Monitoring and aggregate modelling of an existing neutral temperature district heating network

Abstract

This contribution provides preliminary modelling results and data analysis of an existing neutral-temperature district heating (NTDH) network. The word ”neutral” in this context refers to the fact that the distribution temperature is close to the ambient temperature (e.g., 15–20 °C). This type of network is coupled with decentralized heat pumps (HP), for both heating and cooling. They offer the advantage of being reversible and the possibility of integrating low-temperature waste heat. The considered case is located in Ospitaletto, Italy. The network includes two sources (industrial waste heat at about 25 °C and ground source heat from aquifer wells at about 15 °C), it is mainly built with non-insulated pipes and has a length of approximately 2 km. Decentralized HPs installed at user substations provide the proper temperature for space heating and sanitary hot water production.An approximate model was applied to analyse the network operation. This model is focused on energy balances aggregating all users as a lumped demand and explicitly includes the behaviour of HPs substations, a component not available in other district heating analysis tools. The simulation of an entire year of operation is considered, with an hourly resolution. Thermal load profiles are known and used as input to the model, while the outputs are compared with real data -a combination of weekly and hourly measurements at the users substations-which include annual heat supply, electricity consumptions, thermal losses, and seasonal performance factor (SPF). The results yield an overall deviation of 15% in the main indicators when using pre-defined data. In conclusion, even though the measured SPF is slightly lower than expected, the model reaches a reasonable agreement.