Lessons learned from excess flow analyses for various district heating systems

Abstract

In the transition to 4th Generation district heating, lower network temperatures are needed to allow easier integration of renewable energy sources into district heating networks. Many substations in existing district heating networks do not achieve optimal efficiency, which often corresponds to high return temperatures. This paper shows approaches to achieve significant improvements with only limited measurement data required. The excess flow analysis is used to rank substations according to their contribution to high return temperatures. It was applied for three existing district heating networks in Germany. In further steps substations were recommended for inspections and faults identified. Measures for fault elimination were suggested, and the possible return temperature reduction and costs of the measures estimated. For the network return temperature, a related reduction between 4 and 8 K was estimated. The costs per substation range from 0.08 to 7.91 €/(MWh∙K) for network return temperature reduction. Due to low temperature sensitivity most of these costs are too high for implementation with combined heat and power (CHP) plants, but the continuous integration of more temperature sensitive technologies such as heat pumps, solar thermal and geothermal energy offer economic feasibility for a higher quantity of measures.