Thermoeconomic analysis of a geothermal power plant by comparison of different exergetic methods

Abstract

Exergoeconomics is a vital complementation of thermodynamic performance analysis. In this study, a comprehensive exergoeconomic analysis of a binary geothermal power plant in southwestern Anatolia is conducted to determine improvement potentials in the plant configuration. By utilization of cost allocation rules of three different exergoeconomic methods (Moran, Specific Exergy Costing (SPECO), Exergy Cost Theory) plant is analyzed in terms of exergetic costs and possible optimization areas. Levelized cost of electricity (LCOE) estimated by 3 different methods vary within a 3.6% range, between 7.81 c$/kWh and 8.1 c$/kWh. It has also been determined that 51.5% of LCOE is constituted by waste/residual costs. Components especially including a thermal phase change or energy conversion, whose exergoeconomic factors below 0.5 warrant investment and optimization for performance improvement despite their higher individual exergetic efficiencies reported in previous studies. This phenomenon highlights the importance of considering exergetic efficiency and exergoeconomic factors together as plant design parameters. By using advanced materials or by optimizing the temperature gradient between the geothermal brine and the working fluid, heat transfer efficiency can be enhanced in heat exchanger devices. Turbines generally have mechanical losses which can be enhanced by optimizing blade design, reducing friction, and enhancing the thermodynamic cycle (i.e., use re-heat stages or improve steam conditions).