Crop-specific Optimization of Bifacial PV Arrays for Agrivoltaic Food-Energy Production: The Light-Productivity-Factor Approach

Abstract

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.