14.05.2020 | Test your energy knowledge (3)

How do you produce electricity from the sun?

According to the Energy Strategy 2050, around 40 percent of total electricity consumption in Switzerland is to be additionally covered by renewable sources. The expansion of photovoltaics (PV) plays an important role in this - for Axpo too. What do you know about electricity from the sun? Test your knowledge in our quiz.

1 How high is the share of solar energy in Swiss electricity production?

A) Just under 10%. 

B) Just over 15

C) Just over 3

C – Just over 3 percent

The amount of solar energy produced in 2018, around 1,942 GWh, corresponds to 3.38 % of the electrical energy consumed in relation to the final energy consumption of 57,600 GWh. The Energy Strategy 2050 plans to increase this proportion to 20 percent.

2. In which year was the first solar cell produced?

A) 1839

B) 1954

C) 1972

B – 1954

This year, scientists from Bell Laboratories in the USA developed the first silicon solar cell and presented it to the public. The solar cell had an efficiency of 6 percent. Modern solar cells achieve an efficiency of 15 to 20 percent in practice. By the way: In 1839 the French physicist Alexandre Edmond Becquerel discovered the photoelectric effect and thus the basis of photovoltaics. More about this here.

3. How many full-load hours electricity per year can a solar plant in Switzerland produce on average?

A) 1000 hours

B) 4500 hours

C) 7500 hours

A – 1000 hours

The production of solar energy is irregular and hardly predictable - it varies depending on the weather. At night it does not produce electricity. For this reason, PV in Switzerland can only be expected to produce around 1000 full-load hours per year. By comparison, a river hydroelectric power plant generates around 4500 full-load hours, while biomass power plants, which Axpo also operates, generate 7500 hours per year.

And by the way: full-load hours are a measure of the degree of utilization of a technical system. Full-load hours are the time for which a plant would have to be operated at nominal capacity in order to carry out the same electrical work as the plant actually did within a specified period of time, during which breaks in operation or partial load operation can also occur.

4. Who currently produces the most electricity from photovoltaics worldwide?

A) Germany


C) China

C – China 

China is by far the leader here. At the end of 2018, solar panels with a capacity of around 175 GW were installed there. In the USA it was still around 63 GW - in Germany, the leader in Europe, it was around 47 GW. 

It is striking that the annual growth rates of the total PV capacity installed worldwide have been very high in recent years and have consistently been in the double-digit percentage range. For a long time Germany was in first place in terms of installed capacity, but was taken over by China in 2015. Since then, the markets there, in Japan and also in the USA have been developing much more dynamically.

5. What can you do with one kilowatt hour of solar power?

A) Boil 240 eggs

B) 30 hours of television

C) Work 10 hours on the computer

A – Cook 240 eggs

We admit, that was a tricky question. Did you guess right? It's the eggs. On a average TV, 1 kWh is enough for 15 hours of wathcing, with the computer it's 7 hours. But with one kilowatt hour of electricity you can also do 5 kilograms of laundry at 60 degrees, vacuum for 93 minutes, withdraw 86x money from a cash machine or take the subway for 21 minutes.

6. Which element is important for the production of solar cells?

A) Chromium

B) Silicium

C) Nickel

B – Silicium

Solar panels are made of semiconductors that produce electricity under the influence of light. Silicium is very often used as a semiconductor.

7. On hot days with a lot of sunshine, solar power plants produce the most electricity...

A) That is correct

B) This is wrong

C) The temperature does not play a role here - so always the same depending on the sunlight

B – wrong

On a hot day, the efficiency of solar panels drops by about 0.4 percent for every additional degree Celsius. This is due to the reduced voltage in the solar cells. A lot of sunshine and cooler temperatures are ideal for electricity production - correspondingly good performance is therefore achieved with solar systems in the Swiss mountains. They produce around 50 % more electricity than a system in the lowlands, especially in winter, the time of year when Switzerland imports electricity. More about this here.

8. Which electricity source causes the least CO2 emissions over its entire life cycle?

A) Nuclear power

B) Wind power

C) Solar energy

B – Wind power

Wind energy causes the least CO2 (13g CO2-eq/kWh), followed by nuclear power (15g CO2-eq/kWh) and solar energy (80g CO2-eq/kWh). Compared to fossil fuels such as coal (870g CO2-eq/kWh), however, the CO2 balance of solar energy is also very good. 

9.  If the production of the Gösgen nuclear power plant is to be replaced by PV systems, an area about the size of the...

A) Lake Thun

B) Lake Constance

C) Lake Zurich

C –  Lake Zurich


Photovoltaics is material-intensive: to replace the electricity production of the Gösgen nuclear power plant in terms of quantity, an area of solar panels would be required that is as large as that of Lake Zurich. It must also be borne in mind that photovoltaic systems do not supply energy in bad weather or darkness, whereas a nuclear power plant can produce evenly throughout the year. These studies show how high the solar potential is in Switzerland

10. What is the average annual solar radiation in the Swiss midlands (Mittelland) per year?

A) Around 1050 kWh/m2

B) Around 1250 kWh/m2

C) Around 1650 kWh/m2

B – Around 1250 kWh/m2

In the Swiss midlands, the annual solar radiation is around 1250 kWh/m2. Taking into account the module and system efficiency, a favourable positioning of the solar modules results in an electricity yield of around 170 kWh per m2 module surface (1250 kWh x module efficiency 0.16 x system efficiency 0.85). Here you can easily find out whether a solar system pays off at home.

How we rate your result

8-10 correct answers

Bright boy: Your knowledge of solar energy outshines even the sun. Congratulations!

4-7 correct answers

Quite good: Your knowledge is like the sun - unfortunately she doesn't shine 24 hours a day either. You want to change that. Then find out here about solar energy and Alpinsolar.

1-3 correct answers

Let there be light: You knowledge of solar energy is far from brilliant. You can do better, can’t you? Here is some information about solar energy and alpinsolar.

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