OPTIMIZATION OF GEOTHERMAL POWER PRODUCTION (CASE STUDY ULUMBU GEOTHERMAL POWER PRODUCTION UNIT 4 ULUMBU GEOTHERMAL WORKING AREA NTT, INDONESIA)

• Main Author: Ediatmaja, Prajamukti
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/48303
• Institution: Institut Teknologi Bandung

Ulumbu WKP is located in Manggarai Regency, East Nusa Tenggara Province, Indonesia is one of the WKP owned by PT PLN (Persero). In the Ulumbu WKP, there are four units of geothermal power plants with a capacity of 4 x 2.5 MW which have been operating since 2013. The steam used to operate all of the power plants in Ulumbu comes from ULB-2 production wells. Current conditions in Ulumbu unit 4, the scrubber pressure has decreased from 11 barg to 9.6 barg. Refers to the design conditions, scrubber pressure is equal to turbine inlet pressure. The pressure drop in scrubber makes the turbine being operated with inlet pressure conditions beyond its specifications. SSC during the commissioning of the Ulumbu unit 4 SSC was 9.77 T/MW. The increase of SSC after 6 years of operation becomes an average of 10.04 T/MW, makes opportunities for optimization performing. The optimization aims to reduce the SSC level so that Ulumbu unit 4 becomes more efficient. The optimization method is performed by analyzing the Ulumbu unit 4 thermodynamic equation model. Equation models are made in the EES software based on the Ulumbu design heat balance diagram. Validation of the equation model is performed by comparing the results of calculations in EES with the data on the heat balance diagram and the operating data. By using a validated equation model, optimization is done through simulation by changing several operating parameters. The simulation by changing the turbine inlet pressure to respond the pressure drop in the scrubber result in an optimal pressure at 9.3 barg with SSC value 9.17 T/MW and the cycle efficiency 10.39%. Optimization at the cooling tower air flow rate obtains SSC value 9.24 T/MW and the cycle efficiency 11.08%. While re-setting the NCG ejector compression ratio value can reduce the percentage of motive steam usage up to 9.8% of the total steam demand for unit 4. The cycle efficiency value for the overall optimization process is still below the standard efficiency of the dry steam geothermal power plant which is 16-17%. But in terms of SSC, the optimization simulation results lower SSC than the SSC test results during commissioning. If the optimization process in the Ulumbu unit 4 cooling system will be implemented, a VFD tool is needed to regulate the flow rate of air entering the cooling tower. The investment study carried out, the addition of VFD tools with a useful life of 10 years is feasible to do with an NPV of Rp. 714,493,000.00 and IRR value 103.09%