Spectrally selective c-Si agrivoltaic modules: Evaluating a new approach

Protected cropping is one of the most promising applications in the rapidly emerging field of agrivoltaics as it typically involves higher value crops that are shade tolerant and existing requirements for protective surface support structures offsets the cost of implementing the agrivoltaic array. To adapt photovoltaics (PV) for optimal use in protected cropping situations commercial semi-transparent PV modules are required. Detailed here for the first time is a novel design concept that embeds a Distributed Bragg Reflector (DBR) on flat plate concentrator geometry within a monolithic semi-transparent crystalline silicon (c-Si) PV module to provide spectral selectivity. It allows near-infrared (NIR) portions of the solar spectrum, not required by crops for photosynthesis, to be efficiently redirected to the c-Si cell matrix for electrical conversion while maintaining high transmission of photosynthetically active radiation to crops located below. To assess the expected performance benefit provided by the concept a simulation based study was undertaken and is reported on herein. A dedicated optical model based on raytracing is constructed to allow estimation of expected performance benefit across a year for typical panel orientations and site solar resources. For a semi-transparent module with PV cells covering 50% of the module area simulations indicate an increase of 23–27% in annual electrical output could be achieved via the inclusion of the embedded DBR. For semi-transparent modules with lower PV cell coverage larger improvements in electrical output could be achieved. When including the embedded DBR in a module with 38% cell coverage simulations indicated that an additional 34–40% in electrical output could be made available annually. For all semi-transparent modules investigated simulations indicate that over 90% of the original PAR transmission is maintained after incorporating the embedded DBR and crops could be shielded from approximately 80% of the NIR. The proposed concept is based on existing large area technologies and could likely be incorporated in semi-transparent modules for less than US$5.0/m 2 at commercial scale if requisite fabrication challenges are solved. To date, a commercially relevant spectrally selective PV module has yet to be demonstrated for use in agrivoltaic applications. The design concept detailed and assessed herein provides a commercially relevant approach that could significantly improve agrivoltaic system electrical output while maintaining appropriate levels of PAR transmission.