Osaka Gas and Sonnedix to add 30-MW/125-MWh battery in Oita

• Osaka Gas and Sonnedix will install a 30-MW/125-MWh battery at a 39-MW solar park in Japan’s Oita prefecture to shift energy and support the grid.

Osaka Gas has partnered with Sonnedix to deploy a 30-MW/125-MWh battery energy storage system (BESS) at a 39-MW solar plant in Oita prefecture, advancing Japan’s shift from stand-alone renewables to hybrid assets that can deliver power when it’s most valuable. The four-plus-hour system will absorb midday solar and discharge across the evening peak, while providing sub-second frequency and voltage support to the local network.

Technically, the BESS is expected to use containerized lithium-ion blocks with sectionalized fire-safety zones, off-gas detection and robust thermal management suited to Kyushu’s heat and humidity. Grid-forming inverters will supply synthetic inertia, frequency-watt response and ride-through aligned with evolving utility requirements. A supervisory energy management system will co-optimize energy arbitrage with ancillary services, maintaining state of charge for high-value windows and coordinating closely with the PV plant’s controller.

Adding storage to an operating solar site brings immediate benefits. It raises capture rates by shifting energy into higher-priced hours, reduces curtailment risk on bright, low-load days and turns variable generation into controllable capacity. The co-location also avoids a second interconnection, sharing substation infrastructure and trimming conversion losses compared with a stand-alone battery.

For Osaka Gas, the project supports a broader strategy to pair retail and distributed-energy businesses with grid-scale flexibility. For Sonnedix, it deepens a pipeline of storage retrofits across its fleet—replicable designs, standardized O&M, and portfolio-level analytics that lift returns and availability.

Community measures remain central: construction traffic management, acoustic treatments, landscaped buffers and emergency response coordination with local fire services. End-of-life plans outline responsible recycling pathways for battery modules and balance-of-system components, meeting lender and municipal expectations.

Japan’s evening ramps are intensifying as solar penetration rises, particularly on weekends and mild-weather days. By anchoring four hours of storage at an existing 39-MW site, Osaka Gas and Sonnedix demonstrate a practical template for hybridization—one that strengthens local reliability and extracts more value from every installed megawatt of PV.