Validation of a District Heating System Model and Simulation-Based Investigation of Bidirectional Heat Transport by Decentralized Solar Thermal Plants

摘要

This work discusses a MATLAB/Simulink-based modelling approach for the simulation of bidirectional flow in district heating systems with decentralized solar thermal plants. Based on the results of a monitoring campaign of an operational district heating network w ith decentralized solar thermal plants, a simulation model of the system is validated. Modified components for pipes, thermal storages and network junctions are derived from the CARNOT toolbox and additionally validated by laboratory tests. These components are used to enhance the model for the simulation of a reversed flow in the district heating pipes. Based on this modification, a study is conducted to examine the performance of a return-supply feed-in compared to a return-return feed-in for different dimensions of solar thermal plants in the network. The comparison shows that for small plant sizes and low solar fractions, a pure return-return feed-in can be suitable, whereas for higher solar fractions, a return-supply feed-in increases the solar yield of the decentralized plants.