Massive integration of renewable heat in district heating (DH) networks is conditioned by reduction of its operative temperatures, which in turn depends on the temperature level of the individual substations (SST).
This study tackles the issue of temperature reduction in existing DH SSTs.
Focus is set on two case studies:
- CAD-SIG located in Geneva: 2nd generation (2G), urban DH system from the 1960’s, delivering 359 GWh/yr at 110°C/70°C (supply/return)
- CAD Le Marais-Rouge located in Les Ponts-de-Martel: 4th generation (4G), rural DH system from 2007, delivering 5.8 GWh/a at 80°C/40°C
After a comparative overview of both case studies, their individual substations are ranked in terms of their influence on the DH return temperature.
For the 2G system, monitoring of selected SSTs, combined with NTU analysis, allows to further tackle the issue of high DH return temperatures, and to identify if the problem lies on the secondary side (building and/or distribution system) or on the DH heat exchanger.
For the 4G system, a specific monitoring campaign allows to characterize advantages of cascade preparation of domestic hot water and space heating. It is complemented by a numerical sensitivity analysis under diverse conditions of operation.
