Construction and Operation of Kamojang Unit-4, the First Commercial Geothermal Power Plant Built, Owned and Operated by PT Pertamina Geothermal Energy

Abstract

PT Pertamina Geothermal Energy (PGE) is established in December 19, 2006 to deal with geothermal business in Indonesia. It carried on the role of PT Pertamina, a state-owned oil and gas company, in developing the geothermal energy in this country, starting in 1976, then succeeded in supplying steam to the first commercial geothermal power plant (30 MW.) namely Kamojang Unit 1 in 1983. It was followed by Unit 2 and Unit 3, 55 MW capacities each, commissioned in 1987. These 140 MW total capacity power plants are owned and operated by Indonesia Power, a subsidiary company of PT PLN the state-owned electricity company. Since then, PT Pertamina is recognized as an upstream player in geothermal energy development, to be precise: a steam seller geothermal company. It was ended in early 2008 when PGE successfully commissioned a Geothermal Power Plant (GPP) namely Kamojang Unit 4. This 63 MW installed capacity geothermal power plant is the first large-scale geothermal power plant built, owned and operated by PGE, and will be a starting point to install and operate a total of 500 MW geothermal power plants in the next 3 years.
The geothermal power plant had a starting commercial operation date (COD) on January 26, 2008, following a successful commissioning conducted at the end of the 2 year construction period. The basis of design is to acquire a lowest cost for every kW (net) installed capacity by conducting an optimization study of the circulating water system. The zero venting principle is applied to eliminate the steam loss through the rock muffler during normal operation. The geothermal power plant consumes about 423 ton/hr of steam which originated from 8 production wells to produce 60.5 MW (net) of electrical power. Initially, only 7 wells are used to supply steam to the geothermal power plant, however due to decline in steam production, one additional well was put in on June 2008. On the other hand, Non Condensable Gas (NCG) content in steam declined from 1.9% to 0.85% wt which allows operating only one Vacuum Pump. Despite problems that occurred during the first year operation, the geothermal power plant was able to dispatch 471 GWh of electricity to the National Grid, equivalent to a capacity factor of 95.78%.