Semitransparent photovoltaic (STPV) windows integratetransparent photovoltaic film technologies or spaced opaquesolar cells on the exterior glass layer. As these technologies aredeveloped and eventually adopted in the building and windowindustry, the evaluation of key performance parameters suchas the solar heat gain coefficient (SHGC), thermal conductance(U-factor), and electrical power output is required.These performance parameters are interdependent and theyhave a direct impact on the building cooling, heating, electriclighting loads, solar electricity generation, and occupancycomfort. Thus, STPV windows should be treated as integratedphotovoltaic and fenestration technologies.

This study focuses on the experimental determination ofthe SHGC of STPV windows under maximum power pointoperation, using an indoor solar simulator and calorimeterfacility. The objective of this work is to provide input on thedevelopment of an experimental procedure suited to the determinationof the SHGC of STPV windows. The results indicatethat when the solar electricity generation of the STPV windowis taken into account by operating the STPV windows at themaximum power point rather than open circuit conditions, theSHGC is reduced between 2% (for a STPV window with visibletransmittance of 40% and nominal conversion efficiency of7%) and 23% (for a STPV window with visible transmittanceof 6% and nominal conversion efficiency of 15%). The reductionis expected to be even higher in a STPV window with nolow-e coating due to significant increase of the inward-flowingabsorbed solar energy.