Switzerland's first large-scale alpine solar power plant

Pioneer project at a glance

Axpo is planning the first large-scale alpine solar power plant at the Muttsee dam at 2,500 metres above sea level. The dam is part of the Limmern pumped storage power plant in the Glarus Alps and the highest dam in Europe. With this 2-megawatt pioneer project, Axpo is pushing ahead with the expansion of re-newable energies in Switzerland and supplying important winter electricity.

The project envisages a plant with an installed capacity of 2 megawatts and an annual electricity produc-tion of 2.7 gigawatt hours, equivalent to the annual consumption of 600 average four-person households. Around 6,000 PV modules covering an area of 10,000 square metres are planned for this purpose, to be installed on the south side of the Muttsee dam.

The most important facts about the pioneering project:

  • The Muttsee dam is extremely well suited for a photovoltaic plant thanks to its existing infrastructure, its location and its altitude.
  • The plant will deliver about half of its power production during the winter – a comparable plant in Central Switzerland generates only one quarter of its total production volume during the winter.
  • Axpo has requested the SFOE to include the pioneer facility at the Muttsee in the list of lighthouse projects.

Winter power from a dam

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

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Alpine solar power in winter

Switzerland produces significantly less electricity in winter than it consumes. Therefore, there is a lack of electricity in winter. And this fact is likely to intensify significantly in the coming years when large-scale power plants are taken off the grid in Switzerland and abroad.

It is important to find solutions to the problem of winter electricity. The large-scale alpine solar power plant in the Glarus Alps makes a contribution here: it supplies 50 percent of its production in winter.

During the winter months, the PV systems in Central Switzerland often lie under a blanket of fog - at high altitudes there is much less fog and thus more solar radiation. In addition, PV systems like to be cold. The efficiency of solar modules is higher at low temperatures. And finally, the sunlight is reflected by the snow cover, which leads to a higher solar power yield. In addition, the angle of inclination of the dam is ideal for solar power production in winter.

The Muttsee dam is interesting for alpine PV for various reasons:

  • Due to its alpine location (almost 2500 m.a.s.l.), photovoltaics is particularly effective there and, thanks to reflection on the snow and little fog, delivers a lot of electricity, especially in winter.
  • The dam has a southern exposure with optimal sunlight
  • The dam has an optimal angle of inclination – snow slips off by itself
  • Existing infrastructure is built on, so no additional open space is occupied
  • Part of the infrastructure (e.g. 16 kV grid connection) already exists

Data for research

The first large-scale alpine solar plant offers the opportunity to gather experience and data in the field of research, which could be useful for future plants in the alpine region. For this purpose, the testing of different panel types, the comparison of different panel inclination angles on the dam wall or empirical values with wind and snow loads could be part of the research.

In order to minimize the risk to the plant from snow loads, Axpo has already had the Institute for Snow and Avalanche Research (SLF) carry out an initial study which measures how much pressure the snow will exert on the solar panels for each section of the dam. Among other things, it forms the basis for the design of the solar system. 

“We need a new solution for winter power”

Solar researcher Annelen Kahl about the Axpo project in the Glarus Alps

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