Increasing land productivity with agriphotovoltaics: Application to an alfalfa field

Agriphotovoltaic systems, consisting of the combination of crops and photovoltaic panels (PVPs) on the same area, have recently emerged as an opportunity to solve the competition for land use between food and energy production. Various crops, pedoclimatic contexts and structures and both fixed and mobile panels have been studied. Over a period of two years, this research has been investigating an agriphotovoltaic (APV) system with mobile panels along two axes of rotation. The studied crop is alfalfa, a grassland species that has received little attention under these conditions. In our experimental set-up, the alfalfa biomass increased by an average of 10 % over the two years of the experiment in the shade of the APV plant (between 29 % − 44 %) in comparison to full sunlight (835 g.m−2.year−1), but in a different way depending on the climatic year. The nutritional qualities were preserved while the canopy's morphology was adapted through an increase in the length of the stems and the surface area of the leaflets. Photovoltaic production was reduced by 15 % due to the optimised tracking for plant growth. This combined production allowed an increase in total productivity per unit area of 51 % (LER: 1.51). The positive agronomic results are explained by a decrease in evapotranspiration caused by the panels in a context where the crop is highly sensitive to water deficit with thin soil. To reach a more general conclusion on synergy, these results need to be completed over several years and compared with other studies in different soil and climatic contexts, as well as with modelling studies.