01.07.2021 | Test you solar energy knowledge

How high is your solar IQ?

Ueli Walther




Axpo is the already largest Swiss producer of renewable energies and with a portfolio of 16,600 MW we are the leading marketer of green electricity in Europe. Axpo intends to strengthen this position because solar energy is the market of the future – including in Switzerland. How familiar are you with the topic of solar energy and the key figures? Test your knowledge and learn more. Go for it!

1. How long does it take for sunlight to reach the earth?

A)    A little over 8 minutes

B)    Exactly 30 minutes

C)    About an hour

A – A little over 8 minutes

Light travels about 300,000 kilometres per second. The sun is an average of 149.7 million kilometres from the earth. Sunlight takes a little over 8 minutes to reach the earth. The speed of light is always the same in outer space. That's why astronomical distances are measured in time units. The most well-known unit according to this principle is the light-year. However, it does not represent a time span, but rather the distance that light travels in a year: about 9 trillion kilometres.

2. Solar energy is booming – because the costs for this energy are dropping. How much have they dropped worldwide on average each year since 2010?

A)    By 5 per cent

B)    By 18 per cent

C)    By 10 per cent

B – It's 18 per cent

Costs have dropped on average by 18 per cent per year. It's no wonder that solar energy is growing so rapidly: With an average annual growth rate of 39 per cent in the last ten years, this area is growing faster on a global scale than any other energy technology  – and doubling its capacity nearly every two years. See more details here.

3. And what about solar growth in Switzerland in 2020?

A)    At least 15 per cent

B)    At least 20 per cent

C)    At least 30 per cent

C – At least 30 per cent

Surprising in light of the corona pandemic: Swissolar, the Swiss Association for Solar Energy, assumes a new record growth rate for photovoltaic systems in the year 2020. As compared to the previous year, this is at least 30% according to the association. However, to reach climate and energy policy goals, Switzerland must increase expansion by a factor of 4 in the upcoming years. This requires adaptations to subsidy programmes, the obligation of self-consumption in new buildings, and simplified spatial planning processes for ground-mounted plants, in particular infrastructure.

4. How much electricity will Alpinsolar generate during the winter?

A)    30 per cent

B)    40 per cent

C)    50 per cent

C – 50 per cent

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 and results in higher solar power production. This is called the Albedo effect. Furthermore, the slope of the dam wall is optimal for solar power production in winter. You will find a comparative graphic on electricity production at high altitudes and solar plants in the Midlands here.

5. When did researchers in the USA start developing the first solar cells?

A)    In the 19th century

B)    After the end of  First World War

C)    In the 1950s

C – In the 1950s

In 1954, the front page of the New York Times announced the development of the first silicon solar cell at Bell Telephone Laboratories in New Jersey. The crystalline silicon solar cells were about 2 cm² in size and had an efficiency rate of up to 6%. The photovoltaic effect was discovered in 1839 by the French physicist Alexandre Edmond Becquerel.

6. How high is the voltage of a solar cell?

A)    0.5 volts

B)    50 volts

C)    230 volts

A – 0.5 volts

A single silicon solar cell has a voltage of 0.5. The voltage increases through the serial connection of solar cells and modules. Twenty years ago the maximum system voltage was limited to 110 V in order to fulfil safety regulations. With today's solar modules,  a system voltage of 1000 V is possible. This improves the performance of the solar plant because there are fewer losses when transporting power at higher voltages.

7. How many full load hours can a Swiss solar plant produce on average per year?

A) 1000 hours

B) 4500 hours

C) 7500 hours

A – 1000 hours

Production of solar energy is irregular and difficult to forecast. It varies depending on the weather. In addition, no electricity can be produced during the night. As a result, only about 1000 full load hours per year can be calculated for PV in Switzerland. As a comparison: A run-of-river power plant produces about 4500 full load hours, a biomass power plant, which Axpo also operates, generates about 7500 hours per year. 

8. An average solar module comprises 36 cells (4x9). What happens when a cell is in the shade? 

A)    Output drops by 10 per cent

B)    Output drops by 25 per cent

C)    Output is only 50 per cent

C – 50 per cent

If you install solar cells on your roof it is important to ensure that the entire system is in full sun. If a cell is in the shade, the performance of the affected module drops by half. This is because of the electric wiring of the solar cells in the module. Several solar cells are wired in so-called strings. That means that they are connected to each other in a row by a cable. If a solar cell in a string is in the shade, the electricity flow reacts similar to water that is held back by a kink in a garden hose. The entire electricity flow is impeded and is only as high as its weakest point, which is the point that is in the shade.

9. How high is the efficiency rate of a solar cell?

A)    20 to 22 per cent

B)    30 to 34 per cent

C)    50 to 52 per cent

A – 20 to 22 per cent

The efficiency of a solar cell indicates how much of the available solar energy is transformed into solar power in the photovoltaic cell. The best mono-crystalline modules can reach an efficiency level between 20 and 22 per cent. Record efficiency was reached at the end of 2013 by a German-French development team and reached a remarkable 46%.

10. How high are CO2 emissions from solar power measured in CO2 equivalents?

A)    30 grammes

B)    42.5 grammes

C)    275 grammes 

B - 42.5 grammes

According to a study on behalf of Swissolar, the production of a kilowatt-hour of solar electricity in Switzerland produces 42.5 grammes of CO2 equivalents. The manufacture and disposal of the PV plant are included in the calculation. As a comparison: A gas-fired power plant produces 589 grammes and for a lignite-fired power plant it's 1220 grammes. According to the European Environment Agency, the power mix in Europe produces emissions of 275 grammes. At Axpo we are a lot lower – our entire electricity production emits only 79 grammes per kilowatt-hour. And our electricity is even cleaner in Switzerland. We generate one third of Swiss power consumption with emissions of only 7 grammes.

Here's how we rate your result

8-10 correct answers

IQ 180+: With your knowledge on the topic of solar energy you even outshine genius Albert Einstein!

4-7 correct answers

IQ 100: With your knowledge on the topic of solar energy you're in a good average range. Want to improve that? Then get up to speed on solar energy and  Alpinsolar here.

1-3 correct answers

IQ: We can't say what your IQ is... but one thing's for sure: You could do better, right? You will find information on solar energy and AlpinSolar here.

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