How can large-scale solar power be stored? Batteries will play an increasingly import- ant role in saving it for a few hours or days. Stationary batteries at home or in the grid or batteries in the car will enable us to op- erate the grid stably. In Switzerland, we can also rely on hydropower for seasonal storage and pumped storage power plants for short-term storage. Another option is to heat underground or water tanks in summer and use this heat in the winter. This works for large buildings, but also for small ones with the help of a re- versible ground source heat pump. Finally, hydrogen production from clean energy will play an increasingly important role. In addition to the conventional modules, solar roof tiles are also being developed. What other commercial applications do you anticipate? All buildings must be energy efficient or – even better – become an energy source themselves. For facades, there are now white panels or terracotta-like panels for the roof. Thanks to “transformative” PV devices, in which the solar cells are cov- ered by a coloring film, as is already the case, there are in principle no limits to what can be achieved. There are wonder- ful new possibilities, even solar cells as a work of art! Where else can the modules be integrated? On mobile devices like cars, trucks, drones, planes, watches... there are many more applications to come. ◄ Innovation We have excellent scientific and technological research centers in Europe, and we must take advantage of that. But we have to hurry.” Christophe Ballif, Director of CSEM can be easily synthesized from readily available materials, so there is no supply risk involved. How much can the light yield be increased? By combining materials such as gallium arsenide (GaAs), three, four, five or even six solar cells can be stacked on top of each other to achieve efficiencies of over 38 percent. However, these materials and their deposition techniques are very ex- pensive, typically by a factor of a thou- sand compared to a silicon cell. Today, they are mainly used in outer space or for military applications, such as drones. Will it be possible to generate solar power in space? Yes, the idea to install huge solar stations in space, convert the electricity into mi- crowaves, and beam the power back to Earth around the clock is out there. But we still have countless technical chal- lenges ahead of us to make this happen. Back to Earth. In many regions of Central Europe, solar energy can cover the energy demand in summer, but not in winter. What should we do? Even though we have more sunshine in summer, you can still generate a lot of solar energy in winter. There is nothing wrong with installing more solar panels to have more energy in winter, as well as re- ducing production in summer or using them to manufacture chemicals. We have enough space for solar energy, which is 30 to 100 times more efficient than biomass, for example. We can also use unusual sur- faces, such as in parking lots, on harvesting machines, over roads and in fields or lakes. At the European level, wind and solar power complement each other perfectly, so there is a good balance throughout the year. So this is what the new perovskite cell looks like. Prof. Ballif promises that it has remarkable potential for further increasing efficiency. 36 MEYER BURGER Magazine 01/2022