Effects of fuel composition on the economic performance of biogas-based power generation systems

Abstract

Biogas to fuel is an attractive method to reduce global warming potential of methane emission and providing a renewable source of energy. In this study, exergoeconomic assessment of a biogas-based gas turbine system with preheater is conducted. In the present work, effects of fuel composition on the exergetic and economic performance of a plant are studied, and comparison between two fuel pricing methods has been carried out. Fuel composition effects have not been studied before and fuel pricing mostly conducted in terms of lower heating value (LHV) in previous studies. In this study, percentage of methane content in the fuel is changed. Two definitions for fuel pricing are used, one based on the exergy and the other based on the LHV of the biogas and the results are compared. In addition, the cost factors are defined and the cost of generated power are evaluated. To add more generality to the work, system sizes ranged from 1 to 10 MW is taken into consideration to understand the effect of system size as well. Results reveal that fuel pricing based on the exergy gives more realistic evaluations. Furthermore, when methane content is changed from 0.95 to 0.6, total cost rate of the plant rises around 1% and electricity cost augments. Exergetic efficiency mitigates when methane content reduces. Based on the system size and biogas fuel price, the cost of generated electricity varies from 0.05$/kWh to 0.18$/kWh in this assessment.