Evaluating Vertical Building Integrated Photovoltaics With Standard and New Performance Metrics

Abstract Building energy resilience is emerging as a critical issue, driven by rising global energy demands and the increasing frequency of extreme weather events that disrupt power grids. Building-integrated photovoltaics (BIPVs) offer a means of harvesting on-site solar energy, but lack standard, user-friendly metrics to evaluate performance. This article investigates established metrics and introduces new ones for assessing vertical BIPV systems. A newly proposed metric, the energy production ratio (Er), compares seasonal and annual energy production of vertical BIPVs to those of south-facing photovoltaics (PVs) tilted at the optimal angle in the same location. South-facing vertical BIPV had the highest annual Er, with up to a 3% advantage over optimally tilted PVs in winter. Predictive Er equations based on latitude and orientation (south, east, and west) are introduced to help researchers and solar developers understand the potential of vertical BIPV technologies at specific geographical locations. Specific yield and performance ratio, standard metrics in the solar industry, are presented to evaluate the system capability relative to standard testing conditions. Additionally, a payback period scaling factor (SPBP) is introduced to rapidly estimate economic viability. South-facing vertical BIPV exhibited the lowest SPBP, with a 20% decrease compared to east- and west-oriented vertical BIPV, helping offset procurement costs. By applying these metrics across 33 diverse regions in the United States, this study highlights how geographical location influences the energy output and performance, offering clearer insights into the potential and cost-effectiveness of vertical BIPV systems. These insights could drive broader adoption and integration of photovoltaics into the built environment.