What is the potential of solar energy in Switzerland?

This potential is enormous. If we decided to cover all of our well-exposed roof and facade surfaces with solar panels, we could meet our entire annual hot-water requirements, a significant proportion of our heating needs, and nearly 40% of our electricity consumption by 2050.

In Switzerland, the total surface area available and well exposed to solar radiation is estimated at 140 km² for roofs and 55 km² for façades. The average solar radiation that falls on these surfaces each year corresponds to about 200 TWh. This is almost the total current energy consumption of Switzerland [→ Q6]. Of course, not all of this radiation can be converted into usable energy (final energy), because the imperfect efficiency of the technologies used must be taken into account. Assuming that 20% of the total surface area is covered by thermal collectors (for hot water production) and the remaining 80% by photovoltaic panels (for electricity production), we could then, simultaneously and considering the efficiencies of the technologies available today:

• meet all our domestic and industrial hot water needs (13 TWh per year);
• produce 9 TWh per year of heat, making it possible to cover 20 to 30% of our heating needs in 2050;
• produce 24 TWh per year of electricity, which is between 35 and 45% of the expected consumption in 2050 depending on the scenario considered.

In practice, given various installation constraints, it will not be possible to cover all the surfaces available with solar collectors. It is therefore realistically estimated that only half of this solar potential could be effectively exploited, or 12 TWh/year, if current technologies are considered.

The performance of thermal solar collectors still has some room for improvement, especially for vacuum collectors. But it is mainly photovoltaic technologies (converting solar radiation into electric current) that have the greatest potential for improving their efficiency. It could increase from the current average of 16% to 25% in 2035, which would increase the photovoltaic potential by more than 50%. We can thus hope to reach 18 TWh of production by this horizon, which represents ¾ of our current nuclear production (24 TWh).

The seasonal variation of solar radiation is an important limiting factor; rooftop solar heat and electricity production is almost 5 times lower in December and January than in June and July (the difference is much smaller for facade panels). Depending on the orientation of the panels, this can result in a strong seasonal disparity between solar energy production, which peaks in the summer, and our energy demand, which peaks in the winter. Our solar energy production could even become surplus in the summer. If we are to harness the full solar potential in Switzerland, we will therefore have to succeed in storing this energy until the following winter, by developing so-called “seasonal storage” solutions. With this in mind, solar energy could be used for the production of synthetic fuels such as hydrogen or methanol [→ Q74].

Solar panels – thermal as well as photovoltaic – have the dual advantage of not taking up any space on the ground and causing very little damage to the landscape, at least when used on buildings. They are therefore well accepted by the population, unlike wind turbines or hydropower structures. However, it is not certain that large solar collector projects (such as exist in Germany and more rarely in Switzerland) enjoy the same favourable consensus. However, there are areas in Switzerland that are of little architectural or landscape value, such as motorways or railway lines, and some sections of which could be covered with photovoltaic panels, thus considerably increasing the amount of land that can be used.

Finally, photovoltaic solar panels have a long service life, more than 30 years. Contrary to some preconceived ideas, they need only one to three years of electricity production to compensate for their “grey energy”, i.e. to generate the energy needed to manufacture them.