Agricultural friendly single-axis dynamic agrivoltaics: Simulations, experiments and a large-scale application for Chinese solar greenhouses

The concept of agrivoltaics (APV) has made progress in recent years but has not yet been widely promoted and applied on a larger scale. The main hindrance lies in the fact that the effects on crop cultivation have not been optimal. This study establishes two sets of single-axis dynamic tracking photovoltaic (PV) systems utilizing bifacial modules: Solar tracking (ST) employing the maximum power generation strategy, and Reverse tracking (RT) employing the minimum shadow area tracking strategy for ground-mounted tracking. In Xiongan (N39.02°, E116.11°), ST increases power generation by 3.9% compared to fixed-axis PV systems (Tilt = 25°), while RT decreases power generation by 34.7%. The discrepancy in power generation between ST and RT is most noticeable on clear sky and partly cloudy days, with minimal difference on cloudy days. We investigate the impact of these systems on crop growth by analyzing changes in canopy area during the lettuce growing period and compare the net photosynthetic rates (P_n) of spring wheat (C₃ crop) and millet (C₄ crop) using canopy photosynthesis and transpiration measurement systems (CAPTS). The results indicate that lettuce shows a larger leaf area under ST throughout the growing period, millet exhibits a higher net photosynthetic rate under RT, while there is marginal difference in the P_n of spring wheat under both systems. This study integrates the above research configuration with Chinese Solar Greenhouses (CSGs) located in Yufa, Beijing. During the production season, the dynamic PV systems switch to the shadow-free mode to ensure the photosynthesis of crops within the CSGs. Conversely, during the idle season of the CSGs, the system shifts to ST mode to ensure PV power generation. By integrating power generation and planting data, the Land Equivalent Ratio (LER) can reach 1.46, with the Return on Investment (ROI) of 20% based on construction costs. Through experiments and practical case studies, it is evident that dynamic PV systems can be effectively integrated with CSGs, providing sufficient land and space for both PV power generation and crop cultivation.