WEG has supplied a battery energy storage system (BESS) with 4MW of power and 8MWh of capacity to Finland’s Callio solar park, one of the country’s first hybrid renewable energy projects combining large-scale solar generation with battery storage.
The project was delivered in April 2026, 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.
Commercial power production at the Callio solar park began in June 2025. The energy storage equipment maximises the capacity of the existing 13MWp 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, WEG BESS provides flexibility to the hybrid plant regarding the timing of energy export to the grid.
The project represents one of the first hybrid systems in Finland that combines photovoltaic generation with energy storage. The equipment supplied by WEG includes two battery containers totalling 8,360kWh of capacity, a 4,400kVA bidirectional power converter, a 4,500kVA 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,” says Manfred Peter Johann, Vice President of Automation & Systems at WEG, “while at the same time strengthening the stability of the national power grid through energy arbitrage and rapid response to frequency variations.”
In the hybrid system, the focus is on optimising 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.
