A solar cell is about the size of the palm of your hand and consists of two layers that are two to three tenths of a millimetre thick. Today, most solar cells are made of silicon. Their basic material, quartz sand, is available in sufficient quantities on earth - and silicon is considered environmentally friendly.

There are two types of solar cells: Crystalline and amorphous. Crystalline cells account for the largest share of global production. Monocrystalline solar cells are manufactured from pure silicon, which is withdrawn from a silicon melt in a time-consuming and costly process, pressed into bars, and then cut into discs up to 12 centimetres in diameter. All atoms are aligned equally in the monocrystal. The blue to black cells, which also come in different colours if desired, harvest up to 24 per cent of the solar rays in the Iaboratory; in practice, efficiency is 16 to 20 per cent.

Multi-crystalline solar cells consist of industrially produced polysilicon, and their production is significantly less expensive than monocrystalline solar cells. They are bluish in colour and their efficiency in practice is between 11 and 14 per cent.

Amorphous solar cells are less expensive and suitable for simple applications such as a garden fountain or on large house facades. In amorphous solar cells, the electricity generating layer is steamed onto a glass plate. The atoms are no Ionger deposited in a crystal structure, but in a disorderly (amorphous) manner instead. Relatively little silicon is needed for this process, which lowers the price. ln comparison with the 0.2 to 0.3-millimetre thick crystalline cells, these so-called thin-layer cells measure only 0.01 to 0.05 millimetres. The cells are brown or anthracite and have an efficiency of 6 to 10 per cent. On gloomy days, amorphous cells deliver more electricity than others - but their efficiency drops over the years.

When the sun shines, solar panels produce electricity. Logical, isn’t it? But even on less clear days, solar cells can produce electricity, although not at full capacity. This is comparable to our skin, which reacts to solar UV rays even when it is cloudy. Around 75 percent of the electricity generated by conventional solar systems installed in the lowlands is generated from May to September. What’s more: Solar plants do not produce electricity during the night. ln contrast to base load energy from hydropower or nuclear power, photovoltaic power is therefore only moderately predictable and controllable.

By the way: The share of photovoltaics in the Swiss electricity mix in 2018 was 1944 GWh, which corresponds to around 2.9 per cent.By the way: the share of photovoltaics in Swiss electricity production in 2018 was 1944 GWh, which corresponds to around 2.9 percent.

A typical solar panel (one square metre in size) made of commercially available silicon can generate an average of 180 W on a clear, sunny day in Switzerland. That's enough to run a Iaptop computer. A solar system consisting of several panels with a size of 20 square metres produces around 3600 kWh of electricity per year. In comparison: An average Swiss household consumes between 4500-5000 kWh of electricity per year.

As a general rule, the output of solar modules essentially depends on the amount of sunlight (global radiation/geographical location), on orientation (the more precisely the photovoltaic system is positioned at the optimum inclination angle to the south, the higher the yield) or on shade (from trees, chimneys, etc.). But of course the quality of the solar cells also has a significant influence on the overall performance.

A solar park is a large number of solar modules that are installed on fields or other large surfaces and feed the generated electricity into the grid. Sometimes they are referred to as solar farms or open space solar plants. ln a solar park, the solar modules are installed on approximately 3-metre high mounting systems, which are placed into the ground like fence posts. Rows of these mounting systems would be a typical feature of a solar park. Solar parks can be of any size. About 1.6 to 2 hectares of land are required for every megawatt (MW) of installed solar modules (around 4000 modules per MW).

Studies show that up to 67 TWh of electricity could be generated on rooftops and facades in Switzerland. This corresponds to around 110 per cent of annual electricity consumption in Switzerland. If other infrastructures (car parks, reservoirs, noise barriers) and other open spaces, such as those in already developed Alpine regions, were to be covered with solar panels, there would be an additional potential of 25 per cent. The sun could therefore become a major factor in Switzerland's energy supply. However, politicians would have to create incentives for this, i.e. design the market and the framework conditions in such a way that companies are prepared to make the necessary investments - also for large-scale plants. In addition, a strong expansion of photovoltaics requires large storage facilities, which do not yet exist, as well as grid expansion and grid reinforcement, especially at the lowest Ievel.

How much does electricity produced from photovoltaics cost? Thanks to increasingly cheaper solar modules, the production costs for solar energy are continue to drop. They are between 8 and 28 centimes/kWh depending on the size of the system. For comparison, the production costs for nuclear power plants are between 4 and 7 centimes per kWh – for large-scale hydropower they range between 4 and 9 centimes per kWh.

ln addition, the costs per kWh of electricity produced also depend to a large extent on the location, i.e. the local sunshine duration/radiation. In a normal year, the sunshine duration in Lugano is around 2100 hours, while in Glarus it is only around 1200 hours. Accordingly, more or less solar energy can be produced, which naturally has an impact on costs.