Upgrading DH networks from the 60s and 70s
A recent project aimed to increase the share of renewable and cogenerated heat and reducing the local pollution by cleaner plants. Two levels of temperature are created to exploit heating in optimal way by different sources. The project has been validated by a dynamic optimization procedure integrated with the design.
Buildings in Alessandria are presently equipped with high temperature central heating systems running on gas or oil fired boilers. In the project, thermal power is provided by a mix of classical, cogeneration gas fired ICEs and backup boilers, and renewable heat coming from solar thermal field and ground source heat pumps connected to the local aquifer.
A 60 km piping extension covers the whole city while flexibility of operations is increased by a thermal storage of 2000 m3. As heat must be supplied to end-users at high temperature, a local low temperature grid is created where contributes from solar field and last cooling stage of CHPs are collected. This heat is upgraded at the high temperature value by heat pumps.
Challenges are mainly related to the operative coordination and tuning of the actual plant and its adherence to the nominal working conditions assumed in the Preliminary design phase. Even if the environmental indicators are positive and moving toward a lower carbon footprint of the plant, communication of the whole operation and social acceptance by end-users are issues to be continuously monitored.
Information on this page is retrieved from DHC+