Challenge: upgrading a power station inside a mountain


A Nord SK 12407 industrial geared motor drives the lower conveyor belt

In an extremely demanding construction project in the Swiss Alps, at an altitude of around 1700 metres and almost 600m inside a mountain, large chambers are being excavated to form the new expanded underground centre of a pumped storage hydroelectric power station.

The expansion project ‘Linthal 2015’ will upgrade three existing power station systems and increase their overall output power from 480mW to 1480mW. The supplier of this complete drive solution is Getriebebau Nord AG, Switzerland.

A new underground pumping station will drive water from a lower reservoir at an altitude of 1860m into a lake reservoir which is about 600 m higher. The pumped storage power station will use this elevation difference to produce hydroelectric power on demand. The client for this project is Kraftwerke Linth-Limmern AG, a part of Axpo Holding AG.

The power requirements of a national electricity grid are subject to large fluctuations over the course of a single day. At night, power consumption is at a minimum and typically reaches a peak at midday and in the evening. In Switzerland, electric power is mainly supplied by nuclear and river-based hydroelectric power stations.

Biomass and conventional thermal power stations also make a contribution. In contrast to nuclear and river-based plant, pumped storage hydroelectric power stations can rapidly respond to changes in demand. The optimum interplay between these various types of power generation technologies ensures that a reliable and economic power supply A Nord SK 12407 industrial geared motor drives the lower conveyor beltis maintained around the clock.

Unlike pure storage power stations, pumped storage stations cannot just generate energy at peak times; they can also convert excess power, which is generated during periods of low demand, into valuable peak-time energy. The demand for peak energy is continuously increasing throughout the entire European grid network. Apart from the general increase in annual consumption, another important reason for this is the intensive development of wind energy in the coastal regions of the European Union. This factor results in an increase in the so called stochastic energy, which depends on random wind conditions and therefore cannot be reliably planned. If power from wind energy is generated in times of low demand, the excess can be used to pump back water into the higher reservoirs of pumped storage power stations.

Industrial gear units are used in the conveyor systems which are located in the central area of the construction project Linthal 2015. Two S-conveyors convey 500 tons of material per hour over a distance of about 260 metres with an extreme incline of 45 degrees and a height difference of around 180m. The excavated material is conveyed down to a crushing plant. This conveyor belt is driven by a Nord industrial gear unit with brake control, which simultaneously generates electricity. On the second conveyor belt, the crushed material is conveyed up to the gravel plant, where it is stored until it is needed for further processing as construction aggregate for the dams or as concrete for walls and ceilings.

This conveyor has a belt speed of 2.2m/s and is driven by two Nord industrial gear units, located at the right and left of the conveyor system and connected by a common shaft. With a protection class of IP55, these industrial gear units each have a drive power of 250kW.

Supplied by Getriebebau Nord AG