HPP Gratkorn, hydraulic design for a compact power plant limited by given geometrical boundary conditions and the dimension of the tailwater gate.

The new construction of a hydropower plant on the river Mur required a planning inversion in the classical sense in order to realise the necessary cost savings for the new development of a low-pressure plant. The downstream sluice gate and the given geometrical boundary conditions limit the overall size of the hydropower plant. In the case of the power plant HPP Gratkorn, the specified outlet and inlet widths are specified together with the setting. The prescribed maximum discharge capacity must be able to pass through the machine without cavitation. Standard hydraulics no longer fit here and a completely new hydraulic design had to be developed and model tested. The two machines with a runner diameter of D = 4.0 m have a combined power output of P = 11 MW with an annual generation of about 54 GWh and are scheduled to go into operation in 2024.