The organic rankine cycle (ORC) is a heat recovery technology used for renewable energy generation such as the large-scale production of electricity from geothermal resources. In this paper a dynamic model of a commercial-scale geothermal ORC is developed in process simulation software and validated against plant data. The difference in power output between the model and plant was found to be 0.24% with a standard deviation of 1.40% of the average power output. The results from model validation are used to suggest improvements to the model, which is intended to be used for further investigation of optimisation and process control. (C) 2016 Elsevier Ltd. All rights reserved.