Operation optimization of existing district heating systems

Reducing the operating cost of district heating (DH) systems can be regarded as an operation optimization of DH systems. It was proved that the pumping cost and heat loss cost (PHLC) determined the operating cost of an existing DH system. The minimum operating cost can be obtained by minimizing the PHLC. The optimization method was used. The optimization model used to minimize the PHLC of an existing DH system was established. Program was written to solve the optimization model by using MATLAB software. An existing indirect DH (IDH) system in Hohhot, Inner Mongolia, China was optimized by using the optimization model. Four strategies were used respectively. Results show that the minimum PHLC and related heating parameters can be obtained by using the optimization model. When controlling the primary water mass flow rate (PMF) and the secondary water mass flow rate (SMF) simultaneously, the minimum PHLC is lower than that for other strategies. But this operating strategy requires the excellent hydraulic stability of DH systems. The limit of the frequency of pumps should also be taken into account when applying the optimization model to engineering practice. (C) 2015 Elsevier Ltd. All rights reserved.