EXERGY ANALYSIS OF SOUTHERN NEGROS GEOTHERMAL FIELD, PHILIPPINES

Abstract

Exergy analysis is important for identifying the sources of ineffeciency in a thermal process and for determining options for optimizing the system (Szargut et al., 1988). In a common geothermal power plant set-up, the overall second law (exergy/utilization) efficiency of the process is obtained from the actual electric power generated by the available exergetic power from the produced geothermal fluids at the wellheads.
This work calculates the second law efficiency of the geothermal system using exergetic power from the geothermal reservoir, instead of the wellhead. In Southern Negros Geothermal Project (SNGP), the utilization efficiency is 28.8 % based on an available exergy of 670 MWe at the reservoir. Reservoir parameters that are used for exergy analysis are obtained through numerical reservoir modeling. An optimization and sustainability assessment of the resource shows that highest utilization efficiency (geothermal heat source) is obtained at a 190 ºC reinjection temperature.