Maintaining high crop productivity in rice fields hosting solar panels remains a major challenge for agrivoltaic projects, as demonstrated by a recent research project conducted by the University of Tokyo in Japan. The six-year experiment showed that grain yields reached 8.5 tons per hectare in the control plot, compared with 6.5 tons per hectare in the agrivoltaic field, representing a 23% reduction.
The results confirmed that rice yields in the agrivoltaic system were limited by reduced biomass and fewer panicles, both of which are critical to rice productivity. Grain quality also deteriorated under partial shading, particularly in terms of grain chalkiness and head rice yield.
With these challenges in mind, another research group from the University of Tokyo has proposed a multi-modeling approach that could help accurately predict rice yields in agrivoltaic systems.
“Our study is the first to build a multi-modeling framework that couples three models – solar radiation environment, rice growth and yield, and photovoltaic power generation. It predicts rice yield and electricity output simultaneously in rice agrivoltaic systems,” corresponding author Yoichiro Kato told pv magazine. “It integrated radiation, rice growth, and photovoltaic models to jointly predict rice yield and electricity generation under agrivoltaic panels, enabling probabilistic, climate-based design of panel configurations that meet yield targets while quantifying the impact on power output and revenue.”
The researchers used Rhinoceros, Grasshopper and Ladybug Tools to simulate solar radiation reaching rice crops beneath the panels. They used the ORYZA crop model to estimate rice yields under agrivoltaic and conventional cultivation conditions, while PVsyst simulated electricity generation. The models were calibrated and validated using field data collected between 2019 and 2022 at an experimental site in Chikusei, Japan.
The agrivoltaic installation covered 1,416 m2, with a ground coverage ratio of 27% and monthly adjustments to panel tilt angles. The researchers then used 30 years of meteorological data, from 1994 to 2023, to assess long-term crop yields and electricity production.
The research group simulated additional panel tilt angles ranging from 10 degrees to 70 degrees to determine how increased sunlight availability could affect rice growth. A key objective was to identify configurations capable of achieving at least 80% of conventional rice yields, in line with Japanese regulations.
The team also calculated the probability of meeting this threshold under different weather conditions. The researchers then assessed the economic implications of optimizing panel tilt angles, considering both rice sales and electricity revenue.
The researchers found that their computer simulations closely matched the results measured during field experiments. The models accurately reproduced sunlight levels, rice growth and electricity generation, suggesting that they could reliably predict the performance of agrivoltaic systems under different conditions.
Simulations based on 30 years of weather data, from 1994 to 2023, showed that rice yields under agrivoltaics averaged 82% of conventional cultivation levels, ranging from 66% to 94%. The probability of falling below Japan’s regulatory threshold of 80% was 26%. Average electricity generation between May and September reached 32,893 kWh, with a coefficient of variation of 7.1%.
The researchers also found that increasing panel tilt angles toward the vertical improved sunlight availability and rice yields, although it reduced electricity production. Increasing the tilt angle by 7 degrees raised the probability of achieving at least 80% of conventional rice yields to 80%, while reducing annual income by just 0.1%.
Adjustments of 30 degrees and 53 degrees increased this probability to 90% and 95%, respectively. These configurations improved rice yields by 4.2% and 10.3%, but reduced electricity generation by 3.2% and 9.4%, respectively. Consequently, annual income declined by 2.7% and 8%, respectively.
“The approach can be extended to other design variables, such as panel size and installation density, as well as to assessments of site suitability based on region, climate and cultivar characteristics,” Kato said.
The researchers presented their findings in “Balancing crop production and electricity generation in rice agrivoltaic systems: A multi-modeling approach,” published in Field Crops Research.
“These findings confirmed that the multi-modeling approach, which integrates irradiance, crop, and photovoltaic models, can assess grain yield and electricity generation in rice agrivoltaics, thereby reducing potential risks when exploring different agrivoltaics configurations within the food–energy nexus,” the researchers concluded.
In 2025, another research group from the University of Tokyo investigated whether agrivoltaic systems based on dual-axis trackers could improve rice productivity. The experiments showed that, over two growing seasons, rice yields under the panels were 75% and 85% lower than those in nearby benchmark paddies without solar modules. However, the researchers found that yields, while slightly lower in the first year, improved significantly in the second year after they fine-tuned the amount of sunlight reaching the crops.
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