Hybrid pumped hydro-BESS project in Finland doubles battery capacity

Thanks to technological advances, developer SENS has been able to increase the capacity of the BESS component of its innovative hybrid pumped hydro-BESS project, located at Pyhäsalmi mine in Finland. The cluster comprises a 75 MW underground pumped storage hydroelectric (UPHS) facility and a BESS.

Initially, the BESS’ capacity was to be 85 MW but this has doubled to 170 MW, the company announced in Feb. 2025. It attributed this capacity increase to improved BESS technology.

SENS initially entered into a principal agreement with Finnish company Callio Pyhäjärvi to provide the technical solutions to develop an energy storage solution at the mine in May 2024. Subsequently another company, Dovre Group, joined the consortium in June 2024.

In October 2024, SENS announced that it had acquired 100% of the two storage systems at Pyhäsalmi.

“By doubling the capacity of our battery storage project in Pyhäsalmi, we have successfully strengthened the project, which is an important development for both SENS and our partners,” said SENS chief executive officer, Henrik Boman, of the most recent milestone for the project.

“The increased capacity strengthens the project’s business potential and makes it an even more attractive investment case for external actors. This is a clear example of how we are working to optimize our solutions to meet the growing demand for efficient energy storage systems,” Boman added.

SENS maintains that the increased scope represents a “significant increase” in the potential revenue stream and it strengthens the project’s position in the frequency and arbitrage markets. The company has already secured ready-to-build status for the BESS component and will continue speaking with potential investors interested in acquiring it.