Thermodynamic, economic and environmental assessments in a cogeneration power plant

Exergoeconomic assessment with Specific Exergy Costing (SPECO) technique and an exergoenvironmental analysis for a cogeneration system have been implemented to show the relation among thermodynamics and economical data and environmental impact of each component on the system. Depending upon the outcomes of exergoeconomic analysis, the unitary exergy price and exergy price of the natural gas have been counted as 0.05 US$/GJ and 490.23 US$/h, respectively. The unitary exergetic price and exergetic price of the steam have been counted as 158.84 US$/GJ and 2958.17 US$/h, respectively. Furthermore, the capital investment price, operating and maintenance price, and total price of the cogeneration system have been calculated to be 2185.50, 2316.60, and 4502.08 US$ per hour, respectively. The unitary environmental impact rate and environmental impact rate of the electricity, which is produced in the turbine, have been reckoned as 0.22 mPts/GJ and 0.02 mPts/h, respectively. Moreover, the effects of various fuel loading conditions and steam pressures (from 4 bar to 12 bar) on exergy prices have been investigated. The amount of fuel loading decreases, the exergy price of fuel, steam, and electricity also decreases. As the steam pressure goes up, the price of exergy loss for the boiler goes up whilst the exergy price of steam decreases.