The almost a century year old Ritom pumped storage plant in Switzerland is to be replaced by a new facility, with technology group Voith receiving an extensive order for generating units at the plant.

Voith announced that it will be responsible for design, fabrication, installation and commissioning of the new high-performance generating units for client Ritom SA, a Joint Venture between Swiss Rail SBB and the canton of Ticino.

The electricity produced by the Ritom pumped storage power plant is of crucial importance for the operation of the rail network by SBB and for supplying power to the Ticino region. The total investment volume for the construction project is in the region of CHF 250 million. The new plant is scheduled to go into operation in mid-2023.

The four Pelton turbines with a total rated output of 44MW that are currently used in the Ritom plant will be replaced by much more powerful generating units in the new facility. To this end, Voith will supply two Pelton 60MW turbines and a 60MW storage pump.

The different designs and purposes of the generating units mean that Voith’s engineers have exacting requirements to meet. For example, the first machine unit will supply power for the 16.7 Hz Swiss Rail network and the operation of its trains. The second will feed the electricity it generates into the 50 Hz public grid.

The third unit, a 60MW capacity storage pump with a delivery head of more than 700m, will pump the water for reservoir management and to provide balancing power (operating reserve) from the Airolo basin to Lake Ritom. In combination with the turbine, the pump can provide the operating reserve for fast grid regulation and stabilization with maximum flexibility. This means that the new power plant will provide a feed-in reserve/intake balance of 60MW for the 50 Hz Swiss grid.

“In addition, the storage pump can be speeded up with the help of the 50 Hz Pelton turbines using back-to-back starting and synchronized with the grid. In this situation the power of the turbine is used to start the pump in the water,” explained Christian Matten, Project Manager at Voith Hydro Europe.

Because of the special importance of this power plant, operator Ritom SA had very stringent design requirements for all components. “As well as conducting transient pressure (water hammer) calculations, we built a comprehensive simulation model for the entire electrical and mechanical scope of supply and carried out corresponding research beforehand,” said Matten. “As a result, we can ensure, for example, that our machines meet the exacting requirements of the Swiss transmission grid.”