Valuable peak-load energy

The power stations belonging to Linth-Limmern AG (KLL) in Glarus were built between 1957 and 1968. They use the water inflow from a catchment of around 140 km2 in the headwaters of the River Linth. Its mean electricity production is 460m kWh per annum. However, the KLLs are of much greater significance for power supply across Switzerland. As a storage power station, they produce value peak-load energy when demand is particularly great. Consequently, they play an important part in maintaining the equilibrium between energy consumption and energy production. With the demand for peak-load energy rising steadily, the KLLs are to be upgraded with an additional high-capacity pumped storage plant, Project Linthal 2015.

KLL is a partnership between the Glarus cantonal authority and Axpo AG. Canton Glarus holds a 15% stake, and Axpo AG has an 85% share.

Project Linthal 2015

One of the more significant upgrade projects is "Linthal 2015". A new underground pumped storage facility will be used to pump water from Lake Limmern back up to Lake Mutt which is 630 m higher. Where necessary, it can then be used for generating more electricity. The new facility will boast pump and turbine capacities of 1000 MW each.

This will boost the KLL's output from the current 450 MW or so to 1450 MW. In terms of performance, this will put it on a par with the Leibstadt nuclear power plant or the Cleuson Dixence hydro power station. It will also serve to safeguard the electricity supply for northeast and central Switzerland in the future. Construction is expected to take a good five years, and it should go into operation in 2015/2016. Up to 250 people will be employed on the construction sites. This project will represent an investment of the order of some 1.8 billion francs. The project required new concessions to be issued for the KLL ahead of schedule.

Structural alterations

The new Limmern power station will be installed underground in a cave. A new gravity dam will have to be built for Lake Mutt, and the existing Tierfehd compensating basin will have to be extended. A new connection will have to be made to the supergrid for feeding electricity in and drawing it off. Two underground cable cars have been built to facilitate operation.

Lake Mutt
The storage capacity of Lake Mutt has been increased from 9 to 25m m3. The current natural lake level of 2446 m will be raised to a dam height of 2474 m. In addition, field studies have been conducted in order to survey ecological diversity. They will be used as a basis for the environmental compatibility study which has been conducted.

Kraftwerk Limmern
A new underground machine aggregate center will be created about 600 m inside the mountain at the foot of the dam for Lake Limmern, at approx. 1700 m above sea level. Two pressure tunnels will connect Lake Mutt to the machinery center, and the center will be connected to lake Limmern by two underwater tunnels measuring about 500 m in length. Access to the underground machinery center from Tierfehd is via a 4 km long access tunnel, equipped for this purpose with a cable car.

Tierfehd compensating basin
The existing Tierfehd compensating basin is too small for the new pumped storage facilities. An additional basin will be built to the north of the operating building, with a comparable surface area to the existing basin. This measure will enable the machines in the pump storage works to be used more flexibly, improving the regulation of the flow to and from the Linth.

Connection to the grid
The massive increase in power associated with Project Linthal 2015 will require the KLL to be connected to the Swiss supergrid. There is currently a 220 kV overhead cable line running from Tierfehd to Grynau near Uznach. A new 380 kV overhead line is planned to run from Tierfehd to the Schwanden/Sool area as part of Project Linthal 2015, running parallel to the existing line. It will be connected to the existing 380 kV line from the Vorab Glacier.

For further information, please refer to the flyer entitled Project Linthal 2015, Grid Connection.