WEG supplied a battery energy storage system (BESS) with 4 MW of power and 8 MWh of capacity to the Callio solar park, located in the city of Pyhäjärvi, Finland. The project was delivered in April to Solarigo Systems Oy, the investor and operator of the hybrid park located in Pyhäsalmi mine, a site that is being decommissioned and prepared to host new businesses focused on research, development, and sustainable energy solutions. Energy storage systems are essential for providing stability to the country’s power grid.

Commercial power production at the Callio solar park began in June 2025. The energy storage equipment maximizes the capacity of the existing 13 MWp peak-power solar plant in its role of participating in electricity grid markets. By enabling the storage of the energy generated by the photovoltaic plant, the BESS provides flexibility to the hybrid plant regarding the timing of energy export to the grid, that is, it contributes to the stability of the country’s power grid.

The project represents one of the first hybrid systems in Finland that combines photovoltaic generation with energy storage. Among the equipment supplied by WEG and that make up the BESS are two battery containers totaling 8,360 kWh of capacity, a 4,400 kVA bidirectional power converter, a 4,500 kVA medium-voltage/low-voltage oil transformer, and a central control system for the BESS set and the existing solar plant.

“With WEG’s energy storage system integrated into the Callio initiative, we are helping to transform a historic mine into an innovation hub for renewable generation and storage, while at the same time strengthening the stability of the national power grid through energy arbitrage and rapid response to frequency variations,” says Manfred Peter Johann, Vice President of Automation & Systems.

In the hybrid system, the focus is on optimizing the performance of the entire system. The goal is to use generation, storage, and market opportunities in the most efficient and economically sound way possible.