Dynamic temperature supply to boost the integration of renewable energy into existing district heating networks

The integration of renewable energy into District Heating systems is essential to achieving decarbonization targets by 2050. The transition to low-temperature renewable sources may be challenging in the case of large-scale systems originally designed for high-temperature fossil fuel plants. In this study, the implementation of a dynamic temperature supply strategy in portions of the network is proposed as a convenient solution to promote the integration of renewable energy and the transition to low temperature operation in existing networks. This objective is pursued through the installation of decentralized production units that use groundwater heat pumps and deliver hot water at lower temperature level than those of the central plant, which continues to operate just as a booster unit. The feasibility of the proposed operating conditions is evaluated by means of a physical model, which includes both the simulation of the network operation and a representation of the behavior of the different buildings. The application is tested on three sub-networks within a real large-scale system in Northern Italy. The results show that for more than 50 % of the operating time, the sub-networks can be supplied at temperatures between 40 °C and 90 °C using renewable energy, with the central fossil-fuel-based plant providing support only during the most demanding conditions.