Besides the conversion of the turbine type from the original Francis runner design from almost 100 years ago to a modern Kaplan design, there was another equally important general requirement to meet: Eglisau’s status as a historical landmark. The preservation obligations of the plant and its architecture had to be considered very carefully. Much of the plant’s technical equipment is still in its original circa 1920 state and will be preserved in its entity.

It did not take long until the Project Management team led by Peter Bührer realized that the gate and door of the old power house would be the bottleneck for the delivery of large components for the rehabilitation project. The door accommodates parts up to 4.5 meters wide, some of the new parts are more than 6.5 meters in diameter – the pit liner for example.

„It was obvious that we had to find another way to get the equipment into the power house“, says Peter Bührer: „Our only chance was to go for the slice by slice-option bringing the components in through the windows. Therefore, we had a truck-mounted crane which lifts the parts from outside upright through the windows.“ On the inside, a new crane complemented the historical one to move the parts to their final position inside the 80 to 90 meter long power house.

Voith delivered seven 6.7 MW Kaplan turbines, generators and governors as well as the complete control package. „The new turbines even exceed the guaranteed efficiency“, explains Peter Bührer.

In its more than 85 years of operation, Eglisau hydropower station produced more than 20 billion kWh of electricity. Using Kaplan turbines instead of the original Francis units even increased the flow rate from 385 m3/s to 500 m3/s. Thus, annual performance could be raised about a third from 246 to 314.5 GWh which is enough electricity to power around 80 000 households.