An optimization approach to photovoltaic building integration towards low energy buildings in different climate zones

• Optimal PV building integration depends on climate zones. • Semi-transparent PVs eliminate overheating and boost flexibility index in hot climates. • PV shadings optimize environmental and energy indicators in moderate climates. • Opaque BIPV is more attractive for utilizing on-site PV generation in cold climates. Building integrated photovoltaic systems (BIPVs) focusing on windows, such as semi-transparent photovoltaic (STPV) or PV shading devices (PVSD), are proposed as efficient approaches to the production of electricity and the improvement of building energy performance. However, glass replacement with advanced PV concepts needs thorough energy and environmental assessment, since it took more than a millennium to produce transparent window glass of high visibility. Despite the many published studies in relation to the performance of each technology, there are limited comparative investigations of the proposed PV integration options and the most appropriate integration solutions for different climatic regions. Here, we report, for the first time, on the energy performance of four BIPVs that control solar radiation through windows and their effect on the built environment for three different climatic zones. The evaluation was done through TRNSYS simulations and calculation of representative indexes associated with thermal and visual comfort. A BIPV-flexibility index, given as a ratio of self-sufficiency to self-consumption, is proposed as a figure of merit for the assessment of each BIPV technology’s electricity production and its effect on building energy performance. The findings clearly show that BIPVs could substantially contribute to the transition to zero energy buildings due to their passive energy benefits (up to 43% savings) in addition to their electricity production. Opaque module, PV shadings and PV windows optimize the BIPV-flexibility index (up to 0.57) for cold, moderate and hot climates, with acceptable indoor thermal (up to 54% of time) and visual (up to 83% of time) comfort.