Rice Field Agrivoltaics Shows Promise with Tracking Systems

Japanese researchers have made new strides in addressing the challenges of combining rice cultivation with solar power generation. Despite previous productivity concerns, innovative approaches using double-axis tracking systems show potential for making agrivoltaics viable in rice paddies.

Addressing Known Challenges

Rice cultivation under solar panels has historically faced significant productivity hurdles. A six-year study by University of Tokyo researchers demonstrated that rice yields decreased by approximately 23% in agrivoltaic settings compared to control plots (6.5 tons per hectare versus 8.5 tons). The research identified reduced biomass and fewer panicles as key factors limiting productivity, while grain quality issues like increased chalkiness also emerged under partial shading conditions.

New Approach with Dual-Axis Tracking

To overcome these limitations, another University of Tokyo research team explored whether dual-axis tracking systems could improve outcomes. Their study examined an 830 m² rice paddy installation in Nagano Prefecture featuring 352 solar panels (130W each) organized in small groups controlled by torque motors.

The system's key innovation was its ability to adjust panel angles throughout the growing season, prioritizing rice growth during cultivation periods and energy production during off-seasons. The panels' inclination was carefully managed: 11 degrees during April-August, 20 degrees in September-October and February-March, and 30 degrees from November through January.

Promising Results

While initial rice yields under the panels were significantly lower than in nearby control paddies, the researchers observed substantial improvement in the second year after refining sunlight exposure levels. Notably, the harvested rice met Japan's highest quality standards, with protein and amylose content comparable to locally grown rice.

The solar component generated 961.4 kWh/kW, which researchers noted was comparable to European agrivoltaic systems.

Future Directions

The research, published in the Journal of Photonics for Energy, highlights the importance of balancing crop productivity with energy generation. The team suggests that careful management of shading through strategic panel angle adjustments can help achieve both agricultural and energy goals.

Future research may explore artificial intelligence for real-time sunlight optimization and the use of high-efficiency or semi-transparent solar panels to further reduce crop shading impacts.