Unlocking temperature reduction of cogeneration district heating networks through automated substation retrofit

To achieve decarbonization targets, the network operating temperatures of district heating networks need to be lowered to increase efficiency in heat generation and distribution. However, reducing operating temperatures in existing networks can present challenges with respect to the required heat and flow transfer through the substations and network pipes. These challenges should be alleviated to enable the desired temperature reduction and increased energy efficiency. To assist herein, an automated retrofitting methodology is introduced, which suggests the optimal retrofit for existing networks by leveraging mathematical optimization. The installation choice of a supplementary heat exchanger in the substations is optimized to enable network temperature reduction in a cost-optimal way. The proposed methodology is applied to a representative 3rd generation network in Belgium, where the suggested retrofits would allow an optimal temperature reduction from 100°C to 84°C and a cost reduction for the network operator of 24.6%. The paper highlights how the optimization-supported retrofitting methodology is able to simultaneously account for the different aspects influencing the retrofitting decision, such as the required consumer temperature and local retrofitting costs. Thereby, the paper emphasizes the advantage of using the proposed holistic and automated mathematical optimization approach, instead of rule-based approaches, to determine necessary network retrofits.