The largest alpine solar plant in Switzerland

Pioneer project at a glance

Together with IWB, Axpo has realised Switzerland's largest alpine solar plant at 2500 metres above sea level. The plant has been fully operational since the end of August 2022. The pioneering AlpinSolar project produces 3.3 million kilowatt hours of electricity per year - half of it in winter. In this way, we use solar energy at any time of year and despite the sea of fog. 

Impressions from the construction period

We use the sun where it is the closest

The Muttsee dam is extremely well suited for a photovoltaic plant thanks to its existing infrastructure, its orientation and its altitude:

  • Owing to the alpine location at 2500 m.a.s.l., solar power is particularly effective and generates lots of power in the winter thanks to snow reflection and a lower incidence of fog.
  • The Muttsee dam faces the south and, as a result, has sun all day.
  • The Muttsee dam has an optimal angle – snow slides off the surface on its own.
  • Part of the infrastructure (e.g. 16 kV grid connection) could be used for the installation. 
Local, renewable power for Denner

Denner, Switzerland's largest discounter, purchases the alpine solar power from Axpo under a power purchase agreement (PPA) for the first 20 years after commissioning. Denner is thus consistently pursuing its ambitious sustainability goals and is supplying its retail outlets and offices with 100% renewable and local electricity. 


Need for stable framework conditions for continued solar expansion

In its fall session 2022, the Federal Parliament created the prerequisites for the fast expansion of ground-mounted PV plants with higher winter production in its “Urgent measures for the short-term provision of reliable power supply in winter" (amendment to the Energy Act). The simplified approval process and additional subsidies will be in force until the end of 2025 or until a total annual production of 2 TWh has been reached. With the urgent measures, the Swiss Parliament has generated a welcome short-term impulse for alpine plants.

More viable framework conditions for the expansion of renewable power production will remain important beyond the year 2025. For example, PV ground-mounted plants will require a solution that goes beyond these urgent measures. In the wake of the blanket ordinance, framework conditions for all renewable energies must be improved to create more momentum for the expansion of domestic power capacities, particularly, the simplification and acceleration of approval processes.

By 2050, Switzerland must develop about 50 terawatt-hours. The Axpo model foresees a mix of various production technologies and a fundamental technology impartiality in order to master this enormous challenge.

Alpine solar power in winter

Switzerland produces significantly less electricity in winter than it consumes. So there is a shortage of electricity in winter, which has to be imported. And this fact is likely to increase significantly over the next few years as nuclear and coal-fired power plants are taken off the grid at home and abroad.

It is therefore important to find solutions to produce additional electricity from renewable sources in winter. The large-scale alpine solar plant in the Glarus Alps makes a contribution to this: it produces around three times more electricity in the winter months than a comparable solar plant in the Swiss midlands.

Solar panels in the Swiss midlands are often under a blanket of fog during the winter months - at high altitudes there is much less fog and thus more solar radiation. In addition, solar panels like it cold. The efficiency of solar modules is higher at low temperatures than when it is hot. And finally, the sunlight is reflected by the snow cover, which leads to a higher solar power yield. This is called the "albedo effect". In addition, the angle of inclination of the dam is optimal for solar power production in winter.

Winter power from a dam

Project manager Christian Heierli in an interview on winter power and profitability.

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Data for research

The full operation of AlpinSolar also marks the start of scientific research work by the Snow and Avalanche Institute (SLF) and the EPFL technical university. Over a period of four years, empirical values and data on the system will be collected, which can serve as a basis for future systems in the alpine region. The testing of different panel types, the comparison of different panel inclination angles on the dam and data on wind and snow loads are also part of the research.

Solar researcher Annelen Kahl on the pioneer project in the Glarus Alps

The largest alpine solar plant at the Muttsee dam at 2,500 metres above sea level has also been of interest to the Federal Institute of Technology Lausanne (EPFL) and the Institute for Snow and Avalanche Research (SLF) since the beginning of the project. Annelen Kahl has been researching the behaviour of solar plants in the high alpine region for several years. In this interview she reveals what opportunities she sees in the 2-megawatt pioneer project.

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