Plant operator Atel Hydro, a subsidiary of Alpiq Holding Ltd, investigated ways to increase capacity at Flumenthal back in 1993. Following success with model-based trials, actual modernisation work began in 2006 as part of a general refurbishment programme at the power station.

Atel Hydro rebuilt the first turbine-generator group over a six month period in winter 2006/2007, with refurbishment of the other two groups undertaken in staggered one-year intervals. The last turbine-generator group was returned to service early this year.

Modernization of the power station encompassed a general overhaul of the generating groups. New turbine shafts were fitted, there were technical modifications to the water flow around the turbine wheels, and control and regulating equipment was replaced along with the plant’s switchgear.

Installation of new modified turbine wheels with an enlarged flow cross-section and optimised contours enabled significant improvements to turbine efficiency and water throughput capability. No structural alterations to the building were needed to carry out the work, and discharge conditions in the Aare are unchanged.

As a result of the refurbishment, annual power generation at the plant stands at 146GWh.