A parametric study on exergoeconomic analysis for a binary geothermal power plant with ORC

Abstract

The exergoeconomic analysis of an energy conversion system is helpful to decide about topics like the cost of fuel required to produce each unit of energy, electricity sales prices affecting energy production cost amounts and how to allocate R&D funds to develop system equipment. With this aim, exergoeconomic assessment of a binary geothermal power plant (GPP) with organic Rankine cycle (ORC) is researched in detail. Therefore, a parametric study about the effect of well head and ambient temperatures, electricity production, and CO2 release is conducted for the GPP. The study shows that the exergy efficiency, exergy destruction ratio and exergoeconomic factor for the GPP are, respectively, 39.1%, 31.4%, and 58.1%. The highest total operating costs and exergy destruction rate belong to the condenser in the system with values of 186 $/h and 2.49 MW. The costs per unit exergy for the liquid and steam geothermal fluid in the GPP are 1.2 $/GJ and 370 $/GJ, respectively. The total operating cost of the GPP is nearly 1,218.38 $/h, while the cost rate per unit of electricity produced by the GPP is 0.055 $/kWh. As the ambient temperature increased, there is a 10% increase in total operating cost and this results in a 21% increase in cost per electricity produced. With the brine input temperatures of 160 degrees C, 165 degrees C, and 170 degrees C, the costs per unit CO2 output are, respectively, 110 $/h, 167.50 $/h, and 307 $/h. In conclusion, as the amount of steam brine entering the GPP increases, the amount of CO2 released to the atmosphere ascends.