Experimental evaluation of spectral energy balance in a semi-transparent photovoltaic module under outdoor conditions

Semi-transparent photovoltaic (STPV) modules facilitate concurrent electricity generation and light transmission, rendering them appealing for building-integrated photovoltaics (BIPV) and agrivoltaic applications. Experimental data on the partitioning of incident solar energy into absorbed, transmitted, and reflected components under actual outdoor conditions are still limited. The present study conducts an outdoor spectral energy balance analysis of a commercial glass-glass STPV module utilising directional spectrometer measurements. Spectral data were obtained for incident, transmitted, and reflected solar radiation across the ultraviolet, visible, and near-infrared wavelength ranges under clear-sky conditions. The findings indicate that, on an integrated energy basis, the module absorbs roughly 66.8% of incident solar radiation, with 18.6% transmitted and 14.6% reflected. The spectral distribution indicates significant absorption in the visible range (500–550 nm), accompanied by decreased transmittance and reflectance in the near-infrared region. The characteristics suggest a trade-off between energy harvesting and optical transparency, which is typical of commercial STPV systems. The measurements indicate directional spectral components instead of total hemispherical transmission and reflection. Consequently, the findings should be viewed as a case-study-level energy balance rather than a thorough optical characterisation. The dataset offers baseline experimental evidence of spectral energy partitioning in a commercially deployed STPV module, contributing to energy-oriented performance assessment for BIPV and agrivoltaic applications. • Experimental spectral energy balance of STPV under outdoor conditions. • Directional spectrometer-based measurement of spectral partitioning. • Quantification of absorption (66.8%), transmission (18.6%), reflection (14.6%). • Evidence of wavelength-selective behaviour in STPV modules. • Implications for BIPV and agrivoltaic applications.