TECNO-ECONOMIC STUDY OF ORGANIC RANKINE CYCLE DEVELOPMENT SCENARIO AT ULUMBU GEOTHERMAL POWER PLANT BACK PRESSURE TURBINE UNIT

• Main Author: Nandaliarasyad, Naufal
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/43125
• Institution: Institut Teknologi Bandung

Binary cycle using organic working fluid or ORC system has been applied in geothermal and some other industrial processes to recover low grade and waste energy to generate electricity. The conventional system to utilize geothermal energy is a condensing system or back pressure system which depend on a turbine used in the system. Two units of the Ulumbu Geothermal Power Plant are using back pressure turbine, which means that there is still a chance to increase the electrical power of the steam which is released through the turbine. The amount of exhaust steam available from these two units power plant is more than 62,000 kg per hour with 99oC of temperature and around 2,430 kJ/kg enthalpy. This research is trying to get the optimum power that can be generated by the ORC regarding other consideration parameters such as ambient temperature, thermodynamics condition of resource steam, and energy conversion of each apparatus. The aim of this paper is to present a thermodynamic study on the utilization of ORC as the bottoming cycle with various types of working fluids to produce additional electricity. Several working fluids are chosen to find the optimum ORC scenario to utilize this exhaust steam such as isobutane, butane, isobutene, isopentane, propane, propyne, neopentane, R245fa, R236fa, and R134a. ORC system used in this research is simple ORC with basic components such as Pre-Heater, Evaporator, Expander, Condenser, and Pump. The properties of working fluids are calculated by REFPROP. The type of working fluid must also be considered, whether it was wet, isentropic, or dry type working fluid. The best scenario for this ORC is using isopentane as the working fluid. It can generate up to 2 MW with 10.29% thermal efficiency. The development cost for this scenario reaches 2,496.6 USD and is able to produce an IRR value of 16.5% with an NPV of 127.797,70 USD if the electricity is sold at 0.16 USD / kWh.