspen HYSYS V8.8, a software developed by Aspen Tech® . The Hydrogen was produced at a rate of 358 kgmole/h, temperature of 330 K, pressure of 4.8 bar and 99% purity from the Preferential oxidation (PrOx) exit stream. Data generated from the simulation model were subsequently used for the thermodynamic and economic analysis and a fuel processor efficiency of 83.5 % was obtained. Energy analysis of the process showed that the principle of energy conservation was satisfied, requiring and producing energy simultaneously and a net electrical efficiency of 42.32 % was realized, while the result of exergy analysis showed that the unit associated with high irreversibilities and maximum exergy destruction is the steam generator. From the economic analysis, a rate of return of 20% was realized which is an indication that the investment is safe and profitable. The general overview of the processes based on economic and thermodynamics performance shows that the investment is worthwhile and indeed waste can be turned to wealth.