Architectural integration of photovoltaics in high-rise office buildings: a case study in Milan

The paper illustrates the potential use of PV Glass as a solution for building purposes, as well as an electricity-generating opportunity with the aim of capturing the sunlight for electricity production, focusing on high-rise office towers. In this regard, the use of Building Integrated PhotoVoltaics (BIPV) in the building envelope is very varied and opens many strategies for designers and architects. The concept of BIPV refers to an architectural technology and to the capability of photovoltaic systems to be multifunctional and interact with the building, producing free energy from a renewable source. The PV glass panels consist of layers of heat-treated safety glass (laminated with polymeric interlayer foils), which include in the middle a certain number of PV cells (monocrystalline, polycrystalline or amorphous). The cells are linked together following electric schemes based on technology of various bus bars connection and plugs (current state of art with 3 or 5 bus bars). BIPV glass provides the same performance (thermal and sound insulation) as a conventional glass and it can be assembled in Double Glazing Unit (DGU) or Triple Glazing Unit (TGU). Furthermore, PV systems can also be used as small stand-alone power units. Thus, the BIPV could be inserted in tailored solutions of new glass façades or replacing old glazings into retrofitting of curtain walls of buildings, generating free clean electricity and reducing the carbon footprint. In case of high-rise office buildings, BIPV technology may come to significant values of installed electrical power, but it is necessary to develop a consistent design strategy to take into account the daily and seasonal sun path and its positive input on available glazing area. Also shading given by adjacent buildings and sloping or recessed façade areas need to be clearly investigated as potential and crucial critical issues for the BIPV efficiency. The paper presents a significant case study of a high-rise office building in Milan (Italy), highlighting the “pros” and “cons” of PV integration in the building curtain walls for this specific building typology