Dynamic exergy analysis - Modelica®-based tool development: A case study of CHP district heating in Bottrop, Germany

Exergy analysis is a powerful thermodynamic technique for assessing and optimizing the efficiency of energy systems. In this research, a Modelica®-based tool to perform a fully-dynamic exergy analysis has been developed. Another scope of this study is to develop a component that automatically generates a “Hydraulic network” in the Modelica® modelling language to be used as a case study for performing a dynamic exergy analysis. Using this component, a model of a district in Bottrop, Germany and its energy system has been developed. The exergy analysis tool has been implemented in this district model and the system has been dynamically analysed from an exergy point of view. Additionally, the “simple water model” of the Modelica® Standard Library has been improved in the course of this research to meet the requirements of an exergy analysis. Influence of key parameters variation has been investigated and the system has been optimized with respect to the overall exergy efficiency by means of a parameter study. Using this approach, an improvement of the overall exergy efficiency of 5 percentage points has been achieved.