Development of building driven-energy payback time for energy transition of building with renewable energy systems

Indicators capable of reflecting the life cycle energy consumption and generation for both the building and renewable energy system are necessary to quantitatively evaluate substantive energy transition of the building since most of research or policies only focused on the operation energy of the building. In this regard, this study applied the energy payback time to the building installed with the renewable energy system, and proposed “building driven-energy payback time (BD-EPBT).” To evaluate the BD-EPBT of the building, a building applied with South Korea's energy transition policy was decided as a case study. With the annual energy generation (19.2 million kWh/yr) based on the current policy, the BD-EPBT was calculated at 53.9 years, which exceeded the building's lifetime (40 years), and the actual energy transition ratio was 22.2%, far less than the national objective (30%). In addition, the annual energy generation required to achieve a 30% energy transition target within the building's lifetime was estimated as 26.4 million kWh/yr, which is more than 137% of the current policy-based annual energy generation. Consequently, the energy transition of the building sector cannot be achieved by the current policies. Therefore, the BD-EPBT should be introduced for the substantial energy transition of the building with the renewable energy systems. This reduces the life cycle energy consumption of buildings and renewable energy systems and helps to effectively install the renewable energy systems.