Preliminary Exergy Analysis for Performance Optimization at Ulubelu Geothermal Power Plant Unit 1

Abstract

Indonesia lies within the Ring of Fire, renowned for volcanic activity and geothermal energy potential estimated at 23.7 GW. By 2023, 18 geothermal power plants were operational with a combined capacity of 2,597 MW. The Ulubelu Geothermal Power Plant, supplying 25% of Lampung’s electricity, serves as a case study for a preliminary exergy analysis. Using Cycle-Tempo simulation, a thermodynamic model was developed to replicate actual operating conditions and evaluate exergy flows and losses. The system’s total exergy input was 50,136 kW, with 16,367 kW (32.6%) destroyed due to irreversibilities, resulting in an overall exergy efficiency of 67.34%. The turbine achieved the highest functional exergy efficiency (82.43%) but also accounted for the largest relative exergy loss (12.43%). Substantial inefficiencies were identified in the condenser (14.88%) and ejector (1.66%). These findings reveal critical sources of exergy destruction, forming the basis for targeted performance improvements. Optimization strategies are prioritized for the turbine and condenser, where losses are most significant.