Assessment of the Ground Coverage Ratio of AgriVoltaic systems as a proxy for potential crop productivity

Abstract

The yield of crops in both agrivoltaic (AV) and agroforestry (AF) systems is difficult to predict. The shade pattern of an AV system is not usual and quite different from the one of AF systems. Most countries allow AV systems on croplands only if the crop productivity is maintained (e.g. in France) or slightly reduced, as in Japan and Germany, with 80% and 66% minimum relative yield (RY) required respectively. We suggest to use the Ground Coverage Ratio (GCR: ratio of the area of photovoltaic panels to the area of land) as an indicator of the crop potential productivity in AV systems. The GCR can be easily computed and controlled for all kinds of AV systems with fixed (horizontal, tilted or vertical) or mobile (on 1 or 2 axis trackers) panels. We provide here a synthesis of published data for crop productivity under AV systems. We included only publications that provided both the GCR of the system and the crop RYs, which requires a reliable non AV control plot. Several publications were excluded as a consequence of doubts about the validity of the measurements (too small sized systems with strong edge effects, unreliable control plots). Despite the scattering of results, a clear pattern is evidenced: RYs decrease rapidly with increasing GCRs. It appears that a GCR < 25% is required to ensure that most crop RYs stay > 80%. Our results are consistent with a recent meta-analysis on the impact of shade on crops. Using the GCR criterion to validate AV projects is a simple and costless alternative to the tricky control of crop yields in the fields.