Energy, exergy, and economic evaluations of a CCHP system by using the internal combustion engines and gas turbine as prime movers

In this paper, a combined cooling, heating and power (CCHP) system has been designed under an electric charge supply strategy for a residential complex in Iran. The aim of this research is energy, exergy and economic analyses of the CCHP system with using different prime mover arrangements and presenting appropriate condition of its operation according to these viewpoints. For this purpose, three types of gas engine, diesel engine, and gas turbine as prime movers have been presented and analyzed separately and simultaneously at six different scenarios and the appropriate scenario has been proposed for the CCHP system. In addition, the performance of system has been estimated at various part load conditions. The system is modeled and simulated using thermodynamic and economic relationships by using a computer code in the MATLAB software. The results show that the CCHP system under the electricity supply strategy with the simultaneous combination of two prime movers has significant advantages over one of them. The CCHP efficiency with two prime movers increases up to 10% compared to that of a single prime mover as well as the exergy efficiency. Additionally, scenario 4 by combining the gas engine and diesel engine is selected as the best scenario. It has 87% energy efficiency, 62.8% exergy efficiency, and operating cost reduction of about 80%. Also, the payback period is 6.3 years by taking interest rate into account and 1.36 years regardless of it.