15 Feb 2022

Cascade sub-low temperature district heating networks in existing district heating systems

This paper discusses the integration of sub-LTDHNs into the return flow of existing HTDHNs, thereby creating an energy cascade and thus lowering the overall system temperatures of the HTDHN.

Existing district heating networks (DHNs) are often designed for relatively high temperatures, typically 80–120 °C supply and 40–60 °C return. The transformation of such high-temperature DHNs (HTDHNs) into more efficient low-temperature DHNs (LTDHN) and towards the 4th generation DHNs is associated with great complexity and effort. This paper discusses the integration of sub-LTDHNs into the return flow of existing HTDHNs, thereby creating an energy cascade and thus lowering the overall system temperatures of the HTDHN. The technical barriers and drivers of such sub-LTDHNs were analysed through literature research, expert interviews, and a questionnaire. Their technical design was investigated, and a techno-economic analysis was conducted for several configurations in terms of the supply and return temperatures in the sub-LTDHN, various temperatures of the HTDHN and potential connecting points.

Authors: A.Volkova (TalTech), S. Reuter (AIT), S.Puschnigg, H. Kauko, R.R. Schmidt (AIT), B. Leitner (AIT), S. Moser