Primeo Energie’s new large-scale battery storage system in Kappel has successfully completed its first months of operation. The facility in the canton of Solothurn is running reliably and provides balancing energy in particular for Swissgrid, helping to keep the Swiss electricity grid stable.
Primeo Energie’s large-scale battery storage system in Kappel (SO) was connected to the grid in several stages in spring 2026. Four battery strings are currently in operation. A fifth string will be installed at the end of the year, after which the facility will be fully completed. Each string comprises four containers with battery cells. Once fully expanded, the large-scale battery storage system next to the substation in Kappel will have an output of 30 megawatts and a storage capacity of 80 megawatt hours. In purely mathematical terms, this would be enough to supply around 30,000 households with electricity for almost three hours. As things stand today, the storage system is one of the largest of its kind in Switzerland.
The large battery currently provides balancing energy primarily to the national grid operator Swissgrid. This is needed when electricity has to be fed into or drawn from the grid at short notice in order to keep the grid frequency constant at 50 hertz. The system is controlled via Primeo Energie’s “equalio” flexibility pool, which forwards Swissgrid’s signals to the battery storage system. The facility has also been tested on the Swiss intraday market. This trial operation has shown that the system is also ready for use in electricity trading on the market.
Primeo Energie focused on sustainable technical solutions when implementing the project. The transformers use bio-oil based on vegetable oil. Unlike fossil mineral oil, it is biodegradable. The switchgear also does not use sulphur hexafluoride (SF6), an insulating gas that is harmful to the climate. The planned service life of the storage system is 15 to 20 years. After that, its components are to be recycled.
Large-scale battery storage systems are becoming increasingly important for the electricity system. To keep the grid stable, electricity production and consumption must be balanced at all times. With the growing share of solar and wind energy, this task is becoming more demanding because their production fluctuates depending on the weather. Flexible facilities such as battery storage systems can absorb or release electricity at short notice and thereby help to balance these fluctuations.
The large-scale battery storage system in Kappel supports the Swiss Confederation’s Energy Strategy 2050 and strengthens security of supply. The expansion of battery storage systems is an important part of Primeo Energie’s corporate strategy. The company plans to connect further large-scale battery storage systems to the grid in the future. The next storage system is scheduled to go into operation next year in Rankwage (SO).
Media contact: Viktor Sammain, PR Editor, tel. +41 61 415 41 08, e-mail medienstelle@primeo-energie.ch
