Technological and Economic Analysis on Modification of Turbine Shafts and Blades in Geothermal

The 55 MW geothermal power plant has been operating for 35 years. This generator experienced a reduction in turbine efficiency from 0.88 to 0.56. The decrease in turbine efficiency resulted in an increase in the volume of steam, a decrease in the power produced by the turbine, and instability in the generator's output power. The steam turbine consists of six levels: axial steam flow direction type, single flow type, with a rotation speed of 3000 rpm, inlet steam pressure of 6.50 bar, and exit steam pressure of 0.15 bar. The results of the shaft modification show an increase in performance, producing an internal efficiency of 0.66 and a relative efficiency of 0.73 when the turbine operates with a steam volume of 144.46 kg/s. This turbine is suitable for production and operation because it meets the economic feasibility requirements with a Net Present Value of IDR 243,816,146,409,928.00 and an Internal Rate of Return of 58%. The payback period for the investment capital is 1.72 years. This research focuses on developing a turbine by analyzing its technological and economic aspects. The modifications include changes to the shaft and blade components. The number of blades affects the rotational speed, torque coefficient, power coefficient, and turbine efficiency.