Developing and exergetic performance assessment of biogas upgrading process driven by flat plate solar collectors coupled with Kalina power cycle

Highlights: • Biogas upgrading was integrated with FPC & Kalina cycle and exergetically assessed. • The analysis was based on the real solar data for Bushehr city. • Sensitivity analysis of the integrated system was conducted. • The proposed system was able to produce upgraded biogas with a rate of 2293 kg/h. • Exergy efficiency of cycle was 92.36% & FPCs had the highest exergy destruction. -- Abstract: The goal of this study is to develop and introduce a novel integrated system composed of water scrubbing biogas upgrading process with water regeneration, flat plate solar collectors (FPC) and Kalina power cycle. Solar thermal energy was exploited by means of FPCs and delivered to the Kalina cycle aiming at producing the electrical power required by biogas upgrading process. The excess heat in biogas upgrading cycle was recovered and fed to the Kalina cycle. The proposed system was simulated by Aspen Hysys based on the real solar data for Bushehr city. Overall, the FPCs provided 2627 kW thermal power to the Kalina cycle, where 289.5 kW electrical power was produced and delivered to the biogas upgrading process. The water scrubbing process was capable of removing the CO₂ and H₂S contents and provided upgraded biogas with a mass flow of 2293 kg h⁻¹. A comprehensive second law based thermodynamic analysis was accomplished to assess the effectiveness of the proposed cycle and the exergetic performance of the components was scrutinized and discussed thoroughly. The exergy efficiency of the proposed integrated system was found 92.36%. The highest exergy destruction was occurred in the FPCs being responsible for 73% of the whole exergy destruction. The desorption column and steam turbine had the second and third highest exergy destruction, respectively. The effects of collector's number and minimum approach temperature on the exergy efficiency, upgraded biogas production, Kalina cycle efficiency, and exergy destruction were studied and discussed as well.