According to a study by the Fraunhofer Institute for Solar Energy Systems ISE (PDF) in Freiburg, renewable energy sources are becoming increasingly important in power generation in Germany. In 2018, 43 percent of all electricity in Germany was covered by renewable sources. The largest share of this is borne by wind energy, which covers around 17 percent of the total electricity requirement. The second place of renewable energies is currently biomass power generation.
If the ongoing development since 2008 continues unchanged this year, photovoltaic systems will exceed the share of biomass in electricity generated from renewable energy in 2019. Due to their steadily increasing distribution, photovoltaic systems were able to increase their share from less than two percent in 2008 to 8.7 percent in 2018.
Solar power is becoming increasingly important in Germany. The share of total electricity generation has increased by about 7 percent within ten years. This is mainly due to the lower acquisition costs and the higher efficiency of the systems, which are available for single-family houses from around 10,000 euros.
980,000 solar systems in Germany:
A survey by the Bundesverband Solarwirtschaft eV (BSW) shows that the demand for photovoltaic systems in the home sector alone increased by about a quarter within a year. In 2017, around 55,000 smaller solar power systems were installed on private houses with a maximum nominal output of 10 kilowatts (kWp). In the previous year, there were around 10,000 fewer systems.
Estimates assume that the rising electricity prices and the resulting higher profitability of our own power supply as well as the technical development of solar systems will lead to a further increase in the number of newly installed systems in the coming years. A total of around 980,000 solar systems in this performance class are active in Germany. Another development is that many small photovoltaic systems now have their own batteries, which can hold the generated electricity in order to enable a completely self-sufficient supply.
Commercial and industrial sectors are also growing rapidly:
In addition to private households, commercial and industrial companies are increasingly focusing on covering at least part of their electricity needs from environmentally compatible sources. The annual growth rates of new plants are double-digit here too. Carsten Körnig, the managing director of the BSW, sees the main reason for this as “the profitability of solar power”, which motivates the companies to make large investments.
Some of the large commercial photovoltaic roofs are also installed by third-party companies, which pay the owners of the houses an annual rent. In addition to the two companies, which on the one hand generate additional income by renting the roof and on the other hand generate profits by generating electricity, the environment can also benefit from the fact that the ever increasing proportion of solar power increasingly ensures that coal , natural gas or nuclear energy are becoming less important in electricity generation.
In fact, any roof can be used for photovoltaics if it is not shaded. If it is partially shaded, this must be taken into account when planning the system. If photovoltaic systems were primarily installed on south-facing roofs in the past, all roofs are now used – and also other areas.
Are north roofs suitable for photovoltaics?
Rather not. However, for visual reasons, the north roof is occasionally used for photovoltaics. Because some owners find it better if all roofs facing south, east, west and north look the same. Most of the time, photovoltaics are only installed on roofs that are not oriented towards the north.
Do I absolutely need a south roof for photovoltaics?
No, but south-facing roofs are preferred for photovoltaics . Because at noon the sun is in the south, has the most power and provides the most electricity. Because the sun can also be very powerful in the morning and afternoon, roofs with different orientations can also be used. However, the optimal orientation for photovoltaics is south.
Can roofs to the east or west or east-west roofs be used for photovoltaics?
Yes, absolutely, and in both directions. Because in the morning and in the afternoon, these roofs with photovoltaics also supply a lot of electricity. They can even be interconnected so that the yields from both roofs are optimally used. East-west roofs generate a relatively constant current curve during the day – unlike south roofs, which have a typical midday peak. Evenly generated solar energy over the day fits better with the photovoltaic storage , which should be filled as possible in the evening.
How are the solar modules mounted on the roof?
Usually solar modules are mounted on the roof covering. In the case of pitched roofs, the installer screws special roof hooks into the battens of the substructure in order to hang the modules over the tiles and screw them onto aluminum rails.
The solar modules are usually set up on flat roofs freely with ballasted systems. Only rarely, for example in regions with strong winds, are the frames anchored by bolts in the roof membrane. This carries the risk of later leaks and must therefore be carried out very carefully.
Ballasted systems hold due to their own weight. The weight of the ballast stones must be absorbed by beams located under the roof. The ballasting plan is based on the wind conditions, the size of the solar modules and the substructure of the roof.
What is the optimal slope of the roof for photovoltaics?
Pitched roofs, between 25 and 60 degrees, are best suited for photovoltaics. The solar modules can be mounted on them parallel to the roof, you don’t have to set them up. The steeper the roof, the better the rain washes away any dirt from the modules. And the sooner the snow slips in winter. The optimal inclination for photovoltaics is 35 degrees (when facing south).
How much space do I need for photovoltaics?
A good solar module with sixty cells (standard size) has an area of about 1.6 square meters and produces around 300 watts (some with over 100 cells even around 400 watts). Accordingly, 1 to 1.2 kilowatts need around 6 to 6.4 square meters of roof area. Between 850 and 1,300 kilowatt hours of solar power can be harvested per square meter – depending on the region and orientation of the roofs. If the plant produces less electricity, it was either planned incorrectly or has a defect that reduces yields . The more space used for photovoltaics, the better.