A PERFORMANCE PREDICTION TOOL FOR ORC APPLICATIONS BASED ON MODELICA

asme-orc2015 Tracking Number 5

Converting industrial waste heat to electricity using organic ranking cycle (ORC) technology is an effective method to improve energy efficiency and reduce cost. However, the waste heat source is often characterized by relatively large fluctuations in load making it a demanding task to design and operate an ORC in an efficient and economically sound manner. Compounding this challenge are the relatively tight profit margins of ORC projects in general even with the support of governmental subsidies along with the tendency to use only a rough estimation in predicting performance. These factors increase the uncertainty when trying to create an economically successful operation. To build the business case on a firm foundation, performance prediction that takes into consideration all relevant operation aspects is inevitable. Therefore a reliable performance prediction tool for the use in an early project phase is highly desired and has been developed in this project. The performance prediction tool uses Modelica as the modeling platform and is comprised of the ThermoCycle library [1] in combination with the CoolProp software [2] necessary for calculating fluid properties. Whereas the ThermoCycle library provides robust and computationally efficient generic models for many ORC components, a newly developed library deals with the dynamic transient modeling of industrial plants in operation that contain an ORC. Specifically, two ORC applications in Switzerland have been investigated and used for parameterization and calibration: a large scale application in the cement industry and a small bio gas CHP application. The investigated plants show significant operating hours in the part load regime with many automatic shut-down and start-up cycles due to external limiting conditions such as high ambient temperatures or low engine output power. With the implemented transient models and the deduced control strategies, the measured ORC power output well predicts the industrial behavior over a longer period of time. This shows the approach to be a viable method to allow future performance prediction with a higher certainty. In addition, the dynamic models of the overall plants may be used to support future tasks necessary during the whole life cycle of an ORC plant (e.g. determining optimal control strategy concepts, pre-tuning of control parameters, troubleshooting during commissioning, planning service intervals etc.). Assessing additional ORC industrial applications will extend and boost the prediction capabilities of the tool, contributing to an ecological and efficient use of energy. [1] S. Quoilin, A. Desideri, J. Wronski, I. Bell, V. Lemort. ThermoCycle: A Modelica library for the simulation of thermodynamic systems, Proceedings of the 10th International Modelica Conference; March 10-12; 2014; Lund; Sweden [2] I. Bell, J. Wronski, S. Quoilin, and V. Lemort. Pure and Pseudo-pure Fluid Thermophysical Property Evaluation and the Open-Source Thermophysical Property Library CoolProp, Industrial & Engineering Chemistry Research 2014 53 (6), 2498-2508