Development of a Design Decision-Support Process for Photovoltaic System for Zero-Energy Building Certification and Operation

As zero-energy buildings (ZEBs) become increasingly mandatory, photovoltaic (PV) systems play a key role in increasing on-site energy generation. For staged ZEB certification based on the energy self-sufficiency ratio (ESSR), it is essential to determine the required power generation and to design PV systems with appropriate installation area and location. This study proposes a systematic design decision-support process for PV system planning that links required energy generation to panel installation strategies. The process enables the determination of a feasible installation area and location of PV panels and was implemented as a design-support program. The proposed process was applied to an apartment building under construction with a ZEB certification grade 5. Compared to the existing design, the optimal design reduced the required PV system capacity by 1.7% while increasing the predicted power generation by approximately 2.8%. The reported improvement in energy generation represents a relative comparison between design alternatives evaluated under identical modeling assumptions and therefore remains valid for comparative design decision-making. Field measurements conducted at a residential building with installed PV systems showed that the predicted power generation is consistent with measured trends, supporting comparative design evaluation and feasibility screening in early-stage PV planning. The developed design process provides a practical framework for early-stage PV system planning, supporting informed design decisions to meet target energy self-sufficiency requirements in ZEBs.