A photovoltaic system at the Muttsee

Could the Muttsee dam located at 2500 metres above sea level be used as the surface for a large-scale photovoltaic system? A few days ago, the Südostschweiz newspaper devoted an extensive article on to the subject. At Axpo, the idea has been under consideration for some time. And first assessments indicate: Yes, this could by all means be possible.

The performance of a photovoltaic system is strongly dependant on its location. Geographic position has a huge impact – North Africa being more advantageous than, for example, Island. The position of the individual modules is also important. In Switzerland, these should be pointing south between 25 and 35 degrees in order to absorb sunlight optimally.

Weather also has a huge influence: When it’s cloudy or foggy, solar plant performance is nearly zero. For this reason, and because of the higher solar radiation, the efficiency of systems located in alpine regions in Switzerland is up to 50% higher than those located in the midlands.

Above a sea of fog

The Muttsee dam is located at 2500 metres above sea level. With a length of over 1000 metres, it closes off the valley in a wide arc toward the southwest. In the winter, the view up here is often on a sea of thick fog covering the Swiss midlands. There are no peaks standing in the way of the sun. Every solar ray from sunrise to sunset shines on the dam, the perfect conditions for a photovoltaic system – in summer as well as winter.

Model for the energy future

The Federal Council’s Energy Strategy 2050 focuses on a strong expansion of renewable energies. With more sun and wind energy, demand for storage energy to compensate production gaps will increase as will the need for pumped storage to compensate production peaks and to ensure grid stability by absorbing surplus energy. With its highly flexible turbines, the Limmern pumped storage plant is a trump card in this interplay of different technologies.

Exciting option if economically feasible

Of course it’s clear that for Axpo the project can only take on concrete form if solar power were to fall under feed-in remuneration at cost. The investment for such a plant would amount to several million francs. Profitable operation would not be possible under today’s market prices. 

But before solar panels are installed, the dam will continue to undergo various control measurements for some time and the last milestones for the full commissioning of the Limmern pumped storage plant must be achieved. The photomontage here would become reality at the earliest in three years. How the power market and politics will develop until then will have an impact on the project and its realisation.