Optimisation of Ulubelu unit 1&2 PLTP electricity production realisation against cyclyc well using main setting pressure mode

Abstract

The Ulubelu Geothermal Power Plant, operated by PT Indonesia Power–PLN and PT Pertamina Geothermal Energy Tbk, plays a key role in Indonesia's renewable energy sector. Units 1 and 2 each have an installed capacity of 55 MW and rely on two-phase geothermal fluid from production wells such as UBL-56. However, UBL-56 exhibits cyclic pressure behavior, fluctuating between 6.14 barg and 11.27 barg, which affects the stability and availability of steam supply. As a result, Ulubelu Unit 1&2 often operate below their optimal capacity. To address this issue, the operational mode was shifted from Power Mode to Main Setting Pressure (MSP) Mode. MSP Mode prioritizes stable steam pressure delivery to the turbine, allowing for more efficient energy conversion during high-pressure phases. Implementation of MSP Mode resulted in a significant improvement, with an additional 44,329 kWh generated per day (~2% increase). This paper presents the methodology, operational adjustments, and results of this optimization, highlighting the potential of pressure-responsive strategies for enhancing electricity generation in geothermal systems with cyclic well behavior.