Assessment of new functional units for agrivoltaic systems.

In agrivoltaic systems, photovoltaic (PV) modules are ground-mounted between crops replacing a part of greenhouse or are set below or above the cover film of greenhouse; these can provide solutions with respect to land competition and climate change mitigation. These systems have certain additional functions, namely, sunlight sharing, land sharing and power generation, as compared to the conventional agricultural production systems. These new functions are not adequately performed by traditionally used functional units (FUs), such as the mass- or the area-based FU, in agricultural life cycle assessment (LCA). Therefore, this study proposed new FUs for agrivoltaic systems, namely the modified area-based FU and the monetary-based FU. The modified area-based FU was derived by adding area covered by PV modules to the cultivated area addressing the function of land sharing. The monetary-based FU was derived by adding the prices of crops and electricity addressing the function of the system as a producer of differently valued market goods. The traditional area-based FU is based on the function of solar sharing because crop cultivation and power generation share the same sunlight falling on the same land. These new and traditional FUs were applied to a tomato greenhouse, with and without organic photovoltaics, as a case study of Japan. A combination of traditional and new FUs helps to maintain focus on crop production as the primary function of agricultural land and to better understand the environmental impacts of agrivoltaic systems. Finally, as the sharing of sunlight and land happen simultaneously, a method that addresses both these functions while reporting LCA results was considered.