Selection of Optimum Working Fluid and Cycle Configuration of Organic Rankine Cycle (ORC) as Bottoming Binary Cycle at Wayang Windu Geothermal Power Plant

Abstract

This research presents the thermo-economic approach for determining the optimal setting of Organic Rankine Cycle (ORC) as the proposed bottoming binary cycle for the existing Wayang Windu geothermal power plant. The ratio of the total heat transfer area to net power output (γ) and the ratio of the total specific equipment investment costs to net power output (SICp) are selected as the optimisation parameters. The working fluids and cycle configurations are varied in the optimisation process. Three working fluids are selected: isopentane, isobutane, and n-pentane. Two-cycle configurations are compared: basic ORC and recuperative ORC system. Each model is assessed on its thermodynamic performance (thermal efficiency and net power output) and economic performance (levelized cost of energy and discounted payback period). Aspen Hysys v 10 is employed to gather the technical and economic data of the various ORC settings. Further calculations are conducted to analyse the simulation data. The results show that n-pentane provides the highest net power output as well as the lowest specific investment cost for the Wayang Windu brine characteristic. The results also indicate that it is economically more beneficial to operate under the basic ORC system configuration rather than the recuperative ORC system.