Solar power from the mountains – how does that work?

B – 40 per cent

According to the Energy Strategy, the Federal Office of Energy forecasts an installed capacity of 37.5 gigawatts for solar power in Switzerland in the year 2050 (scenario zero basis). That would correspond to an increase by a factor of 13 as compared to today. Approximately 34 terawatt-hours of solar power will cover 40 per cent of total annual consumption. A solar power share of 32 per cent is estimated for the winter half-year. 

C – Silicon

A solar cell is about the size of a one's palm and comprises two layers that are two to three tenths of a millimetre thick. Today, most solar cells are manufactured from silicon. Their raw material, quartz sand, is available in sufficient quantities on earth – and silicon is considered to be environmentally compatible. Read how and when solar cells found their way into light here

A – On the Muttsee dam at 2500 m.a.s.l.

The pioneer project is located on the Muttsee dam at an altitude of 2500 m.a.s.l. Spanning 1054 metres, it is the longest dam in Switzerland and the highest elevation dam in Europe. 250 000 m³ of concrete were used for the gravity dam and the reservoir can store up to 23 million m³ of water. The dam is part of the Limmern pumped storage plant (LPSP), which functions like a battery in the mountains.

Axpo CEO Christoph Brand comments on the solar pioneer project: "We are proud to realise the largest alpine solar plant together with strong partners, and, in doing so, advance the energy turnaround in Switzerland."

C – IWB

The energy service providers Axpo and IWB have joined forces to transform the Muttsee dam into the largest alpine solar plant in Switzerland. "The company consistently strives for a climate-friendly energy supply. This includes the expansion of electricity production from solar energy with targeted investments in Switzerland," says Claus Schmidt, CEO of IWB.

B – Denner

The third Axpo partner is Denner, the largest discounter in Switzerland. This commitment makes sense for Denner's CEO Mario Irmiger: "This project is a further milestone in our sustainability strategy and reaffirms our commitment to climate goals. Our aim is to continue to exclusively draw our electricity from renewable sources, in order to support the responsible use of natural resources."

A – Power Purchase Agreement

PPAs are not yet well known in Switzerland, but are developing rapidly around the world. They replace the anonymous procurement of electricity from unknown sources. PPAs are of special importance because they accelerate the transition to a renewable energy supply. They create transparency and help consumers establish a direction connection to "their" power source.

PPAs can be concluded for solar plants as well as hydropower plants. The more power that gets directly to consumers through PPAs, the smaller the proportion of non-renewable power consumption.   

C – 3.3 gigawatt-hours

When talking about electricity we have to differentiate between capacity measured in kilowatts and production, which is measured in kilowatt-hours. The plant at the Muttsee will produce an average of 3.3 gigawatt-hours of electricity annually with a capacity of 2.2 MW. This power covers the annual average consumption of 740 average four-person households. 

C – 10 000 m²

The surface of the solar plant at the Muttsee corresponds to the size of about one and a half soccer fields. 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, is exposed to sun all day long.
• 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.

B – It produces more power in winter than a plant in the lowlands.

During the 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 the Swiss nuclear plants are taken off grid. It is therefore important to find solutions for the production of additional power from renewable sources during the winter. 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.

Because: Solar plants in the lowlands 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 wall is optimal for solar power production in winter. More details here .

A – Cook 240 eggs

We admit that this question was a bit tricky. Did you guess right? It's the eggs. One kWh of electricity can power a common television for 15 hours and a computer for 7 hours. You can also do a 5-kilogram load of laundry at 60 degrees centigrade with one kilowatt-hour of electricity, or vacuum for 93 minutes, withdraw money from the ATM 86 times, or ride the subway for 21 minutes.