Technical, economic and environmental optimization of district heating expansion in an urban agglomeration

In order to integrate large shares of variable renewable energy sources, district heating can play an important role. Furthermore, in order to increase the efficiency of district heating systems, interconnecting adjacent system could be socio-economically justified. In order to assess the economic and environmental consequences of the latter, a mixed linear integer optimization model was developed with the endogenous decision on the potential interconnectors.

The case study was carried out for the city of Zagreb, Croatia. The results showed that all three studied interconnections are economically viable, while the socio-economic cost was 29.2% lower in the case of the implemented interconnectors, all other capacities being equal. Moreover, the optimal thermal energy storage capacity was found to be equal to 25 and 24 days of average heating demand in two alternative scenarios.

Finally, compared to the reference case, the CO2 emissions could be lowered by 15.3%.CO2 savings derive mainly from better utilization of low carbon capacities after interconnecting the systems, as well as from installation of heat pumps and electric boilers.