The first geothermal binary system in Indonesia that has successfully implemented is a 500kW binary system in Lahendong. Yet, there is still a plenty room of improvement for binary system development in Lahendong. This study aims to give an alternative design of the binary system by using an organic Rankine cycle. The investigations of thermodynamic analysis based on the law of thermodynamics, silica scaling analysis, and optimization of working fluid selection are presented. Flashing process from separator produces vapor and liquid-brine with mass flow rates 48.6 kg/s and 173.6 kg/s at separator pressure of 10.23 bar. Based on second law thermodynamics analysis, obtained the maximum useful energy from brine flow is 7.2MW. Based on the simulation results, it is achieved that the potential power generated by waste heat from the Lahendong plant is 2.46MW with the net thermal and exergy efficiency by 11% and 34%, respectively. Compared to the current operating binary system, still, much available energy needs to be harnessed in the future from the Lahendong plant.

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This study aims to design and conduct an experimental study of axle tilt angles variation on the performance of the Archimedes screw turbine (AST). The AST was constructed based on Rorres (2000) [3] formulation to achieve the optimum design of AST. This design was obtained with the followings parameters:  1.7m turbine axle length, 0.069m and 0.128m of internal and external turbine radius, 0.260m pitch length, 6.5 pitches number, 59° and 72° of external and internal blade angel, and 2 number of blades. The screw turbine performance was experimentally carried out by varying the angle of the turbine axle in the range of 25°, 30°, 35°, 40°, and 45°. The test was utilized the natural river flow with an average discharge of 0.011 m3/s. The result was yielded that the optimum angle of the turbine was at a turbine tilt axle of 35° while the rotational speed was 265.5 rpm, whereby the turbine generated  48.81W power and 4.09Nm of torque. This study is hopefully beneficial for the turbine design reference as well as its experimental evaluation.

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This study investigated the optimum value of Archimedes Screw Turbine (AST) performance by taking into account blades number. This paper also addressed the design approach based on a fixed incline angle of 30°, where this paper also addressed the design approach. Variations of the single and double blades were experimentally carried out concerning the turbine power output, torque, and rotation speed. This study's aim was related to the optimum power output between two blade variations, while the manufacturing and design steps were addressed as well. In the design process, the obtained blade length dimension was 0.180 m and 0.269 m for the single and double blades. Furthermore, the overall turbine's length was 1.7m, and the inner and outer of the turbine's radius were 0.069m and 0.128m. Meanwhile, the manufacturing process began with turbine modeling, plate cutting, plate withdrawal (thread formation), welding, and attained finishing process. Based on the experimental result, a double blade turbine generated turbine power by 48.8W at an average rotational speed of 115.3 rpm. Moreover, a single blade turbine produced 37.5W with turbine power averaging a rotational speed of 109.8 rpm. It was obtained that the values of turbine efficiency were 42% and 38% for double and single turbine types, respectively. Based on this finding, it can be suggested that a double blade was more efficient than a single one. This study is beneficial for the design consideration of the AST system.