Design and Performance Comparison of District Heating Systems in Milan and Riga

The work proposes a comparison between three heating configurations covering the demand of a new settlement: 1) centralized district heating system (DHC); 2) 5th generation district heating & cooling system (5GDHC) and 3) individual home heating and cooling (HHC) systems. Thermal and electrical loads are evaluated by transient simulations of a residential area with 80 buildings. The energy plants are based on different technologies: combined heat and power plants, gas-fired boilers, and domestic heat pumps. A transient numerical model has been developed for each solution. Every component is modelled according to performance maps provided by the manufacturers, allowing an accurate simulation in both design and off-design operating conditions. On an annual basis, the Latvian residential complex requires almost twice as much energy as the Milan one. The thermal losses in the district systems are 4.21 % in the Milan solution and 5.65 % in Riga. The district heating system coupled with a heat pump represents the best layout in terms of primary energy consumption in both locations, with energy savings of 50 % compared to other solutions. The use of 5GDHC is a good compromise that could increase the use of renewable energy. The adoption of a cogeneration plant is a good choice in the case of a centralized district system that allows the installation of high-efficiency genset. On the contrary, for small applications such as residential, the cogeneration results are expensive, and the conversion efficiency does not justify the installation.