Rice yield and energy balance in an agrivoltaic system established in Shonai plain, northern Japan

Abstract

An agrivoltaic system (AVS), wherein crops and electricity are simultaneously produced on the same agricultural land, contributes to renewable energy production and food security. AVS is expected to expand energy production in rural areas; however, its energy balance has not been comprehensively investigated. In this study, the energy balance of an AVS established in 2021 in the paddy fields on Shonai Plain was determined. The factors affecting rice growth and yield and the amount of electricity generated were monitored for 3 years (2021-2023). The photosynthetic photon flux density (PPFD) in the AVS field decreased by 26-39 %. Rice growth and yield decreased by >20 % due to insufficient light, as the photovoltaic (PV) panels intercepted most of the solar radiation. The energy balance of the AVS was -3102.47 GJ·ha^-1 because energy input was required for installing the AVS. However, since 2083.46 GJ· ha^-1 of energy was generated by the AVS, it is expected that the energy balance will become positive after >2 years of operation. To improve rice production, it is necessary to model PPFD and rice growth; additionally, PV panels should be movable so that the amount of PPFD can be adjusted depending on the model.

Keywords: Green energy; Land use; Paddy field; Photosynthetic photon flux density; Photovoltaic panels.