Energy scenarios for the decarbonisation of the building stock in the context of the energy system transformation

Decarbonising the building stock relies on the strategies of efficiency, sufficiency and consistency. Building stock energy scenarios (BSES) help evaluate the effect of these measures by modelling the existing building stock and using appropriate inputs, but must also account for boundary conditions, such as the structure of the energy system. In renewable energy (RE)-based systems, high summer generation contrasts with winter building stock demand, creating a seasonal gap. This study presents two BSES for Austria: a BAU scenario with standard decarbonisation measures (HVAC change and renovation rates) and a BEST scenario with more ambitious rates. Three energy system configurations are considered: (A) a demand-independent energy system based on current data of the Austrian electricity generation, (B) a RE-based generation system in terms of net-annual balance with the energy demand but connected with surrounding countries, and (C) an autarkic RE-based system with seasonal storage (based on green hydrogen). The key performance indicators (KPIs) used to assess the decarbonisation of a system are the equivalent CO 2 emissions, the load cover factor (LCF) and the required PV generation to reach energy autarky. The results show that the assumption of the energy system structure has a strong impact on the effectiveness of different measures. Hence, the choice of the KPIs is sensitive with respect to the boundary conditions. A building stock within a RE-based domestic energy system relying on energy imports to cover the winter gap cannot be considered fully decarbonised, if the import electricity mix is not known. On the other hand, an autarkic system is not feasible if the domestic demand exceeds the RE potential. The RE mix of the generation system, along with the load characteristics, has an impact on the winter gap magnitude, consequently influencing the energy imports or the seasonal storage requirements.