Abstract

District Heating Systems (DHS) are widely utilized for space heating in residential and commercial buildings. They offer economic benefits to consumers in terms of lower heating costs. The energy efficiency of DHS can be further improved by optimally controlling the operating parameters of the system. With this as a motivation, dynamic modeling and optimal operation strategies of DHS are explored in this thesis. Two typical District Heating Systems namely Direct District Heating System (DDHS) and Indirect District Heating System (IDHS) are considered. Using typical system configurations the components of the DHS were sized. Dynamic models of the designed DHSS useful for control analysis were developed. Open loop tests subject to constant inputs and loads were conducted to evaluate the time response characteristics of DHS. A methodology for computing optimal operating parameters of DHS is presented. These optimal parameters so computed are used as set points for PID controllers. The DHS by virtue of its long distribution network is subject to large transportation time delays. To compensate such time delays, a PID controller augmented with a Smith Predictor is developed. The designed controller is used to simulate closed loop operation of DHS under variable load conditions. Results show that the optimal set point strategy can save 10%-15% energy compared to conventional control strategies