Dynamic modelling and thermoeconomic analysis for the energy refurbishment of the Italian building sector: Case study for the "Superbonus 110 %?"funding strategy

The refurbishment of the building sector is a relevant issue in several Countries, such as Italy, where the poor energy performance of residential buildings dramatically affects the overall primary energy consumption and the related emissions of CO2. Such buildings are featured by a significantly poor efficiency of the conventional centralized boilers and by a scarce thermal insulation of the envelope. Therefore, the use of renewable technologies, as the solar ones, may significantly reduce the environmental impact of such residential buildings. Moreover, the use of modern and highly efficient boilers is crucial to reduce the primary energy consumption. The combination of these solutions along with the improvement of thermal insulation of the building envelope seems very promising to enhance the energy performance of existing residential buildings. In particular, this work proposes the integration of a CO2 heat pump to replace a conventional gas-fired boiler. This solution aims to be suitable for the Italian economic funding policy, known as "Superbonus 110% ", where some specific energy refurbishment actions are fully funded by the Government. In the layout presented in this paper, the existing radiators are supplied by a new CO2 heat pump, since its high outlet temperature is very close to the boiler one. Furthermore, the thermal insulation of the building envelope and the use of photovoltaic panels are also considered in combination with the CO2 heat pump. In this work, the dynamic, monthly, and annual results of the carried out dynamic simulations are then presented and discussed. The optimal solution of the proposed layout is detected by means of a detailed sensitivity analysis which considers different weather zones. The energy and environmental analyses show that the CO2 heat pump coupled with all the other solutions leads to a reduction of the primary energy consumption by 52% and a total CO2 emission savings of 49%. The Italian incentive is considered in the economic analysis and results show a Net Present Value of the investment of roughly 27 keuro, considering a lifespan of 25 years.