Dynamic Modelling and Simulation of an Organic Rankine Cycle Unit of a Geothermal Power Plant

Abstract

This article presents a dynamic model of a 5.4 MW binary cycle unit of a geothermal power plant. The plant is an Organic Rankine Cycle (ORC) where pentane is used as the motive fluid and it is powered by the separated brine from the geothermal fluid. It is found that the inlet brine properties including brine mass flow rate, and the ambient air temperature are the two most important parameters influencing the plant performance. Specifically, the plant performance is highly dependent on the ambient air temperature as the ORC uses air-cooled condenser. Moreover, the inlet brine property changes less significantly with respect to time compared to the ambient air temperature. Simulation has been carried out where, brine inlet properties and ambient air temperature are fed as inputs to the computer model. The simulated plant performance has been compared with the actual plant performance data. It has been found that the developed model is very competent in predicting plant performance. The average percentage error of the theoretical and the observed power outputs remain within 5%.