11.08.22 Solar panels sold out Author: Christian Buck • Reading time: 7 min.

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Summary

Interest in photovoltaics has rarely been as high as it is today. Small modules for balconies make an ideal entry-level solution, but they are in short supply. And, as a result of in-depth research, even more efficient solar cells should soon be available. 

In midsummer, the sun shines for hours every day, which benefits not only tourists, but also operators of solar farms, because this is the time of year when they can generate a particularly large number of kilowatt hours of green electricity. In Germany, around 60 gigawatts of solar output is currently installed. In 2021 alone, around five gigawatts were added. This is starting to make a significant difference to the electricity mix in the country. Last year, photovoltaic systems were responsible for almost nine percent of the gross electricity generation. On the international stage, the leaders are China and the USA with 260 and 100 gigawatts respectively. Germany comes in behind Japan (75 gigawatts) in fourth place. However, China and the USA have not achieved a comparable percentage of the electricity mix with their solar generation. In both countries, the figure is around four percent, while Japan by contrast has reached approximately eight percent. 

Ambitious expansion plans

Germany intends to increase the pace of expansion even further. In the latest amendment to the German Renewable Energy Act (EEG 2023), the plan is to achieve a photovoltaic generation capacity of 215 gigawatts by 2030. This means that over the next ten years the proportion of solar energy in the German electricity supply should rise to almost 30 percent. The solar expert Volker Quaschning from HTW Berlin University of Applied Sciences is even expecting photovoltaics to cover around one third of our entire energy requirements in the long term, including, for example, consumption for heating and transport. The current figure is around three percent. 

Of course, countries in Southern Europe and the Middle East can generate more solar energy than Germany because of the high number of hours of sunshine there. But even in our latitudes it is possible to produce a reasonable quantity of energy over the course of a year. In Germany, insolation is around 1,000 kilowatt hours (kWh) per square meter per year, but the levels are five times higher in summer than in winter. Countries further south, such as Spain and Turkey, have much higher insolation figures at more than 1,800 kWh per square meter per year. 

However, the experts believe that it is still worthwhile to generate solar energy in Germany. “Past experience has shown that photovoltaic systems are cost-effective here,” says Jörg Sutter, President of the German Society for Solar Energy. “We now have our first very large photovoltaic farms, which can function without any subsidies. Also, if the solar electricity were generated in an African country, for example, we would have to bring it here along thousands of kilometers of electric power lines.” The additional output resulting from the favorable geographic location would be wasted because of the losses in the lines. “This is why it makes perfect sense to build solar farms in Germany and not somewhere much further south,” explains Sutter. 

Huge interest in solar energy

A lot of people in Germany are of the same opinion, particularly since energy security hit the headlines as a result of the war in Ukraine. “There is currently huge interest in solar energy,” comments Sutter. “This is what we are hearing from the installers and the wholesalers, but also from the consumer advice centers.” They are currently seeing large numbers of people who are looking for advice about the move to photovoltaics. “One in every six homeowners in Germany is planning to install solar panels for generating energy or heating over the next twelve months,” reports Carsten Körnig, Managing Director of the German Solar Association. 

The relatively new plug-in solar panels for use on balconies are particularly in demand at the moment. “They have become hugely popular and the demand is now so great that it will not be possible to get hold of any over the next few weeks from any of the online stores or other suppliers,” says Sutter. “The lead times are very long, because the suppliers are overwhelmed with enquiries.” A study by the consumer advice center in the German state of North Rhine-Westphalia reveals that around 190,000 of these systems have already been installed throughout Germany. “And if another few hundred thousand are sold over the next few years, that means more renewable energy is being generated here,” comments Sutter. 

The appeal of the plug-in solar panels is that they are easy to install, for example on a balcony, and can be connected to the grid without any effort. You simply need to plug the modules into a wall socket using a normal plug. However, many grid operators in Germany require special plugs or registration in same way as with a large photovoltaic systems. “You have to fill out a ten-page form before you’re allowed to start using the panel,” complains Sutter. “The red tape is an obstacle that puts a lot of people off and, unfortunately, the problem hasn’t been addressed in the latest amendment to the Renewable Energy Act.” Anyone who does not register their module risks having to pay a fine. But many people are still not doing so and are not suffering any consequences. Sutter believes that connecting the solar panels to the grid with a normal mains plug is perfectly safe. “Your house won’t burn down. The requirement for a special plug is not realistic.” 

Self-sufficiency with your own electrolyzer

If you generate solar energy on your roof or your balcony, you can significantly reduce your electricity bills. But complete independence is not possible, at least not with a photovoltaic system and a battery. “But if you have an electrolyzer and a hydrogen tank as well, you could actually go off-grid and generate all of the energy that a normal house needs all year round,” explains Sutter. “But setting this up is technically very complex, which is why we recommend installing a solar system that covers 70 to 80 percent of your needs. The remaining 20 to 30 percent can then come from the power grid.” But many housing developers are still interested in the hydrogen solution. “It’s difficult in technical terms and not necessarily financially viable,” says Sutter. 

By contrast, the latest developments in solar cells do promise to be more cost-effective, because researchers all over the world are working on making them more efficient. If you install solar panels on your roof today, you can expect an efficiency level of around 20 percent. Conventional silicon solar cells have a theoretical efficiency limit of approximately 29 percent, while commercially available modules should eventually reach 26 percent. Better yields can only be achieved with the help of new concepts. 

More solar electricity from tandem systems

This is where perovskites come in. This is a class of materials that could give solar cells a genuine efficiency boost. If they are applied in a thin layer to a silicon solar cell, they can significantly increase its output, because the perovskites can be tailored to exploit the parts of the sunlight spectrum where silicon is not particularly efficient (green and blue). Tandem modules made of silicon and perovskites could achieve efficiency levels of well over 30 percent. But the new material can also be used as a replacement for silicon. The first solar cells made entirely from perovskites have already achieved an efficiency of more than 25 percent in the laboratory. This could be increased even further by stacking several layers of the material on top of one another, each of which optimized for different areas of the sunlight spectrum. Thin transparent coatings on windows or walls are also a possibility, which would mean that previously unused surfaces could produce electricity in the future. 

“Almost all of the major manufacturers are investigating perovskites, because they are currently the only way of improving silicon solar cells,” reports Professor Michael Saliba from the University of Stuttgart, who is carrying out detailed research in this field. “The first tandem modules will hopefully come onto the market in the middle of this decade and by 2030 at the latest. The results of many research projects and a number of articles in the press by manufacturers indicate that perovskites have passed almost all the usual stability tests, which would mean that they can be used in the field. There is already a research facility in Crete where a perovskite solar cell system is being tested outdoors.” 

The innovative tandem modules could possibly also breathe new life into the German solar industry, most of which migrated to China around ten years ago. “The multi-junction solar cells are high-tech products,” Saliba explains. “We have world-leading research facilities in this field in Germany with a great deal of expertise and a large number of patents. This could lead to the renaissance of the German solar industry.” There is already one production line in operation in Neubrandenburg which is run by the British start-up Oxford PV. And Saliba himself is in the process of founding a start-up called Perosol to manufacture perovskite-based solar modules. 

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