80%+ overall cycle efficiency

Variable speed technology to regulate power

Variable Speed Pumped Storage Technology

Securing future electricity supply

In 2008, Kraftwerk Linth-Limmern (KLL) AG—a partnership between Axpo Power AG and the Glarus cantonal authority—began seeking a way to extend its hydroelectric power production, located in the heart of Switzerland in Linthal. At the time, KLL generated 450 MW. In order to better satisfy peaking power demand and aid in meeting Switzerland’s low-carbon power generation goals, KLL wanted to increase the plant’s total output.

Switzerland was dedicated to the development of pumped storage power plants as an efficient, flexible and timely solution to fluctuating power demands and managing peaks in a financially and environmentally efficient manner.

Power at the Flip of a Switch

KLL granted GE a contract in 2008 to provide four new 250 MW variable speed pump turbines, four 280 MVA variable speed motor generators, and power electronics for the new project. These units were designed to boost the plant’s output from 450 MW to 1,450 MW, generating as much electricity as a nuclear power plant.

The altitude differences found in the Swiss Alps provide a particularly favorable environment to use pumped storage power plants. In order to generate electricity, the operator opens the main inlet valves and lets the water run down from Lake Mutt, located nearly 2,500 m above sea level, to Lake Limmern in the valley below. The water runs through the pump turbines that turn the motor generators, converting the potential energy in the fallen water into electricity. However, if power demand drops, the plant is able to reverse the flow of water, pumping it from Lake Limmern back up to Lake Mutt, which is 630 m higher.

Pumped storage plants also play a key role in regulating the frequency of the electrical grid. The variable speed pump storage plants will enable Switzerland to regulate power to the grid in both generating and pumping mode.

Peak Power Efficiency

The Linthal 2015 project was designed to provide central and northeastern
Switzerland with electricity supply for years to come. Linthal 2015 became GE’s first variable speed technology plant to connect to the grid. With a total power generating capacity of 1,000 MW, its output is equal to the average power consumption of approximately 600,000 people.

GE’s variable speed technology enables KLL to fine-tune the plant, monitor the level of excess electricity in the grid and send the right amount in whatever direction it is needed, all with an overall cycle efficiency of more than 80%. In addition, the storage capability means that energy can be reserved to immediately and effectively bridge production bottlenecks.