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02.09.2022 | Test your energy knowledge

Solar power from the mountains – how does that work?

Ueli Walther




In Switzerland, the majority of power consumption will have to be covered by additional renewable sources. The expansion of photovoltaics (PV) plays an important role here. The largest alpine solar plant in Switzerland has been in operation since the end of August 2022. Have you heard about it already? What do you know about solar electricity and AlpinSolar? Test your knowledge in our quiz.

1. According to the Federal government, how high must the proportion of solar power in total power consumption be in 2050?

A) around 30 per cent

B) around 40 per cent

C) around 60 per cent

B – around 40 per cent

According to the Energy Perspectives 2050+, the Swiss Federal Office of Energy expects an installed capacity of around 34 terrawatt hours of solar electricity in Switzerland in its forecasts for the year 2050. Today, the current proportion of solar electricity is only 2 terrawatt hours. The expansion of solar plants is therefore to be increased by a factor of 17. This means that solar power will cover around 40 percent of total consumption. 

With its Power Switcher, Axpo calculates that 38.17 terawatt hours of solar electricity are needed to cover the calculated electricity consumption of 86.3 terawatt hours. 

2. What is the most commonly used material in solar cells?

A)    Chrome

B)    Nickel

C)    Silicon

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.

3. At the end of August 2022, the largest alpine solar plant in Switzerland went into full operation. Where exactly?

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

B)    Near the Limmernsee dam at 1857 m.a.s.l.

C)    On the Oberblegisee above Braunwald at 1422 m.a.s.l.

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 cubic metres of concrete were used for the gravity dam and the reservoir can store up to 23 million cubic metres 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."

Axpo-CEO Christoph Brand

4. Axpo looked for a strong project partner. Who is it?

A)    EKZ

B)    EWZ

C)    IWB 


The energy service experts 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.

5.     Who will purchase the power at a fixed price for 20 years? 

A)    Coop

B)    Denner

C)    Lidl

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."

Denner-CEO Mario Irmiger

6. What do experts call this type of long-term power contract at a fixed price?

A)    Power Purchase Agreement

B)    Fix Power Deal

C)    Long-time Power Agreement

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.   

7. How much power does the AlpinSolar facility produce?

A)    2.2 megawatts

B)    2.2 gigawatt-hours

C)    3.3 gigawatt-hours

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 produces an average of 3.3 gigawatt-hours of electricity annually with a capacity of 2.2 megawatt. This power covers the annual average consumption of 740 average four-person households. 

8. 4872 solar panels were installed on the Muttsee dam wall. How large is the area of the solar plant?

A)    1500 square metres

B)    10 000 square metres

C)    20 000 square metres 

B – 10 000 square metres

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.
  • It was possible to build on existing infrastructure where there was also a grid connection. 

9. What's special about an alpine solar plant compared to a plant in the lowlands?

A)    It produces more power in summer

B)    It produces more power in winter

C)    It is easier to maintain

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 supplies three times more electricity in the winter months than a comparable plant in the lowlands.

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.

10. What can you do with a kilowatt-hour of solar power?

A)    Cook 240 eggs

B)    Watch TV for 30 hours

C)    Work on the computer for 10 hours

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.

How we rate your result

8-10 correct answers

Very bright: Your knowledge on AlpinSolar outshines the sun. Congratulations!

4-7 correct answers

Not bad: Your knowledge is like the sun – unfortunately it doesn’t shine 24 hours a day. Want to change that? Then get up to date on solar energy and AlpinSolar here.

1-3 correct answers

Let there be light: You didn't exactly shine on the topic of AlpinSolar. You could do better, right? Get up to date on solar energy and AlpinSolar here.

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