The largest alpine solar plant in Switzerland

Pioneer project at a glance

In the summer of 2021, Axpo and IWB will begin construction of the largest alpine solar plant on the Muttsee dam at an altitude of 2,500 m.a.s.l. Denner has contracted all the generated alpine solar power for a term of 20 years. With the 2.2-megawatt pioneer project, Axpo and IWB are driving forward the expansion of renewable energies in Switzerland and supplying important winter power.

Construction of the solar plant on the dam in the Glarus Alps with nearly 5,000 solar modules is scheduled to begin in the summer of 2021. The plant will produce some 3.3 gigawatt-hours of electricity per year – corresponding to the consumption of 740 average four-person households. The solar plant will cover a surface of 10,000 square metres, which corresponds to about 1.5 soccer fields. The dam is part of the Limmern pumped storage plant located in the Glarus Alps and is the highest elevation dam in Europe.

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.
  • Only existing infrastructure will be used so that no additional open space is needed for construction.
  • Some of the infrastructure (e.g. 16-kV grid connection) is already in place.
Local, renewable power for Denner

Denner, the largest discounter in Switzerland, has contracted the alpine solar power generated as of commissioning for a term of 20 years. In doing so, Denner continues to rigorously pursue its ambitious sustainability objectives and will supply its stores and offices with 100% renewable, local power. 


The energy transition requires additional large-scale plants, but...

Achieving the energy transition is contingent upon the construction of many more large-scale, renewable energy producing plants like AlpinSolar in the upcoming years. Unfortunately, there is little perceptible development in this area. This is because the current subsidy framework is designed for small plants with captive use. Today, large-scale plants are an economic risk. This is also likely to be the case for AlpinSolar.

In view of the importance of the project for the energy transition – electricity in winter – Axpo and IWB have decided to move forward despite the risk. The energy suppliers hope to gain experience in the construction of these types of plants, collect data for research, and send a signal to the whole of Switzerland, especially to politics. In addition, with Denner, they have found a power consumer that, under its sustainability strategy, is prepared to pay a price that will cover the high investment costs for the plant.

The Energy Act must improve the subsidy framework

The success of the energy transition cannot be dependent on whether companies that are prepared to accept uneconomical projects can be found. Switzerland must improve the political framework conditions for large-scale plants. The current revisions of the Energy and Electricity Supply Acts is an opportunity to do so. The bill will come before Swiss Parliament this summer. Along with a major part of the industry, Axpo and IWB have contributed to the discussion with proposals on how this could be achieved: For example with a floating market premium based on international standards.

Alpine solar power in winter

In winter, Switzerland produces significantly less power than it consumes. This lacking power in winter has to be imported. The situation will intensify in the upcoming years when nuclear and coal-fired power plants are taken off grid in Switzerland and abroad.

This makes it important to find solutions to produce additional power in the winter from renewable sources. The large-scale, alpine power plant in the Glarus Alps will make a contribution: It will generate 50 per cent of its production during the winter.

Solar plants in the Midlands are often under the fog line during the winter months – there is much less fog and more sun at high altitudes. In addition, PV plants like the cold. The efficiency of solar modules is higher at low temperatures than when it is hot. And sunlight is reflected by the snow cover and results in higher solar power production. This is called the Albedo effect. Furthermore, the angle 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 pioneer project in the Alps offers an opportunity to collect empirical values and data for research that could be useful for future plants in the alpine region. This research could include, for example, testing different types of panels, comparing different panel inclination angles on the dam, or empirical data on wind forces and snow loads.

To minimise plant risks due to snow loads, Axpo has already had a study carried out by the Institute for Snow and Avalanche Research in which every section of the dam was analysed to see how much pressure snow puts on the solar panels. This study is the basis for assessment for the alpine solar plant.

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

The first large-scale, alpine solar plant will be installed on the Muttsee dam at 2,500 m.a.s.l. in the sum-mer of 2021. The pioneer project also interests the Federal Institute of Technology Lausanne (EPFL) and the Institute for Snow and Avalanche Research (SLF). Annelen Kahl has been researching the perfor-mance of solar plants in high alpine regions for several years. In this interview she reveals what opportu-nities she sees in the 2-megawatt pioneer project.

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