Researchers in Japan have made another attempt to make agrivoltaisies on rice fields technically and economically feasible, despite known productivity problems when rice is grown under solar modules. They used double axle, finding potential with careful management of shadow and tilt corners.
Maintaining high crop productivity in rice fields that organize solar panels remains a great concern for agrivoltaic projects, as demonstrated by a recent research project from the University of Tokyo in Japan. This six -year experiment showed that the grain yield in the control plot was 8.5 T per hectare, while it was 6.5 T per hectare in the Agrivoltaics field, which represented a reduction of 23%.
The results of this work confirmed that the grain yield in the Agrivoltaics system would be limited by the reduced biomass and the reduced panel number, which are critical properties for rice productivity. Grain quality, and in particular the grain limeiness and the proceeds of the main rice, also appeared to be deteriorated under partial shadow in the Agrivoltaics system.
With these issues in mind, another research group from the University of Tokyo investigated whether Agrivoltaic systems can achieve better results in terms of rice productivity based on dual-axis trackers.
They analyzed the performance of an Agrivoltaic facility with trackers on an 830 m2 rice pathdy in Miyada-Mura, Nagano Prefecture, Japan. “The system is designed to adjust panel corners daily and seasonal, to prioritize rice growth during the planting season and to maximize energy production during the low season,” they explained.
The system used 352 PV panels with a power of 130 W and a size of . They were grouped in units of 7 to 8 panels and twisted by six torque engines. Galvanized materials were used to withstand strong winds of maximum . “The PV panels are checked and rotated remotely with the help of torque engines around the most important East-Westas,” the research group emphasized. “The slope of PV panels along the North-South axis is regularly adjusted at an angle of between 10 and 30 degrees of the horizontal.”
Image: Y. Okada et al., Doi 10.1117/1.JPE.15.032704
During the April-August period, the modules were placed at 11 degrees of the horizontal, while they were placed at 20 degrees in September and October. From November to the end of January they were placed at 30 degrees and from February to the end of March at 20 degrees.
These experiments showed that the rice yields were 75% and 85% lower for two growing seasons under the panels compared to benchmark -paddies without modules in the area. However, the scientists discovered that, although slightly lower in the first year, the yield significantly improved in the second year after refining the amount of sunlight that reached the crops.
“It is important that the rice also met the highest standards of the highest grain quality in Japan,” they explained further. “The average protein content was 6.34% compared to 6.47% for rice produced in the local village area, while that of Amylose was 18.71% compared to 18.67%.”
The PV system turned out to be able to generate 961.4 kWh/kW, a value that the researchers described as comparable to Agrivoltaic systems in Europe.
Their findings are available in the newspaper “Case Study of rice agriculture in Japan under Agriphotovoltaic systemPublished in the Journal of Photonics for Energy.
“The study underlines the considerations involved in balancing the productivity of crops with solar energy output,” concluded the research team. The researchers noted that careful shadow management, including adjusting the panels of the panels during the day and the season, can help achieve both goals. They also emphasized future instructions such as the use of AI to optimize the sharing of sunlight in real time and to experiment with high efficient or semi-transparent solar panels to further reduce the shadow of crops.
This content is protected by copyright and may not be reused. If you want to work with us and reuse part of our content, please contact: editors@pv-magazine.com.
Popular content
