The increased number of heat pumps and electric vehicles will drive up electricity demand in the future. Solar power is the ideal way to satisfy our appetite for electricity and curb CO₂ emissions. By building a photovoltaic system, property owners benefit from cost-effectiveness, image enhancement and an increase in the value of their properties.
In 1982, the first solar power system in a private home was connected to the grid in Switzerland. A lot has changed since then: after continual gentle growth over the years, photovoltaics are now experiencing ever-increasing expansion. According to statistics on solar energy published by the Swiss Federal Office of Energy (SFOE), around 118,000 photovoltaic systems with an output of almost 3 gigawatts were installed at the end of 2020. As a result, solar power production already covered 4.7 per cent of Switzerland’s electricity requirements. Experts believe that this trend will continue as a result of efforts to achieve greater energy independence.
According to the Energy Strategy 2050 (in German) and Energy Perspectives 2050+ (in German), renewable energies will assume a larger proportion of energy supply in future. Photovoltaics play a key role here, as Christof Bucher, Professor of Photovoltaic Systems at Bern University of Applied Sciences and author of the book ‘Photovoltaikanlagen – Planung, Installation, Betrieb’, confirms: ‘Solar power currently has by far the greatest expansion potential of all renewable energies and is the only domestic energy source able to cover all of Switzerland’s energy requirements across the year.’ According to Bucher, solar power will replace electricity from nuclear power plants and ensure the electrification of mobility and heat supply. His expert opinion is that solar power may even exceed the production of hydroelectric power to become the largest source of power production in Switzerland.
In photovoltaics, radiant energy is converted directly into electrical energy by means of solar cells. An inverter converts the generated direct current into alternating current. Different types of solar cells are now available on the market. Crystalline silicon cells are by far the most commonly used. There are two different types of these: the polycrystalline cells that were previously used more frequently and the monocrystalline cells that are now most common. The monocrystalline solar cells have been continuously optimised in recent years, so that their efficiency has constantly improved. In addition to crystalline silicon cells, there are also thin-film cells. The advantages of thin-film cells are low material consumption and low production costs, but the efficiency is generally lower than that of crystalline cells. Solar cells are also being developed with new materials. These include, for example, organic cells, dye cells and perovskites. Perovskite solar cells are interesting in that their efficiency could be increased very quickly to over 25 per cent. However, they are not very resistant to moisture and oxygen.
The individual solar cells are connected in series and connected to form modules. Glass-foil modules and glass-glass modules are the most commonly sold products. Solar roof tiles, in a terracotta colour or slate effect, are popular for aesthetic reasons. As PV modules increasingly adorn facades, the demand for more design options has grown. This is why coloured PV modules are now available that meet high aesthetic demands. However, while conventional solar modules typically achieve an efficiency of between 19 and 22 per cent, the efficiency of coloured modules is generally lower. Another speciality are hybrid modules that use solar energy to generate both electricity and heat. However, the heat yield of these modules is far lower than that of conventional solar thermal installations. Hybrid modules also do not reach high temperatures, making them suitable for only a few applications, such as the summer regeneration of geothermal probes.
PV modules can be installed in various places in and around a building:
On-roof systems are a good solution for existing pitched roofs. The panels are mounted on a substructure and the existing roof remains the same. Flat-roof systems offer great potential for solar power due to the large number of unused flat roofs. They are mounted on the existing roof membrane without penetrating the roof.
In-roof systems are systems integrated into the roof and are therefore part of the building shell. They are more demanding in terms of planning and construction, as they also take on the protective function of the roof. They are often used in new-builds or renovations with high aesthetic standards. Although an in-roof system also needs an underlying roof, the costs of conventional roof cladding do not need to be covered.
For facade systems, the PV system takes over the functions of the facade. This usually requires project-specific solutions. PV modules can also be attached to balcony railings. Carports and bicycle shelters offer additional potential for solar power production. Whether and how well a roof is suited to generating solar power is easy to find out with the solar potential calculator (in German).
There are a few key points to consider when planning a PV installation. Before a system can be installed on an existing building, the condition of the roof as well as its structural stability must be assessed. Static reinforcement may be required. A roof renovation should not be planned for the next 20 years. It should also be borne in mind that shading by trees or other buildings can lead to major yield losses. Sufficient space for the inverter, the house connection and the lines must also be considered for installation.
A building permit is no longer required in construction and agricultural zones; it is only required for systems on historic buildings. According to the federal act on spatial planning, a notification to the building authorities is adequate for ‘sufficiently adapted’ solar panels.
Around 90 per cent of new buildings already have a heat pump, and new registrations of electric vehicles are continuing to rise sharply. However, heat pumps and electric vehicles are only really low in CO₂ if they use renewable electricity. It therefore makes sense to combine them with a photovoltaic installation: solar power reduces CO₂ emissions and high self-consumption increases the cost-effectiveness of the PV installation, because the production costs for solar power are usually lower than the electricity tariff for households.
Production-dependent consumption control optimally balances production and consumption and ensures efficient operation. According to Bucher, it also helps to make the heat storage system a little larger, allows for an intelligent charging station for electromobility and raises awareness of solar power amongst residents.
A good way to consume a large proportion of the solar power oneself is to organise several end consumers in one connection to self-consumption (ZEV). This makes sense if, for example, several parties want to use their own electricity. Find out more in our connection to self-consumption white paper.
For owners of property portfolios, photovoltaic systems offer a whole range of benefits. ‘On the one hand, they can hedge against high electricity prices in the future,’ explains Bucher. Secondly, they have the security of now already meeting future regulations, such as the obligation to produce their own electricity. PV electricity from your own roof is usually cheaper than electricity from the grid. The fact that electricity consumption from heat pumps and electromobility will increase even further in the future also contributes to the financial attractiveness of PV systems.
And, last but not least, portfolio owners secure a clear reputation boost by producing their own solar power. Improving life cycle assessments is also becoming increasingly important, as sustainability aspects form part of more and more company strategies. Moreover, PV systems are also attractive because they increase the value of a property.
Christof Bucher: ‘Photovoltaikanlagen – Planung, Installation, Betrieb,’ Faktor Verlag 2021, ISBN 978-3-905711-62-2