On April, 16, 1998, the class 7c visited the Freudenau power plant. Like all power plants on the Danube, the power plant Freudenau is a multi-purpose installation. Apart from producing electrical power, it serves several other purposes. For example, when the water level of the Danube rises, or when the rubble on the river bottom is being washed away and the river threatens to become too deep, the plant can help. Furthermore, the power plant secures the ground water level of the city of Vienna. In addition to that, near the riverside new natural recreation resorts for man and animal develop.

 The Freudenau power plant is the first big river power plant next to a big city with over a million inhabitants. After five years of hard work, it is now almost finished. The plant was built with the so-called wet-building method, i.e. in the river. In two phases - since the beginning of the works in 1992 - the southern lock was built on the right banks of the Danube and the weir installations with the four weir fields on the left banks. Since the middle of 1995, the ships on the Danube have been able to use the southern lock chamber. In an island ditch actual power plant was built, plus the second lock, and the operational buildings on an island. In the beginning of 1997, one of the six planned turbines already started operating. The others started working in spring of 1997. These six Kaplan-pipe turbines, with a running-wheel diameter of 7.5 m, are the biggest of their kind in Europe. Together with the connected generators, they make up the “heart” of the plant.

The six engine sets can process as much as 3000m³/s of water. The power produced is sent through ground cables to the transformers at Kaiserebersdorf. The planned power production is equivalent to the consumption of approximately half of all Vienna households.

The deepening of the river Danube, which in former times was considered desirable as a form of protection against floods and was even caused on purpose, is nowadays perceived as the reason why the Prater water-meadows are slowly drying up. Also the drinking water supply seems to be threatened by the river deepening. The building of the power plant and, in connection with it, the damming of the water, seems to provide a chance for preventing the consequences of the deepening.

The whole plant is made up of three major parts: The power plant itself, the lock and the weir installations. The central power plant is situated in the middle of the river between the weir and the power plant island, on which are situated the filling and emptying installations for the locks, the assembly building with its workshops, the operational buildings and the garages. The six engine sets are made of one Kaplan turbine with a horizontal arbor and a three-phase current generator each. They transform water power into electrical energy.

The weir installations with the four weir fields are situated on the left side in a flat bay of the island in the Danube, and towards the side of the river, they are right next to the power plant. The installations have the following purpose: when the water level is high, not all the water can be taken in by the turbines. So the surplus water is released through the four weir fields. Even at flood level it is still possible to produce power and to let the surplus water run out under the lifted gate.

The sluice helps the ships to overcome the different water levels between the upper part and the lower part. The ship enters the sluice, and by opening the filling / emptying channels, the water level within the sluice is approximated to the upper / lower level.

All in all, the excursion was very interesting and we got valuable insights into the interiors of such a power plant.

(Patek, Benesch)