| Abstract |
Darajat Unit 2 and Unit 3 are geothermal power plants operated by Star Energy Geothermal Darajat II, Limited (SEGD) located in Garut, West Java, Indonesia. These power plants produce electricity 95 MW and 121 MW during full load and 90 MW and 116 MW during Take or Pay (TOP). TOP is a minimum generation accepted by PLN based on Energy Sales Contract. To generate electricity, power plant requires the production of geothermal steam supplied from subsurface resources. Unit 2 and Unit 3 turbines require steam production of 368.15 kg/s during full load and 351.1 kg/s during TOP and upstream steam pressure at 17.9 barg. With a typical steam decline rate and the current upstream steam pressure around 17.9 barg, Darajat steam supply is calculated to fall in to a deficit situation around Q1/Q2 2018 (using full load scheme) or the end of December 2018 (using TOP scheme). Considering this steam supply calculation and potential deficit consequence, steam production optimization is required to maintain maximum electricity generation. In order to resolve the problem above, Lean Sigma project team was formed to execute the steam production optimization. The Lean Sigma is a method that relies on a collaborative team effort to improve performance by systematically removing waste and reducing variation adopted by SEGD. The project is divided into DMAIC phase (Define, Measure, Analyze, Improve and Control) process. Define (D) phase determines what are the inputs, processes, specifications and targets. Measure (M) phase selects and observes critical parameters and record as base line data. Analyze (A) phase conducts process analysis using the Lean Sigma tools and identify all aspects and choose the most important parameters that will be focused on. Improve (I) phase carries the some test to prove the hypothesis and make a Standard Operating Procedure (SOP) for implementation. The last step is Control (C) phase, it is to control the steps that have been implemented during the improvement phase. As the result of this project, Unit-2 and Unit-3 upstream pressure can be optimized by reducing the pressure from 17.9 to 17.39 barg as an average with a duration of five months. Upstream optimization of Unit 2 and Unit 3 can extend steam shortages until the end of August 2018 (using full load scheme) or end of April 2019 (using TOP scheme). This steam production optimization project contributes potential cost savings USD 2,624,620 to company. |