Study & design of binary ORC using wet cooling tower (existing) of unit V & VI in Lahendong geothermal field, Indonesia

Abstract

Utilization of hot brine from production separator has a great potential to generate electricity as a secondary turbine in Lahendong and the other PT PGE fields. Currently, the separated water from separator will move directly into reinjection wells with gravity due differential elevation of about 60 meters.
In order to utilize hot brine from production separator, the existing line should be modified by making pipe branch 6”schedule 40 toward secondary turbine, from main line 16” schedule 40. The pressurized water from upstream (7.83 barg) has a pressure drop 0.13 barg and heat loss 0.019°C along 30 meters of new pipeline.
In this study, pentane was chosen as the best selection of binary working fluids due to had power output greater than others and the surface condenser with pressure 1.32 bara is connected to the existing wet cooling tower as the cooling system. The calculation using Scilab and CoolProp as numerical computation, with vaporizer pressure 8.63 bara or 7.70 barg resulting net power 1795.32 kW and SSI value 2.02, while using vaporizer pressure 18.7 bara resulting net power 626.1 kW with SSI value 0.99.