Performance analysis and economic assessment of a combined cooling heating and power (CCHP) system in wastewater treatment plants (WWTPs)

Wastewater treatment plants (WWTPs) have great potential as a renewable energy source because of producing biogas. Due to electrical, heating and cooling demands in WWTPs, combined cooling heating and power (CCHP) systems are an appropriate choice through the energy systems. In this study, a novel integrated WWTP-CCHP system is performed to investigate the system performance from energy and economic perspectives. The effect of various parameters on the performance, payback period and profitably index of the system are studied. To increase the system electrical efficiency, a combination of a micro gas turbine and an organic Rankine cycle (ORC) is utilized. The excess heat is used to provide thermal demand for an anaerobic digester. Due to declining digester thermal demand in the hot season, the residue of heat is employed for absorption chiller. Also, hot water is produced as a byproduct throughout the year. The CCHP system shows a lower energy efficiency and greater payback period and profitably index at high capacity of WWTP. The optimization of the system increases the electrical efficiency with a shorter PB and higher PI in all working conditions.