Series Solar Sharing Frontline No.7 Tsuboguchi AgricultureSolar Panels Protect Rice from Extreme Heat

The seventh edition of our "Solar Sharing Frontline" series features Tsuboguchi Agriculture in Toyooka City, Hyogo Prefecture, where rice is cultivated beneath solar panels. The solar sharing system has a shading rate of 30%, reducing exposure to intense sunlight. During the extreme heat of 2023, many chalky rice grains were found in areas without solar panels, while fewer occurred under the panels, helping to prevent deterioration in rice quality. To balance quality and yield, the shading rate was determined based on examples from solar sharing projects across Japan, and the project achieved yields of more than 80% of the regional average, the benchmark for temporary farmland conversion permits. Tsuboguchi Agriculture has also cultivated sweet potatoes, Japanese yams, black soybeans, and other crops under solar panels, expanding the range of crops suited to shaded conditions.

Of the five solar sharing facilities in the city, four were financed through corporate bonds issued by Tsuboguchi Agriculture and purchased by Patagonia Japan. The electricity generated is supplied to Patagonia's directly operated stores in Japan through a retail electricity provider. Tsuboguchi Agriculture is also working to commercialize sake made from rice grown using solar sharing. A portion of the annual JPY 6–7 million in electricity sales revenue is used to invest in agricultural facilities, including a rice drying and processing facility. The company also aims to continue farming while maintaining habitats for birds and aquatic organisms. In collaboration with the University of Hyogo, it is studying how shading from the solar panels affects water temperatures and organisms in the rice paddies.