Abstract

First and second law analysis of a 12.9 MW binary geothermal power plant in Nevada is performed using actual plant data obtained in 1996, and alternatives are investigated to evaluate its performance. Exergy destruction throughout the plant is quantified and illustrated using an exergy cascade. The primary sites of exergy destructions are the turbine-generator assembly where power is generated, the condenser where the working fluid is condensed, and the reinjection well where the brine is reinjected into the ground after passing through heat exchangers. The exergy destruction at these sites account for 30.5%, 26.4%, and 21.4% of total exergy destruction in the plant, respectively.

The first and second law efficiencies of major plant components are determined in an attempt to assess their individual performances. The overall first and the second law efficiencies of the plant are calculated to be 5.6%, and 26.9%, respectively, based on the exergy of the geothermal fluid at reservoir, and 5.9%, and 29.2%, respectively, based on the exergy of the geothermal fluid at wellhead. Thermodynamic analysis of alternative designs (single and double flash systems) indicates that the existing binary design is best suited for this site, and thus it should be preferred at similar sites.

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