Effects of thin-film and wafer-based photovoltaic module transparency and spectral properties on microclimate and turnip yield in agrivoltaic systems

Agrivoltaics is a land efficient sustainable production system that simultaneously produces food and renewable electricity while reducing environmental harm. Agrivoltaic systems alter microclimates by modifying the quantity and quality of solar radiation reaching crops, yet limited research has examined these effects for root vegetables. This study investigates the influences of photovoltaic (PV) module type, transparency, and spectral properties on radiation transmission, photosynthetically active radiation, and turnip (rutabaga) yield. This is the first known study globally to investigate agrivoltaic production of turnips. Thirteen PV module treatments, including wafer-based crystalline silicon (c-Si) and thin-film cadmium telluride (CdTe) at multiple transparency levels, were tested under outdoor conditions. Results show that crop performance depended strongly on both the shading pattern and light spectrum. Thin-film CdTe modules, which provide uniform shading, optimized yield at 50–60% transparency, while c-Si modules with non-uniform shading patterns performed best at 8% transparency. In both cases, fresh turnip biomass increased up to threefold compared to full-sun controls, underscoring the role of moderated radiation and improved microclimate in alleviating heat and light stress. Spectral effects were also evident: modules enhancing blue light transmission promoted leaf biomass, whereas green-shifted spectra suppressed root development. Extrapolation to national scale suggests agrivoltaic adoption in Canada could generate CAD$33.93B in agricultural revenue and CAD$1.98B in solar electricity sales over 25 years, while reducing over one million tonnes of carbon emissions. This work highlights how PV transparency and spectral transmission fundamentally shape crop-atmosphere interactions in agrivoltaic systems, with implications for climate-resilient food production and dual land-use strategies.