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Flumenthal river power station now generating additional electricity sufficient to power 1750 households

Four years of work to increase the efficiency of Flumenthal power station on the river Aare near Solothurn have come to a successful close. The modernised plant operated by Swiss energy supply company Alpiq has added six percent extra generating capacity. The additional electricity generated from renewable hydropower is enough to supply around 1750 households and comes as the product of some 30 million Swiss francs worth of investment.

Refurbishment of three horizontal-axis turbine-generator groups at the Flumenthal power station is complete after four years of work. The result is a six percent efficiency increase, corresponding to additional generating capacity of eight million kWh per year. That amount is equivalent to the electricity needed to power around 1750 households consuming an average of 4500 kWh each per year. Some 30 million Swiss francs were invested in the efficiency-improving measures.


Modernisation work underway from 2006 to 2009

Atel Hydro AG, a subsidiary of Alpiq Holding Ltd., investigated ways to increase capacity at Flumenthal power station back in 1993. Following success with model-based trials, actual work began in 2006 as part of a general refurbishment programme at the power station, which by that time had logged in excess of 270,000 operating hours. Atel Hydro AG rebuilt the first turbine-generator group over a six-month period in winter 2006/2007; refurbishment of the two other groups went ahead at staggered one-year intervals. The last turbine-generator group was returned to service early in 2009. Modernisation 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, control and regulating equipment was replaced, along with switchgear used to run the generators and supply the power station’s own electricity requirements.

Larger turbine wheels for increased efficiency

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. The end result is a power station efficiency increase of around six percent. No structural alterations to the building were needed in order to carry out the work. Discharge conditions in the Aare and elevations of the up- and downstream water levels are likewise unchanged. The modernisation work brings the power station in line with the current engineering state-of-the-art, while optimising energy-exploitation of the head of water as urged by the Swiss Federal Council’s policy on energy.

Flumenthal power station – dependably generating electricity since 1970

The run-of-river power station at Flumenthal is 100 percent owned by Alpiq through its Atel Hydro AG subsidiary. It was constructed as part of a second corrective phase of the Jurassic waterways, has been in operation since 1970 and provides generating capacity of 23.7 MW. Annual power generation stands at 146 GWh after modernisation, which means that the Flumenthal power station supplies around 37,000 households with electricity. Of its concessionary stretch of the river Aare, 62.1 percent is apportioned to the Canton of Solothurn and 37.9 percent to the Canton of Bern. According to agreed terms, BKW Energie AG takes a stake in the investment and annual running costs commensurate with the Bernese share.