  Agrivoltaics (AV) is an emerging technology having symbiotic benefits for
food-energy-water needs of the growing world population and an inherent
resilience against climate vulnerabilities. An agrivoltaic system must optimize
sunlight-sharing between the solar panels and crops to maximize the food-energy
yields, subject to appropriate constraints. Given the emerging diversity of
monofacial and bifacial farms, the lack of a standardized crop-specific metric
(to evaluate the efficacy of the irradiance sharing) has made it difficult to
optimize and assess the performance of agrivoltaic systems. Here we introduce a
new metric, light productivity factor (LPF), that evaluates the effectiveness
of irradiance sharing for a given crop type and PV array design. The metric
allows us to identify optimal design parameters including the spatial PV array
density, panel orientation, and single axis tracking schemes specific to the
PAR needs of the crop. By definition, LPF equals 1 for PV-only or crop-only
systems. The AV systems enhances LPF between 1 and 2 depending on the shade
sensitivity of the crop, PV array configuration, and the season. While
traditional fixed-tilt systems increase LPF significantly above 1, we find LPF
is maximized at 2 for shade-tolerant crops with a solar farm based on single
axis sun tracking scheme. Among the fixed tilt systems, East-West faced
bifacial vertical solar farms is particularly promising because it produces
smallest variability in the seasonal yield for shade sensitive crops, while
providing LPF comparable to the standard North-South faced solar farms.
Additional benefits include reduced soiling and ease of movement of large-scale
combine-harvester and other farming equipment.
